See image — Aromatic Hydrocarbons Chemistry Question

💡 Solution & Explanation

Step 1 - Identify the starting material: The starting material is 2-benzylbenzoic acid, which has a COOH group and a CH2C6H5 (benzyl) group at the ortho positions on a benzene ring. Step 2 - Reaction with SOCl2 converts the carboxylic acid (-COOH) to an acid chloride (-COCl), giving 2-benzylbenzoyl chloride (intermediate after SOCl2). Step 3 - Intramolecular Friedel-Crafts acylation with anhydrous AlCl3: The acid chloride undergoes intramolecular Friedel-Crafts acylation. The acyl chloride attacks the pendant phenyl ring of the benzyl group. This closes a six-membered ring (the carbonyl carbon bridges between the two aromatic rings via the CH2 unit), forming a cyclic ketone. The product A is 9,10-dihydroanthracen-9-one (anthrone), i.e., a tricyclic compound where the central ring is a six-membered ring containing a C=O at position 9, with two CH2 groups at positions 9 and 10... More precisely: the ring closure gives a six-membered ring fused to both benzene rings with a ketone. This product A is anthrone (10H-anthracen-9-one), a tricyclic compound: two benzene rings fused to a central cyclohexanone-like ring with C=O and one CH2 (at C10). Actually the structure is: the central ring has C=O (from acyl) and one -CH2- (from the original benzyl CH2), making it a six-membered ring with one ketone group - this is anthrone (9(10H)-anthracenone). Step 4 - Clemmensen reduction (Zn-Hg / Conc. HCl) reduces the ketone (C=O) to CH2. This converts anthrone (A) to 9,10-dihydroanthracene (B), where the central ring is fully saturated at positions 9 and 10 (both are CH2 groups), and both outer rings are benzene rings. Step 5 - Verify the answer: Product B is 9,10-dihydroanthracene, which matches option (b) - two benzene rings fused to a central six-membered ring with two sp3 CH2 carbons. Why other options fail: - Option (a) is the ketone A (anthrone), not B after Clemmensen reduction. - Option (c) anthracene would require dehydrogenation, not Clemmensen reduction. - Option (d) would require a different reaction pathway entirely. Therefore, the correct answer is B.