Nomenclature of polycyclic compounds

The nomenclature of polycyclic compounds is a specialised area of organic nomenclature. There are several methods, depending on the particular compound:

• von Baeyer nomenclature, including
  • spiro nomenclature
• fusion nomenclature
• natural product nomenclature, which can be further subdivided into
  • steroid nomenclature
  • terpene nomenclature
  • alkaloid nomenclature

While there may be choice of nomenclature methods for a given compound, it is normal to use natural product nomenclature for steroids, terpenes, alkaloids and other compounds of biological origin; fusion nomenclature for fused ring systems such as polycyclic aromatic hydrocarbons; and von Baeyer nomenclature for other polycyclic compounds. The systems are not completely independent of one another.

Definitions

Polycyclic compound

A compound which, for nomenclature purposes, requires at least two scissions to convert it into an open-chain compound

Spiro compound

A compound which has two (or three) rings which have only one atom in common and the two (or three) rings are not linked by a bridge. The common atom is known as a spiro atom.

Fusion

The process of joining rings, for nomenclature purposes, so that two rings have two atoms and one bond in common, the resulting compound being regarded as being derived from the two rings as separate entities.