Maltose_050223.pptx

Structure of Maltose

1. Maltose It is a colorless crystalline solid , soluble in water but insoluble in ether It is a reducing sugar & reduces Tollen’s reagent and Fehling solution On hydrolysis , it gives two molecules of glucose Structure of Maltose The molecular formula is found to be C 12 H 22 O 11 It is a reducing sugar: It reduces Tollen’s reagent and Fehling solution It forms an osazone with phenyl hydrazine On hydrolysis, it forms two molecules of glucose. This suggest that maltose is made up of two glucose unit Dr. Dhananjaya Sahoo

2. On oxidation with bromine water , maltobionic acid is formed, suggesting the presence of an aldehyde group in the reactive hemiacetal form, in one of the two glucose unit present Br 2 /H 2 O C 12 H 22 O 11 (C 11 H 21 O 10 )COOH Maltose maltobionic acid Dr. Dhananjaya Sahoo

3. Maltobionic acid on complete methylation with (Me) 2 SO 4 and NaOH followed by hydrolysis gives a mixture of 2,3,4,6-tetra-O-methyl D-glucose and 2,3,5,6-tetra-O-methyl-D-gluconic acid Dr. Dhananjaya Sahoo

4. The presence of free –OH group at C-4 in 2,3,5,6-tetra-O-methyl-D-gluconic acid shows that this position was not available for methylation at maltobionic acid. The presence of free –OH at C-1 in 2,3,4,6-tetra-O-methyl D-glucose suggests that this position was not available for methylation at maltobionic acid stage Thus C-1 is involved in maltobionic acid or maltose itself 2,3,4,6-tetra-O-methyl D-glucose must be due to the non-reducing part of the maltose Thus C-4 is involved in maltobionic acid or maltose itself Dr. Dhananjaya Sahoo

5. The presence of free –OH group at C-4 in 2,3,5,6-tetra-O-methyl-D-gluconic acid shows that this position was not available for methylation at maltobionic acid. The presence of free –OH at C-1 in 2,3,4,6-tetra-O-methyl D-glucose suggests that this position was not available for methylation at maltobionic acid stage Thus C-1 is involved in maltobionic acid or maltose itself 2,3,4,6-tetra-O-methyl D-glucose must be due to the non-reducing part of the maltose Thus C-4 is involved in maltobionic acid or maltose itself Dr. Dhananjaya Sahoo

6. The enzyme maltase specifically hydrolyzes a -glucopyranosides to a -glucose Harowth projection formula of D-Glucose Dr. Dhananjaya Sahoo The enzyme maltase specifically used for the hydrolysis of a -glycosidic linkage. hydrolyzes maltose, suggesting the -OH group at C-1 of the non-reducing glucose is alpha form

7. Harowth projection formula of Maltose Dr. Dhananjaya Sahoo Thus the –OH group on –C-1 of non-reducing glucose unit is attached with the –OH of the C-4 of the reducing sugar

8. Harowth projection formula of Maltose Dr. Dhananjaya Sahoo

9. a - and b - form maltose differ in their configuration only at the anomeric center Dr. Dhananjaya Sahoo