JEE Main · 2021 · 27 Aug 2021 · Shift 2 · Compounds Containing Nitrogen

Catalytic hydrogenation with ${\mathrm{H}}_2/Pd$ reduces the nitro group of $p$-nitrophenol to an amino group, giving $p$-aminophenol as A while the phenolic $-\mathrm{OH}$ is left intact. With one equivalent of acetic anhydride the more nucleophilic $-\mathrm{N}{\mathrm{H}}_2$ is acetylated in preference to the phenolic $-\mathrm{OH}$, so B is $N$-(4-hydroxyphenyl)acetamide (paracetamol), whose ring $-\mathrm{OH}$ remains free. A is $p$-aminophenol and B is $N$-(4-hydroxyphenyl)acetamide.