JEE Main · 2025 · 03 Apr 2025 · Shift 1 · Hydrocarbons

Reductive ozonolysis cleaves the ring double bond and leaves a carbonyl on each former alkene carbon. To reach $\text{3-methyl-6-oxoheptanal}$, ${\text{OHC-CH}}_2{\text{-CH(CH}}_3){\text{-CH}}_2{\text{-CH}}_2{\text{-CO-CH}}_3$, the aldehyde end must come from a $=\text{CH-}$ carbon and the methyl ketone end from a $={\text{C(CH}}_3)\text{-}$ carbon, with a further methyl two carbons from the aldehyde. That demands a cyclohexene carrying a methyl on one double-bond carbon and a second methyl para to it, namely 1,4-dimethylcyclohex-1-ene, whose ozonolysis yields 3-methyl-6-oxoheptanal.