Hydroxyl radical sulfur dioxide reaction

Four IR absorption bands have been identified in the spectrum of the hydroxysulfonyl radical (HOSO 2) which has been obtained by the reaction of hydroxyl radicals with sulfur dioxide in argon matrix at 11 K16. The observed bands at 3539.9 and 759.5 cm 1 have been assigned to O—H and S—OH stretching modes while the bands at 1309.2 and 1097.3 cm-1 have been assigned to the asymmetric and symmetric stretching modes of the double bonded S02 moiety. These data are consistent with the theoretical prediction on the geometry of the hydroxysulfonyl radical12. 

Chemical radicals—such as hydroxyl, peroxyhydroxyl, and various alkyl and aryl species—have either been observed in laboratory studies or have been postulated as photochemical reaction intermediates. Atmospheric photochemical reactions also result in the formation of finely divided suspended particles (secondary aerosols), which create atmospheric haze. Their chemical content is enriched with sulfates (from sulfur dioxide), nitrates (from nitrogen dioxide, nitric oxide, and peroxyacylnitrates), ammonium (from ammonia), chloride (from sea salt), water, and oxygenated, sulfiirated, and nitrated organic compounds (from chemical combination of ozone and oxygen with hydrocarbon, sulfur oxide, and nitrogen oxide fragments). ... 

Once sulfur dioxide has escaped into the atmosphere, it undergoes a series of reactions by which it is converted to sulfuric acid. Those reactions are somewhat complex and may follow at least three different courses. In the first of these reaction sequences, sulfur dioxide reacts with hydroxyl radicals in the atmosphere in the presence of some metallic catalyst (M) to form the bisulfite radical (HSO3 ) ... 

Sulfuric acid. New particle formation involving H2SO4 has been investigated most intensively because there is strong evidence that sulfuric acid can be an important particle precursor. Gaseous sulfuric acid is formed via the oxidation of sulfur dioxide (SO2) by hydroxyl radical in the following multistep reaction ... 

Most of the releases of carbonyl sulfide to the environment are to air, where it is believed to have a long residence time. The half-life of carbonyl sulfide in the atmosphere is estimated to be 2 years. It may be degraded in the atmosphere via a reaction with photochemically produced hydroxyl radicals or oxygen, direct photolysis, and other unknown processes related to the sulfur cycle. Sulfur dioxide, a greenhouse gas, is ultimately produced from these reactions. Carbonyl sulfide is relatively unreactive in the troposphere, but direct photolysis may occur in the stratosphere. Also, plants and soil microorganisms have been reported to remove carbonyl sulfide directly from the atmosphere. Plants are not expected to store carbonyl sulfide. 

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. 

A wide variety of interrelated homogenous gas-phase, solution-phase, and heterogenous chemistry may ultimately result in oxidation of SO2 to sulfuric acid in DUV exposure tools. The three main possible reaction pathways for the oxidation of sulfur dioxide to sulfuric acid in the exposure chamber may include (i) direct oxidation of sulfur dioxide by stable atmospheric oxygen, (ii) catalyzed oxidation of sulfur dioxide by metal ions, and (iii) photochemical oxidation of sulfur dioxide by ozone and hydroxyl radical. 

The reaction is self-catalyzed and irradiation can be cut off after the process has started. Free radicals can be produced by UV light (with optional water), ozone, X- or y-ray, and acetic anhydride or chlorine. The main intermediates are thus sulfur dioxide in its triplet state ( SOp alkyl, R hydrogenosulfonyl, HSO alkanesulfonyl, RSO alkanepersulfonyl, RSOj-O-O alkanesulfony-loxy, RS02-0 and hydroxyl, OH radicals and alkaneperoxysulfonic acid. Since RSO is the most stable free radical, the most probable chain rupture reaction is ... 

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)... 

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