1 (158)

Prévia do material em texto

150 CHAPTER 5 
 
(h) This compound has an internal plane of symmetry, so 
it is a meso compound. As such, it is achiral and 
optically inactive. 
 
 
 
5.58. In each case, begin by numbering the carbon 
atoms in the Fischer projection (from top to bottom) and 
then draw the skeleton of a bond-line drawing with the 
same number of carbon atoms. Then, place the 
substituents in their correct locations (by comparing the 
numbering system in the Fischer projection with the 
numbering system in the bond-line drawing). When 
drawing each substituent in the bond-line drawing, you 
must decide whether it is on a dash or a wedge. For each 
chiral center, make sure that the configuration is the 
same as the configuration in the Fischer projection. If 
necessary, assign the configuration of each chiral center 
in both the Fischer projection and the bond-line drawing 
to ensure that you drew the configuration correctly. 
With enough practice, you may begin to notice some 
trends (rules of thumb) that will allow you to draw the 
configurations more quickly. 
 
(a) 
 
 
(b) 
 
 
(c) 
 
 
 
(d) 
 
 
(e) 
 
 
5.59. 
(a) The compound in part (a) of the previous problem 
has an internal plane of symmetry, and is therefore a 
meso compound: 
 
 
(b) The structures shown in parts (b) and (c) of the 
previous problem are enantiomers. An equal mixture of 
these two compounds is a racemic mixture, which will be 
optically inactive. 
 
(c) Yes, this mixture is expected to be optically active, 
because the structures shown in parts (d) and (e) of the 
previous problem are not enantiomers. They are 
diastereomers, which are not expected to exhibit equal 
and opposite rotations. 
 
 
5.60. As we saw in problem 5.58, it is helpful to use a 
numbering system when converting one type of drawing 
into another. When drawing each substituent in the 
Fischer projection, you must decide whether it is on the 
right or left side of the Fischer projection. For each 
chiral center, make sure that the configuration is the 
same as the configuration in the bond-line drawing. If 
necessary, assign the configuration of each chiral center 
in both the Fischer projection and the bond-line drawing 
to ensure that you drew the configuration correctly. 
With enough practice, you may begin to notice some 
trends (rules of thumb) that will allow you to draw the 
configurations more quickly. 
 
(a) 
H OH
CH2OH
HO H
O
OH
HO
OH
O
OH
OH
12
3
4
1
2
3
4
 
 
 
www.MyEbookNiche.eCrater.com