Term: chain reaction
https://doi.org/10.1351/goldbook.C00960

Definition:
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, Cl&middot; is continuously regenerated in the chain propagation steps: C00960-1.png C00960-2.png 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: C00960-3.png

Related Terms:
1) chain branching (http://doi.org/10.1351/goldbook.C00948).
2) chain transfer (http://doi.org/10.1351/goldbook.C00963).
3) degenerate chain branching (http://doi.org/10.1351/goldbook.D01557).
4) initiation (http://doi.org/10.1351/goldbook.I03042).
5) termination (http://doi.org/10.1351/goldbook.T06274).
6) intermediates (http://doi.org/10.1351/goldbook.I03096).
7) mechanism (<em>of a reaction</em>) (http://doi.org/10.1351/goldbook.M03804).
8) propagation (http://doi.org/10.1351/goldbook.P04881).
9) chain polymerization (<em>of a reaction</em>) (http://doi.org/10.1351/goldbook.C00958).
10) relative molecular mass (<em>of a reaction</em>) (http://doi.org/10.1351/goldbook.R05271).

Images:
1) Not defined (https://goldbook.iupac.org/img/inline/C00960-1.png) 
2) Not defined (https://goldbook.iupac.org/img/inline/C00960-2.png) 
3) Not defined (https://goldbook.iupac.org/img/inline/C00960-3.png) 

Source: PAC, 1993, 65, 2291. 'Nomenclature of kinetic methods of analysis (IUPAC Recommendations 1993)' on page 2293 (https://doi.org/10.1351/pac199365102291)

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. https://doi.org/10.1351/goldbook.C00960

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