| 摘要 |
Aliphatic o -cyanocarboxylic acids are prepared by heating an aliphatic o -dicarboxylic acid together with an amount of ammonia equivalent to one carboxyl group or less either as free ammonia or in the form of a substance that splits off ammonia under the reaction conditions, or the monoammonium salt of an aliphatic o -dicarboxylic acid either alone or in the presence of the free acid at 140 DEG to 220 DEG C. until the evolution of gas ceases and then heating the reaction mixture to 240 DEG to 350 DEG C. until the evolution of gas which has recommenced ceases again. The o -cyanocarboxylic acid can be recovered from the reaction mixture by dissolving said mixture in dilute ammonia, extracting the neutral substances therefrom with a water-immiscible organic solvent, subjecting the residual ammoniacal solution to steam distillation, and extracting the cyanocarboxylic acid from the remaining solution by dilution with water or extraction with a water-immiscible organic solvent. The addition to the initial reaction mixture of 5 to 10% by weight of the o -dicarbonitrile corresponding to the o -cyanocarboxylic acid to be produced and based upon the weight of o -dicarboxylic acid present in the starting material either in the free form or as the mono-ammonium salt, is stated to practically completely eliminate the formation of the o -dicarbonitrile as by-product. |
