Question

The reagent which is used to distinguish primary, secondary and tertiary amines from the mixture is

• A. Fehling's reagent
• B. Tollens reagent
• C. Lucas reagent
• D. Hinsberg's reagent

Hint:

Summarize the Hinsberg Test: - 1° Amine: Reacts, product is soluble in alkali. - 2° Amine: Reacts, product is insoluble in alkali. - 3° Amine: Does not react. This clear difference in reactivity and solubility is the basis of the test.

Answer 1

The Correct Option is D

Step 1: Identify the Reagent: Hinsberg's reagent is Benzenesulfonyl chloride (\( \text{C}_6\text{H}_5\text{SO}_2\text{Cl} \)). It reacts differently with amines:
Step 2: Reaction with Amines: - Primary Amine ($1^\circ$): Reacts to form N-alkylbenzenesulfonamide. The product has an acidic hydrogen attached to nitrogen, so it is soluble in alkali (NaOH). - Secondary Amine ($2^\circ$): Reacts to form N,N-dialkylbenzenesulfonamide. The product has no acidic hydrogen, so it is insoluble in alkali. - Tertiary Amine ($3^\circ$): Does not react with Hinsberg's reagent (no H on nitrogen). The amine remains insoluble (or soluble in acid).
Step 3: Conclusion: Because of these distinct observations (soluble product, insoluble product, no reaction), Hinsberg's reagent is the standard method to distinguish and separate the three classes of amines.