"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] The termsreactant andreagent are often used interchangeably, butreactant specifies a substanceconsumed in the course of a chemical reaction.[1]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.
Inorganic chemistry, the term "reagent" denotes a chemical ingredient (a compound or mixture, typically of inorganic or small organic molecules) introduced to cause the desired transformation of an organic substance. Examples include theCollins reagent,Fenton's reagent, andGrignard reagents.
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.
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.
