Question

Conversion of benzene diazonium chloride to chlorobenzene in presence of CuCl / HCl is known as

• A. Sandmeyer reaction
• B. Mendius reaction
• C. Gattermann reaction
• D. Hofmann degradation

Hint:

To avoid getting confused between the Sandmeyer and Gattermann reactions, remember that Sandmeyer uses copper Salts ($\text{Cu}_2\text{Cl}_2$ or CuCl), while Gattermann relies purely on metallic copper powder (Cu).

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The problem presents a specific name reaction where an aromatic diazonium salt is converted into an aryl chloride using a copper-based catalyst, and asks us to identify the correct named organic reaction.

Step 2: Key Formula or Approach:
Substitution of the diazonium group ($-\text{N}_2^+\text{Cl}^-$) on a benzene ring by a halogen atom using copper(I) salts is a classic radical-nucleophilic substitution reaction.

Step 3: Detailed Explanation:
When freshly prepared benzene diazonium chloride solution is treated with cuprous chloride (CuCl) dissolved in hydrochloric acid (HCl), the diazonium group is successfully replaced by a chlorine atom, evolving nitrogen gas: $$\text{C}_6\text{H}_5\text{N}_2^+\text{Cl}^- \xrightarrow{\text{CuCl/HCl}} \text{C}_6\text{H}_5\text{Cl} + \text{N}_2\uparrow$$ This specific method using copper(I) salts is historically and chemically designated as the

Sandmeyer reaction. Note: If copper powder (Cu) is used instead of cuprous salt (CuCl), the reaction is termed the

Gattermann reaction.

Step 4: Final Answer:
The process described is the Sandmeyer reaction, matching option (A).