Williamson, Alexander William (1824–1904)

English organic chemist who made significant discoveries concerning alcohols and ethers, catalysis, and reversible reactions. He was the first to explain the action of a catalyst in terms of the formation of an intermediate compound.

Williamson was born in London and studied at several European universities. He was professor at University College, London, 1849–87.

Williamson was the first to make ‘mixed’ ethers, with two different alkyl groups, and his method is still known as the Williamson synthesis. It involves treating an alkoxide with an alkyl halide (haloalkane).

Some of the reactions of alcohols and ethers are reversible (that is, the products of a reaction may recombine to form the reactants), a phenomenon first noted and described by Williamson in the early 1850s. If the rate of the forward reaction is the same as that of the reverse reaction, all compounds in the process coexist and the system is said to be in ‘dynamic equilibrium’ (a term also introduced by Williamson).