Which of the following forms a stable diazonium salt at 273 278 K?

Options

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

Answer

To determine which compound forms a stable diazonium salt at 273-278 K, we need to understand the characteristics of diazonium salts and the conditions under which they are stable.

### Step-by-Step Solution:

1. **Understanding Diazonium Salts**:
- Diazonium salts are formed when aromatic amines react with nitrous acid (HNO2) at low temperatures (0-4 °C). These salts are generally stable when the amine is aromatic due to resonance stabilization.

2. **Identifying Aromatic Amines**:
- Aromatic amines, such as aniline (C6H5NH2), are capable of forming stable diazonium salts because the positive charge on the nitrogen can be delocalized into the aromatic ring.

3. **Conditions for Stability**:
- The stability of diazonium salts is favored at low temperatures, typically around 273-278 K. This is because higher temperatures can lead to decomposition of the diazonium salt.

4. **Analyzing the Options**:
- We need to evaluate the given options to identify which one is an aromatic amine.
- If aniline is one of the options, we can conclude that it will form a stable diazonium salt under the specified conditions.

5. **Conclusion**:
- Based on the information provided, aniline is the compound that forms a stable diazonium salt at 273-278 K. Therefore, the correct answer is option 2: aniline.

### Final Answer:
The compound that forms a stable diazonium salt at 273-278 K is **aniline** (option 2).