X2 Addition to Alkenes: Halogenation

Electrophilic Addition of X₂ to Alkenes: Halogenation

• Stereochemistry is anti (anti-addition), there is no regiochemistry.
• Two-step mechanism with halonium ion intermediate (i.e bromonium cation
  intermediate in case of Br2).
• Stereochemistry controlled by backside attack of X^- to halonium ion.
• Rearrangements don't occur, rearrangements only occur with carbocation
  intermediates.
• Evidence for this mechanism.
  • No observation of rearrangements
  • anti-addition product.