# How does potassium cyanide react with an alkyl halide?

Feb 12, 2017

The cyanide species acts as the nucleophile.

#### Explanation:

And of course the reaction leads (generally) to a $C - C$ bond.

The usual representation of the cyanide ion is as ""^(-):C-=N:, with a formal negative charge on the carbon. Cyanide anion is an excellent nucleophile in circumstances that favour substitution, and $C - C$ bond formation. The elimination of an inorganic metal salt is kinetically and thermodynamically favoured:

RCH_2X + K^(+)""^(-)C-=N rarr RCH_2C-=N+KXdarr

Note that the length of the original carbon chain has been extended by one carbon. Because the nitrile group can be further elaborated, by reduction to give a primary amine for instance, or by hydrolysis to give a carboxyl group, this reaction offers some synthetic utility.