CHAPTER XII 

 THE VEGETABLE BASES 



WE come, now, to the consideration of the characteristically 

 nitrogenous compounds of plants. None of the groups of com- 

 pounds which have been considered thus far have, as a group, 

 contained the element nitrogen. This element is present in the 

 chlorophylls and hi certain other pigments, but not as the char- 

 acteristic constituent of the molecular structure of the group of 

 compounds, nor do these compounds serve as the source of supply 

 of nitrogen for the plant's needs. 



The characteristic nitrogen-containing compounds may all be 

 regarded as derived from ammonia, or ammonium hydroxide, by 

 the replacement of one or more hydrogen atoms with organic 

 radicals of varying type and complexity. If the group, or groups, 

 which be considered as having replaced a hydrogen atom in ammo- 

 nia, in such compounds, is an alkyl group, the compound is strongly 

 basic in character and is known as an amine; whereas if the 

 replacing group is an acid radical, the resulting compound may be 

 neutral (known as add amides), or weakly acid (known as amino- 

 acids) in type. Compounds of the first type constitute the vege- 

 table bases; while those of the second type are the proteins. 



The vegetable bases may be divided into three groups. These 

 are (a) the plant amines, which are simple open-chain amines; (6) 

 the alkaloids, which are comparatively simple closed-ring amines, 

 containing only one nitrogen atom in any single ring; and (c) 

 the purine bases, which are complex compounds containing a 

 nucleus with four carbon atoms and four nitrogen atoms arranged 

 alternately to form a double-ring group. 



THE PLANT AMINES 



The simple amines bear the relation to ammonia, or ammonium 

 hydroxide, represented by the following formulas, in' which the 

 R indicates any simple alkyl radical: 



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