Gibbs energy of activation (standard free energy of activation), Δ‡G⚬

https://doi.org/10.1351/goldbook.G02631
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: Δ‡G=R T [ln⁡(kBh)−ln⁡(kT)] where kB is the Boltzmann constant and h the Planck constant (kBh=2.083 58×1010 K−1 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).
See also: enthalpy of activation, entropy of activation
Sources:
PAC, 1994, 66, 1077. (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1118 [Terms] [Paper]
PAC, 1996, 68, 149. (A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC Recommendations 1996)) on page 166 [Terms] [Paper]
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. https://doi.org/10.1351/goldbook.G02631 RIS BibTex EndNote
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