Abstract
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.
Highlights
Dimethyl sulfide (CH3SCH3, dimethyl sulfide (DMS)) emitted by oceans is the main natural source of S-containing compound[1,2,3]
Enami et al.[18] have performed the experiment to investigate the OH radical-initiated oxidation of DMSO on the air-water interface. They have concluded that the methanesulfinic acid (MSIA) formed by the reaction OH + DMSO can further be oxidized by O3 or OH + O2, producing the methanesulfonic acid (MSA)
We found that only MSIA-I can react with OH radical to form CH3 radical and H2SO3, which is called as path 4 in this paper
Summary
Dimethyl sulfide (CH3SCH3, DMS) emitted by oceans is the main natural source of S-containing compound[1,2,3]. Tian et al.[28] have used DFT method to study the reaction of OH radical with methanesulfinic acid (MSIA) They found that the association-decomposition reaction (MSIA + OH → adduct → CH3SO2 + H2O → CH3 + SO2 + H2O) is more favorable than direct CH3 radical-abstraction reaction (MSIA + OH → adduct → CH3 + H2SO3 → CH3 + SO2 + H2O). Enami et al.[18] have performed the experiment to investigate the OH radical-initiated oxidation of DMSO on the air-water interface In their work, they have concluded that the MSIA (or dissociated methanesulfinic acid) formed by the reaction OH + DMSO can further be oxidized by O3 or OH + O2, producing the MSA. To our knowledge, the mechanism of the reaction MSIA + O3 has not been considered by the theoretical study
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