identification of carbohydrates using tests

ppt

1. Identification of carbohydrates Dr. Muhannad O mer Assistant lecturer Gasha institute 3 rd Lab

2. Introductions The word carbohydrate is formed from the words carbon and hydrogen. Organic compounds composed of C, H and O with H and O present in the same ratio as in water.

3. 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.

4. 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 monosacchari

5. Molisch’s test  is a general test for carbohydrates. This test is given by almost all of the carbohydrates. In this test concentrated sulfuric acid converts the given carbohydrate into furfural or its derivatives, which react with α- naphthol to form a purple coloured product.

6. Experiment : Aim :- To Test the presence of carbohydrates in the given sample using Molisch’s test .

7. Materials required: Molisch’s reagent Glucose solution Concentrated sulfuric acid Test tubes Measuring cylinder Dropper Stirrer Pipette Distilled water

8. Procedure: First prepared the Molisch’s reagent by adding α- naphthol in 10% alcoholic solution. Take 2ml of given sample solution in a clean test tube. Add 2-3 drops of Molisch reagent slowly. Now add 2 ml concentrated sulfuric acid along the sides of the test tube .

9. Take sample of sugar solution Add Molisch’s reagent Add conc.H2SO4 Formation of violet ring

10. Observations: Test Glucose Lactose Sucrose Starch Molisch’s test Purple ring Purple ring Purple ring Purple ring

11. Results The given organic compound is a reducing sugar . If there is formation of violet ring then the presence of carbohydrate is confirmed.