Which of the following amines will form stable doazonium salt at `273-283K`?

Options

A. Ethylamine
B. Aniline
C. Dimethylamine
D. Benzylamine

Answer

To determine which of the following amines will form a stable diazonium salt at 273-283 K, we need to analyze the structure and stability of the diazonium salts formed from each amine. The amines given are ethylamine, aniline, dimethylamine, and benzylamine.

### Step-by-Step Solution:

1. **Understanding Diazonium Salts**: Diazonium salts are formed when primary amines react with nitrous acid (HNO2) at low temperatures. The general formula for a diazonium salt is R-N2^+X^-, where R is an alkyl or aryl group and X is a halide or another anion.

2. **Analyzing Each Amine**:
- **Ethylamine (C2H5NH2)**: This is a primary aliphatic amine. When ethylamine forms a diazonium salt, the positive charge on the nitrogen does not have resonance stabilization from a benzene ring. Therefore, the diazonium salt formed from ethylamine is not stable at low temperatures.

- **Aniline (C6H5NH2)**: Aniline is a primary aromatic amine. When aniline forms a diazonium salt, the positive charge on the nitrogen can be delocalized into the benzene ring through resonance. This delocalization stabilizes the diazonium salt, making it stable at low temperatures (273-283 K).

- **Dimethylamine (C2H7N)**: This is a secondary amine. Similar to ethylamine, dimethylamine does not have the resonance stabilization that aniline has. Therefore, the diazonium salt formed from dimethylamine is also not stable at low temperatures.

- **Benzylamine (C6H5CH2NH2)**: Benzylamine is a primary amine with a benzyl group. The diazonium salt formed from benzylamine does not have the same level of resonance stabilization as aniline because the positive charge cannot be delocalized into the benzene ring. Thus, it is less stable than aniline's diazonium salt.

3. **Conclusion**: Among the given amines, only **aniline** can form a stable diazonium salt at 273-283 K due to the resonance stabilization provided by the benzene ring.

### Final Answer:
**Aniline** will form a stable diazonium salt at 273-283 K.