DFT investigations on the mechanisms and kinetics for the DMS + O₃ reaction

Abstract

The potential energy surface (PES) for the reaction of ozone with dimethyl sulfide (DMS) was calculated at the CCSD(T)/6‐311++G(3df,2pd)//M06‐2X/6‐311++G(d,p) levels of theory. Result shows that on the singlet PES the addition–elimination mechanism is dominant, and H‐abstraction mechanism is less competitive. The major channel starts from the addition of ozone and DMS leading to a weak intermediate IM1, which decomposes subsequently to DMSO and 1O2 via a barrier around 38.8 kJ/mol. With a barrier of 64.0 kJ/mol, the formation of HO3 + CH3SCH2 via H‐abstraction mechanism is subdominant. Besides, DMSO + 1O2 can take place further reactions to produce several products. The substitution mechanism was located on the triplet PES, however, with a rather high barrier it is negligible. Furthermore, the rate constants for the two channels leading to DMSO + 1O2 and HO3 + CH3SCH2 were calculated from 200 to 1000 K. The total rate constant is 1.13 × 10‐20 cm3·molecule‐1·s‐1 at 298 K and 1 atm, in good agreement with previous experimental data. The overall rate constants are positive temperature dependent in the whole temperature range.