SUGAR 415 



Emil Fischer. Not only have many of the natural carbohydrates 

 been made by synthetical laboratory processes, but a large 

 number of purely artificial sugars have been built up which have 

 no existence in nature, or at any rate have not hitherto been 

 discovered. The constitutional formula for common sugar, 

 which harmonises with its synthesis, has been represented as 

 shown in the diagram on the opposite page. 



This looks rather formidable, but a glance will show that it is 

 essentially made up of two chains each consisting of six atoms 

 of carbon, with which are associated four hydroxyl groups, HO, 

 and associated together by the agency of an atom of oxygen 

 which links them together. 



Before proceeding to enquire how this has been determined it 

 may be of interest to examine why sugar possesses a sweet taste 

 and is so soluble in water. This appears to be connected with 

 the presence of the numerous hydroxyl groups attached directly 

 to carbon atoms, which also are linked to one or two atoms of 

 hydrogen. Many compounds having a more or less sweet taste 

 and ready solubility are thus constituted. They are possessed 

 of the chemical characters exhibited by common ethyl-alcohol 

 CH 3 -CH 2 OH, though not its intoxicating properties. Thus : 



Ethylene-alcohol or glycol HO-CH 2 -CH 2 -OH. 

 Propylene glycol CHo-CH-OH-CH 2 -OH. 

 Glycerine or glycerol CH 2 -OH-CH-OH-CH 2 -OH. 

 Mannite or Mannitol 



CH 2 -OH-CH-OH-CH-OH-CH-OH-CH-OHCH 2 -OH. 



All these substances have a decided sweet taste, though 

 inferior to that of common sugar, and it will be found when the 

 constitution of some of the other sugars is explained that they 

 also contain an abundance of this constituent, hydroxyl, HO. 

 It will be observed, however, that when hydroxyl is associated 

 with carbon which is charged with oxygen instead of hydrogen 

 its function changes and it gives rise to acid. 



Thus glycol is sweet in virtue of the hydroxyl and the hydrogen 

 combined with the carbon, but when the two hydrogen atoms 

 are each replaced by one atom of oxygen oxalic acid is the 

 result, HO-CO-CO-OH. The same gathering of oxygen and 

 hydroxyl together, which is usually called carboxyl, is character- 

 istic of hundreds of known acids. 



The whole story of the sugars is too technical to be presented 



