Question

Which of the following is non-aromatic in nature?

• A.
• B.
• C.
• D.

Answer 1

Answer: (B)

a. $10\pi {\bar{e}}^{\prime }s$ in delocalisation $\Rightarrow$ Aromatic
b. $10\pi {\bar{e}}^{\prime }$ sin delocalisation, but is non-aromatic because ring is non-planar, as the $H$ atoms that point to the interior to the ring interfere with each other
Note: Annulene with $10C$ and $14C$ are $n$ on - aromatic, but dehydro [10] and [14] annulenes are aromatic

in delocalisation (only one lone pair is delocalised) $\Rightarrow$ Aromatic

in delocalisation $\Rightarrow$ Aromatic