{"term":{"id":"00960","title":"chain reaction","longtitle":"IUPAC Gold Book - chain reaction","doi":"10.1351\/goldbook.C00960","code":"C00960","status":"current","also defines":"<em>also defines<\/em>: propagation step, propagation","definitions":[{"id":1,"text":"A reaction in which one or more reactive reaction intermediates (frequently radicals) are continuously regenerated, usually through a repetitive cycle of elementary steps (the 'propagation step'). For example, in the chlorination of methane by a radical mechanism, $\\ce{Cl^{.}}$ is continuously regenerated in the chain propagation steps:   In chain polymerization reactions, reactive intermediates of the same types, generated in successive steps or cycles of steps, differ in relative molecular mass, as in: ","links":[{"term":"chain branching","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/C00948"},{"term":"chain polymerization","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/C00958"},{"term":"chain transfer","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/C00963"},{"term":"degenerate chain branching","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/D01557"},{"term":"initiation","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/I03042"},{"term":"intermediates","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/I03096"},{"term":"mechanism","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/M03804"},{"term":"relative molecular mass","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/R05271"},{"term":"termination","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/T06274"}],"sources":["PAC, 1993, 65, 2291. 'Nomenclature of kinetic methods of analysis (IUPAC Recommendations 1993)' on page 2293 (https:\/\/doi.org\/10.1351\/pac199365102291)","PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1094 (https:\/\/doi.org\/10.1351\/pac199466051077)","PAC, 1996, 68, 149. 'A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC Recommendations 1996)' on page 157 (https:\/\/doi.org\/10.1351\/pac199668010149)"],"seealso":["PAC, 1990, 62, 2167. 'Glossary of atmospheric chemistry terms (Recommendations 1990)' on page 2179 (https:\/\/doi.org\/10.1351\/pac199062112167)"]}],"altoutputs":{"html":"https:\/\/goldbook.iupac.org\/terms\/view\/C00960\/html","xml":"https:\/\/goldbook.iupac.org\/terms\/view\/C00960\/xml","plain":"https:\/\/goldbook.iupac.org\/terms\/view\/C00960\/plain"},"citation":"Citation: 'chain reaction' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351\/goldbook.C00960","license":"The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/) for individual terms.","collection":"If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org .","disclaimer":"The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using.","accessed":"2026-04-20T19:28:59+00:00"}}