ROSENMUND REDUCTION is used to prepare an aldehyde from an acyl chloride. The reagents and key feature of the reaction are

1. NCERT §8.2.2 lists Rosenmund as a specific aldehyde-from-acyl-chloride method. 2. Reagents: $\mathrm{H_2}$ gas over $\mathrm{Pd/BaSO_4}$ that has been POISONED with sulphur or quinoline. 3. Why poisoning? An unpoisoned catalyst would continue reducing the aldehyde to a primary alcohol. The poison MODERATES the catalyst activity so the reduction STOPS cleanly at the aldehyde stage. 4. Mechanism summary: $\mathrm{R{-}COCl} + \mathrm{H_2} \xrightarrow{\text{Pd/BaSO}_4\,(\text{S})} \mathrm{R{-}CHO} + \mathrm{HCl}$. 5. Option A would over-reduce to alcohol. Option C with $\mathrm{LiAlH_4}$ also reduces to alcohol (unless you use the bulkier $\mathrm{LiAlH(O\,t\text{-}Bu)_3}$). Option D over-reduces because the catalyst is too active. _Source: NCERT Class 12 Chemistry Part 2, Ch 8, §8.2.2 (Preparation of Aldehydes — Rosenmund reduction), p. 5–6._