The given reaction `CH_3COOH+Cl_2overset(P)rarrClCH_2COOH+HCl` is known as

Options

A. Hell - Volhard - Zelinsky reaction
B. Birch reaction
C. Rosenmund reaction
D. Hunsdiecker reaction

Answer

To solve the question regarding the reaction `CH_3COOH + Cl_2 → ClCH_2COOH + HCl`, we need to identify the name of the reaction taking place.

### Step-by-Step Solution:

1. **Identify the Reactants and Products**:
- The reactants are ethanoic acid (CH₃COOH) and chlorine (Cl₂).
- The products are alpha-chloroethanoic acid (ClCH₂COOH) and hydrochloric acid (HCl).

2. **Understand the Reaction Type**:
- The reaction involves the substitution of a hydrogen atom in the alpha position of the carboxylic acid (ethanoic acid) with a chlorine atom.
- This is characteristic of a halogenation reaction of carboxylic acids.

3. **Recall the Specific Reaction Name**:
- The reaction is known as the **Hell-Volhard-Zelinsky reaction**. This reaction involves the halogenation of carboxylic acids at the alpha position in the presence of a halogen (like Cl₂) and phosphorus (P).

4. **Eliminate Other Options**:
- Other reactions mentioned (like bridge reduction, Rosenmann reaction, and Hans Dekker reaction) do not apply to this scenario as they involve different reactants and mechanisms.

5. **Conclude the Answer**:
- Therefore, the name of the reaction `CH_3COOH + Cl_2 → ClCH_2COOH + HCl` is the **Hell-Volhard-Zelinsky reaction**.

### Final Answer:
The given reaction is known as the **Hell-Volhard-Zelinsky reaction**.