Hydroxyl radical dimethyl sulfide reaction

Figure 4-13 shows an example from a three-dimensional model simulation of the global atmospheric sulfur balance (Feichter et al, 1996). The model had a grid resolution of about 500 km in the horizontal and on average 1 km in the vertical. The chemical scheme of the model included emissions of dimethyl sulfide (DMS) from the oceans and SO2 from industrial processes and volcanoes. Atmospheric DMS is oxidized by the hydroxyl radical to form SO2, which, in turn, is further oxidized to sulfuric acid and sulfates by reaction with either hydroxyl radical in the gas phase or with hydrogen peroxide or ozone in cloud droplets. Both SO2 and aerosol sulfate are removed from the atmosphere by dry and wet deposition processes. The reasonable agreement between the simulated and observed wet deposition of sulfate indicates that the most important processes affecting the atmospheric sulfur balance have been adequately treated in the model. 

CASRN 75-18-3 molecular formula C2H6S FW 62.14 Chemical/Physical MacLeod et al. (1984) studied the reaction of hydroxyl radicals ( limiting reagent ) with dimethyl sulfide in a discharge flow reactor. The rate constants for this reaction were 9.2 x 10 and 7.8 x 10 cm /molecule-sec at 100 and 300 °C, respectively. 

An example in which formation of a carbon radical is not the initial reaction is provided by the atmospheric reactions of organic sulfides and disulfides. They also provide an example in which rates of reaction with nitrate radicals exceed those with hydroxyl radicals. 2-dimethylthiopropionic acid is produced by algae and by the marsh grass Spartina alternifolia, and may then be metabolized in sediment slurries under anoxic conditions to dimethyl sulfide (Kiene and Taylor 1988), and by aerobic bacteria to methyl sulfide (Taylor and Gilchrist 1991). It should be added that methyl sulfide can be produced by biological methylation of sulfide itself (HS ) (Section 6.11.4). Dimethyl sulfide — and possibly also methyl sulfide — is oxidized in the troposphere to sulfur dioxide and methanesulfonic acids. 

Atkinson R, Perry RA, Pitts JN Jr. 1978. Rate constants for the reaction of hydroxyl radicals with carbonyl sulfide, carbon disulfide and dimethyl thioether over the temperature range 299-430 K. Chem Phys Lett 54 14-18. 

Hatakeyama, S., Okuda, M., Akimoto, H. Formation of sulfur dioxide and methanesulfonic acid in the photooxidation of dimethyl sulfide in the air. Geophys. Res. Lett. 9, 583-586 (1982) Hatakeyama, S., Washida, N., Akimoto, H. Rate constants and mechanisms for the reaction of hydroxyl (OD) radicals with acetylene, propyne, and 2-butyne in air at 297 2 K. J. Phys. Chem. 90, 173-178 (1986)... 

---