Chemical Constituents of the Animal Body. 203 



CHO CH 2 (OH) 



(CH(OH)) 4 into (CH(OH)) 4 



CH 2 (OH) CHO 



In the preceding section it has been stated that sugars 

 can be converted by oxidation into monobasic acids (for 

 example, gluconic and mannonic acids). This reaction can 

 be brought about by means of bromine water. If a more 

 powerful oxidizing reagent, such as nitric acid, is employed, 

 the sugar can be converted into a dibasic acid. In this 

 way saccharic acid can be formed from glucose. Saccharic, 

 like gluconic acid, also forms a lactone, which on reduction 

 yields an aldehyde acid (glycuronic acid). The latter, on 

 further reduction, yields a new acid by the conversion of 

 the CHO group into the CH 2 OH group. This acid 

 also forms a lactone, which on reduction yields a sugar. 

 This series of reactions is represented by the following 

 formulae : 

 CHO _ ^COOH _ ^CHO _ ^CH 2 OH __ ^CH a OH 



(CH(OH)) 4 [oxi-(CH(OH)) 4 N- (CH(OH)) 4 [re- (kll(OH)h [" (CH(OH)) 4 



da- | due- | due- I due- 



CH 2 (OH) tionJcoOH tion] COOH tion]cOOH *i 



Glucose Sa - ric ^curonic Gulonio Guloge 



Throughout this series of reactions the relative positions 

 of the hydrogen atoms and hydroxyl groups on the four 

 asymmetric carbon atoms remain unchanged. Sugars 

 related to one another in the way that glucose is related 

 to gulose can only differ in the relative positions of the 

 CHO and CH 2 OH groups. It is easy to see that 

 they will yield the same dibasic acid (in the example cited 

 saccharic acid) on oxidation. 



III. It is possible to pass from one sugar to another 

 containing an additional carbon atom for example, from 

 a pentose to a hexose. On treatment with hydrocyanic 



