Osazone
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Osazone are a class of carbohydrate derivatives found in organic chemistry formed when reducing sugars are reacted with excess of phenylhydrazine at boiling temperatures.[1][2]
Formation
Osazone formation was developed by Emil Fischer,[3] who used the reaction as a test to identify monosaccharides.
The formation of a pair of hydrazone functionalities involves both oxidation and condensation reactions.[4] Since the reaction requires a free carbonyl group, only "reducing sugars" participate. Sucrose, which is nonreducing, does not form an osazone.
File:Osazone-Formation.png A typical reaction showing the formation of an osazone. D-glucose reacts with phenylhydrazine to give glucosazone. The same product is obtained from fructose and mannose.
File:Osazone.svg General steps in osazone formation
Appearance
Osazones are highly coloured and crystalline compounds. Osazones are readily distinguished.[5]
- Maltosazone (from maltose) forms petal-shaped crystals.
- Lactosazone (from lactose) forms powder puff-shaped crystals.
- Galactosazone (from galactose) forms rhombic-plate shaped crystals.
- Glucosazone (from glucose, fructose or mannose) forms broomstick or needle-shaped crystals.
Historic references
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References
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