Osazone

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Class of chemical compounds

title: "Osazone" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["carbohydrates", "hydrazones", "emil-fischer"] description: "Class of chemical compounds" topic_path: "general/carbohydrates" source: "https://en.wikipedia.org/wiki/Osazone" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Class of chemical compounds ::

::figure[src="https://upload.wikimedia.org/wikipedia/commons/b/b9/D-glucose-osazone-3D-balls.png" caption="[[Ball-and-stick model]] of glucosazone"] ::

Osazone are a class of carbohydrate derivatives found in organic chemistry formed when reducing sugars are reacted with excess of phenylhydrazine at boiling temperatures.

Formation

Osazone formation was developed by Emil Fischer, who used the reaction as a test to identify monosaccharides.

The formation of a pair of hydrazone functionalities involves both oxidation and condensation reactions. Since the reaction requires a free carbonyl group, only "reducing sugars" participate. Sucrose, which is nonreducing, does not form an osazone.

:[[Image:Osazone-Formation.png|none|thumb|400px|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]].]]

:[[Image:Osazone.svg|none|thumb|600px|General steps in osazone formation]]

Appearance

Osazones are highly coloured and crystalline compounds. Osazones are readily distinguished.

  • 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

References

References

  1. (2000). "Hydrazine derivatives of carbohydrates and related compounds". Advances in Carbohydrate Chemistry and Biochemistry.
  2. (1970). "Structure of saccharide osazones". Journal of the Chemical Society C: Organic.
  3. (1953). "Emil Fischer zum 100. Geburtstag". Angewandte Chemie.
  4. (2004). "Textbook of Medical Biochemistry". Orient Blackswan.
  5. Gupta, Anil. (2019). "Comprehensive Biochemistry for Dentistry". Springer.

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carbohydrateshydrazonesemil-fischer