Title: quasi-equilibrium
Long Title: IUPAC Gold Book - quasi-equilibrium
DOI: 10.1351/goldbook.Q04999
Status: current

Definition
In conventional transition-state theory it is assumed that activated complex are formed in a state of equilibrium with the reactants. They are not in classical equilibrium with the reactants; if they were, addition of more activated complexes to the system would cause the equilibrium to shift in favour of the reactants. This would not occur for an activated complex, and the term quasi-equilibrium is used to denote this special type of equilibrium.

Related Terms
- activated complex: https://goldbook.iupac.org//terms/view/A00092
- transition-state theory: https://goldbook.iupac.org//terms/view/T06470

Source
- PAC, 1996, 68, 149. 'A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC Recommendations 1996)' on page 179 (https://doi.org/10.1351/pac199668010149)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/Q04999/html
- json: https://goldbook.iupac.org/terms/view/Q04999/json
- xml: https://goldbook.iupac.org/terms/view/Q04999/xml

Citation: Citation: 'quasi-equilibrium' 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.Q04999
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Accessed: 2026-06-20T06:06:00+00:00