See image — Aldehydes Ketones and Carboxylic Acids Chemistry Question

💡 Solution & Explanation

Step 1: Identify the starting material. The starting material is benzoic acid (Ph-COOH), a carboxylic acid. Step 2: Reaction with SOCl2 (thionyl chloride). When a carboxylic acid reacts with SOCl2, the -OH of the carboxyl group is replaced by -Cl, converting the carboxylic acid into an acid chloride (acyl chloride). Product (A) is benzoyl chloride: Ph-C(=O)-Cl. Step 3: Reaction of acid chloride with H2 over Pd-BaSO4. This is the Rosenmund reduction. In this reaction, an acid chloride (acyl chloride) is selectively reduced by H2 in the presence of a poisoned palladium catalyst (Pd on BaSO4, which is a partially deactivated/poisoned catalyst). The poisoned catalyst ensures that reduction stops at the aldehyde stage and does not proceed further to the alcohol. Ph-C(=O)-Cl + H2 --Pd/BaSO4--> Ph-C(=O)-H + HCl. Product (B) is benzaldehyde (Ph-CHO). Step 4: Evaluate other options. (b) Ph-CH2-OH (benzyl alcohol) would require over-reduction beyond the aldehyde; the poisoned Pd-BaSO4 catalyst prevents this. (c) Ph-CH2-Cl (benzyl chloride) is not a product of hydrogenation of an acid chloride. (d) Ph-CH=CH2 (styrene) is unrelated to this reaction sequence. The Rosenmund reduction is specifically designed to stop at the aldehyde, making (a) Ph-CHO the correct product. Therefore, the correct answer is A.