Which of the following compounds does not liberate `N_2` on
treatment with `HNO_2`?

Options

A. `H_(3) C - overset(overset(O)(||))C - NH_2`
B. `H_(2) N - overset(overset(O)(||))C - NH_2`
C.
D. `H_(3) C - underset(underset(H)(|))N - CH_3`

Answer

To determine which compound does not liberate nitrogen gas (N₂) upon treatment with nitrous acid (HNO₂), we need to understand the behavior of different types of amines when they react with HNO₂.

### Step-by-Step Solution:

1. **Identify the Types of Amines**:
- Amines can be classified into three categories: primary (1°), secondary (2°), and tertiary (3°).
- Primary amines have the structure RNH₂, secondary amines have R₂NH, and tertiary amines have R₃N.

2. **Reactions with HNO₂**:
- **Primary Amines (1°)**: When treated with HNO₂, primary amines (RNH₂) react to form alcohol (ROH), nitrogen gas (N₂), and water (H₂O). This is a characteristic reaction of primary amines.
- **Secondary Amines (2°)**: Secondary amines (R₂NH) react with HNO₂ to form N-nitrosoamines, and do not liberate nitrogen gas.
- **Tertiary Amines (3°)**: Tertiary amines (R₃N) react with HNO₂ to form nitrite salts, and also do not liberate nitrogen gas.

3. **Determine the Compound in Question**:
- Based on the information above, we need to identify which of the given compounds is a secondary amine or a tertiary amine, as these will not liberate nitrogen gas when treated with HNO₂.

4. **Analyze the Options**:
- If the options provided include a secondary amine, that will be the correct answer since it does not liberate N₂ upon treatment with HNO₂.

5. **Conclusion**:
- The compound that does not liberate nitrogen gas when treated with HNO₂ is the secondary amine.

### Final Answer:
The compound that does not liberate N₂ on treatment with HNO₂ is the **secondary amine**.