A butanediol that is butane in which one hydrogen of each of the methyl groups is substituted by a hydroxy group. A colourless, water-miscible, viscous liquid at room temperature (m.p. 16degreeC) with a high boiling point (230degreeC), it is mainly used for the production of other organic chemicals, particularly the solvent oxolane (also known as tetrahydrofuran or THF).