A chemical structure search looks for chemical substances that are identical or highly similar to compounds of interest. Search projects involving substances are rarely complete without chemical structure searching, especially in consideration of the rapid growth of generic and exemplified chemical structures disclosed in patents.
Chemical structure searches can be distinguished by subtypes:
> Exact, where results exactly match the structure searched
> Family, where results include the exact structure searched and its salts, hydrates, solvates, mixtures, stereoisomers, racemic mixtures, geometric isomers, tautomers, zwitterions, coordination compounds, charged compounds, radicals, radical ions and isotopes, as well as polymers in which the structure searched is a component monomer
> Substructure, in which the structure searched can include variables and optional substitutions at defined locations
> Markush, also referred to as generic structure search, in which the structure searched can include variable functional groups, atoms, ring sizes, etc. Markush structures are generally associated with patent literature.
> Fragment, where the structure searched is composed of individual pieces or fragments, and results contain the same collection of fragments, although not necessarily connected in the same way
Chemical structures can also be searched by using substance name or synonym, molecular formula, CAS Registry Number or substance attributes.