In which of the following compounds is the lone pair of electrons on the nitrogen atom an essential part of the aromatic -electron system?

Step-by-step solution

To determine if the lone pair is part of the aromatic system, we must check if it is required to satisfy Hückel's rule ( 4n+2 electrons). 1. Pyridine: The ring already contains 6 electrons from its three double bonds. The nitrogen atom is sp^2 hybridized, and its lone pair resides in an sp^2 orbital orthogonal to the system. It is not part of the aromatic sextet. 2. Aniline: The benzene ring is inherently aromatic with 6 electrons. Although the nitrogen lone pair can delocalize into the ring via resonance, it is no