How is carbolic acid prepared from benzene diazonium chloride ?

Options

A. Treating it with nitrous acid at 275K
B. Preparing an aqueous solution and warming it
C. Treating it with sodium hydroxide
D. Freezing it

Answer

To prepare carbolic acid (phenol) from benzene diazonium chloride, follow these steps:

### Step-by-Step Solution:

1. **Starting Material**: Begin with benzene diazonium chloride (C6H5N2Cl). This compound is typically formed by the diazotization of an aromatic amine (like aniline) with nitrous acid (HNO2).

2. **Dissolution**: Dissolve benzene diazonium chloride in water. This step is crucial as it allows the diazonium salt to interact with the solvent and other reagents.

3. **Acid Addition**: Add a small amount of dilute sulfuric acid (H2SO4) to the aqueous solution of benzene diazonium chloride. The dilute acid helps in the hydrolysis of the diazonium salt.

4. **Heating**: Warm the solution gently. The heat facilitates the reaction, leading to the breakdown of the diazonium salt.

5. **Reaction Outcome**: During the warming process, the benzene diazonium chloride undergoes hydrolysis to produce phenol (carbolic acid, C6H5OH), nitrogen gas (N2), and hydrochloric acid (HCl) as by-products.

6. **Final Product**: The main product of this reaction is carbolic acid (phenol), which can be separated and purified if necessary.

### Summary of Reaction:
The overall reaction can be summarized as:
\[ \text{C}_6\text{H}_5\text{N}_2\text{Cl} + \text{H}_2\text{O} + \text{H}_2\text{SO}_4 \rightarrow \text{C}_6\text{H}_5\text{OH} + \text{N}_2 + \text{HCl} + \text{H}_2\text{SO}_4 \]