THE CHEMISTRY OF THE SUGARS 87 



nature and which have a practical as well as a scientific import- 

 ance, and it is unnecessary, therefore, to extend it further. 



All these aldoses and ketoses have certain general reactions 

 by which they can be readily identified : 



1. They are readily reduced by nascent hydrogen to the 

 corresponding alcohols, the aldehyde and ketone group being 

 attacked, thus : 



CH 2 OH CE^OH CILjOH 



I I 



= (CHOH) 4 (CHOH) 3 (CHOH) S 



I I | +H,= | 



CHO CH 2 OH CO CHOH 



I I 



CH 2 OH CH 2 OH 



2. Dilute nitric acid oxidises aldoses to oxycarboxylic acids, 

 thus : 



CH 2 OH(CHOH) 4 CHO + = CH 2 OH(CHOH) 4 C0 2 H 



With ketoses the chain is broken on oxidation : 



CH 2 OH(CHOH) 3 COCH 2 OH + 30 = 



C0 2 H(CHOH) 2 C0 2 H + C0 2 HCH 2 OH 



Tartario acid Glycollic add 



3. Phenyl-hydrazine converts both aldoses and ketoses into 

 hydrazones and finally into osazones by the following impor- 

 tant reactions : 



Aldose 

 i. - 



Aldose group Phenyl-hydrazine 



= -CHOHCH=N-NHC 6 H 5 + H 2 



Hydrazone 



u, CHOHCH=N-NHC 6 H 5 + C 6 H 5 NHNH 2 



= -COCH=N-NHC 6 H 5 + C 6 H 5 NH 2 -f 



Carbonyl compound 



