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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3o4247

The compound shown is treated with sodium ethoxide in ethanol and reacts by E2. Select all correct statements.

  1. AThe reactive chair conformer has bromine and the isopropyl group both axial.
  2. BOnly one ring hydrogen is anti-periplanar to bromine in the reactive chair.
  3. C1-Isopropylcyclohexene is the major alkene.
  4. DThe cis diastereomer gives 1-isopropylcyclohexene as its major alkene.

Answer: A, B, D

The compound is trans-1-bromo-2-isopropylcyclohexane. Bromine must be axial, which forces the trans isopropyl group axial too, so the C-2 hydrogen is equatorial and only the C-6 axial hydrogen is anti to bromine; the alkene formed is 3-isopropylcyclohexene, not 1-isopropylcyclohexene. In the cis isomer bromine is axial with isopropyl equatorial, leaving an axial C-2 hydrogen anti to bromine and giving the Saytzeff alkene.
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