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41 42 Organic: General of purely trivial names, some old, some new, and then a fully logical nomenclature, simple to understand and compatible with computer usage, might appear a desirable objective. Even if this were possible, however, such a completely new start would meet at most only gradual acceptance by chemists accustomed to current terminology. So until the omens are more favourable, current lUPAC nomenclature needs to be mastered in spite of its deficiencies, at least because its general principles are used to a large extent in Chemical Abstracts {CA) indexes.

The former can be outlined at once as follows; in most cases they apply equally to trivial, semitrivial, and systematic names. , of Η by CI (chlorination), by NO2 (nitra­ tion), by CH3 (methylation), even though this replacement may not be the method of synthesis. Some restriction is necessary. Chlorination, for instance, is only replacement of Η by CI; the term should not be used for addition, as in: C 6 H 5 C H = C H 2 +CI2 - ^ C ö H s C H C l C H i C l or for the reaction >C-0H^>C-C1 Hydrogenation is an obvious exception.

There are also systems for such compounds where specific syllables have prescribed meanings for ring structure. , '-lactone', 'seco-', '-oside'. , (l)/(2), (l)/(4), and (2)/(4); . some have severely restricted use. Much the commonest is simple substitutive nomenclature. Also a warning is perhaps appropriate already here that the special treatments of acids and their derivatives (see pp. 107-112), aldehydes {see p. 115), and amines {see pp. 120-121) do not fit wholly into any of the classes named above.