ABSTRACT
Publications from Chemical Abstracts Service (CAS) can be used to find the name of a known ring system. An italic H appearing with the name of a ring or ring system usually denotes an indicated or added hydrogen atom. Sometimes a hydrogen atom needs to be added to a ring system in order to accommodate structural features such as principal groups. Von Baeyer names are used for bridged and occasionally for non-bridged ring systems. Fused ring systems that have other bridges are usually named by prefixing the name of the bridge to the name of the fused ring system. Many common monocyclic hetero systems have trivial names, such as, pyridine and furan. Those that do not can be named by the Hantzsch–Widman method. Ring assemblies are polycyclic systems consisting of two or more identical rings or ring systems directly joined to each other by single or double bonds.
