Halogenation of Alkenes: Bromonium/Chloronium Ions and Anti Addition

Master alkene halogenation (Br2/Cl2). Bromonium ion intermediate, anti addition stereochemistry, and how solvents change the outcome (halohydrins).

  • Reaction: Alkene + Br2/Cl2 → Vicinal dihalide
  • What it does: Adds two halogens across a double bond
  • Typical reagents: Br2 (CCl4, CH2Cl2), Cl2
  • Key intermediate: Halonium ion (bromonium/chloronium)
  • Driving force: Formation of two C–X bonds; relief of π bond
  • Exam type: Stereochemistry
  • Exam type: Predict product

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