Chemistry - GOC Question with Solution | TestHub

The $\mathrm{C}=\mathrm{O}$ bond is polarised (${\mathrm{C}}^{+}-{\mathrm{O}}^{-}$), so the ring has 2 $\mathrm{C}=\mathrm{C}$ (4π) with an empty p orbital on the cationic carbon : 4π = 4n (n = 1). Anti-aromatic.