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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3o4232

The halide shown is treated with sodium ethoxide in ethanol (reaction I) and with potassium tert-butoxide in tert-butanol (reaction II). Select all correct statements about the major alkene in each case.

  1. AIn reaction I the major alkene is 2-methylbut-2-ene.
  2. BIn reaction II the major alkene is 2-methylbut-1-ene.
  3. C2-Methylbut-2-ene, the product of reaction I, exists as separate E and Z isomers.
  4. DThe halide has eight beta-hydrogens.

Answer: A, B, D

The compound is 2-bromo-2-methylbutane, with 6 H on the two methyl groups and 2 H on the CH2 group (eight beta-hydrogens). Ethoxide gives the Saytzeff product 2-methylbut-2-ene, while the hindered tert-butoxide favours the Hofmann product 2-methylbut-1-ene. 2-Methylbut-2-ene carries two identical methyl groups on one alkene carbon, so it has no E/Z isomers.
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