Title: Gibbs energy of activation
Long Title: IUPAC Gold Book - Gibbs energy of activation
DOI: 10.1351/goldbook.G02631
Status: current
Index: quantity

Definition
The standard Gibbs energy difference between the transition state of a reaction (either an elementary reaction or a stepwise reaction) and the ground state of the reactants. It is calculated from the experimental rate constant \(k\) via the conventional form of the absolute rate equation: \[\Delta ^{\ddagger}G = R\ T\ \left[\ln (\frac{k_{\rm{B}}}{h}) - \ln (\frac{k}{T})\right]\] where \(k_{\rm{B}}\) is the Boltzmann constant and \(h\) the Planck constant (\(\frac{k_{\rm{B}}}{h} = 2.083\ 58\times 10^{10}\ \rm{K}^{-1}\ \rm{s}^{-1}\)). The values of the rate constants, and hence Gibbs energies of activation, depend upon the choice of concentration units (or of the thermodynamic standard state).

Related Terms
- Boltzmann constant: https://dev.goldbook.iupac.org/terms/view/B00695
- Gibbs energy: https://dev.goldbook.iupac.org/terms/view/G02629
- Planck constant: https://dev.goldbook.iupac.org/terms/view/P04685
- activation: https://dev.goldbook.iupac.org/terms/view/A00093
- elementary reaction: https://dev.goldbook.iupac.org/terms/view/E02035
- enthalpy of activation: https://dev.goldbook.iupac.org/terms/view/E02142
- entropy of activation: https://dev.goldbook.iupac.org/terms/view/E02150
- ground state: https://dev.goldbook.iupac.org/terms/view/G02704
- rate constant: https://dev.goldbook.iupac.org/terms/view/O04322
- standard state: https://dev.goldbook.iupac.org/terms/view/S05925
- stepwise reaction: https://dev.goldbook.iupac.org/terms/view/S05970
- transition state: https://dev.goldbook.iupac.org/terms/view/T06468

Sources
- PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1118 (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 166 (https://doi.org/10.1351/pac199668010149)

Other Outputs
- html: https://dev.goldbook.iupac.org/terms/view/G02631/html
- json: https://dev.goldbook.iupac.org/terms/view/G02631/json
- xml: https://dev.goldbook.iupac.org/terms/view/G02631/xml

Citation: Citation: 'Gibbs energy of activation' 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.G02631
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Accessed: 2026-06-13T02:56:38+00:00