JEE Main · 2021 · 18 Mar 2021 · Shift 2 · Compounds Containing Nitrogen

Benzene sulphonyl chloride reacts with primary and secondary amines but leaves tertiary amines untouched, since a tertiary nitrogen has no hydrogen to replace. A primary amine gives a sulphonamide that still carries one hydrogen on nitrogen, and the electron-withdrawing sulphonyl group makes that hydrogen acidic, so the product dissolves in dilute alkali as its sodium salt. A secondary amine gives a sulphonamide with no hydrogen left on nitrogen, which stays insoluble in alkali. A product soluble in dilute sodium hydroxide therefore comes from a primary amine, and the only primary amine among the structures offered is 1-phenylethanamine, ${\mathrm{C}}_6{\mathrm{H}}_5\mathrm{CH}(\mathrm{C}{\mathrm{H}}_3)\mathrm{N}{\mathrm{H}}_2$.