The following reaction is known as
`C_(6)H_(6)+CH_(3)Cl underset(("anhy."))overset(AlCl_(3))to C_(6)H_(5)CH_(3)+HCl`

Options

A. Wurtz-Fittig reaction
B. Friedel-Crafts reaction
C. Rosenmund reaction
D. Sandmeyer reaction

Explanation

To solve the question regarding the reaction of benzene with methyl chloride in the presence of anhydrous aluminum chloride, we will break down the process step by step.

### Step-by-Step Solution:

1. **Identify the Reactants and Products:**
- The reactants are benzene (C₆H₆) and methyl chloride (CH₃Cl).
- The product of the reaction is toluene (C₆H₅CH₃) and hydrochloric acid (HCl).

2. **Recognize the Reaction Type:**
- This reaction is an example of an electrophilic aromatic substitution. In this process, an electrophile replaces one of the hydrogen atoms on the benzene ring.

3. **Formation of the Electrophile:**
- In the presence of anhydrous aluminum chloride (AlCl₃), methyl chloride (CH₃Cl) reacts to form a methyl cation (CH₃⁺) and a complex ion (AlCl₄⁻).
- The reaction can be represented as:
\[ CH₃Cl + AlCl₃ \rightarrow CH₃^+ + AlCl₄^- \]

4. **Electrophilic Attack on Benzene:**
- The methyl cation (CH₃⁺) acts as an electrophile and attacks the benzene ring.
- This leads to the formation of a sigma complex (also known as an arenium ion), where a hydrogen atom is temporarily removed from the benzene ring.
- The reaction can be illustrated as:
\[ C₆H₆ + CH₃^+ \rightarrow C₆H₅CH₃^+ \text{ (sigma complex)} \]

5. **Rearrangement and Restoration of Aromaticity:**
- The sigma complex is not aromatic and is less stable. To regain aromaticity, it loses a proton (H⁺).
- This step restores the aromatic character of the benzene ring and forms toluene (C₆H₅CH₃).
- The reaction can be summarized as:
\[ C₆H₅CH₃^+ \rightarrow C₆H₅CH₃ + H^+ \]

6. **Formation of HCl:**
- The proton (H⁺) that is released combines with AlCl₄⁻ to regenerate AlCl₃ and produce hydrochloric acid (HCl):
\[ H^+ + AlCl₄^- \rightarrow AlCl₃ + HCl \]

7. **Final Reaction Summary:**
- The overall reaction can be summarized as:
\[ C₆H₆ + CH₃Cl \xrightarrow{AlCl₃} C₆H₅CH₃ + HCl \]

8. **Naming the Reaction:**
- This reaction is known as the **Friedel-Crafts Alkylation**.

### Conclusion:
The reaction of benzene with methyl chloride in the presence of anhydrous aluminum chloride is called **Friedel-Crafts Alkylation**.