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What is the major final product formed when 2-methylpentane is subjected to the following reaction sequence? (i) Br ₂ , h (ii) Alc. KOH, (iii) HBr, R-O-O-R, h

Options

  1. A2-bromo-2-methylpentane
  2. B3-bromo-2-methylpentane
  3. C1-bromo-2-methylpentane
  4. D2-bromo-4-methylpentane

Correct answer

B. 3-bromo-2-methylpentane

Step-by-step solution

The reaction sequence involves three steps: Step 1: Free radical bromination of 2-methylpentane. The tertiary C-H bond is the most reactive, leading to the formation of 2-bromo-2-methylpentane. CH ₃ -CH(CH ₃ )-CH ₂ -CH ₂ -CH ₃ Br ₂, h CH ₃ -C(Br)(CH ₃ )-CH ₂ -CH ₂ -CH ₃ Step 2: Dehydrohalogenation with alcoholic KOH and heat. Following Saytzeff's rule, the more substituted alkene is formed as the major product. CH ₃ -C(Br)(CH ₃ )-CH ₂ -CH ₂ -CH ₃ Alc. KOH , CH ₃ -C(CH ₃ )=CH-CH ₂ -CH ₃ (2-methylpent-2-ene) Step 3:

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