1. 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.

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-gluconic acid. Glucose is a reducing sugar.

3. Oxidation of Monosaccharides
aldonic acid
gluconic a.
CH2OH C O HO =
CH2OH C O H =
COOH
COOH C O H =
aldaric acid
glucaric a. Z
monosaccharide
D-glucose
alduronic acid
glucuronic a. 3 11

4. Disaccharides

5. Disaccharides
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.

6. Disaccharides Formed from two monosaccharides
Joined by a glycosidic bond
A condensation reaction:
glucose + glucose  maltose
glucose + galactose  lactose
glucose + fructose  sucrose

7. Condensation reactionOH

8. Condensation reactionOH

9. Condensation reaction
H2O

10. Condensation reaction4 1
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 b-D-(-)-Fructofuranose cis = b up = D .. : anomeric carbon ..
standard position
cis = b
up = D 1 .. : 2
anomeric
carbon 6 3 5 2 4 .. 4 3 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

16. Maltose
A disaccharide in which two -D-glucose molecules are joined by an -1,4-glycosidic bond.
Malt Sugar

17. - D-Maltose 
 -1,4-glycosidic bond

18. Lactose
Composed of -galactose and -glucose linked by a -1,4-glycosidic bond.
Milk Sugar

19. α-D-Lactose 
 -1,4-glycosidic bond

20. Sucrose
Composed of glucose and fructose molecules joined by ,-1,2-glycosidic bond.
Has no isomers because mutarotation is blocked.
Table Sugar

21. Sucrose
α, -1,2-glycosidic bond

22. Disaccharide Synthesis
Energy +

23. Disaccharide Hydrolysis
Disaccharide hydrolyzed to its corresponding of monosaccharides.
Maltose + H2O Glucose + Glucose
Lactose + H2O Glucose + Galactose
Sucrose + H2O Glucose + Fructose