Methyl sulfides, atmospheric

Chloroethyl methyl sulfide is a vesicant and must be handled with care. It boils at 140° under atmospheric pressure. 

Sulfides and disulfides can be produced by bacterial reactions in the marine environment. 2-Dimeth-ylthiopropionic 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). Further details are given in Chapter 11, Part 2. Methyl sulfide can also be produced by biological methylation of sulfide itself (HS ). Carbon radicals are not the initial atmospheric products from organic sulfides and disulfides, and the reactions also provide an example in which the rates of reaction with nitrate... 

Grosjean, D. Atmospheric reactions of ortho cresol gas phase and aerosol products, Atmos. Environ., 19(8) 1641-1652,1984. Grosjean, D. Photooxidation of methyl sulfide, ethyl sulfide, and methanethiol, Environ. Sci. Technol, 18(6) 460-468,1984a. Grosjean, D. Atmospheric reactions of styrenes and peroxybenzoyl nitrate, ScL Total Environ., 50 41-59, 1985. 

Caution. The reaction should be carried out in a well-ventilated hood and away from flames, since BMS, 1,3-butadiene, organoborane by-products, and methyl sulfide are flammable, odoriferous, and possibly toxic substances. BMS and the initial hydroboration product are sensitive to air and moisture. The inert atmosphere technique8 is therefore recommended. Peroxide-free tetrahydro-furan (THF) should be distilled from a small quantity of lithium tetrahydro-aluminate according to the procedures in Reference 8. BMS is a very concentrat-... 

A solution of 6.0 mL of borane-methyl sulfide complex (10M BH3 in methyl sulfide) in 45 mL THF was placed in a He atmosphere, cooled to 0 °C, treated with 12.6 g of 2-methylbutene, and stirred for 1 h while returning to room temperature. To this there was added a solution of the impure 3,4-diethoxy-5-methylthiostyrene in 25 mL THF. This was stirred for 1 h during which time the color deepened to a dark yellow. The excess borane was destroyed with about 2 mL MeOH (all this still in the absence of air). There was then added 11.4 g elemental iodine followed by a solution of 2.4 g NaOH in 30 mL of boiling MeOH, added over the course of 10... 

A solution of 10 mL of borane-methyl sulfide complex (10 M BH3 in methyl sulfide) in 75 mL THF was placed in a He atmosphere, cooled to 0 °C, treated with 21 mL of 2-methylbutene, and stirred for 1 h while returning to room temperature. This was added directly to the crude 4-... 

Mercury occurs in soils predominantly in the +2 oxidation state. Elemental Hg in the atmosphere is oxidized to Hg + and deposited in rainfall. It is a strong chalcophile and under anaerobic conditions forms the extremely insoluble sulfide cinnabar (HgS, pK = 52.7). Nonetheless it is not entirely immobilized under anaerobic conditions because it is reduced to volatile Hg° or methylated to volatile methyl mercury compounds by microbial action, and so returned to the atmosphere. The methylation is mediated by various bacteria, especially methanogens, through the reactions ... 

Biogenic processes, however, emit reduced forms of sulfur, including dimethyl sulfide and hydrogen sulfide, with lesser amounts of carbon disulfide (CS2), dimethyl disulfide (CH3SSCH3), carbonyl sulfide (COS), and methyl mercaptan (Cl I3SH). These reduced sulfur compounds are then oxidized in the atmosphere as described in detail in Chapter 8.E. 

The worlds oceans cover approximately 70% of the surface of the earth, and may play a significant role in the transport of volatile sulfur compounds from marine, coastal and estuarine environments to the atmosphere. These compounds include hydrogen sulfide, HjS, carbonyl sulfide (COS), carbon disulfide, (CSA methyl mercaptan (CH3SH), dimethyl sulfide, (CH3SCH3), (DMS), and dimethyl disulfide (CH3SSCH3) (1). Although it was initially thought that H2S was the major compound involved in this transport (2), more recent evidence indicates that DMS accounts for most of the sulmr transferred from marine environments to the atmosphere (2). 

Biogenic Sulfur Emissions from the Ocean. The ocean is a source of many reduced sulfur compounds to the atmosphere. These include dimethylsulfide (DMS) (2.4.51. carbon disulfide (CS2) (28). hydrogen sulfide (H2S) (291. carbonyl sulfide (OCS) (30.311. and methyl mercaptan (CH3SH) ( ). The oxidation of DMS leads to sulfate formation. CS2 and OCS are relatively unreactive in the troposphere and are transported to the stratosphere where they undergo photochemical oxidation (22). Marine H2S and CH3SH probably contribute to sulfate formation over the remote oceans, yet the sea-air transfer of these compounds is only a few percent that of DMS (2). 

Hydrogen sulfide is acted on in the body by methylation with thiol S-methyl transferase. The initial product is methanethiol, HSCH3, which is also quite toxic. A second methylation produces dimethylsulfide, H2CSCH3. (Of some interest is the fact that dimethylsulfide is the major volatile sulfur compound released to the atmosphere from oceans, where it is produced by the action of marine microorganisms.)... 

WiUiams 1., Wang N.-Y., Cicerone R. 1., Yagi K., Kurihara M., and Terada E. (1999) Atmospheric methyl halides and dimethyl sulfide from cattle. Global Biogeochem. Cycles 13, 485-491. 

---