NITROGEN BASES 359 



These three substances, CH3NH2, methylamine, (C2H5)2NH, 

 diethylamine, and (C2H5)3 : N, triethylamine, are types of three 

 different classes of amines, known respectively as primary, 

 secondary, and tertiary amines, according as one, two, or three 

 of the hydrogens of ammonia have been replaced by organic 

 radicles. 



Tertiary amines are also known in which the nitrogen 



atom takes part in the formation of a ring, as, for example, in 



pyridine — 



CH 



/ \ 

 CH CH 



II I 



CH CH 



\ / 



N 



which may be regarded as being derived from ammonia by the 



replacement of three atoms of hydrogen by the five carbon 



ring— 



— CH=CH\ 



^CH 

 =CH— CH-^ 



Pyridine, being a substituted ammonia, can form salts by 

 changing the valency of its nitrogen atom from three to five, 

 as follows : — 



Secondary amines containing a nitrogen atom in the ring 

 are also known. 



Thus, when pyridine is reduced by nascent hydrogen, six 

 atoms of hydrogen are added on, and a substance known as 

 piperidine is produced ; this substance is a secondary amine, 

 since it now has a hydrogen atom attached to its nitrogen. 

 Like pyridine, it can also form a salt with hydrochloric acid. 



