Term: initiation
https://doi.org/10.1351/goldbook.I03042

Definition:
A reaction or process generating free radicals (or some other reactive reaction intermediates) which then induce a chain reaction. For example, in the chlorination of alkanes by a radical mechanism the initiation step is the dissociation of molecular chlorine.

Related Terms:
1) radicals (http://doi.org/10.1351/goldbook.R05066).
2) reactive (http://doi.org/10.1351/goldbook.R05180).
3) reaction intermediates (http://doi.org/10.1351/goldbook.R05171).
4) chain reaction (http://doi.org/10.1351/goldbook.C00960).
5) dissociation (http://doi.org/10.1351/goldbook.D01801).
6) alkanes (http://doi.org/10.1351/goldbook.A00222).

Source: PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1125 (https://doi.org/10.1351/pac199466051077)

Citation: 'initiation' 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.I03042

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