28 



LECTURE II. 



From mannose, the monobasic mannonic acid and then the dibasic 

 manno-saccharic acid. 



From galactose the monobasic galactonic acid and then the dibasic 

 mucic acid. 



Fructose behaves quite differently on oxidation. In the case of the 

 above-mentioned sugars, which are all aldoses, acids are obtained by 

 oxidation having the same number of carbon atoms as the original sugars. 

 Fructose, on the other hand, is a ketone, and on being oxidized breaks down 

 into compounds containing a smaller number of carbon atoms. 



These reactions are naturally not peculiar to hexoses, and for the simpler 

 or higher monosaccharides there are corresponding alcohols as well as 

 monobasic and dibasic acids. Thus we have for example: 



Bioses : 



Trioses : 



Alcohol 

 CH 2 OH 



CH 2 OH 

 Glycol 



CH 2 OH 



HOH 



H 2 OH 

 Glycerol 



Tetroses : 



Sugar Monobasic Acid Dibasic Acid 



CHO CO .OH CO . OH 



I I I 



CH 2 OH CH 2 OH CO . OH 



Glycolose Glycollic Acid Oxalic Acid 

 (Glycolaldehyde) 



COOH 

 CHOH 

 CHOH 



COOH 



Tartaric 

 Acids (4) 



Erythritol was discovered by Lamy (1852) in the algae Protococcus 

 vulgaris. It is optically inactive. 



In the group of the pentoses, it has already been stated that arabinose 

 corresponds to the alcohol arabitol and the two acids, arabonic and 1-trioxy- 

 glutaric, while with xylose we have the alcohol xylitol and two correspond- 

 ing acids. Although these last alcohols and acids have up to the present 



