Camphene preparation

Borneol and isoboineol are respectively the endo and exo forms of the alcohol. Borneol can be prepared by reduction of camphor inactive borneol is also obtained by the acid hydration of pinene or camphene. Borneol has a smell like camphor. The m.p. of the optically active forms is 208-5 C but the racemic form has m.p. 210-5 C. Oxidized to camphor, dehydrated to camphene. 

Ordinary commercial camphor is (-i-)-cam phor, from the wood of the camphor tree. Cinnamonum camphora. Camphor is of great technical importance, being used in the manufacture of celluloid and explosives, and for medical purposes, /t is manufactured from pinene through bornyl chloride to camphene, which is either directly oxidized to camphor or is hydrated to isoborneol, which is then oxidized to camphor. A large number of camphor derivatives have been prepared, including halogen, nitro and hydroxy derivatives and sulphonic acids. 

Chlorinated Terpenes. A group of incompletely characterized insecticidal compounds has been produced by the chlorination of the naturally occurring terpenes. Toxaphene [8001-35-2] is prepared by the chlorination of the bicycHc terpene, camphene [79-92-5] to contain 67—69% chlorine and has the empirical formula C QH QClg. The technical product is a yellowish, semicrystalline gum (mp 65—90°C, d 1.64) and is a mixture of 175 polychloro... 

Camphene Manufacture. Camphene (13) is produced by the reaction of a-pinene (8) with a Ti02 catalyst (80). Preparation of the catalyst has a great influence on the product composition and yield. Tricydene (14) is formed as a coproduct but it undergoes the same reactions as camphene thus the product is generally used as a mixture. They -menthadienes and dimers produced as by-products are easily removed by fractional distillation and the camphene has a melting poiat range of 36—52°C, depending on its purity. Camphene is shipped ia tank cars, deck tanks, and dmms. 

Uses ndReactions. Camphene is used for preparing a number of fragrance compounds. Condensation with acids such as acetic, propionic, isobutyric, and isovaleric produce usehil isobomyl esters. Isobomyl acetate (41) has the greatest usage as a piae fragrance (81). The isobomyl esters of acryhc and methacrylic acids are also usehil ia preparing acryUc polymers. 

Camphene is extremely difficult to separate in the solid condition from essential oils, and it may therefore be taken for granted that natural camphene is rarely prepared in the pure condition. The figure given above for the specific rotation is for a sample artificially prepared from pinene hydrochloride. 

Camphene is prepared artificially by the isomerisation of pinene with sulphuric acid or by the withdrawal of HCl from pinene monohydrochloride, or by the action of heat in the presence of acetic anhydride on bornylamine, CjjHj7NH2, which causes the withdrawal of ammonia and leaves camphene, as follows —... 

The isobomeol so formed melts at 212°, but the determination must be carried out in a sealed tube, as the melting-point is very dose to the temperature of sublimation. It is, however, very rarely that the isobomeol so prepared is free from impurities, and the melting-point will often be found to be as low as 203° to 205°. It is therefore necessary to pare derivatives of the isobomeol in order to identify it with certainty. Kie compound with bromal melts at 71° to 72°. Other compounds will be found mentioned under isobomeol . By dehydration by means of zinc chloride, isobomeol is easily converted into camphene, melting at about 49° to 50°. 

A number of characteristic derivatives of camphene have been prepared of which the following are the most important. 

Camphene hydrochloride, Cj(,H gHCl, is prepared by passing dry hydrochloric acid into an alcoholic solution of camphene. When re-ctystallised from an alcoholic solution containing excess of hydrochloric acid, it melts at 155° (or possibly a few degrees lower).- Melting-points from 149° to 165° have been recorded for this compound, but the products examined were probably not in a state of purity. 

Camphene hydrate is a tertiary alcohol, and a study of its characters and method of preparation caused Aschan to consider that it is improbable that borneol and isoborneol are stereoisomeric, but that they probably have different constitutional formulae. 

Toxaphene is a complex mixture of compounds prepared by chlorinating camphene, and contains several hundred polychlorinated bornanes. After incubation with Sulfurospirillum (Dehalospirillum) multivorans only the hexa- (B6-923) and the heptachlorinated (B7-1001) remained. The nonachlorinated congener B9-1679 could be transformed by preferential dechlorination of the em-dichloro groups with formation of the heptachlorinated B7-1001 (Ruppe et al. 2003). Further examination showed that this congener could be dechlorinated to penta- and hexachlorinated bornanes (Ruppe et al. 2004). 

The purpose of this work was to determine the toxicity to mosquito larvae of insecticide spray residues. That certain insecticides are translocated in plants (4, 5) adds impetus to this study. Fresh orchard fruit sprayed or dusted with preparations containing parathion (0,0-diethyl O-p-nitrophenyl thiophosphate), tetraethyl pyrophosphate (TEPP, HEPP), DDD [2,2-bis(p-chlorophenyl)-l,l-dichloroethane], DDT [2,2-bis(p-chlorophenyl)-l,l,l-trichloroethane], chlorinated camphene, and basic lead arsenate were shipped from California to Yonkers, N. Y., by air express for bioassay. 

It is well known that Rh(I) complexes can catalyze the carbonylation of methanol. A heterogenized catalyst was prepared by ion exchange of zeolite X or Y with Rh cations.126 The same catalytic cycle takes place in zeolites and in solution because the activation energy is nearly the same. The specific activity in zeolites, however, is less by an order of magnitude, suggesting that the Rh sites in the zeolite are not uniformly accessible. The oxidation of camphene was performed over zeolites exchanged with different metals (Mn, Co, Cu, Ni, and Zn).127 Cu-loaded zeolites have attracted considerable attention because of their unique properties applied in catalytic redox reactions.128-130 Four different Cu sites with defined coordinations have been found.131 It was found that the zeolitic media affects strongly the catalytic activity of the Cd2+ ion sites in Cd zeolites used to catalyze the hydration of acetylene.132... 

Bomeol is oxidized to camphor with chromic or nitric acid dehydration with dilute acids yields camphene. Bomeol is readily esterified with acids, but on an industrial scale bornyl esters are prepared by other routes. For example, levorotatory bomeol is synthesized industrially from levorotatory pinenes by Wagner Meerwein rearrangement with dilute acid, followed by hydrolysis of the resulting esters [86]. 

Impregnation of cobalt and molybdenum (without sodium) increases largely the isomerizing activity of the catalyst the /3-pinene is then completely converted. The catalysts prepared with sodium molybdate and sodium hydroxide (Co-Mo-Na and Na-Co-Mo-Na) have lower isomerizing activities while their HDS activities are significantly increased. As in the case of alumina supported catalysts the sulfided CoMo phase protected by a double layer of alkaline ions on the carbon support gives the best results in HDS of /3-pinene. The behaviour of this catalyst was examined in desulfurization of the turpentine oil (40% a-pinene, 25% /3-pinene, 25% A -carene and 10% camphene + dipentene + myrcene, 1500 ppm S). The results are recorded in Table 6. 

Sorensen and co-workers799-801 have studied the fate of observable camphene hydrocation 190 prepared from isoborneol 187, camphene 188, or tricyclene 189 in HSO3F acid medium (Scheme 5.74). The intermediate cycloalkenyl cation 191 can also be prepared by protonation of a-terpineol (192), sabine (193), and /3-pinene (194) (Scheme 5.75). 

The presence of water was subsequently identified as being essential for the performance of the above set-up and for maintaining high enantiose-lectivity (Lindstrom et al., 1990). The preparative-scale enantiomeric separation of racemic camphene with a separation factor as high as a — 3.7 (measured at 30°C on an analytical column) was subsequently achieved at 45°C on a 2.1 m x 4 mm (i.d.) column containing a-cyclodextrin hydrate in formamide (1 5, w/w) coated on Chromosorb W (AW, 45-60 mesh) by saturating the carrier gas (helium) with water vapour (Lindstrom et al., 1990). 

A group of highly chlorinated polycyclic insecticides, exemplified by heptachlor (143) and aldrin (144), is prepared from hexachlorocyclopentadiene and cyclopentadiene. The y-isomer (lindane, 145) of hexachlorocyclohexane (HCH) is the toxic component of HCH, first prepared by Michael Faraday. Toxaphene consists of a complex mixture of chlorinated camphenes, of which 146 represents a particularly toxic isomer. 

Fig. II Selected experimental and calculated results for the temperature dependence of the optical rotation at 365 nm. Top-. Fenchone. Center a-Pinene. Bottom Camphene. Data to prepare the plots were taken from [125] (experimental data were from Wiberg et al., J. Phys. Chem. A (2005), 109 3405)...

Midland and co-workers demonstrated that certain p-alkyl-9-borabicyclo [3.3.1] nonanes can reduce benzaldehyde to benzyl alcohols under mild conditions. Several optically active terpenes such as (+)-a-pinene (6.54), (—)-P-pinene (6.55), (—) camphene (6.56) and (+)-3-carene (6.57) have been used to prepare asymmetric (3-alkyl-9-BBN reagents. 

The aim of variant (iii) is to obtain well-defined low-chlorinated single toxaphene components. Further chlorination of the single components allows one to produce several higher chlorinated components. The idea of this approach goes back to the initial investigators of the mechanisms of camphene chlorination [38,39,46]. In 1976, Parlar et al. prepared seven low-chlorinated bornanes by adding small amounts of Cl2 to camphene [103]. In a similar way, Turner et al. isolated 2-exo,10-dichlorobornane (B2-20). Photochlorination of B2-20 resulted in B7-515 (P-32) [53]. Parlar and co-workers applied this method to pro-... 

Camphene is a solid terpene. The dextro variety d-camphene is found in camphor, ginger and spike oils, and the levo variety, 1-camphene is in citrondla and valerian oil and in French and American turpentine. Bornylene does not occur in nature but has been prepared from the alcohol corresponding to it known as Borneol or Borneo camphor. This, as previously stated, may be prepared from pinene so that Bornylene itself may be made from pinene. Fenchene, also, is not found in nature but is obtained by reduction of fenchone a terpene ketone found in fennel oil and in Thuja oil. 

Example 10-camphenylsodium is produced from camphene (2,2-dimethyl-3-methylenebicyclo[2.2. l]heptane), n-C H,K is prepared in situ from n-C H Li and KOR [R = CfCH j, menthyl]. 

Terpenes are reputed to increase cholesterol solubility in bile, though are less effective than bile acids. There are two such preparations available, Rowatinex and Rowachol , containing some combination of the following anethol, borneol, camphene, cineole, mendone, menthol, pipene and renchone, in olive oil. Direct contact dissolution by direct injection of organic solvents, such as methyl tert-butyl ether (MTBE), is sometimes used. 

An alternative route for the synthesis of primary phosphines involves the disproportionation of phosphinic acids, RP(0)(0H)H, at elevated temperatures. This procedure has been used in the synthesis of endo-8-camphanylphosphine (29) from inexpensive camphene by pyrolysis at 220-240 °C (Equation (8)).38 The phosphine is a colorless, low-melting-point solid that partly crystallizes on standing or, in other preparations, is obtained as an air-sensitive, odorous liquid. 

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