A probabilistic rate theory connecting kinetics to thermodynamics

International audienceKinetics and thermodynamics are largely disconnected in current theories because Arrhenius activation energies (Ea) have strictly no influence on equilibrium distributions. A first step towards the incorporation of rate theories in thermodynamics is the identification of the pre-exponential term of the Arrhenius equation as an entropic quantity. A second step examined here is the possible contribution of Ea in equilibrium landscapes. Interestingly, this possibility exists if envisioning the energetic exponential term of Arrhenius rate constants as the probability that the energy of the reactant is sufficient for the transition. This radically new approach encompasses Maxwell–Boltzmann distributions and solves inconsistencies in previous theories, in particular on the role of temperature in kinetics and thermodynamics. These probabilistic rate constants are then reintroduced in dynamic systems to provide them with the two distinct facets of time the time step and the time arrow. © 2018 Elsevier B.V