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Chapter 6 227
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3.
cis
-2-Butene forms a meso compound; the product has two asymmetric centers, and only syn
addition occurs.
O
C C
CH
3
H
H
CH
3
trans
-2-Butene forms a pair of enantiomers; the product has two asymmetric centers, and only
syn addition occurs.
O
C C
H CH
3
H
CH
3
O
C C
CH
3
H
CH
3
H
4.
cis
-2-Butene forms the threo pair of enantiomers; a product with two asymmetric centers is
formed, and only anti addition of
Br
2
occurs.
trans
-2-Butene forms a meso compound; a product with two asymmetric centers is formed, and only
anti addition of Br
2
occurs.
CC
CH
3
Br
H
Br
H
C C
H
3
C
Br
CH
3
H
Br
H
+
CH
3
H Br
CH
3
Br
H
CH
3
H
Br
CH
3
Br
H
or
S S
R R
S
S
R
R
CH
3
C C
H
3
C
Br
CH
3
Br
H
H
CH
3
Br
H
CH
3
Br
H
or
S R
S
R
5.
cis
-2-Butene forms the threo pair of enantiomers; a product with two asymmetric centers is
formed, and only anti addition of Br and OH occurs.
C C
H
3
C
H
HO
CH
3
C C
H
Br
OH
CH
3
or
CH
3
CH
3
OH
H
H
Br
CH
3
CH
3
H
HO
Br
H
H
Br
C C
H
3
C
H
H
CH
3
or
CH
3
CH
3
H
HO
H
Br
CH
3
CH
3
OH
H
Br
H
HO
Br
H
C C
H
Br
H
CH
3
OH
trans
-2-Butene forms the erythro pair of enantiomers; a product with two asymmetric centers is
formed, and only anti addition of Br and OH occurs.
S S
R R
S
S
R
R
R S
R S
R
S
S
R
CH
3
CH
3
6.
Both
cis
- and
trans
-2-butene form this product; a product with no asymmetric centers is formed.
CH
3
CH
2
CH
2
CH
3