The reaction of `HNO_(2)` with 'A' gives quaternary ammonium salt. A is

Options

A. Methyl amine
B. Dimethyl amine
C. Trimethyl amine
D. Aniline

Explanation

To determine the compound 'A' that reacts with nitrous acid (HNO₂) to form a quaternary ammonium salt, we can analyze the reactions of various amines with HNO₂.

### Step-by-Step Solution:

1. **Understanding the Reaction**:
- Nitrous acid (HNO₂) reacts with amines to form nitrosamines or quaternary ammonium salts depending on the degree of amine (primary, secondary, or tertiary).
- Quaternary ammonium salts are formed from tertiary amines when they react with nitrous acid.

2. **Identifying the Type of Amine**:
- A primary amine (RNH₂) reacts with HNO₂ to form a nitrous acid derivative (R-N₂⁺), which can lead to the formation of a gas (N₂) and an alcohol.
- A secondary amine (R₂NH) can also react to form a nitrosamine.
- A tertiary amine (R₃N) will react with HNO₂ to form a quaternary ammonium salt (R₃N⁺).

3. **Choosing the Right Amine**:
- Since we are looking for a compound 'A' that gives a quaternary ammonium salt upon reaction with HNO₂, we need to consider tertiary amines.
- For example, trimethylamine (N(CH₃)₃) is a tertiary amine.

4. **Reaction of Trimethylamine with HNO₂**:
- When trimethylamine reacts with HNO₂, it forms a quaternary ammonium salt:
\[ N(CH_3)_3 + HNO_2 \rightarrow N^+(CH_3)_3 + H_2O + N_2 \]
- The product is a quaternary ammonium salt (N⁺(CH₃)₃).

5. **Conclusion**:
- Therefore, the compound 'A' that reacts with HNO₂ to give a quaternary ammonium salt is trimethylamine (N(CH₃)₃).

### Final Answer:
The compound 'A' is trimethylamine (N(CH₃)₃).