Nucleophilic Substitution Reactions

Alkyl halides undergo many reactions in which a nucleophile displaces the halogen atom bonded to the central carbon of the molecule. The displaced halogen atom becomes a halide ion.

Some typical nucleophiles are the hydroxy group (−OH), the alkoxy group (RO−), and the cyanide ion (−C N). Reaction of these nucleophiles with an alkyl halide (R—X) gives the following reactions and products: 

The halogen ion that is displaced from the carbon atom is called the leaving group, and the overall reaction is called a nucleophilic substitution reaction