Question

Identify the aromatic compound?

• A.
• B.
• C.
• D. None of the these

Answer 1

The correct option is B

(a) The molecule is a cyclic, planar conjugated molecule having 12 $\pi$-electrons. Hence it is not an aromatic compound.

(b)

Neither cycloheptatriene nor cyclopentadiene alone is aromatic but resonance structure bears a positive charge in the seven-membered ring, giving it an aromatic character of cycloheptatrienyl cation, while the five membered ring bears a negative charge making it similar to the aromatic cyclopentadienyl anion. This charge separation is responsible for the observed dipole moment. Moreover, it is a cyclic, planar conjugated molecule with 10 $\pi$-$e^{-}$. Therefore, it is an aromatic compound.

(c) The molecule is cyclic, planar conjugated molecule having 8 $\pi$-$e^{-}$ $\left(4n\right)\pi e^{-}$ Therefore, it is anti-aromatic compound.

Hence option (b) is the correct answer.