Osazones formazans from

Since they contain no active methine groups, - the fcetose phenyl-hydrazones do not yield formazans this lack of reaction is therefore suitable for distinguishing ketoses from aldoses. It is more specific than the osazone test, frequently used in the identification of sugars, for it yields a different formazan from each aldose, whereas the osazone test does not differentiate between epimers. 

The name phenylosazone formazan is suggested for this group of compounds, of which a few simple representatives have been known for some time, such as those where R = CH3 or R = CO2H however, these were not made from osazones, but by treatment of the corresponding a-keto-formazans with phenylhydrazine (as shown in the lower left of the above equation). For example, pyruvaldehyde phenylosazone formazan (C-acetyl-A, A -diphenylformazan phenylhydrazone) was prepared by Bamberger and Lorenzen as early as 1892 by condensation of acetyl-formazan with phenylhydrazine. The violet or brownish-black color characteristic of all known compounds of this group can be attributed to the three chromophoric groups present in the structure. 

The fact that the formazan is formed ehminates structures XVII, XVIII, and XXI, which do not meet the conditions for this reaction. This fimiishes dired evidence in place of the indirect evidence on which Hardegger and Schreier had discarded structures XVIII and XXI. The bicyclic structure XIX, and XX, proposed by Percival" can be dismissed on comparison of the ultraviolet spectra. This compound, after coupling, should contain the two chromophoric groups of the simple formazans, whereas osazone formazans contain three of them. Anhydro- D-glucose phenylosazone formazan and its diacetate display practically the same maxima (maxima at 335 and 405 ran and 340 and 405 m/x, respectively) as does the indisputably-acyclic pyruvaldehyde phenylosazone formazan (maxima at 335 and 410 m/t), and these peaks differ substantially from the values for the simple sugar for-... 

The bishydrazones of the 1,2-diketones from inositols have also been converted into triazoles.222,223 The conversion of arylosazones into the corresponding osotriazoles requires the presence of an oxidant, and it is obvious that simple removal of aniline from the osazone, as suggested by the equation, is not involved. In addition to copper(II) sulfate, the reagent most commonly used, other oxidizing heavy-metal salts, such as ferric sulfate and chloride,224 and mercuric acetate,223 have been used, as well as halogens225 and nitro-sulfonates.226 The osazone acetates are converted into osotriazoles by nitrous acid,227 which decomposes the unacetylated osazones to the aldosuloses228 and the osazone formazans are cyclized with warm... 

Sucrose likewise yields glucosazone identifiable as glucosazone formazan. This indicates that in sucrose it is the hydroxyl group on the first carbon atom of n-fructose which oxidizes to an aldehyde group. As has been observed by several authors (1, 7, 14), in the course of the formation of osazone the disaccharide bond 2, S) breaks up and glucosazone forms from both components of the disaccharide upon the addition of phenylhy drazine. 

Reaction of the n-glucose phenylosazone remaining, in samples taken from the mutarotating solution after increasing periods of time, with diazo solution, yields less and less osazone formazan (see Fig. 16). This is obviously attributable to the same structrual change as that which is optically... 

Hexosulose hydrazones and the mixed osazones react with diazotized aniline to give formazans, and with hydrogen peroxide to give pentonic acids. Unlike the mixed osazones obtained by transhydrazonation, the derivatives obtained from the glycosulose hydrazones are pure, uncontaminated compounds, and the positions of their hydrazone residues are well established. Thus, they afford remarkable possibilities, not only in the preparation of new types of compound, but also in enabling the reaction of osazones to be followed more closely, as in the case of triazole formation," and in studying the structure of anhydro-osazones. ... 

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