Chapter 24
Carbohydrates
Review of Concepts
Fill in the blanks below. To verify that your answers are correct, look in your textbook at
the end of Chapter 24. Each of the sentences below appears verbatim in the section
entitled Review of Concepts and Vocabulary.
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Carbohydrates are polyhydroxy ___________ or ketones.
Simple sugars are called _______________ and are generally classified as
aldoses and _________.
For all D sugars, the chirality center farthest from the carbonyl group has the ___
configuration.
Aldohexoses can form cyclic hemi______ that exhibit a pyranose ring.
Cyclization produces two stereoisomeric hemiacetals, called ___________. The
newly created chirality center is called the ___________ carbon.
In the α anomer, the hydroxyl group at the anomeric position is ______ to the
CH2OH group, while in the β anomer, the hydroxyl group is ______ to the
CH2OH group.
Anomers equilibrate by a process called _____________, which is catalyzed by
either ______ or _______.
Some carbohydrates, such as D-fructose, can also form five-membered rings,
called ___________ rings.
Monosaccharides are converted into their ester derivatives when treated with
excess _____________________________.
Monosaccharides are converted into their ether derivatives when treated with
excess ___________________ and silver oxide.
When treated with an alcohol under acid-catalyzed conditions, monosaccharides
are converted into acetals, called ___________. Both anomers are formed.
Upon treatment with sodium borohydride an aldose or ketose can be reduced to
yield an ___________.
When treated with a suitable oxidizing agent, an aldose can be oxidized to yield
an __________.
When treated with HNO3 , an aldose is oxidized to give a dicarboxylic acid called
an _______________.
D-Glucose and D-mannose are epimers and are interconverted under strongly
__________ conditions.
The Kiliani-Fischer synthesis can be used to lengthen the chain of an ________.
The Wohl degradation can be used to shorten the chain of an _________.
________________ are comprised of two monosaccharide units, joined together
via a glycosidic linkage.
Polysaccharides are polymers consisting of repeating monosaccharide units
linked by ____________ bonds.
When treated with an ________ in the presence of an acid catalyst,
monosaccharides are converted into their corresponding N-glycosides.
640
CHAPTER 24
Review of Skills
Fill in the blanks and empty boxes below. To verify that your answers are correct, look
in your textbook at the end of Chapter 24. The answers appear in the section entitled
SkillBuilder Review.
24.1 Drawing the Cyclic Hemiacetal of a Hydroxyaldehyde
DRAW THE CYCLIC HEMIACETAL THAT IS FORMED WHEN THE FOLLOWING HYDROXYALDEHYDE
UNDERGOES CYCLIZATION UNDER ACIDIC CONDITIONS.
O
HO
[ H+ ]
H
24.2: Drawing a Haworth Projection of an Aldohexose
DRAW A HAWORTH PROJECTION OF α-D-GALACTOPYRANOSE.
H
H
HO
HO
H
O
OH
H
H
OH
CH2OH
[ H+ ]
D-GALACTOSE
24.3: Drawing the More Stable Chair Conformation of a Pyranose Ring
DRAW THE MORE STABLE CHAIR CONFORMATION OF α-D-GALACTOPYRANOSE.
HOCH2
OH
O
OH
OH
OH
α-D-GALACTOPYRANOSE
MORE STABLE CHAIR CONFORMATION
24.4 Identifying a Reducing Sugar
STEP 1 - IDENTIFY THE ______________
POSITION.
HO
HO
CH2OH
O
OH
STEP 2 - DETERMINE IF THE GROUP ATTACHED TO THE ANOMERIC POSITION IS
A _____________ GROUP OR ___________ GROUP.
- IF ___________ GROUP, THEN THE COMPOUND IS A REDUCING SUGAR
- IF ____________ GROUP, THEN THE COMPOUND IS NOT A REDUCING SUGAR.
OCH3
CHAPTER 24
641
24.5 Determining Whether a Disaccharide Is a Reducing Sugar
STEP 1 - IDENTIFY THE ______________ POSITIONS.
OH
CH2OH
O
HO
OH
O
HO
STEP 2 - DETERMINE IF THE GROUPS ATTACHED TO
THE ANOMERIC POSITIONS ARE HYDROXY GROUPS OR
ALKOXY GROUPS.
- IF ONE IS A ____________ GROUP, THEN THE
COMPOUND IS A REDUCING SUGAR.
- IF NEITHER ARE ____________ GROUPS, THEN THE
COMPOUND IS NOT A REDUCING SUGAR.
CH2OH
O
OH
OH
Review of Reactions
Identify the reagents necessary to achieve each of the following transformations. To
verify that your answers are correct, look in your textbook at the end of Chapter 24. The
answers appear in the section entitled Review of Reactions.
Hemiacetal Formation
H
H
1
C
2
HO
3
H
4
H
5
O
6
HOCH2
OH
H
H
OH
H
4
OH
HO
OH
H
OH
H
H
H
H
OH
H
OH
CH2OH
C
O
3
H
H
4
H
5
OH
OH
6
6
HOCH2
HOCH2
H
5
H
4
OH
OH
3
2
H
CH2OH
1
HO
H
H
OH
Chain Lengthening and Chain Shortening
H
HO
H
H
O
H
H
HO
OH
H
OH
H
CH2OH
OH
O
O
OH
CH2OH
H
OH
HO
2
H
O
H
O
3
CH2OH
2
OH
1
HO
6
1
HOCH2
5
C
O
H
OH
H
OH
OH
CH2OH
HO
+
HO
H
H
C
O
H
H
OH
OH
CH2OH
H
CH2OH
642
CHAPTER 24
Reactions of Monosaccharides
CH2OH
O
HO
HO
CH2OAc
OH
OH
O
AcO
AcO
OAc
OAc
CH3O
CH3O
HO
H
CH2OCH3
O
HO
OCH3
OCH3
HO
CH2OH
HO
HO
H
O
HO
OCH3
OH
CH2OH
H
OH
HO
C
O
OH
C
O
OH
H
H
OH
H
OH
HO
O
H
H
H
OH
H
OH
H
OH
H
OH
CH2OH
CH2OH
Solutions
24.1.
a) an aldohexose
d) an aldotetrose
b) an aldopentose
e) a ketohexose
c) a ketopentose
24.2. Both are hexoses so both have molecular formula (C6H12O6). Although they have
the same molecular formula, they have different constitution – one is an aldehyde and the
other is a ketone. Therefore, they are constitutional isomers.
24.3. All are D sugars except for (b), which is an L sugar.
a) 2S, 3S, 4R, 5R
b) 2R, 3S, 4S
c) 3R, 4R
d) 2S, 3R
e) 3S, 4S, 5R
Pay special attention to the following trend: The configuration of each chirality center is
R when the OH group is on the right side of the Fischer projection, and the configuration
is S when the OH group is on the left side.
24.4.
H
a)
C
O
H
C
O
H
OH
HO
H
H
OH
HO
H
H
OH
HO
H
H
OH
HO
H
CH2OH
b)
CH2OH
CHAPTER 24
643
24.5.
CH2OH
CH2OH
C O
C O
H
OH
HO
CH2OH
H
CH2OH
D
L
enantiomers
24.6.
H
H
O
C
C
O
H
H
OH
HO
H
HO
H
OH
HO
H
H
CH2OH
D
CH2OH
L
C
H
O
H
C
H
OH
OH
HO
CH2OH
O
H
CH2OH
D
L
enantiomers
enantiomers
24.7.
CH 2 OH
C O
H
OH
HO
H
HO
H
CH 2 OH
L-Fr uctose
24.8. D-fructose and D-glucose are constitutional isomers. Both have molecular formula
(C6H12O6). Although they have the same molecular formula, they have different
constitution – one is a ketone, and the other is an aldehyde.
CH2OH
C O
H
OH
HO
H
H
OH
CH2OH
D-Fructose
H
H
HO
H
H
C
O
OH
H
OH
OH
CH2OH
D-Glucose
644
CHAPTER 24
24.9.
O
O
O
OH
OH
O
OH
OH
a)
b)
c)
d)
24.10.
O
HO
H
24.11.
O
O
HO
OH
OH
HO
a)
b) The six-membered ring is expected to predominate because it has less ring strain than
a five-membered ring.
24.12.
6
6
HOCH2
OH
4
5
O
OH
OH
HOCH2
1
5
4
a)
O
1
2
1
OH
OH 3
c)
6
5
HOCH2
5
4
d)
OH
OH 3
OH
O
OH
4
1
2
24.13. β-D-galactopyranose
e)
OH
6
HOCH2
O
5
OH
1
OH
OH 3
OH
2
OH
HOCH2
6
O
4
OH
OH 3
b)
OH
5
OH
2
3
HOCH2
6
4
OH
f)
1
OH
OH 3
2
O
2
OH
OH
645
CHAPTER 24
24.14.
H
HO
3
HO
6
5
H
H
OH
4
HO
H
O
B
H
6
HOCH2
6
O
CH2OH
H
2
5
H
1
OH
3
H
A
OH
5
H
H
O
H
4
H
HOCH2
1C
2
OH
O
H
OH
4
HO
2
H
α-D-Mannopyranose
1
OH
3
H
OH
H
H
β-D-Mannopyranose
24.15.
H
HO
HO
1C
2
3
6
H
OH
4
H
5
H
OH
A
H
H
HO 4
HOCH2
H
O
H
5
O H
B
6
HOCH2
6
O
CH2 OH
H
1
OH
H
H
2
O
H
OH
4
OH
3
5
OH
2
H
α -D-Talopyr anose
1
OH
3
H
OH
H
H
β -D-Talopy r anose
24.16.
OH
CH2OH
CH2OH
O
HO
a)
HO
HO
OH
OH
HO
HO
H
OH
b)
H
CH2OH
O
c)
OH
24.17.
H
CH2OH
O
HO
OH
OH
OH
H
C
O
H
OH
H
OH
H
OH
H
OH
CH2OH
D-Allose
O
OH
OH
H
646
CHAPTER 24
24.18.
HO
OH
O
HO
HO
OH
OH
ring flip
O
OH
OH
OH
more stable
OH
less stable
24.19.
OH
OH
O
O
O
OH
OH
a)
OH
O
OH
b)
OH
OH
c)
OH
d)
OH
OH
24.20.
H
H
HO
C
O
OH
H
CH2OH
H
H
O
H
H
H
HO
C
O
H
OH
H
OH
OH
O
H
CH2OH
OH
L-THREOSE
H
OH
O
H
OH
O
OH
OH
CHAPTER 24
24.21.
CH2OH
C
HO
CH2OH
H
O
H
H
C
O
HO
H
O
H
OH
O
H
OH
H
OH
H
OH
H
OH
CH2OH
CH2OH H
H
OH
CH2OH
CH2OH
OH
D-Fructose
H
O
CH2OH
O
OH
H
OH
CH2OH
OH
24.22.
CH2OH
C
O
H
HO
H
OH
H
OH
CH2OH
D-Fructose
24.23.
a)
HO
AcO
CH2OH
O
excess Ac2O
HO
CH2OAc
O
AcO
py
OH
OAc
OAc
OH
b)
CH2OH
O
HO
HO
excess Ac2O
py
AcO
AcO
OAc
OAc
OH
OH
HO
AcO
CH2OH
O
HO
c)
excess Ac2O
OH
OH
CH2OAc
O
py
CH2OAc
O
AcO
OAc
OAc
647
648
CHAPTER 24
24.24.
a)
HO
CH3O
CH2OH
O
excess CH3I
HO
CH2OCH3
O
CH3O
Ag2O
OH
CH3O OCH
3
OH
b)
CH2OH
O
HO
HO
excess CH3I
CH3O
CH3O
Ag2O
OH
CH2OCH3
O
CH3O OCH
3
OH
c)
HO
CH3O
CH2OH
O
excess CH3I
HO
OH
CH3O
Ag2O
OH
CH2OCH3
O
OCH3
OCH3
24.25.
HO CH OH
2
HO CH OH
2
O
H
HO
HO CH OH
2
- H2 O
O
Cl
O
HO
HO
OH
OH
OH
H
O
OH
H
HO
CH2OH
O
HO
OH
--------------------------------------------------------------------------------------------------------HO
HO
CH2OH
HO
CH2OH
EtOH
O
HO
O
H
HO
OH
HO
OEt
OH
Et
H
CH2OH
O
Et
O
OH
H
H
O
H
--------------------------------------------------------------------------------------------------------HO CH OH
2
HO CH OH
2
EtOH
O
HO
H
O
HO
OH
H
H
HO
Et
O
Et
HO CH OH
2
O
HO
H
OH
O
OEt
H
649
CHAPTER 24
24.26.
CH2OH
CH2OH
H
O
HO
HO
A
H
CH2OH
O
HO
HO
H
OH
OH
HO
OCH3
O
HO
HO
O
H3C
H
H
CH3OH
CH2OH
CH2OH
O
HO
HO
A
OCH3
O
HO
HO
OH
H
24.27.
C
O
H
H
H
HO
H
O
OH
H
H
H
OH
HO
H
OH
H
OH
HO
H
OH
OH
H
HO
H
CH2OH
D-Mannose
a)
C
b)
C
O
OH
H
H
OH
CH2OH
CH2OH
D-Allose
c)
D-Galactose
24.28.
H
C
HO
O
CH2OH
H
HO
H
OH
NaBH4
H
OH
H2 O
H
OH
CH2OH
D-Altose
H
C
O
HO
H
HO
H
HO
H
H
OH
CH2OH
D-Talose
NaBH4
H 2O
CH2OH
H
HO
H
H
OH
HO
H
H
OH
HO
H
H
OH
CH2OH
CH3
OH
H
H
H
O
Rotate
180
H
OH
CH2OH
650
CHAPTER 24
24.29.
H
C
H
O
CH2OH
OH
H
OH
NaBH4
H
OH
H2 O
H
OH
CH2OH
H
OH
HO
H
H
OH
HO
H
H
OH
HO
H
H
OH
HO
H
CH2OH
CH2OH
Rotate
180
CH2OH
D-Allose
H
C
O
HO
H
HO
H
HO
H
HO
H
NaBH4
H 2O
CH2OH
L-Allose
24.30. The following alditols are meso compounds, and are therefore optically inactive:
H
C
H
O
CH2OH
OH
H
OH
NaBH4
H
OH
H2 O
H
OH
H
OH
H
OH
H
OH
H
OH
CH2OH
CH2OH
(meso)
D-Allose
H
C
H
O
CH2OH
OH
HO
HO
H
H
H
NaBH4
HO
H
H2 O
HO
OH
H
CH2OH
D-Galactose
OH
H
H
OH
CH2OH
(meso)
24.31.
a) No (an acetal)
b) Yes
c) Yes
651
CHAPTER 24
24.32.
HO
O
C
H
HO
OH
H
O
HO
OH
O
C
H
HO
OH
H
OH
H
HO
H
HO
H
HO
H
H
OH
H
OH
OH
H
OH
H
OH
H
CH2OH
CH2OH
D-Galactonic acid
b)
HO
O
HO
OH
H
C
HO
H
a)
C
CH2OH
D-Galactonic acid
c)
H
CH2OH
D-Gluconic acid
D-Gluconic acid
d)
24.33. This compound will not be a reducing sugar because the anomeric position is an
acetal group.
CH3O
CH3O
CH2OCH3
O
OCH3
OCH3
β-D-Glucopyranose pentamethyl ether
24.34.
H
C
H
H
O
OH
Fischer-Kiliani
O
C
H
O
C
H
OH
HO
H
OH
H
OH
OH
H
OH
H
OH
H
OH
H
CH2OH
H
+
OH
H
H
OH
CH2OH
CH2OH
D-Ribose
D-Allose
a)
H
C
H
H
O
OH
HO
H
Fischer-Kiliani
O
H
H
OH
HO
H
OH
H
OH
HO
CH2OH
H
H
C
D-Altose
H
+
OH
C
H
OH
HO
H
H
CH2OH
O
OH
CH2OH
D-Xylose
D-Gulose
b)
H
HO
HO
H
C
H
O
H
H
OH
CH2OH
H
Fischer-Kiliani
C
H
O
OH
HO
H
HO
H
H
D-Idose
OH
CH2OH
+
C
O
HO
H
HO
H
HO
H
H
OH
CH2OH
D-Ly xose
c)
D-Galactose
D-T alose
652
CHAPTER 24
24.35.
H
C
H
O
C
H
H
OH
1) HCN
H
OH
2) H2 , Pd / BaSO4 , H2O
CH2OH
O
H
OH
H
OH
H
OH
HO
+
O
H
H
OH
H
OH
CH2OH
D-Erythrose
C
CH2OH
D-Ribose
D-Arabinose
24.36.
H
C
O
H
OH
H
OH
H
OH
H
OH
H
C
HO
+
CH2OH
O
H
H
H
OH
H
H
Wohl Degradation
H
OH
OH
H
OH
OH
H
OH
CH2OH
D-Allose
O
C
CH2OH
D-Ribose
D-Altose
24.37.
H
C
O
H
OH
H
OH
H
OH
H
1) NH2OH
2) Ac2O
3) NaOMe
CH2OH
C
O
H
OH
H
OH
CH2OH
D-Ribose
D-Erythrose
24.38.
H
H
HO
C
O
H
H
OH
H
H
OH
H
OH
CH2OH
D-Glucose
Wohl
Degradation
HO
C
O
H
H
Fischer-
H
OH
Kiliani
H
OH
CH2OH
D-Arabinose
24.39.
a) Yes, one of the anomeric positions bears an OH group.
b) No, both anomeric positions bear acetal groups.
c) No, both anomeric positions bear acetal groups.
HO
C
O
H
OH
H
H
OH
H
OH
+
C
O
HO
H
HO
H
H
OH
H
OH
CH2OH
CH2OH
D-Glucose
D-Mannose
653
CHAPTER 24
24.40.
CH2OH
CH2OH
O
HO
HO
CH2OH
O
O
OH
O
HO
HO
NaBH4
CH2OH
OH
HO
OH
HO
MeOH
OH
OH
O
OH
OH
24.41.
a)
CH2OH
CH2OH
O
HO
HO
CH2OH
OH
HO
O
HO
HO
NaBH4
O
O
OH
H2O
OH
CH2OH
OH
O
HO
OH
OH
OH
CH2OH
CH2OH
O
HO
HO
CH2OH
O
OH
Br2
O
HO
OH
CH2OH
OH
O
OH
H2O
OH
b)
O
HO
HO
HO
OH
OH
O
c)
CH2OH
O
HO
HO
CH2OH
OH
CH3OH
O
O
HO
OH
HCl
CH2OH
CH2OH
O
HO
HO
OCH3
+
O
HO
HO
OH
OH
OH
OCH3
d)
CH2OH
HO
HO
CH2OAc
O
CH2OH
O
OH
Ac2O
O
HO
OH
AcO
AcO
O
OAc
py
CH2OAc
O
OH
24.42.
a) a D-aldotetrose
d) a D-aldohexose
O
AcO
OAc
OAc
b) an L-aldopentose
e) a D-ketopentose
c) a D-aldopentose
24.43.
a) D-glyceraldehyde b) L-glyceraldehyde c) D-glyceraldehyde d) L-glyceraldehyde
24.44.
a) D-Glucose
b) D-Mannose
c) D- Galactose
d) L-Glucose
654
CHAPTER 24
24.45.
a) D-Ribose
b) D-Arabinose
H
O
C
HO
H
HO
H
HO
H
CH2OH
c) L-Ribose
d) Same compound
e) Diastereomers
24.46.
O
O
O
OH
OH
OH
b)
a)
c)
24.47.
O
HO
H
24.48.
H 1 O
C
H
H
H
2
H
OH
3
OH
4
OH
5
H
H
4
5
OH
O
H
4
HO
OH
CH2OH
H
2
3
3
HO
OH
2
OH
OH
OH
1
3
HO
OH
2
OH
α pyranose ring
D-ribose
O
4
+
1
H
1
5
5
O
OH
β pyranose ring
b)
H 1 O
C
H
H
H
2
3
4
5
OH
HOCH2
OH
OH
5
CH2OH
H
H
H
O
1
H
2
3
OH
5
CH2OH
O
OH
4
5
CH2OH
OH
4
+
3
OH
2
OH
OH
α furanose ring
OH
O
1
4
1
3
OH
2
OH
β furanose ring
D-ribose
24.49.
a) epimers
b) diastereomers
c) enantiomers
d) identical compounds
655
CHAPTER 24
24.50.
H
C
H
HO
H
H
O
OH
H
OH
OH
CH2OH
D-Glucose
24.51.
H
H
H
O
C
H
R
H
OH
R
H
H
OH
HO
CH2OH
a)
C
R
R
S
O
H
OH
R
H
OH
HO
S
H
R
H
CH2OH
b)
C
O
H
H
H
H
OH
CH2OH
c)
HO
OH
C
R
S
R
R
O
C O
H
OH
OH
CH2OH
d)
CH2OH
OH
HO
S
H
H
R
OH
CH2OH
e)
24.52.
H
H
HO
H
H
a)
C
H
O
C
O
H
OH
H
OH
OH
CH2OH
H
OH
HO
HO
HO
H
H
H
HO
H
H
OH
CH2OH
D-Glucose
b)
OH
HO
D-Galactose
c)
O
H
H
H
OH
OH
CH2OH
H
H
H
H
C
D-Mannose
d)
C
O
OH
OH
OH
OH
CH2OH
D-Allose
24.53.
6
HOCH2
5
O
H
H
a)
HO
4
3
H
OH
HOCH2
2
1
O
HO
b)
O
OH
OH
24.55.
a) α-D-allopyranose
b) β-D-galactopyranose
c) methyl β-D-glucopyranoside
HOCH2
O
OH
CH2OH
HOCH2
OH
OH
OH
24.54.
HO
HOCH2
O
OH
c)
OH
OH
OH
d)
HO
OH
OH
656
CHAPTER 24
24.56.
H
H
H
H
H
a)
O
C
H
OH
OH
H
OH
HO
OH
OH
CH2 OH
D-Allose
H
O
C
H
HO
H
H
H
HO
H
H
OH
CH2OH
b)
D-Galactose
C
O
OH
H
OH
OH
CH2OH
D-Glucose
c)
24.57.
CH3O
CH2OCH3
O
OCH3
OCH3
HO
b)
CH2OH
O
OCH3
OH
c)
OAc
OAc
OCH3
a)
CH2OAc
O
AcO
OH
+
OAc
CH2 OH
O
HO
OH
OH
OCH3
24.58. The product is a meso compound
HO
C
H
meso
compound
OH
HO
H
HO
H
H
HO
O
OH
C
O
24.59.
H
H
H
H
H
C
O
OH
OH
OH
OH
CH2OH
D-Allose
HO
HNO3, H2O
heat
C
H
H
H
H
HO
O
OH
OH
OH
OH
C
O
optically inactive
meso
compound
CHAPTER 24
24.60.
axial
equatorial
OH
O
HO
HO
equatorial
OH
OH
axial
axial
24.61.
HO
CH3 O
CH2OH
O
excess CH3 I
HO
Ag2O
OH
CH3O
CH2 OCH3
O
+
CH3 O
CH2 OCH3
O
CH3O
OCH3
OCH3
CH3 O OCH
3
OH
H3 O+
CH3 O
CH3O
CH2 OCH3
O
+
CH3 O
CH2 OCH3
O
CH3O
OH
OCH3
CH3 O OH
24.62.
a) diastereomers
b) same compound
24.63.
CH2OH
CH2OH
CH2OH
CH2OH
C
C
C
C
O
H
OH
HO
H
OH
H
OH
H
H
CH2OH
O
H
H
OH
HO
OH
H
CH2OH
O
O
OH
HO
H
H
HO
H
OH
CH2OH
H
OH
CH2OH
24.64.
H
C
O
H
C
O
H
OH
HO
H
OH
H
OH
H
OH
H
OH
H
OH
H
OH
CH2OH
D-Allose
Wohl
degradation
Wohl
degradation
H
C
O
H
OH
H
OH
H
OH
CH2OH
D-Ribose
H
CH2OH
D-Altose
657
658
CHAPTER 24
24.65.
H
H
C
HO
O
H
Kiliani-Fischer
H
HO
C
O
H
HO
H
H
HO
H
OH
H
OH
H
OH
H
OH
D-Arabinose
O
OH
H
CH2OH
C
+
H
OH
H
OH
CH2OH
CH2OH
D-Glucose
D-Mannose
24.66.
H
H
C
CN
H
OH
H
OH
O
HCN
OH
CH 2OH
CN
HO
H
H
OH
+
CH2 OH
D-Gly cer ald ehy de
CH2 OH
Diastereomers
24.67.
CH2OH
H
HO
OH
H
H
OH
H
OH
CH2OH
a)
H
HO
HO
H
HO
O
CH2OH
H
H
OH
HO
NaBH4
H2O
H
CH2OH
b)
HO
H
HO
CH2OH
H
H
H
HO
OH
H
OH
H
OH
H
H
OH
CH2OH
CH2OH
L-Gulose
24.68. D-Allose and D-Galactose
24.69.
a) This compound will not be a reducing sugar because the anomeric position is an acetal
group.
b) This compound will be a reducing sugar because the anomeric position bears an OH
group.
CHAPTER 24
24.70.
a) CH3OH, HCl
b) CH3OH, HCl
c) HNO3, H2O, heat
d) excess CH3I, Ag2O followed by H3O+
24.71.
a) α-D-glucopyranose and β-D-glucopyranose
b) α-D-galactopyranose and β-D-galactopyranose
24.72.
a)
b)
c)
d)
D-Arabinose
D-Ribose and D-xylose
D-xylose
D-xylose
24.73.
HOCH2
O
OH
OH
HO
O
OH
OH
OH
O
HOCH2
24.74.
H
H
HO
H
C
O
OH
H
OH
CH2OH
CH2OH
H
OH
HO
H
H
OH
CH2OH
NaBH4
H2O
D-Xylose
D-Xylitol
24.75.
CH2OH
HO
HO
O
1
OH
O
6
CH2
HO
O
HO
Isomaltose
(a 1 6-α-glycoside)
OH
OH
659
660
CHAPTER 24
24.76.
a) No, it is not a reducing sugar because the anomeric position has an acetal
group.
OH
OH
O
HO
HO
O
HO
HO
OH
OH
H3 O+
OH
O
+
OH
OH
HO
HO
salicin
OH
OH
b)
c) Salicin is a β-glycoside.
OH
OH
OAc
OH
O
HO
HO
OH
O
Ac2O
O
AcO
AcO
py
OH
OAc
O
O
OAc
salicin
d)
e) No. In the absence of acid catalysis, the acetal group is not readily
hydrolyzed.
24.77.
OH
HO
HO
OH
O
H
O
HO
HO
Cl
OH
OH
H
- H2O
O
OH
OH
O
HO
HO
H
OH
OH
OH
HO
HO
OH
O
HO
HO
Cl
O
OH
CH2OH
CH2OH
O
+
OH
H
N
an α -N-Glycoside
HO
HO
O
H
N
OH
a β -N-Gly coside
H
O
OH
24.78.
HO
HO
O
661
CHAPTER 24
24.79.
NH2
N
HO
N
O
N
N
HO
N
N
O
OH
a)
N
N
H
NH2
O
DEOXYADENOSINE
GUANOSINE
b)
OH
OH
24.80.
H
HO
H
H
C
O
H
C
H
C
O
H
H
HO
H
H
OH
H
OH
HO
H
H
OH
HO
OH
H
OH
H
OH
H
CH2OH
CH2OH
CH2OH
C
O
OH
H
OH
CH2OH
NaBH4
NaBH4
NaBH4
NaBH4
H2O
H2O
H2O
H2O
CH2OH
HO
O
CH2OH
CH2OH
CH2OH
H
HO
H
H
OH
H
H
OH
HO
H
H
OH
HO
H
OH
H
OH
H
OH
H
CH2OH
(optically active)
CH2OH
CH2OH
(optically active)
(optically inactive)
OH
H
OH
CH2OH
(optically inactive)
24.81.
HO
H
HO
O
OH
HOCH2
O
H
H
OH
H
OH
OH
O
OH
CH2OH
OH
a)
b)
c) Yes. The compound has chirality centers, and it is not a meso compound. Therefore,
it will be optically active.
d) The gluconic acid is a carboxylic acid and its IR spectrum is expected to have a broad
signal between 2500 and 3600 cm-1. The IR spectrum of the lactone will not have this
broad signal.
662
CHAPTER 24
24.82. In order for the CH2OH group to occupy an equatorial position, all of the OH
groups on the ring must occupy axial positions. The combined steric hindrance of
all the OH groups is more than the steric hindrance associated with one CH2OH
group. Therefore, the equilibrium will favor the form in which the CH2OH group
occupies an axial position. The structure of L-idose is:
H
O
H
OH
HO
H
HO
O
HO
H
HO
OH
OH
HOCH2
H
OH
CH2OH
L-Idose
24.83.
H
O
H
OH
H
OH
H
OH
H
OH
CH2OH
OH
OEt
EtI
O
HO
OH
O
EtO
Ag2O
OEt
OH
OH
OEt
OEt
β-pyranose form
D-Allose
(Compound A)
24.84. Glucose can adopt a chair conformation in which all of the substituents on the
ring occupy equatorial positions. Therefore, D-glucose can achieve a lower
energy conformation than any of the other D-aldohexoses.
CHAPTER 24
663
24.85.
H
O
C
H
O
H
OH
HO
OH
H
H
H
OH
OH
HO
OH
H
OH
H
CH2OH
H
H
O
H
CH2OH
OH
H
HO
OH
H
OH
H
C
taut
H
CH2OH
O
HO
H
OH
H
OH
H
OH
OH
CH2OH
CH2OH
D-glucose
OH
CH2OH
CH2OH
H
H
OH
O
H
C
OH
OH
OH
O
O
H
OH
H
OH
CH2OH
H
CH2OH
OH
taut
CH2OH
OH
HO
H
O
OH
O
H
H
OH
H
H
OH
H
CH2OH
CH2OH
CH2OH
CH2OH
OH
OH
CH2OH
H
CH2OH
H
H
OH
OH
HO
H
taut
OH
HO
C
OH
H
CH2OH
HO
OH
H
H
H
O
H
OH
O
H
H
H
C
O
HO
CH2OH
CH2OH
OH
HO
OH
O
OH
CH2OH
H
CH2OH
OH
H
O
HO
HO
OH
HO
H
O
O
H
taut
H
H
H
O
H
H
OH
O
OH
OH
HO
OH
CH2OH
CH2OH
H
CH2OH
H
OH
H
CH2OH
HO
CH2OH
OH
HO
H
HO
CH2OH
H
OH
C
H
HO
CH2OH
CH2OH
CH2OH
C
OH
taut
H
OH
H
O
OH
H
OH
OH
O
H
OH
H
H
O
H
H
OH
HO
H
OH
taut
H
HO
H
HO
H
HO
H
HO
H
HO
HO
H
HO
H
HO
H
HO
H
HO
CH2OH
CH2OH
CH2OH
CH2OH
C
O
H
OH
H
H
CH2OH
L-glucose
664
CHAPTER 24
24.86. Compound X is a D-aldohexose that can adopt a β-pyranose form with only one
axial substituent. Recall that D-glucose has all substituents in equatorial positions, so
compound X must be epimeric with D-glucose either at C2 (D-mannose), C3 (D-allose),
or C4 (D-galactose).
Compound X undergoes a Wohl degradation to produce an aldopentose, which is
converted into an optically active alditol when treated with sodium borohydride.
Therefore, compound X cannot be D-allose, because a Wohl degradation of D-allose
followed by reduction produces an optically inactive alditol.
We conclude that compound X must be either D-mannose or D-galactose.
The identity of compound X can be determined by treating compound X with sodium
borohohydride. Reduction of D-mannose should give an optically active alditol, while
reduction of D-galactose gives an optically inactive alditol.
24.87. Compound A is a D-aldopentose. Therefore, there are four possible structures to
consider (Figure 24.4).
When treated with sodium borohydride, compound A is converted into an alditol that
exhibits three signals in its 13C NMR spectrum. Therefore, compound A must be Dribose or D-xylose both of which are reduced to give symmetrical alditols (thus, three
signals for five carbon atoms).
When compound A undergoes a Kiliani-Fischer synthesis, both products can be treated
with nitric acid to give optically active aldaric acids. Therefore, compound A cannot be
D-ribose, because when D-ribose undergoes a Kiliani-Fischer synthesis, one of the
products is D-allose, which is oxidized to give an optically inactive aldaric acid. We
conclude that the structure of compound A must be D-xylose.
H
H
HO
H
a)
C
O
OH
H
OH
CH2OH
D-Xylose
b) Compound D is expected have six signals in its 13C NMR spectrum, while compound
E is expected to have only three signals in its 13C NMR spectrum.
HO
C
H
H
HO
H
HO
C
O
HO
OH
OH
H
OH
HO
H
HO
H
O
HO
Compound D
C
O
H
OH
H
OH
C
O
Compound E