Methanesulfinic acid (MSIA) is an important intermediate in the oxidation of dimethyl sulfide (DMS) in the marine boundary layer. The oxidation of MSIA by ozone in the gas phase to form methanesulfonic acid (MSA) was investigated using theoretical calculations in this paper. Three pathways can be found for the reaction of MSIA with ozone. The highest energy barrier is 13.02 kcal mol−1 in the most favorable pathway. By comparing the reaction rate of MSIA + O3 with that of MSIA + OH, it can be concluded that the oxidation of MSIA by O3 to form MSA is of minor significance relative to its oxidation by OH radical in the gas phase. This study can provide some information for the theoretical and experimental studies in the significantly heterogeneous and aqueous-phase oxidation of MSIA by O3.
Abstract. The hydration of SO3 plays an important role in atmospheric
sulfuric acid formation. Some atmospheric species can be involved in and
facilitate the reaction. In this work, using quantum chemical calculations,
we show that oxalic acid, the most common dicarboxylic acid in the
atmosphere, can effectively catalyze the hydration of SO3. The
energy barrier of the SO3 hydration reaction catalyzed by oxalic acid
(cTt, tTt, tCt and cCt conformers) is a little higher or less than
1 kcal mol−1, which is lower than the energy barrier of
5.17 kcal mol−1 for water-catalyzed SO3 hydration. Compared
with the rates of the SO3 hydration reaction catalyzed by oxalic acid
and water, it can be found that in the upper troposphere the OA-catalyzed SO3 hydration can play an important role in
promoting SO3 hydration. It leads us to conclude that the
involvement of oxalic acid in SO3 hydration to form
H2SO4 is significant in the atmosphere.
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