Question

Which test is used to differentiate between primary, secondary and tertiary amines?

• A. Brady test
• B. Tollen's test
• C. Hinsberg test
• D. Lucas test

Hint:

Think of the reagent benzenesulphonyl chloride, which reacts differently with 1°, 2° and 3° amines.

Answer 1

The Correct Option is C

Step 1: The Hinsberg test uses benzenesulphonyl chloride \( (C_6H_5SO_2Cl) \), the Hinsberg reagent, to distinguish the three classes of amine.
Step 2: A primary amine gives an N-substituted sulphonamide having an acidic N–H that dissolves in aqueous KOH (soluble). A secondary amine gives a sulphonamide with no N–H, so it stays insoluble in KOH. A tertiary amine has no N–H to react and normally does not react at all.
Step 3: These different outcomes (soluble product / insoluble product / no reaction) identify 1°, 2° and 3° amines, so option (iii) is correct.
Step 4: Brady's test (2,4-DNP) and Tollen's test are for carbonyl compounds; Lucas test differentiates alcohols. Hence they are wrong here.