CHEMISTRY PROJECT

Topic: carbohydrates
Submitted to: submitted by:
Mrs.Premsheela singh gaurav kumar arya
(PGT CHemistry) (xii a)(‘19’)
 CERTIFICATE
This is to certify that GAURAV KUMAR ARYA
of CLASS 12TH of JNV NAINITAL has
successfully completed his project on
CARBOHYDRATES under my supervision .
He has taken proper care and shown utmost
sincerity in completion of the project.I certify
that this project up to my expectation and as
per guidelines issued by CBSE.
Mrs.PREMSHEELA SINGH
(P.G.T. CHEMISTRY)
INTERNAL EXAMINER
 Acknowledgement
I wish to express my deep gratitude and sincere thanks to MR.RAJ SINGH ,
PRINCIPAL JAWAHAR NAVODAYA VIDYALAYA, NAINITAL for his
encouragement and for all the facilities that provided for project work. I
sincerely appreciate this magnanimity by taking me into fold for which I shall
remain embedded to him. I extend my heartily thanks to MRS. PREMSHEELA
SINGH MA’AM who guided me to the successful completion of this project
work. I take this opportunity to express my deep sense of gratitude for his
invaluable guidance ,constant encouragement , constructive comments,
sympathetic attitude and immense motivation which has sustained my efforts
to all the stages of size of this project for work .
I can't forget to offer my sincere thanks to my classmates to help me to carry
this project successfully and for their valuable advice and support which I
received from them time to time.
THANK YOU
GAURAV KUMAR ARYA
ROLL NO. 19
 CARBOHYDRATES
 Carbohydrates are the most abundant organic molecules in nature. They
have a wide range of functions, including providing a significant fraction
of the energy in the diet of most organisms, acting as a storage form of
energy in the body, and serving as cell membrane components that
mediate some forms of intercellular communication. Carbohydrates also
serve as a structural component of many organisms, including the cell
walls of bacteria, the exoskeleton of many insects, and the fibrous
cellulose of plants.
 The carbohydrates as the name implies are composed of carbon,
hydrogen and oxygen with the latter two element in the ratio of 2 to 1 as
in water The empiric formula for carbohydrates is (CH2O)n.
 Structurally carbohydrates are polyfunctional compounds. They contain
two types of functional groups-hydroxyl and carbonyl. They may be
polyhydroxy aldehydes or polyhydroxy ketones.

Formation of carbohydrates in nature occurs in green plants by a process
called photosynthesis, plant contain the green pigment chlorophyll, which
catalyses the conversion of carbon dioxide and water into sugar.
 Classification and nomenclature of
carbohydrates
 The carbohydrates are divided into three major classes depending
upon whether or not they undergo hydrolysis and if they do, on the
number of products formed.
 Monosaccharides: The monosaccharides are polyhydroxy
aldehydes or polyhydroxy ketones which cannot be decomposed by
hydrolysis to give simpler carbohydrates. e.g. Glucose, fructose,
Galactose etc.
 Oligosaccharides: The oligosaccharides (Oligo: few) are
carbohydrates which yield a definite number (2-9) of
monosaccharide molecules on hydrolysis.
 Disaccharides - Which yield two monosaccharides molecules on
hydrolysis. Which have molecular formula is C12H22O11.e.g.
Sucrose, maltose etc
 Trisaccharides - Which yield three monosaccharides molecules on
hydrolysis and have molecular formula is C18H32O16.

 Trisaccharides - Which yield three monosaccharides molecules on
hydrolysis and have molecular formula is C18H32O16.

 Tetrasaccharides - Which yield four monosaccharides molecules on

hydrolysis and have molecular formula is C22H42O21. eg: Stachyose
[gal(α1→6)gal(α1→6)glu(α1↔2β)fru]
 Polysaccharides: The carbohydrates which have higher molecular weight,
which yield many monosaccharide molecules on hydrolysis. E.g. Starch,
glycogen, Dextrin, Cellulose etc.

In general monosaccharides and oligosaccharides are

crystalline solids, soluble in water and sweet to taste,
they are collectively known as sugars, the polysaccha-
rides on the other hand are amorphous, insoluble in
water and tasteless, they are called non-sugars.
Classification of Carbohydrates :
 Maltose and Cellobiose
 Both maltose and cellobiose are composed of two glucose molecules. But in
maltose the glucose molecules are in the α configuration and joined with an
α(1→4) link while in cellobiose they are in the β configuration and joined with a
β(1→4).
 Pentose Sugar:
 A pentose is a monosaccharide with five carbon atoms.
 Pentoses are organized into two groups.
 Aldopentoses have an aldehyde functional group at position 1.
 Ketopentoses have a ketone functional group in position 2 or 3.

 Aldopentoses: The aldopentoses have three chiral centers and therefore eight
different stereoisomers are possible.

Ketopentoses: The 2-ketopentoses have two chiral centers, and therefore

four different stereoisomers are possible. The 3ketopentoses are rare
 Note By: Synthetic sweetening agents

•The carbohydrates may also be classified as either reducing or non

reducing sugars. All those carbohydrates which have ability to reduce
Fehiling’s solution and Tollen’s reagents are referred to as reducing
sugars, while others are non reducing sugars. All monosaccharides
and disaccharides other than sucrose are reducing sugars.
Carbohydrates are also said to be saccharides
Sugars exhibit various forms of isomerism:
•The maximum number of optical isomers of a sugar is related to the
•number of asymmetric carbon atoms in the molecules and may be
• calculated by the following equation,
Maximum Number of Optical Isomers = 2n [n = the asymmetric carbon
•Glucose, with four asymmetric carbon atoms, can form 16 isomers.
• The more important types of isomerism found with glucose are as
• follows.
•D and L isomerism:
•The designation of a sugar isomer as the D form or of its mirror image
• as the L form.
•The L and D forms of the sugar depends on the orientation of the –H
• and -OH groups around the carbon atom adjacent to the terminal
•primary alcohol carbon (carbon 5 in glucose) determines whether the
• sugar belongs to the D or L series.
•When the -OH group on this carbon is on the right, then sugar is the
• D-isomer; when it is on the left, then it is the L-isomer.
Most of the monosaccharide occurring in mammals is D sugars,
and the enzymes responsible for their metabolism are specific for
this configuration. In solution, glucose is dextrorotatory—hence the
alternative name dextrose.The presence of asymmetric carbon
atoms also confers optical activity on the compound. When a
beam of plane-polarized light is passed through a solution of an
optical isomer, it will be rotated either to the right, dextrorotatory
(+); or to the left, levorotatory (-). The direction of rotation is
independent of the stereochemistry of the sugar, so it may be
designated D (-), D (+), L (-), or L (+). For example, the naturally
occurring formof fructose is the D (-) isomer.
Alpha and beta anomers:
•The anomeric centre of a sugar is a stereocentre created from the
intramolecular formation of an acetal (or ketal) of a sugar hydroxyl group
and an aldehyde (or ketone) group. The two stereoisomers formed from
the two possible stereochemistries at the anomeric centre are called
anomers. They are diastereoisomers of one another.
Cyclic Structures and Anomeric Form Alcohols react readily with
aldehydes to form hemiacetals This reaction is promoted in the
presence of either acid or base One of the subtleties of this reaction
involves the stereochemistry of the aldehyde and keto carbon it goes
from being achiral to chiral.

•Similarly alcohols react with ketones to produce hemiketals:

 Characters Starch Glycogen Cellulose
α-glucose
Amylose: (60 to 300 α-glucose
Monomer Unit) α-glucose β-glucose
Amylopectine: (300 to (6000 to 30,000 α-glucose (300 to 2500 β-glucose
6000 α- glucose Unit) Unit) Unit)

Type of α(1→4) glycosidic bond α(1→4) and α(1→6)

(Amylose) +
bond α(1→4) and α(1→6) glycosidic glycosidic bonds β(1→4) glycosidic bond
between bond (Amylopectin)
monomers
Nature Amylose is coiled Short many branched chains, Straight, long
of chain unbranched Amylopectin some coiling unbranched chains
is long branched form H-bonds, with
chains, some coiling adjacent chains
Occurrence In plants In animals and fungi In plants
Function Carbohydrate energy store Carbohydrate energy store Structural
General form Grains Small granules Fibres
Chemical Test Deep Blue-Violet color Reddish brown color Negative test
or Iodine test
•MUTAROTATION IN SUGAR
•Mutarotation is the change in the optical rotation because of the
change in the equilibrium between two anomers, when the
corresponding stereocenters interconvert. Cyclic sugars show
mutarotation as α and β anomeric forms interconvert.
•The optical rotation of the solution depends on the optical rotation of
each anomer and their ratio in the solution.
•Mutarotation was discovered by French chemist Sir Dubrunfaut in
1846, when he noticed that the specific rotation of aqueous sugar
solution changes with time. [The organic fructose molecule was
subsequently discovered by Dubrunfaut in 1847].
•Sugars in the ring form can exist in two states, one where the C-1
hydroxy group is above the plane of the ring (β) and one where it is
below (α).
•In aqueous solution there is a constant interchange between the
various conformations via the breaking open of the hemi acetal
structure and its subsequent reforming.
 Hermann Emil Louis Fischer (9 October 1852 –  Sir (Walter) Norman Haworth (19 March 1883
15 July 1919) was a German chemist and 1902 – 19March 1950) was a British chemist.
recipient of the Nobel Prize in Chemistry.  He received the 1937 Nobel Prize in Chemistry "for
 He also discovered the Fischer esterification. his investigations on carbohydrates and vitamin
 He developed the Fischer projection, a symbolic C".
way of drawing asymmetric carbon atoms.