Why are carboxylic acids more acidic than alcohols?
Carboxylic acids are stronger acids than alcohols primarily due to the stability of the resulting anion after the loss of a proton.
When an alcohol donates a proton, it forms an alkoxide ion (), which has only one possible structure. In contrast, when a carboxylic acid donates a proton, it forms a carboxylate ion (). This ion is significantly more stable because of resonance, a phenomenon where valence electrons are delocalized across multiple atoms.
Because two resonance structures can be drawn for the carboxylate ion, the negative charge is dispersed rather than concentrated on a single oxygen atom. Since the stability of an anion directly determines the strength of its parent acid, the resonance-stabilized carboxylate ion makes the carboxylic acid a much stronger acid than the corresponding alcohol.1