Kolbe nitrile synthesis

The Kolbe nitrile synthesis is a method for the preparation of alkyl nitriles by reaction of the corresponding alkyl halide with a metal cyanide. A side product for this reaction is the formation of an isonitrile because the cyanide ion is an ambident nucleophile. The reaction is named after Hermann Kolbe.



The ratio of product isomers depends on the solvent and the reaction mechanism, and can be predicted by Kornblum's rule. With the Using alkali cyanides such as sodium cyanide and polar solvents, the reaction occurs by an SN2 mechanism via the more-nucleophilic carbon atom of the cyanide ion.

This type of reaction together with dimethyl sulfoxide as a solvent is a convenient method for the synthesis of nitriles. The use of DMSO was a major advancement in the development of this reaction, as it works for more sterically hindered electrophilies (secondary and neopentyl halides) without rearrangement side-reactions.