Exploring the chemical fate of the sulfate radical anion by reaction with sulfur dioxide in the gas phase

Abstract

Abstract. The gas phase reaction between SO4−(H2O)n and SO2, n = 0–2, is investigated using ab initio calculations and kinetic modelling. Structures of reactants, transition states and products are reported. Our calculations predict that the SO2SO4−(H2O)n cluster ion, which is formed upon SO2 and SO4−(H2O)n collision, can isomerize to SO3SO3−(H2O)n. The overall reaction is SO2 oxidation by the SO4−(H2O)n anionic cluster. The results show that SO4−(H2O)n is a good SO2 oxidant, especially at low relative humidity, with a reaction rate constant up to 1.5 × 10−10 cm3 molecule−1s−1. At high relative humidity, instead, the re-evaporation of SO2 from the SO2SO

Theoretical Study of Reactions between Oxygen-Centered Radicals (•OH and SO4•-) and Vinyl Monomers in Aqueous Phase

“…Calculated rate coefficients in Table are slightly overestimated both in gas and aqueous phases, on average by factors of 3.7 and 4.6, respectively. Underestimation of kinetic barriers is a known occurrence with DFT . However, hybrid and meta‐hybrid functionals such as B3LYP and M06‐2X provide a large improvement, particularly the M06‐2X functional, which exhibits an excellent performance on the calculation of standard thermochemistry properties .…”

“…The exploration of this new functional was motivated by Jensen's theoretical work, in which it is pointed out that modeling of radical anions, such as SO 4 • — , must make use of functionals including a high percentage of exact exchange correlation. Moreover , CAM‐B3LYP has been found to perform well in the kinetic description of SO 4 • — radicals reacting with sulfur dioxide and with water clusters …”

“…•radicals reacting with sulfur dioxide and with water clusters. [ 25 ] Vibrational frequencies are determined using the harmonic oscillator (HO) approximation to confi rm that optimized structures correspond to a local minimum (zero imaginary frequencies) or to a fi rst-order transition state (one imaginary frequency). Additionally, visualization of the imaginary vibrational mode is performed to corroborate that the transition state is connecting the right minima.…”

“…Underestimation of kinetic barriers is a known occurrence with DFT. [ 25 ] However, hybrid and meta-hybrid functionals such as B3LYP and M06-2X provide a large improvement, particularly the M06-2X functional, which exhibits an excellent performance on the calculation of standard thermochemistry properties. [ 23 ] Results in Table 1 show consistent agreement with experimental values.…”

A potential source of atmospheric sulfate from O<sub>2</sub><sup>−</sup>-induced SO<sub>2</sub> oxidation by ozone

“…The sulfate radical ion is believed to react with unsaturated compounds to form organosulfates, a major component of secondary organic aerosol (Surratt et al, 2007;Surratt et al, 2008;Schindelka et al, 2013). Using first-principles calculations, it was demonstrated that SO4acts as a catalyst in SO2 oxidation to SO3 by O3 in the gas-phase and hence, plays a role in atmospheric aerosol formation (Tsona et al, 2015;Tsona et al, 2016). The chemistry of O2SOOis largely unknown but, is potentially important for sulfur chemistry and atmospheric aerosol formation.…”