Chemistry Reference
In-Depth Information
the Cahn-Ingold-Prelog convention is (
R
) since one sulfur atom in
the side-chain takes priority over the two oxygens in the COO
group.
Q
2 Draw Fischer projections of
HOH
2
C
CH(OH)
CH(OH)
CH
2
OH to illustrate
a
a
a
(a)
A pair of enantiomers
(b)
A pair of diastereoisomers
(c)
A meso compound
A
2 The answers are shown in Figure 4.20. Structures (1) and (2)
are enantiomeric pairs. Structures (1) and (3) and structures (2)
and (3) are pairs of diastereoisomers (or diastereomers), while
structure (3) is a meso compound. A meso compound is optically
inactive since it possesses a plane of symmetry and is superimpos-
able on its mirror image. It does, however, contain two chiral
carbon atoms. This reminds us that
not all compounds that
contain chiral centres are optically active
.
CH
2
OH
CH
2
OH
CH
2
OH
HO
H
H
OH
H
OH
Plane
of
symmetry
H
OH
HO
H
H
OH
CH
2
OH
CH
2
OH
CH
2
OH
(1)
(2)
(3)
Figure 4.20
Enantiomers, diastereoisomers and a meso compound.
