Maltose is a reducing sugar that is soluble in water but insoluble in ether. It reduces Tollen's reagent and Fehling's solution. Upon hydrolysis, maltose yields two molecules of glucose. Maltose is composed of two glucose units linked via an alpha-1,4-glycosidic bond between the anomeric carbon of one glucose and the C4 hydroxyl of the other. Oxidation of maltose forms maltobionic acid, indicating the presence of an aldehyde group in one of the glucose units. Complete methylation and hydrolysis of maltobionic acid produces 2,3,4,6-tetra-O-methyl-D-glucose

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 C12H22O11
• 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
Br2/H2O
C12H22O11 (C11H21O10)COOH
Maltose maltobionic acid
Dr. Dhananjaya Sahoo

3. Maltobionic acid on complete methylation with (Me)2SO4 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