See image — Aromatic Hydrocarbons Chemistry Question

💡 Solution & Explanation

Step 1: Identify compound A. Three molecules of HC≡CH (acetylene) undergo trimerization over red-hot iron (Fe) catalyst to give benzene (A). Step 2: Identify compound B. Benzene (A) reacts with acetyl chloride (CH3COCl) in the presence of AlCl3 (Friedel-Crafts acylation) to give acetophenone (methyl phenyl ketone, C6H5COCH3) as compound B. Step 3: Identify C and D. Acetophenone (B) undergoes catalytic hydrogenation with Ni/H2 at 25°C. The C=O group of acetophenone is reduced to give 1-phenylethan-1-ol (C6H5CH(OH)CH3). The carbon bearing the OH group becomes a chiral center (attached to: phenyl, methyl, H, and OH — four different groups). Since the starting material (acetophenone) is achiral and prochiral, and the hydrogenation adds H2 non-stereospecifically (heterogeneous catalysis with Ni), attack of H2 can occur from either face of the carbonyl with equal probability, producing a racemic mixture of (R)- and (S)-1-phenylethan-1-ol. Step 4: Relationship between C and D. C and D are the (R) and (S) enantiomers of 1-phenylethan-1-ol. They are non-superimposable mirror images of each other, i.e., enantiomers. Step 5: Why other options fail. - (a) Identical: They cannot be identical because they are non-superimposable mirror images. - (c) Diastereomers: Diastereomers are stereoisomers that are not mirror images; here C and D are mirror images, so they are not diastereomers. - (d) Position isomers: Position isomers differ in the position of a substituent on the carbon skeleton; C and D have the same connectivity, only differing in spatial arrangement. Therefore, the correct answer is B.