Question

The List-I contains products obtained from the reaction of compounds in List-I with \(\mathrm{O_3/Zn-H_2O}\) followed by cyclization (via more stable enolate) in the presence of aqueous \(\mathrm{NaOH}\). Match each entry in List-I with appropriate entry in List-II and choose the correct option.

• A. \(P \rightarrow 2;\ Q \rightarrow 4;\ R \rightarrow 1;\ S \rightarrow 3\)
• B. \(P \rightarrow 3;\ Q \rightarrow 4;\ R \rightarrow 5;\ S \rightarrow 2\)
• C. \(P \rightarrow 2;\ Q \rightarrow 1;\ R \rightarrow 5;\ S \rightarrow 3\)
• D. \(P \rightarrow 3;\ Q \rightarrow 5;\ R \rightarrow 4;\ S \rightarrow 2\)

Hint:

Important reactions involved:
• Ozonolysis: \[ \mathrm{C=C \xrightarrow[Zn/H_2O]{O_3} Carbonyl\ compounds} \]
• Intramolecular aldol reaction: Enolate attacks intramolecular carbonyl center to form cyclic \(\beta\)-hydroxy carbonyl compounds.
• More substituted enolates are generally more stable and dominate under thermodynamic conditions. In cyclic systems, always analyze:
• ring strain
• favored ring size
• stability of enolate intermediate before predicting the major cyclized product.

Answer 1

The Correct Option is B

Concept: This problem involves:
• Ozonolysis of cyclic alkenes
• Formation of diketone or keto-aldehyde intermediates
• Intramolecular aldol cyclization
• Preference for formation through the more stable enolate The overall strategy is:
• Identify the position of double bond cleavage after ozonolysis
• Determine the carbonyl compounds formed
• Predict intramolecular aldol condensation product
• Match with structures in List-II

Step 1: Analyzing compound \(P\). Compound \(P\) is a fused bicyclic alkene containing methyl substituents. On ozonolysis:
• the double bond gets cleaved
• two carbonyl groups are formed Under aqueous \(\mathrm{NaOH}\), intramolecular aldol cyclization occurs. The cyclization proceeds through the more substituted and more stable enolate. After careful structural analysis, the product formed corresponds to structure \((3)\). Thus: \[ P \rightarrow 3 \]

Step 2: Analyzing compound \(Q\). After ozonolysis of \(Q\), a diketone intermediate forms. Because of the ring geometry and substituent arrangement, aldol cyclization gives the bridged hydroxy ketone represented by structure \((4)\). Therefore: \[ Q \rightarrow 4 \]

Step 3: Analyzing compound \(R\). Ozonolysis of \(R\) followed by base-induced cyclization produces a bicyclic hydroxy ketone. The stereochemical arrangement and carbonyl position match structure \((5)\). Hence: \[ R \rightarrow 5 \]

Step 4: Analyzing compound \(S\). Compound \(S\) gives a diketone intermediate after ozonolysis. Cyclization through the thermodynamically more stable enolate produces structure \((2)\). Therefore: \[ S \rightarrow 2 \]

Step 5: Final matching. Thus the correct matching is: \[ P \rightarrow 3 \] \[ Q \rightarrow 4 \] \[ R \rightarrow 5 \] \[ S \rightarrow 2 \] This corresponds to option (B). Final Answer: \[ \boxed{(B)} \]