In the Rosenmund's reduction , `BaSO_(4)` taken with catalyst Pd acts as `:`

Options

A. Promotor
B. Catalytic poison
C. Cooperator
D. Absorber

Answer

**Step-by-Step Solution:**

1. **Understanding Rosenmund's Reduction:**
- Rosenmund's reduction is a chemical reaction that involves the reduction of acid chlorides to aldehydes using hydrogen gas (H2) in the presence of a palladium (Pd) catalyst.

2. **Identifying the Role of BaSO4:**
- In this reaction, barium sulfate (BaSO4) is added along with the palladium catalyst. The question asks about the role of BaSO4 in this context.

3. **Defining Terms:**
- To determine the role of BaSO4, we need to understand the definitions of the terms provided:
- **Promoter:** Increases the rate of the reaction.
- **Catalytic Portion:** Controls the reaction rate.
- **Cooperator:** Works in conjunction with the catalyst.
- **Absorber:** Acts as a surface for the reaction.

4. **Analyzing the Function of BaSO4:**
- BaSO4 acts as a **catalytic poison** in this reaction. It reduces the activity of the palladium catalyst due to its low surface area, which prevents the complete reduction of the acid chloride to the corresponding acid.

5. **Outcome of the Reaction:**
- As a result of BaSO4's presence, the reaction stops at the aldehyde stage, specifically producing benzaldehyde (C6H5CHO) rather than proceeding to the carboxylic acid.

6. **Conclusion:**
- Therefore, BaSO4 is acting as a catalytic poison that controls the reaction and prevents over-reduction of the reactant.

**Final Answer:**
In the Rosenmund's reduction, BaSO4 taken with the catalyst Pd acts as a **catalytic poison**.

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