Primary and secondary amines are distinguished by :

Options

A. `Br_2//KOH`
B. `HClO`
C. `NHO_2`
D. `NH_3`

Explanation

To distinguish between primary and secondary amines, we can use nitrous acid (HNO2). Here’s a step-by-step solution:

### Step 1: Understanding the Types of Amines
- **Primary amines (RNH2)** have one alkyl group attached to the nitrogen atom.
- **Secondary amines (R2NH)** have two alkyl groups attached to the nitrogen atom.

### Step 2: Reaction with Nitrous Acid (HNO2)
- When a primary amine reacts with nitrous acid, it produces an alcohol and nitrogen gas:
\[ RNH2 + HNO2 \rightarrow ROH + N_2 + H_2O \]
This indicates that primary amines can be converted to alcohols.

- When a secondary amine reacts with nitrous acid, it forms a N-nitrosoamine:
\[ R2NH + HNO2 \rightarrow R2N-N=O + H2O \]
This indicates that secondary amines form a different product, specifically a N-nitroso compound.

### Step 3: Conclusion
- Since the reactions of primary and secondary amines with nitrous acid yield different products, we can use this reaction to distinguish between them. Therefore, the correct answer is that primary and secondary amines are distinguished by **HNO2 (nitrous acid)**.

### Final Answer:
Primary and secondary amines are distinguished by nitrous acid (HNO2).

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