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JEE Advanced levelSingle correct optionDifficulty 3 of 3o4254

The alcohol shown is heated with concentrated sulfuric acid. Which structure is the major alkene?

  1. AStructure A
  2. BStructure B
  3. CStructure C
  4. DStructure D

Answer: B

The alcohol is 2,2-dimethylcyclohexanol. It forms a secondary cation, but no beta-hydrogen exists on the quaternary C-2, so a methyl group shifts and gives a tertiary 1,2-dimethylcyclohexyl cation. Loss of the adjacent hydrogen gives the tetrasubstituted 1,2-dimethylcyclohexene, the most stable alkene. 3,3-Dimethylcyclohexene is the unrearranged, minor product.
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