Identifying the CAS Registry Number of Compounds

CAS Registry Numbers (CAS RN) are unique numeric identifiers assigned to specific substances by the Chemical Abstract Service (CAS), a department of the American Chemical Society. CAS RNs are useful when substance searching in chemistry databases, because a single search by CAS RN retrieves results for chemical names, synonyms, trade names, and systematic names of the same substance.
If you know the chemical name you can find its CAS RN by searching the following databases.

  • Common Chemistry
    Contains the CAS RN, chemical names (both formal and common), molecular formulas, and structures or sequences for substances that are of global commercial use and have been cited at least 1,000 times in the CAS databases. Links to Wikipedia records (when available) that have been provided by the Wikipedia Chemicals WikiProject.
  • NIST Chemistry WebBook 
    • Guide for using NIST Chemistry WebBook
      This collection of chemical and physical property data is maintained by the NIST (National Institute of Standards and Technology) Standard Reference Data Program. Includes thermochemical data, IR spectra, mass spectra and ion energetics data for organic and small inorganic compounds. Various search options are available.
  • ChemIDplus
    Includes the names, synonyms, and structures of over 400,000 chemicals.

Research Guide created by Tanis Schumilas, April 2018