JEE Main · 2022 · 29 Jun 2022 · Shift 2 · Hydrocarbons

In Friedel-Crafts alkylation, the Lewis acid catalyst (like ${\mathrm{AlCl}}_3$) coordinates with the lone pair on the nitrogen of aniline, forming a positively charged nitrogen species: ${\mathrm{C}}_6{\mathrm{H}}_5-\stackrel{+}{\mathrm{N}}{\mathrm{H}}_2-{\mathrm{AlCl}}_3$. This positively charged nitrogen is a strong meta-directing deactivating group, which prevents the Friedel-Crafts reaction from proceeding normally. The amino group becomes protonated/complexed and the ring becomes too deactivated for electrophilic substitution. Therefore, Friedel-Crafts alkylation does not work well with aniline, and what you get is a positively charged nitrogen attached to the benzene ring.