JEE Main · 2021 · 24 Feb 2021 · Shift 1 · Hydrocarbons

Aniline ($\mathrm{C}{}_6\mathrm{H}{}_5\mathrm{NH}{}_2$) normally has an amino group ($-\mathrm{NH}{}_2$) which is a strong ortho-para directing group due to its +M (mesomeric) effect. However, during nitration, the reaction is carried out in acidic medium (using $\mathrm{HNO}{}_3/\mathrm{H}{}_2\mathrm{SO}{}_4$).

In this acidic medium, the amino group gets protonated to form the anilinium ion ($\mathrm{C}{}_6\mathrm{H}{}_5\mathrm{NH}{}_3{}^{+}$). The $-\mathrm{NH}{}_3{}^{+}$ group is electron-withdrawing due to its positive charge and acts as a meta-directing group through its -I (inductive) effect.

Therefore, along with the expected ortho and para products, a significant amount of meta-nitro product is also formed due to the formation of the anilinium ion in the acidic reaction conditions.