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JEE Advanced levelSingle correct optionDifficulty 3 of 3o2105

Assertion (A): In the presence of a peroxide, HBr adds to propene to give 1-bromopropane. Reason (R): The bromine atom adds to the terminal carbon to form the more stable secondary alkyl radical.

  1. ABoth A and R are true and R is the correct explanation of A
  2. BBoth A and R are true but R is not the correct explanation of A
  3. CA is true but R is false
  4. DA is false but R is true

Answer: A

The chain mechanism begins with adding to the carbon that leads to the more stable radical. Addition at the terminal carbon gives a secondary radical (versus primary at the middle carbon), and H transfer from HBr yields 1-bromopropane. Both statements are true and R explains A.
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