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Encyclopedia Britannica - Main :: MOL-MOS |
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MONOCYCLIC TERPENE GROUP Limonene, At :8(9) terpadiene, C10H16, is known in three forms, namely d-limonene, l-limonene, and i-limonene or dipentene. d-Limonene is the chief
found in oil of fir-cones and in Russian peppermint oil. Both are Menthol (terpan-ol-3), C1oH20O. The laevo variety is the chief
redwing the from each other only in rotatory power. Dry hydrochloric acid menthone obtained by E. Beckmann and M. Pleissner :nn., 1891, gas converts them into optically active limonene hydrochloride, 262, p. 21) from pulegone hydrobromide with sodium and alcohol. while in the moist condition it gives dipentene dihydrochloride. It crystallizes in prisms which melt at 43 C. and boil at 212 C. When heated to a sufficiently high temperature they are con-verted into dipentene. Four optically active nitrosochlorides are known, two corresponding to each of the active limonenes, and these on heating
distillation
heating
Terpinolene, 01:4(8) terpadiene, has not as yet been observed in essential oils. It is formed by the action of hot dilute sulphuric acid on terpineol, terpin hydrate and cineol. It is an inactive liquid boiling at 183-185 C., and is readily converted into terpinene by acids. Terpinene, DI : 4(8) terpadiene (?), is found in cardamom oil and in oil of marjoram. It is formed by the action of alcoholic sulphuric acid on dipentene, terpin hydrate, cineol phellandrene or terpineol; or by the action of formic acid on linalool. Phellandrene is . a mixture of Al : 5 terpadiene and 02: 1(7) terpadiene (pseudo-phellandrene) (F. W. Semmler, Ber., 1903, 36, p. 17491. It is found as d-phellandrene in oil of water-fennel and oil of elemi, and as l-phellandrene in Australian eucalyptus oil and oil of bay. It is an exceedingly unstable compound, and must be extracted from the oils by distillation
Svlvestrene, Al :8(9) meta-terpadiene, is found in Swedish and Russian oil of turpentine and in various pine oils. It boils at 175-176 C. and is dextro-rotatory. It is one of the most stable
Carvestrene is obtained by the distillation of carylamine or vestrylamine hydrochloride (A. v Baeyer, Ber., 1894, 27, pp. 3485 seq.). It is regarded by Baeyer as i-sylvestrene. It was synthesized by W. H. Perkin and G. Tattersall (Proc. Chein. Soc., 1907, 22, p. 268) by the application of the Grignard reaction to the ethyl ester of y-ketohexahydrobenzoic acid M. By the action of magnesium methyl iodide this ester yields the lactone of y-hydroxy-hexahydrometa-toluic acid, which is transformed by hydrobromic acid into the corresponding y-bromo-hexahydro-meta-toluic acid. This latter substance by the action of pyridine
179-180 C. of the double
dioxide yields I-methyl-4-isopropyldiketohexamethylene. This ketone is then reduced to the secondary alcohol, the hydroxyl groups replaced by bromine, and hydrobromic acid is then removed froth the bromo-compound by boiling it with quinoline
It is readily oxidized by chronic acid to the corresponding ketone menthone. By the action of phosphorus pentoxide, or zinc chloride, it is converted into menthene, CioHis, and when heated with anhydrous copper sulphate to 250 C. it yields para-cymene. It is reduced by hydriodic acid and phosphorus to hexahydrocymene. The phosphorus haloids yield haloid esters of composition C10H19C1, which, according to I. L. Kondakow (Jour. prakt. Chem., 1899 [2]. 6o, p. 257) are to be regarded as tertiary esters; a similar type of reaction is found in the case of carvomenthol. A d-menthol has been prepared from the i-mixture obtained by reducing menthone with sodium. The mixture is benzoylated, and the liquid d-menthol benzoate separated and hydrolysed. Tertiary menthol (terpan-ol-4), a liquid boiling at 97-101 C. (2o mm.), has been obtained by the hydrolysis of the ester prepared by heating menthene with trichloracetic acid (A. Reychler and L. Masson, Ber., 1896, 29, p. 1844). It possesses a faint pepper-mint odour. W. H. Perkin, junr. (Proc. Chem. Soc., 1905, 21, p. 255) synthesized it from 1.4 methylcyclohexanone: sodium carbonate converts a-bromhexahydro-para-toluic acid (I) into i .1-tetrahydro-para-toluic acid and a-oxyhexahydro-para-toluic acid, and the latter on treatment with dilute sulphuric acid yields I.4-methylcyclohexanone (2), which by the action of magnesium isopropyl iodide and subsequent hydrolysis is converted into tertiary menthol (3). CHa CII End of Article: MONOCYCLIC TERPENE If you wish, you can link directly to this article.
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