Title: homolysis
Long Title: IUPAC Gold Book - homolysis
DOI: 10.1351/goldbook.H02851
Status: current

Definition
The cleavage of a bond ('homolytic cleavage' or 'homolytic fission') so that each of the molecular fragments between which the bond is broken retains one of the bonding electrons. A unimolecular reaction involving homolysis of a bond (not forming part of a cyclic structure) in a molecular entity containing an even number of (paired) electrons results in the formation of two radicals:  It is the reverse of colligation. Homolysis is also commonly a feature of bimolecular substitution reactions (and of other reactions) involving radicals and molecules.

Related Terms
- bond-dissociation energy: https://dev.goldbook.iupac.org/terms/view/B00699
- colligation: https://dev.goldbook.iupac.org/terms/view/C01153
- heterolysis: https://dev.goldbook.iupac.org/terms/view/H02809
- unimolecular: https://dev.goldbook.iupac.org/terms/view/M03989

Source
- PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1122 (https://doi.org/10.1351/pac199466051077)

Other Outputs
- html: https://dev.goldbook.iupac.org/terms/view/H02851/html
- json: https://dev.goldbook.iupac.org/terms/view/H02851/json
- xml: https://dev.goldbook.iupac.org/terms/view/H02851/xml

Citation: Citation: 'homolysis' 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.H02851
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Accessed: 2026-04-20T03:09:22+00:00