where ΔΔ𝐺 ‡ solv represents the solvation effect on the free energy of activation, and 𝐴 and 𝐸 𝑎 are the gas phase kinetic parameters of the same reaction. The ΔΔ𝐺 ‡ solv term accounts for the difference between the solvation free energies of the reactants and transition state (TS). This approach assumes 𝐴 and 𝐸 𝑎 to be constant and attempts to describe the non-Arrhenius behavior of 𝑘 liq in terms of the temperature dependence of ΔΔ𝐺 ‡ solv . As temperature approaches the critical point of a solvent, the solvent's dielectric constant changes significantly, causing the ΔΔ𝐺 ‡ solv value to change a lot for the reaction whose reactants and TS have different dipole moments. Marrone, Tester, and their co-workers adopted the Kirkwood theory to express ΔΔ𝐺 ‡ solv as a function of the dielectric constant of a solvent and the dipole moments and molecular radii of reactants and TS. While they were able to reproduce the experimental data of CH 2 Cl 2 hydrolysis from room temperature up to the critical point of water, their method relies on several variables that cannot be easily fitted to experimental data.