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JEE Advanced levelSingle correct optionDifficulty 3 of 3o4018

Match each alcohol in List I with its major alkene from heating with concentrated (List II). List I: P = 3-methylbutan-2-ol; Q = 2-methylpropan-2-ol; R = 3,3-dimethylbutan-2-ol; S = 2-methylcyclohexanol. List II: 1 = 1-methylcyclohexene; 2 = 2-methylbut-2-ene; 3 = 2-methylpropene; 4 = 2,3-dimethylbut-2-ene.

  1. AP-4, Q-3, R-2, S-1
  2. BP-2, Q-3, R-1, S-4
  3. CP-2, Q-3, R-4, S-1
  4. DP-3, Q-2, R-4, S-1

Answer: C

P: hydride shift to the tertiary cation, then Saytzeff elimination gives 2-methylbut-2-ene. Q: tertiary cation gives 2-methylpropene (no other alkene possible). R: methyl shift to the tertiary cation gives 2,3-dimethylbut-2-ene. S: secondary cation, loss of the tertiary H (or hydride shift to the tertiary cation) gives 1-methylcyclohexene. So P-2, Q-3, R-4, S-1.
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