Our methodology to estimate the entropy of barrierless reactions is as follows: First, the electronic dissociation energy is calculated and a morse potential fit function is applied (Figure ). The modelling of the onset entropy of the dissociation process is done by using quantum chemical descriptors. The descriptor itself is used to locate the intramolecular distance, r cleave , at which the bond is assumed to be broken (Figure ). We use r cleave as the inflection point of the entropy fit. Hence, at the bond breaking distance r cleave , we have reached half of the total entropy. The onset of entropy is modelled with a sigmoid function and the resulting entropy curve -T ∆S f it (r, k i ) (Figure ) is added to the electronic energy ∆E f it (r), to yield the Gibbs free energy surface ∆G f it (r) (Figure ). Assuming no minimum after the TS, ensured through modification of the steepness of the sigmoid, the maximum of