Abstract
Carbohydrates, or sachharides are sugars and starches that provide energy for us
humans and animals. In this experiment, carbohydrates are tested with different
reagents, and two unknown samples are examined to determine their identity. For the
identification of unknown carbohydrate sample, six different carbohydrates and two
unknown samples with 0.20ml volume was placed in separate test tubes. It was tested
with Molisch reagent, wherein 0.20ml of Molisch reagent was added to each sample.
For Benedict, Barfoed, Iodine, Seliwanoff, and 2,4-DNP test, 0.20 ml of their
corresponding reagent was supplemented on each carbohydrate sample and they were
Cooled down in an ice bath afterwards.Results and reaction was taken and observed so
that the identity of the two unknown samples can be determined. After carefully
analyzing the data, the unknown samples were identified to be Fructose and Ribose.
Introduction
Carbohydrates are carbon compounds that contain great amounts of hydroxyl groups.
The simplest carbohydrates also comprise either an aldehyde moiety
(polyhydroxyaldehydes ) or a ketone moiety (polyhydroxyketones). All carbohydrates
can be categorized as monosacchrides, oligosaccharides or polysaccharides.
Somewhere from two to ten monosaccharide units, linked by glycosidic bonds, make up
an oligosaccharide. Polysaccharides are much bigger, having hundreds of
monosaccharide units. The existence of the hydroxyl groups permits carbohydrates to
interrelate with the aqueous nature and to participate in hydrogen bonding, both inside
and between chains. Derivatives of carbohydrates can contain nitrogen, phosphate and
sulfur compounds. Carbohydrates also can unite with lipids to form glycolipids or with
proteins to form glycoproteins.
Materials and Method
Precautions: In handling conc. Acid was carefully supervised for it was corrosive.
Thermal gloves was used
In identification of unknown carbohydrates sample, 0.20 ml of the known carbohydrate
and two unknown sample was transferred on seperate test tube and properly labeled.
0.20 ml of Molisch reagent was added followed by H2SO4 to each sample, Changed in
color was observed and recorded. Separate test tubes on different samples on each
chemical test (Iodine, Benedict’s, Barfoed’s, Seliwanoff’s, and Bial’s test) color changed
was observed. The identity of the Unknown samples was determined by comparing it
against that of the known carbohydrate samples.
Result and Discussion
A. Reactions of Carbohydrates and Identification of Unknown
, Table 1. Positive Reactions for Carbohydrates Test
Test Positive Color Change
Molisch Deep purple color
Iodine Blue w/black color
Benedict blue
Barfoed Rust colored
Seliwanoff ketoses (red)
2,4 DNP Yellow black
Table 2. Reaction of Carbohydrates Samples
Samples Molisch Iodin Benedi Barfoe Seliwanoff 2,4
e ct d DNP
Glucose + - + ++ - +
Galactose + - + ++ - +
Ribose + - ++ + - +
Lactose + - + - - +
Sucrose ++ - - - - ++
Starch + ++ - - - -
Fructose ++ - + + ++ ++
Unknown 1 ++ ++ ++ ++ ++ ++
Unknown 2 + + + - - +
Identity of Unknown Fructose
1:
Identity of Unknown Ribose
2:
Legend: ++ - fast reaction/ + - slow reaction/ - no reaction
Molisch test is a test used to describe the basis of qualitative tests for
monosaccharides, disaccharides and polysaccharides and use the test to distinguish
specific sugars form each other. A deep purple color occur because of the presence of
Carbohydrates, or sachharides are sugars and starches that provide energy for us
humans and animals. In this experiment, carbohydrates are tested with different
reagents, and two unknown samples are examined to determine their identity. For the
identification of unknown carbohydrate sample, six different carbohydrates and two
unknown samples with 0.20ml volume was placed in separate test tubes. It was tested
with Molisch reagent, wherein 0.20ml of Molisch reagent was added to each sample.
For Benedict, Barfoed, Iodine, Seliwanoff, and 2,4-DNP test, 0.20 ml of their
corresponding reagent was supplemented on each carbohydrate sample and they were
Cooled down in an ice bath afterwards.Results and reaction was taken and observed so
that the identity of the two unknown samples can be determined. After carefully
analyzing the data, the unknown samples were identified to be Fructose and Ribose.
Introduction
Carbohydrates are carbon compounds that contain great amounts of hydroxyl groups.
The simplest carbohydrates also comprise either an aldehyde moiety
(polyhydroxyaldehydes ) or a ketone moiety (polyhydroxyketones). All carbohydrates
can be categorized as monosacchrides, oligosaccharides or polysaccharides.
Somewhere from two to ten monosaccharide units, linked by glycosidic bonds, make up
an oligosaccharide. Polysaccharides are much bigger, having hundreds of
monosaccharide units. The existence of the hydroxyl groups permits carbohydrates to
interrelate with the aqueous nature and to participate in hydrogen bonding, both inside
and between chains. Derivatives of carbohydrates can contain nitrogen, phosphate and
sulfur compounds. Carbohydrates also can unite with lipids to form glycolipids or with
proteins to form glycoproteins.
Materials and Method
Precautions: In handling conc. Acid was carefully supervised for it was corrosive.
Thermal gloves was used
In identification of unknown carbohydrates sample, 0.20 ml of the known carbohydrate
and two unknown sample was transferred on seperate test tube and properly labeled.
0.20 ml of Molisch reagent was added followed by H2SO4 to each sample, Changed in
color was observed and recorded. Separate test tubes on different samples on each
chemical test (Iodine, Benedict’s, Barfoed’s, Seliwanoff’s, and Bial’s test) color changed
was observed. The identity of the Unknown samples was determined by comparing it
against that of the known carbohydrate samples.
Result and Discussion
A. Reactions of Carbohydrates and Identification of Unknown
, Table 1. Positive Reactions for Carbohydrates Test
Test Positive Color Change
Molisch Deep purple color
Iodine Blue w/black color
Benedict blue
Barfoed Rust colored
Seliwanoff ketoses (red)
2,4 DNP Yellow black
Table 2. Reaction of Carbohydrates Samples
Samples Molisch Iodin Benedi Barfoe Seliwanoff 2,4
e ct d DNP
Glucose + - + ++ - +
Galactose + - + ++ - +
Ribose + - ++ + - +
Lactose + - + - - +
Sucrose ++ - - - - ++
Starch + ++ - - - -
Fructose ++ - + + ++ ++
Unknown 1 ++ ++ ++ ++ ++ ++
Unknown 2 + + + - - +
Identity of Unknown Fructose
1:
Identity of Unknown Ribose
2:
Legend: ++ - fast reaction/ + - slow reaction/ - no reaction
Molisch test is a test used to describe the basis of qualitative tests for
monosaccharides, disaccharides and polysaccharides and use the test to distinguish
specific sugars form each other. A deep purple color occur because of the presence of
