"Reactants" redirects here; not to be confused withReactance.
Reagents, such assulfur (pictured), are the starting materials used in chemical reactions.
Inchemistry, areagent (/riˈeɪdʒənt/ree-AY-jənt) oranalytical reagent is a substance or compound added to a system to cause achemical reaction, or test if one occurs.[1] Areactant is a substance or compound that is consumed in a chemical reaction.[1] The termsreactant andreagent are often used interchangeably, but reactant specifies a substanceconsumed in the course of a chemical reaction;reagent is used in the context ofchemical analysis, whilereactant is used in the context of reaction itself.Solvents, though involved in thereaction mechanism, are usually not called reactants. Similarly,catalysts are not consumed by the reaction, so they are not reactants. Inbiochemistry, especially in connection withenzyme-catalyzed reactions, the reactants are commonly calledsubstrates.
In commercial or laboratory preparations,reagent-grade designateschemical substances meetingstandards ofpurity that ensure the scientific precision and reliability ofchemical analysis, chemical reactions or physical testing. Purity standards for reagents are set by organizations such asASTM International or theAmerican Chemical Society. For instance, reagent-quality water must have very low levels of impurities such assodium andchloride ions,silica, and bacteria, as well as a very highelectrical resistivity. Laboratory products which areless pure, but still useful and economical for undemanding work, may be designated astechnical,practical, orcrude grade to distinguish them from reagent versions.[citation needed]
Tool compounds are an important class of reagent in biology. They are small molecules or biochemicals likesiRNA or antibodies that are known to affect a given biomolecule[ambiguous]—for example adrug target—but are unlikely to be useful as drugs themselves, and are often starting points in thedrug discovery process.[5][6]
However, many natural substances are hits in almost any assay in which they are tested, and therefore not useful as tool compounds. Medicinal chemists class them instead aspan-assay interference compounds. One example iscurcumin.[7][8][9]
^Kenakin, T; Bylund, DB; Toews, ML; Mullane, K; Winquist, RJ; Williams, M (1 January 2014). "Replicated, replicable and relevant-target engagement and pharmacological experimentation in the 21st century".Biochemical Pharmacology.87 (1):64–77.doi:10.1016/j.bcp.2013.10.024.PMID24269285.
^Baell, JB; Holloway, GA (8 April 2010). "New substructure filters for removal of pan assay interference compounds (PAINS) from screening libraries and for their exclusion in bioassays".Journal of Medicinal Chemistry.53 (7):2719–2740.CiteSeerX10.1.1.394.9155.doi:10.1021/jm901137j.PMID20131845.
