Hydroxyl radical-initialized polymerization and degradation of N-vinylpyrrolidone in lipid and aqueous environments

Absolute rate constants and degradation efficiencies for hydroxyl radical and hydrated electron reactions with four different sulfa drugs in water have been evaluated using a combination of electron pulse radiolysis/absorption spectroscopy and steady-state radiolysis/high-performance liquid chromatography measurements. For sulfamethazine, sulfamethizole, sulfamethoxazole, and sulfamerazine, absolute rate constants for hydroxyl radical oxidation were determined as (8.3 +/- 0.8) x 10(9), (7.9 +/- 0.4) x 10(9), (8.5 +/- 0.3) x 10(9), and (7.8 +/- 0.3) x 10(9) M(-1) s(-1), respectively, with corresponding degradation efficiencies of 36% +/- 6%, 46% +/- 8%, 53% +/- 8%, and 35% +/- 5%. The reduction of these four compounds by their reaction with the hydrated electron occurred with rate constants of (2.4 +/- 0.1) x 10(10), (2.0 +/- 0.1) x 10(10), (1.0 +/- 0.03) x 10(10), and (2.0 +/- 0.1) x 10(10) M(-1) s(-1), respectively, with efficiencies of 0.5% +/- 4%, 61% +/- 9%, 71% +/- 10%, and 19% +/- 5%. We propose that hydroxyl radical adds predominantly to the sulfanilic acid ring of the different sulfa drugs based on similar hydroxyl radical rate constants and transient absorption spectra. In contrast, the variation in the rate constants for hydrated electrons with the sulfa drugs suggests the reaction occurs at different reaction sites, likely the different heterocyclic rings. The results of this study provide fundamental mechanistic parameters, hydroxyl radical and hydrated electron rate constants, and degradation efficiencies that are critical for the evaluation and implementation of advanced oxidation processes (AOPs).

Hydroxyl radical

Solvated electron

10.1021/jp073990k

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Citations (152)

Characterization of the Reaction Rate Coefficient of DNA with the Hydroxyl Radical

Radiation Research (1996)

Jamie R. Milligan C. C. L. Wu J Y Ng José Miguel Aguilera John F. Ward

Using agarose gel electrophoresis, we have measured the yield of single-strand breaks (SSBs) induced by 137Cs gamma irradiation in a variety of plasmid DNA substrates ranging in size from 2.7 kb to 38 kb irradiated in aerobic aqueous solution in the presence of the hydroxyl radical scavenger dimethyl sulfoxide (DMSO). Under these conditions DNA SSBs are caused mainly by the hydroxyl radical. Using the competition between DMSO and DNA for the hydroxyl radical, we have estimated the rate coefficient for the reaction of the hydroxyl radical with DNA. The results cannot be characterized by conventional steady-state competition kinetics. However, it is possible to describe the second-order rate constant for the reaction as a function of the scavenging capacity of the solution. The second-order rate constant increases with increasing scavenging capacity, rising from about 5 x 10(8) dm3 mol-1 s-1 at 10(5) s-1 to about 10(10) dm3 mol-1 s-1 at 10(10) s-1. This dependence of the second-order rate constant on the scavenging capacity appears to be more pronounced for larger plasmids.

Hydroxyl radical

Scavenger

Agarose

10.2307/3579551

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Citations (33)

Homo- and Copolymers of N-Acryloylpyrrolidine and N-Vinylpyrrolidone as Kinetic Inhibitors of Hydrate Formation

Chemistry and Technology of Fuels and Oils (2011)

Anton P. Semenov П. А. Гущин Е. В. Иванов В. А. Винокуров Dmitriy A. Sapozhnikov

N-Vinylpyrrolidone

Proton NMR

10.1007/s10553-011-0243-x

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Kinetics and Mechanism of the Oxidation of Dimedone by Alkaline Permanganate

Synthesis and Reactivity in Inorganic and Metal-Organic Chemistry (1999)

Rafeek G. Panari Sharanappa T. Nandibewoor

Abstract The kinetics of oxidation of dimedone (DM) by permanganate in low and high alkali concentrations at a constant ionic strength has been studied spectrophotometrically. The reaction seems to proceed by two different mechanisms. At higher concentrations of alkali the reaction exhibits first, less than unity and zero order dependence of the rate on [permanganate ion], [DM] and [alkali], respectively, while at lower concentrations of alkali, all the orders are the same except for [OH−] the order of [OH″] is less than unity. In both the cases of [OH−], the. initial addition of products does not affect the rate significantly, while an increase in ionic strength and decrease in dielectric constant enhance the rate of the reaction. Plausible mechanisms consistent with the kinetic data were proposed and constants involved in the mechanisms have been evaluated. There is good agreement between observed and calculated rate constants at varying conditions of the experiments. The activation parameters with respect to the slow step of the mechanism have been computed.

Permanganate

Dimedone

Reaction rate

10.1080/00945719909351717

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Citations (4)