OSAZONES 199 



For the isolation of the -sugars we often make use of the hydrazones 

 as well as the osazones obtained by the aid of substituted phenyl hydra- 

 zines instead of the phenyl hydrazine, because they yield difficultly soluble 

 compounds. As seen from the above equations the aldoses and ketoses 

 yield the same osazones, while the hydrazones are different. 



The osazjones, which are more important than the hydrazones, are 

 generally yellow crystalline compounds which differ from each other in 

 melting-point, solubility, and optical properties, and hence have been of 

 great importance in the characterization of certain sugars. They have 

 also become of extraordinarily great interest in the study of the carbo- 

 hydrates for other reasons. Thus they are a very good means of pre- 

 cipitating sugars from solution in which they occur mixed with other 

 bodies, and they are of the greatest importance in the artificial prepara- 

 tion of sugars. On cleavage, by the brief action of gentle heat and fuming 

 hydrochloric acid (for disaccharides still better with benzaldehyde), 1 

 the osazones yield so-called osones, Which on reduction yield aldoses or 

 more often ketoses. ' 



We can also pass from the osazones to the corresponding sugars in 

 other, indirect, ways. The hydrazones can be much more readily retrans- 

 formed into the corresponding sugar, especially by decomposition with 

 benzaldehyde (HERZFELD) or with formaldehyde (RUFF and OLLEN- 

 DORFF 2 ), whereby the sugar is replaced by the aldehyde used. 



An important property, although not applicable to all sugars, is their 

 ability to undergo fermentation, especially their ability to undergo 

 alcoholic fermentation with alcohol-yeast. We must state, however, 

 that the power of fermentation with pure yeast has been shown only for 

 the hexose group, and in fact all of the hexoses do not ferment, and they 

 do not all ferment with the same readiness. d-Glucose and d-mannose 

 ferment readily, but d-galactose only with difficulty. The /-forms of 

 the above-mentioned sugars do not ferment, and from the racemic forms 

 of these sugars the optical Z-antipode can be prepared by the fermenta- 

 tion of the d-sugar. Among the ketoses the d-levulose ferments while 

 the sorbose does not. Among the sugars containing nine atoms of carbon, 

 the nonoses, the mannonose does not ferment while the glucononose does. 

 The different behavior of the various sugars with yeast stands in fixed 

 relation to their configuration, and is not only of great importance for 

 the behavior of the sugar in lower organisms, but also for their behavior 

 in higher developed organisms. Thus the investigations of NEUBERG and 

 WOHLGEMUTH 3 upon arabinose and of NEUBERG and MAYER 4 on man- 



1 E. Fischer and Armstrong, Ber. d. d. chem. Gesellsch., 35. 



2 Herzfeld, ibid., 28; Ruff and Ollendorff, ibid., 32. 



3 Zeitschr. f. physiol. Chem., 35. 4 Ibid., 37. 



