Chemistry - GOC Question with Solution | TestHub

To determine aromaticity, a compound must be cyclic, planar, fully conjugated, and follow Hückel's Rule ($4n+2$$\pi$ electrons).

Aromatic: (a) Cyclopentadienyl anion ($6\pi$ e⁻), (c) Cyclobutadienyl dianion ($6\pi$ e⁻), (d) Cyclobutadienyl dication ($2\pi$ e⁻), (e) Tropylium cation ($6\pi$ e⁻), and (h) Cyclopropenyl cation ($2\pi$ e⁻) all satisfy the $4n+2$ rule.

Not Aromatic: (b), (f), and (g) fail Hückel's rule (they have $4n$ electrons) or, in the case of (f), are non-planar.

Conclusion: Based on these criteria, the correct option is (D).