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JEE Main levelSingle correct optionDifficulty 2 of 3st282

The compound shown is 1,2-dimethylcyclohexane with both methyl groups drawn on the same face of the ring. Considering configuration only (treat the ring as planar), which statement is correct?

  1. AIt is achiral and superimposable on its mirror image
  2. BIt is chiral because C1 and C2 are both stereocentres
  3. CIt can be resolved into two optically active enantiomers
  4. DIt is identical to the isomer with the two methyl groups on opposite faces

Answer: A

The compound is cis-1,2-dimethylcyclohexane, (1R,2S). Although C1 and C2 are stereocentres, the molecule has a mirror plane that bisects the C1-C2 bond and the C4-C5 bond. So it is a meso compound: achiral and not resolvable. The trans isomer, with methyl groups on opposite faces, is a diastereomer of the cis isomer and is chiral.
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