GB285403A - Process for the production of inactive menthol (the racemate of natural menthol) - Google Patents

Abstract

285,403. Rheinische Kampfer-Fabrik Ges. Feb. 15, 1927, [Convention date]. Menthol and its isomers. - i-Neomenthol and i-neoisomenthol are transformed, separately or together, into i-menthol either by (1) treatment with hydrogen at ordinary or increased pressure in the presenoe of a hydrogenation catalyst, (2) heating with the mentholates of the alkali or alkaline earth metals, magnesium or aluminium at temperatures above 100‹ C., or (3) oxidation with chromic acid or treatment with dehydrogenation catalysts, followed by hydrogenation of the resulting i-menthone or i-isomenthone. The neomenthol and neoisomenthol may be obtained by the process of Specification 285,394. The hydrogen treatment may be effected with the addition of i-isomenthol, thymol, i-menthone or i-isomenthone, and the oxidation or dehydrogenation in the presence of i-isomenthol. The reaction product is subjected to freezing-out or fractional distillation or both, and the crude imenthol obtained is purified by conversion into its esters or ester-acids, e.g. of p-nitrobenzoic, carbonic, boric, phthalic or succinic acid, followed by crystallization and saponification (see Specification 289,125). Examples of each of the processes are given. Specifications 213,991, 231,827, and 238.314 are referred to. Mentholates of alkali metals and alkaline earth metals are prepared bv interaction of menthol or its isomers with. the metals or compounds thereof such as the alcoholates or amides; the mentholates of magnesium and aluminium are obtained by the treatment of menthol with the metal alcoholate or amide.