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Chapter 9 339
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2.
Add the remaining groups to the structure in a way that gives the asymmetric centers the desired
configurations. For example, the structure below is (3
S
,4
S
)-3-bromo-3,4-dimethylhexane.
CH
3
CH
3
CH
3
CH
2
CH
2
CH
3
C C
Br
H
(3
S
,4
S
)-3-bromo-3,4-dimethylhexane
3.
Because the groups to be eliminated are both attached to solid lines, they are anti to each other.
CH
3
CH
3
CH
3
CH
2
CH
2
CH
3
C C
Br
H
4.
Once the groups are eliminated, you can draw the structure of the alkene product. (The groups
attached to the solid wedges are on the same side of the double bond, and the groups attached by
hatched wedges are on the other side of the double bond.)
CH
3
CH
3
CH
3
CH
2
CH
2
CH
3
(
E
)-3,4-dimethyl-3-hexene
C C
The configuration of the elimination product obtained from each of the other three stereoisomers
can be determined in the same way.
CH
3
CH
3
CH
2
CH
3
CH
2
CH
3
(
Z
)-3,4-dimethyl-3-hexene
(3
S
,4
R
)-3-bromo-3,4-dimethylhexane
C C
CH
3
CH
3
CH
3
CH
2
CH
2
CH
3
C C
Br
H
CH
3
CH
3
CH
2
CH
2
CH
3
CH
3
(
E
)-3,4-dimethyl-3-hexene
(3
R
,4
R
)-3-bromo-3,4-dimethylhexane
C C
CH
3
CH
3
CH
2
CH
2
CH
2
CH
3
C C
Br
H
CH
3
CH
2
CH
2
CH
2
CH
3
CH
3
(
Z
)-3,4-dimethyl-3-hexene
(3
R
,4
S
)-3-bromo-3,4-dimethylhexane
C C
CH
3
CH
2
CH
2
CH
3
CH
2
CH
3
C C
Br
H