Modulation of reaction barriers by generating reactive intermediates: double proton transfer reactions

Proton transfer reactions in 1,2,3-triazoles have been studied by computational methods up to the CCSD(T)/aug-cc-pVDZ level. Intermolecular double proton transfer (DPTR) is preferred over an intramolecular single proton transfer (SPTR) mechanism. The DPTR energy profiles along the reaction paths can be understood on the basis of two superimposed potentials with major contributions from two overlapping SPTR steps. For the proton transfer between 1,2,3-triazole and guanidine a plateau-like transition state region was found. Solvent effects and substituents attached to the triazoles turn this plateau into reactive intermediates.