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

Options

A. Wurtz - Fittig.s reaction
B. Friedal - Craft.s reaction
C. Rosenmund reaction
D. Sandmeyer reaction

Explanation

The reaction given is:

\[ C_6H_6 + CH_3Cl \overset{AlCl_3}{\longrightarrow} C_6H_5CH_3 + HCl \]

To identify the name of this reaction, we can analyze the components and the process involved.

### Step-by-Step Solution:

1. **Identify the Reactants**:
- The reactants are benzene (\(C_6H_6\)) and methyl chloride (\(CH_3Cl\)).

**Hint**: Look for the type of hydrocarbons involved in the reaction.

2. **Identify the Catalyst**:
- The catalyst used in this reaction is aluminum chloride (\(AlCl_3\)). This compound acts as a Lewis acid, which means it can accept electron pairs.

**Hint**: Consider the role of \(AlCl_3\) in facilitating the reaction.

3. **Reaction Mechanism**:
- In the presence of \(AlCl_3\), \(CH_3Cl\) forms a methyl cation (\(CH_3^+\)) after the chloride ion (\(Cl^-\)) is removed. The \(AlCl_3\) combines with the chloride ion to form \(AlCl_4^-\).
- The benzene ring, which is electron-rich, acts as a nucleophile and attacks the methyl cation, leading to the formation of toluene (\(C_6H_5CH_3\)).

**Hint**: Think about how nucleophiles and electrophiles interact in organic reactions.

4. **Formation of Products**:
- The product formed is toluene (\(C_6H_5CH_3\)), and hydrochloric acid (\(HCl\)) is released as a byproduct.

**Hint**: Identify the products formed and check if they correspond to known compounds.

5. **Naming the Reaction**:
- This type of reaction, where an alkyl group is introduced into an aromatic ring, is known as the Friedel-Crafts alkylation reaction.

**Hint**: Recall the names of common reactions involving aromatic compounds and alkyl halides.

### Final Answer:
The reaction is known as the **Friedel-Crafts alkylation reaction**.