GB1144356A - Process for the manufacture of dicyanobutenes - Google Patents

Abstract

1,144,356. Production of dicyanobutenes. IMPERIAL CHEMICAL INDUSTRIES Ltd. 30 Aug., 1967 [19 Sept., 1966], No. 41719/66. Heading C2C. Dicyanobutenes are continuously prepared by the cyanation of dihalobutenes or halocyanobutenes employing hydrogen cyanide in aqueous solution at elevated temperature at a pH of from 3À5 to 5À5 in the presence of cuprocyanide ion as catalyst, and in the presence of a stabilizer to inhibit the polymerization of #- cyanoprene. The reaction is suitably effected at a temperature of 80-105‹ C. and the hydrogen cyanide may be introduced into the aqueous reaction mixture in the gaseous or liquid state or it may at least in part be generated in situ, e.g. by the addition of sodium cyanide solution. The cuprocyanide ion catalyst may be introduced into the reaction mixture by adding a copper salt which is converted by the hydrogen cyanide in situ to give the cuprocyanide ion; the catalyst is preferably introduced, however, as an aqueous solution of cuprous cyanide in sodium cyanide. The stabilizer, which is preferably volatile, is suitably introduced into the reaction mixture in solution in a suitable solvent, specified stabilizers being phenothiazine, n-butyraldoxime, triethyl phosphite, ammonium N-nitrosophenylhydroxylamine, sodium nitrite, the addition product of di-isobutylene and nitrogen tetroxide, nitroso compounds of the formula R 1 R 2 N.NO, where R 1 and R 2 are alkyl or aryl groups, hydroquinone, t-butyl catechol, picric acid and alkali metal salts thereof, sodium sulphide, organic sulphides and mercaptans, and it is preferred to introduce a small amount of air or oxygen into the reaction mixture at the same time as the stabilizer. Continuous operation of the process is preferably effected by employing a series of reactors deployed in a cascade arrangement.