A `overset(Pci_(5))(rarr) B overset("Pd/BaSO"_(4))(rarr) c underset(0^(@)C)overset("Conc."H_(2)SO_(4))(rarr)` D in the above reaction A, B, C & D are :

Options

A. `CH_(3)`COOH, `CH_(3)`COCl, `CH_(3)`CHO, Metaldehyde
B. `CH_(3)`COOH, `CH_(3)`COCl, `CH_(3)`CHO, Paraldehyde
C. `CH_(3)`COOH, `CH_(3)`COCl, `CH_(3) - CH_(2)`OH, Paraldehyde
D. None of these

Answer

To solve the question, we need to identify the compounds A, B, C, and D in the given reaction sequence:

1. **Identify Compound A**:
- The first step involves the reaction of acetic acid (CH3COOH) with PCl5.
- PCl5 is a reagent that converts carboxylic acids into acyl chlorides.
- Therefore, when acetic acid reacts with PCl5, it forms acetyl chloride (CH3COCl).
- **So, A = CH3COOH (Acetic Acid)**

2. **Identify Compound B**:
- The next step involves the reaction of acetyl chloride (A) with Pd/BaSO4.
- This is a Rosenmund reduction, which reduces acyl chlorides to aldehydes.
- The product of this reaction is acetaldehyde (CH3CHO).
- **So, B = CH3COCl (Acetyl Chloride)**

3. **Identify Compound C**:
- The subsequent step involves the reaction of acetaldehyde (B) with concentrated H2SO4 at 0°C.
- This reaction leads to the formation of paraldehyde, which is a cyclic trimer of acetaldehyde.
- **So, C = CH3CHO (Acetaldehyde)**

4. **Identify Compound D**:
- Finally, the product formed from the reaction of acetaldehyde under the specified conditions is paraldehyde.
- Paraldehyde can be represented as (C2H4O)3 or as a cyclic structure of three acetaldehyde units.
- **So, D = Paraldehyde**

### Summary of Compounds:
- **A = CH3COOH (Acetic Acid)**
- **B = CH3COCl (Acetyl Chloride)**
- **C = CH3CHO (Acetaldehyde)**
- **D = Paraldehyde**