17. Osazone formation involves hydrazone formation at
C-1 of an aldose (or C-2 of a ketose) and oxidation of
C-2 (or C-1) of an alcohol group to a ketone (or an
aldehyde). The new carbonyl group is also converted to
a hydrazone.
Fructose Mannose Glucose
18. Osazone crystals have a characteristic shape under the light
microscope and help in the identification of the sugar type.
Disaccharides - like Lactose - like tight balls Monosaccharides - like
sunflowers of needles needle-shaped or
broomstick
19. Making Osazone Crystals
The difference in the structure of the monosaccharides
is caused by the diverse groups attached to the first
and second carbons of the sugar molecules. Their
needle-shaped crystals show that the position of the
first and second carbons do not matter in the crystal
formation.
26. Time to Form
The time needed to create osazone crystals varies
among the various sugars involved, but helps to
identify the sugars being tested. For an osazone crystal
to be presented from a hot solution will take as long as
follows:
fructose, two minutes; Actual Time:
glucose, four to five minutes; Xylose – 20 mins
xylose, seven minutes; Galactose – 25 mins
galactose, 15-19 minutes; Glucose – 30 mins
maltose, osazone soluble in hot Sucrose – 47 mins
water Fructose – 57 mins
Maltose – 59 mins