On heating aqueous solution of benzene diazonium chloride, which is formed

Options

A. Benzene
B. Chlorobenzene
C. Phenol
D. Aniline

Answer

To solve the question regarding the product formed when heating an aqueous solution of benzene diazonium chloride, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactant**: The reactant in this case is benzene diazonium chloride, which has the formula C6H5N2Cl. It is a diazonium salt that is typically used in organic synthesis.

**Hint**: Remember that diazonium salts are often unstable and can undergo various reactions when heated or treated with certain reagents.

2. **Heating the Solution**: When an aqueous solution of benzene diazonium chloride is heated, it undergoes a reaction. The presence of heat can cause the diazonium group (N2) to become unstable.

**Hint**: Consider what happens to unstable groups when they are subjected to heat. They often decompose or react to form new products.

3. **Role of Water**: In the presence of water (from the aqueous solution), the diazonium ion (C6H5N2^+) can react with hydroxide ions (OH^-) that are generated from the dissociation of water.

**Hint**: Think about how water can dissociate and what ions are available to react with the diazonium ion.

4. **Substitution Reaction**: The hydroxide ion (OH^-) can replace the diazonium group (N2) on the benzene ring. This is a nucleophilic substitution reaction where the nitrogen gas (N2) is released as a byproduct.

**Hint**: Recall that in nucleophilic substitution reactions, a nucleophile replaces a leaving group. Here, the leaving group is the diazonium ion.

5. **Formation of Phenol**: The product of this reaction is phenol (C6H5OH), as the hydroxyl group (OH) is now attached to the benzene ring.

**Hint**: Remember that phenol is characterized by having a hydroxyl group attached to a benzene ring.

6. **Conclusion**: Therefore, the product formed when heating an aqueous solution of benzene diazonium chloride is phenol.

**Final Answer**: The correct answer is option 3: phenol.

### Summary of Steps:
1. Identify the reactant (benzene diazonium chloride).
2. Heat the solution to initiate the reaction.
3. Recognize the role of water in generating hydroxide ions.
4. Understand the substitution reaction where hydroxide replaces the diazonium group.
5. Conclude that phenol is the final product.