Transcript CH 8-3 Power Point

CH 8-3: Electrophilic Addition of Br2 and Cl2
(1) Electrophilic Addition of HX (HCl & HBr)
-Carbocation mechanism
-Regioselective: Markovnikov’s Rule
-Non-stereospecific reaction
-Rearrangements possible
(2) Electrophilic Addition of H2O and ROH
-Acid catalysis
-Carbocation mechanism
-Rearrangements possible
(3) Electrophilic Addition of Br2 and Cl2 to alkenes
-”Halonium ion” mechanism
-No carbocation!!!
-Stereospecific reaction – Anti-Addition
Electrophilic Addition of Br2 or Cl2 to Alkenes
Part I: Dihalide Products (no other nucleophile)
Stereospecific Anti-Addition of Electrophile and Nucleophile
Electrophilic Addition of Br2 or Cl2 to Alkenes
•The mechanism for halogen addition involves a new
intermediate, the “halonium ion” (no carbocation):

+
bromonium ion
•Since there is no carbocation, there are no rearrangements!
Electrophilic Addition of Br2 or Cl2 to Alkenes
•The mechanism for halogen addition involves a new
intermediate, the “halonium ion” (no carbocation):
•The nucleophile must add anti = stereospecific.
Electrophilic Addition of Br2 or Cl2 to Alkenes
Part II: “Second” Nucleophile
•Anti-Addition of electrophile and a second nucleophile.