Free chemical database to search for physical properties? I am looking for an Open-access tool that can search "backwards", eg. give me all the structures corresponding to a given heat of formation, critical pressure, etc. It would be even better if the database canbe automatically searched by API or by downloading it. Currently my best go is ChemExper, where I can search for some of the properties, but it is challenging to make it automatic. Is there anything similar in the field?
As I've mentioned on other related questions, this is very much an open topic. There aren't many open-access databases in chemistry, and far fewer that have APIs.


As suggested in the other answer, there are multiple ways to query / scrape Wikipedia.
ChemSpider offers some property search features.
Reaxys offers some property searching, including spectra features. It's not open access.