32.2.4—Acidities of water, phenol and ethanol

The relative acidity is phenol > water > ethanol. Phenoxide is stabilised by delocalisation, whereas hydroxide and ethoxide keep the negative charge mainly on oxygen; the ethyl group also pushes electron density towards oxygen.

Use conjugate-base stability rather than the number of hydrogens to compare acidity. All three are weak acids in water, but their equilibria differ.

Phenol reacts with aqueous hydroxide, while ethanol does not react appreciably with aqueous hydroxide because hydroxide is not strong enough to remove its proton under those conditions.

Phenol being “weak” does not make it less acidic than ethanol; weak acids can still have a clear relative order.