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Polycyclic Systems
Both nature and mankind has created many examples
of compounds that contain more than one ring system. These can be classified
depending on how many rings are present and how the rings are joined together.
| If there is a single carbon atom common to two rings, then the system
is said to be "spirocyclic" and the carbon can be described
as the "spirocenter". The simplest example is spiropentane.
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| If two or more atoms are shared between more than one ring then the
system is said to be "polycyclic" in general terms or as
bicyclic, tricyclic, tetracyclic etc. depending on how many rings systems
are present. The simplest polycyclic system is bicyclobutane.
When there are two common atoms in the rings, then it is a "fused" system, as in bicyclobutane.
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| If there are more than two common atoms then the a "bridged"
system is obtained, the simplest example being bicyclo[1.1.1]pentane.
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A couple of interesting examples are shown below.
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© Dr. Ian Hunt, Department of Chemistry |  |