carbohydrate ppt 27.06.2021.pptx

carbohydrate

1. Reactions of Monosaccharides and Disaccharides Seetaram Mohapatra

2. Kiliani -Fischer Synthesis : It is a method for extending a carbohydrate chain by a single carbon. It involves addition of cyanide ion to an open chain aldehyde which is then partially reduced and then hydrolyzed to give a new aldehyde. In the absence of chiral reagents, a mixture of diasteromers will be produced.

3. Kiliani -Fischer Synthesis: It is a method for extending a carbohydrate chain by a single carbon. It involves addition of cyanide ion to an open chain aldehyde which is then partially reduced and then hydrolysed to give a new aldehyde . In the absence of chiral reagents, a mixture of diasteromers will be produced.

4. Steps involved Kiliani -Fischer Synthesis:

5. Mechanism: Step 1: Step 2:

6. Ruff degradation Reaction: It is a method for shortening a carbohydrate chain by a single carbon. It is a method for performing the reverse reaction.

7. Mechanism:

8. Osazone reaction:

9. Mechanism

10. Examples

11. Mechanism:

12. Molisch’s test is a general test for all carbohydrates. In this test, carbohydrates when reacted with conc. H 2 SO 4 get dehydrated to form furfural and its derivatives. When monosaccharide are treated with conc H 2 SO 4 or conc HCl , -OH group of sugar are removed in the form of water and furfural is formed from pentose sugar and hydroxymethyl furfural is formed from hexose sugar. These products reacts with sulphonated α- naphthol to give a purple (violet red) colored complex. Molisch’s test

13. Mechanism, Molischs Test

14. Reagents for Molisch’s test: test solution: 5 % Glucose, 5 % Sucrose, 5 % Starch, Molisch’s reagent (5 % α naphthol in ethanol). H 2 SO 4 Dry test tubes. pipettes Procedure of Molisch’s test: Take 2ml of sample in dry test tube. Take 2ml of distilled water in another tube as control. Add 2-3 drops of Molisch’s reagent to the solution. Gently pipette 1ml conc. H 2 SO 4 along the side of the tube so that two distinct layers are formed. Observe color change at the junction of two layers. Appearance of purple color indicates the presence of carbohydrates.

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