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

Abstract

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.

Electron-triggered chemistry in HNO3/H2O complexes

“…Its presence can be explained by (H 2 O) n (HNO 3 ) m – dissociation into OH – + NO 2 , with NO 2 not forming strong hydrogen bonds. This would be in line with our recent work, 38 where OH – formation is observed in binary collisions of hydrated electrons with HNO 3 in the gas phase. Electron attachment to a neutral (H 2 O) n HNO 3 cluster would form the same initial state, a hydrated valence-bound HNO 3 , which quickly undergoes O–N bond cleavage to form (H 2 O) n OH – .…”

“…As shown previously, it is more exothermic than the (H 2 O) n NO 2 – channel due to the stronger interaction of water with OH – than with the NO 2 – ion. 38 If more than one HNO 3 molecule is present in the neutral complex, the OH – anion reacts rapidly with HNO 3 and forms NO 3 – , reactions (6) and (9).…”

Carbon-carbon bond formation in the reaction of hydrated carbon dioxide radical anions with 3-butyn-1-ol

“…Previous comparisons to literature thermochemistry illustrate that the method works well, provided a sufficient number of data sets is analyzed so that some averaging is possible [49,65,73,94,95].…”

Mass spectrometry of aerosol particle analogues in molecular beam experiments

“…The (H 2 O) m products were observed only as minor products. In comparison to the free electron attachment to the gas‐phase HNO 3 molecule, in the reaction with the solvated electron the competition between OH and NO 2 for the electron was won by OH due to the high hydration enthalpy of OH − …”