Role of water in intramolecular proton transfer reactions of formamide and thioformamide

Abstract

A theoretical study of the mechanism of intramolecular proton transfer reactions in formamide and thioformamide is presented; the focus is on the characterization of the role of water in the reactions. The reaction mechanisms was analyzed with the help of energy profiles in the frame of the reaction force analysis and using the reaction electronic flux to characterize the electronic activity that takes place along the reaction. Bader’s quantum theory of atoms in molecules is used to confirm the reaction mechanism and help elucidate the specific role of water. Results at the DFT/B3LYP 6-311G** level of theory show that water catalyzes the proton transfer reaction lowering the activation energy by a factor of two. The reaction force analysis allowed the characterization of activation energies, indicating that in all four reactions, it is mostly due to structural reordering.