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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3o4033

cis-1-Bromo-2-methylcyclohexane and trans-1-bromo-2-methylcyclohexane are each treated with in ethanol (E2). Which of the following is/are correct?

  1. AThe trans isomer reacts through the chair in which Br and are both axial.
  2. BThe trans isomer gives 1-methylcyclohexene as the major product.
  3. CThe cis isomer gives mainly 1-methylcyclohexene.
  4. DThe trans isomer gives only 3-methylcyclohexene.

Answer: A, C, D

The trans isomer must react in the diaxial chair (Br and CH3 both axial). There the H on C-2 is equatorial, so the only anti H is on C-6 and 3-methylcyclohexene is the sole alkene. In the cis isomer the chair with Br axial has CH3 equatorial, so the C-2 axial H is anti and the Saytzeff alkene, 1-methylcyclohexene, is the major product.
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