Top side open to attack :Br:- Br H H Br :Br: Br H + Bottom side shielded from attack Cyclopentene Bromonium ion trans-1,2-Dibromo- intermediate cyclopentane 2004 Thomson-Brooks/Cole
Bromonium Ion is Opened Equally from Both Sides Br2 Br Br ⊕ B Br
Bromonium Ion is Opened Equally from Both Sides Br2 Br Br Br Br Br Br Br Br Br Br + -
Definitions Stereospecific-only one stereoisomer is formed at the expense of the other (e.g. trans vs.cis) Stereoselective-one stereoisomer is formed preferentially over the other
Definitions • Stereospecific – only one stereoisomer is formed at the expense of the other (e.g. trans vs. cis) • Stereoselective – one stereoisomer is formed preferentially over the other
Anti-Addition Stereospecific Reaction Anti-addition Br Br Br2 ""Br Br
Anti-Addition Stereospecific Reaction Anti-addition Br Br Br Br + Br2
Bromonium Ion Intermediate 8+ Br Br-Br "Br Bi Bromonium ion
Bromonium Ion Intermediate Bromonium ion - Br Br Br Br Br + Br Br