PubChem
https://pubchem.ncbi.nlm.nih.gov/
PubChem is an open chemistry database at the National Institutes of Health (NIH). "Open" means that you can put your scientific data in PubChem and that others may use it. They collect information on chemical structures, indentifiers, chemical and physical properties, biological activities, patents, health, safety, toxicity data, and many others.
