`C_6H_6overset(CH_3COCl)underset(AlCl_3)rarroverset(Zn//Hg//HCl)rarr(P)`
In the reaction sequence product (P) will be

Options

A. `C_6H_5-CH_3`
B. `C_6H_5-CH_2-CH_3`
C. `C_6H_5-CH_2-CHO`
D. `C_6H_5-CH=CH_2`

Answer

To solve the given problem step by step, we will analyze the reaction sequence involving benzene (C₆H₆), acetyl chloride (CH₃COCl), aluminum chloride (AlCl₃), and zinc amalgam in the presence of hydrochloric acid (HCl).

### Step 1: Electrophilic Aromatic Substitution
The first step involves the reaction of benzene (C₆H₆) with acetyl chloride (CH₃COCl) in the presence of aluminum chloride (AlCl₃).

1. **Formation of Electrophile**:
- Acetyl chloride reacts with AlCl₃ to form the electrophile, which is the acetyl cation (CH₃CO⁺).
- The reaction can be represented as:
\[ \text{CH}_3\text{COCl} + \text{AlCl}_3 \rightarrow \text{CH}_3\text{CO}^+ + \text{AlCl}_4^- \]

2. **Electrophilic Attack**:
- The benzene ring acts as a nucleophile and attacks the electrophile (CH₃CO⁺).
- This results in the formation of a sigma complex (arenium ion), which temporarily loses its aromaticity:
\[ \text{C}_6\text{H}_6 + \text{CH}_3\text{CO}^+ \rightarrow \text{C}_6\text{H}_5\text{COCH}_3^+ \]

3. **Deprotonation**:
- To regain aromaticity, the sigma complex loses a proton (H⁺), leading to the formation of acetophenone (C₆H₅COCH₃):
\[ \text{C}_6\text{H}_5\text{COCH}_3^+ \rightarrow \text{C}_6\text{H}_5\text{COCH}_3 + \text{H}^+ \]

### Step 2: Reduction of Carbonyl Group
The next step involves the reduction of the carbonyl group in acetophenone using zinc amalgam (Zn/Hg) in the presence of hydrochloric acid (HCl).

1. **Reduction Reaction**:
- Zinc amalgam acts as a reducing agent, converting the carbonyl group (C=O) of acetophenone into a methylene group (–CH₂–):
\[ \text{C}_6\text{H}_5\text{COCH}_3 \xrightarrow{\text{Zn/Hg, HCl}} \text{C}_6\text{H}_5\text{CH}_2\text{CH}_3 \]

### Final Product
The final product (P) after the reduction is:
\[ \text{C}_6\text{H}_5\text{CH}_2\text{CH}_3 \]
This compound is known as ethylbenzene.

### Conclusion
The product (P) formed from the given reaction sequence is ethylbenzene (C₆H₅CH₂CH₃).

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