Allylic Bromination (NBS): Selective Radical Substitution at Allylic Sites

Master allylic bromination with NBS: radical chain mechanism, why it targets allylic positions, and how resonance creates product mixtures. Includes interactive steps + practice.

  • Reagents: NBS, hv (or peroxide), often in solvent like CCl4
  • Selectivity: Targets allylic (and benzylic) positions due to radical stabilization
  • Mechanism type: Radical chain; Br2 generated in situ
  • Common outcome: Mixture of allylic bromides due to resonance
  • Exam type: Predict the major product
  • Exam type: Rate / selectivity
  • Exam type: Failure modes / distractors

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