The carbon - oxygen bond in phenol is slightly stronger than that in methanol. Why?

Explanation

This can be explained as under :
(i) Phenol, the conjugation of unshared electron pair over oxygen with aromatic ring results in partial double bond character in `C-O` bond.

In methanol, no such conjugation (resonance) is possible.
(ii) In phenol, oxygen is attached to `sp^(2)` hybridised carbon while in methanol, oxygen is attached to `sp^(3)` hybrised carbon. An `sp^(2)` hybridised carbon is more electronegative (because of greater s - character) than `sp^(3)` hybridised carbon atom. Therefore, the bond between oxygen and `sp^(2)` hybridised carbon is more stable than the bond between oxygen and `sp^(3)` hybridised orbital.