Nomenclature and structure

Common names of alcohols add 'alcohol' to the alkyl name (methyl alcohol). IUPAC names replace the final 'e' of the parent alkane by 'ol' and give the –OH carbon the lowest possible number: CH₃CH(OH)CH₃ is propan-2-ol.

IUPAC names with their common names: butan-1-ol (n-butyl alcohol); butan-2-ol (sec-butyl alcohol); 2-methylpropan-1-ol (isobutyl alcohol); 2-methylpropan-2-ol (tert-butyl alcohol); ethane-1,2-diol (ethylene glycol); propane-1,2,3-triol (glycerol).

For polyhydric alcohols the 'e' of the alkane is kept and di, tri and so on are placed before 'ol'. Cyclic alcohols take the prefix cyclo, as in cyclohexanol and 2-methylcyclopentanol, with the –OH carbon numbered 1.

Hydroxybenzene is simply called phenol, and this is also its accepted IUPAC name. The methylphenols are the cresols (2-, 3- and 4-methylphenol); benzene-1,2-diol, 1,3-diol and 1,4-diol are catechol, resorcinol and hydroquinone (quinol).

Common names of ethers list the two groups in alphabetical order followed by 'ether' (ethylmethyl ether); with two identical groups the prefix di is used (diethyl ether). IUPAC names treat the ether as a hydrocarbon with an alkoxy or aryloxy substituent, the larger group being the parent.

Ether name pairs: dimethyl ether = methoxymethane, diethyl ether = ethoxyethane, anisole = methoxybenzene, phenetole = ethoxybenzene, phenyl isopentyl ether = 3-methylbutoxybenzene; CH₃OCH₂CH₂OCH₃ is 1,2-dimethoxyethane.

In alcohols the oxygen is sp³ hybridised with two lone pairs. Lone-pair repulsion squeezes the C–O–H angle to slightly below the tetrahedral 109°28′.

In phenols the C–O bond is 136 pm, shorter than in an alcohol, because the oxygen lone pair is shared with the ring (partial double-bond character) and the carbon is sp² hybridised.

In ethers the two bulky groups push apart, so the C–O–C angle is slightly larger than tetrahedral; the C–O bond length (141 pm) is close to that in alcohols.