Kinetics of the Thermal Decomposition of the CH₃SO₂ Radical and Its Reaction with NO₂ at 1 Torr and 298 K

Abstract

The kinetics and mechanism of the thermal decomposition of CH3SO2 and its reaction with NO2 have been investigated in a discharge flow reactor at 298 K and 1 Torr pressure using Cl/Cl2/CH3SH/NO2/He mixtures: CH3SO2 + NO2 → CH3SO3 + NO (3); CH3SO2 + M → CH3 + SO2 + M (4). The rate constants k3 and k4 were derived from the fitting of calculated and experimental kinetic profiles of CH3O and SO2 monitored by laser-induced fluorescence (LIF) analysis. CH3 produced in reaction 4 was rapidly converted into CH3O by reaction with NO2. The values obtained were k3 = (2.2 ± 1.1) × 10-12 cm3 molecule-1 s-1 and k4 = 510 ± 150 s-1. Errors are 1 standard deviation. The role of these reactions in the atmospheric oxidation mechanism of dimethyl sulfide is discussed.