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, we will analyze the reactions involved when benzene is treated with methyl chloride in the presence of anhydrous AlCl3, followed by treatment with chlorine in UV light.

### Step 1: Reaction of Benzene with Methyl Chloride
- **Reaction**: Benzene (C6H6) is treated with methyl chloride (CH3Cl) in the presence of anhydrous aluminum chloride (AlCl3).
- **Mechanism**:
- AlCl3 acts as a Lewis acid and accepts a chloride ion from methyl chloride, generating a methyl carbocation (CH3+).
- The methyl carbocation is an electrophile, which will react with the nucleophilic benzene ring.

### Step 2: Electrophilic Aromatic Substitution
- **Reaction**: The benzene ring attacks the methyl carbocation.
- **Product**: This results in the formation of toluene (C6H5CH3) through an electrophilic aromatic substitution mechanism.
- **Regaining Aromaticity**: The proton (H+) that was attached to the benzene is released, restoring the aromatic nature of the ring.

### Step 3: Chlorination of Toluene
- **Reaction**: Toluene (C6H5CH3) is then treated with excess chlorine (Cl2) in the presence of UV light.
- **Mechanism**:
- The UV light initiates a radical mechanism, leading to the homolytic cleavage of Cl2 to form two chlorine radicals (Cl•).
- The chlorine radical can abstract a hydrogen atom from toluene, forming a benzyl radical (C6H5CH2•) and HCl.

### Step 4: Further Chlorination
- **Reaction**: The benzyl radical can react with another chlorine radical.
- **Product**: This leads to the substitution of all hydrogen atoms on the benzyl group with chlorine atoms, resulting in the final product, which is trichloromethylbenzene (C6H2Cl3).

### Final Product
- The final product after these reactions is **C6H2Cl3**, which is known as **trichlorotoluene** or **benzyl chloride**.

### Summary of Steps
1. Benzene reacts with methyl chloride in the presence of AlCl3 to form toluene.
2. Toluene undergoes chlorination in the presence of UV light, replacing hydrogen atoms with chlorine.
3. The final product is trichlorotoluene (C6H2Cl3).