The dichlorobutcnes are then reacted with HCN or an alkali cyanide in the liquid phase at 80 OC to butenedinitriles. The formation of 3,4-dicyano-l -butene is not disadvantageous since, in the presence of the copper-cyano complex, an ally1 rearrange- ment takes place under the hydrocyanation conditions. A mixture of the cis/truns isomers of 1,4-dicyano-2-butene is obtained with about 95% selectivity: