How is benzoic acid converted to
Benzaldehyde

Explanation

To convert benzoic acid to benzaldehyde, we can follow these steps:

### Step 1: Convert Benzoic Acid to Benzoyl Chloride
- **Reaction**: Treat benzoic acid (C6H5COOH) with thionyl chloride (SOCl2).
- **Process**: The hydroxyl group (-OH) of the carboxylic acid is replaced by a chlorine atom, forming benzoyl chloride (C6H5COCl). During this reaction, sulfur dioxide (SO2) and hydrochloric acid (HCl) are released as by-products.

### Step 2: Reduction of Benzoyl Chloride to Benzaldehyde
- **Reaction**: Reduce benzoyl chloride (C6H5COCl) using hydrogen gas (H2) in the presence of a palladium catalyst on barium sulfate (Pd/BaSO4), which is known as the Rosenmund reduction.
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