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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3st217

Menthyl chloride (Cl, isopropyl and CH all equatorial in its preferred chair, with the same relative configuration as menthol) and neomenthyl chloride (Cl axial, isopropyl and CH equatorial in its preferred chair) undergo E2 elimination. Which statements are correct?

  1. AE2 of menthyl chloride requires the chair in which Cl, isopropyl and CH are all axial
  2. BNeomenthyl chloride undergoes E2 faster than menthyl chloride
  3. CMenthyl chloride gives mainly the alkene with the C=C between the former C1 and C2
  4. DIn the reactive conformer of menthyl chloride the C2-H is anti-periplanar to Cl

Answer: A, B

E2 needs the leaving group and the beta-H anti-periplanar, i.e. both axial. In menthyl chloride Cl is equatorial in the stable chair, so the ring must flip to the all-axial form, which is high in energy; in that form the C2 isopropyl is axial, so the C2-H is equatorial and not anti to Cl, and only the C6-H is available (less substituted alkene). Neomenthyl chloride already has axial Cl in its stable chair with axial H on C2 and C6, so it eliminates faster.
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