1. PINUS
Introduction
Distribution
Distribution in India
Morphology
Key to the Identification of Indian Species
Anatomy
Root
Root-Stem Transition
Shoot Apex
Stem
Leaf
Embryology
Male Cones
Female Cones
Pollination
Receptive Spot
Fertilization
Embryogeny
Seed Coat
Wing
Germination
Cytology
Seed Testing
Seed Production and Dormancy
Breeding
Diseases
Mycorrhiza
Pests
2. PINE OLEORESIN EXTRACTION METHODS
Introduction
Cup the Larger-Diameter Trees for Increased Yields and Greater Profits
Double-Facing
Gum Yield from Shoulders
Use Currect Tin Lengths
First-Year Installation of Spiral Gutters with Double-Headed Nails
Shaving the Bark
Attach the Apron First
Attaching the Spiral Gutter
Completed Installation
Use of the Advanced Streak
Turpentining and Growth
Bark Chipping
Mounting and Sharpening the Bark Hack
Treating the Streak
Acid Penetration Above the Streak
Wounding the Tree for Gum Production
Metal Cups, Acid Corrosion and Gum Grades
Raising Tins Installed with Double-Headed Nails
Bark Pulling and Acid Treatment
How to Use the Spray-Puller
Acid Paste Method
Applying the Paste
Chipping and Paste Treatment
Streak Height
Turpentined Section Suitable for Other Wood Products
Beetle Attacks and Control Measures
The Black Turpentine Beetle
The Ips Beetle
Solutions for Beetle Control
3. PINES FOR THEIR OLEORESIN
Occurrence, Formation and Exudation of Oleoresin in Pines
Oleoresin Tapping
French Methods
Spanish Method
Greek Method
Indian Method
Mexican Method
American Bark-Chipping Method
The Austrian and German “Herringbone" Methods
Russian Methods
Methods in Other Countries
Felled Pine Wood as Source of Rosin and Turpentine
Composition of Oleoresin
Summary
4. PROCESSING OF OLEORESIN
Processing of Oleoresin
Olustee Gum Cleaning Process
Recovery of Turpentine and Rosin
Stripping Column
Multiple Tube Column
Luwa Columns
Fractionation of Turpentine
Batch Operation
Semi-Continuous Operation
Continuous Operation
Column Packings
Isomerisation of -Pinene
Camphene Via Bornyl Chloride
Catalytic Isomerisation of -pinene
Reaction Mechanism
Design Aspect of an Isomerisation Reactor
Liquid Phase
Vapor Phase
5. ROSIN DERIVATIVES AND ITS POTENTIAL
6. HYDROGENLESS HYDROGENATION OF RESIN
ACIDS
Experimental
Results and Discussion
Transfer Hydrogenation of Isopimaric/Pimaric Acids
Transfer Hydrogenation of Abietic Acids
Reaction Mechanism
7. NEW DEVELOPMENTS IN ROSIN ESTER AND
DIMER CHEMISTRY
New Rosin Esters
Chemistry of Rosin Dimers
8. TERPENE RESINS
Physical Properties
Chemical Properties
Manufacture
Uses
9. TERPENE BASED ADHESIVES
Introduction
Chemistry
Beta-Pinene Resins
Initiation
Propagation
Termination
Dipentene Resins
Alpha-Pinene Resins
Physical Characteristics of Resins
Pressure Sensitive Adhesives
Hot Melt Adhesives
Analytical Methods
Commercial Resins and Their Uses
Commercial Production
Applications in Pressure Sensitive Adhesives
Applications in Hot Melt Adhesives
10. OZONOLYSIS OF ALPHA-PINENE
Effect of Solvent, Ozone Concentration and Temperature on Yields were Investigated
Experimental Conditions are Discussed
11. -BROMOLONGIFOLENE
Steam Distilled Products
Residue
Chromic Acid Oxidation of Dilongifolenyl Ether
Lead Tetraacetate Oxidation of Longifolene
12. PEROXIDES FROM TURPENTINE
Peroxide Number and Degree of Unsaturation are Tests of Product Quality
Catalytic Hydrogenation of Pinene to Pinane is First Step in Hydroperoxide Production
Small and Large Scale Techniques of Pinane Oxidation are Investigated
Cold-Rubber Polymerization
Decomposition of Pinane Hydroperoxide
Over-all Yield of 85% is Realized in Production of High Purity Hydroperoxide
Peroxidation
Stripping of Oxidates
Polymerization
Heavy Metal Salts Accelerate Decomposition of Pinane Hydroperoxide
Decomposition
Summary
13. PINONIC ACID
Ozonolysis of -Pinene in Acetic Acid Solution Proved Best Method
Yields were Determined by Partition Chromatography
Ozone Source
Reagents
Ozonization
Calculations and Analyses
Direct Ozonolysis was not Successful
Ozonization in Methanol
Ozonization and Decompostion in Aqueous Acetic Acid at Room Temperature
Ozonization in Aqueous Acetic Acid at 0ºC. Decomposition in the Presence of Oxidants
Ozonization in Nitromethane
14. SYLVESTRENE AND SOME OF ITS DERIVATIVES
Sylvestrene
Sylvestrene Nitrosochloride
Sylvestrene Oxide
m-Terpineols
Sylvedihydrocarvone
15. 8-ACETOXYCARVOTANACETONE
16. RECOVERY OF 3-CARENE FROM CHINESE
TURPENTINE AND SYNTHESIS OF
ACETYLCARENES
Introduction
Distillation of Wood and Sulfate Turpentines
Material and Methods
Distillation Results
Synthesis of Acetyl-Carene
Materials and Methods
Results and Discussion
Synthesis Products
17. HOMOPOLYMERS AND COPOLYMERS OF
ACRYLATES
Introduction
Results and Discussion
Monomers
Homopolymerization
Copolymerization
Terpolymerization
Epoxidation
Curing
Hydrolysis of Polymethacrylate of I
Experimental
Reduction of -Campholene Aldehyde
Typical Preparation of a Monomer: Methacrylate of II
Typical Homopolymerization Recipe: Homopolymer Methacrylate of II
Typical Copolymerization Recipe: Copolymer of the Methacrylate of II and Acrylate of I
Solution Copolymer of the Methacrylate of II and Fumaronitrile
Typical Terpolymerization Recipe: Terpolymer of the Acrylate of I, Acrylonitrile and Butadiene
Typical Epoxidation Procedure
18. POLYMERS AND COPOLYMERS OF VINYL
PINOLATE
Preparation of Vinyl Pinolate
Polymerization
Reaction of Vinyl Pinolate Copolymers with Isocyanates
Experimental
Preparation of Vinyl Pinolate
Polymerization of Vinyl Pinolate in Solution
Polymerization of Vinyl Pinolate in Suspension
Polymerization of Vinyl Pinolate in Emulsion
Copolymerization of Vinyl Pinolate and Vinyl Acetate in Solution
Copolymerization of Vinyl Pinolate and Vinyl Chloride in Solution
Copolymerization of Vinyl Pinolate and Vinyl Chloride in Emulsion
Reaction of Polymers with Isocyanates
Evaluation of Vinyl Pinolate and Vinyl Chloride Copolymers
19. HOMOPOLYMERIZATION OF HYDRONOPYL
VINYL ETHER
Discussion
Experimental
Materials
Preparation of 2-Hydronopoxyethyl Vinyl Ether
Polymerization of HVE and HEVE
X-Ray Analysis of Poly (HVE)
Evaluation of Poly (HEVE)
20. TERPOLYMERS OF ETHYLENE AND PROPYLENE
WITH d-LIMONENE AND -PINENE
Introduction
Results and Discussion
Experimental
Materials
Preparation of EPT Rubber
Analysis of Unsaturation
Determination of Gel Content
Determination of Methyl Group Content in Polymer
21. LOW MOLECULAR WEIGHT POLYMERS OF
d-LIMONENE
Experimental
Materials
General Procedure
Results
Infrared Spectra
Nuclear Magnetic Resonance Spectra
Optical Activity
Perbenzoic Acid Oxidation
Discussion
22. BASE-CATALYSED ISOMERISATIONS OF
TERPENES
Hydrocarbons
Alcohols
Aldehydes
Ketones
Acids
Esters
Epoxides
Conclusion
23. COPOLYMERS OF VINYL CHLORIDE OF PINENE
Experimental
Homopolymerization
Copolymerization
Test of Heterogeneity of a Copolymer
Evaluation of New Polymers
24. POLYALLOÖCIMENE
Experimental
Monomer
Polymerizations
Polymer
Ozonolysis
Discussion of Results
25. ESSENTIAL OIL IN CHLOROPHYLL-CAROTENE
PASTE FROM PINE NEEDLES AND TWIGS
Abstract
26. ESSENTIAL OIL OF THE CONE OF PINUS
SYLVESTRIS VAR. MONGOLICA
27. COMPONENTS OF PINE ROOTS
Conclusions
Composition of the Remaining Neutral Fraction
Composition of the Carbonyl Fraction
Composition of the Hydroxyl Fraction
Results and Discussion
Composition of Turpentine
Composition of the Resin Acid Fraction
28. WOOD TURPENTINE OIL FROM PINE STUMPS
29. BLENDING OF TURPENTINE PRODUCTS
Lilac
Pine Bouquet
Cuir De Russe (for leather)
Violet
Lavender Bouquet
Oriental
Gardenia
Fougere
Eau De Cologne
Amber
Chypre
Ylang Syn
Sweet Pea
30. BIOLOGICALLY ACTIVE COMPOUND FROM
TURPENTINE
Terpenoids as Antimicrobials
Terpenoids as Anthelmintics
Terpenoids as Insecticides
Terpenoids as Plant Growth Hormones
Terpenoids as Anticancer Agents
Terpenoids as Pharmacological Agents
Terpenoid Derivatives as Biodynamic Agents
Terpenoids as Intermediates for Synthesis of Bio¬dynamic Agents
31. INSECTICIDES BASED ON TURPENTINE
Toxaphene (C10H10 CI8)
Strobane (C10H11CI7)
32. TALL OIL
History of Tall Oil
Production Processes for Tall Oil
Recovery of Tall Oil
Acid Refining of Tall Oil
Fractionation of Tall Oil
Composition and Properties of Tall Oil
Crude Tall Oil
Distilled Tall Oil
Acid Refined Tall Oil
Fractionated Tall Oil
Analysis and Testing of Tall Oil Products
Shipping, Storage and Handling of Tall Oil Products
Crude Tall Oil
Acid Refined Tall Oil
Tall Oil Fatty Acids and Distilled Tall Oils
Tall Oil Heads
Tall Oil Pitch
Tall Oil Rosin
Safety Notes
Applications of Tall Oil
The Chemistry of Tall Oil Fatty and Rosin Acids
Chemical Composition of Tall Oil Fatty Acids
General Reactions of Tall Oil Fatty Acids
Chemical Composition of Tall Oil Rosin
General Reactions of Tall Oil Rosin
Tall Oil Products in Surface Coatings
Tall Oil in Alkyd Resins
Tall Oil Formulations in Alkyd Resins
Esters of Tall Oil Products
Tall Oil Formulations in Esters
Other Uses for Tall Oil Products
Tall Oil in the Plasticizer Field
Esterification of Tall Oil for Plasticizers
Tall Oil in Adhesives and Linoleum Cement
Tall Oil in Rubber-based Adhesives
Tall Oil in Hot-Melt Adhesives
Tall Oil Products in Linoleum Cements
Formulation with Tall Oil
Formulation with Tall Oil Esters
33. DIMER ACIDS
The General Characteristics of Dimer Acids
Introduction
Dimer Acids Manufacture and Feedstock
By Products of the Dimerization Reaction
Monomer Acids
Trimer Acids
Structure and Properties of Dimer Acids
Structure of Dimer Acids
Analysis of Dimer Acids
Physical Properties of Dimer Acids
Chemical Reactions of Dimer Acids
Reactions of the Double Bonds and at the -Carbon Atoms
Reactions of the Carboxyl Groups to Produce Monomeric Derivatives
Reactions of the Carboxyl Groups to Produce Polymeric Derivatives
Commercial Applications of Dimer Acids and Their Derivatives
Introduction
Applications of Dimer Acids
Applications of Monomer Acids and Derivatives
Applications of Trimer Acids and Derivatives
Applications of Low-Molecular Weight Derivatives of Dimer Acids
Applications of High-Molecular¬ Weight Dimer Acids Derivatives
Applications of Other Polymeric Nitrogen Derivatives of     Dimer Acids

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Pinus

Introduction

The genus Pinus L comprising evergreen trees has been known to mankind from time immemorial. Theophrastus (372 287 B.C.) in his early writings made a reference to the morphology and reproduction of pines. Its decorative value has been exploited in old Chinese paintings. Pine incense used to be burnt in the religious ceremonies of the Mayas  the Aztecs and the Romans.

The pines have been traced back in geological history to the Jurassic period (150 million years) though they reached their climax of distribution only in the Tertiary (60 million years). By the lower Cretaceous (125 million years)  two distinct groups emerged  viz.  (i) Haploxylon or soft pines and (ii) Diploxylon or hard pines. The plants exhibit an exceptionally long life. In the Inyo National Forests of California  USA  there is a tree of Pinus aristata  which is more than 4600 years old  still producing cones occasionally.

Pinus belongs to the family Pinaceae or Abietaceae of the order Coniferales. The other genera included in this family are Abies Mill.  Cathaya Chun & Kuang  Cedrus Link.  Keteleeria Carr.  Larix Mill.  Picea A. Dietr.  Pseudolarix Gord.  Pseudotsuga Carr.  and Tsuga Carr.

Some of the characteristic features of the family are as follows  the plants are monecious  the microsporophylls are spirally arranged with two abaxial sporangia per sporophyll; female cones with numerous spirally arranged pairs of scales (seed scale complex)  viz. ovuliferous scales and the bract scales  the former free from the latter or only slightly fused at the base; ovules adaxial with their micropyles directed towards cone axis; and seeds generally winged.

Distribution

The genus has a cosmopolitan distribution and is represented by about 105 species Jackson however  mention c. 80 valid species. It is found mainly in the northern hemisphere  northern Europe  northern and central America  Bahamas  British Honduras  the subtropics of North Africa  the Canary Islands  Afghanistan  Pakistan  India  Burma and the Philippines  crossing the Equator in Indonesia. In the tropical countries like India  it is found in the hills with subtropical or temperate climates  though some pines are grown as ornamentals even at lower altitudes.

Distribution in India

In the Indian subcontinent there are six species of Pinus of which four are distributed in the Himalayas. They are P. roxburghii Sarg.  P. wallichiana A.B. Jacks.  P. insularis Endl.  and P. gerardiana Wall. ex Lamb. A few trees of P. armandii Franch. occur in the North East Frontier Agency  NEFA P. merkusii Jungh. & de Vriese grows on the hills of Burma. The altitudinal range of these pines varies considerably.

Apart from indigenous species  some exotic species also occur. These are listed below along with the areas where they were successfully planted.

 

Morphology

In their general habit  young pine trees are pyramidal with their horizontal branches disposed in regular whorls. As the tree matures  this symmetry is lost and the crown becomes rounded  flat  or even spreading. Under cultivation  when planted close  the trees lose their branches and thus have a considerably long bole.

The stem bears two types of branches  (i) branches of unlimited growth or long shoots  and (ii) branches of limited growth or dwarf shoots  also termed brachyblasts. The long shoots appear on the main stem as lateral buds in the axils of scale leaves. Each of these shoots terminates in an apical bud  which is enclosed by a number of bud scales closely surrounded by a thick mat of hairs. The lateral buds grow more or less horizontally to a certain length  and this growth has been termed nodal growth. In some pines this growth is restricted to the production of a single internode every year (uninodal pines)  but in some others there may be two to several internodes per year (multinodal pines).

The dwarf shoots or foliar spurs develop on the long shoots  arising in the axils of scale leaves. Each dwarf shoot initially has two opposite scales  termed prophylls  followed by 5 13 spirally arranged  scaly cataphylls. These are in 2/5 phyllotaxy. Finally  depending upon the species  1 5 needle like leaves develop. Unlike the long shoot  the dwarf shoot lacks a terminal bud. The leaves are of two kinds  (i) the foliage leaves which appear only on the foliar spurs  and (ii) the scale leaves  which are developed as protective structures.

The male and female cones are borne on the same tree  though on different branches. They become visible towards the end of spring or the beginning of summer. The male cones (the modified dwarf shoots) appear in clusters (catkin) on the lower branches of the tree  whereas the female cones  which replace the terminal buds of the long shoots  are the modified long shoots. In most of the species  including Pinus roxburghii and P. wallichiana  the mature female cones open and release the seeds  but in others the seeds are released only after the cones fall to the ground and rot. In a few species such as P. flexilis  the cones remain on the tree for several years and open only when they are scorched by forest fire.

The pines are generally light demanders; a few can tolerate partial shade for several years  but their growth is stunted. They do not thrive in areas  which remain hot and humid throughout the year. Only a few species like P. taeda grow successfully on wet lands. Alternation of seasons dry and wet  and warm and cold  or often a combination of both is required for the normal development of pines.

There are several external characters  which facilitate the identification of different pines. The number of needles per dwarf shoot  their length  the position of the umbo on the apophysist and the shape  size and colour of the resting bud are some of the important ones.

P. wallichiana  the blue or Bhutan pine  commonly known in trade as Kail  is found in the Himalayas mainly from Kashmir to Bhutan at altitudes of 1 500 3 000 m. It has also been recorded at as high an altitude as 3 600 m along the region of Namchebazar and Thengopoche. It is very common in the Western Himalayas in Kashmir valley  Simla  Chakrata and Mussoorie and in the eastern Nepal at altitudes of 1 500 2 135 m. In Bhutan  it occurs along the valley above the river Tista (lower Rangeet valley). Though this species is sporadically distributed along the eastern part of the Kameng division of NEFA  it is most dominant in the Khalaktang area  Rupa valley and the Dirang Dzong valley at an altitude of 1 500 m  covering an extensive area along the hill slopes. In the Subansiri division of NEFA  the species is restricted to the mountain slopes surrounding the Apatanang valley at an altitude of 1 500 1 830 m. Here it appears to have been introduced  since there is no trace of the species in the surrounding mountain slopes.

The species is found on a variety of geological formations  growing best on well drained moist soil with an annual rainfall of 100 200 cm. Some of the best forests are found on mica schist  which breaks down into ideal soil. It is frequently associated with Cedrus deodara (Roxb). G. Don  Abies pindrow (Royle) Spach  and Picea glauca (Moench) Voss.

The blue pine is an elegant tree  30 90 m high  with horizontally spreading branches. The young shoots are glaucous green. Each dwarf shoot has five needles  12.5 20.0 cm long  and the leaf sheaths (scale leaf  prophyll and cataphyll) are non persistent. The winter buds are cylindric conic  0.6 1.2 cm long. The female cones are 15 30 cm long with rounded ovuliferous scales. The seeds are winged; wings membranous  about thrice as long as the seed.

Under abundance of light and protection  the blue pine regenerates profusely. The seeds germinate during rainy season. If artificially regenerated  direct sowing is preferred to transplanting. The young trees grow fairly rapidly  but on reaching maturity the girth increment becomes slow and growth in height may almost stop.

Kingdon Ward reported the occurrence of this species in the NEFA area. The tree attains a height of 18 m and a diameter of one metre. The winter buds are cylindrical  blunt and slightly resinous. The needles are 10 15 cm long. The female cones are subterminal in groups of 2 3; cone is 2 5 cm or more long  broadly tapering into rounded apex. The wingless seeds are 1.3 1.6 cm long and are liberated soon after they ripen.

The taxonomic status of P. insularis and P. kesiya Gord. is not satisfactorily settled. There is a strong possibility that these two names refer to the same species. Savory made a study of the morphology  and anatomy of the wood of these two species. No significant difference was found between them to justify their separation. Accordingly  Pinus insularis Endl. has been treated by some authors as a synonym to P. kesiya Royle ex Gord. in Loud  Gard. mag. 16  8  1840.

The Khasi pine is restricted only to the eastern Himalayas  where it is commonly found along the various ranges of the Garo. khasi and Jaintia hills (800 2 000 m). The species has been introduced successfully in the Aijal area of the Lushai hills (1 220 m). In the northern part of Manipur and the Naga hills round about Kohima (1 220 1 830 m) it appears in isolated patches. The plant grows well in fairly moist regions  free from extremes of heat and cold on loose textured soil like granitic or sandstone rocks covered with clay.

The tree is 60 90 m in height and trunk up to 6 m in diameter. The bark is thick  reddish grey and deeply fissured giving a reticulate appearance. The branches are arranged in whorls forming a rounded crown. The leaves are in fascicles of threes and are 15 25 cm long  slender with acute apices. The old needles fall for the most part during April May  though the scale leaves are persistent.

The male and female cones appear on the new shoots during February March. The mature male cones are light brown and 3 5 cm in diameter. The female cones are approximately 5.0 7.5 cm long and 4 6 cm in diameter and are the smallest amongst the Indian pines. They are ovoid and initially light green but turn brown as they mature. The prominent umbo is sharply mucronate in the centre. The seeds have long wings  which are about four times the length of the seed.

The plants come up naturally in places of abandoned or shifting cultivation  or in areas where undergrowth of forests has been burnt. For artificial regeneration the seeds are sown broadcast. The growth rate is fairly high.

Of all the Indian pines  P. roxburghii is the most important and is known as the Himalayan long leaved pine or Chir pine. It is peculiar to the main valleys of the western Himalayas at altitudes of 460 1 500 m  and extends into Bhutan (Biswas  1933). Along the eastern Nepal this species is restricted to lower elevations. In NEFA  along the Kameng Frontier Division  it appears to be very sparsely distributed among the pure and extensive formations of P. wallichiana. It either forms a pure forest or occurs as a co dominant species with other plants. At higher altitudes  it is associated with cedrus deodara (Roxb.) G. Den  Pinus wallichiana  ouercus inlana roxb.  and Rhododendron arboreum Smith whereas at lower altitudes  it is found along with Anogeissus latifolia Wall.  Bauhinia latifolia Cav.  B. variegata L. and Shorea robusta Roxb.

P. roxburghii is a large evergreen tree with a spreading crown. The young shoots are grey to pale brown and the winter buds are ovoid and non resinous. Leaves 15 40 cm long  three on a dwarf shoot. The mature female cones are 12 24 cm x 7.5 14.0 cm  the ovuliferous scales having reflexed apices. The umbo is very prominent and the seeds are about 8 16 mm long with c. 2.5 cm long membranous wings.

Natural regeneration is normally through seeds. Mature cones are collected from healthy trees for artificial regeneration  placed in hot sun to loosen the scales and then the seeds thrashed. This is normally practised where coniferous forests have been damaged by fire and is mostly done by direct sowing (With India  Raw Materials  VIII).

This species is the source of Chilgoza or Nioza seeds of commerce  which are eaten as such or after roasting. It is found in northern Afghanistan and in the north western Himalayas  occurring on the borders of Tibet  Kashmir and Pakistan. It also occurs in Kalpa (Kinnaur) and Pangi districts of Himachal Pradesh.

The plant is an evergreen tree  18 m or more in height and 1.8 2.4 m in diameter. It grows on dry  rocky grounds at an elevation of 1 830 3 600 m. It thrives best in areas where the rainfall is scanty  but winter snowfall is heavy. The species can easily be identified by its bark  which is shed in small flakes. The branches are ascending and are either obscurely whorled or not whorled. They are comparatively thin  grey  with mottled appearance. The shoots are glabrous and greyish green. The winter buds are spindle shaped and nearly 1.5 cm long. The stout short leaves are c. 5 10 cm long and occur in groups of threes on dwarf shoots. The male cones are visible during May June  when pollination takes place. The female cones are large  hard and woody having reflexed  triangular umbos. Each cone is 15 20 cm × 10 13 cm.. The seed is c. 2.5 cm long with a very short rudimentary wing.

P. merkusii is the most tropical of all pines and is of common occurrence in the southern Shan States of Burma. It has been recommended for planting along the eroded hill slopes of the Andaman and Nicobar Islands. Commonly known as Tenasserim pine  it normally attains a height of c. 20 m when mature. The bark is grey to brown  thick and deeply fissured. The leaves are in pairs  17 33 cm long  persisting for 1 ½ 2 years. The female cones are cylindric  borne in pairs and at maturity reach a length of c. 5.7 cm. The umbo is rhomboid and furrowed. The small seeds are winged.

Anatomy

Root

The plant possesses initially a primary taproot with a large number of laterals  arising in an acropetal succession. In most cases  the growth of the primary root soon becomes arrested  while the laterals  termed long roots  continue to grow. Later  the dwarf roots arise in clusters on the long roots. They branch dichotomously and form coralloid masses. Some of these harbour an ectotrophic mycorrhiza and are termed mycorrhizal roots.

Long roots. In a transverse section the epidermal cells appear more or less isodiametric and many of them are filled with tannin as in P. roxburghii  P. wallichiana and P. gerardiana. The broad cortex is distinguishable into a peripheral zone of small and an inner zone of large perenchymatous cells. Frequently  the cells of both the zones are filled with starch. The endodermis is composed of suberized cells  usually impregnated with tannin  which gives them the brownish orange colour. It shows indistinct casparian strips  followed by 6 7 layers of pericycle. The walls of the peripheral pericyclic cells are slightly thickened while those of the inner cells are thin. Many of them contain tannin.

The stele is generally diarch or tetrarch  but may sometimes show pentarch condition. The number of protoxylem elements varies from 8 to 16. Each protoxylem point is associated with a resin duct and consists mostly of scalariform or scalariform pitted tracheids  while the metaxylem is made up of pitted trachieds. The phloem  which alternates wit the xylem strands  consists of parenchyma  sieve and tannin cells. The pith cells contain a considerable amount of starch; some of them also contain tannin.

Secondary growth sets in when the primary tissues are still in the process of differentiation. A zone of cambium differentiates from the parenchymatous cells beneath the phloem. This by repeated periclinal divisions forms secondary xylem towards the pith and secondary phloem towards the cortex. In the region of the resin ducts  the cambium cuts off only parenchymatous cells  resulting in broad xylem rays. With subsequent development of the secondary wood  the rays are reduced to the width of only a single cell.

The secondary xylem is made up of tracheids with bordered pits on their tangential and lateral walls. Many tracheids get blocked with tyloses in older roots. The rays are either uni or multiseriate  the latter being always associated with resin ducts.

The primary phloem soon gets crushed and is unrecognizable. The secondary phloem consists of radially oriented (disposed) rows of cells. Many of the parenchymatous phloem ray cells contain tannin.

Pine Oleoresin Extraction Methods

Introduction

Modern gum naval stores methods have been developed to benefit both the gum producer and the timber owner. Following the methods described in this booklet will bring maximum gum yields  will reduce chipping labor requirements about 50 percent  and will make the worked out tree saleable for other wood products.

If these modern turpentining methods are used  naval stores can be integrated in the management plan for pine timbered lands and timber owners can almost double the dollar value per tree by leasing or working for naval stores before they harvest.

The aim of this booklet is to bring together in one place all the best modern methods of producing gum  and to describe the principal factors that affect gum flow.

The extraction methods and application techniques described here were developed during 15 years of research and testing by scientists at the Forest Research Institute with the cooperation of gum producers and timber owners throughout the gum naval stores belt.

Cup the Larger diameter Trees for Increased Yields and Greater Profits

A crop of single faced trees 11 inches in diameter will produce 60 barrels more gum per year than 9 inch trees. The costs for installing tins and for chipping are about the same for 9 and 11 inch trees. The number of small diameter trees worked can be the difference between break even and profitable operation.

Double Facing. Only one face per tree should be installed on trees smaller than 14 inches in diameter. Simultaneous working of two faces installed on one tree does not mean that gum yields from that particular tree will double. The yield from two faces worked simultaneously is normally not more than 70 percent of the yield  which could have been obtained from two faces  worked one at a time.

Two faces should be installed on trees 14 inches d.b.h. and over for obtaining the greatest yield if the trees are to be worked out in 4 years.

The volume of gum produced is directly related to the width of the face. Good gum yields can be obtained with a face width equal to the diameter of the tree measured at breast height. For example  a 10 inch tree should have a 10 inch face and a 12 inch tree a 12 inch face.

Gum Yield from Shoulders. With bark chipping and acid treatment  75 percent of the gum yields at each dipping flows from the shoulders of the face. If careless chipping extends the streak ½ inch beyond the range of the tins on each side of the face  a barrel of gum is wasted during the season for every 310 trees worked.

Use Correct Tin Lengths. One piece tin assemblies or broadaxe inserted tins will not give full face widths on 12 inch trees and larger. For full face widths and good gum yields  use 10 inch spiral gutters on trees 9 to 12 inches in diameter. Use 12  inch spirals on trees 12 to 16 inches in diameter. For an apron  use a 7 or 8 inch straight or curved gutter with either length.

First Year Installation of Spiral Gutters with Double Headed Nails

Shaving the Bark. Shave off the rough bark using double edge  shove down scrape iron or a bark shave tool. Shave only the area where the tins will be nailed and the cup will sit. Shave a fairly flat seat for the apron and cup; keep the spiral gutter side of the tree round. Remove enough bark to get rid of the deep cracks.

Attach the Apron First. Drive the first nail at the middle of the apron. Level the apron and drive the second nail in the left shoulder. Set this nail close to the end of the tin so as to get full face width. Drive all nails near the top edge of the tins; this pulls the edge into the bark to prevent leakage behind the tins. Pound the inner lip of the right hand end of the apron so that it fits snugly against the tree. Do not nail the right hand end at this stage.

Use only double headed nails designed specially for attaching and removing naval stores tins.

Attaching the Spiral Gutter. Lap the lower end of the spiral gutter over the right hand end of the apron. Set the angle of the spiral between 30 and 40 degrees    around 30 for slash and steeper for longleaf pine. Drive the first nail in the middle of the spiral. Drive the next nail through both the spiral gutter and the apron at the overlap. Drive the shoulder nail last. Close any gaps between the gutter and the bark by pounding the inner edge of the gutter into the bark.

Completed Installation

The double  headed nails are numbered in the photograph to show the order in which they are driven. To support a large 2 quart cup  a 30d flathead nail is used. A standard size cup takes a 20d nail. Drive the cup nail at a slight angle so outer edge of cup will snap over nail head. This holds cup snugly against tree.

Use of the Advanced Streak

With bark chipping and acid treatment  the familiar  lead  or advance streak is not necessary  as it will not increase the volume of gum produced the first year from virgin installations. An advance streak applied 30 days before the regular chipping season begins will give good early season yields for the first 8 weeks of the season  but yields for the remainder of the season will be reduced proportionally.

Producers may consider it desirable to produce an increased volume of gum during April and May. There may be a psychological effect in getting something in the cup quickly to spur the interest of chipping and dipping laborers.

The best type of advance streak for good early season yields is a bark streak 5/8 to 3/4  inch high  treated with 50  percent sulfuric acid  applied 30 days in advance of the regular chipping season.

Turpentining and Growth

Measurement data covering a 2 year period from a plantation of 20 year old slash pine  growing at the rate of 8 annual rings per inch  with 15 × 15 foot spacing  and worked with modern gum extraction methods showed that

The annual volume increment in cubic feet of turpentined trees was 26 percent less than that of round  unworked trees. This reduction in growth was correlated with the width of the face on the tree; the wider the face on a tree of given size  the slower the growth. For normal face width equal to the diameter of the tree  the annual deficit per turpentined tree would be about 2 cents for pulpwood and 5 cents for saw logs  at current stumpage prices. The gross value for naval stores per year would range from 15 to 25 cents per tree.

Growth loss from turpentining was not directly related to the volume of gum extracted from the tree annually. Thus  the extent of growth loss is the same for indifferent work and poor gum yields  as for skilled work and good yields.

Bark Chipping

The bark hack removes the outer  rough bark and the white  inner bark  exposing the gum ducts in the wood. Acid is then sprayed on the surface of the wood. The action of the acid holds these gum ducts open for a period of 2 weeks. It is the acid that makes the gum flow from the tree for the 2  week period. Chipping merely prepares the area for acid treatment. It is not necessary to cut into the wood with the bark hack  because a wood streak ½ inch deep will not produce any more gum than a streak of bark depth  both treated with acid.

How Often to Chip and Treat. Treating the streak with acid prolongs the flow of gum; therefore it is necessary to chip and treat only once every 14 days. Chipping and treating every 2 weeks during the chipping season will get practically all of the gum the tree can produce over a period of 4 to 6 years.

Height of Streak to Chip. For maximum gum yields over a 4 year period  bark streaks ¾ inch high are recommended for both slash and long leaf pine.

Mounting and Sharpening the Bark Hack

The bark hack has been designed with a special flat bill  square corners and high jaws to cut through two thicknesses of bark. If it is correctly mounted and sharpened  clean streaks can be chipped and blades will last several years.

The angle (called  pitch ) at which the hack head is mounted in the wooden stock helps to prevent chipping into the wood. The best mounting angle for speedy bark chipping is shown below.

Proper sharpening of a bark hack blade contributes greatly to the chipping of a clean streak and actually determines how long a blade will last.

A steel cutter may be used to cut out and to thin the edges of a new blade  as illustrated below  but the final sharpening touches should be with a flat file. Do not use the cutter to resharpen the edges; use the flat file or whetstone.

Quite often laborers will file a long  keen bevel at the bill to make woodcutting easier. But the corners will soon break  leaving large gaps in the blade. The blade should be filed so that the corners are kept square at all times. A rounded or gapped corner will leave patches of inner bark in the streak. These patches of bark will stop the flow of gum from above the streak and reduce monthly yields.

In many instances  poor gum yields from bark chipping and acid treatment have been traced directly to such a simple cause as improperly sharpened hack blades. To reduce the excessive breakage of blades  for speedier bark chipping  and for maximum gum flow from each streak  producers should occasionally check with their laborers on the sharpening and mounting of bark hack blades.

Treating the Streak

The difference between poor and good yields each month is directly related to the amount of acid properly sprayed on each freshly chipped streak.

A 50 percent solution of sulfuric acid is used on both slash and longleaf pine. The plastic bottle of the acid sprayer is filled only two thirds full  and the sprayer is held at a 45 degree angle for obtaining good treatment. Keep the nozzle tip from 1 to 2 inches below the top of the streak and from 1 to 2 inches away from the tree. Move the sprayer in one steady motion across the streak  spraying enough acid to wet the streak thoroughly from shoulder to shoulder.

The sprayer should be aimed so that the spray from the nozzle hits the streak at the line where bark meets wood. The acid should be discharged from the sprayer in the form of a spray. Normally  a stream of acid does not give good treatment  because a stream hits the streak with force  spatters and the major portion runs down the face as waste.

Good treatment is of vital importance  and laborers must be consistently supervised to assure quality treatment for profitable gum yields.

Acid Penetration Above the Streak

For acid treatment to be effective  the acid must penetrate the area above the exposed wood at the streak line. Acid penetration causes a reddish brown color in the white  inner bark and on the surface of the wood. Penetration above the streak is necessary and is obtained only by good treatment  in which the streak is wet thoroughly and evenly.

Height of Acid Penetration. The volume of gum produced by each streak is directly related to the distance the acid penetrates above the streak; the higher the penetration  the greater the yield. The penetration line and the tissues killed by acid treatment can be seen when the next streak is chipped.

Normally  50 percent sulfuric acid properly applied in sufficient quantity will penetrate ½ to ¾ inch above the streak in 14 days. Good penetration is obtained by using the acid sprayer correctly  as the acid must be sprayed into the top portion of the streak. Through careless application  most laborers waste more acid per streak than is needed for good treatment.

If the height of acid penetration is under ½ inch  then treatment has been poor  and maximum yields will not be obtained from that streak. Poor treatment can usually be traced to careless application.

For best gum yield  the tissues killed by acid penetration should be removed and fresh green wood exposed with each streak chipped. Serious yield decline may result unless the chipping keeps up with the acid penetration.

 

Pines for their Oleoresin

Pines  besides being a source of valuable timber and pulpwood  yield pitch  tar  rosin or colophony and turpentine  collectively known as naval stores  a term coined to these owing to their use for construction and maintenance of sailing vessels as sealing compounds for their wooden hulls. Rosin and turpentine are obtained by distillation of crude pine oleoresin  exuding from the trunks of standing pine trees as a result of injury. Rosin and turpentine are also obtained by distillation or solvent extraction of felled pinewood and wood waste. In the paper pulp industry  rosin and turpentine are obtained as one of the important by products. Pine rosin and turpentine as used in most varietal ways and form raw material to a number of industries all over the world. Rosin finds use in soap  paper sizing  wall board  synthetic rubber  adhesives  paint driers  varnishes  lacquers  paints  water proofing compounds  axle greases  cements  linoleum  floor waxes  pharmaceuticals  inks etc; turpentine in paint and varnish thinning  rosin solvent  lacquers  water proofing compounds  synthetic pine oil  insecticides  terpene resins  synthetic camphor  flavours and perfumes  refined terpenes and derivatives  rubber  pharmaceuticals  polishes etc.

Geographic distribution of pines. The pines belong to 94 recognized species of the genus Pinus. Except one species  P. merkusii (Merkus Pine) which crosses the Equator in Sumatra (Indonesia)  in nature  all the pines are confined to Northern Hemisphere  extending from polar region to the tropics. A list of species  represented in the natural flora of different countries  is given in the Appendix I.

Pines tapped for oleoresin. The important pine species tapped for their oleoresin in different countries are  P. palustris (Longleaf Pine) and P. elliottii (Slash Pine in U.S.A.; P. pinaster (Cluster or Maritime Pine) in France  Portugal and Spain; P. Sylvestris (Scots Pine) in U.S.S.R.  Finland  Norway  Sweden  Germany  Poland  Austria  Yugoslavia  Bulgaria and Hungary; P. halepensis (Aleppo Pine) in Greece  France  Spain and Algeria; P. nigra (Austrian or Black Pine) in Austria  Albania  Bulgaria  Italy  Spain  Yugoslavia  Greece and Turkey; P. Sibirica (Siberian Stone Pine) in U.S.S.R. (Western and Central Siberia); P brutia (Calabrian Pine) in Turkey; P. peuce (Balkan Pine) in Bulgaria; P. pinea (Italian Stone Pine) in Northern Italy; P. heldreichii in Yugoslaiva; P. ayacahuite (Mexican White Pine) and P. teocota (Aztec Pine) in Mexico; P. caribea (Caribbean Pine) in Honduras; P. roxburghii (Chir Pine) in India and Pakistan; P. thunbergiana (Japanese Black Pine) in Japan; P. massoniana (Masson Pine) and P. tabulaeformis (Chinese Pine) in China; P. merkusii (Merkus Pine) in Indonesia (Sumatra Island. In U.S.A. P. taeda (Loblolly Pine) and P. ponderosa (Ponderosa or Western Yellow Pine) are also tapped sometimes. More than three quarters of pine oleoresin are derived from P. palustris  P. elliotti (U.S.S.)  P. sylvestris (U.S.S.R. and Northern Europe) and) P. pinaster (France  Italy  Portugal and Spain); oleoresin from the former three species comprising the most of it.

Besides  following countries have also examined various pines that are growing naturally or introduced there  to develop their naval stores resources. They are P. pinea in Spain; P. pithyusa  P. pallasiana  P. nigra var caramanica and P. sylyestris var. hamata in U.S.S.R.; P. halepensis in Cyprus  Israel and Tunisia; P. brutia in Syria; P. insularis in Burma and Philippines P. elliottii in Argentina  Brazil and South Africa; P. radiata in Australia  Chile and New Zealand; P. pinaster and P. caribaea in Australia and South Africa; P. roxburghii in South Africa. P. caribaea var. hondurensis in British Honduras; P. kesiya (P. khasya) and P. wallichiana in India; P. taiwianensis in Taiwan  and  P. densiflora in Japan

World production of pine rosin and turpentine. Prior to World War II  most of the world s supply of rosin and turpentine came from U.S.A.  and even today it tops in naval stores production. But since then considerable advance has also been made by several other countries  particularly U.S.S.R. and China (People s Republic)  Around 1959 about 1.72 million hectares of pine forest  with an yield upto 100 Kg. crude oleoresin per hectare  were tapped in U.S.S.R. Basing on the average of world s total production of 1964 to 1966  about 47.0%rosin and 42.5% turpentine is produced in U.S.A.  15.8% rosin and 13.3% turpentine in U.S.S.R.  8.6% rosin and 10.4% turpentine in China  7.2% rosin and 6.4% turpentine in Portugal  3.7% rosin and 2.9% turpentine in Mexico  3.0% rosin and 3.5% turpentine in Spain  2.9% rosin and 3.0% turpentine in France  2.8% rosin and 2.2% turpentine in India  2.2% rosin and 2.1% turpentine in Poland  1.9% rosin and 2.0% turpentine in Greece  and rest of it  i.e.  about 4.9% rosin and 11.2% turpentine collectively by 14 other countries. The estimated production of rosin and turpentine in the different countries  during late fifties and early sixties.

Occurrence  Formation and Exudation of Oleoresin in Pines

Occurrence. In pines the oleoresin is formed and translocated in the resin canals  occurring in root  wood and inner bark of the stem and leaves. The normal resin canals are longitudinal  running parallel to axis  or transverse  running at right angle to it. Transverse canals are always included in the fusiform rays. The oleoresin in the longitudinal canals tends to reach the surface by means of transverse ones. The size of resin canals varies according to their orientation  species  age and growth rate of trees. The longitudinal canals are invariably larger in diameter then transverse ones. These are very large in diameter in species like P. lambertiana (average 175 255 µ  maximum over 300 µ)  P. roxburghii (200 225 µ  and P. ponderosa; large in P. strobus (average 135 150µ  maximum 200µ)  P. kesiya  (130 150µ)  P. palustris  P. elliottii  P. taeda  P. rigida and P. echinata; medium in P. banksiana (upto 100 µ)  P. contorta (60 105 µ) and P. wallichiana (70 85 µ) (106  196  210). Their proportion as per cent of wood volume  is 0.3% in P. ponderosa  0.5% in P. lambertiana 0.7% in P. strobus and 0.8% in P. palustris. In P. peuce their number averages to 11 per linear cm. or 61 per sq. cm.  and of these about 97% occur in the late wood  whereas  the early wood contains only 3%. In all the 3 Indian pines  viz.  P. roxburghii  P. kesiya and P. wallichiana  the number of both longitudinal and transverse canals has been recorded as 0 to 2 per sq. mm.  except the longitudinal canals in P. kesiya where it is 0 to 3 per sq. mm. of wood; the diameters of radial canals  which are smaller than the longitudinal ones  are 40 to 5µ  30 to 35µ and 30 to 40µ respectively.

Traumatic resin canals  arising as a result of injury  may accompany transverse canals of normal type. They may be longitudinal or transverse  but both seldom occur together. The longitudinal traumatic canals are generally arranged in a tangential row and usually restricted to early wood. The traumatic transverse canals are confined to rays and are larger in diameter than normal transverse canals. The epithelial cells of traumatic resin canals are thick walled  whereas  these are thin walled in normal canals.

In softwoods like pine  resin is also contained in ray parenchyma cells  in addition to the resin canals. The resin in epithelial cells of canals is generally fluid type  whereas  in parechymatous cells adjacent to trachlieds it is more viscid. Direct analysis of parenchyma resin has not been carried out but  the proportion of canal resin to total resin has been calculated to be 40% in P. palustris.

Formation. The oleoresin is produced in the epithetical cells of the canal and adjoining living parenchymatous cells  which are especially active in the outer sapwood. The oleoresin is under pressure exerted by the epithelial cells into the lumen of canal; this pressure  called oleoresin exudation pressure  is responsible for the exudation of oleoresin when the trees are tapped. As the normal canals pass from sapwood into heartwood  they cease to function and are frequently occluded with tylosoids  and are gradually plugged entirely.

Evidence drawn from reciprocal grafts of P. sabiniana and P. ponderosa was that the oleoresin is formed locally and is not supplied from tree crown. The site of oleoresin synthesis  in the epithelial and sheath cells of the canals  was considered to be in the plastids and later on in the endoplasmic reticulum. A recent study in P. halepensis allocated the site in special organelles  i.e.  spherosomes  in epithelial cells of canals and adjacent living parenchymatous cells. These organelles were especially active in younger tissues  which contained a higher proportion of resin acids than the older ones. The terpenes are suggested to be produced in the spherosomes at a later stage of their development into the oleoresin.

Mechanism of oleoresin exudation. Studies have been carried out on the anatomy of tapped faces and mechanism of resin flow in P. pinea. Wounding causes differentiation of traumatic resin canals at that level and the tissues surrounding the faces get soaked with resin  more abundantly at the lower levels. The normal longitudinal resin canals  reached by the wound  become obstructed by tylosoids formed in the interior of the canals  and also they get elongated tangentially with their orifices divaricated. In intact longitudinal canals  the resin is always contained in the resiniferous cells and never runs into the lumen. The canals interrupted by traumatic lesions on the other hand  the secretory cells react in one of the two ways either by turgescence  which tends to immobilize the resin in the cytoplasm  or in following sequence of processes the resin emulsifies in the cytoplasm  the vacuole disappears  the nucleus degenerates  the cell membranes thicken and turn into lamellaes  the pits enlarge and the resin exudes through them into the lumen  and perhaps only the cells reacting in the later fashion are able to feed the flow of resin from a wound. Resin flow from the wound is governed by three principal conditions a physiological defence mechanism  consisting in a very rapid increase in cellular turgescence leading to the occlusion of the interior of the canal by swelling of its epithelial cells; this phenomenon which takes place relatively far from the wound in cells of live tissues  is accompanied by a hyper secretion of resin; emulsifying of the resin in the water of cellular cytoplasm  its displacement  and its oozing through the pit membranes to the interior of canal  total dehydration of cells and embalming of their membranes by the resin giving a characteristic laminated appearance. At the dehydration stage the resin flow appears to cease  and it therefore seems that it is controlled by the water in the secretory cells.

Oleoresin Tapping

The oleoresin tapping also called  turpentining   implies in general to several operations  such as selection of trees  making of blaze or face on the tree  fixing of lips and pots to collect the resin exuding from the cut face  freshening of the blaze  collection of oleoresin and scrape (solidified oleoresin).

There are two methods of oleoresin tapping which in French are termed as le gemmage a vie (cautions or light tapping) and le gemmage a mort (tapping to death); former method aims at obtaining the oleoresin without causing the death to trees and is adopted for longer spells  while the second method exhausts and kills them. The later method is adopted only when a tree is to be felled soon after. Before introduction of cups and lips  oleoresin exuding from the blaze was allowed to run down to the foot of the tree  where it was received in a little trough hollowed out in one of the roots in the sand. This practice resulted in much waste and contamination. Hugues method  employing lips and pots  was introduced in Landes (France) for the first time in 1844  which spread in the region by 1885. Hugues method soon formed the basis for oleoresin tapping in a number of countries. The salient features of principal resin tapping methods in vogue in different countries  are described here in brief

French Methods.

P. Pinaster is the principal oleoresin yielding species in France. Methods adopted for tapping are as follows.

Hugues method. (a) Le gemmage a vie This method suggests tapping of trees 110 cm. g.b.h. or above  but often trees of 90 cm. g.b.h are also tapped. The initial blaze is made at the base starting a little above the ground level preferably on the eastern face and worked for 5 years. A second one is added on trees of 130 cm. g.b.h. or above. The season of tapping in France extends to about 8 months (1st March to 31st October). During this period about 30 streaks or freshenings are made at 8 day intervals with an adze (abschott) and with a rasclet when it reached higher. In a season about 6 to 7 crops are collected. Before actual tapping starts gradual thinning of bark to a height of about 60 cm . and width of 15 to 20 cm.  nearly reaching wood in the middle  is made as early as the 2nd week of February.

Initially the blaze is 9 cm. wide and is extended upward to 60 cm. height  during the freshenings by the end of first year. Depth of the initial blaze and freshenings increases from the sides inwards reaching a maximum of 1 cm. in the middle. Similarly  in subsequent years  freshening is made upward in continuation of the previous years s blaze (face).

Le gammage a mort  This method of tapping to death is used in the last 5 years of felling. The blazes are made as close as possible in the 1st year and worked for 4 years. Generally one blaze is made on trees of 50 60 cm. g.b.h. and a blaze is added for increase of every 20 cm. The blaze width and height is not actually restricted in a mort tapping. Freshening of blazes is done once or twice a week.

Bellini s method. Bellini around 1930 introduced a new method. In this a circular incision about 5 cm. in diameter and 2 to 3 mm. deep is made  just sufficient to pierce below the outer bark  by a special drill like tool. The cut is gradually enlarged during the season  upto 10 cm. diameter and 1 cm. in depth. The face is protected by a sort of cover  protector . The oleoresin from the blaze is led through a tube  receptacle  into the container (bottle). This method  though facilitated working of many faces on a tree at a time and collection of oleoresin in pure and liquid form  retaining much more turpentine content  did not gain wide attention owing to high labour costs.

Spanish Method

In Spain P. pinaster is the principal species constituting about 94% of the total pine stands tapped for oleoresin; the other two species  viz.  P. helepensis and P. nigra var. calabrica constituting 5 and 1% respectively. Tapping is done on Hugues pattern  however  the Spanish faces differ from French faces being 12 cm. wide  3.4 m. high (final height in 5 years) and 1.5 cm. deep. A new method called  Spanish narrow face   was recommended for stands to be tapped for 20 to 25 years. In this system 5 narrow faces  2.2 cm. wide  2.2 cm. apart and 1 cm. deep  are started near the base of the tree and worked upwards giving 19.8 cm. combined width of face  i.e.  11 cm. width of actual tapping surface and total 8.8 cm. untapped space leftover between 1st to 5th blazes. The method is reported to be better than standard faces used in Spain  as it results in rapid healing of faces  8 to 10% greater oleoresin yield and easier to work. However it takes longer time in freshening. Trials are also being carried out to tap Spanish pines employing herringbone (Mazek) system  with or without chemical stimulation  and American bark chipping method with acid stimulation

Greek Method

In Greece P. halepensis and P. halepensis var. brutia are tapped for oleoresin. Tapping schedules follow Hugues pattern  but the standard Greek face is about 31 cm. long (annual height) and 11.5 to 12.5 cm. wide; freshening of blaze is done at 7 day intervals. Narrow face of about 4 to 7 cm. (Angistri Islands) or 7 to 10 cm. (Sofika) are also employed for long term tapping of stands where regeneration is slow.

 

Hydrogenless Hydrogenation of Resin Acids

Hydrogenation of resin acids at low pressure with palladium on carbon or platinum oxide catalysts has been reported to yield dihydro compounds rapidly  with the formation of tetrahydro compounds requiring more rigorous conditions. Reduction with lithium in liquid ammonia has also been reported; the major products are different from those of catalytic hydrogenation  as expected. Homogeneous hydrogenation of the abietic type  acids using tristriphenylphosphinerhodium chloride as the catalyst was not successful  but the pimaric  and isopimaric type resin acids were partially hydrogenated to the dihydro compounds.

Under very mild conditions and in the presence of stoichiometric amounts of water and a palladium on carbon catalyst  alkali metal formates have been reported to be effective hydrogen donors.

This method has been used to successfully hydrogenate soybean oil methyl esters. We herein report that resin acids can be hydrogenated using this method at ambient condition to form the dihydro derivatives

Experimental

The resin acid methyl ester (0.1 mmol) was dissolved in 0.3 ml solvent in a 3 ml screwcap reaction vial. Appropriate amounts of deionized water and sodium formate (99%) were then added following conditions used for the transfer hydrogenation of soybean oil methyl esters5. The reaction vial was placed in a vortex test tube mixer to ensure mixing of all the components before adding 5 mg of 10% palladium on carbon catalyst. The instant of palladium addition was used as the zero reaction time. The temperature rose slowly from ambient to 33°C 34°C over the course of the reactions. Aliquots (2 to 3 µl) were withdrawn periodically  diluted with Me t Bu ether  and analyzed with an Hewlett Packard 5880 gas chromatograph (FID)  using a 14 m  thin film. DB1 column at 190°C and a 30 m BDS column at 190°C. Components of the reaction products were identified by their relative retention characteristics.

For the reactions at controlled temperatures and at 5x scale. vortex mixing was replaced by magnetic stirring.

The influence of variables on the reactivity of the transfer hydrogenation was determined by comparing of the initial reaction rate (ro  initial slope of the molar fraction) as a function of time.

Results and Discussion

Resin acids were used as the methyl esters to facilitate direct monitoring of the product composition by gas chromatography (GC) during the course of the reaction. Because the reaction is heterogeneous  an efficient stirring method was needed for the small solution volumes used in most of this study  a vortex mixer was found to be more efficient than ultrasonic mixing. In scaling up the reactions  however  mixing could be accomplished with a magnetic stirrer.

Methyl isopimarate  which has an exocyc1ic double bond  was chosen as the substrate for determining optimum reaction conditions because it reacted quickly and the expected hydrogenation products are well resolved in GC analysis. Using an amount of catalyst so that Pd > 0.4% and toluene as the solvent  the effect of the proportion of water and sodium formate was determined. Like Arkad et al. we found that 3 mol of water per mole of sodium formate gives the most efficient reaction  whether using toluene or a more polar solvent (50% toluene Me t Bu ether) (Figure 1). Accordingly  all further reactions were carried out with this water content. Sodium formate is most efficient when used in a ratio of 2 mol per mole of resin acid methyl ester  which also agrees with the results of Arkad et al.

Transfer Hydrogenation of Isopimaric/Pimaric Acids. Under the conditions described and using toluene as the solvent  methyl dihydroisopimarate was the only reaction product from methyl isopimarate. Attempts to drive the reaction by increasing the acidity of the system (2 1 formic acid Na formate) were not successful. Contrary to expectations  not only were tetrahydroisopimarates not formed  but the reaction rate slowed considerably  probably because the solubility of formic acid in water effectively made some water unavailable. Solvent polarity was then increased with a water insoluble solvent  Me t Bu ether (Figure 2). Although a slight increase in polarity had a negative effect on the reaction rate  about 1 1 toluene Me t Bu ether provided the best reaction conditions. The conversion of methyl isopimarate to dihydroisopimarate as the only product was complete in about 1.5 h. Reaction at the ring double bond occurred to a very small extent even after 40 h (about 5% methyl 18 isopimaranoate was formed). However  20% of methyl dihydroisopimarate was isomerized during this 40 hour period to a mixture of methyl 8(14) isopimaren 18 oate and methyl 8 isopimaren 18 oate.

Because ultrasonic waves have been reported to accelerate many heterogeneous reactions  we tried the isopimarate transfer hydrogenation under the most efficient reaction conditions and ultrasonic mixing. The reaction was approximately 6 times slower than the reaction with mechanical stirring. This was probably a result of the deleterious effect of ultrasound on ion exchange kinetics.

The conditions found to be most efficient for isopimarate hydrogenation transfer were then applied to methyl pimarate and methyl sandaracopimarate. These esters reacted slower than isopimarate  but pimarate reacted unexpectedly faster than sandaracopimarate (Table I). Whereas isopimarate followed a zero order reaction path up to 95% conversion  transfer hydrogenation of sandaracopimarate and pimarate deviated from a straight line reaction path earlier in the conversion.

Transfer Hydrogenation of Abietic Acids. The best reaction conditions for hydrogen transfer for the abietic type methyl esters were not the same as those found for methyl isopimarate. Both the polarity of solvent and the formate  resin acid ester ratios were different. Optimum conditions were 4 mol of sodium formate per mole of resinate with a solvent composition of 3  I toluene  Me t Bu ether. The water  sodium formate ratio was maintained at 3  1. As with isopimaric  and pimaric type methyl esters  only one double bond was hydrogenated for all four abietic type esters as in disproportionation of rosin over Pd/C.II the reaction was complete in 5 to 6 h.

For methyl abietate transfer hydrogenation  the major reaction products were 13b abiet 8(14) en 18 oate (64%) and 13b abiet 7 en 18 oate (25%) (Table II). This is consistent with the results of platinum oxide reduction of 12 hydroxyabietic acid  in which the proportion of the 13 b 8 (14) en isomer to the 13b 7 en isomer was nearly 3 Only very small amounts of the 13 a isomers were formed.

Although methyl neoabietate hydrogenates faster than abietate  the initial rate of formation of the dihydro compounds is practically the same; some isomerization to methyl abietate (maximum about 25%) and a slight dehydrogenation to methyl dehydroabietate occur. The reaction product distribution is essentially the same as for abietate; only trace amounts of 13(15) abietenoate are produced.

For methyl levopimarate the side reactions of isomerization and dehydrogenation are more prevalent (Figure 3). They do not occur if either catalyst sodium formate  or water are absent  which suggests that a catalyst water/formate complex is involved. Although a change in solvent polarity or in temperature does not affect selectivity in the formation of specific dihydro compounds  it does affect the extent of dehydrogenation 21% of dehydroabietate is formed in toluene  13.5% in 1 1 toluene Me t Bu ether  and 20% at O°C (45% at 80°C) in 3 1 toluene Me t Bu ether. Although the reaction is much faster in 3  I toluene Me t Bu ether at 80°C (Ea = II kcal/mol)  the yield in hydrogenated products is much lower. The optimum temperature is about 20°C. Reducing the amount of catalyst  decreased the reaction rate  which is in agreement with the results of Arkad et al for soybean oil methyl esters. The amount of catalyst had no significant influence on the selectivity of the dihydro compounds but the proportion of dehydroabietate increased slightly with increasing amounts of catalyst.

The major hydrogenation products of methyl palustrate are the 8 abieten isomers. Isomerization of palustrate to abietate (maximum about 4%) and dehydrogenation occur to a very small degree compared with that of levopimarate. Because the hydrogenation products have a similar distribution for all abietic type esters except methyl palustrate  the reaction mechanism for palustrate may be different.

 

Terpene Resins

Pale amber  transparent  thermoplastic polyterpene hydrocarbon resins  of the type formula (C10H16)n  have been produced and sold on a commerical scale since 1938. These resins are characterized by ring and ball softening points (S.P.) ranging up to about 135º C.; they are soluble in a great variety of organic solvents  including hydrocarbon solvents and are of good color stability. They are used  in conjunction with other materials  in the formulation of a wide variety of end products  including adhesives  adhesive tapes  rubber goods  and coating compositions. Depending on the nature of the end use  the terpene resins are supplied either in solid form or in solution in hydrocarbon solvents; the solid forms are made in a wide range of softening points or molecular weights.

These polyterpene resins are derived primarily from the catalytic polymerization  in solution  of the bicyclic monoterpene pinene  C10H16  principally the b isomer (nopinene)  and may be regarded as essentially polymers from b pinene. The pinene in turn is derived from gum and sulfate turpentines  from both of which it is recovered by fractional distillaton.

This article is concerned only with these hydrocarbon resins  and does not cover other terpene derived resinous substances  such as rosins (q.v.) and the terpene phenol resins. The latter are produced by reacting terpene hydrocarbons or alcohols with phenol in the presence of acid catalysts  followed by catalytic resinification of the resulting substituted phenol with a reactive substance such as formaldehyde. Such terpene modified phenolic resins exhibit among other properties increased solubility in drying oils. They are useful in adhesives and in various types of coatings  including particularly wax emulsions  varnishes  paints  and heat setting printing inks. Certain resins are also antioxidants for rubber.

Physical Properties

The commerically available polyterpene resins are produced with a variety of softening points (measured by the A.S.T.M. ring and ball method E28 51T)  ranging from + 10 to + 135ºC.  corresponding to a range from viscous liquid to hard  brittle solid polymers at ordinary temperatures. The average molecular weights of these polymers increase as the softening points increase. A molecular weight of about 1200 to 1250  measured cryoscopically in benzene  is characteristic for a polymer of 125 to 135º C. softening point. In common with polymers generally  the polyterpenses are mixtures of polymers of various molecular weights and chain lengths. A characteristic molecular weight distribution obtained by fractionation for a commercial 135ºC. softening point polyterpene resin is shown in Table 1. The fractionation was accomplished by partial precipitation from amyl alcohol  the general procedure involving solution of the resin in hot amyl alcohol  followed by cooling  decanting the amyl alcohol solution from the precipitated higher molecular weight polymers  and steam distillation of the decanted solution to remove the alcohol. Fractions 1 0 were so obtained  increasing amounts of amyl alcohol being required for the successive fractions because of the decreased solubility associated with increased molecular weight.

These polymers are typically thermoplastic  and merely soften or harden as they are beated or cooled  no irreversible change occurring as long as the heating temperature is kept below that at which pyrolytic reactions set in. In common with other amorphous hydrocarbon resins  these polymers show no sharply defined liquefaction or solidification temperatures  and their softening points are therefore measured by arbitrary standard test methods.

The polymers are slightly less dense than water  resulting in a relatively high bulking value compared to other polymeric materials. Values for the specific gravity of these resins range between about 0.97 and 1.00  depending on the softening point or molecular weight  the exact composition of the monomeric terpene mixture polymerized  and the method of production.

The resins exhibit solubility in  or compatibility with  a wide range of materials. Complete miscibility exists with liquid paraffinic  naphthenic  and aromatic hydrocarbons  chlorinated hydrocarbons  higher alcohols  higher ketones  esters  and drying oils. Compatibility is exhibited with rosin  ester gum  waxes  including paraffin wax  polyisobutylenes  petroleum residues and pitches  mineral oils  and certain types of petroleum hydrocarbon polymers. Under appropriate conditions  compatibility is exhibited with rubber and modified rubbers  including synthetic rubbers such as GR S. Compatibility with cellulose ethers and esters is  however  quite limited.

Inasmuch as these resins are entirely hydrocarbon in nature they are moisture resistant and possess good dielectric properties.

Chemical Properties

As essentially pinene polymers  principally polymers from b pinene  the terpene resins exhibit properties typical of polymeric hydrocarbons including chemical inertness. They are inert to dilute mineral acids  alkalies  and salt solutions  and are characterized by acid numbers and saponification numbers less than four and approaching zero. Similarly they are resistant to heat over a wide range of temperatures  varying only in fluidity with temperature.

The detailed chemical structure of the terpene resins cannot be regarded as satisfactorily elucidated. Published data in the chemical literature and patented art have indicated these polymers to be susceptible to both halogenation and catalytic hydrogenation  and to reaction with ozone to give polymeric ozonides. For example  the reported weight of hydrogen absorbed by a catalytic polymer made from b pinene was 1.2%. This is equivalent to 0.82 mole of hydrogen per C10H16 recurring unit in the polymer chain. Based in part on these considerations  and in part on physical properties  Roberts and Day speculated that the catalytic polymerizaton of b pinene involved more than a simple chain addition reaction of monomer molecules and that isomerization occurred during the polymerization to give a polymer comprising a chain of recurring monocyclic C10H16 terpene units each containing a carbon double bond. Powers has also suggested the recurring unit of polymers pinene to be monocyclic and unsaturated  proposing a formula different in detail and in point of linkage.

More recent studies of these polymers by infrared spectrophotometric techniques have indicated that the polymers contain notably less unsaturation that would be required for a chain of recurring monocyclic terpene units but more than would be the case for a simple addition polymerization of b pinene molecules yielding a polymolecule containing only a single terminal double bond. Part  but not all of the unsaturation observed by infrared examination appears to represent terminal double bonds in the polymolecules inasmuch as it decreases with increasing molecular weight.

These observations imply that the pinene polymerization is  as postulated by Roberts and Day  more complex than simple addition  but that the final recurring unit structure is not solely monocyclic. Pending further elucidation it seems preferable toavoid the term poly b pinene  insofar as the latter may imply simple addition polymerization.

 

Terpene Based Adhesives

Introduction

Terpene resins are low molecular weight hydrocarbon polymers prepared by cationic polymerization of terpenes. These products  used by the adhesives  sealant  wax coating and investment casting industries  are separated into three major categories  pressure sensitive adhesives  hot melt adhesives and coatings  and elastomeric sealants. The pressure sensitive adhesives category includes solvent  emulsion  and hot melt pressure sensitive adhesives and rubber cements. The hot melt adhesives category includes hot melt adhesives  coatings  and investment waxes  while the elastomeric sealants category includes sealants  caulks and can end cements. Specific types of tackifying resins are required for each use.

Terpene resins are old  in fact  the oldest reference to polymerization was recorded in 1789 where in turpentine was treated with sulfuric acid. More modern milestones are a U.S. patent issued to Emile Rouxeville in 1909 for subjecting hydrocarbons such as turpentine to sulfuric acid to produce a resin and to resemble various Indian rubbers. Twenty four years later  aluminium chloride catalysis was patented for terpene polymerization  by the Gulf Refining Company. Later  in 1950  an excellent fundamental publication by Roberts and Day appeared in the chemical literature. Commercial terpene resins produced for adhesive applications resulted from modification of disclosed processes  catalysts and terpene feed stocks.

Chemistry

Commercial tackifying resins are prepared from the monoterpenes (Figure 1). Beta pinene  alpha pinene and dipentene (limonene) are derived from turpentine by fractional distillation. The supply of dipentene is augmented by by product linonene collected during processing citrus fruit to frozen concentrate.

Commercial beta pinene typically ranges from 72 95% purity. Beta pinene resins are prepared from the lower assay material and flavour fragrance chemicals from the higher. Dipentene and alpha pinene resins are generally prepared from 92 98% pure feedstreams. Smaller quantities of modified terpene resins are produced from mixed feeds of terpenes  phenols  and hydrocarbon monomers.

Beta pinene resins

Initiation

The effective catalyst for terpene polymerization is a complex protonic acid derived by the interaction of a Lewis acid  typically AICI3  and a cocatalyst or promoter such as adventitious water. The initiation step is completed when the  hot  proton produced attacks the exocyclic methylene group of a beta pinene monomer (Figure 2).

Propagation

The tertiary carbenium ion rearranges prior to its attack on another monomer  which begins the propagation step (Figure 3). The main repeating unit in a beta pinene resin is a ring having 1 4 disubstitution.

The resin can be visualized as a perfectly alternating copolymer of isobutylene and cyclohexene. Its chemistry can be explained on this basis.

Ozonolysis or peracid oxidation indicates and olefinic group per mer unit. Infrared analysis shows the expected gem di methyl group of the repeat unit and the single methyl of the end unit.

Termination

The overriding determinant of molecular weight is chain transfer. This limits molecular weight to the 1000 2000 unit range as determined earlier by Roberts & Day. Figure 4 depicts the rearrangement of the end mer through ring expansion to a (2 2 1) bicyclic system and loss of a proton to form a camphenic end group. The camphenic carbenium ion depicted in Figure 4 will be non propagative for steric reasons. Good analogy for this rearrangement mechanism to a non propagative camphenic end cited above is seen in the acid catalyzed Wagner Meerwein isomerization of alpha or beta pinene  which expands the four membered rings to the (2 2 1) bicyclo ring system (Figure 5). A second minor chain transfer step to aromatic solvent  also occurs during commercial manufacture. In this case  the growing end attacks the solvent with elimination of a proton to produce the end group shown in Figure 6.

Dipentene Resins

The initiation step is similar to that described previously for beta pinene resins. Propagation through the terminal methylene group would be predicted (Figure 7). However  the determination of olefin content by NMR  ozonlysis and perbenzoic acid oxidation indicates that only one half of the mer units have the expected unsaturation. The endocyclic or ring double bond is involved in the polymerization and is consumed in some manner. To explain these facts and elucidate the polymerization pathway  the structurally similar model compound 8  9 p menthene (Figure 8) was subjected to polymerization conditions.

Only dimer was obtained  therefore the presence of a double bond in the ring is required for a successful polymerization. Armed with this fact  me may theorise that the polymerisation of dipentene proceeds by initiation at the tri substituted olefinic ring position with the carbenium ion under going cyclic polymerization to yield a structural unit as shown in Figure 9.

Butler has shown that the polymerization of the related 1 methylene 4 vinylcyclohexane proceeds partially by cyclization (Figure 9). More likely  the terminal isopropyl carbenium ion attacks the residual double bond of the penultimate mer unit and thus forms a ring with subsequent polymerization proceeding from the penultimate mer unit.

A structural representation based on this postulation is presented in Figure 10. The dotted bonds are those formed during polymerization  the Arabic numerals indicate the sequence of bond formation  and the letters the dipentene mers. By invoking either of the above mechanisms  we can satisfactorily explain the presence of only one double bond per every two to three mer units. Further evidence of the polycyclic nature of the resin is the high density of the dipentene resins.

Alpha pinene resins

This monomer is the most difficult of the common terpenes to polymerize since it does not possess an exocyclic methylene group. Although alpha pinene easily forms the same initial carbenium ion as beta pinene (1)  the propagation step  Figure 11  is difficult for steric reasons. The presence of an adjuvant is required to eliminate the formation of large amounts of dimer which otherwise would form during the polymerization.

The presence of the adjuvant (also referred to as a synergist) is thought to stabilize the growing carbenium ion and thus give it a longer lifetime during which it can attack another alpha pinene monomer. Chain transfer to monomer is thus suppressed with its accompanying formation of dimer (Figure 12). The peracid oxidation of alpha pinene resin shows that approximately two thirds of the mer units contain an olefin indicating that in the remaining one third  the four membered ring probably expands and results in a saturated mer unit possessing the (2 2 1) bicyclic system. Accordingly  the two proposed mer structures (a) and (b) in an alpha pinene resin are illustrated in Figure 13.

Physical characteristics of resins

The number average molecular weights and molecular weight distributions of representative commercial terpene resins  determined by vapor pressure oxmometry and gel permeation chromatography  are presented in Table 1.

The molecular weight is the most important single property of a polyterpene resin. It may be correlated to physical properties and utility. When a polymer property is plotted versus molecular weight  there occurs a  leveling off  in the property at a particular molecular weight  which varies for each resin or polymer. In most instances it is necessary to attain this minimum molecular weight range to get the desired physical properties  e.g.  polypropylene has to have a molecular weight of 50 000 and acrylonitrile 35 000 to be useful in common polymer applications. By contrast  the relatively low molecular weights of terpene resins at which properties plateau  coupled with their narrow molecular weight distribution and excellent solubility in elastomers makes them unique and useful for adhesives.

An adhesive consisting of a high polymer and a low molecular weight tackifier takes advantage of the properties of each component. The high polymer contributes strength through entanglements of extremely long chains and rein forcement with secondary valence bonds  whereas terpene resins attain their utility from low molecular weight  rapid change in viscosity with temperature  Newtonian liquid behaviour and good solubility which provides high polymer segmental motion and wetting of substrates. It is recognized that the preferred tackifiers for pressure sensitive tapes are beta pinene resins having ring and ball softening points from 115ºC to 135ºC. This maximum utility appears on the bend or leveling off of the softening point molecular weight curve (Figure 14). At this bend  the beta pinene resins are transparent amber glasses. Recently  water white versions have been introduced.

Since initiation  propagation and chain transfer process are all proceeding simultaneously  we observe a distribution of molecular weights. This can be determined by gel permeation chromatography. During a typical batch polymerization  the molecular weight distribution was observed to change during the course of the monomer addition. This is not surprising in view of the multitude of physical changes that are occurring  e.g.  the heterogeneous to near homogenous catalysis  the increase in dilution. In order to better control the polymerization process  most commercial operations employ a continuous process where a steady state ration of initiation/propagation/chain transfer is present. (cf. Commercial Production).

For a specified softening point  dipentene and alphapinene resins have lower molecular weights than a betapinene resin indicating that the former polymer structures are more rigid and more compact than that of a beta resin. The density of dipentene resins is higher than that of beta resins  0.998 to 0.974  corroborating the presence of rigid fused ring moieties. Although dipentene resins have a higher softening point/mer unit  they have a smaller hydrodynamic volume and hence form solutions of low viscosity. The semi ladder structure is confirmed by greater thermal stability than betapinene resins. The density of alpha resins  at 0.976  is very close to that of beta resins; more importantly  the molecular weight and hydrodynamic volume are closer to those of dipentene resins that beta resins. For this reason  the bulk properties of alpha resins resemble those of dipentene resins with the exception of thermal stability. The thermal stability of alpha resins is poorer because of the partial steric interaction due to the 1 3 disubstitution of the cyclohexene ring and absence of any double stranded placements.

Pressure sensitive adhesives

A pressure sensitive adhesive is one which is permanently tacky  requires no activation by heat  solvent  or moisture  and which will adhere strongly to most surfaces upon application with a minimum of pressure. Tack is defined as instant low order adhesion developed by mere contact with a variety of dissimilar surfaces. The major components of a pressure sensitive formulation are elastomer and tackifier. The latter can be polyterpene  hydrocarbon or rosin ester based. The elastomers  generally rubbers  have molecular weights between 60 000 and 350 000  which correspond to degrees of polymerization of 1 000 to 5 000. Because of their extreme chain length  they provide the cohesive strength to formulation and  in addition  possess a latent tackiness. Their high molecular weights allow modification with large amounts of other substances without serious loss of cohesive strength. The terpene resins  because of their chemistry and physical characteristics  combine with the elastomer to produce formulations with the characteristics of tack  adhesion and cohesion required of a successful pressure sensitive adhesive.

The tackifying resin can be thought of as a solid solvent for the rubber elastomer. Usually  solubility is affected by molecular weight; the smaller the molecule  the higher the solubility. While low molecular weight in a tackifying resin is desirable  there is a practical limit to this feature. As molecular weight drops  semisolid resin is produced which imparts tack but adhesives formulated with such a resin then fail cohesively. Conversely  adhesives made with resins having a softening point beyond 135ºC lack in tack. Empirically  beta pinene resins of 115ºC softening point impart the best balance of adhesive properties.

The tackifying resin appears to operate by bringing out the smaller  tack bestowing molecules from their dispersion in the mass of the rubber. The solubility of the longest chains of a rubber is at best limited  so we can speculate that the tackifying resin exhibits a gradient solvent effect totally solubilising the shortest chains  partially solubilising those of intermediate large size. In the case of the longest elastomer chains  the tackifier probably operates by solubilizing segments  thereby allowing wetting of the substrate and adhesion.

 

Ozonolysis of Alpha Pinene

The discovery that the esters of pinic acid (2 2 dimethyl 3 carboxy cyclobutylacetic acid) have excellent lubricant and plasticizer properties has stimulated interest in this compound and in its precursor  pinonic acid (2 2 dimethyl 3 acetyleyclobutylacetic acid). The cost of producing these acids by permanganate oxidation of a pinene to pinonic acid and further oxidation to pinic acid with hypochlorite is expensive. On the other hand  an ozonolysis process might be developed which would be economically attractive. Harries and coworkers made a cursory investigation of the ozonolysis of a pinene and reported about 25% yields of a liquid pinonic acid. Subsequently Brus obtained low yields of solid optically active pionic acid by decomposition of an ozonide of a pinene. More recently  Spencer and coworkers have reported that vapor phase ozonization of a pinene yields an ozonide containing five atoms of oxygen which yields pinonic acid. They question the validity of Harries identification of pinonic acid.

Prior of the initiation of the research reported here  workers at the Naval Stores Station of the United States Department of Agriculture  Southern Utilization Research Branch  had verified the fact that pinonic acid is actually obtained by liquid phase ozonoloysis of a pinene using low concentrations (2%) of ozone and had increased the yield of pinonic acid to about 50%. This work consists of a broad screening program of the effect of a number of variables on the production of pinonic acid and pinic acid by the ozonolysis of a pinene in the liquid phase using concentrations of ozone up to

100%. The structural formulas of the principal compounds are

Effect of solvent  ozone concentration and temperature on yields were investigated

Solvent Screening. The data obtained from an evaluation of the effect of solvent are listed in Table 1. Except for those from experiments involving the use of acetic acid and carbon tetrachloride acetic acid as solvents  all data in Table 1 resulted from single experiments  unless otherwise indicated. The best of several experiments with each of five selected solvents  involving changes in concentration of ozone  ratio of ozone to pinene  and ozonization temperature  are listed in Table 1 with the footnote about multiple runs. In view of the apparent superiority of the carbon tetrachloride acetic acid solvent system  this system was investigated in some detail.

Ozone Concentration. The ozonization of a pinene in carbon tetrachloride acetic acid solvent was studied as a function of ozone concentration in order to ascertain the possible advantages of the use of high concentrations of ozone. The technical literature does not contain any references to the use of high concentrations of gaseous ozone in the controlled oxidation of organic compounds.

A series of ozonolyses was made with 7.5  15 and 100 mole % gaseous ozone during the ozonization phase  followed by a 0.5  hour reflux treatment. The data for these runs are presented in Table 2. The fact that the yields for all these runs are so nearly the same strongly suggests that the yield of desired products is independent of the concentration of gaseous ozone used.

Effect of Temperature. The effect of temperature on the ozonization of pinene in carbon tetrachloride acetic acid solvent was investigated. These data  comprising a part of Table 3 suggest that there is only a slight increase  if any  in the yield of pinonic acid caused by changing the temperature of ozonization from 25º to 5º or  40º C.

Carbon tetrachloride acetic acid solvent composition and ratio of pinene to ozone during ozonization do not substantially affect yields

The data acquired on the effects of solvent composition and the ratio of pinene to ozone on the ozonization of pinene in carbon tetrachloride acetic acid solvent is presented as part of Table 3. These data suggest that changes in these variables do not effect any pronounced changes in the yield of pinonic acid. It appears that slightly better yields are obtained when a large excess of ozone is used.

Post Ozonization Use of Dilute Ozone. An investigation was made of the post ozonization use of a very dilute ozone (1000 p.p.m.) in oxygen at the reflux temperature of the liquid phase  compared with simple refluxing. The data for these experiment are listed in Table 4.

In five of the six comparisons made between the use of simple refluxing and the use of 1000 p.p.m. ozone  the use of ozone slightly increased the yield of desired products. The results of three series of experiments  designed to test the effect of using dilute ozone over a long period of time  suggests that little or no increase in the yield of desired products is obtained by using 1000 p.p.m. ozone for more than 2 hours. The results of a single pair of experiments  designed to explore the advantages of using more concentrated ozone for post ozonization treatments  suggests that the use of 2000 p.p.m. ozone may be more beneficial than 1000 p.p.m. ozone.

Experimental conditions are discussed

Analysis for Products. An aliquot of the final ozonolysis system  stripped of solvent  was dissolved in chloroform and chromatographically analyzed by the method of Marvel and Rands. Department of Agriculture  Olustee  Fla.  and our own study of known mixtures of pinonic acid  terebic acid  and pinic acid. The percentage of butanol in chloroform for the three elution solvents used were 0  1  and 2  respectively. To each 10 ml. fraction eluted  15 m . of 95% ethanol was added prior to titration with standard alkali to the phenol red end point.

Ozonization with Dilute Ozone. Dilute ozone of known concentrations was prepared by vaporizing a known quantity of 100% liquid ozone in an evacuated reservoir of known volume and adding pure nitrogen or pure oxygen until 2 atmospheres pressure (absolute) was obtained. A given amount of the dilute ozone was then bled through a grooved stopcock and rotameter at 10 liters per hour through the reactor containing the solution of pinene. The reactor (for runs with an excess of pinene over ozone) was essentially a 28 × 200 mm. test tube with a short 45º side arm about 125 mm. above the bottom of the reactor  with a 24/40 standard taper joint permitting connection with a reflux condenser and exhaust gas tube. An 8 mm. outside diameter glass gas inlet tube was concentrically sealed to a male 24/20 standard taper joint  which fitted the top of the reactor tube. The gas inlet tube terminated about 15 mm. from the bottom of the reactor with a coarse fritted borosilicate glass pencil  12 mm. outside diameter  or a finely perforated endsealed glass tube.

During ozonization  the reactor was surrounded by 530 ml. of water (or other appropriate coolant)  held in a open widemouthed Dewar flask. The jacketing water was stirred intermittantly during the ozonization period and a temperature rise of approximately 4º C. was usually observed for each 0.95 gram of ozone passed into the reactor.

Ozonization with 100% Ozone. Liquid ozone and high concentrations of gaseous ozone are highly reactive with iron  brass  mercury  rubber  ordinary greases  and many organic and inorganic compounds. Glass  stainless steel  aluminum  concentrated sulfuric acid  and perhalogenated hydrocarbons are compatible with ozone. Ozone handling apparatus must be cleaned serupulously before using.

The apparatus for conducting ozonizations with 100% ozone is as follows  The liquid ozone tube is connected to one arm of an inverted U tube by a ball and socket joint. The shallow U tube is made of 1 mm. capillary tubing and is approximately 2 ft. long in the horizontal direction. The other arm of the U tube terminates in a male standard taper 24/40 joint concentrically ring sealed about the capillary tube which extends about 3 cm. beyond the joint. An outlet or exhaust tube  made of 0.5 mm. capillary tubing  extends from the upper side of the 24/20 joint about a centimeter below the ring seal. Standard round bottom flasks are attached to the 24/40 joint.

 

w Bromolongifolene

Abstract By analogy with w bromocamphene  w bromolongifolene on fusion with alkali  but at a comparatively higher temperature  gives several monomeric and dimeric products as a result of right enlargement. The monomeric products have been characterized as longihomocamphenilone (VIII) and longi isohomocamphenilone (IX). The dimeric products are composed of a mixture of longifolenyl ethers and the kinetic dimers. Lead tetraacetate oxidation of longifolene  according to the method of Ourisson  has been found to yield  not only longihomocamphenilone and longidione  but also a crystalline alcohol  identified as isolongifolol (XI).

Base induced ring enlargement of w bromocamphene was first studied by Lipp. He observed that potassium hydroxide fusion of w bromocamphene affords a six membered ring ketone and divinly ether as dimeric product. Later  Huckel also investigated these reaction products  but only recently Wolinsky after reinvestigation  characterized the constituents as I to V.

Longifolene (VI)  which in many reactions is similar to camphene  also forms w bromolongifolene (VII). Ourisson attempted alkaline fusion of the w bromo compound (VII) without success. A reinvestigation of the alkali fusion of w bromolongifolene has produced interesting results  which we wish to place on record.

During the initial alkali fusion of w bromolongifolene  using the method described by Wolinsky for w bromocamphene  the bromo compound was recovered unchanged. Considering the structure of longifolene and is general inertness  it was felt that the conditions for alkali fusion mentioned by Ourisson might not be applicable and hence certain modifications in the reaction were employed. After several attempts by varying the temperature of fusion  it was found that a temperature range of 380 to 400º is required. Instead of glass tubes  a stainless steel tube fitted with a long air condenser was found necessary for the drastic conditions employed.

As in the case of the camphene series  the fusion products were steam distilled and the distillate and the residue worked up separately.

Steam distilled products

By judicious application of GLC and TLC  the product was found to be a mixture of four components  the identification of which was carried out by employing both physical and chemical methods. Actual separation of these components was achieved by elution chromatography. Of the four  two were identified as longifolene and unreacted w bromolongifolene. The other two were found to be ketones (5 7% yield). IR spectra of these showed close similarity and indicated that both are six membered ring ketones with a  CH2 CO  linkage  but they are different as shown by GLC  TLC and NMR studies.

One of the ketones (IR spectra  Fig. 1; NMR spectra Fig. 3) agrees perfectly with the ring enlarged ketone longihomocamphenilone (VIII)  prepared by Ourisoon6 by lead tetraacetate oxidation of longifolene. On the basis of chemical and NMR spectral evidence he proved the structure as being VIII  the second ketone (obtained by us) must  therefore  have the structure IX and the name longi isohomocamphenilone (IR spectra Fig. 1; NMR spectra  Fig. 4) is proposed. In conformity with this  both these ketones give longidione (X) on treatment with selenium dioxide.

While preparing standard longihomocamphenione (VIII) for comparison purposes by lead tetraacetate oxidation of longifolene according to the procedure of Ourisson  together with longihomocampheilone (VIII) and longidione (X)  substantial amounts (5%) of another compound  an alcohol  which has been characterized as iso longifolol (XI) was isolated. Its identity was further confirmed by oxidation to iso longifolic acid (XII).

Residue

The reside from steam distillation of the alkaline fusion product was purified by repeated chromatography and distillation under diffusion pump vacuum and the purity examined by TLC using silica gel impregnated with silver nitrate.

The product was found to be mostly dilongifolenyl ether dimer (XIIIa and b)  since it has an absorption maximum at 6.05µ (1653 cm–1) which supports the presence of a vinyl ether  revealing that the alkaline fusion of VII predominantly produces a unique ring expansion. The ketone dimers (XIVa and b) which as in the camphene series  might also be present  could not be isolated. Although their presence is not supported by UV absorption  a positive indication comes from ozonolysis of the dimeric product  when both the ketones (VIII and IX) and the diketone (X) are produced. The presence of a divinly ether was established by chromic acid oxidation to furnish longihomocamphenilone (VIII)  longi isohomocamphenilone (IX)  longidione (X) and longiforic acid (XV).

All m.ps and b.ps are uncorrected. Rotations were taken in CHC13 solution. IR spectra were taken as liquid films for liquids and in nujol for solids on a Perkin Elmer Model 137B Infracord spectrophotometer by Ms. Gopinath and Deshpande. The NMR spectra were taken in CC14 solution using tetramethylisilane as internal standard on a Varian A 60 spectrometer by Dr. Nair and Mr. Mulla. GLC analyses were carried out on a Griffin George instrument on polyester column using H2 under press. as the carrier gas by Ms. Bapat and Sankpal  Anhydrous Na2SO4 was used for all drying purposes. Microanalyses were carried out by Mr. Pansare and colleagues.

w Bromolongifolene (VII). This was prepared according to the procedure of Ourisson with some modifications. To a mechanically stirred solution of longifolene (100 g) in dry ether (300 ml)  Br2 in dry ether (500 ml) was added at  10º during 3 hr and further kept at the same temp for ½hr. The mixture was then kept in a freeze for overnight. The ether was removed in vacuum at 20º  dimethylaniline (200 g  3 equivs) added and the mixture heated for 7hr at 180º. It was acidified with HCl aq (1 1)  extracted with ether  washed thoroughly with water until free of acid  dried  the ether removed and the residue fractionally distilled to yield pure (GLC  TLC) w bromolongifolene (43 45%)  b.p. 150º/6 mm  m.p. 40 41º. (Found  Br  27.94. C15H23Br requires  Br  28 02%).

Fusion of w bromolongifolene with potassium hydroxide. w Bromolongifolene (2 5 g) and KOH (6 15 g) were placed in a stainless steel tube (length 8   diameter 1 ) fitted with a long air condenser. The contents were heated on a sand bath and the temp slowly raised to and kept at 380 400º for 1½ hr. After cooling the tube the contents (dark brown) were poured into water. Several such fusions (from 90 g of VII) were combined together and steam distilled. The distillate and the residue were worked up separately.

Longihomocamphenilone (VIII) and longi isohomocam phenilone (IX). The steam distillate was extracted with ether  washed  dried and the ether removed. The residue (22.5g) was chromatographed on alumina (gr. 1  675 g) and eluted successively with pet. ether  benzene and ether.

Pet  ether eluate (15.5 g) was found to contain a mixture of longifolene and unreacted w bromolongifolene  which were separated by repeated chromatography and characterized by GLC  TLC. and IR analyses.

The earlier fractions of the benzene eluates and the later fractions of the ether eluates were rich in the ketones (IX and VIII) respectively. The intermediate fractions were a mixture of these two ketones. By careful and repeated chromatography of the appropriate fractions  these two ketones were obtained in the pure form (GLC and TLC) and were further purified by sublimation.

Longihomocamphenilone (VIII; yield 2 g). It had m.p. 55 57º  (a)D + (91.26º (c  7.15). (Found  C  82.04; H  10.64. C15H24O requires  C  81.76; H  10.98%). 2 4 DNP derivative  m.p. 144º  (Found  N  14 23. C21H28O4N4 requires  N  14.01%).

The same ketone prepared from longifolene by treatment with lead tetraacetate according to the method of Ourisson showed the same m.p. (55 57º) but a higher specific rotation (141.6º). The m.ps of the DNPs of our ketone (144º) and the Ourrison s ketone  as obtained by us (144 145º)  were also somewhat lower than observed by Ourrisson (156 158º). However  GLC and TLC behaviour and the IR and the NMR spectra of our ketone were identical with Ourrison s ketone  thus proving their identity. It may be possible that partial racemization has taken place during help temp alkali fusion  which will explain the lower optical rotation.

Long isohomocamphenilone (IX yield 2 g). It had m.p. 52.53º  (a) D + 64.13 (c  1.45). (Found   C  82.08; H  10.79. C15H24O requires  C  81.76; H  10.98%). 2 4 DNP derivative  m.p. 166º. (Found  N  14.45. C21H28O4O4 requires  N  14.01%).

Selenium dioxide oxidation of longihomocamphenilone (VIII) and longi isohomocamphenilone (IX) to longidione (X).A solution of SeO2 (150 mg) in a few drops water and acetic acid  (2 ml) was added to a solution of longi isohomocamphenilone (56 mg) in glacial acetic acid (2ml) at 80º and the mixture heated on a water bath for 24 hr. It was then diluted with water  extracted with ether  the ether extract washed with water  dried and the ether removed. The solid diketone was crystallized from pet. ether as fine yellow crystals; yield 50 mg  m.p. 93 94º  mixed m.p. with authentic sample undepressed  IR bands at  2960; 1730 and 1700 (doublet)  1497 and 1370 cm 1. (Found; C  77.05; H 9.61. C15H22O2 requires; C  76.88; H  9.46%).

The similar odixation of longihomocampheilone (VIII) gives the same product.

Dilongifolenyl ether (XIII a  b). The residue from steam distillation of the alkaline fusion products was extracted with ether  washed with water till neutral  dried and the ether removed to yield a viscous dark brown product (35g). It was chromatographed over alumina (Gr.II  1kg). On distillation it afforded a viscous  light yellow oil  b.p. 215º (bath)/1.54 × 10–2 mm; IR bands at  2941  1653  1449  1370  1205  1176  1156  1130  1093  1036  980  926  830  and 820 cm–1. (Found  C  85.92; H  11.18. C30H46O requires  C  85.24; H  10.97%).

Chromic acid oxidation of dilongifolenyl ether

The ether (2.5 g) and CrO3 (1.7 g) in acetic acid (18 ml) were heated on a water bath for 1 hr. Potassium carbonate (20g) was added to the green solution and the mixture steam distilled. The distillate was extracted with ether affording a yellowish oil (0.7 g)  shown to be a mixture of longihomocamphenilone  longi isohomocamphenilone and longidione by GLC and TLC analyses and further confirmed by actual isolation via chromatography over alumina.

The residue left after steam distillation of the product of chromic acid oxidation was made slightly acidic. The organic material was extracted with ether and divided by treatment with alkali into acidic and neutral portions. The former  which was composed of longiforic acid (XV)  was crystallized from ethyl acetate  m.p. 220 221º.

Ozonolysis of dilongifolenyl ether. A solution of the ether (1.14 g) in CCl4 (20 ml) was  ozonized at 0º for 4 hr. Carbon tetrachloride was removed under vacuum and the residual ozonide was heated with water (20 ml) for 2 hr extracted with ether. The ether extract was separated into acidic and neutral portions by treatment with KOH. There was very little acidic material. The neutral portion  a yellow oil (1 g)  was shown to be a mixture of longihomocamphenilone  longiisohomocamphenilone and longidione by GLC and TLC analyses and further confirmed by actual isolation via chromatography over alumina.

 

Peroxides from Turpentine

Excellent activity of pinane hydroperoxide as a catalyst for 5ºC.GR S polymerization was reported in the first article in this series. At that time attention was called to the fact that unusually high conversions and yields of the hydroperoxide can be obtained from pinane. This article discusses in greater detail methods of producing technical grades of pinane hydroperoxide from gum turpentine in good yields. The preparation and properties of pure cis l pinane 2 hydroperoxide have been described.

From gum turpentine or pinenes four steps are involved in producing technical grades of pinane hydroperoxide

Conversion of pinenes to pinane by hydrogenation

Purification of the pinane usually by distillation

Oxidation of purified pinane with molecular oxygen to give an oxidate having a peroxide content of about 50%

Stripping of the oxidate under vacuum to remove unoxidized pinane and leave the pinane hydroperoxide as the residue.

The product prepared on a 20 mole scale had a purity of 85 to 90% A conversion of at least 40% per pass and a yield  based on pinane not recovered  of 80 to 90% was obtained.

Peroxide number and degree of unsaturation are tests of product quality

Peroxide Number. The peroxide content of the various oxidates was determined by a slight modification of the iodometric method of Wheeler. The reaction time was 5 minutes and the results are expressed as peroxide number in milliequivalents per kilogram. The peroxide number of pure pinane hydroperoxide is 11 760.

Unsaturation. The quantitative hydrogenation method of Joshel and coworkers was used to determine unsaturation in the various products. The results are calculated in terms of moles of hydrogen absorbed per 136 gross of sample. For convenience  these values are referred to double bonds per mole in the case of turpentine and are converted to percentage of olefins in the case of crude pinanes.

Sulfuric Acid Test. For rapid control the purposes purity of freshly prepared pinane was estimated by shaking a portion with an equal volume of 85% sulfuric acid for 1 minute and examining the acid layer. Samples that give a cloudy acid layer or a straw color darker than 0.05N potassium dichromate solution will generally be unsatisfactory.

Catalytic hydrogenation of pinene to pinane is first step in hydroperoxide production

Pinane is prepared by catalytic hydrogenation of either a or b pinene. In the work reported in this article a commercial catalyst containing 16% nickel supported on filter aid and suspended in coconut oil was used. Both high pressure (20 to 100 atm.) and low pressure (15 to 30 pounds per square inch absolute) hydrogenations were made using this catalyst at a 1% nickel level and temperatures in the range of 60º to 150º C.

High Pressure Hydrogenation. In a representative high pressure hydrogenation  1275 grams of fresh gum turpentine  = 1.4715   = 12.60 (10 cm.  neat)   = 0.8618 containing an average of 1.03 double bonds per mole were charged to a 3 liter  rocker type autoclave. Commerical nickel hydrogenation catalyst (70 grams  14 grams of nickel) was added and the autoclave was closed  flushed with hydrogen  and charged with hydrogen at about 100 atm. The shaker was started and the autoclave was heated electrically to about 60º C. over a period of about 20 minutes by means of an electric furnace. At this point the hydrogenation  caught  and heat was cut off. The hydrogen pressure was permitted to drop to about 20 atm. and then recharged to about 100 atm. The temperature rose to 130ºC. during the next 40 minutes and about 0.9 mole of hydrogen was absorbed per mole of turpentine. The heater was then adjusted to maintain this temperature for about 4 hours to complete the hydrogenaton. Total hydrogen uptake was about 1 mole per mole of turpentine. Filtration after the reaction mixture was cooled yielded 1312 grams of crude pinane containing about 30 grams of coconut oil from the catalyst. Distillation of this product through a short Vigreaux column at atmospheric pressure yielded 1020 grams of pinane boiling below 170º C.  n20D = 1.46.5   = 0.8546   =   9.0 (10 cm.  neat)  which gave only a light yellow color when it was shaken with 85% sulfuric acid. This represents a yield of about 80% based on the gum turpentine charged.

The recovered catalyst was still fully active and was re used three times to produce yields of 88  89  and 87% of pinane. The low yield in the first run was due to the difficulty in removing the last of the pinane from the residual coconut oil.

Low Pressure Hydrogenation. Low pressure hydrogenations were carried out in stirred autoclaves designed for the hydrogenation of fats. The largest single charge was a 400 pound drum of gum turpentine. This hydrogenation was carried out at 22 pounds per square inch gage and 280º F. for 18.5 hours. At this time the run was stopped because of servere  leakage at the agitator shaft bearing caused by the action of hot turpentine on the packing. This hydrogenation was only 84% complete that is  quantitative hydrogenation indicated about 0.17 of a double bond remained per mole of terpene. The original gum turpentine had about 1.05 double bonds per mole  indicating the presence of 5% of monocyclic terpenes  which yield p menthane on hydrogenation. Small scale runs indicated that substantially complete hydrogenation of gum turpentine can be attained at 60 pounds per square inch and 150º C. when a suitable packing is used in the agitator shaft seal.

A portion (2400 grams) of this crude pinane was distilled through an efficient column at about 50 1 reflux ratio to give about 1500 ml. of pinane containing only about 1% of residual olefins.

Small and large scale techniques of piNane oxidation are investigated

Method A. Small samples (2 ml.) of pure pinane were oxidized with oxygen in 50 ml. Erlenmeyer flasks attached to gas burets. The reaction temperature was controlled by immersing the reactors in a constant temperature oil bath. The samples were not stirred. The progress of the reaction was followed by observing the volume of oxygen absorbed. At the conclusion of each experiment the peroxide content of the sample was determined.

Method A was used to study the effect of light on the oxidation of pinane. For runs in the dark  the reactors were completely covered with tin foil. A 200 watt incandescent light was used to illuminate the reactors for runs in the light. The results of these experiments are given in Table I.

Method B. Samples of pinane (0.1 mole) were oxidized in 125 ml. Erlenmeyer flasks immersed in a constant temperature oil bath. The samples were stirred by means of a glass encased magnetic stirring bar  and wet oxygen from calibrated gas reservoir was passed over the surface of the liquid at the rate of 1 liter per hour. The exit gas was passed through a Dean Stark trap and condenser to remove entrained vapors  and was then collected in a calibrated gasholder. Samples for use in determining peroxide number were withdrawn by interrupting the oxidation for a few seconds and using the oxygen inlet tube as a pipet to withdraw the sample.

Method B was used to investigate the effect of oxidation temperature on the peroxidation reaction. The results of these experiments are presented in Figure 1 and in Tables II and III. In calculating the data for Tables II and III  allowance was made for the moisture content of the oxygen for the removal of samples  and for the loss through the condenser by evaporation. Since such calculations involve a number of approximations  the results are only semiquantitative.

Method C. This method was the same as Method B except the reactor was simply connected to an oxygen reservoir and the oxidation was carried out in a closed system. In Table IV results obtained by this method are compared with those obtained by method B.

Method D. Oxidations were made using 100 ml. samples of pinane containing 1.4% of olefins in a 250 ml reactor with a fritted glass false bottom for introduction of oxygen and equipped with the usual moisture trap and condenser. A temperature of 110º C. was maintained by means of a constant temperature oil bath  and the oxidation time was 6 hours in each case. The crude oxidates were stripped at 0.3 mm. of mercury pressure to a pot temperature of 78ºC using water vapor as a carrier gas to remove unoxidized pinane. Oxygen absorption was not measured  but peroxide content was determined before and after stripping.

To evaluate the effect of iron on the peroxidation  duplicate runs were made with and without 1 gram of iron filings in the sample and iron turnings in the head space and trap. The runs with iron gave light yellow oxidates having peroxide numbers of 6200 and 6400. Stripping in the presence of iron gave a product having peroxide number of 10 600. The runs without iron gave similar oxidates having peroxide numbers of 5800 and 6600; the stripped product had a peroxide number of 10 800.

Method E. For larger scale runs (10 to 20 moles) using various grades of pinane  the reactor consisted of a 3  or 5 liter  three necked flask which was fitted with an efficient mechanical stirrer  a fritted glass gas inlet tube  a thermometer  and a modified Dean Stark moisture trap and reflux condenser. The reactor was heated with a heating mantle at the start of the oxidation and was cooled with an air blast or with a wet cloth during the latter stages of the reaction. The oxidation was initiated at 120º to 130º C.  and the temperature was lowered as the oxidation progressed. Samples were removed from time to time and the peroxide content was determined. Upon completion of the oxidation  the peroxide was concentrated by stripping off the unreacted pinane under vacuum  using water vapor as a carrier gas.

Oxygen flow rates of 200 to 400 liters per hour were used  depending on the size of the charge. Oxygen absorption was not measured directly  but in some experiments an efficient trap cooled with solid carbon dioxide was used to condense the volatile material from the exit gas. The amount of oxygen absorbed was then estimated from the total weight of products recovered. Results of experiments using this method are given in Tables V  VI  and VII.

The over all length of the reactor is about 1 meter. Neck A is fitted with a long stemmed glass thermoregulator. The simple regulator shown in Figure 2 is satisfactory and convenient for this purpose. It is readily set simply by opening the stopcock until the desired temperature is attained and then closing it. Necks B and C are used for insertion of a thermocouple well (or thermometer) and a sampling tube. Neck D is the gas outlet and is fitted with a Dean Stark moisture trap and reflux condenser.

The coolant maybe any suitable high boiling liquid  such as turpentine and is recirculated through a heat exchanger reservoir system by means of a centrifugal pump. The flow is controlled by means of a magnetic valve actuated through a relay by the thermoregulator. Heat for initiation of the reaction is provided by wrapping the reactor with electrical heating tape.

Oxygen input and exhaust were measured by means of wet test meters. Samples were withdrawn at suitable intervals for determination of peroxide content. Table VIII presents data for a typical run by this method.

Cold Rubber Polymerization. Samples of a crude pinane oxidate and a pinane hydroperoxide concentrate were tested by the Government Laboratories of the University of Akron for use in 5º C. copolymerization of butadiene styrene. For this evaluation in amine formula II (Formula A) and the low sugar iron formula (Formula B) previously reported and a sugar free formula (Formula C) were used. The sugar free formula was identical with the low sugar formula except for the omission of the sugar and part of the pyrophospate from the activator. All peroxides were tested simultaneously at a given level. Representative data from these tests are given in Table IX.

Decomposition of Pinane Hydroperoxide. The general technique used in this work consisted of weighing a sample of pinane hydroperoxide (Approximately 0.1 gram) into a small glass ampoule  adding the decomposing agent being tested  flushing the ampoule thoroughly with nitrogen  and sealing it. The sealed ampoules were immersed in a constant temperature bath and removed at suitable intervals  chilled  cleaned thoroughly  and opened. The sample was transferred to a flask by means of the peroxide number solvent and the peroxide content was determined. Decomposition conditions were chosen on the basis of work on the pure peroxide.

Results of these experiments are given in Tables X  XI  and XII.

Over all yield of 85% is realized in production of high purity hydroperoxide

Preparation of Pinane. Although gum turpentine was used as the starting material in the work reported  either a  or b pinene can be used. b pinene hydrogensters more readily than turpentine or a pinene and can be hydrogenated at a little lower temperature. When gum turpentine is used instead of pure pinenes  the product may contain up to 5% of p menthane and small amounts of other saturated terpenes  but these do not interfere in the oxidation step.

If the hydrogenation step is carried out properly  the product can be filtered  distilled to remove the last traces of the catalyst and the carrier  and used for the production of pinane hydroperoxide without further purification. If the hydrogenation step is not carried to completion  purification of the crude pinane may be necessary. As shown in Tables V and X  the presence of excessive amounts of residual olefins decreases the purity and stability of the product and the yield of hydroperoxide.

The residual olefins can be removed by efficient fractional distillation  by washing with concentrated sulfuric acid or with chromic acid sulfuric acid mixtures  by passage through activated silica gel  or by a combination of these processes. Obviously such methods are relatively time consuming and expensive. In some cases it has been found satisfactory to oxidize the impure pinane for a short time at 130º to 140º C. and recover the unoxidized pinane by simple distillation. The olefins are more easily  oxidized than the pinane. As a general rule it is much better to take adequate precautions to ensure complete hydrogenation than to have to remove residual olefins from the crude pinane. However  the hydrogenation conditions should be fairly mild since high temperatures favor the production of trans pinane  which is more resistant to oxidation than is cis pinane. Furthermore  vigorous hydrogenation conditions may convect the pinane to monocyclic hydrocarbons.

 

Sylvestrene and some of its Derivatives

With the discovery of  sylvestrene  in Swedish pine oil derived from Pinus sylvestris  probably the most intriguing chapter was opened in the chemistry of m menthadienes. We now know for certain that  sylvestrene  is not a naturally occurring hydrocarbon but an artifact originating from D3   or D4  carene during the process of isolation through the dihydrochloride. However  during the past one hundred years  the structures of sylvestrene and its derivatives were the subject of innumerable inconclusive investigations. In recent times there has been great interest in the  sylyestrene  problem and the purpose of this review is to focus attention on the salient developments in this field.

Sylvestrene

Structure  Usually  sylvestrene  is obtained from sylvestrene dihydrochloride (1) by splitting off two molecules of hydrogen chloride using aniline sodium acetate and acetic acid or diethylaniline. Theoretically six m menthadienes can arise by the dehydrochlorination process. However  by precise fractionation the hydrocarbon mixture has been resolved into the isomers designated as sylvestrene  isosylvestrene and sylveterpinolene with tentative formulae (II)  (III) and (IV) respectively. That formula (II) represents sylvestrene is firmly established by the n.m.r. analysis of syivestrene tetrabromide (V) which is obtainable only from sylvestrene. It was therefore  proposed that the name sylvestrene should be confined to the D6 8(9) m menthadiene which alone furnishes sylvestrene tetrabromide.

New method of preparation  Whereas the earlier methods of obtaining sylvestrene depended on the fractionation of the hydrocarbon mixture derived from sylvestrene dihydrochloride  recently it was prepared in about 47% yield by heating an ethanol ether solution of sylvestrene tetrabromide with zine dust. This sylvestrene afforded copiously the tetrabromide and nitrosochloride derivatives but did not respond to the acetic anhydride   sulphuric acid colour test.

Sylvestrene nitrosochloride

Wallach who was the first to prepare the bimolecular sylvestrene nitrosochloride  considered the monomeric form to be (VI)  (VII) or a mixture of the two on the assumption that sylvestrene was a mixture of (II) and (III). If this view is accepted  then the dimeric form is either (VIII)  (IX)  (X) or a mixture of these. In order to distinguish between these possible structures. the n.m.r. spectrum of the bimolecular nitrosochloride was studied. The results obtained favoured the formula (VIII) for the derivative  which in turn would suggest that the correct formula for the nomomer is (VI).

Sylvestrene oxide

The epoxidation of sylvestrene with peracetic acid at temperatures below 0º has resulted in about 70% yield of sylvestrene oxide (XI). It is a colourless mobile liquid with a camphor menthol smell. The physical constants for the camphor menthol smell. The physical constants for the purest sample are  b.p. 90º/20 mm  n29 1.4671  d20 0.9307 and (a) 20D + 54.1º. On hydration with dilute sulphuric acid it gave the crystalline diol (XII)  m.p. 135º. As will be seen in the sequel  sylvestrene oxide is a useful raw material for synthesis of oxygenated derivatives in the m menthane series.

 

Recovery of 3 carene from Chinese Turpentine and Synthesis of Acetylcarenes

Fractions containing 56~72% 3 carene were recovered by two stage fractional distillation of Chinese wood and sulfate turpentines. Acetylation with acetic anhydride using zinc chloride as catalyst produced a mixture of acetylated carenes with 4 acetyl 2 carene as the main product. The optimal condition for the acetylation was determined to be  reaction temperature 70ºC  reaction time 6h  amount of ZnC12 3.8% and the ratio acetic anhydride  3 carene 2.0 1

Introduction

The monoterpene 3 carene (3 7 7 trimethyldicyclo 4 1 0 3 hexene) is one of the major components in wood and sulfate turpentines produced in north China. Its content is about 10% in this turpentine. 3 Carene also occurs in essential oil  such as oil from needles and barks of arborvitae (Thuja species). 3 Carene has been used for the synthesis of perfumes and raw materials for perfumes  for example  4 acetyl 2  carene and 4 hydroxymethyl 3 carene. However  there is no report about the utilization of 3 carene in China. The aim of this study was to recover fractions rich in 3 carene from Chinese turpentines and to synthesize 4 acetyl 1 carene. The synthesis conditions were optimized and the reaction mechanisms were elucidated.

Distillation of wood and Sulfate Turpentines

Material and Methods

Turpentine samples Wood turpentine was obtained in March 1987 from the Dunhua wood Rosin Factory in Dunhua city  Jilin Province  China  using Korean pine (Pinus koraiensis). Sulfate turpentine was obtained in March 1987 from the Jiamusi Pulp and Paper Plant in Jiamusi city  Heilongjiang Province  China  using wood of the following species; 70% Dahurian larch (Larix dahurica) and 30% of a mixture of Korean pine (P. koraiensis)  Yeso spruce (Picea jezoensis)  Khingan fir (Abies nephrole pis).

Fractional distillation the turpentines were distilled using a silverplated glass column with a vacuum jacket. The distillation conditions were as follows

Distillation Results

After the first distillation a distillate rich in a pinene was obtained (Table 1). The yield of a pinene in the distillate was 82% of the amount in the wood turpentine and 74% in the case of sulfate turpentine. Practically all 3 carene was left in the residue.

The residues from the first distillation were subjected to a second distillation. Two fractions rich in 3 carene were recovered from the wood turpentine residue (Table 2). The total yield of 3 carene was 74% of that originally present in the wood turpentine.

The sulfate turpentine reside yielded a first fraction rich in b piene  containing 70% of the amount present in the crude sulfate turpentine  the second distillate was rich in 3 carene and contained 79% of the original amount in the crude turpentine.

It was thus possible through two fractional distillations to recover fractions containing 56~72% 3 carene with a recovery of 74~79% of the 3 carene present in the crude turpentine.

Synthesis of Acetyl Carene

Materials and Methods

Synthesis experiments were carried out with the two carene rich distillates from the wood turpentine and the carene rich one from the sulfate turpentine.

Carene rich distillate  acetic acid anhydride and anhydrous zinc chloride were placed in a three necked flask equipped with a stirrer  a thermometer  a reflux condenser and a calcium chloride drying tube. The mixture was kept at a certain temperature for a certain time under stirring. After the reaction  water was added and the organic phase was separated. The aqueous phase was extracted with three portions of diethyl ether. The ether solutions were combined with the organic phase  the solution was washed with sodium bicarbonate until free of acid  then dried by addition of sodium sulfate and the ether was removed. The residue was vacuum distilled and the fraction recovered in the range 118 ~120ºC at 1333.22Pa containing mainly acetylated carenes was collected.

The synthesis products were characterized by GC  GC 1R and GC MS. GC IR spectra were recorded with a Hewlett Packard 5890A GC coupled a PRGLIB FTS 60 FTIR instrument using a HP 5 fused silica capillary column. The GC MS instrument was a JEOL D300 with a SE 30 fused silica capillary column. EI spectra were recorded at 70 eV.

Results and Discussion

The yield of products is dependent on the type and the amount of catalyst  the reaction temperature  the reaction time and the ratio of reactants. Each factor was investigated and orthogonal experiments were carried out in order to establish the optimal conditions for the reaction.

Effect of catalyst Tin tetrachloride (SnC14) and zinc chloride (ZnC12) gave rather similar catalytic effects. Zinc chloride was preferred because it is less costly. The optimal amount of zinc chloride is around 3.8%(Table 3). With higher amounts  polymerization of 3 carene seems to take place. With lower amounts  the reaction is considerably slowed down.

Effect of temperature. The yield of acetylated products decreased considerably with increasing reaction temperature  probably because of polymerization reactions (Table 4).

Determination of the optimal reaction conditions. According to the above results and earlier reports  we decided to study the four factors  reaction temperature  reaction time  amount of catalyst  ratio of 3 carene and acetic anhydride in an orthogonal experiment utilizing three levels and nine experiments  coded L9 (34)  (Table 5  6).

 

The average yield for every level of each factor was calculated. Because the yields of products were nearly the same when the added amounts of catalyst were 2.1% and 3.8% (C1 and C2)  the experiments of group A2B1C1D3 and A2B1C2D3 were repeated  and compared with the highest yield of Table 6.

Under A2B1C2D3 conditions  the yield of products was the highest and identical to the conditions and results of No.4 experiment (Table 7). So the optimal conditions were  reaction temperature 70ºC  reaction time 6h  added amount of catalyst 3.8%  acetic acid anhydride 3 carene 2.0 1. Under these conditions  the yield of products was 74~75%.

 

Homopolymers and Copolymers of Acrylates

Introduction

In continuation of the studies on the preparation of polymers containing terpenes and various terpene derivatives  two new derivatives from a pinine have been investigated  (1) homoterpenylmethyl carbinol  6 hydroxy 2  (1 hydroxy 1 methylethyl) heptanoic acid g lactone (I)  and (2) a campholenol  2 (2 2 3 trimethyl 3cyclopentenyl) ethylalcohol (II). I was prepared by Howell and Hedrick by the platinum oxide reduction of homoterpenylmethyl ketone in sodium hydroxide solution; H was obtained by reduction of the corresponding aldehyde  a campholene aldehyde. The properties and reactions of II and a campholene aldehyde have been deseribed. Synthesis of various esters of II  conversion of the esters to epoxides  and evaluation of the epoxides as plasticizer stabilizers for poly (vinyl chloride) have also been described.

The work here describes the preparation and polymerization of the acrylates and methacrylates of I and II. In addition  studies on the epoxidation  curing  and hydrolysis of some of the polymers of II were conducted. Polymers containing the unit I would be expected to undergo the lactone ring opening to yield water soluble polymers. Polymers of II would be expected to undergo an epoxidation readily. The reaction products of epoxidized polymers with  for example  fatty acids could find applications in the coatings field.

Results and Discussion

Monomers

Samples of a campholene aldehyde  I and II  were provided by Dr. G.W. Hedrick of the Naval Stores Laboratory of the Southern Utilization Research and Development Divisions  Agricultural Research Service. In the preparation of additional II  a campholene aldehyde was reduced with lithium aluminum hydride. The physical constants of the three materials are given in Table 1.

The acrylates and methacrylates of II and I were prepared according to the procedure of Marvel and Schwen. However  instead of distilling the products  chromatography on silicic acid with diethyl ether hexane mixtures as eluent was used for purification of the monomers. Physical characteristics of the monomers and their analytical data are given in Table 2. Infrared analysis showed the presence of a trace of hydroxyl containing material in the acrylate and methacrylate of I. Although there was a good agreement in analytical data between the calculated and experimental values  it is possible that a minor amount of the hydrolyzed lactone was still present in the derivatives of I or the hydroxyl band may have been due to absorbed moisture. The residue found in the analysis of the methacrylate of II was probably due to colloidal silicic acid introduced inadvertently during the chromatography of the monomer.

Homopolymerization

The experimental conditions and polymerization results for the various polymers are given in Table 3.

Hompolymerizations were conducted in an emulsion system with the use of a detergent (Siponate DS 10) rather than soap as the emulsifier. The detergent gave better latices and conversions. The low inherent viscosities for the homopolymers of methacrylate of I and acrylate of II were unexpected. The polymers were isolated as white powders  which could be molded (at about 150ºC) into water clear  brittle films. On one occasion the acrylate of I gave a material  which could be molded into a strong film. In the homopolymerization of the acrylate of II  whenever the conversion exceeded 35%  some insoluble polymer began to form. Similarly  long drying periods insolubilized the material  probably by oxidative coupling at the allylic position. The polyacrylates of I were soluble in ethyl methyl ketone and chloroform. The polyacrylates of II were soluble in tetrahydrofuran  ethylmethyl ketone  and methylene chloride. Whereas only a trace of a hydroxyl containing material was indicated in the acrylate and methacrylate of I monomers the corresponding homopolymers appeared to contain more of the hydroxy acid despite the fact that their analytical data agreed with the calculated. A tightly bound water of hydration cannot be ruled out  as the infrared analysis is not conclusive on this point.

Copolymerization

Copolymers of the acrylate of I. The acrylate of I was copolymerized with the acrylate and methacrylate of II  and with acrylonitrile. The acrylate copolymers were isolated as white  hard solids  soluble in ethyl methyl ketone  whereas the acrylonitrile copolymer was a yellow solid  soluble in N methylphrrolidone. The acrylate copolymers had inherent viscosities below 1.0; acrylonitrile copolymer had the exceptionally high viscosity of 4.4. The acrylates could be molded (at about 150ºC.) into water clear  brittle films  whereas the acrylonitrile copolymer gave an extremely tough  somewhat soft film.

The properties of all the copolymer films are given in Table 4. All of the copolymers gave transparent films.

Prolonged drying of the copolymers of the acrylate and methacrylate of II insolubilized them. In genera  the copolymers of acrylate of I exhibited adhesion to a copper foil in varying degrees. This may have been due to the hydroxy acid component present in the polymers.

Copolymers of the methacrylate of I. The  methacrylate and acrylate copolymers were isolate as white  hard solids soluble in ethyl methyl ketone; the acrylonitrile copolymer was a yellow soild  soluble in N methylpyrrolidone. None of the methacrylate of I copolymers possessed adhesive properties.

Copolymers of the acrylate and methacrylate of II. The acrylate/acrylonitrile copolymer was isolated as a yellow solid in a 95% yield of which only 30% was soluble in N methylpyrrolidone. The insolubility was probably due to the corsslinking of the acrylate portion.

The methacrylate/acrylonitrile copolymer was isolated in a quantitative yield; however  only about 20% of it was soluble in N methylpyrrolidone.

The solution methacrylate/fumaronitrile copolymer was isolated as a dark tan solid  soluble in tetrahydrofuran.

Terpolymerization

Terpolymers of the acrylate of I. Two series of terpolymers involving the acrylate of I have been prepared. One of the series involved BD/AN comonomers. The terpolymers were isolated as water clear to white rubbery masses  which could be molded (at about 130ºC.) into clear tough films. Whereas the 30/61/9 acrylate BD/AN terpolymer was essentially insoluble in hot tetrahydrofuran and chloroform  only 10% of the 60/33/7 acrylate BD/AN terpolymer was not soluble and the 78/17/5 acrylate/BD/AN terpolymer was soluble in chloroform and tetrahydrofuran.

The other series involved BD/Sty comonomers. These materials again were isolated as water clear to white rubbery masses  which could be molded (at about 130ºC.) into clear  tough films. A film prepared on copper foil of the 80/14/6 acrylate/BD/Sty terpolymer adhered strongly to the foil. Of the four compositions only the 80/14/6 and 66/24/10 acrylate/BD/Sty terpolymers were partially (~70%) soluble in hot ethyl methyl ketone.

Terpolymers of the acrylate of II. Another terpolymer series identical to the one described but with the acrylate of II was attempted. However  with both  the BD/AN and BD/Sty comonomers only low conversions were realized. The best yield (33%) was obtained with the 75/20/5 acrylate BD/AN terpolymer. The two terpolymers  75/20/5 and 58/34/8  on which inherent viscosities were run  were soluble in tetra hydrofuran and had good viscosity values. The films pressed (at about 130ºC.) from these materials were clear  rubbery  and strong.

Epoxidation

Epoxidation of several polymers was explored to increase their functionality. Development of adhesive properties was also sought. The following polymers were investigated  (1) polyacrylate of II  (2) 60/40 acrylate of I/acrylate of II copolymer  and (3) 66/24/10 acrylate of I/BD/Sty terpolymer. The in situ method11 with hydrogen peroxide/glacial acetic acid with a resin catalyst (Amerlite IR 120) was explored. This method was preferred over the ones involving use of preformed peracids because it gave higher oxirane oxygen content in a shorter time and less contamination in the final product. Ethyl methyl ketone was used as a solvent for the polymers. Normally  in epoxidations of polymers  secondary reactions products  such as glycol derivatives  ketones and ether derivatives  would be expected.

According to the infrared analysis of the epoxidized materials  only a trace amount of unsaturation was observed in the epoxidized homopolymer of acrylate of II and no unsaturation was detected in the other two materials. Furthermore  absorption bands attributed to epoxides (1250  840 cm. 1) were observed in the epoxidized polymers.

Analytical data  calculated on the basis of one oxygen atom addition across the double bond  indicated that for the polyacrylate of II only 10% of the theoretical addition had taken place  for the copolymer 38%  and for the terpolymer 25%. A more accurate determination could be probably achieved by the ether HCI method.

Although the epoxidized copolymer was isolated as a soluble product from the reaction mixture  drying it at 39ºC. for 26 hr. insolubilized it completely.

In the epoxidation of the terpolyemr (66/24/10 acrylate of I/BD/Sty)  two products were produced in about equal amounts. One of the materials was water soluble  the other was water insoluble. The water soluble material was also insoluble in hot ethyl methyl ketone  was extremely tough  and a good film could not be molded. Hence an infrared spectrum could not be obtained. The water soluble material was pressed into a film; the infrared spectrum showed it to be the hydroxy acid and contained absorption bands characteristic of epoxides. Analytical data on the water soluble material could also be accounted for by assuming opening of the lactone ring. It is surprising that the lactone ring was opened under these acidic conditions.

Curing

Epoxypolybutadienes cured with polyamines or anhydrides are good adhesives to metallic substrates. Accordingly  the epoxidized polyacrylate of II and the acrylate of I/acrylate of II copolymer were mixed with p phenylenediamine  placed between copper foils  and compressed and heated at 160ºC. for 2 min. The film from the polyacrylate of II was extremely hard and completely nonadhesive; the copolymer film was partially adhesive.

Hydrolysis of Polymethacrylate of I

The lactone ring in polymers of I should be susceptible to basic hydrolysis. A sample of the methacrylate homopolymer was hydrolyzed with 3.5% ethanolic potassium hydroxide at room temperature. After a period of about 2 hr. the infrared spectrum showed that most of the lactone ring had been opened; the product was soluble in ethanol and water. In water the hydrolyzed polymer formed a light blue  very viscous solution. Evaporation of water yielded a transparent strong film. Infrared analysis on the film showed the presence of a strong absorption band for the carboxylate anion at 1565 and 1390 cm. 1 and only a minor absorption band at 1775 cm. 1  indicative of the lactone carbonyl. Thus the potassium hydroxide treated polymer is essentially all potassium salt of the polycarboxylate. The extremely facile opening of the lactone ring suggests an easy preparation of water soluble polymers.

 

Polymers and Copolymers of Vinyl Pinolate

Preparation of Vinyl Pinolate

The preparation of vinyl pinolate from pinolic acid has been described previously. More recent work has shown that the product formed from the reaction of pinolic acid vinyl acetate  and mercuric sulfate is probably an acetoxyacetal  which can be hydrolyzed at room temperature with mineral acid. Infrared absorption for a hydroxyl group was completely absent in the unhydrolyzed product. Hydrolysis  however  gave the expected vinyl pinolate.

Polymerization

Polymerization of vinly pinolate has been accomplished by free radical initiation in bulk  solution  suspension and emulsion systems. The conditions for polymerization and some properties of the samples of poly (vinyl pinolate) are summarized in Table I. Preparation of poly (vinyl pinolate) in suspension was unsuccessful until neutral buffered solution was substituted for distilled water in the polymerization recipe. In contrast  polymerization of vinyl pinolate in buffered and unbuffered emulsion systems produced the same results.

All the samples of poly (vinyl pinolate) are colorless  glasslike solids that melt between 70 and 105ºC. Except for sample 31 B which is poly (vinyl pinolate) prepared in emulsion  the samples are soluble in methanol  acetone  and tetrahydrofuran  slightly soluble in benzene and insoluble in petroluem ether. Sample 31 B is soluble in acetone and tetrahydrofuran until it is dried. Then it is insoluble in acetone  tetrahydrofuran and several other solvents.

Because poly (vinly pinolate) contains one hydroxyl group per repeating unit  reaction with a diisocyanate would be expected to produce a high degree of crosslinking. To prepare low molecular weight polymers that contain relatively fewer hydroxyl groups than poly (vinly pinolate) and might therefore be more suitable for extending with diisocyanates  vinyl pinolate was copolymerized in solution with vinyl acetate and vinyl chloride. Table II contains information concerning the preparation and properties of several vinyl pinolate vinyl acetate copolymers and Table III vinyl pinolate vinyl chloride copolymers. Transparent  colorless films can be cast from both vinyl pinolate vinyl chloride copolymers. Transparent  colorless films can be cast from both vinyl pinolate vinyl acetate and vinyl pinolate vinyl chloride copolymers  but the films are brittle indicating that the vinyl pinolate units do not produce any appreciable internal plasticization.

Vinyl pinolate was copolymerized with vinyl acetate and vinyl chloride in emulsion as well as in solution. The data resulting from the copolymerization experiments are compiled in Table IV.

Poly (vinyl acetate) and poly (vinyl chloride) prepared in emulsion are soluble in acetone and tetrahydrofuran and so are the copolymers of vinyl pinolate prepared in solution and listed in Tables II and III. In contrast  the copolymers of vinyl pinolate with vinyl acetate and vinyl chloride prepared in emulsion are soluble in acetone  and tetrahydrofuran only until they are dried at room temperature. Attempts to dissolve the dried co polymer in benzene  acetone  tetrahydrofuran  and dimethyl sulfoxide resulted in the slow softening and swelling of the copolymer. Apparently even small amounts of vinyl pinolate  as small as 0.5 mole % copolymerized in emulsion with vinyl acetate or vinyl chloride produce a marked decrease in the solution of the dried copolymer.

Vinyl pinolate fails to copolymerize with vinylidene chloride under the emulsion polymerization conditions. Under similar conditions  the relative reactivity ratios of vinylidene chloride (0.08) and the vinyl ester of a long chain fatty acid  e.g.  vinyl stearate (3.80)  were determined and are unfavorable for copolymerization.

Reaction of vinyl pinolate copolymers with Isocyanates

To learn something of the reactions of vinyl pinolate and its vinyl chloride and vinyl acetate copolymers with isocyanates  a method was used based upon spectral analyses. By determining infrared absorbancies of a stretching vibration arising from the isocyanate group at 4.5µ of solutions of vinyl pinolate and its copolymers reacted with toluene diisocyanate and phenyl isocyanate it was possible to estimate the decrease in isocyanate concentration caused by the reaction. The change in concentration as represented by change in absorbancy gave a convenient method for measuring reactivity. Poly (viny acetate) and poly (viny chloride) homopolymers exhibited little or no reaction with either isocyanate at 75ºC. (Table VI). One of the isocyanate groups of toluene diisocyanate was less reactive than the other group  since almost half the isocyanate was unreacted when equivalent quantities of vinyl pinolate and the isocyanate were reacted. Phenyl isocyanate reacted completely. Similar results were obtained with the vinyl acetate vinyl pinolate copolymer  123 A. Copolymers  44 2 and a mixture of 121 A 123 A  from which excess toluene diisocyanate was removed after reaction by precipitating and washing with hexane contained free isocyanate groups. With 0.1N solutions of the copolymers  based on vinyl pinolate content  the residual isocyanate content was 0.07N for the vinyl chloride copolymer and 0.064 for the vinyl acetate copolymer.

The results of a rate study involving reactions of the copolymers 44 2 and 123 A and phenyl isocyanate are tabulated in Table V. After about 6 hr.  the isocyanate concentration with both polymers was about 0.07N (calculated 0.07N) and did not change much after an additional 8 hr. heating.

Experimental

Preparation of Vinyl Pinolate

Pinolic acid  372 g. (2.0 moles)  freshly distilled vinyl acetate  2200 ml.  copper resinate  1.0 g.  and mercuric acetate  8.0 g.  were mixed in a 3 1 flask. Concentrated sulfuric acid  1.0 ml.  was added and agitation continued at 0 5ºC. until the pinolic acid was in solution. The batch was stored in a refrigerator (10ºC.) for two days. The sulfuric acid was neutralized with sodium acetate and the excess vinyl acetate and acetic acid distilled below 30ºC. The residue was dissolved in 1500 ml. ether and washed with vigorous agitation for 15 min. with three 500 ml. portions of 1.5N hydrochloric acid. The solution was washed at 10ºC. with cold water  cold 0.5N sodium carbonate and dried. The ether was removed and the product distilled bulb to bulb; b.p. 106ºC./1.0 mm.; 334 g.  81%. The crude ester was redistilled through a column packed with glass helices  b.p. 84ºC. /0.2 mm.  1.4656.

Polymerization of Vinyl Pinolate in Solution

A 250 ml.  three necked flask equipped with a spiral condenser  thermometer  magnetic stirring bar  and nitrogen inlet tube was charged with vinyl pinolate  azobisisobutyronitrile (2% of weight of the monomer)  and 150 ml. of A.R. grade benzene. The solution was stirred at reflux temperature under nitrogen for the desired number of hours. Then the benzene was removed by aspiration and the polymer was purified by repeatedly dissolving it in acetone and precipitating it in petroleum ether (35 75ºC.). Finally the polymer was dissolved in benzene and freezedried.

Polymerization of Vinyl Pinolate in Suspension

Into a 100 ml.  two necked flask fitted with a spiral condenser  magnetic stirring bar  and nitrogen inlet tube was placed 3.0 g. of vinyl pinolate  0.03 g. of Duponol C (du Pont s sodium lauryl sulfate)  0.3 g. of azobisisobutyronitrile  and 10 ml. of neutral buffered solution. The suspension was stirred under nitrogen at 60ºC. for 48 hr. The poly (vinyl pinolate)  which had coalesced into a single lump  was dissolved in acetone and precipitiated first in water and then in petroleum ether. Then the polymer was dried at 60ºC. in a vacuum oven at 20 mm. of mercury.

Polymerization of Vinyl Pinolate in Emulsion

A 2 oz.  screw capped bottle was charged with 0.3 g.  of Triton X 301 (Rohm and Haas  sodium alkylaryl polyether sulfate  20% aqueous disperision)  1.5 g. of vinyl pinolate  0.75ml of 25% aqueous potassium persulfate  and 3 ml. of distilled water. After the air had been flushed from the bottle with a stream of nitrogen the bottle was capped and tumbled in a water bath at 60ºC. for 48 hr. A sulfuric acid salt solution (5% H2SO4 saturated with salt) was used to break the emulsion. The poly (vinylpinolate) was washed with water and purified by the same procedure described for suspension polymerization. After it has been dried  the poly (vinyl pinolate) was insoluble in dimethylformamide  methanol  acetone  2 butanone  tetrahydrofuran  dioxane benzene  toluene  chloroform  and carbon tetrachloride.

Copolymerization of Vinyl Pinolate and Vinyl Acetate in Solution

The same procedure described for solution polymerization of vinyl pinolate was used with the exception that a calculated amount of freshly distilled vinyl acetate was added to the solution.

Copolymerization of Vinyl Pinolate and Vinyl Chloride in Solution

Polymerization bottles (110 ml.  Ace Glass T 1506) were charged with calculated amounts of vinyl pinolate  0.2 g. of azobisisobutyronitrile  40 ml. of A.R. grade benzene and then cooled in a Dry Ice acetone bath. Vinyl chloride was condensed in the bottles until slight excess was present. Went the excess vinyl chloride had been allowed to evaporate  the bottles were sealed with crown type bottle caps and tumbled in a water bath at 60ºC. for 48 hr. The copolymers were coagulated by pouring the benzene solutions into 400 ml. of methanol and purified by repeatedly dissolving them in tetrahydrofuran and precipitating them in rapidly agitated methanol. After the copolymers had been dried at room temperature for 48 hr. they could be dissolved easily in acetone and tetrahydrofuran but only with difficulty in benzene.

Copolymerization of Vinyl Pinolate and Vinyl Chloride in Emulsion

The calculated amounts of vinyl pinolate  40 ml. of oxygen freewater 3.0 g. of Triton X 301  and 4 ml. of 2.5% potassium persulfate solution were placed into 110  ml. polymerizaton bottles. While the bottles were being cooled in a Dry Ice acetone bath a slight excess of vinyl chloride was condensed into it. When the excess had been allowed to evaporate the bottles were capped and tumbled at 50ºC. for 72 hr. The copolymers were coagulated with 400 ml. of saturated salt solution and collected on filter paper. After being washed with water and then with methanol  the copolymers were repeatedly dissolved in tetrahydrofuran and precipitated in methanol. Finally  the copolymers were dried at room temperature for 48 hr. If the copolymers are overheated  on drying they become insoluble in acetone  tetrahydrofuran  dimethyl sulfoxide  dimethyl formamide  and benzene.

Reaction of Polymers with Isocyanates

Exploratory experiments were made to select a solvent and to determine a suitable temperature and time for running the reactions. Tetrahydrofuran was a good solvent for the polymer; however  the isocyanates  toluene diisocyanate (a mixture of 2 4 and 2 6 isomers in a 4 1 ratio) and phenyl isocyanate were not stable in this solvent at 75ºC. since this solvent did not affect the isocyanate adversely.

In instances indicated  the benzene was replaced with tetrahydrofuran for reasons of solubility. The benzene was removed in vacuo at room temperature and the residual polymer dissolved in the tetrahydrofuran. In other instances also  as indicated  the polymers crosslinked and became insoluble in the latter solvent.

The substances investigated are tabulated in Table VI.

Benzene solutions (0.1N with respect to vinyl pinolate) of each of the copolymers 123 A and 44 2 were made up containing 0.3N phenyl isocyanate. These were heated to 75ºC. for periods of 1  2  4  6  and 14 hr. After each heating period 1 ml. samples were removed and diluted with 2 ml. of tetrahydrofuran. The results are tabulated in Table V. The concentration of the hydroxyl and isocyanate initially in the diluted samples were about 0.03 and 0.1N  respectively.

In another experiment  benzene solutions containing 0.93 g. (0.1N) of a mixture of copolymers 121 A and 123 A in equal amounts  and 0.87 g. (1.0N) toluene diisocyanate diluted to 10 ml were heated to 75ºC for 2 hr. The polymers were precipitated by pouring into hexane  washed by decantation  redissolved and reprecipitated to remove excess isocyanate. The polymers were dissolved in tetrahydrofuran and diluted to 10 ml. The isocyanate concentrations after removal of excess isocyanate were 0.064N for the 121 A 123 A polymer mixture and 0.07N for the 44 2 polymer.

 

 

Homopolymerization of Hydronopyl Vinyl Ether

Discussion

The work reported in this paper was undertaken to determine the optimum conditions for polymerizing hydronopyl vinyl ether (Ia) and 2 hydronopoxyethyl vinyl ether (Ib) and to investigate the properties of the resulting polymers.

Samples of hydronoply vinyl ether (HVE) and 2 hydronopoxyethyl vinyl ether (HEVE) were provided by the Naval Stores Division of the Southern Utilization Research and Development Division of the Agricultural Research Service and were prepared by published methods. During the course of the investigation  the preparation of additional HEVE became necessary. Bissel reported a yield of 38% (based on sodium) for the preparation of HEVE. He allowed sodium to react with a large excess of hydronopol and then treated the resulting suspension with 2 chloroethyl vinyl ether. We have found that HEVE can be prepared in 93% yield (based on hydronopol) by mixing hydronopol and sodium hydride in an excess of 2 chloroethyl vinyl ether.

The polymerization of HVE and HEVE by initiation with free radical  cationic  and coordination catalysts was investigated. In accord with the report that most vinyl ethers do not polymerize well by free radical initiation  neither HVE nor HEVE polymerized appreciably by free radical initiation in bulk or emulsion systems.

Under the conditions studied  the order of effectiveness of cationic initiation of the polymerization of HVE is stannic chloride >boron fluoride etherate > titanium tetrachloride > vanadium oxychloride. Vanadium trichloride does not catalyze the polymerization of HVE. For polymerization of HEVE the order of effectiveness is boron fluoride etherate >>> stannic chloride. Titanium tetrachloride  vanadium oxychloride  and vanadium trichloride do not catalyze the polymerization.

Polymerization of HEVE by initiation with boron fluoride etherate at  78ºC. produces the highest conversion and molecular weight of any method investigated. The poly (HEVE) is a tough  slightly tacky rubber with a specific rotation of  =   20.1º. It is soluble in petroleum ether  benzene  toluene  carbon tetrachloride  and tetrahydrofuran but insoluble in methanol  acetone  and 2 butanone.

Okamura and Higashimura report that poly (isobutyl vinyl ether) can be separated into crystalline and noncrystalline fractions because the crystalline fraction is less soluble in 2 butanone. The insolubility of poly (HEVE) in 2 butanone may indicate the presence of some crystalline portions.

At best  coordination catalysts prepared by mixing triisobutylaluminum with titanium tetrachloride or vanadium oxychloride or vanadium trichloride produce poor yields of poly (HEVE). Poor results were also obtained when attempts were made to polymerize HVE with catalysts prepared by mixing triisobutylaluminum with vanadium oxychloride or vanadium trichloride. Conversely  catalyst prepared by mixing triisobutylaluminum and titanium tetrachloride in a mole ratio of 2.7 1 produces poly (HVE) in the highest conversion and with the highest molecular weight of any catalyst investigated by us.

The poly (HVE) prepared with triisobutylaluminum titanium tetrachloride catalyst is hard and brittle  but becomes rubbery at temperatures above 45ºC. It has a specific rotation of  =   26.2 and is soluble and insoluble in the same solvents as poly (HEVE). An x ray diffraction pattern indicates considerable crystallinity in this polymer.

Experimental

Materials

Hydronopyl vinyl ether (HVE)  b.p. 80 81ºC./2 mm.   1.4788;   2.3.8º (0.3882 g. in 25 ml. of benzene); 2 hydronopoxyethyl vinyl ether (HEVE)  b.p.. 87 88ºC./0.5 mm.   1.4760    18.1º (0.418 g. in 25 ml of benzene)  and hydronopol  b.p. 126 128ºC./10 mm.   1.488 were provided by the USDA Naval Stores Laboratory  Olustee  Florida. The vinyl ethers contained 0.2% of hydroquinone and were purified by the method described by Schildknecht  Zosc  and McKinley and passed through alumina (Merck s chromatographic grade) just before they were used. 2 Chloroethyl vinyl ether was obtained from Monomer Polymer Laboratories and distilled before use. Hexane (Phillips 99%) was reluxed over sulfuric acid  washed  dried with potassium carbonate  and distilled from over sodium. A dispersion of sodium hydride (50.6% by weight) in mineral oil was procured from Metal Hydrides  Inc. The boron fluoride etherate was obtained from Eastman Organic Chemicals  stannic chloride from Baker Chemical Company triisobutylaluminum from Texas Alkyls  titanium tetrachloride (99.5%) from Matheson  Coleman  and Bell  and vanadium trichloride and vanadium oxychloride from Anderson Chemical Company.

Preparation of 2 Hydronopoxyethyl Vinyl Ether

Into a 5 liter four necked flask fitted with a stirrer  reflux condenser that was protected with a calcium chloride drying tube  addition funnel  and nitrogen inlet tube were placed 321 g. (6.68 moles) of NaH in mineral oil (50.6% dispersion by weight) and 650 g. (6.1 moles) of 2 chloroethyl vinyl ether. While the mixture was stirred rapidly  460 g. (2.7 moles) of hydronopol was added over a period of 1 hr. Stirring was continued for 2 hr. at room temperature and for 48 hours at reflux temperature. The reaction mixture was allowed to cool to room temperature and 500 ml. of methanol followed by 1500 ml. of water was added slowly. Six 250 ml. portions of ether were used to extract the organic material. The portions were combined  washed with 500 ml. of water  and dried over anyhydrous magnesium sulfate. The ether and methanol were removed by distillation and the residue was distilled under reduced pressure through a 100 × 1 cm. spinning band column. A total of 580 g. (93% yield based on hydronopol) of 2 hydronopoxy ethyl vinyl ether  b.p. 109ºC./0.75 mm.   1.4730  was collected.

Polymerization of HVE and HEVE

Attempted free radical initiation in bulk. A 6 × 1 in. polymerization tube was charged with 2.0 g. of HVE and 0.02 g. of a  a  azodiisobutyronitrile. To purge the reaction mixture of oxygen the pressure in the tube was reduced to 0.1 mm. Hg with a vacuum pump  and then nitrogen was admitted to the tube. Then the pressure was reduced to 0.1 mm. Hg and the tube was sealed and heated in an oil bath at 65ºC. At the end of 40 hr. the contents of the tube was a thin liquid that was completely soluble in methanol. Similar results were obtained when 2.0 g. of HEVE was substituted for HVE.

Attempted free radical initiation in emulsion. Into a 2 oz. screwtopped bottle were placed 0.2 g. of Triton X 301 (a 20% aqueous dispersion of Rohm and Haas sodium alkylarly polyether sulfate)  1.0 g of HVE  5 ml. of distilled water  and 0.5 ml. of 2.5% potassium persulfate solution. The bottle was flushed with nitrogen  capped  and tumbled in a water bath at 55ºC. for 36 hr. After the emulsion had been broken with saturated sodium chloride solution  two layers formed. The organic layer was a free flowing liquid completely soluble in methanol. The same results were obtained when 2.0 g. of HEVE was substituted for HVE.

Initiation with boron fluoride etherate. A method similar to the one reported by Sorenson and Campbell6 was used. A 250 ml.  three necked flask was fitted with a stirrer  nitrogen inlet tube  and rubber  serum bottle cap and charged with 10 g. of vinyl ether in 40 ml.of n hexane. While the solution was kept under a nitrogen atmosphere and stirred  it was cooled in Dry Ice acetone to  78ºC. A hypodermic needle was inserted through the serum cap and four drops of boron fluoride etherate were added to the solution. After 30 min. another four drops were added and the mixture was stirred for the desired length of time. A 10 ml. portion of methanol was poured into the reaction mixture  which was allowed to warm to room temperature. The resulting solution was poured into 800ml. of methanol that was being rapidly stirred. The polymer that precipitated was removed from the supernatant liquid. Further purification of the polymer was effected by dissolving it in benzene and repeating the precipitation step. Finally the polymer was dissolved in 200 ml. of benzene. The solution was filtered and the polymer isolated by freeze drying. Inherent viscosities were calculated from flow times of the benzene solution taken at 30ºC. in a number 50 Cannon Fenske viscometer. Data for polymerization of HVE and HEVE are collected in Tables I and II.

Initiation with boron fluoride etherate (Flash polymerization). Into a 250 ml.  four necked flask fitted a stirrer  nitrogen inlet tube  Dry Iceacetone cooled dropping funnel and Dry Ice acetone cooled condenser was placed 30 ml. of n hexane and eight drops of boron fluoride etherate. While a nitrogen atmosphere was maintained  the solution was cooled to  78ºC. and a solution of 10 g. of vinyl ether in 20 ml. of n hexane that was also at  78ºC. was added rapidly. After the reaction mixture had been stirred for 30 min.  10 ml. of methanol was added and the resulting solution was allowed to warm to room temperature. The poly (vinyl ether) was purified and isolated by the same method described in the preceding section. Data for the polymerization of HVE and HEVE are collected in Tables I and II.

Initiation with stannic chloride  titanium tetrachloride and vanadium oxychloride. Inside a dry box that was continually flushed with nitrogen  a 4 oz. screw topped bottle was charged with a weighed amount of vinyl ether and 15 ml. of n hexane. The bottle was sealed with a screw cap that had a hole punched in it and had been lined with a neoprene gasket. When the bottle had been cooled to the desired temperature  a measured volume of n hexane solution containing a known amount of metal chloride or oxychloride was injected through the gasket into the bottle. Cooling was continued until polymerization was terminated by addition of 10 ml. of methanol. The poly(vinyl ether) was purified by the same method described previously. Data concerning the polymerization of HVE and HEVE with cationic initiators are collected in Tables I and II.

Attempted initiation with vanadium trichloride. In general the procedure was the same as described in the preceding section  although the order in which the reagents were added was different. The vanadium trichloride was weighed directly into the polymerization bottle and mixed with n hexane. Then after the bottle was sealed and cooled  the vinyl ether was injected into the bottle. Tables I and II contain data for the attempted polymerization of HVE and HEVE with vanadium trichloride.

Initiation with  Coordination Type  catalysts. A 4 oz. screw topped bottle was charged  in a dry box and under nitrogen  with hexane (10 ml./g. monomer)  a measured volume of a hexane solution of triisobutylaluminum (0.1. g. i Bu3Al/ml.) and a measured volume of hexane solution of titanium tetrachloride (0.084 g. TiCl4/ml.) or vanadium oxychloride (0.03 g. VOCl3/ml.) or a weighed amount of vanadium trichloride. The bottle was sealed with a neoprene gasketed cap and the catalyst mixture was allowed to age.

If the polymerization were to be performed at room temperature  a measured volume of vinyl ether was injected into the polymerization bottle  which was shaken occasionally while it stood for 24 hr. For polymerization at  78ºC. the catalyst mixture  after aging  was cooled in a Dry Ice acetone bath for 30 min. and a measured volume of vinyl ether was injected slowly into the bottle. Cooling was maintained for 24 hr.  during which time the reaction mixture was swirled occasionally. Then the contents of the bottle were poured into rapidly stirred methanol. The precipitated polymer was purified by the same method previously described. Data for the polymerization of HVE and HEVE are collected in Tables III V.

X Ray Analysis of Poly (HVE)

A thick film was obtained by repeated casting of thin layers of a benzene solution of the poly (HVE). After the portions had dried over water  the film was removed from the water and allowed to remain at room temperature for two weeks to remove residual solvent.

A Phillips x ray diffraction instrument (operated by Dr. M.L. Corrin) was used. The major machine settings were  35 Kv.  20 ma.  B1 200  SF 16  TC 4  and M 0.8.

The scan of diffracted x rays (Fig. 1) indicates two maxima (2q = 13.5 and 19.0). Using l = 1.54 and Bragg s Law q = 2d sin the spacing distances are 6.55 and 4.66 A. The sharpness of the recorded scan and the short distance (d) indicate considerable crystalline polymer structure.

Evaluation of Poly (HEVE)

Preparation of sample. A 150 g. sample for evaluation was prepared by polymerizing 10 30 g. lots of 2 hydronopoxyethyl vinyl ether in dry n hexane solution by boron fluoride initiation in a Dry Ice acetone cooling bath. The polymerization mixture was stirred for the first 4 hr. and then allowed to stand for 14 hr. Then  methanol was added  the mixture stirred well and then allowed to warm to room temperature. The polymer was dissolved in benzene  the solution was filtered  and then the polymer precipitated by adding this solution to excess methanol with stirring. Solution in benzene and reprecipitation in methanol was repeated two more times and then the polymer was dried under reduced pressure. On the average conversion was 96% and the inherent viscosity of the polymer varied from 1.5 to 2.1 with the average for the 150 g. sample being 1.8.

 

Terpolymers of Ethylene and Propylene with d Limonene and b Pinene

Introduction

Ethylene propylene terpolymers (EPT) have recently enjoyed a great deal of research activity due to their remarkable oxidation and ozone resistance and their desirable elastomeric properties. The practical utilization of these materials has been hindered somewhat by the economic considerations involved in producing them and also the cost of the nonconjugated diene as the third monomer. In order to circumvent the latter problem  limonene and related monoterpenes obtained from citrus oils were chosen as suitable third monomers. Limonene and a  and b pinenes have been previously homopolymerized by a number of catalysts. Obviously in the case of EPT rubbers  the Ziegler Natta catalysts were the catalysts of choice.

Modena  Bates  and Marvel found that when optically active d limonene was homopolymerized  the resulting polymer was optically inactive. Their work indicated that limonene polymerized into a bicyclic structure (I) as well as the desired structure II. The bicyclic structure was favored over the monocyclic structure by a factor of 1.5 2. In the case of a B pinene  the expected structure (III) was obtained.

Results and Discussion

An experimental program was undertaken to evaluate a series of EPT elastomers from a variety of Ziegler Natta type catalysts. The terpene monomers were introduced into the reaction vessel  containing catalyst and solvent  by vapor entrainment in the ethylene proplene gas stream. This method was found superior to injecting the terpene into the reaction vessel by means of a hypodermic syringe.

The resulting polymers were purified in the usual manner and freeze dried from a benzene solution. The purified product was analyzed for unsaturation by the method of Kolthoff  Lee  and Maris and for methyl group content by infrared analysis. The intrinsic viscosity (0.4% solution in benzene) and gel content were also determined prior to vulcanization. (Gel content was determined by cyclohexane extraction at 23ºC. over a 24 hr.period.)

The polymers sent for vulcanization are reported in Table I. All experimental conditions were kept constant except the types of catalysts employed and the ratio of aluminum alkyl to coordination compound.

The results of vulcanization tests gave highly undercured vulcanizates. The poor results were attributed to high gel content and acidic residues in the polymers. Samples I 49  I 58  I 66  I 69 and I 71 were examined by the testing laboratory for gel content  ash content  and spectrographic analysis on the ash residues. The results of these tests are reported in Table II. All attempts to obtain satisfactory vulcanizates on samples I 62  I 72  I 73  I 74  and I 79 were also unsuccessful. Analogous results were obtained with the b pinene terpolymers  samples II 23  II 24  II 25 and II 28. In all cases  du Pont s Nordel EPT rubber was run as a control. The recipes employed in the vulcanization studies are reported in Table III.

Typical polymerization experiments performed in this study are reported in the experimental section. Where an insufficient amount of polymer was obtained for vulcanization studies  it is so noted. The following catalyst systems were examined  triethylaluminum with vanadium oxytrichloride  titanium tetrachloride  and titanium tetraiodide; triisobutylaluminum with vanadium oxytrichloride  and titanium tetrachloride and diisobutylaluminum chloride with vanadium oxytrichloride and vanadium triacetylacetonate.

          It is difficult to explain why structures II and III (from limonene and b pinene  respectively)  which are those  incorporated in the terpolymers do not lend themselves readily to vulcanization  even though adequate unsaturation is indicated by titration with perbenzoic acid.

Experimental

Materials

Samples of chemical dipentene and d limonene were furnished by Newport Industries Division of Heyden Newport Chemical Corporation. The b pinene was furnished by the Glidden Company. Unless otherwise noted  the monomers were used without further purificaiton. Ethylene and propylene were Matheson C.P. grade and were used directly after passing through two towers of magnesium perchlorate. Heptane  Phillips 99 mole %  was purified by extraction with sulfuric acid  dried over sodium sulfate  distilled from sodium hydride  and stored over sodium ribbons Triethylaluminum  triisobutylaluminum  and diisobutylaluminum chloride (Texas Alkyls); vanadium oxytrichloride and vanadium triacetyl acetonate (Alfa Inorganics  Inc.)  titanium tetrachloride (Matheson  Coleman and Bell) were all used without further purification. Inherent viscosities were determined as a 0.4% benaene solution in a No. 50 Cannon Fenske viscometer at 31º C.

Preparation of EPT Rubber

General procedure. A 1 liter reaction flask equipped with efficient stirrer  condenser  and inlet tube was flame dried under a vigorous stream of prepurified nitrogen. Apiezon grease N was used throughout the system. The solvent was introduced and saturated with an ethylene propylene gas mixture. The source of third monomer was then connected into the system and the appropriate amounts of catalyst (dissolved in solvent) were introduced into the reaction flask by means of hypodermic syringes.

Immediately  the appropriate rates of flow of ethylene and propylene gases were begun and the reaction allowed to run  with vigorous stirring  for the noted period of time and at the stated temperature.

Upon completion of the reaction  10% hydrochloric acid in methanol (200 ml.)  containing a small amount of 2 6 di tert butyl p cresol (du Pont Antioxidant No. 29)  was introduced  under a nitrogen atmosphere  to destroy the catalyst  and the resulting mixture was thoroughly mixed with excess methanol in a high speed Waring Blendor. The resulting polymer was collected on a filter and purified by repeated precipitation in methanol from benzene. After five precipitations  the resulting polymer was lyophilized from a benzene solution (approximately 10% in polymer) containing about 0.1% du Pont Antioxidant No. 29. The various physical properties were determined on the dried polymer.

Reaction parameters. Reaction parameters are listed in Table IV.

Analysis of Unsaturation

Preparation and standardization of sodium thiosulfate solution. In a dark bottle was placed 13.22 g. (0.09 equiv.) of reagent grade sodium thiosulfate and 900 ml. of freshly boiled distilled water. The resulting solution was allowed to stand at least 24 hr. prior to standardization. The sodium thiosulfate was standardized by titration of the iodine liberated from a solution containing an accurately weighed amount of potassium iodate (0.1 0.15g.  reagent grade  previously dried at ~ 110ºC. for 24 hr. and stored in a desiccator)  1 g. of potassium iodide  and 50 ml. of 0.4M acetic acid solution to a starch endpoint.

 

Base catalysed isomerisations of terpenes

The panorama of base catalysed isomerisations of terpenes is an important part of aroma chemistry. Major contributions in this area are presented here under sections on hydrocarbons  alcohols  aldehydes  ketones  acids  esters  and epoxides.

Hydrocarbons

p Menthenes. Pines and Eschinazi introduced sodium organosodium catalysts  for example sodium  benzylsodium  catalyst (prepared by treating an excess of sodium in toluene with o chlorotoluene) for isomerising the title compounds. One of their main findings is that when (+) p menth 1 ene (1)  trans p menth 2 ene (2) or p menth 3 ene (3) is refluxed at 168 175º for 20 22 hrs with the catalyst  the isomerisate is an equilibrium mixture of (3) (63%)  (1) (32%)  and p menth 8 (9) ene (4) (5%). The rate of racemisation of (+) (1) is relatively faster than that of its rate of isomerisation and (+) trans (2) reorganised to (+) (1). There is no formation of p cymene (5). The mechanism proposed involves intermediate carbanions.

More recently  Ferro and Naves studied the isomerisation of (1)  (3)  (4) (cis and trans) and p menth 4(8) ene (6) with sodium organosodium catalyst (catalyst S  prepared according to Pines and Eschinazi  xylene replacing toluene) and analysed (by GC) the products formed at reflux temperatures. Under these experimental conditions  there is no equilibrium of the p menthenes. Thus  (3) is obtained from (+) (1) and cis (4) in 52.1 and 78.6% in 48 and 6 hrs respectively; trans (4) however  is less reactive than its stereoisomer.

Further  the behaviour of the p menthenes toward n lithioethylenediamine (catalyst L) at 50º and potassium tert butoxide (t BuOK) in dimethylsulfoxide (DMSO) (catalyst B) at 100º was evaluated. By a 4 hr treatment with catalyst L  (+) (1) only a small amount of the racemate resulted and with catalyst B  the racemisation rate increases of 16% in 2 hrs without isomerisation. Reaction of cis (4) and trans (4) with catalyst L furnishes (6) in 76.9 and 48.6% (in 4 hrs) and with catalyst B  77.0% (in 8 hrs) and 64.3% (beyond 12 hrs) respectively. Use of catalyst S is recommended for the preparation of (3) from (1) and of catalysts L and S to obtain (6) from (4) (cis and trans).

Kinetically controlled regrouping of p menthenes with calcium amide catalyst in the liquid phase gives equivalent mixtures of isomers with exo and endocyclic double bonds.

o Menthenes. Rearrangements similar to p menthenes are observed in the interaction of the sister o isomers with calcium amide catalyst.

p Menthadienes. Investigations on base catalysed rearrangements of this family of hydrocarbons were reported by Pines and Eschinazi. On reluxing (+) limonene (7) with sodium  benzylsodium  or sodium hydride catalyst  rapid racemisation occurs with evolution of hydrogen  providing p cymene (5). Interruption of the reaction when the optical rotation drops to ~20% gives a catalysate that includes 20% of (+) (7)  50% of (+) (7) and 20% of a mixture consisting of p mentha 2 4(8)  and p mentha 3 8(9) diene (8) and (9) in the approximate ratio 4 1 and 1% of (5). Without a promoter but in the presence of sodium at relux temperature  (+) (7) only undergoes racemisation without aromatisation. With the catalyst  the intermediates (8) and (9) are reversibly isomerised; on the other hand  ( ) a phellandrene (10) loses optical activity and gets dehydrogenated to (5) with no signs of condition to (8) and (9). Invoking carbanions these changes have been explained.

Swiss investigators have also tracked in the same way as p menthenes the transformations of p menthadienes. When reacted for 1 hr with catalyst L at 50º  (+) (7) gives an equilibrium mixture of (8)  (9)  g terpinene (13) and a terpinene (14) in the proportion 14 50 30 3 with increasing conversion to (5)  depending on the reaction time. On processing with catalyst B  the substrate is practically effected in 5 hrs at 100º and equilibrium is realised. Under refluxing conditions  catalyst S generates (8) and (9) in the proportion 11 1.

Terpinolene (11)  isolimonene (p mentha 2 8(9) diene) (12) and g terpinene (13)  with the exception made for the latter in the case of catalyst S  respond in a similar manner. With catalyst L  the equilibrium of (11)  (12) and (13) is attained in 30 min and with catalyst B  in 15 min. Complete isomerisaton is achieved in 6 hrs with catalyst S  leading to (8) and (9) in the approximate proportion 11 1 As against these  with catalyst S  (13) changes completely to p cymene (5) in 15 hrs.

The study with the conjugated dienes (8)  (9)  (14)  and p mentha 2 4 diene 15) has led to interesting results. Equilibrium between (8)  (9)  and (14) is attained by the action of catalysts L and B. Divergent behaviour is displayed with catalyst S; the cyclic dienes (14) and (15) only give (5) (100 and 90% in 24 hrs); (8) equilibrates with (9) in the approximate ratio 11 1. A modified carbanion mechanism has been advanced to explain this reaction.

Using pines and Eschinazi catalyst  isoterpinolene (8) has been synthesised from (+) limonene (7).

A kinetic study of the action of t BuOK DMSO system on (±) limonene indicates that the initial products of isomerisation is a 5 3 1 mixture of (8)  (13)  and (14) and that the pseudo first order rate constant of 55º is 4.5 x 10 6 sec 1. Under the experimental conditions  (8) and (14) afford the same products in 30 min. Hence the slow step in the isomerisation is the migration of the double bond to the exoposition.

From the above synthetic mixture derived from (±) limonene  by precise fractionation  (8) is recoverable in 11% yield. Since the sister isomers can also bereverted to this mixture and recycled  this is an elegant method for the large scale preparation of this unusual hydrocarbon.

Whereas (±) p mentha 2  4(8)diene (8) is convertible to (±) menthol isomers  it is the (±) 8 that is higher priced  being a possible precursor in the synthesis of ( ) menthol. Technically  a facile route to this hydrocarbon is from (±) isolimonene (12) by contact with t BuOk DMSO combination at room temperature.

In the rearrangement of p menthadienes catalysed by t BuOK DMSO at 55º  only three constituents of the isomerisate have been identified. A fuller picture of the equilibrium composition  conditions for achieving it with 76.2%) with lesser amounts of m mentha 1 8diene (19)  m mentha 6 3(8) diene (20) m mentha 1(7) 8 diene (21)  and m cymene (22); at 100º aromatisation is complete. By reaction with t BuOK DMSO system at 82±2º for 3 hrs  sylvestrene (17) affords (18) (45.0%)  (19) (3.0%)  (20) (5.5%)  and (21) (0.9%) 13. With the same catalyst  the hydrocarbon (18) largely resists rearrangement but the sister isomer (20) smoothly conjugates to (18).

(+) Car 3 ene. Ohloff and coworkers accomplished the base catalysed conversion of (+) car 3 ene (23) to (+) car 2 ene (24). The reaction of (23) with N lithioethylenediamine for 1 hr at 100º results in an equilibrium mixture of the 3  and 2 isomers in the ratio 3 2  accompanied by cymenes equivalent to 2%. From the catalysate  enriched (+) car 2 ene (80%) is obtained by fractionation. Others have followed this trail. Theroretical reasons have been advanced to account for the greater stability of the 3  over the 2 isomer. From the equilibrium constant 1.50  the free energy difference is extracted as 240 cal/mol at 25º.

A disadvantage of the above technique is the concurrent release of the cymenes. However  under regulated conditions  use of t BuOK DMSO catalyst eliminates this defect and the reaction generates a clean equlibrium mixture consisting of 40% (+) car 2 ene and 60% (+) car 3 ene.

While today more advanced and different syntheses for ( ) menthol are used  patents granted to Booth combined with that to Webb are classies of the technical exploitation of (+) car 3 ene for a ( ) menthol synthesis. The outstanding step in the chain of reactions is the rearrangement of the terpene to the 2 isomer. In general  basic catalysts recommended consist of strong bases  applied under conditions when carbanions of a hydrocarbon can be formed and these include simple or complex alkali metal alkyls  also strong bases such as alkali metal alkoxides  and alkali metal amides  which are advantageously used in media that encourage the maturing of their basicity. Examples of the catalysts are activated sodium of the Pines type  sodium and/or potassium derivative of y picoline  t BuOK in DMSO  N lithioethylenediamine  and Na or K metal on Al2O3.

Here we may digress a little. Above 180º  in the presence of the basic catalyst  (+) car 2 ene (24) decyclises to (+) isolimonene (12) and the latter conjugates to (+) p mentha 2  4(8) diene (8)  the pivotal hydrocarbon in a ( ) menthol synthesis. The next stage is the migration of the exo double bond of (8) to give an equilibrium mixture of a terpinene (14) (50%)  g terpinene (13) (20%)  isoterpinolene (8) (25%) and p mentha 3  8 diene (9) (5%). Finally the p menthadienes get dehydrogenated to p cymene (5). For these reasons  the correct temperature and time must be chosen to terminate the reaction at the isoterpinolene stage. Catalysts which rearrange (+) car 3 ene to (+) car 2 ene will also perform this function.

Ferro found that Ohloff s reaction when conducted at 110º for 5 hrs gives an equilibrium mixture of (+) car 3 ene (23) and (+) car 2 ene (24) (55 45) with cymenes (12%); an 18 hr run augments aromatisation (20.4%). Also  the findings of Acharya and Brown using t BuOK DMSO have been fully substantiated.

There are valuable data on the isomerisation of (+) car 3 ene (23) over basic catalysts such as MgO  Cao  SrO2  Y2O3. La2O3 and ZrO2 by the pulse method. The reaction has been tracked in detail over MgO (I) and MgO (II) and CaO (II) catalysts. Rearrangement of (23) to (24) is the dominant change  by synchronised two way decylisation leads to a terpinene (14) and m mentha 1 5 diene (25) and further dehydrogenation to p cymene (5) and m cymene (22). From a tracer study with deuterium it is inferred that the double bond shift is most likely to proceed via II allylic anion (26).

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