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NEET levelSingle correct optionDifficulty 1 of 3o4235

The compound shown (the tert-butyl group locks the ring) is treated with a strong base such as sodium ethoxide. Compared with its diastereomer, it undergoes E2 elimination

  1. Aslower, because the axial bromine is shielded by the tert-butyl group
  2. Bmuch slower, because in its preferred chair the bromine is equatorial
  3. Cmuch faster, because in its preferred chair the bromine is axial and has anti-periplanar axial beta-hydrogens
  4. Dat the same rate, because both isomers give the same alkene

Answer: C

The cis isomer of 1-bromo-4-tert-butylcyclohexane has the tert-butyl group equatorial and therefore bromine axial. An axial bromine is anti-periplanar to the axial hydrogens on C-2 and C-6, which is the geometry required for E2, so it reacts much faster than the trans isomer.
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