THE CARBOHYDRATES AND THEIR METABOLISM 215 



C H 



HCO.OC CII 3 



I 

 HCO.OC CH 3 



HCO.OC CH 3 



I 

 HCO.OC CH 3 



HCO.OC CH 3 

 II 



That is, glucose behaves like a compound having five alcohol (OH) groups 

 here, and Berthelot, who first prepared the acetates of glucose, called the 

 sugar a pentatomic aldehyde alcohol. When acted upon by metallic 

 hydroxides, glucose forms compounds resembling alcoholates, further dem- 

 onstrating the presence of alcohol groupings. 



Glucose is reduced by sodium amalgam to form a hexahydric alcohol, 

 which in turn may be reduced by hydriodic acid to iodohexane, a derivative 

 of normal hexane, which indicates that glucose is a normal chain com- 



(COOH). Acids and alcohols react forming ethereal salts or esters, much as acids 

 and bases react to form salts, thus: 



CH 3 OH -f CH 3 COOH ^ CH 3 COOCH 3 



methyl alcohol acetic acid methyl acetate (ester) 



// * 



Substances having the group C are called aldehydes, and those that contain 



I H 



the carbonyl group CO are known as ketones. A fundamental distinction between alde- 

 hydes and ketones, is that when they are oxydized, aldehydes yield acids containing the 

 same number of carbon atoms as the original substance while ketones break up on oxi- 

 dation, yielding products which do not contain as many carbon atoms as the original 

 substances. Thus: 



O 

 CH,CH 2 C -f _ CH 3 CH 2 COOH 



H 



propyl aldehyde propionic acid 



CH, 



CO -f 3 O _ CH 3 COOH -f HCOOH 



CH 3 



methyl ketone acetic and formic acids 



(acetone> 



