Communication: Charge transfer dominates over proton transfer in the reaction of nitric acid with gas-phase hydrated...

The reaction of HNO₃ with hydrated electrons (H₂O)_n^- (n = 35-65) in the gas phase was studied using Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry and ab initio molecular dynamics simulations. Kinetic analysis of the experimental data shows that OH^-(H₂O)_m is formed primarily via a reaction of the hydrated electron with HNO₃ inside the cluster, while proton transfer is not observed and NO₃^-(H₂O)_m is just a secondary product. The reaction enthalpy was determined using nanocalorimetry, revealing a quite exothermic charge transfer with -241 ± 69 kJ mol^-1. Ab initio molecular dynamics simulations indicate that proton transfer is an allowed reaction pathway, but the overall thermochemistry favors charge transfer.