Question

Which of the following reagents is used in Rosenmund reduction?

• A. Zn/HCl
• B. H$_2$/Pd - BaSO$_4$ (poisoned)
• C. LiAlH$_4$
• D. NaBH$_4$

Hint:

Rosenmund reduction uses Zn/HCl to reduce acyl chlorides to aldehydes, making it different from other reductions.

Answer 1

The Correct Option is B

The Rosenmund reduction is a chemical reaction used to reduce acyl chlorides to aldehydes. The typical reagent for this reduction is hydrogen gas (H₂) in the presence of a catalyst, specifically palladium (Pd) that is poisoned with barium sulfate (BaSO₄). This specific catalyst combination ensures that the reduction stops at the aldehyde stage and does not proceed further to an alcohol.

Let's evaluate the options provided:

• H₂/Pd - BaSO₄ (poisoned): This is indeed the reagent used in the Rosenmund reduction, as it effectively stops at the aldehyde stage.
• Zn/HCl: This combination is typically used for other types of reductions, such as the reduction of nitro compounds, and is not used in Rosenmund reduction.
• LiAlH₄: This is a strong reducing agent used to reduce a wide range of compounds, including esters and amides, to alcohols but not suitable for selective reduction to aldehydes.
• NaBH₄: Another reducing agent, commonly used for reducing aldehydes and ketones to alcohols, not used for Rosenmund reduction.

Conclusion: The correct reagent for the Rosenmund reduction is H₂/Pd - BaSO₄ (poisoned).