Which of the following reagent is used in Hinsberg test of amines?

\(C_6H_5SO_2Cl\) in aq. \(NaOH\)

The correct answer is option 2. \(C_6H_5SO_2Cl\) in aq. \(NaOH\).

The Hinsberg test is a qualitative test used to distinguish between primary, secondary, and tertiary amines based on their reactivity with benzenesulfonyl chloride \((C_6H_5SO_2Cl)\). Here’s a detailed explanation of the test and the reagents involved:

Principle of the Hinsberg Test:

Reaction with Benzenesulfonyl Chloride:

Benzenesulfonyl chloride is a sulfonylating reagent that reacts with amines to form sulfonamides. The solubility of these sulfonamides in different solvents can help differentiate between primary, secondary, and tertiary amines.

Chemical Reactions:

Primary Amines:

Primary amines react with benzenesulfonyl chloride to form a sulfonamide that is soluble in alkali solutions (basic conditions). The reaction produces a benzenesulfonamide derivative of the primary amine.

Example reaction:

\(RNH_2 + C_6H_5SO_2Cl \rightarrow RNH-SO_2-C_6H_5 + HCl\)

where \(RNH-SO_2-C_6H_5\) is the sulfonamide derivative.

Secondary Amines:

Secondary amines also react with benzenesulfonyl chloride, but the resulting sulfonamide is generally insoluble in alkaline solutions.

Example reaction:

\(R_2NH + C_6H_5SO_2Cl \rightarrow R_2N-SO_2-C_6H_5 + HCl\)

Tertiary Amines:

Tertiary amines do not react with benzenesulfonyl chloride under these conditions because they lack the hydrogen atom required for the formation of the sulfonamide. Therefore, tertiary amines will not produce a sulfonamide derivative.

Testing Process:

A sample of the amine is treated with benzenesulfonyl chloride in the presence of an aqueous sodium hydroxide solution. The resulting product is then analyzed:

If a solid sulfonamide forms and is insoluble in aqueous sodium hydroxide, the amine is a secondary amine.

If a solid sulfonamide forms and is soluble in aqueous sodium hydroxide, the amine is a primary amine.

If no reaction occurs, the amine is a tertiary amine.

Reagents Used in the Hinsberg Test:

Benzenesulfonyl Chloride \((C_6H_5SO_2Cl)\):

This is the key reagent that reacts with amines to form sulfonamides. The solubility of these sulfonamides in basic solutions is crucial for distinguishing between the different types of amines.

Aqueous Sodium Hydroxide \((NaOH)\):

Sodium hydroxide is used to create a basic environment in which the solubility of the sulfonamide derivatives can be tested.

Analysis of Options:

1. \((CH_3CO)_2O\) and pyridine: These are used in the acetylation test to identify and differentiate amines based on their reaction with acetic anhydride, not in the Hinsberg test.

2. \(C_6H_5SO_2Cl\) in aqueous \(NaOH\): This reagent is used in the Hinsberg test for differentiating primary, secondary, and tertiary amines.

3. \(NaNO_2\) in aqueous \(H_2SO_4\): This reagent is used in the diazotization test for aromatic amines, not in the Hinsberg test.

4. \(CH_3I\) (excess) followed by \(AgOH\): This is used in the **Finkelstein reaction** and other reactions for alkyl halides and amines, not in the Hinsberg test.

Conclusion:

The Hinsberg test involves treating amines with benzenesulfonyl chloride \((C_6H_5SO_2Cl)\) in the presence of aqueous sodium hydroxide \((NaOH)\) to form sulfonamide derivatives. The solubility of these derivatives helps distinguish between primary, secondary, and tertiary amines. Therefore, the correct reagent used in the Hinsberg test is **Option 2: \(C_6H_5SO_2Cl\) in aqueous \(NaOH\)**.