ABSTRACT
Various publications from the Chemical Abstracts Service can be used to œnd the name of a known ring system. The most comprehensive source of ring system names is the Ring Systems Handbook (RSH). Entries are in ring analysis order, i.e., according to the following hierarchy of ring data:
1. Number of component rings 2. Sizes of component rings 3. Elemental analysis of component rings
For example, the ring system
contains four rings, with sizes 6,6,6,7, and with elemental compositions C5N-C6-C6-C5NO. The preferred parent contains the senior ring system. For ring systems, nitrogen heterocycles > other heterocycles > carbocycles. Thus, pyridine > furan > naphthalene. If two ring systems are of a type, then that with the greater number of individual rings is preferred, e.g., quinoline > pyridine, and naphthalene > benzene. A further twelve criteria are needed to allow a decision to be made in all cases. These can be found in the Chemical Abstracts Index Guide, Appendix IV, paragraph 138.
