Chemistry - GOC Question with Solution | TestHub

In (a) the C=O polarises to C+ $O^{-}$, and the ring then has the aromatic cyclopropenyl cation (2 π electrons). This dipolar form contributes strongly and the compound is highly stable, so (a) has the larger dipole moment. In (b) the benzophenone C=O gets no such extra stabilisation of the charge-separated form.