Question

Number of anti aromatic compound in the following compound is______.

Answer 1

Answer: 4

The molecules, which have $4n\pi$ electrons are anti-aromatic compounds.
(a) has $4\pi$-electrons
(b) has $6+2$ (from oxygen atom) $=8\pi$ electrons
(c) has $6\pi$-electrons and one $C$-atom is $s{p}^3$ hybridised hence it is non - aromatic.
(d) is aromatic
(e) has $4\pi$-electrons as available lone pair with $N$ - atom will not be delocalized in this conjugated system.
(f) has $12\pi$-electrons.
Hence, (a), (b), (e) and (f) are anti-aromatic.