What is the role of the -NH₂ group in aniline in electrophilic substitution reactions, and where is the maximum electron density located in its resonance hybrid structures?

The -NH₂ group in aniline plays a crucial role in electrophilic substitution reactions. The amino group is an ortho-para director, meaning it directs incoming electrophiles to the ortho and para positions of the aromatic ring. This directing effect is due to resonance stabilization. In aniline’s resonance hybrid structures, the maximum electron density is located on the ortho and para positions of the ring. The lone pair on the nitrogen atom is involved in resonance, contributing to the electron density in these positions. This directing effect influences the regioselectivity of electrophilic aromatic substitution reactions involving aniline.