Osazone

As osazones is called the phenyl hydrazones of sugars.

History

Emil Fischer discovered in 1874 while working on the diazotization of aniline the phenylhydrazine, it was later used for the characterization of sugars.

Representation

Aldoses form with three equivalents of phenylhydrazine twice hydrazones on - and - atom, so that a chiral center disappears and the identification of possible epimers. The formation of the osazones is represented as follows:

Here is a monosaccharide (1, abbreviated by R ), for example glucose, with phenylhydrazine elimination of water to a phenylhydrazone (2). Is further reacted phenylhydrazine in the reaction, that the dehydration of the carbonyl group adjacent to the alcohol group of the sugar. This produces aniline and ammonia. As an intermediate This produces a Osonhydrazon (3). Finally, a third molecule phenylhydrazine reacts with the carbonyl group, there arises a osazone (4a). This is due to an intramolecular hydrogen bond stabilizes (4b).

However, it is not known why an educated osazone no longer can react with another molecule of phenylhydrazine. When glucose while the hydroxy group would come into question on the C3 atom.

Properties

Osazones are yellow, slightly crystallized substances. After exposure to strong acids or by boiling in benzaldehyde Oson can be displayed from a osazone. Osone are α - keto aldehydes.

Chemical significance

The osazone formation is primarily used for separation and identification or characterization of sugars above the melting point. The epimers of glucose and mannose (both aldoses ) and fructose ( a ketose ) give the same osazone in the implementation.

Credentials

  • Substance Group
  • Hydrazine
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