JEE Main · 2026 · 04 Apr 2026 · Shift 1 · Hydrocarbons

Reductive ozonolysis cleaves every carbon--carbon double bond into two carbonyl groups. Reading back from the products, the two molecules of methanal arise from two exocyclic $=\mathrm{CH}{}_2$ groups; the fragment $\mathrm{OHC}-\mathrm{CO}-\mathrm{CHO}$ arises from three consecutive ring carbons whose central carbon carried an exocyclic methylene and whose outer two were ring $=\mathrm{CH}-$ carbons; and the fragment $\mathrm{CH}{}_3-\mathrm{CO}-\mathrm{CO}-\mathrm{CO}-\mathrm{CH}{}_3$ arises from three consecutive ring carbons whose central carbon carried an exocyclic methylene and whose outer two were methyl-bearing ring $=\mathrm{C}(\mathrm{CH}{}_3)-$ carbons. Rejoining these pieces at the cleaved double bonds reproduces a cyclohexa-1,4-diene that bears a methyl group on each of the two double-bond carbons of one fragment and an exocyclic $=\mathrm{CH}{}_2$ on each of the two ring carbons that become ketonic; this is the structure of alkene X.