Review Of Organic Chemistry Page 15
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34Organic Chemistry I Review: Highlights of Key Reactions, Mechanisms, and Principles
15
8
CH
3
Br
Br
2
(or Cl
)
H
2
Br
3 Notes
Br
Br
Br Br
1. Cation intermediate is cyclic
Br
bromonium (or chloronium) ion
H
Br
Cation
2. The nucleophile captures the
H
H
Capture
bromonium ion via backside attack
-this leads to the trans stereochemistry
3. The nucleophile attacks the bromonium
ion at the *more* substituted carbon
9
CH
3
Br
, H
O
OH
2
2
(or Cl
)
H
2
Br
H
OH
Br Br
O
2
OH
-H
H
Br
H
Br
Cation
Br
H
H
Capture
H
4 Notes
1. Cation intermediate is cyclic bromonium (or chloronium) ion
2. The nucleophile captures the bromonium ion via backside attack (ala SN2)
-this leads to the trans stereochemistry
3. The nucleophile attacks the bromonium ion at the *more* substituted carbon
-this explains the orientation (Markovnikov)
a. There is more + charge at the more substituted carbon
b. The Br-C bond to the more substituted carbon is a lot weaker
H
O
OH
More
-H
H
Substituted
Br
Br
End
H
CH
H
3
Br
Less
Substituted
H
End
Br
Br
H
-H
OH
O
H
H
H
4. Alcohols can function in the same way that water does, resulting in an ether OR rather than
alcohol OH.
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