The reaction of methyl radicals with hydrogen peroxide

Ulański, Piotr; Merényi, Gábor; Lind, Johan; Wagner, Rita; Sonntag, Clemens von

doi:10.1039/a900686i

Cited by 20 publications

(35 citation statements)

References 26 publications

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“…The reaction of methyl radicals with hydrogen peroxide has been studied, [44] but the results given herein differ considerably from those previously reported for a system containing less DMSO [44] (10 À3 -10 À2 m vs. 0.10 m in this system). The rate constant of the abstraction of hydrogen atoms from hydrogen peroxide by the methyl radical has been reported [reaction (11)]: [44] …”

Section: Analysis Of Peroxidescontrasting

confidence: 74%

“…In the previous study (which used relatively low concentrations of DMSO), the production of methane increased with increasing concentration of hydrogen peroxide, but no catalytic effect had been observed. [44] The present results indicate that at relatively high concentrations of DMSO and low dose rates reaction (11) is followed by reaction (12) (pK a value of HO 2 C is 4.8 [45] ).…”

Section: Analysis Of Peroxidesmentioning

confidence: 86%

“…The rate constant of the abstraction of hydrogen atoms from hydrogen peroxide by the methyl radical has been reported [reaction (11)]: [44] …”

Section: Analysis Of Peroxidesmentioning

confidence: 99%

“…The increase in the concentration of sulfate ions is independent of dose rate and only dependent on the persulfate concentration. 2À , which will be followed by reaction (44). Table 4.…”

mentioning

confidence: 99%

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Mechanism of the Reaction of Radicals with Peroxides and Dimethyl Sulfoxide in Aqueous Solution

Herscu-Kluska

Masarwa

Saphier³

et al. 2008

Chemistry A European J

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The reactions of methyl and methylperoxyl radicals derived from dimethyl sulfoxide (DMSO) with hydrogen peroxide, peroxymonocarbonate (HCO4 (-)), and persulfate were studied. The major reaction observed for the hydroperoxides was the abstraction of the hydrogen atom by the radicals. The radicals interact with a lone pair of electrons on the peroxide to produce methanol and formaldehyde. Furthermore, the results indicate that in RO2H and RO2R', electron-withdrawing groups cause a considerable increase in the reactivity of the peroxides towards the radicals and not only towards nucleophiles. The HO2 (.)/O2 (.-) and CO3 (.-) radicals react with DMSO to produce methyl radicals. Thus, the formation of the (.)CH3 radicals in the presence of DMSO is not proof of the formation of the (.)OH radicals in the system. These reactions must be considered when radical processes, such as in biological and catalytic systems, are studied. Especially, the plausible role of HCO4 (-) ions in biological systems as a source of oxidative stress cannot be overlooked.

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Section: Analysis Of Peroxidescontrasting

confidence: 74%

Section: Analysis Of Peroxidesmentioning

confidence: 86%

“…The rate constant of the abstraction of hydrogen atoms from hydrogen peroxide by the methyl radical has been reported [reaction (11)]: [44] …”

Section: Analysis Of Peroxidesmentioning

confidence: 99%

“…The increase in the concentration of sulfate ions is independent of dose rate and only dependent on the persulfate concentration. 2À , which will be followed by reaction (44). Table 4.…”

mentioning

confidence: 99%

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Mechanism of the Reaction of Radicals with Peroxides and Dimethyl Sulfoxide in Aqueous Solution

Herscu-Kluska

Masarwa

Saphier³

et al. 2008

Chemistry A European J

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“…However, C 2 H 6 is, as expected, formed in very low quantities, with a C 2 H 6 /CH 4 ratio below 0.01. It has been shown that formation of C 2 H 6 by the recombination of methyl radicals occurs in water and depends on the experimental parameters 27,41,42 . In those studies, much higher C 2 H 6 /CH 4 ratios (40.1) were reported because of the fast kinetics (for example, Á OH radical formation by water radiolysis), generating a higher steady-state concentration of methyl radicals.…”

Section: Resultsmentioning

confidence: 99%

Abiotic methanogenesis from organosulphur compounds under ambient conditions

et al. 2014

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Methane in the environment is produced by both biotic and abiotic processes. Biomethanation involves the formation of methane by microbes that live in oxygen-free environments. Abiotic methane formation proceeds under conditions at elevated temperature and/or pressure. Here we present a chemical reaction that readily forms methane from organosulphur compounds under highly oxidative conditions at ambient atmospheric pressure and temperature. When using iron(II/III), hydrogen peroxide and ascorbic acid as reagents, S-methyl groups of organosulphur compounds are efficiently converted into methane. In a first step, methyl sulphides are oxidized to the corresponding sulphoxides. In the next step, demethylation of the sulphoxide via homolytic bond cleavage leads to methyl radical formation and finally to methane in high yields. Because sulphoxidation of methyl sulphides is ubiquitous in the environment, this novel chemical route might mimic methane formation in living aerobic organisms.

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Free-Radical-Induced Chain Breakage and Depolymerization of Poly(methacrylic acid): Equilibrium Polymerization in Aqueous Solution at Room Temperature

et al. 2000

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Hydroxyl radicals, generated by ionizing radiation in N2O saturated aqueous solutions, abstract H atoms from poly(methacrylic acid) at the methyl and methylene groups, and radicals 1 and 2 are formed, respectively. The reactions of the poly(methacrylic acid) radicals were investigated by pulse radiolysis (using optical and conductometric detection), EPR, product analysis, and kinetic simulations. The conductometric detection allowed us to measure the rate of chain scission and monomer release. Under conditions in which the polymer is largely deprotonated, the primary radical 1 abstracts a hydrogen (k= 3.5 x 10(2)s(-1)) from the methylene group, and this yields the more stable secondary radical 2. This radical undergoes chain scission by beta-fragmentation (k= 1.8 s(-1)), and the terminal (end-of-chain) radical 3 is formed. The polymer radicals terminate only slowly (2k= 80 dm3mol(-1)s(-1)). This allows effective depolymerization (depropagation) to take place (k=0.1 s(-1)). The yield of monomer release is higher than the original radical yield by up to two orders of magnitude. Once monomer is formed, it reacts with 3 (propagation, k= 15 dm3mol(-1)s(-1)), and a situation close to an equilibrium radical polymerization is approached. From these data, the equilibrium monomer concentration is calculated at 6.7 x 10(-3) mol dm(-3) at room temperature. The standard entropy of propagation is estimated at -185 to -150 J mol(-1)K(-1). Because the monomer reaches concentrations in the millimolar range, the *OH radicals increasingly react with monomers (results in oligomerization) rather than with the polymer. This effect is reflected by, for example, a lowering of chain-scission yields upon prolonged irradiation. In acid solutions, the decay of the polymer radicals becomes much faster (estimated at about 10(7)dm3mol(-1)s(-1) at pH3.5), and monomer release is no longer observed.

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The reaction of methyl radicals with hydrogen peroxide

Cited by 20 publications

References 26 publications

Mechanism of the Reaction of Radicals with Peroxides and Dimethyl Sulfoxide in Aqueous Solution

Mechanism of the Reaction of Radicals with Peroxides and Dimethyl Sulfoxide in Aqueous Solution

Abiotic methanogenesis from organosulphur compounds under ambient conditions

Free-Radical-Induced Chain Breakage and Depolymerization of Poly(methacrylic acid): Equilibrium Polymerization in Aqueous Solution at Room Temperature

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