X and Y in the below reaction are _ and______ respectively :
` C_6 H_5 -CO_2 H + X overset("Heat") to C_6H_5 -COCI overset(H_2 .Pd//BaSO_4) to Y `

Options

A. `SOCI_2 and C_6H_5 CHO`
B. `(COCI)_2 and C_6 H_5 CH_3`
C. `SOCI_2 and C_6H_5 CH_3`
D. `SOCI_2 and C_6 H_5 CH_2 CI`.

Explanation

To determine the compounds X and Y in the given reaction, we will analyze the steps involved in the transformation of benzoic acid to benzoyl chloride and then to benzaldehyde.

### Step-by-Step Solution:

1. **Identify the Reactants and Products:**
- The starting compound is benzoic acid (C₆H₅-CO₂H).
- The first product formed is benzoyl chloride (C₆H₅-COCl).
- The second product formed after the reaction with H₂ and Pd/BaSO₄ is benzaldehyde (C₆H₅-CHO).

2. **Determine the Reaction for X:**
- The transformation from benzoic acid to benzoyl chloride involves the replacement of the hydroxyl group (-OH) with a chlorine atom (-Cl).
- This type of reaction is typically carried out using a chlorinating agent. Common reagents for this transformation include thionyl chloride (SOCl₂), phosphorus trichloride (PCl₃), and phosphorus pentachloride (PCl₅).
- Among these, thionyl chloride (SOCl₂) is the most commonly used reagent for converting carboxylic acids to acyl chlorides.

3. **Identify X:**
- Therefore, we conclude that X is thionyl chloride (SOCl₂).

4. **Determine the Reaction for Y:**
- The reaction of benzoyl chloride with hydrogen (H₂) in the presence of a palladium catalyst on barium sulfate (Pd/BaSO₄) is known as the Rosenmund reduction.
- This reaction selectively reduces acyl chlorides to aldehydes without further reducing them to alkanes due to the use of the Lindlar catalyst (Pd/BaSO₄).
- The product of this reaction is benzaldehyde (C₆H₅-CHO).

5. **Identify Y:**
- Therefore, Y is benzaldehyde (C₆H₅-CHO).

### Final Answers:
- X is thionyl chloride (SOCl₂).
- Y is benzaldehyde (C₆H₅-CHO).