Question

Indicate whether or not each of the following structures is considered to be aromatic.

Answer 1

ans) B is aromatic, A is not.

Answer 2

B is Aromatic, A is not. This is because in structure B, it has 2e- which is delocalized over the complete ring and follows huckel rule of e- of (4n+2) for n=0. Also B is planar structure. And the resonating structures are formed by complete delocalization of e- over the ring.

In A, however it has 6e- and follows huckel rule of (4n+2) for n=1, but since the e- doesn't delocalize completely over the ring it cannot be classified as aromatic compound.