The Kolbe nitrile synthesis is a method for the preparation of alkyl nitriles by reaction of the corresponding alkylhalide with a metal cyanide. A side product for this reaction is the formation of an isonitrile because the cyanide ion is an ambident nucleophile and according to Kornblum's rule is capable of reacting with either carbon or nitrogen. The reaction is named after Hermann Kolbe.The ratio in which both isomers form depends on the solvent and the reaction mechanism.