OH-initiated oxidation

The SOJ radical anion is then oxidized to sulfate, i.e., S(VI), in a series of subsequent steps. These are analogous to the OH-initiated oxidation of S(IV) in solution discussed in more detail in the following chapter. 

Again, the chemistry is analogous to the OH-initiated oxidation of chloride and bromide in solution. The subsequent aqueous-phase chemistry for the halogens is summarized in the following chapter. 

Barnes, I., K. H. Becker, and I. Patroescu, FTIR Product Study of the OH Initiated Oxidation of Dimethyl Sulphide Observation of Carbonyl Sulphide and Dimethyl Sulphoxide, Atmos. Environ., 30, 1805-1814(1996). 

Our current understanding of the rates and mechanisms of the OH-initiated oxidation of several reduced sulfur compounds is reviewed with particular emphasis on recent studies in our laboratory. Important uncertainties are highlighted and directions for future research are suggested. 

HYNES AND WINE OH-Initiated Oxidation of Biogenic Sulfur Compounds 425... 

On the basis of our results, one might expect the end product yields from the OH-initiated oxidation of DMS to be strongly temperature dependent. No temperature dependent laboratoiy studies have been performed which would allow this hypothesis to be tested. However, atmospheric measurements suggest higher MSA-to-S02 yield ratios at higher latitudes (i.e. lower temperatures)... 

Subsequent steps in the OH-initiated oxidation of DMS have not been fully established. In the model reactions 1-3 have been considered sufficient to describe the oxidations. 

The major products of the photolysis of glycolaldehyde are HCHO and CO, methanol and OH production was also observed. Photolysis of glycolaldehyde was used as the OH source to measure the reaction rate constants of OH with a series of dienes by the relative method and to identify and quantify the oxidation products of the OH-initiated oxidation of propan-2-ol. HCHO is observed to be the major product of the OH-initiated oxidation of glycolaldehyde. The results indicate that the OH reaction and photolysis can compete as tropospheric sinks for glycolaldehyde.218... 

The mechanism and kinetics of the atmospheric oxidation of alkynes, initiated by OH radicals, have been studied particularly to determine the role of alkyne oxidation in tropospheric ozone formation. A general mechanism for OH-initiated oxidation of alkynes has been developed with the aid of thermodynamic calculations. In general, the significance of atmospheric alkynes to the formation of tropospheric ozone was found to be smaller than for alkanes and alkenes, due to the absence of the hydroxy peroxy-forming product channel in the OH-initiated atmospheric oxidation of alkynes.227... 

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... 

Monod A., L. Poulain, S. Grubert, D. Voisin and H. Wortham Kinetics of OH-initiated oxidation of oxigenated organic compounds in the aqueous phase new rate constants, stmcture-activity relationships and atmospheric implications, Environ. (2005) in press. 

Magneron, I., R. Thdvenet, A. Mellouki, Q. Le Bras, G.K. Moortgat and K. Wirtz A study of the photolysis and OH-initiated oxidation of acrolein and rrani-crotonaldehyde, J. Phys. Chem. A 106 (2002) 2526. 

Klotz, B., R. Volkamer, M.D. Hurley, M.P.S. Andersen, O.J. Nielsen, 1. Barnes, T. hnamura, K. Wirtz, K.EL Becker, U. Platt, T. J. WaUington, and N. Washida OH-initiated oxidation of benzene - Part n. Influence of elevated NOx concentrations. Physical Chemistry Chemical Physics, 4 (2002) 4399-4411. 

Volkamer, R., B. Klotz, I. Barnes, T. frnamura, K. Wirtz, N. Washida, K.H. Becker and U. Platt OH-initiated oxidation of benzene - Part I. Phenol formation under atmospheric conditions. Phys. Chem. Chem. Phys. 4(9), (2002) 1598-1610. 

The main observed produets of the OH-initiated oxidation of vinyl ethers in the presenee of NOx, were formaldehyde and formates (with molar yields of 80 % for eaeh). 

As in the OH-initiated oxidation of vinyl ether, the reactions of O3 with the same vinyl ethers lead mainly to formation of formates (molar yields of (70-90)%) and formaldehyde (molar yields of (20-10)%). Figure 2 shows an example of the concentration-time profiles of the reactants and products for the reaction of O3 with ethyl vinyl ether (C2H50CH H2). For methyl vinyl ether, hydroperoxymethyl formate and methanol were also observed as produets (Klotz et ai, 2004). 

Two channels are expected to occur in the OH-initiated oxidation of acetic acid ... 

CavaUi, F., H. Geiger, I. Bames and K. H. Becker FTIR kinetic, product, and modeling study of the OH-initiated oxidation of 1-butanol in air. Environ. Sci. Technol. 36 (2002) 1263-1270... 

For many years, the two-channel mechanism has been widely accepted as the operative mechanism for the OH-initiated oxidation of DMS, and the expressions for the rate coefficient and inferred branehing ratio recommended as the best currently available for mechanistic interpretation and atmospheric modelling purposes. 

Kinetic Study of the Temperature Dependence of the OH Initiated Oxidation... 

Williams, M.B., P. Campuzano-Jost, D. Bauer and A.J. Hynes Kinetie and meehanistie studies of the OH-initiated oxidation of dimethylsulfide at low temperature - a reevaluation of the rate eoeffieient and branehing ratio, Chem. Phys. Lett. 344 (2001), 61-67. 

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