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 ( −CN). Reaction of these nucleophiles with an alkyl halide (R&bond;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.