A chemical reaction, the main feature of which is the intermolecular or intramolecular transfer of a proton (hydron) from one binding site to another. For example: In the detailed description of proton transfer reactions, especially of rapid proton transfers between electronegative atoms, it should always be specified whether the term is used to refer to the overall process (including the more-or-less encounter-controlled formation of a hydrogen bonded complex and the separation of the products; see microscopic diffusion control) or just to the proton transfer event (including solvent rearrangement) by itself.