A pulsed laser photolysis-pulsed laser induced fluorescence technique has been employed to measure rate coefficients for the OH initiated oxidation of methylethyl sulfide (MES) and diethylsulfide (DES). In the absence of oxygen and at low sulfide concentrations we measure rate coefficients that are independent of pressure and temperature. At high sulfide concentrations and a temperature of 245 K, we observed the equilibration of MESOH and DESOH adducts over the pressure range 100-600 Torr. In the presence of O2 the observed rate coefficients show a dependence on the O2 partial pressure. We measured the dependence of the overall rates of oxidation on the partial pressure of O2 over the temperature range 240-295 K and at 200 and 600 Torr total pressures. All observations are consistent with oxidation proceeding via a two channel oxidation mechanism involving abstraction and addition channels, analogous to that observed in the OH initiated oxidation of dimethylsulfide (DMS). Structures and thermochemistry of the MESOH and DESOH adducts were calculated and all results compared to those for DMS. Calculated bond strengths of adducts increase with alkyl substitution but are comparable to that of the DMSOH adduct and are consistent with experimental observations.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry