MHT CET Chemistry Question (2026) — Solution

Step-by-step solution

The given reaction is the conversion of benzoyl chloride ( C _6 H _5 COCl ) to benzaldehyde ( C _6 H _5 CHO ). This transformation is known as the Rosenmund reduction. The reagent used for this reaction is hydrogen gas in the presence of a palladium catalyst supported on barium sulfate ( H _2, Pd - BaSO _4). The barium sulfate acts as a catalytic poison that partially deactivates the palladium, preventing the further reduction of the newly formed aldehyde into an alcohol. Thus, the reagent 'R' is H _2, Pd - BaSO _4. Answer: H _2, Pd - BaSO _4