The reaction of an alkyl halide with sodium alkoxide to form an ether is known as the Williamson ether synthesis.

Reaction: $R-X + R'-ONa \rightarrow R-O-R' + NaX$

This reaction involves the nucleophilic substitution of the halide ion from the alkyl halide by the alkoxide ion. It is an important laboratory method for the preparation of symmetrical and unsymmetrical ethers.