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Carbohydrates It constitute one of the most important groups of natural
products.
Discovered in 1838 by a French
chemist “Anselm Payen”
Payen isolated it from plant
matter and he named as
cellulose, and also he determined
its chemical formula.
Suffix “ose”
In 1920 by the Hermann
Staudinger determined
the polymer structure of
cellulose.
Occurrence: widely distributed plant
polysaccharide.
main constituent of the
cell walls of plants, green
algae, bacteria and in
tunicates.
most abundant naturally
occurring biopolymer(Cotton,Wood)etc..,
Colourless solid
Non melting
Relatively hygroscopic
Thermal decomposition
starts at 180°
Ignition Point: ˃290°
Density:1.52-1.59 g/cm 2
Insoluble in water and in
organic solvents
Undergoes severe
degradation in
concentrated acids.
It readily soluble in cupra
ammonium hydroxide
solution(Schweizer’s
reagent)
Cellulose is linear homopolymer composed of
D-glucopyranose units linked by 1,4-β-D-glucosidic bonds.
The chemical formula is (C6H10O5 )n
The hydroxyl groups are positioned in the ring plane
(equatorial), while the hydrogen atoms are in the vertical
position (axial).
Sodium hydroxide solution at different concentrations
and different temperatures could dissolve cellulose with
different DP.
According to different solubilities under specific
conditions, cellulose can be divided into three types:
α-Cellulose
β-Cellulose
γ-Cellulose
1.Elementary analysis -(C6H10O5 )n
2.
Cellulose
Crystalline D- glucose
(indicates that it is
composed of D-glucose
only)
2.Acid
hydrolysis
Tri substituted cellulose
(indicates that only three hydroxyl groups
are free per glucose unit)
3.Acetylation,
Methylation,
Nitration.
4.Acetolysis
Cellobiose
Octa-acetate
(indicates that
it is composed
of cellobiose
units)
But it does not
indicate that
whether it is α
or β glycosidic
linkage.
Cellulose
(fully methylated)
5. Hydrolysis2,3,6-trimethyl glucose
2,3,4,6-tetramethyl glucose
Without any dimethyl glucose
•Indicates that free
hydroxyl groups are
present in C2,C3,C6
•Hence the two
glucose units are
linked through
C1 and C4 (pyranose)
(or)
C1 and C5 (furanose)
•Since glucose is not
easily hydrolyzed it
must be C1 and C4
Indicate that it has
chain length of
about 100-200
units .
Indicates that cellulose
is a linear polymer
Results :
The two D-glucose units are in the pyranose form
Linked via C1 and C4
Cellulose Cellobiose,Cellotriose,
Cellotetraose,Cellopentose,
Cellohexose,Celloheptaose.
6.Gentle acidic hydrolysis
•These products were isolated
by Zechmeister in 1931and
miller in 1960.
•All these had C1 and C4
links and also shown to be β
7.To determine whether cellulose is linear or branched.
Cellulose Solvents Colloidal solution Due to its largeness
Forms fibres
therefore it
must be linear
Finally the long length and linear structure is
confirmed by X-ray analysis
8.The structure of cellulose is assigned
9. Cellulose is not planar
The absence of free rotation about C-O-C link due
to steric effect give rise to a rigid chain molecule.
The long chains are held together by hydrogen
bonding and has a three dimensional brick work.
10. To determine the value of ‘n’
n is the chain length (or)the molecular size.
This is the only problem in establishing the structure
of cellulose.
This can be achieved by determining the molecular
weight.
The two methods are
• Chemical( Haworth methylation and Periodic
oxidation)
• Physical.
Haworth methylation: It is a in complete methylation in an inert atmosphere
followed by hydrolysis with dilute acid to cleave all
the glycosidic linkages.
Results:It is indicated that the presence of chain having 100 to
200 D-glucose residues which corresponds to molecular
weight of cellulose between 20,000 to 40,000.
Drawbacks:
This method always give low molecular weight of
cellulose because of incomplete methylation.
Periodic oxidation(Hirst method) It is based on the estimation of formic acid liberated by
the action of potassium metaiodate.
The reagent liberates 2 molecules of formic acid and one
of formaldehyde from the reducing end.
One molecule of formic acid from the non reducing end.
Results:Estimation of formic acid produced gives the value of
chain length as approximately 100 glucose units.
Drawbacks:
The results are uncertain since over oxidation also takes
place due to progressive attack on the chain molecule
from their reducing ends
Viscosity, osmotic pressure,ultra centrifugal
sedimentation.
These methods indicated that cellulose has
molecular weight of nearly 2000-3000
Results shows divergence therefore the value
of n is uncertain.
It may vary with the condition under which the
polysaccharide are synthesized.
X-Ray studies indicate that the length of unit
cell(10.25Å) corresponds to the length of two D-
glucopyranose units (6.15Å)
X-Ray diffraction pattern indicates that the cellulose
is not crystalline but it is partly crystalline and partly
amorphous
1.Mercerized (smoothed)cellulose:
eg-mercerized cotton used in clothing fabric
2.Regenerated cellulose:
To regenerate too short fibres to long fibres used
in the formation of rayon manufacture.
Prepared from viscose process.
Due to the presence of hydroxyl groups,it can be
converted into various useful derivatives.
1.Nitrocellulose or gun cotton
2.Cellulose acetates
Triacetate is used in photographic film and in textile
industry
Diacetate is used in production of plastics,safety film base.
Monoacetate is used in the manufacture of toys,knife
handle,motor car parts.
First discovered in 1859 by “Rouget” while he
was experimenting with chemical and thermal
manipulation of the natural fiber chitin.
1811 Chitin was first discovered by Professor Henri Braconnot,who isolated it from mushrooms and name it “Fungine”.
1823 Antoine Odier found chitin while studying beetle cuticles and named “chitin” after Greek word “chiton”. (tunic, envelope)
1859 Rouget discovered chitosan, a derivative of chitin.
1950s The structure of chitin and chitosan was identified by X-ray diffraction, infrared spectra, and enzymatic analysis.
Chitosan is the N-deacetylated derivative of chitin
It is a linear polysaccharide composed of
β(1 4) linked D-glucos-2-amine units.
It is white to light red solid powder, insoluble in water
but soluble inorganic acids.
Unique characteristics of chitin and chitosan:
• Biocompatible
• Biodegradable
• Non-toxic
• Remarkable affinity to proteins
• Ability to be functionalized
• Renewable
• Abundant
Moisture content-• It absorbs moisture from atmosphere.• Particle size distribution: <30 mm.• determined by the gravimetric method.Solubility-• Sparingly soluble in water.• Practically insoluble in ethanol and other organic
solvents.• Solubility is affected by degree of deacetylation.PH: 4.0-6.0Density: 1.35-1.40 g/cm3Glass transition temperature: 203°C
Chitosan is a linear polyamine.
It has reactive amino groups (-NH2).
There is availability of reactive hydroxyl groups(-OH).
It has chelating ability for many transition metal ions.
Wade.L.G, Organic chemistry, eighth edition,Pearson publications, 2017 Jain.J.L,Sunjay Jain,Nitin Jain, Fundamentals of Biochemistry ,S.Chand
Publictions,New Delhi,Sixth edition,2010. Agarwal .O.P, Chemistry of Organic Natural products,Vol 2,Goel
publishing,2003 http://www.springer.com/cda/content/document/cda_downloaddocument/
9789400768970-c2.pdf?SGWID=0-0-45-1490458-p175144764 https://application.wiley-
vch.de/books/biopoly/pdf_v06/bpol6010_275_287.pdf https://www.springer.com/cda/content/document/cda_downloaddocumen
t/9781588290144-c2.pdf?SGWID=0-0-45-447173-p173727498 http://www.cfs.purdue.edu/class/f&n630/pdf_full/chitosan_NB.pdf http://meyersgroup.ucsd.edu/literature_reviews/2006/Litreview%20Chiti
n%20and%20Chitosan%20Po-Yu%20Chen.ppt https://s3.amazonaws.com/ppt-download/chitosan-151121074755-lva1-
app6892.pdf?response-content
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