How can I search molecules by constituent atoms Given a set of atoms, I would like to find (some / the most common) molecules that include only (some/all) atoms of the set. Is there any online search engine that can do this?


  E.g.
  Atoms={C,H}
  -->
  Molecules={CH$_4$, C$_2$H$_6$, ...}


Note:


I am looking for known molecules.
It is OK if I can only find chemical formulae, so without all possible configurations.
You can use ChemSpider's full search:

http://www.chemspider.com/FullSearch.aspx

and click on the 'Elements' section. Alternatively, there is a direct link here:

http://www.chemspider.com/ElementsSearch.aspx

This gives you two periodic tables that you can select elements from for your search. I think the upper one is 'allowed' and the lower one is 'forbidden', but I haven't tested this.

Of course, as pointed out in the comments, the set {C, H} will give you most of the database! However, for rarer elements this can be a better filter.