In fusion names

TABLE 1.5 Trivial Names of Heterocyclic Systems Suitable for Use in Fusion Names Listed in order of increasing priority as senior ring system. 

Rings are cited in increasing order of preference for selection as base components in fusion names, i.e. the ring which comes later in the list takes precedence. 

The choice here is essentially between a fully unsaturated parent (type I, see Section II, B, 1, d) and a saturated parent (type II), and should be made with regard to simplicity, brevity, clarity, and suitability in context. (As already noted, choice of an index name by Chemical Abstracts in cases of this type is governed by an elaborate system of rules.) Application of these criteria (apart from the last, which cannot readily be exemplified) is best illustrated by a set of examples (69-74 of course the reader may not agree with the indicated preferences). It must be emphasized that partially saturated skeletons should not be used as parents. In particular the partially and fully saturated units listed by IUPAC in Rule B-2.12 should never be used in fusion names, since any saturation is automatically removed by operation of fusion principles. 

B-2.12—The following trivial and semi-trivial names are retained but are not recommended for use in fusion names. The names of the radicals shown are formed according to Rule B-5. 

In fusion names, the a terms precede the complete name of the parent hydrocarbon. Prefixes denoting ordinary substitution precede the a terms. 

TABLE 1.6 Trivial Names for Heterocyclic Systems that are Not Recommended for Use in Fusion Names... 

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