Local and non-local properties controlling the strength of Brønsted acids and bases

A general formula giving both the energy of heterolytic dissociation of Brønsted acids and the proton affinity of Brønsted bases is proposed, thus providing a rationale for the proton exchange between acids and bases. The formula improves and extends previous ones proposed in the past (DeKock and Barbachyn, Cerofolini and Re, this collaboration) and establishes a correlation between, on one side, the proton affinity of the (neutral or negatively charged) base and, on the other side, the local properties of the proton-hosting site and non-local properties of the base, like its size and ionization energy. Our model involves intuitively appealing chemical concepts and can be very useful to close the gap between the experimental view and the ab initio calculations approach.