Question

Explain the following: The C–O bond is much shorter in phenol than in ethanol.

Answer 1

We know that phenol having benzene ring with -OH attached. The oxygen atoms have lone pair which comes in the conjugation with benzene ring and hence, the C-O bond will attains a partial double bond character.
And we know that the ethanol is aliphatic -OH compound and  the C-O bond having single bond character.
And the bond length of double bond is always shorter than the bond length of single bond, so phenol have shorter bond length than ethanol.