Analysis of structural characteristics of chemical compounds in a large computer-based file. Part IV. Cyclic fragments

The frequencies of monocycles and of primary rings in 1:1 - and 1:2-fused polycycles have been analysed by means of a simple and rapid computer procedure. The analysis deals with the great majority of ring systems in a sample of the Chemical Abstracts Registry System. The data are presented in terms of ring sizes and composition. In each case, the preponderance of six-membered carbocyclic rings is evident.