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CHEMISTRY LAB

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Joyce Angelica Sisracon

on 25 September 2013

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Transcript of CHEMISTRY LAB

Test for Reducing Property of Sugars
Other Test:

Iodine Test
Hydrolysis of Sucrose
Experiment No. 17:
Carbohydrates Chemistry

Carbohydrates
are polyhydroxy carbonyl compounds or those substances that produce them upon complete hydrolysis

Color Reactions And Tests
Osazone Test
Molisch Test
Seliwanoff's Test
Mucic Acid Test
Compostion of Reagent
Phenylhydrazine HCL + Sodium Acetate
PROCEDURE
Osazone Test
a.k.a
Phenylhydrazine Test
This test is used to identify sugars whose stereochem differed by one chiral carbon and for monosaccharides.
Result
Compostion of Reagent
a-naphtol + ethanol
Molisch Test
General test for Carbohydrate
a sensitive chemical test for the presence of
PROCEDURE
result
purple ring @ junction
Schiff's Test
Fuchsin + Sodium Bisulfite + HCl
composition of reagent
Schiff's Test
It is a qualitative test performed in order to detect the possible presence of aldehydes
procedure
result
composition of reagent
conc. resorcinol + HCl
Seliwanoff's Test
a chemical test which distinguishes between aldose and ketose sugars
procedure
result
reddish brown
magenta
composition of reaction
H2O + HNO3
procedure
Mucic Acid Test
a test for identification of galactose which is a component of antigens
result
presence of crystals
Fehling's Test
composition of reagent
Fehling's A: CuSO4 + NaOH
Fehling's B: Na-K tatrate
Fehling's Test
It is a test to distinguish between reducing sugars and non-reducing sugars
procedure
result
Benedict's Test
composition of reaction
CuSO4 + Na2CO3
Benedict's Test
It is a test for the presence of reducing sugars
procedure
Tollen's Test
composition of reagent
AgNO3 + NaOH
result
brick red- positive
light blue- negative
Tollen's Test
It is a test to distinguish aldehyde and ketone
procedure
result
pale yellow-negative
silver mirror-positive
Picric Test
composition of reagent
phenol + HNO3
Picric Acid Test
It is a test used to determine the presence and the levels of reducing sigars
procedure
yellow
sucrose
Barfoed's Test
composition of reagent
Copper Tartrate + Acetic acid
Barfoed's Test
A test used for detecting the presence of monosaccharide
procedure
result
composition of reagent
I2 + KI + H20
Iodine Test
It is a test for detection of polysaccharide to differentiate bet. starch, dextrin, and glycogen
procedure
result
Hydrolysis of
starch

PROCEDURES
result
mahogany red
glucose
blue light
starch
sucrose
glucose
Tollen's
blue
colorless
procedure
Fehling's
Benedict's
Fehling's
Benedict's
Tollen's
procedure
negative & postive
hydrolysis of sucrose
yields glucose and
fructose
galactose
brick red
glucose
brick red
lactose
brick red
sucrose
blue
fructose
brick red
maltose
brick red
orange-brown
light blue
mettalic silver

Carbohydates and 1-2 diols gives a positive result to this test.
monosaccharides, isaccharides, and polysaccharides should give a positive reaction which is a purple ring at junction of two liquids. Nucleic acids and glycoproteins also give a positve reaction
This test gives a positve result to carbohydrates with an aldehyde functinal group. Dark pink - purple color indicates a positive result
The test reagent dehydrates ketohexoses to form 5-hydroxymethylfurfural which further rects with resorcinol present in the test reagent to produce a red to reddish brown product within two minutes or less. Aldohexoses form the same product, but do so very very slowly.
This test is used for reducing sugars which have free aldehyde or ketone group. Cupric ion complex with tarttrate ion is reduced to cuprous oxide. a positive result is indicated by the formation of brick red precipitate
Benedict's reagent is used as a test for the presence of reducing sugars. This includes all monosaccharides and the disaccharides , lactose and maltose. Thus, although the ketose fructose is not strictly a reducing sugar, it is an alpha- hydroxy - ketone , and gives a positive test because it is converted to the aldoses glucose and mannose by the base in the reagent. Carbohydrates which react with Benedict's reagent to reduce the blue copper (II) ion to form a brick red precipitate
Formation of a silver mirror is an indication of a positive result
The test is similar to the Fehling's reaction with aldehydes. It is based on the reduction of copper acetate to copper oxide which forms a brick red precipitate
colorless
Amylose in starch is responsible for the formation of a deep blue color in the presence of iodine. The iodine molecule slips inside of the amylose coil.
A blue-black color results if starch is present. Thus, this test will give a negative result to glucose and sucrose.
yellow osazone crystal
procedure
Iodine Test Result
Reaction of Hydrolyzed Starch
Starch is a non reducing polysaccharide therefore it does not give positive result with Benedict’s, Fehling’s. Tollen's and Barfoed’s reagents, nor does it form any Osazone.
However after hydrolysis into monosaccharide by the actions of strong acid , its components (glucose molecules) giveall the test positive.
The body uses the monosaccharide glucose as its source of energy. In order for energy to be obtained from sucrose, starches and other saccharides, the organism must first break them down into glucose. This reaction entails the hydrolysis of the glycosidic linkages catalyzed by a collection of enzymes. However, in this experiment, we used HCl as a catalyst.
PROCEDURE
What is the importance of HCl in hydrolysis of starch?
Starch is made up of a long chain of glucose molecules held together by glycosidic bonds. One carbon in the ring is bound to an oxygen which is bound to the carbon of another ring: this is the glycosidic bond. This C-O-C bond, an ether linkage, can be broken through hydrolysis to release the constituent glucoses.

Hydrochloric acid puts H+ in your solution. The lone pairs of the oxygen in the C-O-C bond will attack this H+. Now oxygen is bound to three things; it is unstable. Because acid allows this destabilization to occur, it lets hydrolysis of the bond occur.
chemistry laboratory
Hydrolyzed starch with Fehlings
procedure
result
Full transcript