33.1.4—Acidities of carboxylic acids, phenols
- Syllabus
- 9701–2028–2029
- Objective
- 33.1.4
- Level
- A2
Carboxylic acids are more acidic than phenols, which are more acidic than alcohols
The relative acidity is carboxylic acid > phenol > alcohol. Carboxylate ions delocalise negative charge over two oxygens; phenoxide delocalises into the ring; alkoxides localise charge on one oxygen.
Compare conjugate-base stability and electron-donating or withdrawing substituents, not just the O–H bond itself.
A carboxylic acid reacts with aqueous carbonate to release CO₂; phenol is too weak for this under ordinary conditions, and ethanol is weaker still.
All three can donate H⁺, but “weak acid” is relative: a weak acid can still be substantially stronger than another weak acid.
ConceptA-Level CAIE Chemistry A2