How does potassium cyanide react with an alkyl halide?

Question

Ellie Adams · Accepted Answer

The cyanide species acts as the nucleophile.

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 # This reaction offers some synthetic utility because the nitrile group can be further elaborated, for example, by reduction to give a primary amine or by hydrolysis to give a carboxyl group. Note that the original carbon chain has been extended by one carbon.

Ryan Andrews · Answer

undefined Potassium cyanide reacts with alkyl halides in a nucleophilic substitution reaction, replacing the halogen atom with a cyanide ion to form a nitrile compound. The reaction is known as the SN2 reaction (substitution nucleophilic bimolecular). It is generally facilitated by polar aprotic solvents, and the reaction mechanism involves a one-step attack by the cyanide ion on the alkyl halide's carbon, leading to inversion of stereochemistry. This process is highly toxic and poses serious health risks.