Question

Which of the following compound(s) is/are anti-aromatic in nature?

• A.
• B.
• C.
• D.

Answer 1

Answer: (A), (D)

For a compound to be antiaromatic,
(i) It should be cyclic
(ii) It should be planar
(iii) It should have extended conjugation
(iv) It should have (4n) $\pi$ electrons

Compound (a) is cyclic, planar and have extended conjugation with (8) $\pi$ electrons. Thus, it is antiaromatic.

Compound (b) is cyclic, planar and have extended conjugation with (6) $\pi$ electrons which obeys (4n+2) $\pi$ electrons rule. Thus, it is aromatic in nature.
Compound (c) is non-planar so it is a non-aromatic compound.
Compound (d) is cyclic, planar and have extended conjugation with (4) $\pi$ electrons. Thus, it is antiaromatic.
Hence, compound (a) and (d) are antiaromatic.