Osazone

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Osazones are a class of carbohydrate derivatives found in organic chemistry formed when sugars are reacted with phenylhydrazine. The famous German chemist Emil Fischer developed and used the reaction to identify sugars whose stereochemistry differed by only one chiral carbon. The reaction involves formation of a pair of phenylhydrazone functionalities, concomitant with the oxidation of the hydroxymethylene group adjacent to the formyl center. The reaction can be used to identify monosaccharides. It involves two reactions.Firstly glucose with phenylhydrazine gives us glucosephenylhyrdazone by elimination of a water molecule from the functional group.The next step involves reaction of one mole of [[glucosephenylhydrazone with two moles of phenylhydrazine (excess).First phenylhydrazine is invloved in oxidising the alpha carbon to an carbonly group , and the second phenylhydrazine involves in removal of one water molecule with the formyl group of that oxidised carbon and forming the similar carbon nitrogen bond .The Alpha carbon is attacked here because its more reactive than the others.They are highly coloured and crystalline compounds and can be easily detected.