In which case is the indicated unshared pair of electrons NOT a contributor to the $\pi$ aromatic system?

Question

Quizplus · Accepted Answer

In option B, the unshared pair of electrons is not part of the aromatic system as it is in a sp3 hybridized orbital and is not participating in the delocalization of electrons within the aromatic ring. In options I, III, and IV, the unshared pair of electrons is in a p orbital and is part of the delocalized π electrons of the aromatic system. Therefore, only option B does not contribute to the aromatic system.

In Which Case Is the Indicated Unshared Pair of Electrons π\piπ

In Which Case Is the Indicated Unshared Pair of Electrons $\pi$