Aniline reacts with concentrated sulfuric acid to form anilinium hydrogensulphate, which, upon heating, produces p-aminobenzene sulphonic acid (sulphanilic acid) as the major product at 453-473K.

Direct nitration of aniline yields tarry oxidation products alongside nitro derivatives. In strongly acidic conditions, aniline forms the anilinium ion, which is meta-directing. Acetylation of the -NH₂ group can control nitration, favoring the formation of the p-nitro derivative as the ...

Acetylation with acetic anhydride protects the -NH₂ group in aniline during electrophilic substitution, and the resulting -NHCOCH₂ group has a less activating effect due to resonance interactions that make the lone pair on nitrogen less available for donation to the ...

Aromatic amines, like aniline, exhibit very high reactivity in electrophilic substitution, favoring ortho- and para-positions. To control the activating effect of the -NH₂ group for monosubstitution, acetylation with acetic anhydride can be performed, followed by desired substitution and hydrolysis of ...

The -NH₂ group in aniline is ortho- and para-directing, making these positions centers of high electron density in its resonance hybrid structures.