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JEE Main 2019 · Chemistry · Hydrocarbons · medium

A hydrocarbon X (C7H12) undergoes ozonolysis followed by reductive work-up (Zn/H2O) to give a single compound of formula C7H12O2, which gives a…

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A hydrocarbon X (C7H12\mathrm{C_7H_{12}}) undergoes ozonolysis followed by reductive work-up (Zn/H2O\mathrm{Zn/H_2O}) to give a single compound of formula C7H12O2\mathrm{C_7H_{12}O_2}, which gives a silver mirror with Tollens' reagent and also a yellow precipitate with I2/NaOH\mathrm{I_2/NaOH}. X is
  1. A. 3-methylcyclohexene
  2. B. methylenecyclohexane
  3. C. 1-methylcyclohexene
  4. D. 4-methylcyclohexene
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Answer: (C) 1-methylcyclohexene

C7H12\mathrm{C_7H_{12}} has two degrees of unsaturation; one product with the same carbon count means a ring alkene whose cleavage opens the ring. A single product with Tollens' (a −CHO-\mathrm{CHO}) and iodoform (a CH3CO−\mathrm{CH_3CO-}) tests must be CH3CO(CH2)4CHO\mathrm{CH_3CO(CH_2)_4CHO} (6-oxoheptanal), which comes from 1-methylcyclohexene. 3- and 4-methylcyclohexene give dialdehydes (no iodoform), and methylenecyclohexane gives two products (cyclohexanone and methanal).
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