JEE Main · 2023 · 10 Apr 2023 · Shift 1 · Compounds Containing Nitrogen

The Gabriel phthalimide synthesis gives only primary amines that are not joined directly to an aromatic ring, so isomer P must be a primary aliphatic amine, here 2-phenylethylamine. Isomer Q, on treatment with Hinsberg's reagent, gives a sulfonamide that remains a solid insoluble in alkali, which is the behaviour of a secondary amine, so Q is the secondary amine of the set. Isomer R reacts with nitrous acid to form a stable diazonium salt that couples with beta-naphthol in alkali to give a red azo dye, a test characteristic of an aromatic primary amine, so R is the aryl amine. The set in which P is the primary aliphatic amine, Q the secondary amine and R the aromatic primary amine is the correct one.