A = Planar ring, all atoms of the ring sp2 hybridised, has six delocalised $\pi$-electrons, follows Huckel rule. It is aromatic. B = Has six $\pi$-electrons, but the delocalisation stops at sp3 hybridised CH2- carbon. Hence, not aromatic. C = Six delocalised $\pi$-electrons (4$\pi$ electrons +2 unshared electrons on negatively charged carbon) in a planar ring, follows Huckel’s rule. It is aromatic. D = Has only four delocalised $\pi$-electrons. It is non aromatic. E = Six delocalised $\pi$-electrons follows Huckel’s rule. $\pi$-electrons are in sp2 hybridised orbitals, conjugation all over the ring because of positively charged carbon. The ring is planar hence is aromatic. F = Follows Huckel’s rule, has $2\pi$ electrons i.e. (4n + 2) $\pi$-electrons where (n = 0), delocalised $\pi$-electrons. It is aromatic. G = $8\pi$ electrons, does not follow Huckel’s rule i.e., (4n + 2) $\pi$-electrons rule. It is not aromatic.
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