Structure, Stability, and Reactivity of Cationic Hydrogen Trioxides and Thermochemistry of their Neutral Analogs. A Fourier-Transform Ion Cyclotron Resonance Study

Abstract

The kinetics and the reaction patterns of the HO3 + and H2O3 + ions toward a variety of inorganic and organic substrates have been investigated by using Fourier-transform ion cyclotron resonance (FT-ICR) spectrometry. The thermochemistry of the HO3 + and H2O3 + ions is evaluated from correlations between their proton transfer (PT) efficiencies and the proton affinity (PA) of the selected substrates. Similarly, thermochemical data on HO3 and H2O3 species are inferred from a comparison between the electron transfer (ET) efficiencies of their cationic counterparts and the standard ionization energies (IE) of the substrates. Thus, in striking contrast with most literature theoretical and empirical estimates, an experimental value of −1 ± 5 kcal mol-1 is obtained for the standard heat of formation of HO3. Accordingly, ground-state HO3 (2A) is thermochemically stable toward dissociation to HO(2Π) and O2(3Σg -), and therefore, its existence as a true intermediate in key ionic reactions occurring in the upper atmosphere cannot be excluded. The standard formation enthalpy of H2O3 + (198 ± 5 kcal mol-1) is evaluated by two independent approaches, while that of the HOOOH neutral molecule is estimated as ≤−26 kcal mol-1. The HO3 + ion displays a variegated chemistry. Depending of the nature of the reactive centers of the neutral substrate, the HO3 + ion may react as a Brønsted or a Lewis acid, as an oxenium ion or an oxygen-centered free radical. When all these pathways are thermochemically precluded, as with CO, a ligand swiching process takes place in HO3 + to give the CHO2 + ion, which may promote a three-step acid-catalyzed cycle for the O3 oxidation of CO to CO2 and O2. Likewise, the less reactive H2O3 + ion undergoes ligand swiching by water.

Ab initio theoretical calculation and potential energy surface for ground-state HO3

“…They are 6.49 and 5X34 kcal mol À1 lower than the HO O 2 dissociation limit, respectively. These values are comparable with the experimental estimate of 10 AE 5 kcal mol À1 [12]. Note that the theoretical values represent absolute energies without zeropoint energy corrections.…”

“…Although Dupuis et al [6] predict HO 3 to be stable relative to the HO O 2 dissociation limit from the MC(DZP) method, most high level theoretical calculations [4,7,10] suggest such a species to be metastable. Recently, the stability problem has been solved by two experimental measurements [1,12]. The Fourier-transform ion cyclotron resonance mass spectrometry [12] study shows that the HO 3 molecule is relatively stable by 10 AE 5 kcal mol À1 with respect to HO O 2 .…”

“…Recently, the stability problem has been solved by two experimental measurements [1,12]. The Fourier-transform ion cyclotron resonance mass spectrometry [12] study shows that the HO 3 molecule is relatively stable by 10 AE 5 kcal mol À1 with respect to HO O 2 . In turn, Cacace et al [1] detected directly a stable HO 3 molecule using neutralization±reionization and neutralization±reionization/collisionally activated dissociation mass spectrometry.…”

Evidence for the production of trioxygen species during antibody-catalyzed chemical modification of antigens

“…The hydrotrioxide radical has been postulated to be an important intermediate in atmospheric processes (16), but it was not clear whether after formation it would dissociate immediately into 3 O 2 and HO • (17,18). However, HO 3 • has recently been detected experimentally by both Speranza (19) and Cacace and coworkers (20,21) using Fourier-transform ion cyclotron resonance mass spectrometry and neutralizationreionization mass spectrometry, respectively, and its lifetime has been calculated to be of the order of microseconds. Our own qualitative chemical reasoning as well as quantum chemical calculations point to the potential of the HO 3 • or the [HO 2…”

An Evaluation of Gas Phase Enthalpies of Formation for Hydrogen-Oxygen (HxOy) Species

“…The first measurement of its gas phase enthalpy of formation was derived indirectly from correlations in electron transfer efficiencies of the positive ion HO 3 + with the ionization energies of a series of neutral electron donors by Speranza (1996) [165]. This value had a very high uncertainty (about 20 kJ mol −1 ).…”