We have studied the effect of different surfactants on the rate of diethyl sulfide (Et 2 S) oxidation by hydrogen peroxide and peroxymonocarbonate in aqueous solutions. In all the studied cases, the rate of the reaction between Et 2 S and H 2 O 2 decreases as the surfactant concentration increases. The reaction of Et 2 S with HCO 4 − is catalyzed by cationic surfactants and inhibited by neutral and anionic surfactants.A very important endeavor is the search for new systems for rapid oxidation of organic sulfides, which are active components of toxic agents. This task involves solving two fundamental problems: replacing the toxic and aggressive derivatives of hypochlorous acid widely used for disposal of sulfides [1], and selecting solvents that on the one hand make it possible to considerably increase the solubility of toxic sulfides (often practically insoluble in water) and on the other hand to preserve their fast oxidation rate.One promising route to solving the first problem is activation of hydrogen peroxide with formation of peroxy acids, which have high activity in oxidation of sulfides. Bicarbonates [2], silicates [3], nitrites [4], molybdates [5, 6], phthalates [7], and other compounds can be used as the H 2 O 2 activators. Water-alcohol mixtures are used to improve the solubility of the sulfides [2].Recently [8] we studied the bicarbonate-catalyzed oxidation of diethyl sulfide (Et 2 S), modeling 2,2-dichloroethyl sulfide (mustard gas), by hydrogen peroxide in water and in aqueous alcoholic media of variable composition. We established that at pH 7-9, the reaction includes intermediate formation of peroxymonocarbonate:(1)The value of the equilibrium constant for peroxymonocarbonate formation (K (1) ≈ 27) is the same for aqueous and aqueous alcoholic media [2,8]. The rate constant for the reaction (k (2) ) is about 100 times higher than the corresponding value for oxidation of Et 2 S by hydrogen peroxide. In aqueous alcoholic media, the rates of both the catalytic route (with HCO 4 − ) andthe noncatalytic route (with H 2 O 2 ) are slowed down with an increase in the alcohol concentration and in the order HOC 2 H 4 OH > i-PrOH > t-BuOH, but the ratio of the rates is preserved.
Data on the kinetics, kinetic isotope effects, substrate selectivity, and activation parameters for the first step of oxidation of alkylbenzenes by permanganate in acidic aqueous solutions are surveyed. The MnO4-. HMnO.~. and lVlnO3" species serve as oxidants at different acidities. The increase in the positive charge in this series enhances the electrophilicity of the reagent, which manifests itself as an increase in the reaction rate and a change in the site of attack on the atkylbenzene molecule (either the aromatic ring or C-H bond in the alkyl group). The oxidation of the alkyl C--H bonds in alkylbenzenes and in alkanes follows similar mechanisms, while the attack on the aromatic ring proceeds via the electrophilic aromatic substitution mechanism with a transition state intermediate between the charge transfer complex and r
Relative reactivity of alkane and alkylbenzene oxidation by peroxynitrite has been determined in acidic aqueous solutions. The observed data are explained assuming that the reaction simultaneously proceeds in both the gas and the liquid phases. The selectivity in the gas phase was found to be very similar to that of discrete hydroxyl radicals. The ability of peroxynitrite to react with organic substrates in the gas phase suggests that similar processes may occur in lipophilic media. The reaction mechanism and implication for lipid peroxidation are discussed.
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