Question

Which of the following compounds is not aromatic?

• A.
• B.
• C.
• D.

Answer 1

Answer: (B)

Aromaticity of a compound can be decided by Huckel's rule. In cyclopentadienyl cation (b), resonance takes place as follows:

Huckel's rule as it has conjugated $4\pi$-electron $(4n\pi ,n=1)$ system. Rest of the species are aromatic as each of them belongs to $6\pi$-electron $[(4n+2)\pi ,n=1]$ system.