Volume 71, Issue 3

These recommendations document the von Baeyer system for naming polycyclic ring systems described in Rules A-31, A-32 and B-14 of the Nomenclature of Organic Chemistry, Sections A, B, C, D, E, F and H, 1979 and R-2.4.2 of A Guide to IUPAC Nomenclature of Organic Compounds, 1993 and extend the system to cover more complex cases. It provides guidance on the naming of ring systems which previously the rules did not cover. The methods is to identify the main ring and main bridge which provide the basic bicyclic system and to number these atoms. Then all further bridges, whether or not they include additional atoms, are identified by indicating not only the number of atoms but also the two atoms to which the bridge is attached. The final name also indicated the number of rings and the total number of skeletal atoms in the ring systems. Heteroatoms, unsaturation and substituents are indicated in the usual way.

Spiro ring systems have two or more rings linked by one common atom. Several different methods are used to name such systems. Rules A-41, A-43, B-10 and B-12 (Nomenclature of Organic Chemistry, 1979) describe the basics of how to name these compounds. The alternative methods in rules A-42 and B-11 are abandoned. This document describes the nomenclature in greater detail and extends it to cover branched polyspiro systems and compounds where three rings have one common spiro atom. A new notation, based on the von Baeyer method of naming spiro systems where all components are monocyclic, allows both unbranched and branched polyspiro systems to be named without ambiguity. It also enables the names to be readily interpreted.