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JEE Advanced levelSingle correct optionDifficulty 3 of 3g3147

3-Methylbut-1-ene reacts with (i) in the dark in a polar medium, and (ii) in the presence of a peroxide. The major products are, respectively,

  1. A(i) 2-bromo-3-methylbutane; (ii) 1-bromo-3-methylbutane
  2. B(i) 2-bromo-2-methylbutane; (ii) 1-bromo-3-methylbutane
  3. C(i) 1-bromo-3-methylbutane; (ii) 2-bromo-2-methylbutane
  4. D(i) 2-bromo-2-methylbutane; (ii) 2-bromo-3-methylbutane

Answer: B

In the ionic path the proton adds to C1 to give a secondary cation, which undergoes a 1,2-hydride shift to the tertiary cation. The bromide then gives 2-bromo-2-methylbutane. In the radical path adds to C1 and the resulting secondary radical takes H from without rearrangement, so 1-bromo-3-methylbutane forms.
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