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Julia Ames

Why are carboxylic acids more acidic than phenol?

Christine EveningsFall  Follow

Yes, carboxylic acids are more acidic than phenols. The more stable the conjugate base of the acid, the stronger the acid will be.

The conjugate base of carboxylic acid is a carboxylate ion. Since the negative charge on the [math]O^-[/math] ion is spread across two highly electronegative O atoms via resonance (p-orbital overlap of O=C-O), the negative charge is much more dispersed, hence the conjugate base is more stable.

The conjugate base of phenol is phenoxide. However, the negative charge delocalizes into the benzene ring to a smaller extent via resonance, than the benzene ring is electron donating to the [math]O^-[/math] ion via induction. All things considered, the negative charge on [math]O^-[/math] is intensified and the conjugate base of phenol is less stable.

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Connor Becz  Follow

The carboxylate ion is more stabilised than phenoxide ion, so carboxylic acids are more acidic than phenols. The conjugate base of carboxylic acid, a carboxylate ion, is stabilised by two equivalent resonance structures in which the negative charge is at the more electronegative oxygen atom.

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