# Which organic compounds have the most strongly negative enthalpies of formation?

I've been using the NIST Webbook to list organic compounds and look at their heats of formation (kJ/g, not mol). If I limit myself to three carbons, I still get over 400 results.

I can use some heuristics to guess which ones have strong heats of formation. I'm interested in kJ/g rather than /mol so smaller molecules are more likely, and certain bonds like $\ce{C=O}$ help, but that's not good enough for my project because I need to be certain.

Oxamic acid, ammonium formate, and ammonium acetate are up there, but who knows how many I might be missing, limited as I am to looking up small molecules?

So I'm hoping someone with a lot of experience might tell me something off the top of their head.

• Limiting yourself to three carbons seems like a way to bias yourself to things that contain large amounts of other atoms. You may want to limit total atoms or total "heavy" (i.e. non-hydrogen) atoms instead of just C atoms. The compounds you've found -- ammonium acetate, oxamic acid, etc. -- have more heavy atoms overall, and thus more bonds, and thus higher enthalpies of formation. – Curt F. Jun 25 '17 at 5:42
• @CurtF. - Limiting the search at all is the very problem, because as I said, who knows how many I might be missing, limited as I am to looking up small molecules? (And by "small" I mean fewer than 12 or so atoms.) – MackTuesday Jun 25 '17 at 18:13