Chemistry Reference
In-Depth Information
16.30
H
OH
2
C
H
OH
2
C
H
H
OH
2
C
H
+
H
O
OH
H
O
OH
H
O
OH
+H
+
OH
H
OH
H
OH
H
+
-H
+
HO
H
HO
H
HO
H
H
OH
H
OH
H
OH
β
-D-glucopyranose
rotation
H
OH
2
C
H
OH
2
C
H
H
OH
2
C
H
+
H
O
H
H
O
H
H
O
H
-H
+
OH
H
OH
H
OH
H
+
+H
+
HO
OH
HO
OH
HO
OH
H
OH
H
OH
H
OH
α
-D-glucopyranose
16.31
a.
For the structure, see Sec. 16.12c. The
α
form is shown. The
β
form is
identical with it, except for the configuration at C-1 in the “right-hand” unit,
where the OH group is equatorial instead of axial.
b.
Follow Example 16.4 or Prob. 16.29 as guides for the calculation.
92.6 -
52
40.6
58 .6
x
x 1 00 = 6 9.3 %
% of
β
=
100 =
92.6 - 34
16.32
The structures are shown in Figure 16.1. Oxidation of
D
-erythrose gives optically
inactive
meso
-tartaric acid:
CH
O
CH
2
OH
OH
H
OH
H
H
OH
H
OH
CH
2
OH
CH
2
OH
D-erythrose
meso
-tartaric acid
(optically inactive)
Analogous oxidation of
D
-threose gives an optically active tartaric acid:
CH
O
CO
2
H
H
O
H
H
H
H
OH
H
OH
CH
2
OH
CO
2
H
D-threose
S,S
-tartaric acid
(optically inactive)
In this way, we can readily assign structures to the two tetroses.
