Osazones effect

Hydrolysis of the diacetamides is effected by acids. Dilute hydrochloric, sulfuric and nitric acid have been used. An aldose with one carbon atom less than the original nitrile is then liberated from the combination. Only exceptionally can this aldose be isolated in pure condition without transforming it into an insoluble derivative in these instances, the method has been employed for preparative work. In most cases the sugar has been characterized as an osazone. The aldose, without great purification, has been employed successfully for reduction - or oxidation experiments. ... 

Scheme B requires exchange of the H-l with the medium, whereas Scheme A does not. Despite a report5 that stated that there was no loss of tritium from D-glucose-i-f on osazone formation, it seems that about 15% of the hydrogen on C-l does undergo exchange. Such an exchange is consistent with the operation of mechanism B, with a large isotope-effect, but does not preclude the simultaneous operation of mechanism A.

An outstanding contribution to osazone chemistry was made by Hann and Hudson"" who examined the effect of boiling osazones with... 

Diels, Meyer and Onnen studied the effect of boiling alcoholic solutions of osazones with potassium hydroxide (1%). n-Glucose phenylosazone gave glyoxal phenylosazone and l,2-bis(phenylazo) ethylene, and in general, glyoxal phenylosazone was obtained in the other cases examined, except for cellobiose phenylosazone. Evidently fission takes... 

The presence of stable chelated rings in osazones is also evident from the slowing down, and sometime inhibition, of certain reactions. Thus, the for-mazan reaction223 requires potassium hydroxide to break the chelated ring of osazones and to effect coupling with the diazonium ion.319,320 Similarly, the formation of polyhydrazones is inhibited by chelation accross the C-l... 

Hill (1898) showed the reversal of hydrolysis with a maltase extracted from a brewer s yeast. He dried the organism to a powder, which he then heated to 100 °C while dry. The maltase was finally extracted from the yeast with 10 volumes of 0.1% (w/v) sodium hydroxide. The extract, which was neutral to litmus, not only hydrolysed maltose [a-o-Glc-(l - 4)-Glc (9)] to glucose, but also would synthesize a product from glucose which Hill believed, on the basis of a careful analytical study of the osazone, to be maltose. At a total sugar concentration of 40% (w/v) the reaction would approach its equilibrium position from either side (Table 1.4, Figure 1.2), and the synthesis was less effective at lower concentrations. Emmerling... 

Thin-layer chromatography of the osazones can be effected on a variety of adsorbents. Tore [63] reported the chromatography of the phenylosazones on unbound Silene E. F. plates (activated at 110° for 24 hours) with solvent systems containing mixtures of chloroform, acetone, ethanol and water (solvents XXXII and XXXIII). The hRf values increase rapidly with an increase in the water content of the solvent as shown in Table 211. 

Certain reactions t)7pical of aldoses are less easily applicable to the uronic acids because of the modifying effect of the carboxylic group. The important nitrogen derivatives, including osazones, hydrazones and arylglycosylamines are less satisfactory for the characterisation of uronic acids. Such derivatives are apparently a mixture of the desired product with the corresponding amine salt or amide. 

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