Chemical name may seem like an easy and straightforward way to search for a substance but Judith Currano, Chemisty Librarian at the University of Pennsylvania (2014, p110), notes that there many different names that a substance can go by:
- systematic names assigned by IUPAC or CAS
- common names
- historic names
- trade names
- brand names
She observes that any name you enter must be found in that substance's record and advises that you may have to enter several different synonyms to match what you are looking for.
Currano also points out that formula searching presents an opposite sort of problem, in that a single formula may represent the composition of many different substances, a problem especially evident when seraching for common organic substances. You will have to review several hits to locate the substance of interest or limit your search with additional information to narrow down the possibilities (2014, p111).
Using substance identifier numbers such as the CAS Registry number or the InChI number are additional tools to search by, although these are not without their issues as well. The CAS Registry number assigned by Chemical Abstracts Services is a unique identifier but the problem is knowing the CAS Registry number assigned to your substance of interest! InChI (International Chemical Identifier) numbers were started in 2000 by the International Union of Pure and Applied Chemistry (IUPAC). InChI numbers are unique and non-proprietary (individuals can create them using InChI generators (e.g., www.iupac.org/inchi)) but they are complicated to write so they used infrequently for searching (Currano, 2014, p111-112).
Currano points out that a substance's chemical structure is also unique but they can be cumbersome to draw, especially if the structure is large and that success searching by structure is contingent on how the structure is represented in the literature; structure searching relies on matching the connections between atoms in a structure as drawn with the connection tables for substances in the database. Where those match determines the substances returned as results.
Currano, J. (2014). Searching by structure and substructure. In J.N.Currano & D.L. Roth (Eds.), Chemical Information for Chemists: A primer (pp.109-145). Cambridge,UK: RSC Publishing.