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Reduction of Monosaccharides

REACTIONS OF MONOSACCHARIDES. Reduction of Monosaccharides. The reduction of the carbonyl group produces sugar alcohols, or alditols. D-Glucose is reduced to D-glucitol also called sorbitol . Oxidation of Monosaccharides.

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Reduction of Monosaccharides

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  1. REACTIONS OF MONOSACCHARIDES Reduction of Monosaccharides The reduction of the carbonyl group produces sugar alcohols, or alditols. D-Glucose is reduced to D-glucitol also called sorbitol.
  2. Oxidation of Monosaccharides Monosaccharides are reducing sugars if their carbonyl groups oxidize to give carboxylic acids. Benedict’s reagent (CuSO4) can oxidize aldehydes with adjacent hydroxyl groups The blue Cu2+ ions in the Benedict’s reagent are reduced to form a brick-red precipitate, Cu2O In the Benedict’s test, D-glucose is oxidized to D-gluconicacid. Glucose is a reducing sugar.
  3. O HO = aldonic acid COOH C gluconic a. O O H H = = COOH CH2OH C C CH2OH COOH aldaric acid monosaccharide glucaric a. D-glucose alduronic acid glucuronic a. Oxidation of Monosaccharides
  4. Disaccharides
  5. A disaccharide is formed when a hydroxyl group on one monosaccharide reacts with the anomeric carbon (C-1) of another monosaccharide to form a glycosidic bond Links may be α or β 1-4’ link: The anomeric carbon is bonded to oxygen on C4 of second sugar. 1-2’ link: The anomeric carbons of the two sugars are bonded through an oxygen. The free anomeric carbon is called reducing end According to the position of the linkage between the sugar units, disaccharides are classified into non-reducing such as sucrose and reducing such as maltose and lactose. Disaccharides
  6. Disaccharides Formed from two monosaccharides Joined by a glycosidic bond A condensation reaction: glucose + glucose  maltose glucose + galactose  lactose glucose + fructose  sucrose
  7. C C C C O O C C C C C C C C Condensation reaction OH OH
  8. C C C C O O C C C C C C C C Condensation reaction OH OH
  9. C C C C O O C C C C C C C C Condensation reaction O H2O
  10. C C C C O O C C C C C C C C Condensation reaction 1 4 O A disaccharide 1,4 glycosidic bond
  11.  &  Isomerism OH   OH
  12.  and  Anomers for D-Glucose The new –OH on C1 is drawn down for the anomer, and up for the  anomer.   -D-Glucose -D-Glucose
  13. FRUCTOSE standard position cis = b up = D 1 .. : anomeric carbon 2 6 3 5 2 .. 4 3 4 1 .. 5 6 b-D-(-)-Fructofuranose D-(-)-Fructose
  14. Cyclic Structure of Fructose As a ketohexose, fructose forms a cyclic structure when the —OH on C-5 reacts with the C=O on C-2. -D-Fructose -D-Fructose
  15. Maltose A disaccharide in which two -D-glucose molecules are joined by an -1,4-glycosidic bond. Malt Sugar
  16. - D-Maltose   -1,4-glycosidic bond
  17. Lactose Composed of -galactoseand -glucose linked by a -1,4-glycosidic bond. Milk Sugar
  18. α-D-Lactose   -1,4-glycosidic bond
  19. Sucrose Composed of glucose and fructose molecules joined by ,-1,2-glycosidic bond. Has no isomers because mutarotationis blocked. Table Sugar
  20. Sucrose α, -1,2-glycosidic bond
  21. Disaccharide Synthesis Energy +
  22. Disaccharide Hydrolysis Disaccharide hydrolyzed to its corresponding of monosaccharides. Maltose + H2O Glucose + Glucose Lactose + H2O Glucose + Galactose Sucrose + H2O Glucose + Fructose
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