GB639438A - Preparation of organic nitriles - Google Patents

Abstract

Nitriles having the unit <FORM:0639438/IV (b)/1> are prepared by heating a halide possessing the unit <FORM:0639438/IV (b)/2> , where X is chlorine or bromine, with hydrogen cyanide or an alkali metal cyanide or an alkaline earth metal cyanide in an aqueous acid medium, the reactant cyanide acting also as an acceptor for hydrogen halide. Any acid, e.g. sulphuric or oxalic, may be added. The initial halides may be alicyclic, e.g. 1 : 4-dichloro-2-cyclopentene, heterocyclic, e.g. 2 : 5-dichloro-2 : 5-dihydrofuran, or of the type R1R2C = CR3.CH2X or R1R2CX.CR3 = CH2, where R1 is alkyl, alkenyl, chloroalkyl or cyanoalkyl, R2 and R3 are hydrogen or methyl, being the same or different, or the following: benzyl chloride, benzal dichloride, benzotrichloride, triphenylmethyl chloride, phenallyl chloride, a -vinyl allyl chloride and g -dichloroallyl chloride; the halide preferably contains 4-10 carbon atoms. Usually a substantial excess of cyanide is added, the pH is kept below 3, and the temperature is in the range 50-180 DEG C.; cooling is often necessary. Lower temperatures favour the formation of chloro-nitriles from dichloro-compounds. Catalysts such as copper, copper or cobalt salts and potassium ferricyanide may be used. The water content of the reaction medium is preferably 0.2 to 10 times the weight of CN residues present. The reactants may be emulsified, or an inert miscible or immiscible diluent may be used. In the examples: (1)-(3), (5), (7) and (11) 1 : 4-dichloro-2-butene is treated with hydrogen cyanide, or sodium or calcium cyanide, under a variety of conditions to give 1 : 4-dicyano-2-butene, also prepared (6) from 3 : 4-dichloro-1-butene in a similar way (some chloro-nitriles are formed in most cases); (4) 3-chloro-1-butene treated with hydrogen cyanide gives crotyl cyanide; (8), (9) and (12), allyl bromide, isobutenyl chloride and 2-chloromethylthiophene are treated with sodium cyanide to give the corresponding nitriles.