Chemistry - GOC Question with Solution | TestHub

In (a) cyclopentadienone the polar ${\mathrm{C}}^{+}-{\mathrm{O}}^{-}$ form gives a 4π anti-aromatic ring. In (b) tropone the polar form gives a 6π aromatic tropylium oxide ring, so (b) has the larger resonance energy. So a $<$ b.