GB456533A - Improvements in or relating to the manufacture of unsaturated organic compounds - Google Patents

Abstract

Unsaturated amides are manufactured by heating a mixture of a ketone cyanhydrin with sulphuric acid, oleum or an alkylsulphuric acid, or mixtures thereof, preferably in the molecular proportion of 1--2 of acid to one of cyanhydrin, to 140--180 DEG C. for a period of time not substantially exceeding 10 minutes, preferably between \ba1/4\be minute and 5 minutes. The reaction may be effected continuously by introducing the reactants into a mixing vessel from which they are fed at a suitable rate through a reaction zone at 140--180 DEG C., e.g. through a coil heated in an oil bath or over a heated metal drum. The cyanhydrins may be those of ketones of the general formula R1COCHR2R3, where R1 is an organic radicle, R2 and R3 are organic radicles, hydrogen or p halogen, or of carbocyclyc compounds containing the group --CO--CH =. Inert diluents may be added to the cyanhydrin prior to admixture with the acid, and antipolymerization catalysts, e.g. copper, sulphur or hydroquinone, may be added to the reaction mixture. The mixing of the reactants is preferably effected at an elevated temperature, e.g. about 80 DEG C., preferably in a vessel furnished with means for controlling the temperature, e.g. a cooling device. The reaction mixture may be worked up for the isolation of the unsaturated amide, or for conversion to the corresponding acid or ester. In examples: (1) crude acetone cyanhydrin is mixed with sulphuric acid (0,2 per cent free SO3) at 85--100 DEG C. and the mixture is passed with a transit time of 130 seconds through a coil immersed in an oil bath at 150 DEG C., yielding methacrylamide; (2) methyl ethyl ketone cyanhydrin is mixed with sulphuric acid at 85 DEG C. and the mixture is treated as in (1) at 160 DEG C. for 187 seconds, producting a -methylcrotonamide; (3) in the process of (1) the mixing temperature is 80--85 DEG C. and the beating is effected at 160 DEG C. with a transit time of 59 seconds; (4) crude cyclohexanone cyanhydrin is mixed with sulphuric acid at 80--90 DEG C. and the mixture is treated as in (1) at 170 DEG C. for 89 seconds, yielding cyclohexane-1-carboxylic amide; (5) crude acetone cyanhydrin is mixed with sulphuric acid at 80--85 DEG C. and the mixture is passed through a coil as in (1); a table gives the yields obtained at temperatures ranging from 140--180 DEG C. and transit times of 16--279 seconds. Specifications 405,699 and 446,908 are referred to.