Chemistry - GOC Question with Solution | TestHub

The $\mathrm{C}=\mathrm{O}$ polarises (C+ ${\mathrm{O}}^{-}$). The ring then has one $\mathrm{C}=\mathrm{C}$ = 2 π electrons plus an empty p orbital on the cationic carbon, which is the cyclopropenyl cation. The exocyclic $\mathrm{C}=\mathrm{O}$ π bond is not counted. Aromatic.