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