## Gibbs energy of activation (standard free energy of activation), $$\Delta ^{\ddagger}G^{\,\unicode{x26ac}}$$

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: $\Delta ^{\ddagger}G = R\ T\ \left[\ln (\frac{k_{\text{B}}}{h}) - \ln (\frac{k}{T})\right]$ where $$k_{\text{B}}$$ is the Boltzmann constant and $$h$$ the Planck constant ($$\frac{k_{\text{B}}}{h} = 2.083\ 58\times 10^{10}\ \text{K}^{-1}\ \text{s}^{-1}$$). 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).