No‐Barrier Theory: Calculating Rates of Chemical Reactions from Equilibrium Constants and Distortion Energies

No‐barrier theory is a new approach to the calculation of rate constants for reactions in solution, from the corresponding equilibrium constants. It requires relatively small molecular orbital theory calculations, and has been very successful. It is in the spirit of Marcus theory, but does not require an “intrinsic barrier”. The approach is explained, with an examination of the way in which the ideas on which it is based were “in the air”.