The oxidation of methanol and 2-propanol by potassium peroxodisulphate in aqueous solution: Free-radical chain mechanisms elucidated by radiation-chemical techniques
01 Jan 1988-International Journal of Radiation Applications and Instrumentation. Part C. Radiation Physics and Chemistry (Pergamon)-Vol. 32, Iss: 2, pp 149-156
TL;DR: In this article, a curve-fitting procedure has been applied in order to extract mechanistic and kinetic information from product yield data in the presence of potassium peroxodisulphate.
About: This article is published in International Journal of Radiation Applications and Instrumentation. Part C. Radiation Physics and Chemistry.The article was published on 1988-01-01. It has received 13 citations till now. The article focuses on the topics: Qualitative inorganic analysis.
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TL;DR: The photolysis of S(2)O(8)(2-) was studied for the removal of acetic acid in aqueous solution and compared with the H2O(2)/UV system, suggesting that above this pH, competitive reactions with the carbon mineralized inhibit the reaction of the solute with SO(4)(-) and also ()OH radicals.
270 citations
TL;DR: The reactions of O2-.
Abstract: The reactions of O2-. in aqueous solutions of pyrogallol 1 and the antioxidant n-propyl gallate 2 have been studied. In both cases the initial reaction gives hydrogen peroxide and the corresponding phenoxyl radical (k(1 + O2-.) = 3.4 x 10(5), k(2 + O2-.) = 2.6 x 10(5) dm3 mol-1S-1). These phenoxyl radicals have been produced independently by reacting 1 and 2 with Br2-. and their spectra and first pKa values measured (pKa(phenoxyl radical from 1) = 5.1, pKa(phenoxyl radical from 2) = 4.1). It is necessary to correct the observed spectra for the contribution of the H-adducts, formed by the reaction of radiolytically produced H atoms with the substrates (k(1 + H) = 2.5 x 10(9), k(2 + H) = 3.8 x 10(9) dm3 mol-1 S-1). The H-adduct spectra are given. In the reactions of O2-. with the substrates the initial transient absorbances are characteristic of the phenoxyl radicals; however at longer times a new transient absorbing around 500 nm (epsilon congruent to 10(4) dm3 mol-1 cm-1) appears. This is believed to be the deprotonated hydroxy-orthoquinone, formed by the reaction of phenoxyl radicals with O2-. (k congruent to 1.5 x 10(8) dm3 mol-1 S-1, from kinetic curve-fitting). The absorbance due to the hydroxy-orthoquinones decays by first-order kinetics (1.6 x 10(2) in the case of 1 and 1.1 x 10(2) s-1 in the case of 2). This is thought to be mainly the result of the conversion of the hydroxy-orthoquinone into its hydrate. Similar experiments were carried out with catechol and ethyl protocatechuate. The chemistry appears to be similar to that of the pyrogallol derivatives. The rate constant for reaction of these compounds with O2-. is, however, only less than or equal to x 10(4) dm3 mol-1 s-1.
53 citations
TL;DR: In this paper, the pulse radiolysis technique was used to investigate free-radical-induced reactions of poly(vinyl alcohol) PVAL, poly(acrylic acid) PAA, poly (methacrylic acids) PMA, and hyaluronic acid, in dilute aqueous solution.
50 citations
TL;DR: In this paper, the authors reviewed the kinetics of the formation and decay of polymer-derived radicals in radiolysis of N2O-saturated aqueous solutions.
32 citations
TL;DR: The photobleaching of excited tris(2,2′‐bipyridyl)‐ruthenium(II), *Ru(bpy)32+, by peroxydis‐ulfate in the presence of DNA and a series of polynucleotides, mononucleosides, and purine or pyrimidine bases was studied in deoxygenated aqueous solution at room temperature.
Abstract: — The photobleaching of excited tris(2,2′-bipyridyl)-ruthenium(II), *Ru(bpy)32+, by peroxydis-ulfate in the presence of DNA and a series of polynucleotides, mononucleosides (uridine, cytidine, adenosine, guanosine), and purine or pyrimidine bases was studied in deoxygenated aqueous solution at room temperature. A reaction scheme is proposed which is confirmed by data obtained from mixing experiments with Ru(III) and bleaching measurements of Ru(II) using either continuous visible light or a nanosecond laser pulse (353 nm). The primary photobleaching step is the formation of Ru(bpy)32+ and the SO4- radical anion. In the presence of nucleic acids the two oxidizing species are formed in close proximity to the strand, since we used conditions where the Ru(bpy) 32+ ion is bound to the strand. Concerning the secondary reactions two clear cases (and several more complex cases) can be distinguished. On addition of uracil to the Ru(bpy)32+/S2O82- system the quantum yield for photobleaching is not significantly changed (φrel⋍ 0.95), whereas it drops to virtually zero for guanosine-containing substrates, including DNA. The former result is explained by a reaction of SO4- with uracil leading to theN–1 radical which oxidizes Ru(II) to Ru(IIl). In contrast, the guanine moiety reacts with Ru(III) converting it into Ru(II). Therefore, in the presence of S2O82- and a substrate carrying a guanine moiety, Ru(bpy32+ acts as a photocatalyst.
25 citations
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TL;DR: A program system is described for the integration of the rate equations resulting from large systems of elementary reactions, using the Gear integration method for this problem, which frequently may exhibit stiffness instability when other integration methds are employed.
Abstract: A program system is described for the integration of the rate equations resulting from large systems of elementary reactions. The Gear integration method is used for this problem, which frequently may exhibit stiffness instability when other integration methds are employed. No usage of the quasi-steady-state approximation is necessary. Ease in varying the reaction mechanism and simplicity of input structure are coupled with efficient execution and minimal demands for program storage as key features. The input–output structure, method of operation, and implementation are summarized, along with core storage requirements and execution times for trials using an IBM 360/44 computer.
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