Recently, we had suggested that the motion along the promoter mode in the first part of the IRC of proton transfer reaction enhances the delocalization of $n_\sigma$ electrons on the acceptor atom into the $\sigma^\ast$ orbital of the donor-hydrogen covalent bond, and as a consequence weakens it. This leads to a reduction of the barrier to the proton transfer as well as the stretching frequency of donor-hydrogen bond. An extension of this to the concerted multiple proton transfer reactions implies that the kinetic isotope effect in such reaction depends exponentially on the number of protons that are being transferred. Computational evidence on three systems, (HF)3, formic acid dimer, and (H2O)$_n$ clusters is provided to support this assertion.
Volume 135, 2023
Continuous Article Publishing mode
Click here for Editorial Note on CAP Mode