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 where acyl chlorides (RCOCl) are reduced to aldehydes (RCHO) using hydrogen gas in the presence of a palladium (Pd) catalyst.

2. **Role of Barium Sulfate (BaSO₄)**:
- In this reaction, barium sulfate is used alongside the palladium catalyst. It plays a significant role in modifying the activity of the palladium catalyst.

3. **Catalytic Poisoning**:
- Barium sulfate acts as a catalyst poison. It covers the active sites (pores) of the palladium catalyst. When the pores are covered, the reactants cannot access the active sites effectively, which slows down the reaction rate.

4. **Conclusion**:
- Therefore, in the context of the question, barium sulfate taken with the palladium catalyst acts as a **catalytic poison**.

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

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