In the reaction shown below, the total number of possible intramolecular aldol condensation products formed from Y is
← IIT-JEE 2010 · Paper 1![Bicyclo[4.4.0]dec-1(6)-ene (Δ⁹,¹⁰-octalin, two fused six-membered rings sharing a C=C) treated with 1. O₃, 2. Zn, H₂O to give Y (cyclodecane-1,6-dione), then 1. NaOH(aq), 2. heat.](/figures/ja-2010-p1/ja-2010-p1-che-q21-f1.png)
ChemistryInteger+3Question 21 of 84
IIT-JEE 2010 · Paper 1, Chemistry question 21
Answer and worked solution
Official answer: 1
Ozonolysis. The tetrasubstituted C=C shared by the two rings is cleaved, opening the bicycle into a ten-membered ring: Y is cyclodecane-1,6-dione.
Intramolecular aldol. An enolate α to one carbonyl attacks the other carbonyl. By symmetry all four α-carbons are equivalent pairs: an enolate at C2 (or C10) attacking C6 forms a five-membered ring (C2, C3, C4, C5, C6), while attack in the other direction would form a seven-membered ring that is disfavoured relative to it; the five-membered closure with dehydration gives a single bicyclic enone (bicyclo[5.3.0]dec-1(7)-en-2-one).
All favourable pathways lead to the same product.
Answer: 1