1. No category

CH610A/618A Sophomore Organic I
Dr. Brian Pagenkopf
Bromination:
+
Bromination: Intermediate
Bromonium Ion
+
Br
2
Br
Why a Bromonium Ion?
Br
bromonium ion
Br
3
Br
Br2
Br
Br2
Br
+
1
1
Br
Br
but not:
Why a Bromonium Ion?
Stereochemical Consequences of
Bromonium Ion
identical / meso
Br2
Br
+
Br
enantiomers
- Bromine is big
- Charge shared over more atoms
E
identical / meso
Br
Br
Br
Br
F
G
Br
Br
Br
Br
not observed H
1
Assume Carbocation Intermediate:
Gives Wrong Result
Stereochemical Consequences of
Bromonium Ion: Gives Right
Result
Both cis and trans would be formed from a carbocation intermediate
C-Br Bonding
the sp3 bonding orbital
C
C
Br
the anti-bonding orbital: opposite in direction, phase and size
C
to break the C-Br bond, electrons enter the large
lobe of the antibonding orbital - which points
away from the C-Br bond.
anti-bonding orbital
C
Br
Nu C
+
Br¯
Nu
2