Hydrogen bonding in the hydroxysulfinyl radical-formic acid-water system: A theoretical study

Oxidation of HOSO˙ by O2 (3Σg-): a key reaction deciding the fate of HOSO˙ in the atmosphere

In the present work, we have studied the oxidation of HOSO˙ by O₂ (³Σ_g^-) employing quantum chemical and kinetic calculations. The present work reveals that HOSO˙ + O₂ (³Σ_g^-) is a barrierless reaction which proceeds through a stable hydrogen-bonded complex. The estimated atmospheric lifetime of HOSO˙ in the presence of O₂ (³Σ_g^-) is found to be several orders of magnitude less compared to the other oxidation paths of HOSO˙, suggesting that the oxidation of HOSO˙ by O₂ (³Σ_g^-) might be the most dominant oxidation path of HOSO˙ in the atmosphere.

Oxidation of HOSO˙ by Cl˙: a new source of SO2 in the atmosphere?

In the present work, we have studied the formation of SO₂ in the atmosphere from the oxidation of HOSO˙ by Cl˙ at the CCSD(T)/aug-cc-pV(+d)TZ//MP2/aug-cc-pV(+d)TZ level of theory. The present work reveals that the title reaction is a barrierless reaction that proceeds through a stable intermediate sulfurochloridous acid having a stabilization energy of ∼-56.5 kcal mol^-1. The rate constant values within the temperature range of 213-400 K indicate that the rate of HOSO˙ + Cl˙ = SO₂ + HCl reaction does not change much with the change in temperature. Besides, the reaction was also found to be insensitive towards pressure change. Interestingly, the relative rate of HOSO˙ + Cl˙ reaction with respect to HOSO˙ + OH˙ reaction indicates that HOSO˙ + Cl˙ is always much slower than HOSO˙ + OH˙ reaction, within the temperature range of 213-400 K.