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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3o4202

trans-1-Bromo-4-tert-butylcyclohexane and cis-1-bromo-4-tert-butylcyclohexane react with in ethanol; the tert-butyl group stays equatorial. Which statements are correct?

  1. AIn the cis isomer Br is axial.
  2. BIn the trans isomer Br is axial and so is eliminated faster.
  3. CThe cis isomer undergoes E2 using axial hydrogens on C2 and C6 that are anti to Br.
  4. DThe only constitutional alkene possible from either isomer is 4-tert-butylcyclohexene, and the trans isomer forms it much more slowly.

Answer: A, C, D

With tert-butyl equatorial, the 1,4-cis isomer must have axial Br and the 1,4-trans isomer equatorial Br, so statement 2 is wrong. The cis isomer has axial Br anti to axial H on both C2 and C6, so it reacts rapidly. Either isomer can only give 4-tert-butylcyclohexene, but the trans isomer has no anti-periplanar H and reacts much more slowly. Statements 1, 3 and 4 are correct.
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