Chemistry Reference
In-Depth Information
5.17
CH
3
H r
CH
3
CH
3
H r
Br
H
Cl
H
Cl
H
Cl
H
CH
3
(2
S
,3
S
) -2-bromo-
3-chlorobutane
CH
3
(2
R S
) -2-bromo-
3-chlorobutane
CH
3
,3
(2
S
,3
R
3-chlorobutane
) -2-bromo-
These compounds are enantiomers.
This is the enantiomer of (2
R
,3
R
)-2-bromo-3chlorobutane (Fig. 5.12)
5.18
The (2
R
,3
R
) and (2
S
,3
S
) isomers are a pair of enantiomers. Their specific rotations
will be equal in magnitude and opposite in sign.
The (2
R
,3
R
) and (2
S
,3
R
) isomers are a pair of diastereomers. Their specific
rotations will be unequal in magnitude and may or may not differ in sign.
5.19
There are
four
different stereogenic centers, marked below with asterisks. There are,
therefore, 2
4
= 16 possible stereoisomers.
CH
O
C
H
O
*
H
OH
H
OH
*
HO
H
HO
H
*
H
OH
H
OH
*
H
OH
H
OH
CH
2
OH
CH
2
OH
5.20
When the three CH
2
groups are superimposed, the methyl groups of one mirror
image are superimposed on the hydrogens of the other mirror image. The mirror
images are nonsuperimposable and are therefore enantiomers.
H
H
H
3
C
C
H
3
H
H
H
3
C
C
H
3
mirror plane
5.21
cis
-1,2-Dimethylcyclopentane is achiral. It has a mirror plane of symmetry and is a
meso
compound.
H
H
H
3
C
C
H
3
m
irro
r
m
ir
r
or
plane
plane
C
H
3
H
3
C
H
H
