How will you prepare benzoic acid by using Grignard reagent?

Answer

To prepare benzoic acid using a Grignard reagent, follow these steps:

### Step-by-Step Solution:

1. **Preparation of Grignard Reagent**:
- Start with bromobenzene (C6H5Br) and magnesium (Mg) in dry ether (anhydrous diethyl ether).
- The reaction will yield phenylmagnesium bromide (C6H5MgBr), which is the Grignard reagent.

**Reaction**:
\[ C_6H_5Br + Mg \xrightarrow{\text{dry ether}} C_6H_5MgBr \]

2. **Reaction with Carbon Dioxide**:
- The phenylmagnesium bromide (C6H5MgBr) is then reacted with dry ice (solid carbon dioxide, CO2).
- The Grignard reagent will attack the carbon of carbon dioxide, leading to the formation of a carboxylate intermediate.

**Reaction**:
\[ C_6H_5MgBr + CO_2 \rightarrow C_6H_5C(=O)OMgBr \]

3. **Acidification**:
- The carboxylate intermediate (C6H5C(=O)OMgBr) is then treated with a mineral acid (like hydrochloric acid, HCl) to protonate the carboxylate ion.
- This will yield benzoic acid (C6H5COOH) and magnesium bromide hydroxide as a byproduct.

**Reaction**:
\[ C_6H_5C(=O)OMgBr + HCl \rightarrow C_6H_5COOH + Mg(OH)Br \]

### Final Product:
- The final product of this reaction sequence is benzoic acid (C6H5COOH).

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