Question

How does potassium cyanide react with an alkyl halide?

Answer 1

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.