A chemical library or compound library is a collection of stored chemicals usually used ultimately in high-throughput screening or industrial manufacture. The chemical library can consist in simple terms of a series of stored chemicals. Each chemical has associated information stored in some kind of database with information such as the chemical structure, purity, quantity, and physiochemical characteristics of the compound.
In drug discovery high-throughput screening, it is desirable to screen a drug target against a selection of chemicals that try to take advantage of as much of the appropriate chemical space as possible. The chemical space of all possible chemical structures is extraordinarily large. Most stored chemical libraries do not typically have a fully represented or sampled chemical space mostly because of storage and cost concerns. However, since many molecular interactions cannot be predicted, the wider the chemical space that is sampled by the chemical library, the better the chance that high-throughput screening will find a "hit"—a chemical with an appropriate interaction in a biological model that might be developed into a drug.
An example of a chemical library in drug discovery would be a series of chemicals known to inhibit kinases, or in industrial processes, a series of catalysts known to polymerize resins.
Chemical libraries are usually generated for a specific goal and larger chemical libraries could be made of several groups of smaller libraries stored in the same location. In the drug discovery process for instance, a wide range of organic chemicals are needed to test against models of disease in high-throughput screening. Therefore, most of the chemical synthesis needed to generate chemical libraries in drug discovery is based on organic chemistry. A company that is interested in screening for kinase inhibitors in cancer may limit their chemical libraries and synthesis to just those types of chemicals known to have affinity for ATP binding sites or allosteric sites.