Nitrogen compounds parent hydrides

In the names of amines, the general use of suffixes and prefixes is not always observed. Normally, the suffix -amine would be added to the name of the parent hydride and engender names such as methanamine (CH3-NH2). Further substitution on the nitrogen atom would then be indicated by prefixes, leading to names that appear very cumbersome, such as A -methylmethanamine for (CH3)2NH and N,N-dimethylmethanamine for (CH3)3N. The traditional names of methylamine, di-methylamine and trimethylamine are much simpler. In these names, the term amine is not a suffix. It is, in fact, the name of the parent hydride, NH3, which now serves as the basis of substitutive names. Names such as diethylamine and tributylamine are representative of the preferred nomenclature. Diamines are named accordingly, as with ethane-1,2-diamine for H2N-CH2-CH2-NH2 and propane-1,3-diamine for H2N-[CH2]3-NH2. There are allowed alternatives for these last two compounds ethylenediamine and propane-1,3-diyldiamine. 

As in five-membered heterocycles, ring strain in six-membered heterocycles is of little or no importance. Pyran and thiine (thiopyran), with an oxygen or sulfur atom, respectively, and pyridine, with a nitrogen atom, are the parent compounds of six-membered neutral heterocycles with one heteroatom and the maximum number of noncumulative double bonds. In contrast to pyran and thiine, pyridine exists as a cyclic conjugated system. However, by (formal) abstraction of a hydride ion, both pyran and thiine can be converted into the corresponding cyclic conjugated cations, i.e. the pyrylium and the thiinium ions (thiopyrylium ion). 

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