The extent of intramolecular hydrogen bonding between hydroxyl groups and ring oxygens, as determined by infra-red spectroscopy in the hydroxyl stretching region, in a series of monohydroxy derivatives of tetrahydropyran, tetrahydrofuran and 1:3-dioxan provides direct experimental evidence for the stabilities of different conformations of certain of the alcohols. The synthesis of tetrahydropyran-3-ol