Is there an algorithm for finding the number of cyclic isomers a given compound might have?

I've found a general algorithm for all isomers: link, but I'm not sure how to apply it for cyclic isomers only.

  • $\begingroup$ Do you care only for structural isomers, or do you need spatial isomers too? I'm sure including the latter makes it a much harder problem. $\endgroup$ Jan 22, 2014 at 23:38
  • $\begingroup$ Only structural isomers. $\endgroup$ Jan 22, 2014 at 23:39
  • $\begingroup$ I wouldn't be astonished if A. T. Balaban has published something on this. Apart from his great book on pyrylium salts, he has spent decades on the application of graph theory in chemistry. $\endgroup$ Jan 23, 2014 at 0:30
  • 2
    $\begingroup$ Wow, that code listed is awful. It really hurts my eyes! $\endgroup$
    – Jori
    Apr 19, 2015 at 12:40
  • $\begingroup$ Depending on the level of complexity, you may want to consider statistical approaches (treating isomers as populations) too. $\endgroup$ Jun 6, 2015 at 1:37

1 Answer 1


If I remember correctly, several years ago I stumbled over the SMOG program addressing this question (description here). The software requestested sum formula and a selection of allowed structural elements, cyclic substructures were among them. Maybe the algorithms implemented are not the first ones to answer such a question, yet publications like this showcase continuing interest in this field, too.


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