Polycyclic compound, nomenclature heterocycles

Current IUPAC and Chemical Abstracts nomenclature has been employed in this index with the former given preference. Substitutive nomenclature has been given preference over radicofunc-tional, additive, subtractive, conjunctive or replacement nomenclature, except where this becomes unwieldy. With many bicyclic and polycyclic compounds bearing heteroatoms, standard bicyclic or polycyclic oxa, aza, and thia replacement nomenclature has often been used. With certain functional groups, where the names are rather complex and probably not familiar to most organic chemists, such as ylides, those compounds have simply been named as sulfur, tellurium and arsonic ylides. Metal catbenes have been treated similarly. With more complex functionality and many heterocycles, the Beilstein Commander Crossfire nomenclature system has been used with certain modifications. 

Polycyclic parent hydrides. These are classified as bridged polyalkanes (also known as von Baeyer bridged systems, from the nomenclature system developed to name them), spiro compounds, fused polycyclic systems and assemblies of identical rings. The four systems may be either carbocyclic or heterocyclic. In developing their names, the following principles are used. 

Extended series of trivial names that are to be retained (or just too frequently used to be simply omitted) have already been compiled in various tables of Chapter 1 of this book (fused polycycles Table l,p. 16, heterocycles Tables 2 and 3, p. 44,50). For the numerous trivial names to be dealt with in the domain of the functional compound classes of Chapter 2 it has been found more appropriate not to include them directly in the text but to confine them to a tabular appendix. Specific hydrocarbon systems such as terpenes and steroids, whose nomenclature is widely dominated by trivial names, are also accounted for in this appendix. 

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