The Hell-Volhard-Zelinsky reaction is used to

Options

A. determine the percentage of halogen in a compound
B. distinguish primary alcohols from secondary alcohols
C. synthesize `alpha`-bromoacids
D. synthesize `alpha`-hydroxy acids

Answer

**Step-by-Step Solution:**

1. **Understanding the Reaction**: The Hell-Volhard-Zelinsky (HVZ) reaction is a chemical reaction that is primarily used to prepare alpha-bromo acids from carboxylic acids.

2. **Starting Materials**: The reaction begins with a carboxylic acid, which contains a carbonyl group (C=O) and a hydroxyl group (–OH). For example, acetic acid (CH₃COOH) can be used.

3. **Reagents**: The key reagents in the HVZ reaction are red phosphorus (P) and bromine (Br₂) or chlorine (Cl₂). The red phosphorus acts as a reducing agent, facilitating the reaction between the carboxylic acid and halogen.

4. **Reaction Mechanism**:
- The carboxylic acid reacts with red phosphorus and bromine (or chlorine) to form an intermediate.
- The halogen (bromine or chlorine) replaces one of the alpha hydrogens (the hydrogen atom attached to the carbon adjacent to the carboxylic acid) in the carboxylic acid.
- This results in the formation of an alpha-bromo acid (or alpha-chloro acid if chlorine is used).

5. **Product Formation**: The final product of the reaction is an alpha-bromo acid, which has the structure R-CHBr-COOH, where R is the rest of the carbon chain from the original carboxylic acid.

6. **Conclusion**: Therefore, the Hell-Volhard-Zelinsky reaction is used to prepare alpha-bromo acids from carboxylic acids through the substitution of an alpha hydrogen with a bromine atom.

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