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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3hx124

3-Methylbut-1-ene reacts with in the absence of peroxide. Which statements are correct?

  1. AThe major product is 1-bromo-3-methylbutane, formed through a primary carbocation
  2. B2-Bromo-3-methylbutane is also formed as a minor product, by direct capture of the secondary carbocation
  3. CThe major product is 2-bromo-2-methylbutane, formed after a 1,2-hydride shift in the initially formed secondary carbocation
  4. DThe tertiary bromide arises by a 1,2-methyl shift which converts the secondary cation into a tertiary cation

Answer: B, C

Protonation of gives the secondary cation . A 1,2-hydride shift from the neighbouring gives the tertiary cation , which gives 2-bromo-2-methylbutane (major). Direct capture gives the minor 2-bromo-3-methylbutane. A primary cation is not formed under ionic conditions, and a methyl shift from that carbon would not give a tertiary cation.
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