CHAPTER XI 



PLANT BASES 



There are present in plants a number of substances which form a group, 

 and which may be termed nitrogen bases, or natural bases. These sub- 

 stances are of various constitution but they have the property in common 

 of forming salts with acids by virtue of the presence of primary, secondary, 

 or tertiary amine groupings. Such groupings confer a basic property 

 upon a compound and, as a result, salts are formed with acids on analogy 

 with the formation of ammonium salts : 



NH3+ HCI = NH4CI (NH3 • HCI) 



CH3NH2+ HCI = CH3NH2 • HCI 

 methylamine 



(CH3)2 NH + HCI = (CH3)2 NH • HCI 

 diraethjlamine 



(CHgJg N + HCI = (CH3)3 N • HCI 

 trimethylamine 



The hydrogen atoms of ammonia can also be replaced by groups of 

 greater complexity, as will be seen below. 



Complex ring compounds in which nitrogen forms part of the ring 

 are termed heterocyclic, such as the alkaloids, purines and some amines, 

 for instance pyrrolidine (see below). 



The plant bases can be conveniently classified into four groups and 

 this is also to a large extent a natural grouping. They are: 



1. Amines ) ci- 1 .11 



^ ^ . . y bimpler natural bases. 



2. i3etainesj ^ 



3. Alkaloids. 



4. Purine bases. 



The first two groups have been termed the simpler natural bases. 

 They are much more widely distributed in the vegetable kingdom than 

 the alkaloids and purines, since they have probably much more significance 

 in general metabolism. The isolation of the simpler bases is a matter of 

 much greater difficulty than that of the alkaloids: the former are soluble 

 in water but insoluble in ether and chloroform, and so are not readily 

 separated from other substances. The alkaloids, however, occur in the 

 plant as salts of acids and if the plant material is made alkaline the free 

 bases can be extracted with ether or chloroform. 



