How will you bring about the following conversions ?
(i) Benzoic acid to Benzaldehyde
(ii) Benzene to m-Nitroacetophenone
(iii) Ethanol to 3-Hydroxybutanal.

Explanation

To convert the given compounds as per the question, we will follow the steps outlined below:

### (i) Conversion of Benzoic Acid to Benzaldehyde

1. **Starting Material**: Begin with benzoic acid (C6H5COOH).
2. **Conversion to Acyl Chloride**: Treat benzoic acid with thionyl chloride (SOCl2). This will convert the carboxylic acid group (-COOH) into an acyl chloride (-COCl), releasing sulfur dioxide (SO2) and hydrochloric acid (HCl) as by-products.
- Reaction: C6H5COOH + SOCl2 → C6H5COCl + SO2 + HCl
3. **Reduction to Aldehyde**: Next, reduce the acyl chloride to an aldehyde using hydrogen in the presence of palladium on barium sulfate (Pd/BaSO4) as a catalyst.
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