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696 Chapter 20
Copyright © 2017 Pearson Education, Inc.
Knowing that the hexose is oxidized by Tollens reagent to the aldonic acids d-talonic acid and d-galactonic
acid tells us that the aldonic acids and the ketohexose have the same configuration at C-3, C-4, and C-5.
Therefore, the hexose is d-tagatose.
COOH
H
HO H
HO H
H OH
CH
2
OH
D
-talonic acid
HO
COOH
OH
HO H
HO H
H OH
CH
2
OH
D
-galactonic acid
H
CH
2
OH
C O
HO H
HO H
H OH
CH
2
OH
D
-tagatose
63.
H
CHOH
C
CH
2
OH
H OH
H OH
HO H
O
DO
−
CHOH
C
CH
2
OH
H OH
H OH
HO H
O
D OD
−
H
CDOH
C
CH
2
OH
H OH
H OH
HO H
O
D
-fructose with one deuterium
CDOH
C
CH
2
OH
H OH
H OH
HO H
O
D OD
CD
2
OH
C
CH
2
OH
OH
H
OH
H
H HO
O
D
-fructose with two deuteriums
DO
−
−
64.
a.
O
HO
HO
CH
2
OH
HO
OH
b.
OHO
HO
OH
CH
2
OH
HO
c.
O
OH
HO
OH
CH
2
OH
HO
d.
O
OH
OH OH
CH
2
OH
HOCH
2
e.
O
HO
HO
HO
OH
HOCH
2
f.
O
OH
HOCH
2
OH
OH
OH