GB446908A - Manufacture of unsaturated organic compounds - Google Patents

Abstract

Unsaturated amides, acids or esters are manufactured by heating a ketone cyanhydrin other than acetone cyanhydrin with sulphuric acid, oleum or an alkyl sulphuric acid, preferably at about 80--100 DEG C., and, if desired, heating the reaction mixture with water or an alcohol or both. Suitable cyanhydrins are those of ketones of the general formula <FORM:0446908/IV/1> where R1 is an organic radicle, R2 is an organic radicle, hydrogen or a halogen, and R3 is an organic radicle, a halogen or, when R1 is not a methyl group, hydrogen, or in which, when R2 is hydrogen, R1 and R3 are joined in a polymethylene ring; e.g. symmetrical or unsymmetrical alkyl and aralkyl ketones such as diethyl, methyl ethyl, dibenzyl, methyl benzyl and higher ketones, substituted bodies such as symmetrical dichloracetone, or cyclohexanone. The cyanhydrins are prepared by the action of hydrocyanic acid on the ketone, and may be used in the crude state. The molecular proportion of acid to cyanhydrin is preferably about 1--1\ba1/2\be : 1, whilst for the esterification step it is desirable to use at least 1\ba1/2\be molecular proportions of alcohol to one of the original cyanhydrin. Suitable alcohols are mono- and dihydric alcohols, e.g. methyl, ethyl, propyl, butyl, amyl and benzyl alcohols, cyclohexanol, ethylene glycol and its monoacetate and ethylene chlorhydrin. Both steps of the reaction are advantageously effected in the presence of an antipolymerizing agent, e.g. copper or bronze powder, sulphur, diphenylamine, hydroquinone, pyrogallol, tannic acid or resorcinol. In examples: (1) methyl ethyl ketone cyanhydrin is heated with sulphuric acid in the presence of powdered copper and the product is refluxed with water and ethyl alcohol, producing the ethyl esters of the stereoisomeric a -methylcrotonic acids, together with the free acids; (2) the ethyl alcohol is replaced by methyl alcohol, yielding, in addition to pentenic acids, the methyl esters of a -ethylacrylic, angelic and tiglic acids; (3) methyl isobutyl ketone cyanhydrin is reacted as in (2) to produce the amide and methyl ester of a -methyl-b -isopropylacrylic acid; (4) chloroacetone cyanhydrin is heated with sulphuric acid in the presence of copper and the resulting amide is refluxed with water and methyl alcohol, producing methyl a -methyl-b -chloracrylate; (5) cyclohexanone cyanhydrin (prepared from cyclohexanone and hydrocyanic acid in the presence of piperidine) is heated with 0,8 per cent oleum in the presence of copper bronze and the product is refluxed with water and methyl alcohol to yield methyl cyclohexene-1-carboxylate; (6) acetophenone cyanhydrin is heated with sulphuric acid in the presence of copper and the product is refluxed with water and ethyl alcohol, producing ethyl atropate and atropic acid; (7) methyl isobutyl ketone cyanhydrin is heated with sulphuric acid in the presence of copper and the product is refluxed with water and methyl alcohol, yielding heptenic acids, their methyl esters, mainly methyl a -methyl-b -isopropylacrylate, and some amide; (8) cyclohexanone cyanhydrin is heated with sulphuric acid in the presence of copper and the product is refluxed with water to produce cyclohexene-1-carboxylic acid; (9) methyl n-hexyl ketone cyanhydrin is heated with sulphuric acid in the presence of copper and the product is heated with water and methyl alcohol, yielding a -methyl-b -n-amylacrylic acid, its methyl ester and amide; (10) a -methylcrotonic acid is prepared from methyl ethyl ketone cyanhydrin and is esterified with ethylene glycol; (11) methyl ethyl ketone cyanhydrin is heated with sulphuric acid and the product is treated with water and benzyl alcohol to produce benzyl a -methylcrotonate and a -methylcrotonic acid. Specification 405,699 is referred to.