PubChem CID

The compound identifier in PubChem, NIH's open chemistry database — the record from which structure, formula and computed molecular weight can be read for free.

PubChem is the National Institutes of Health's open chemical database, and a CID — compound identifier — is the accession number of one unique, standardised chemical structure within it. Substance records from many depositors that describe the same structure are merged into a single compound record, so the CID functions as PubChem's canonical key for a molecule.

A CID resolves to a page carrying the structure, molecular formula, computed average and monoisotopic mass, synonyms, and cross-references into other registries and the literature. Those computed values describe the drawn structure — the free base — which is the source of the standing caveat that a registry weight is not the mass of a vial's salt-form contents.

Because deposition is open, PubChem's coverage of research compounds is broader than curated registries, and its records are correspondingly more variable: synonym lists can absorb vendor aliases, and separate CIDs sometimes exist for salt forms or tautomers of one compound. The CIDs on this site's research pages are verified against the record before publication, and one compound's CID was dropped when verification failed.

SourcePubChem — about PubChem

For research purposes only. Not for human consumption, diagnosis, treatment, or prevention of any condition. Nothing on this page is medical advice.