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This dictionary of over 400,000 chemicals (names, synonyms, and structures) includes links to National Library of Medicine and other databases and resources,
This free, searchable database contains chemical structure information for over 26 million structures. It lets you search by systematic names, synonyms, trade names, and database identifiers.
Use the Compound Search function find chemical information about biological properties. From the National Center for Biotechnology Information, which is part of the National Library of Medicine.