Organic The Principal Group

Groups closely related chemically to a group cited in list A rank in order of preference immediately after their parent groups e.gr., salts, simple esters, and acid halides after acids oximes, semicarbazones, etc., after the aldehyde or ketone. The lists in Table 4 are clearly not exhaustive but it is surprising how many actual cases it covers. 

We can illustrate this by a few examples. CO ranks before OH, so that we write 2-hydroxycyclohexanone and not 2-oxocyclohexanol in the same way OH ranks before KH2, so that is p-aminophenol 

The lasl3 column in Table 4 gives the separate word used when the compound is named by the radico-functional method (see paragraph (d), p. 43) the preceding word or, for bivalent groups, two words are in radical form, as in ethyl alcohol, ethyl methyl ether, acetyl chloride. 

The formation of names by means of Table 4 will be familiar from general chemistry, and further examples are unnecessary here, but a few special cases should be noted. 

The nomenclature of amines is exceptional. By very long custom radical names may be attached to the ending amine, as in ethylamine but it is equally correct to add amine to the parent name, as indicated in Table 4, giving names such as phenanthren-1-amine, quinolin-8-amine, or even ethanamine. The latter practice is often reserved for more complex cases but that is not a necessary limitation. The same alternatives exist for ammonium salts. Secondary and tertiary amines are treated as substitution products of the most complex constituent primary amine, with N- prefixes when substitution elsewhere might be reasonable, as in triethylamine, dimethylamine, 

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