Why acetic acid is stronger than phenol?

On acetic acid, the carbon in the carboxylic acid group is highly electron-starved: that carbon is bonded to oxygen atoms 3 times! Moreover, that carbon only has one methyl group from which to "take" electrons in order to fill the charge imbalance. This means that the only easy electrons the acidic oxygen on the carboxylic acid group can access is the one on the hydrogen. This makes the O-H bond more ionic in character, and so easy to dissociate in water. On phenol, the carbon in the hydroxyl group is not electron-starved. Since it is part of an electron-rich aromatic ring, it is a "channel" through which the oxygen atom can access electrons - this lucky oxygen atom can access 6 electrons that are delocalized over 6 carbon atoms in order to satisfy its hunger for negative charges. This means that the O-H bond in question is more covalent in character, and more difficult to dissociate in solution.

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