The List-II contains products obtained from the reaction of compounds in List-I with O _3/Zn- H _2 O followed by cyclization (via more stable enolate) in the presence of aqueous NaOH. Match each entry in List-I with appropriate entry in List-II and choose the correct option. List-I List-II (P) (1) (Q) (2) (R) (3) (S) (4) (5)
C. P 2; Q 1; R 5; S 3
The given reaction sequence involves ozonolysis of the bicyclic alkenes followed by an intramolecular aldol condensation. For compound (P), the structure is a 6,6-fused system (an octalin derivative) with methyl groups on opposite sides of the double bond. Ozonolysis cleaves the central double bond to form a 10-membered ring 1,6-diketone with methyl groups at the -positions (C2 and C7). The base-catalyzed aldol condensation proceeds via the more stable trisubstituted enolate at C2, which attacks the C6 carbonyl group. This cyclization forms a new 5-membered ring fused to a 7-membered ring (a 5,7-fused system). The fusion carbons are C2 (bearing a methyl group) and C6 (bearing a hydroxyl group). The unreacted ketone is at C1, and the other methyl group is at C7. Both C1 and C7 are in the 7-membered ring. This matches the structure of product (2). Thus, P 2. For compound (Q), the structure is a 7,5-fused system with methyl groups on different rings. Ozonolysis yields a 10-membered ring 1,7-diketone with methyl groups at C2 and C10. The more stable enolate at C2 attacks the C7 carbonyl group. This forms a 6-membered ring fused to another 6-membered ring (a 6,6-fused system). The fusion carbons are C2 (with a methyl group) and C7 (with a hydroxyl group). The unreacted ketone at C1 and the remaining methyl at C10 are both located in the same 6-membered ring. This corresponds to the structure of product (1). Thus, Q 1. For compound (R), the structure is a 7,5-fused system with both methyl groups on the 7-membered ring. Ozonolysis produces a 10-membered ring 1,7-diketone with methyl groups at C2 and C6. The enolate at C2 attacks the C7 carbonyl, forming a 6,6-fused system. The fusion carbons are C2 (methyl) and C7 (hydroxyl). The unreacted ketone is at C1 (in one ring) and the remaining methyl is at C6 (in the other ring). This corresponds to product (5). Thus, R 5. For compound (S), the structure is a 6,6-fused system with both methyl groups on the same side. Ozonolysis forms a 10-membered ring 1,6-diketone with methyl groups at C2 and C5. The enolate at C2 attacks the C6 carbonyl, yielding a 5,7-fused system. The fusion carbons are C2 (methyl) and C6 (hydroxyl). The unreacted ketone is at C1 (in the 7-membered ring) and the remaining methyl is at C5 (in the 5-membered ring). This corresponds to product (3). Thus, S 3. Combining these results, the correct matching is P 2; Q 1; R 5; S 3.
Related: Chemistry — Hydrocarbons · All PYQ Banks