Natural rubber on complete ozonolysis (O3/Zn−H2O) gives compound X as the major product. X gives positive iodoform and Tollen's tests. X on heating with aqueous NaOH gives Y as the major product. Y is
(A)(see structure)✓ Correct
(B)(see structure)
(C)(see structure)
(D)(see structure)
Answer: (A)
Solution
Natural rubber (polyisoprene) on ozonolysis cleaves the C=C double bonds. The repeating unit of natural rubber is isoprene (2-methyl-1,3-butadiene).
Ozonolysis followed by reductive workup gives levulinaldehyde (4-oxopentanal) as compound X, which has both an aldehyde group (gives positive Tollen's test) and a methyl ketone group (gives positive iodoform test).
When X is heated with aqueous NaOH, it undergoes intramolecular aldol condensation to form a cyclic product Y, which is cyclopent-2-enone (the structure shown in option A).
JEE Advanced · 2026 · 17 May 2026 · Paper 2 · Single correct option
