MHTCET 18 Apr 2026 Shift 1 Paper

Concept:Rosenmund reduction converts acid chlorides to aldehydes using hydrogen and a poisoned palladium catalyst.Explanation:Benzoyl chloride ($\mathrm{C}_6\mathrm{H}_5\mathrm{COCl}$) is reduced to benzaldehyde ($\mathrm{C}_6\mathrm{H}_5\mathrm{CHO}$) by the Rosenmund reduction method.In this reaction, hydrogen gas acts as the reducing agent.The catalyst used is palladium supported on barium sulfate, $\mathrm{Pd}-\mathrm{BaSO}_4$, which is partially deactivated or poisoned.This poisoning prevents the over-reduction of benzaldehyde to benzyl alcohol.The balanced chemical reaction is:$$\mathrm{C}_6\mathrm{H}_5\mathrm{COCl} + \mathrm{H}_2 \xrightarrow{\mathrm{Pd}-\mathrm{BaSO}_4} \mathrm{C}_6\mathrm{H}_5\mathrm{CHO} + \mathrm{HCl}$$This is a standard method for the partial reduction of acid chlorides to aldehydes.Since the acyl chloride is converted to benzaldehyde with the elimination of $\mathrm{HCl}$, the reagent 'R' must supply hydrogen with the poisoned catalyst.Therefore, the reagent 'R' is $\mathrm{H}_2$ along with $\mathrm{Pd}-\mathrm{BaSO}_4$.Answer:Option B: $\mathrm{H}_2, \mathrm{Pd}-\mathrm{BaSO}_4$