Camphene derivatives

Table 1. Ultraviolet Light Absorption of Some Longifolene and Camphene Derivatives...

Treatment of 3,3-dibromocamphor with bromine and chlorsulphonic acid (conditions under with 3,3,8-tribromocamphor is formed), followed by working-up the crude reaction mixture with zinc and hydrobromic acid to effect selective debromination, provided 8-bromocamphor (456) in a regiospecificprocess. Prolonged treatment of c(,/-camphor with excess BF3, OEt2 and ethyl diazoacetate in ether afforded a 2 1 mixture (63 % yield) of the camphene derivatives (457) and (458). Reaction of the mixture with zinc dust and glacial acetic acid at reflux gave (457) in essentially quantitative yield from (458). ... 

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. 

By oxidation with permanganate it forms pinonic acid, C,oH,<503, a monobasic acid derived from cyclobutane. With strong sulphuric acid it forms a mixture of limonene, dipentene, terpinolene, terpinene, camphene and p-cymene. Hydrogen chloride reacts with turpentine oil to give CioHijCl, bomyl chloride, artificial camphor . 

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. 

Closely related to this change is the conversion of bomeol and its derivatives into compounds of the camphene type ... 

Physical Form. Volatile liquid, colorless or yellow, which is a mixture of natural substances obtained ftom resinous exudates or resinous wood ftom living or dead coniferous trees, especially pine trees. The chemical composition can vary with the source and method of derivation, but a typical analysis of turpentine is a-pinene, 82.5% camphene, 8.7% (3-pinene, 2.1% unidentified natural turpenes, 6.8%. 

X-Ray diffraction studies of ( )-carbocamphenilone," of (-)-camphene-8-carboxylic acid," and of a number of Money s brominated camphor derivatives (Vol. 6, p. 39 Vol. 7, p. 40) have been published they include 8-bromo-camphor," l,7-dibromo-3,3,4-trimethylnorbornan-2-one, l,7-dibromo-4-... 

Camphene and derivs 2 C19—C20 camphenenitronitrosite 2 C20 camphenenitrosite 2 C20 campheneozonide 2 C20 nitrocamphenes 2 C19—C20 5-nitroso-5-nitrocamphene 2 C20... 

Arbuzov has described the isomerization of jff-pinene oxide (Kq. 444) and camphene oxide (Eq. 445) to the corresponding aldehyde derivatives in the presence of zinc bromide. 

Terpenes are a class of naturally occurring olefins found in many plants. They are biosynthetically derived from isoprene, CsHg, and therefore consist of Cs-building blocks and are found in both cyclic and acyclic forms. An important subgroup is the monoterpenes, which consist of two isoprene units and are of the molecular formula Ci0H16. Of the monocyclic monoterpenes, by far the most industrially relevant is limonene, which is abundantly present as a fragrance in various household products. From the bicyclic monoterpenes, a-pinene, p-pinene, camphene, and carene are of industrial relevance and are also mostly used in the fragrance industry [44]. 

For cyclohexane derivatives, convulsive activity is associated, apparently specifically, with a particular molecular topography that is only achieved with the aaaeee arrangement of substituents However, the norbornene and camphene carbon skeletons apparently permit the attainment of a similar topography... 

Fig. 5-3. Examples of mono- and sesquiterpenes and their derivatives in softwood. 1, a-Pinene 2, /3-pinene 3, 3-carene 4, camphene 5, borneol (R = H), bornyl acetate (R = COCH3) 6, limonene 7, a-terpineol 8, dipentene 9, a-muurolene 10, 8-cadinene 11, a-cadinol 12, a-cedrene 13, longifolene 14, juniperol.

Bornane monoterpenes are exemplified by camphene (2,2-dimethyl-3-methylene-bicyclo[2,2,1]heptane), a structure in which two fused cyclopentane rings share three Cs. We can simply represent the camphene skeleton as a cyclohexane with a methylene (—CH2—) cross-link (G6(-CH2—)). The keto derivative camphor (camphor smell), the ether eucalyptol (eucalyptus smell) and the simple bornene a-pinene (pine smell) are familiar examples. 

Malpass and Tweddle have isolated a jS-lactam derivative (6) by the reaction of CSI with camphene (5) in CHjClj at -60°. At higher temperatures, (6) rearranges to thermodynamically preferred products (7) and (8). 

Cyclopentane bicyclic monoterpenoids that occur in the plant kingdom belong to three major skeletal types camphane, iso-camphane, and fenchane (Fig. 7). Camphane-type terpenoid alcohols, (+)-bomeol (Gl) and (—)-isobomeol (G2), have been isolated from Cinnamomum camphora (Lauraceae) and Achillea filipendulina (Asteraceae). A ketone derived from these, (-h)-camphor (G3), is found in the camphor tree Cinnamomum camphora) and in the leaves of rosemary Rosmarinus officinalis) and sage Salvia officinalis, Labiatae). Camphene (G4) and its enantiomer with the isocamphane carbon skeleton are known to occur in the oils of citronella and turpentine. Fenchane-type bicyclic cyclopentane monoterpenoids are commonly found in plants as their ketone derivatives. (—)-Fenchone (G5) occurs in the tree of life Thuja occidentalis, Cupres-saceae). Its enantiomer, (+)-fenchone (G6), has been isolated from the oil of fennel Foeniculum vulgare, Umbelliferae). 

Camphor and Bomeol are therefore derived from a camphane di-cyclic terpene in which the isopropyl group joins the para carbons. The unsaturated di-cyclic terpene corresponding to camphor was at first supposed to be camphene but later work has proven that it is not camphene but Bornylene which has the structure corresponding to camphor. The constitution of camphene is still unestablished. 

Now the spirit of turpentine is derived from cymene by the substitution of two H2 groups for two atoms of hydrogen if these occupy the positions 2 and 6 or 3 and 5, symmetrical with regard to the plane of symmetry passing through 1 and 4, we shall have inactive isomers on the other hand we shall have active isomers (tereben-thene and camphene) if they occupy positions not symmetrical to one another, as 2 and 5 or 2 and 3 we might apply the same reasoning to the other isomers of terebenthene, (for the formulas of these see the memoir of Mr. Oppenheim, loc. cit. p. 560). 

---