Methanesulfonic acid, atmosphere

In a Schlenk tube equipped with a magnetic stirrer bar were placed (S,S)-1,2-bis(boranato(tert-butyl)methylphosphino)ethane (2) (131 mg) and dry toluene (4mL) under an argon atmosphere at 0°C. To this solution, trifluoro-methanesulfonic acid (0.22 mL) was added over a period of 5 minutes. 

Kreidenweis, S. M., and J. H. Seinfeld, Nucleation of Sulfuric Acid-Water and Methanesulfonic Acid-Water Solution Particles Implications for the Atmospheric Chemistry of Organosulfur Species, Atmos. Environ., 22, 283-296 (1988a). 

Nitrate clusters with H20 and/or HN03 such as N07(HN03) are common in the atmosphere (Perkins and Eisele, 1984). Proton transfer to such clusters can occur, but clearly, the trace gas must be more acidic than HNOv This limits the number of trace gases that can be ionized through this mechanism but includes the important atmospheric species H2S04 and methanesulfonic acid, CH3S03H (Tanner and Eisele, 1991 Viggiano, 1993). 

Figure 15.12. XH NMR spectra of aqueous soluble species from (A) coarse air particles with diameters of 33-4.7mm (pH 6.55) (B) fine air particles with diameters of 0.65-1.1 mm (pH 3.92). Compounds identified in the spectra include 1, acetic acid 2, monomethylamine 3, succinic acid 4, dimethylamine 5, methanesulfonic acid 6, methanol 7, monomethyl hydrogen sulfate 8, hydroxymethanesulfonic acid 9, phthalic acid 10, terephthalic acid. Reprinted from Suzuki, Y., Kawakami, M., and Akasaka, K. (2001). JH NMR application for characterizing water-soluble organic compounds in urban atmospheric particles. Environ. Sci. Technol. 35, 2656-2664, with permission from the American Chemical Society.

Once DMS is emitted into the atmosphere it will eventually be oxidized by OH or NO3 radicals to sulfur dioxide (SO2), methanesulfonic acid (MSA), and, via SO oxidation, to non-sea-salt sulfate (nss-S042 ) as major reaction products (e.g. 10.111. The Southern Ocean represents a relatively unpolluted marine environment. It offers a unique possibility to study the natural sulfur cycle in an atmosphere far remote from man-inhabited continents. 

Methanesulfonic acid, dimethyl sulfoxide and dimethyl sulfone are potential intermediates in the gas phase oxidation of dimethylsulfide in the atmosphere. We nave measured the rate of reaction of MSA with OH in aqueous solution using laser flash photolysis of dilute hydrogen peroxide solutions as a source of hydroxyl radicals, and using competition kinetics with thiocyanate as the reference solute. The rate of the reaction k (OH + SCN ) was remeasured to be 9.60 1.12 x 109 M 1 s 1, in reasonable agreement with recent literature determinations. The rates of reaction of the hydroxyl radical with the organosulfur compounds were found to decrease in the order DMSO (k = 5.4 0.3 x 109 M-i s 1) > MSA (k = 4.7 0.9 x 107 M l S 1) > DMS02 (k = 2.7 . 15 x 107 M 1 s ). The implications of the rate constant for the fate of MSA in atmospheric water are discussed. 

CH SOH is probably converted to CH3S03H (methanesulfonic acid) by reaction with O2 while the atmospheric fate of DMSO is unclear. 

At 298K our results demonstrate that reaction 1 in one atmosphere of air proceeds 70% via abstraction and 30% via (irreversible) addition. Photooxidation studies have been reported by Niki, et al. (18) and Hatakeyama and Akimoto (19), where 298K SO2 yields from OH initiated oxidation of CH3SCH3 were reported to be 22% and 21%, respectively. Large yields of methanesulfonic acid were observed in both studies. At present, there is insufficient information to allow SO2 production to be associated with either the abstraction... 

Dimethylsulfoxide can readily be removed onto particles and there it can undergo an efficient oxidation through to methanesulfonate. This adds a significant pathway to the gas-phase production of methanesulfonic acid, which is present largely in the submicron aerosol fraction. Peak summer concentrations are 0.6 0.3 nmol m and at times this can amount to almost a quarter of the non-seasalt sulfate in the remote marine atmosphere (Jourdain and Legrand, 2001). 

Water-soluble organic compounds in urban atmospheric particles can also contain organosulfur compounds. Methanesulfonic acid and hydroxymethanesulfonic acid have been found as the major organosulfur compounds in urban aerosols, most particularly in particles with the diameter range of 0.43-1.1 p.m. Monomethyl hydrogen sulfate has also been detected on urban particles from localities where no oil or coal power plant exist (Suzuki et al., 2001). 

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. 

The major product from the OH + DMS reaction is methanesulfonic acid, and the reaction scheme shown in Table 10-4 offers a simple route to its formation. CH3S03H is a condensable product that in the atmosphere becomes associated with aerosol particles. Panter and Penzhorn (1980) have demonstrated its presence in continental aerosols, while Saltzman et al. (1983) found it to occur also in the marine aerosol. Methanesulfonic acid is unstable in aqueous solution. Once associated with the aerosol, it becomes rapidly oxidized to sulfuric acid. 

A widespread marine source of S02 is required to explain these observations. In Section 10.2 it was shown that the oceans release hydrogen sulfide and dimethyl sulfide, and that both are rapidly oxidized in the atmosphere by reaction with OH radicals. The processes convert hydrogen sulfide fully to S02, whereas dimethyl sulfide yields primarily methanesulfonic acid, and S02 accounts for only 25% of all products. Let us see whether the oxidation of these compounds suffices to explain the S02 mixing ratios observed in marine air. For this purpose we assume steady-state conditions and use the lifetimes for H2S and DMS given in Table 10-2. The mixing ratio for S02 at the ocean surface then is... 

A series of poly(thioether ketone)s or poly(thioether ether ketone)s ( /inh = 0.1-0.73 dL/g) were synthesized by condensation of aromatic dicarboxylic acids with aryl compounds containing ether or sulfide structures using phosphorous pentoxide/methanesulfonic acid as the condensing agent and solvent. The polymers showed Tdio in the range of 420-485° C in air and nitrogen atmospheres (63). 

DMS is photochemically oxidized in the atmosphere to methanesulfonic and sulfuric acids. These strong acids contribute, along with nitric and organic acids, to the natural acidity of precipitation. Recent problems with acid rain have aroused interest in the anthropogenic and natural sources of volatile sulfur compounds (2). 

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