Benzene is treated with methyl chloride in presence of anhydrous `AlCl_3` and the product treated with excess of chlorine in presence of UV light. The final product is:

Options

A. `C_(6)H_(5)Cl`
B. `C_(6)H_(5)CH_(2)Cl`
C. `C_(6)H_(5)"CCl"_(3)`
D. `C_(6)H_(5)CHCl_(2)`

Answer

To solve the problem step by step, let's break down the reactions that occur when benzene is treated with methyl chloride in the presence of anhydrous aluminum trichloride, followed by treatment with excess chlorine in the presence of UV light.

### Step 1: Electrophilic Substitution Reaction
1. **Reactants**: Benzene (C₆H₆) and methyl chloride (CH₃Cl) in the presence of anhydrous aluminum trichloride (AlCl₃).
2. **Mechanism**: The aluminum trichloride acts as a Lewis acid and facilitates the formation of a methyl cation (CH₃⁺) from methyl chloride. This cation is a strong electrophile.
3. **Product Formation**: The benzene ring, which is rich in electrons, attacks the methyl cation, leading to the substitution of one hydrogen atom on the benzene ring with a methyl group.
4. **Final Product**: The product of this reaction is toluene (C₆H₅CH₃).

### Step 2: Free Radical Substitution Reaction
1. **Reactants**: Toluene (C₆H₅CH₃) is treated with excess chlorine (Cl₂) in the presence of UV light.
2. **Mechanism**: The UV light causes homolytic cleavage of the Cl-Cl bond, generating chlorine radicals (Cl•).
3. **Radical Formation**: The chlorine radicals can abstract hydrogen atoms from the methyl group of toluene, forming a benzyl radical (C₆H₅CH₂•) and HCl.
4. **Further Reactions**: The benzyl radical can react with another chlorine radical to form benzyl chloride (C₆H₅CH₂Cl).

### Step 3: Further Chlorination
1. **Benzyl Chloride Reaction**: Benzyl chloride (C₆H₅CH₂Cl) can further react with chlorine radicals in the presence of UV light.
2. **Formation of Dichloride**: The benzyl chloride can lose another hydrogen atom to form a dichlorinated product (C₆H₅CHCl₂) and HCl.
3. **Trichloride Formation**: This dichloride can again react with chlorine radicals to form a trichlorinated product (C₆H₅CCl₃) and HCl.

### Final Product
The final product after all these reactions is a trichlorinated derivative of toluene, specifically benzene with three chlorine atoms attached to the methyl carbon. The structure can be represented as C₆H₅CCl₃.

### Conclusion
The final product is **benzyl trichloride (C₆H₅CCl₃)**, which corresponds to option 3 in the given choices.

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