1. Identification of Unknown Carbohydrates By Dr. Mohammed Golam Rasul

2. السلام عليكم ورحمة الله وبركاته

3. بسم الله الرحمن الرحيم

4. Objective Study the various qualitative tests of carbohydrates.
Identify an unknown carbohydrate.

5. Definition
Organic compounds composed of C, H and O with H and O present in the same ratio as in water.
Example: Glucose C6H12O6. [Cm(H2O) n ] m, n= where m and n are integer.
Exceptions:
Deoxy sugars such as Rhamnose C6H12O5, Acetic acid C2H4O2. Formaldehyde HCHO, Lactic acid C3H6O3
New definition:
Optically active Polyhydroxy aldehydes or ketones, or substances that hydrolyze to yield polyhydroxy aldehydes or ketones.

6. Physical Characteristics
State:
Sugars are white, crystalline in shape and with sharp melting points, while polysaccharides are white amorphous solids.
Taste:
Sugars have a sweet taste. Polysaccharides are tasteless.
Solubility:
Monosaccharides are soluble in cold water and hot alcohol. Polysaccharides are partially soluble in hot water.

7. Qualitative Analysis Test
Is concerned with determining the identity of a substance.
Enables us to detect the presence of things which may be beyond the reach of our senses.

8. Types of Carbohydrates
Monosaccharides are the simplest carbohydrates
- Also called “simple sugars”
- Examples: glucose, fructose, galactose, ribose
Disaccharides are two monosaccharides bonded together.
- Examples: sucrose (table sugar), lactose (milk sugar)
Polysaccharides are polymers of monosaccharides
- Can be split into many monosaccharides with acid or enzymes
- Examples: starch, cellulose, glycogen

9. Carbohydrates Characterization
Molisch’s Test : carbohydrate
Benedict’ s Test : color change indicator for simple sugars
Fehling Test: Reducing sugars
Barfoed’s Test: Monosaccharides and Oligosaccharides
Seliwanoff Test : Differentiation of Ketose from Aldose
Iodine Test : Cellulose, Starch, Dextrin

10. Qualitative Tests for Carbohydrates
1. Molisch’s Test
- test for carbohydrates
a-naphthol
Pentose/
Hexose
conc.H2SO4
Furfural
5-hydroxymethyl furfural
(Purple complex)
- H2O
2. Barfoed’s Test
- test for reducing sugars
- test for distinguishing monosaccharides and disaccharides
Slightly acidic
Reducing sugar + 2Cu2+
2Cu+ + oxidized sugar
Cu2O
(brick red ppt)
3. Seliwanoff Test
- test for distinguishing ketose from aldose
resorcinol
conc. HCl
5-hydromethyl
furfural
Ketohexose
red complex
dehydration
4. Iodine Test
- test for starch
Starch + I2
starch - I2 complex (deep blue)

11. Qualitative Tests for Carbohydrates
5. Fehling’s Test
- test for reducing sugars
- test for distinguishing monosaccharides and disaccharides
Reducing sugar + Fehling reagent
Boiling in water bath
Cu2O
( red ppt)
6. Benedict’s Test
- test for reducing sugar
Reducing sugar + Benedict’s reagent
Boil
red ppt

12. Molisch’s Test
Test for carbohydrate materials
Procedure: Using 2 ml of test solution in a test tube, add 2 drops of 1%  1-naphthol, mix and then allow 2 ml of conc. Sulphuric acid to flow down the side of the inclined tube to layer under the mixture. Note the colour at the junction.

13. Barfoed’s Test Test for Monosaccharides and Oligosaccharides
Procedure: To 2 ml of a sample solution is placed in a test tube. 2 ml of Barfoed's reagent is added. The solution is then heated in a boiling water bath for three minutes.

14. Seliwanoff Test Test for Differentiation of Ketose from Aldose
Procedure: Add 0.5 ml of the test solution to 2.5 ml of the Seliwanoff’s reagent. Place the tubes in boiling water and note the results and continue heating, observe the colour change at after 1 minute.

15. Iodine Test Test for Cellulose, Starch, Dextrin
Procedure: Add a drop of dil. HCl to 1 ml test solution to acidify the solution. Add few drops of iodine solution. Record the colours observed. Gently warm the solution and then cool it. Note he change.

16. Fehling’s Test
Test for Monosaccharides and Oligosaccharides
Procedure: Using 0.5 ml of test solution, mix with 2.0 ml of Fehling’s solution in a test tube and heat the mixture. Red precipitate indicates the presence of reducing sugar.

17. Benedict’s Test
Test for Monosaccharides and Oligosaccharides
Procedure: Using 0.5 ml of test solution, mix with 5 ml of Benedict’s reagent in a test tube and heat the mixture. Appearance of red precipitate indicate the presence of reducing sugar.

18. THANK YOU FOR YOUR ATTENTION