Glucose reaction with phenylhydrazine

Simple sugars undergo reaction with phenylhydrazine, PhNHNH2, to yield crystalline derivatives called osazones. The reaction is a bit complex, however, as shown by the fact that glucose and fructose yield the same osazone. 

Reducing sugars can be detected by reaction with phenylhydrazine to yield a hydrazone product, except the result of the reaction is not what one might imagine giving the structure of aldoses and ketoses. Glucose, for example, can react with phenylhydrazine to yield the anticipated... 

He isolated a product, from the reaction of oWe/it/do-D-glucose pentaacetate with phenylhydrazine, which posed a problem in structure not solved until the technique of nuclear magnetic resonance became available, thirty years later. 

Many 1-phenylflavazoles derived from sugars have been characterized by chromatographic Rf values " and by x-ray diffraction patterns. " Most syntheses of pyrazolo[3,4-b]quinoxalines involve polyhydroxy-alkylquinoxalines as intermediates and, by reaction with phenylhydrazine, result in the formation of 1-phenyl substituted derivatives of the ring system. Thus the o-arabotetrahydroxybutyl compound 6, obtained from reaction of o-glucose with o-phenylenediamine, reacts with three moles... 

Historically, techniques such as the formation of osazones and the demonstration of fermentation have contributed significantly to the separation and identification of carbohydrates. Observation of the characteristic crystalline structure and melting point of the osazone derivative, prepared by reaction of the monosaccharide with phenylhydrazine, was used in identification. This method is not completely specific, however, because the reaction involves both carbon atoms 1 and 2 with the result that the three hexoses, glucose, fructose and mannose (Figure 9.19), will yield identical osazones owing to their common enediol form. 

A hexose, C6H1206, which we shall call X-ose, on reduction with sodium amalgam gives pure D-sorbitol, and upon treatment with phenylhydrazine gives an osazone different from that of D-glucose. Write a projection formula for X-ose and equations for its reactions. 

The reaction of phenylhydrazine, and particularly substituted phenylhydrazines, with the carbonyl group of sugars is extensively utilized in their identification. The derivatives are called osazones if two molecules of phenylhydrazine add to one molecule of sugar, as in the case of glucose, and phenylhydrazones when one molecule... 

Elimination of acetic acid occurs readily from phenylhydrazones of acetylated aldoses. For example, the reaction between 2,3,4,5,6-penta-O-acetyl-aZde%do-D-glucose and phenylhydrazine gives the unsaturated phenylhydrazone, 3,4,5,6-tetra-O-acetyl-l, 2-dideoxy-l -phenylazo-n-ara-6mo-hex-l-enitol (137), which may also be prepared by acetylation of the acyclic phenylhydrazones of n-glucose and D-mannose, or by condensation of 2,3,4,5,6-penta-0-acetyl-aZdeA /do-D-mannose with phenylhydrazine. 2,3,4,5,6-Penta-O-acetyl-D-glucose phenylhydrazone (138) has been... 

An interesting intermediate, possibly deriving from Weygand s Scheme B, was isolated by Haas and Seeliger from the reaction of u-glucose with phenylhydrazine in acetic acid or hydrochloric acid. This product is 3-(D-fflrol)fno-tetrahydroxybutyl)cinoline (30), produced, not by the hydrolytic decomposition of the osazone, but by the cyclization of the intermediate glycosulose 2-(phenylhydrazone) (28) or the aldimine 2-(phen-ylhydrazone) (29). 

Although D-fructose is not an epimer of D-glucose or D-mannose (D-fructose is a ketohex-ose), all three yield the same phenylosazone. (a) Using Fischer projection formulas, write an equation for the reaction of fructose with phenylhydrazine. (b) What information about the stereochenfistry of D-fructose does this experiment yield ... 

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