Account for the following : Although amino group is o- and p- directing in aromatic, electrophilic substitution reactions, aniline on nitration gives a substantial amount of m-nitroaniline.

Account for the following : Although amino group is o- and p- directi

1.	Account for the following : Although amino group is o- and p- directing in aromatic, electrophilic substitution reactions, aniline on nitration gives a substantial amount of m-nitroaniline.
Answer» Solution :Nitration is usually carried out with a mixture of conc. `HNO_(3)` + conc. `H_(2)SO_(4)`. In presence of these acids, aniline gets protonated to form anilinium ION. Therefore, in presence of acids, the reaction mixture consists of aniline and anilinium ion. While `-NH_(2)` group in aniline is o, p-directing and activating, the `NH_(3)` group in anilinium ion is m-directing and deactivating. Now nitration of aniline mainly gives p-nitroaniline DUE to steric hindrance at o-position, the nitration of anilinium ion givesm-nitroaniline. In actual PRACTICE, approx. a 1 : 1 mixture of p-nitroaniline and m-nitroaniline is obtained, as per the reactions given below :