Diazotisation can be carried out by the action of `NaNO_(2)` and dilute HCl at ice cold temperature on

Options

A. Aromatic secondary amine
B. Aromatic primary amine
C. Aromatic nitro compound
D. Aliphatic amine

Answer

To solve the question regarding which compound can undergo diazotization when treated with sodium nitrite (NaNO₂) and dilute hydrochloric acid (HCl) at ice-cold temperatures, we can follow these steps:

### Step 1: Understand Diazotization
Diazotization is a chemical reaction where a primary amine reacts with nitrous acid (which can be generated in situ from NaNO₂ and HCl) to form a diazonium salt. This reaction typically occurs at low temperatures to stabilize the diazonium salt.

### Step 2: Identify the Types of Amines
We need to analyze the options given:
1. Aromatic secondary amine
2. Aromatic primary amine
3. Aromatic nitro compound
4. Aliphatic amine

### Step 3: Analyze Each Option
- **Aromatic Secondary Amine**: Secondary amines do not form diazonium salts; they do not have the required structure (R-NH-R') to undergo diazotization.

- **Aromatic Primary Amine**: Primary amines (R-NH₂) can undergo diazotization. When treated with NaNO₂ and HCl, they form stable diazonium salts (Ar-N₂⁺).

- **Aromatic Nitro Compound**: Nitro compounds do not undergo diazotization. They are not amines and cannot form diazonium salts.

- **Aliphatic Amine**: Aliphatic amines can form diazonium salts, but they are generally unstable and decompose quickly, especially at higher temperatures.

### Step 4: Conclusion
The only suitable compound that can undergo diazotization under the given conditions (NaNO₂ and dilute HCl at ice-cold temperature) is the **aromatic primary amine**. This is because it can form a stable diazonium salt.

### Final Answer
**Aromatic primary amine** is the correct answer.

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