Identify the name of the given reaction:
` R - CH_2- COOH underset( (ii) H_2) overset( (i) X_2//" Red P" ) to R - underset ( X = Cl, Br) underset( " a- Halo Carboxylic acid ") underset(|) (CH) - COOH`

Options

A. Etard reaction
B. Hell - Volhard - Zelinsky reaciton
C. Stephen reaction
D. None of the above

Explanation

To identify the name of the given reaction, we need to analyze the reaction step by step.

### Step 1: Understand the Reactants
The starting compound is R-CH₂-COOH, which is a carboxylic acid. The "R" represents a hydrocarbon chain or group, and "COOH" is the carboxylic acid functional group. The carbon atom adjacent to the carboxylic acid (the one attached to the "R" group) is known as the alpha carbon.

**Hint:** Identify the functional groups and their positions in the molecule.

### Step 2: Identify the Reaction Conditions
The reaction involves the use of halogens (X₂, where X can be Cl or Br) in the presence of red phosphorus. This combination is crucial for the halogenation process that occurs at the alpha position of the carboxylic acid.

**Hint:** Pay attention to the reagents and their roles in the reaction.

### Step 3: Recognize the Reaction Type
The reaction involves the halogenation of the alpha hydrogen of the carboxylic acid. When X₂ reacts with the alpha hydrogen, it replaces one of the hydrogen atoms with a halogen atom (Cl or Br). This process is specifically known as halogenation at the alpha position.

**Hint:** Think about what happens to the alpha hydrogen during the reaction.

### Step 4: Determine the Product
After the halogenation, the product formed is R-CHX-COOH, where X is the halogen (Cl or Br). This compound is referred to as an alpha-halo carboxylic acid.

**Hint:** Consider the structure of the product and how it relates to the starting material.

### Step 5: Name the Reaction
The overall reaction is known as the **Hunsdiecker-Von Ziegler (HVZ) reaction**. This reaction specifically describes the halogenation of the alpha carbon of carboxylic acids.

**Hint:** Recall the name associated with the halogenation of alpha-hydrogen in carboxylic acids.

### Final Answer
The name of the given reaction is the **HVZ reaction**.

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