Question

Identify A and B in the given chemical reaction sequence : -

• A.
• B.
• C.
• D.

Answer 1

Answer: (C)

Answer 2

The given sequence involves the following steps:
Step 1: Friedel-Crafts Acylation
Benzene ($\text{C}_6\text{H}_6$) reacts with acetyl chloride ($\text{CH}_3\text{COCl}$) in the presence of $\text{AlCl}_3$, an electrophilic catalyst. This forms acetophenone ($\text{C}_6\text{H}_5\text{COCH}_3$) as compound $A$:
$\text{C}_6\text{H}_6 + \text{CH}_3\text{COCl} \xrightarrow[\text{AlCl}_3]{} \text{C}_6\text{H}_5\text{COCH}_3 \, (A).$
Step 2: Clemmensen Reduction
Acetophenone ($\text{C}_6\text{H}_5\text{COCH}_3$) undergoes Clemmensen reduction using zinc amalgam ($\text{Zn–Hg}$) and hydrochloric acid ($\text{HCl}$). The carbonyl group ($-\text{CO}$) is reduced to a methylene group ($-\text{CH}_2-$), resulting in ethylbenzene ($\text{C}_6\text{H}_5\text{CH}_2\text{CH}_3$) as compound $B$:
$\text{C}_6\text{H}_5\text{COCH}_3 \xrightarrow[\text{Zn–Hg, HCl}]{} \text{C}_6\text{H}_5\text{CH}_2\text{CH}_3 \, (B).$
Step 3: Acidic Oxidation
Ethylbenzene reacts with $\text{H}^+$ under oxidation conditions to form acetophenone again. This completes the reaction cycle.
Final Products:
$A = \text{C}_6\text{H}_5\text{COCH}_3$ (Acetophenone).
$B = \text{C}_6\text{H}_5\text{CH}_2\text{CH}_3$ (Ethylbenzene).
Conclusion: The correct identification of $A$ and $B$ is given in option $(3)$.
Final Answer: (3).