HYDROCARBONS  , CtoH18, OF THE TERPENE

SERIES Menthene, C,H,(CH3) (C3Hr)', is methyl-i-isopropyl-4-cyclohexene-3 . It is obtained by the action of anhydrous zinc chloride or copper sulphate on menthol (J . W . Brfihl, Ber., 1892,• 25, Q . 142), by boiling menthyl chloride with aniline (G . Wagner, Ber., 1894, 27, p . 1636), by heating menthyl chloride with potassium phenolate (L . Masson, Ber., 1896, 29, p . 1843), and by the dry distillation of the methyl ester of menthyl xanthate (L . Tschugaeff, Ber., 1899, 32, p . 3333) . It is a colourless liquid which boils at 167-168° C .

When strongly heated with copper sulphate it yields cymene . According to Tschugaeff, the xanthate method alone gives a pure menthene of the above constitution, the menthene obtained from the dehydration of menthol being a cyclohexene-4; and the one obtained by 0 . Wallach (

Ann., 1898, 300, p . 278) from 1-menthylamine being a cyclohexene-2 . Carvomenthene, C6H3(CH3)(C3H7), is probably methyl- l-isopropyl-4-cyclohexene-I . It is prepared by heating carvomenthyl bromide with quinoline, or by heating carvomenthol with potassium bisulphate to 200° C . It is a liquid which boils at 175-176° C . Cam phone, C;H9(CH3)2 is 1.7.7-trimethyl-bicyclo-(r•2 . )-heptane . It is prepared by the action of sodium and alcohol on pinene hydriodide, or by reducing the hydriodide with zinc in acetic acid solution . It is a crystalline solid which melts at 153° C. and boils at 160° C .