THE CARBOHYDRATES AXD THEIR METABOLISM 233 



while the phenylhydrazine is converted to anilin and ammonia. The car- 

 bonyl group then reacts with another molecule of phenylhydrazine to 

 form the osazone, thus : 



[ 5 CHiX.XH C 6 H 5 



I 

 CO 



CH:N.XH 



HCOH 



I 

 1IOCH 



CHXH.XH 



HCOH 



HCOH 



I 

 CH 2 OH 



65 



HOCH 

 HCOH 



HCOH 



I 

 CHoOH 



C G H 5 XH 2 +XIL 



Plienylhydrazone + phenylhydra- intennediary -f- aniliu + ammonia 



zine oxidation 

 product 



CH :X . XH C 6 H 5 CH :X . XH C ft H 5 



I I 



CO C:X.XH C 6 H 5 



I I 



HOCH HOCH 



| + C 6 H 5 XH.XH 2 | + H 2 



HCOH > HCOH 



HCOH 



CH 2 OH 



phenylosazone 



HCOH 



CHoOH 



Intermediary oxida- + phenylhydra- phenylosazone + water 

 tion product zine 



Because the second stage of the reaction is a process of oxidation, it 

 follows that those sugars that are most easily oxidized (as d-fructose) most 

 readily form osazones. 



Aldoses and ketoses may be differentiated by means of their reaction 

 with methyl phenylhydrazine. According to Xewberg, ketoses form, osa- 

 zones, while aldoses reach only the hydrazone stage. The asymmetrically 

 substituted hydrazines do not act as oxidizing agents. Since the conversion 

 of hydrazone to osazone involves oxidation, the reason for this behavior 

 is evident. 



Most of the hydrazones are very soluble in water and therefore not 

 adapted for identification. Mannose, however, is a notable exception. 

 It forms a crystalline precipitate easily identifiable. The osazones are, 

 as a rule, quite insoluble in water. In order to form more specific com- 



