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MONOCYCLIC TERPENE

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Originally appearing in Volume V26, Page 648 of the 1911 Encyclopedia Britannica.
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MONOCYCLIC TERPENE See also:

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 See also:chief constituent of oil of See also:orange-rind, and is See also:ALCOHOL AND KETONE DERIVATIVES also found in oil of See also:lemon and oil of See also:bergamot. l-Limonene is found in oil of See also:fir-cones and in See also:Russian See also:peppermint oil. Both are Menthol (terpan-ol-3), C1oH20O. The laevo variety is the chief pleasant-smelling liquids, which See also:boil at 175-176° C. They differ portion of oil of peppermint; it may be prepared by See also:redwing the from each other only in rotatory See also:power. Dry hydrochloric See also:acid menthone obtained by E. See also:Beckmann and M. Pleissner :nn., 1891, See also:gas converts them into optically active limonene hydrochloride, 262, p. 21) from pulegone hydrobromide with See also:sodium and alcohol. while in the moist See also: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 See also:con- verted into dipentene. Four optically active nitrosochlorides are known, two corresponding to each of the active limonenes, and these on See also:heating with alcoholic potash are converted into d- and l-carvoxime.

Dipentene (i-limonene) is found widely distributed in many essential See also:

oils, e.g. of camphor, Russian See also:turpentine, See also:cubebs, bergamot, See also:cardamom, &c., and is also a product of the dry See also:distillation of many See also:vegetable resins. It may be produced by heating many See also:terpenes (pinene, camphene, sylvestrene, limonene) for several See also:hours at 250-270° C.; or by the polymerization of isoprene at 300° C. To obtain pure dipentene it is best to See also:heat dipentene hydrochloride with anhydrous sodium acetate and glacial acetic acid (0. Wallach, See also:Ann. Chem. Pharm., 1887, 239, p. 3). It is a pleasant-smelling liquid, which boils at 175-176° C., and polymerizes on heating to high temperatures. When warmed with alcoholic sulphuric acid it yields terpinene, whilst concentrated sulphuric acid or See also:phosphorus pentasulphide convert it into paracymene. Dipentene dihydrochloride, CioH16-2HC1, See also:beet prepared by passing a current of hydrochloric acid gas over the See also:surface of a glacial acetic acid See also:solution of dipentene, crystallizes in rhombic tables which melt at 5o° C. and boil at 118-12o° C. (to mm.). It is apparently a trans-See also:compound. for A. v.

See also:

Baeyer (Ber., 1893, 26, p. 2863) has obtained a cis-dihydrochloride of melting-point 25° (circa), by the See also:action of hydrochloric acid on cineol. 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 See also: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 See also: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 See also:water-See also:fennel and oil of See also:elemi, and as l-phellandrene in Australian See also:eucalyptus oil and oil of See also:bay.

It is an exceedingly unstable compound, and must be extracted from the oils by distillation in vacua. The See also:

hydrocarbons obtained from elemi oil and eucalyptus oil correspond to A1.5 terpadiene. A similar See also:hydrocarbon was obtained by C. Harries and M. See also:Johnson (See also:Bee., 1905, 38, p. 1832) by converting carvone hydro-bromide into A6 terpenone-2, then, by phosphorus pentachlcride, into chlor-2-phellandrene, which is finally reduced. Svlvestrene, Al :8(9) See also:meta-terpadiene, is found in See also:Swedish and Russian oil of turpentine and in various See also:pine oils. It boils at 175-176° C. and is dextro-rotatory. It is one of the most See also:stable of the terpenes and gives a characteristic deep See also:blue See also:colour on the addition of a drop of sulphuric acid to its solution in acetic an-hydride. On treating the hydrobromide with See also:bromine in the presence of See also:iodine, a product is obtained which on reduction yields meta-cymene (A. v. Baeyer and V. Villigcr, Ber., 1898, 31, p.

2067). 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. See also:

Perkin and G. Tattersall (Proc. Chein. See also:Soc., 1907, 22, p. 268) by the application of the Grignard reaction to the See also:ethyl ester of y-ketohexahydrobenzoic acid M. By the action of See also: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 See also:

pyridine yields tetrahydro-metatoluic acid, the ester of which by magnesium methyl iodide is converted into 0•I-meta menthenol-8 (2). The meta-menthenol on dehydration by See also:potassium bisulphate yields carvestrene (3) of boiling-point 179-180° C. of the See also:double linking in the See also:molecule is shown by the use of the See also:symbol A followed by the number of the See also:carbon See also:atom immediately preceding it. dioxide yields I-methyl-4-isopropyldiketohexamethylene. This ketone is then reduced to the secondary alcohol, the hydroxyl See also:groups replaced by bromine, and hydrobromic acid is then removed froth the bromo-compound by boiling it with See also:quinoline, leaving the terpene. It is a liquid which boils at 174° C. and shows a See also:complete terpene See also:character. It is readily oxidized by chronic acid to the corresponding ketone menthone. By the action of phosphorus pentoxide, or See also:zinc chloride, it is converted into menthene, CioHis, and when heated with anhydrous See also:copper sulphate to 250° C. it yields See also:para-cymene. It is reduced by hydriodic acid and phosphorus to hexahydrocymene. The phosphorus haloids yield haloid See also:esters of See also:composition C10H19C1, which, according to I. L. Kondakow (Jour. prakt.

Chem., 1899 [2]. 6o, p. 257) are to be regarded as See also:

tertiary esters; a similar type of reaction is found in the See also: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 See also:hydrolysis of the ester prepared by heating menthene with trichloracetic acid (A. Reychler and L. See also:Masson, Ber., 1896, 29, p. 1844). It possesses a faint See also:pepper-See also: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).

End of Article: MONOCYCLIC TERPENE

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