JEE Chemistry 2023 Question with Solution

Given: Isomeric amines with molecular formula $\mathrm{C_8H_{11}N}$ are identified using three qualitative tests.

Find: Which set of structures corresponds to (P), (Q) and (R) respectively.

The solution states that Gabriel phthalimide synthesis is specific to primary amines. Therefore (P) must be a primary amine.

Hinsberg’s reagent gives a solid product insoluble in $\mathrm{NaOH}$ with a secondary amine. Therefore (Q) must be a secondary amine.

Reaction with $\mathrm{HONO}$ followed by $\beta$-naphthol in $\mathrm{NaOH}$ gives a red dye for an aromatic primary amine. Therefore (R) must be an aromatic primary amine.

So the correct option must contain, in order:

1. a primary amine,
2. a secondary amine,
3. an aromatic primary amine.

The provided the solution explicitly concludes:

The Correct Option is D

and also writes Final Answer: (4). Hence the matching option is D.

Therefore, the correct option is D.

Given:

• (P) can be prepared by Gabriel phthalimide synthesis.
• (Q) reacts with Hinsberg’s reagent to give a solid insoluble in $\mathrm{NaOH}$.
• (R) reacts with $\mathrm{HONO}$ and then with $\beta$-naphthol in $\mathrm{NaOH}$ to form a red dye.

Find: The correct ordered set of isomeric amines.

For (P): Gabriel phthalimide synthesis is used for preparing primary aliphatic amines. So the first structure must be a primary amine.

For (Q): In the Hinsberg test, secondary amines form sulfonamides that are insoluble in alkali. So the second structure must be a secondary amine.

For (R): Formation of a red dye after treatment with nitrous acid and coupling with $\beta$-naphthol indicates diazotization followed by azo coupling. This is characteristic of an aromatic primary amine. So the third structure must be an aromatic primary amine.

Comparing these requirements with the options, the solution identifies option (4), which corresponds to D.

Therefore, (P), (Q), (R) are given by option D.