Monosaccharides

1. MONOSACCHARIDES
Simple sugars.
Cannot be further hydrolyzed into simple
carbohydrates
 catagorized by the number of carbon
(typically 3-8) and whether an aldehyde or
ketone.

2. Monosaccharides
Aldoses (e.g., glucose) have an
aldehyde group at one end.
Ketoses (e.g., fructose)
have a keto group,
usually at C2.

5. MONOSACCHARIDE STRUCTURES
FISHER PROJECTIONS
HAWORTH PERSPECTIVE FORMULAS

6. The asymmetric(chiral) carbon atom
and D and L monosaccharides
Any carbon atom which is connected to four
different groups will be chiral, and will have two
nonsuperimposable mirror images; it is a chiral
carbon or a center of chirality.

10. •When a molecule has more than one chiral
carbon,
each carbon can possibly be arranged in either the
right-hand or left-hand form, thus if there are n
chiral carbons, there are 2n possible
stereoisomers.
Maximum number of possible stereoisomers = 2n

11. Isomerism in monosaccharides
Compounds that possess the same chemical
formula are called isomers.
Glucose,fructose,mannose and galactose all
have the same formula,i.e C6H12O6 and
therefore isomers of each other.

12. 1.STERIOISOMERISM
General term,means two or more
monosaccharides having the same structure
but differing from each other in that the
configuration,i.e the arrangement of their
atoms in space differ from each other.

14. 2.ENANTIOMERS.
Pair of stereoisomerism that are mirror images
of each other in regard to asymetric carbon
atoms present in their molecules.
For example glucose occurs as D and L glucose
isomers.

17. 3.OPTICAL ISOMERISM
The enantiomeric monosaccharides by virtue of their
content of asymmetric carbon atom can rotate the
plane-polarized light either to right or left.
The monosaccharides that rotate this light to right are
called dextrorotatory(+type)
Those rotating this light to left are called levorotatory(-
type).
Glucose is dextrorotatory(+),while fructose is
levorotatory(-)

18. 4.EPIMERS
Monosaccharides(isomers) which differ in
configuration around one specific carbon atom
other than the carbon atom of carbonyl group.

19. Glucose Galactose

21. 5.ANOMERS
Isomers that differ in configuration around the
anomeric carbon i.e the carbon atom of the
carbonyl group which is carbon no.1 in aldosed
and carbon no.2 in ketoses.

22. These representations of the cyclic sugars are
called Haworth projections.

H
O
OH
H
OHH
OH
CH
2OH
H
OH
H H
O
OH
H
OHH
OH
CH
2OH
H
H
OH
a-D-glucose b-D-glucose
23
4
5
6
1 1
6
5
4
3 2
H
CHO
COH
CHHO
COHH
COHH
CH
2OH
1
5
2
3
4
6
D-glucose
(linear form)

23. Cyclization of glucose produces a new asymmetric
center at C1. The 2 stereoisomers are called anomers,
a & b.
a (OH below the ring)
b (OH above the ring).

H
O
OH
H
OHH
OH
CH
2OH
H
a-D-glucose
OH
H H
O
OH
H
OHH
OH
CH
2OH
H
H
OH
b-D-glucose
23
4
5
6
1 1
6
5
4
3 2

25. 6.PYRANOSE-FURANOSE ISOMERISM
The ring structures of monosaccharides may
be similar to either pyran or furan and
accordingly the monosaccharide is said to
occur in pyranose or furanose form.

27. RECEMIC MIXTURE
Equal amounts of dextro- and levorotatory
isomers in solution results no net rotation of
plane of polarized light.Such a mixture is called
racemic mixture.
MESOCOMPOUNDS
Donot rotate the light inspite of asymmetric
carbon due to internal compensation.

28. MUTAROTATION
Process by which anomers are interconverted.