Carbohydrates

1. σακχαρων
Greek “sakcharon” = sugar

2. Carbohydrates – polyhydroxyaldehydes or polyhydroxy-
ketones of formula (CH
2
O)
n
, or compounds that can be
hydrolyzed to them. (aka sugars or saccharides)
Monosaccharides – carbohydrates that cannot be hydrolyzed
to simpler carbohydrates; eg. Glucose or fructose.
Disaccharides – carbohydrates that can be hydrolyzed into
two monosaccharide units; eg. Sucrose, which is hydrolyzed
into glucose and fructose.
Oligosaccharides – carbohydrates that can be hydrolyzed into
a few monosaccharide units.
Polysaccharides – carbohydrates that are are polymeric
sugars; eg Starch or cellulose.

3. Aldose – polyhydroxyaldehyde, eg glucose
Ketose – polyhydroxyketone, eg fructose
Triose, tetrose, pentose, hexose, etc. – carbohydrates that
contain three, four, five, six, etc. carbons per molecule
(usually five or six); eg. Aldohexose, ketopentose, etc.

4. Reducing sugar – a carbohydrate that is oxidized by Tollen’s,
Fehling’s or Benedict’s solution.
Tollen’s: Ag
+
 Ag (silver mirror)
Fehling’s or Benedict’s: Cu
3+
(blue)  Cu
2+
(red ppt)
These are reactions of aldehydes and alpha-hydroxyketones.
All monosaccharides (both aldoses and ketoses) and most
*

disaccharides are reducing sugars.
*
Sucrose (table sugar), a disaccharide, is not a reducing sugar.

5. Glucose (a monosaccharide)
Plants:
photosynthesis
chlorophyll
6 CO
2
+ 6 H
2
O C
6
H
12
O
6
+ 6 O
2

sunlight (+)-glucose
(+)-glucose starch or cellulose
respiration
C
6
H
12
O
6
+ 6 O
2
6 CO
2
+ 6 H
2
O + energy

6. Animals
plant starch (+)-glucose
(+)-glucose glycogen
glycogen (+)-glucose
(+)-glucose fats or aminoacids
respiration
(+)-glucose + 6 O
2
6 CO
2
+ 6 H
2
O + energy

7. OH
CHO
H
CH
2OH
H
CHO
HO
CH
2OH
D-(+)-glyceraldehyde L-(-)-glyceraldehyde
glyceraldehyde
an aldotriose
CH
2CHCHO
OHOH
*
D & L are used to relate configuration of the chiral center
most removed from the reducing group ( C=O ). If the -OH
is on the right in the Fischer projection, then it is D, if the -OH
is on the left, then it is L

8. CHO
H OH
CH
2OH
H OH
aldotetroses
CH
2CHCHCHO
OHOHOH
**
CHO
HO H
CH
2OH
HO H
CHO
H OH
CH
2OH
HO H
CHO
HO H
CH
2OH
H OH
D-erythrose L-erythrose
L-threose D-threose

9. (+)-glucose? An aldohexose
Emil Fischer (1902)
Four chiral centers, 2
4
= 16 stereoisomers
CHO
CH
2OH
OH?
CH
2CHCHCHCHCHO
OHOHOHOHOH
****

10. CHO
OHH
OHH
OHH
OHH
CH
2OH
CHO
HHO
OHH
OHH
OHH
CH
2OH
CHO
OHH
HHO
OHH
OHH
CH
2OH
CHO
HHO
HHO
OHH
OHH
CH
2OH
CHO
OHH
OHH
HHO
OHH
CH
2OH
CHO
HHO
OHH
HHO
OHH
CH
2OH
CHO
OHH
HHO
HHO
OHH
CH
2OH
CHO
HHO
HHO
HHO
OHH
CH
2OH
CHO
HO H
HO H
HO H
HO H
CH
2OH
CHO
H OH
HO H
HO H
HO H
CH
2OH
CHO
HO H
H OH
HO H
HO H
CH
2OH
CHO
H OH
H OH
HO H
HO H
CH
2OH
CHO
HO H
HO H
H OH
HO H
CH
2OH
CHO
H OH
HO H
H OH
HO H
CH
2OH
CHO
HO H
H OH
H OH
HO H
CH
2OH
CHO
H OH
H OH
H OH
HO H
CH
2OH

11. Ruff degradation – a series of reactions that removes the
reducing carbon ( C=O ) from a sugar and decreases the
number of chiral centers by one; used to relate configuration.
CHO
H OH
CH
2OH
H OH
CO
2H
H OH
CH
2OH
H OH
Br
2
H
2O
CO
2
H OH
CH
2OH
H OH
Ca
2+
H
2O
2
Fe
3
+
CHO
CH
2OH
H OH
D-(+)-glyceraldehyde

12. Kiliani-Fischer synthesis. A series of reactions that extends the
carbon chain in a carbohydrate by one carbon and one chiral
center.
CHO
H OH
CH
2OH
HCN
C
H OH
CH
2OH
H OH
C
HO H
CH
2OH
H OH
+
N N
H
+
,H
2O
COOH
H OH
CH
2OH
H OH
COOH
HO H
CH
2OH
H OH
diastereomers
separable
C
H OH
H
2C
H OH
O
O
lactone
Na(Hg)
CHO
H OH
CH
2OH
H OH
-H
2O

13. Epimers – stereoisomers that differ only in configuration about
one chiral center.
CHO
OHH
HHO
OHH
OHH
CH
2OH
D-glucose
CHO
HHO
HHO
OHH
OHH
CH
2OH
D-mannose
epimers

14. CHO
OHH
HHO
OHH
OHH
CH
2OH
(+)-glucose
Exists only in solution. There are two
solids:
α-glucose m 146
o
[α] = +112.2
β-glucose m 150
o
[α] = +17.5
In water each mutarotates to an
equilibrium with [α] = +52.7
(63.6% β / 36.4% α)

15. CHO
OHH
HHO
OHH
OHH
CH
2OH
O
H
HO
H
HO
H
OH
OHH
H
OH
O
H
HO
H
HO
H
H
OHH
OH
OH
alpha-(+)-glucose
beta-(+)-glucose
O
H
OH
OH
H
H
OHH
OH
CH
2OH
O
H
OH
H
OH
H
OHH
OH
CH
2OH

16. R
C
H
O
+ R'OH RCH
OH
OR'
RCH
OR'
OR'
hemiacetal
geminal
ether/alcohol
reducing!
acetal
geminal
diether
non-reducing!
Addition of alcohols to aldehydes/ketones:

17. CHO
OHH
HHO
OHH
OHH
CH
2OH
O
H
HO
H
HO
H
OH
OHH
H
OH
O
H
HO
H
HO
H
H
OHH
OH
OH
nucleophilic addition of -OH on carbon 5 to the aldehyde functional group
CHO
OHH
HHO
OHH
OHH
CH
2OH
CH
OHH
HHO
OHH
HHOH
2C
OH
O
H
HO
H
HO
H
OH
OHH
H
OH
O
O
H
HO
H
HO
H
H
OHH
OH
OH
a
b
rotate C-5 OH to rear

18. O
H
HO
H
HO
H
H
OHH
OH
OH
O
H
HO
H
HO
H
OH
OHH
H
OH
hemiacetal
4H-Pyran
O
D-glucopyranoses
alpha beta

19. OH
H
H
HOH
HOH
O
H
HO
HO
H
OH
H
HOH
HOH
O
H
HO
HO
O
furan
alpha furanose form beta furanose form
D-glucofuranoses

20. O
H
HO
H
HO
H
H
OHH
OH
OH
O
H
HO
H
HO
H
OH
OHH
H
OH
alpha beta
anomers - epimers at C-1
chair conformations - alpha has one group axial
beta has all groups equatorial
mutarotation in solution to 63.6% beta/36.4% alpha

21. CH
2OH
O
HHO
OHH
OHH
CH
2OH
D-fructose
CH
2OH
OH
H
CH
2OH
OH H
H OH
O
beta-D-fructofuranose
OH
CH
2OH
H
CH
2OH
OH H
H OH
O
alpha-D-fructofuranose

22. O
H
HO
H
HO
H
H
OHH
OH
OH
CH
3OH
HCl
O
H
HO
H
HO
H
H
OHH
OCH
3
OH
acetal
(glucoside - glucose acetal)
non-reducing, does not muta-
rotate
methyl beta-D-glucoside

23. Disaccharides:
(+)-maltose “malt sugar”
two glucose units (alpha)
(+)-cellobiose
two glucose units (beta)
(+)-lactose “milk sugar”
galactose & glucose
(+)-sucrose “table sugar”
glucose & fructose

24. (+)-maltose
O
H
H
HO
H
H
OHH
OH
OH
O
H
HO
H
HO
H
OHH
H
OH
O
two glucose units
alpha C-1 to C-4
reducing sugar
O
H
HO
H
HO
H
H
OHH
OH
O
H
O
H
HO
H
H
OHH
OH
OH
(+)-cellobiose
two glucose units
beta C-1 to C-4
reducing sugar

25. O
H
HO
H
HO
H
OHH
H
OH
glucose alpha C-1
to beta C1 fructose
O
HO
H
H
HO
H
H
OHH
OH
O
H
O
H
HO
H
H
OHH
OH
OH
galactose beta C-1
to C-4 glucose
reducing sugar(+)-lactose
O
O
C
H
2
O
H
CH
2OH
H
H
OH
HO
H
(+)-sucrose
acetal
non-reducing

26. Polysaccharides
starch
cellulose
Starch 20% amylose (water soluble)
80% amylopectin (water insoluble)
amylose + H
2
O  (+)-maltose
(+)-maltose + H
2
O  (+)-glucose
starch is a poly glucose (alpha-glucoside to C-4)
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O

27. O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
CH
2
O
Amylopectin + H
2
O  (+)-maltose
(+)-maltose + H
2
O  (+)-glucose
Also a polyglucose, but branched every 20-25 units:

28. Cellulose is a polyglucose with a beta-linkage:
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O