general introduction and reactions along with detailed information about various classes

1. Carbohydrates

2. Carbohydrates
• Hydrates of carbon
•General formula, Cx(H2O)y
•Broadly defined as polyhydroxy aldehydes or
ketones and their derivatives or as substances
that yield one of these compounds on hydrolysis.

3. CLASSIFICATION
• Monosaccharide
• Oligosaccharide
• Polysaccharide

4. Monosaccharides
• Often called simple sugars, are compounds which
possess a free aldehyde (—CHO) or ketone (= CO)
group and 2 or more hydroxyl (—OH) groups. They
are, in fact, the simplest sugars and cannot be
hydrolyzed into smaller units.
• General formula is Cn(H2O)n or CnH2nOn.
• Subdivided into trioses, tetroses, pentoses, hexoses,
heptoses etc., depending upon the number of carbon
atoms they possess; and as aldoses or ketoses,
depending upon whether they contain aldehyde or
ketone group.

6. Oligosaccharides
• These are compound sugars that yield 2 to 10
molecules of the same or different
monosaccharides on hydrolysis.
• Disaccharides - Sucrose, Lactose, Maltose,
Cellobiose, Trehalose
• Trisaccharides - Raffinose, Rabinose
• Tetrasaccharides - Stachyose
• Pentasaccharide - Verbascose

7. Polysaccharides
• These are also compound sugars and yield
more than 10 molecules of monosaccharides
on hydrolysis.
• General formula is (C6H10O5)x.
• Homopolysaccharides -Starch, Glycogen,
Inulin, Cellulose, Pectin, Chitin
• Heteropolysaccharides -Hyaluronic acid,
Chondrotin

8. Asymmetry
• A carbon atom to which 4 different atoms or
groups of atoms are attached is said to be or
chiral.
A
B C D
E

9. ISOMERISM
• Different compounds with the same molecular
formula
• Isomers are of 2 types : structural isomers and
stereoisomers
• Structural isomers have the same molecular
formula but possess different structures.
• Difference in structure may be: exhibited either in
the length of the carbon chain or in the position of
a substituent group or in possessing different
functional groups.

10. Stereoisomers
• Have the same molecular formula and the
same structure but differ only in spatial
configuration.
• 2 types : geometrical and optical.
• Geometrical isomers

11. Optical isomers
• (Enantiomers) differ from each other in the
disposition of the various atoms or groups of
atoms in space around the asymmetric carbon
atom.

12. Epimers
• Any two sugars which differ from each other only in the
configuration around a single asymmetric carbon atom
other than the carbonyl carbon atom are called epimers.
• Glucose and galactose, for example, form an epimeric pair
as they differ with respect to carbon 4 only. Similarly,
glucose is also epimeric with mannose (differing in C2
configuration).

13. OPTICAL ISOMERISM
• A compound rotating the plane of polarized light to
the right is called as dextrorotatory
• Compound causes rotation of polarized light to the
left, it is said to be levorotatory
• When equal amounts of dextrorotatory and
levorotatory isomers are present, the resulting
mixture becomes optically inactive because the
optical activities of each isomer cancel each other.
Such a mixture is called a racemic and this process
of converting an optically active compound into the
racemic modification is known of racemisation.

14. Mutarotation
• When a monosaccharide is dissolved in water,
the optical rotatory power of the solution
gradually changes until it reaches a constant
value.

16. FORMULATION OF
MONOSACCHARIDES
• Formula of Glucose—Linear Form

17. Ring Form

18. PYRANOSE FORM

19. FURAN

20. Mode of conversion of two hexose sugars from Fischer
projection formula to Haworth perspective formula

21. Anomers
• Diastereoisomers that differ in configuration only
around the hemiacetal or anomeric carbon atom.

22. Chemical Reactions of
Carbohydrates

23. • Carbohydrates possess active groups which are
responsible for their chemical behaviour.
• These groups are glycosidic OH, alcoholic OH
and CHO (or CO).

24. REACTION OF GLYCOSIDIC
OH GROUP
• Reaction with alcohol
Glycosides occur in nature:
e.g., phlorhizin (glucose + phloretin) in rose bark ; digitonin (4 galactose +
xylose + digitogenin) in foxglove leaves; amygdalin (2 glucose + 2
mandelonitril) from bitter almonds and saponin (sugar + sapogenin) from
soapwort.

25. REACTION INVOLVING BOTH GLYCOSIDIC
AND
ALCOHOLIC OH GROUPS
• Reaction with acetic anhydride (Esterification)

26. REACTION OF ALCOHOLIC OH GROUP
• Reaction with methyl iodide (Etherification).

27. REACTION INVOLVING BOTH ALCOHOLIC OH
AND CHO/CO GROUPS
With mild oxidants (like HOBr) − Only the aldehyde
group is oxidized to produce monocarboxylic acids.
With strong oxidants (like conc. HNO3) − Both the aldehyde group (or
ketone group) and the primary alcohol group are oxidized to yield
dicarboxylic acids.

28. REACTIONS OF CHO/CO GROUP
• Oxidation with metal hydroxides

30. REDUCTION
•With sodium amalgam

31. With Strong Mineral acids

32. WITH DILUTE ALKALIES
• Glucose, fructose and mannose are interconvertible in weak alkaline solutions
such as Ca(OH)2 and Ba(OH)2 at low temperatures.
• Enolization, the migration of a proton from a carbon atom onto the oxygen of
an adjacent carbonyl group, resulting in the formation of an unsaturated
alcohol called enol.

33. REACTION WITH ALANINE

34. Reaction with phenyl hydrazine
Osazone formation

35. Reaction with hydroxylamine

36. Fermentation

37. Oligosaccharides

38. Disaccharide
• Sucrose
• Table sugar, Cane sugar, Beet sugar
• Properties. Sucrose is a white crystalline solid, soluble
in water and with a melting point 180°C.
• When heated above its melting point, it forms a brown
substance known as caramel. Concentrated sulfuric acid
chars sucrose, the product being almost pure carbon. It is
dextrorotatory and has a specific rotation of + 66.7°. It is
by far the sweetest of the 3 common disaccharides
(sucrose, lactose, maltose). It is also sweeter than glucose.
It crystallizes in colourless crystals.

39. STRUCTURE OF SUCROSE

40. Hydrolysis
• Upon hydrolysis, sucrose yields equimolar mixture
of glucose and fructose which is often called invert
sugar.
• Sucrose (which is dextrorotatory with a specific
rotation, + 66.7°), upon hydrolysis, gives a mixture
of equimolar quantities of D(+) glucose
(dextrorotatory ; + 52.7°) and D(–) fructose
(levorotatory;– 92.0°). And as the levorotation of
fructose is greater than the dextrorotation of
glucose, the mixture so obtained is levorotatory,
contrary to the initial dextrorotatory sucrose.

41. Inversion of sucrose

42. Some artificial sweeteners

43. LACTOSE

44. • Properties:
• Lactose is a white, crystalline solid with a
melting point 203°C (with decomposition) and
is also dextrorotatory. The α- and β-forms have a
specific rotation of + 90° and +35° respectively.
• It is less soluble in water and much less sweet
than sucrose.

45. Hydrolysis
• Upon hydrolysis with the enzyme, lactase, it
yields an equimolar mixture of glucose and
galactose.

46. MALTOSE
• It is the major product of enzymic hydrolysis of
starch. Sprouting cereal grains are rich in
amylases which split the starch present to dextrins
and maltose. Malt, prepared from sprouting
barely, is an excellent source of maltose.

48. • Properties. Maltose is a white crystalline
solid, with a melting point 160–165 °C. It is
soluble in water and is dextrorotatory.
• Hydrolysis. Maltose is easily hydrolyzed into
2 identical units of glucose by dilute acids or
by the enzyme, maltase, found in the intestine.
It should also be noted that the enzyme maltase
hydrolyzes or splits only α-glycoside linkages
and has no action upon β-glycosides.

49. CELLOBIOSE
• Chemistry. Cellobiose is identical with
maltose except that the former has a β-1, 4-
glucosidic linkage in contrast to the α-1, 4-
glucosidic of the latter.
• Properties. Cellobiose is a white crystalline
solid with a melting point 225 °C. It is
soluble in water and is dextrorotatory.

50. ISOMALTOSE

51. TREHALOSE

52. POLYSACCHARIDES

53. Classification
• Polysaccharides may be distinguished into
homopolysaccharides (or homoglycanes),
which yield, on hydrolysis, a single
monosaccharide and heteropolysaccharides
(heteroglycanes), which produce a mixture
of monosaccharides on hydrolysis.

54. BASED ON THEIR FUNCTIONALASPECT
(a) Nutrient (or digestible) polysaccharides.
These act as metabolic reserve of
monosaccharides in plants and animals, e.g.
starch, glycogen and inulin.
(b) Structural (or indigestible) polysaccharides.
These serve as rigid mechanical structures in
plants and animals, e.g. cellulose, pectin and
chitin and hyaluronic acid and chondroitin.

55. HOMOPOLYSACCHARIDES
• These yield, on hydrolysis, a single
monosaccharide. They serve as both storage
(starch, glycogen, inulin) and structural
(cellulose, pectin, chitin) polysaccharides.

56. STARCH
• It consist of two components : amylose (15-
20%), a long unbranched straight-chain
component and amylopectin (80-85%), a
branched chain polysaccharide.

57. α-amylose
• α-amylose or simply amylose has a molecular
weight range of 10,000 to 50,000.
• Formed in plant cells by elimination of a molecule of
water from glycosidic OH group of one α-D-glucose
molecule and alcoholic OH group on carbon 4 of the
adjacent α-D-glucose molecule.
• The linkage in amylose is, thus, an α-1, 4-glucoside,
like that in maltose.

58. Amylopectin
• Has a high molecular weight range of 50,000 to
1,000,000, thus indicating the presence of 300 -
5,500 glucose units per molecule.
• Possesses the same basic chain of α-1, 4-glucoside
linkage like that of amylose but has, in addition,
many side chains attached to the basic chain by α-
1, 6-glucoside linkages
• The average chain length is about 24 glucose
units.

60. Glycogen
• Major reserve food in animals
• Branched-chain polysaccharide and resembles
amylopectin very much in structure, rather than
amylose, but has somewhat more glucose residues per
molecule and about one-and-a-half times as many
branching points.
• The chains are shorter (10-20 glucose units), and
hence the molecule is even more highly branched and
more compact.

61. Inulin
• Inulin has a molecular weight of about 5,000
and consists of about 30-35 fructose units per
molecule.
• It is formed in the plants by eliminating a
molecule of water from the glycosidic OH
group on carbon atom 2 of one β-D-fructose
unit and the alcoholic OH group on carbon
atom 1 of the adjacent β-D-fructose unit.

63. Cellulose
• The molecular weight of cellulose ranges between
200,000 and 2,000,000, thus corresponding to
1,250-12,500 glucose residues per molecule.
• It may be formed by taking out a molecule of
water from the glycosidic OH group on carbon
atom 1 of one β-D-glucose molecule and the
alcoholic OH group on carbon atom 4 of the
adjacent β-D-glucose molecule.

64. Pectin
• Pectin is a polysaccharide of α-D-galacturonic
acid where some of the free carboxyl groups
are, either partly or completely, esterified with
methyl alcohol and others are combined with
calcium or magnesium ions.

65. Chitin
• A linear polymer of N-
acetyl-D-glucosamine
units joined together by
β-1, 4-glucosidic
linkages.
• The excellent
mechanical properties
of insect skeleton are
due to chitin.

66. HETEROPOLYSACCHARIDES
• Hyaluronic acid : It is a straight-chain polymer
of D-glucuronic acid and N-acetyl-D-
glucosamine (NAG) alternating in the chain.
Acts as component of various tissues such as the vitreous body of the eye, the umbilical
cord and the synovial fluid of joints.

67. Chondroitin Sulfates
• Major structural components of cartilage,
tendons and bones.
Chondroitin sulfate A : D-glucuronic acid (β-1 → 3 or β-1 → 4) N-acetyl-D-galactosamine-4-
sulfate
Chondroitin sulfate C: D-glucuronic acid (β-1 → 3 or β-1 → 4) N-acetyl-D-galactosamine-6-
sulfate

68. Dermatan Sulfate
• Similar to chondroitin sulfate
• D-glucuronic acid is replaced by L-iduronic
acid
• (L-iduronic acid + N-acetyl-D-galactosamine-4-
sulfate)

69. Keratan sulfate
• Uronic acid component is replaced by D-
galactose
• D-galactose (β-1 → 4 or β-1 → 3) N-acetyl-D-
glucosamine-6-sulfate

70. Heparin
• Heteropolysaccharide composed of D-
glucuronic acid units, most of which (about 7
out of every 8) are esterified at C2 and D-
glucosamine-N-sulfate (=sulfonylamino glucose)
units with an additional O-sulfate group at C6.
Heparin acts as an anticoagulant.

71. THANKS