HYDRAZONES AND OSAZONES. 203 



The reaction takes place with the aldoses as follows: 



(a) CH 2 (OH).[CH(OH)] 3 .CH(OH).CH04-H 2 N.NH.C 6 H 5 = 



CH 2 (OH).[CH(OH)] 3 .CH(OH)CH:N.NH.C 6 H 6 +H 2 0. 



Phenylglucosehydrazone 



(6) CH 2 (OH)[CH(OH)] 3 .CH(OH).CH:N.NH.C 6 H 5 +H 2 N.NH.C 6 H5 = 



CH 2 (OH).[CH(OH)r 3 .C.CH:N.NH.C 6 H 6 



N.NH.C 6 H6+HoO+H 2 . 



Phenylglucosazone 



and with the keteoses : 



CH 2 (OH)[CH(OH)] 3 CO.CH 2 (OH)-fH 2 N.NH.C 6 H5 = 



CH 2 (OH)[CH(OH)] 3 C.CH 2 OH 



N.NH.C 6 H 6 +H 2 0, 

 and CH 2 (OH)[CH(OH)] 3 .C.CH 2 (OH) 



CH 2 (OH)[CH(OH)] 3 .C.CH:N.NH.C 6 H 6 +H 2 O+H 2 . 



N.NH.C 6 H 6 



The hydrogen is not evolved, but acts on a second molecule of phenylhy- 

 drazine and splits it into aniline and ammonia: 



H 2 N.H.C 6 H 6 + H 2 =H 2 N.C 6 H 6 +NH 3 . 



As seen from the above equations the aldoses and ketoses yield the 

 same osazones, while the hydrazones are different. 



The osazones, 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 fum- 

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

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

 more often ketoses. 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 3 r east has been shown only for 



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



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



