SPIRO AND RELATED COMPOUNDS

In order to extend canonical nomenclature to compounds in which the union of two or more cycles is either a single atom, a single edge, or when a succession of edges connect otherwise unconnected cycles, an expansion of the concept of bridging is undertaken. Four important different protocols suggested by such an extension include  

These latter two techniques are important both for spiro molecules in which the rings containing the common atom are of different constitution and for ring assembly compounds. Additionally, note that in many instances the other distinct types of nomenclature that had been introduced earlier [Cartesian (in Chapter 1) and cylindrical (in Chapter 3)] may be interconverted in much the same way as the different types of coordinate systems in geometry may be interconverted. 

The choice of an optimal name for a given molecule is based on the heuristic principles of shortness and simplicity. 

Up until this point, all of the cyclic compounds that have been examined have the property that removal of a single atom may disrupt the cycle, but will still leave a connected graph. In graph theoretical terms this 

Note that for acyclic compounds larger than a single atom, deletion of an interior atom will always increase the number of blocks. 

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