A model study on the mechanism and kinetics for reactions of the hydrated electron with H₃O⁺ and NH₄ ⁺ ions

Mechanism and kinetics of the reactions of the hydrated electron (e⁻ _aq) with H₃O⁺ and NH₄ ⁺ cations were determined using quantum chemical computations with both density functional theory (B3LYP) and wavefunction (MP2 and CCSD(T)) methods and the 6-311++G(3df,2p) basis set, in conjunction with a PCM method for treating structures in solution. Although both reactions occur with a hydrogen atom transfer, their mechanisms differ from each other by kinetic results. While the reaction of e⁻ _aq and H₃O⁺ in solution is diffusion-controlled, NH₄ ⁺ reacts with e⁻ _aq via a transition structure with H-tunneling. The predicted rate constants agree well with available experimental results.