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Titolo:
OH-Radical-induced oxidation of methanesulfinic acid. The reactions of themethanesulfonyl radical in the absence and presence of dioxygen
Autore:
Flyunt, R; Makogon, O; Schuchmann, MN; Asmus, KD; von Sonntag, C;
Indirizzi:
Max Planck Inst Strahlenchem, D-45470 Mulheim, Germany Max Planck Inst Strahlenchem Mulheim Germany D-45470 70 Mulheim, Germany Univ Notre Dame, Radiat Lab, Notre Dame, IN 46556 USA Univ Notre Dame Notre Dame IN USA 46556 iat Lab, Notre Dame, IN 46556 USA Univ Notre Dame, Dept Chem & Biochem, Notre Dame, IN 46556 USA Univ Notre Dame Notre Dame IN USA 46556 Biochem, Notre Dame, IN 46556 USA
Titolo Testata:
JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2
fascicolo: 5, , anno: 2001,
pagine: 787 - 792
SICI:
1472-779X(2001):5<787:OOOMAT>2.0.ZU;2-R
Fonte:
ISI
Lingua:
ENG
Soggetto:
N2O-SATURATED AQUEOUS-SOLUTIONS; PULSE-RADIOLYSIS; PEROXYL RADICALS; GAMMA-RADIOLYSIS; RATE CONSTANTS; REDUCTION POTENTIALS; ORGANIC SULFIDES; ONE-ELECTRON; METHYL; OZONE;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
40
Recensione:
Indirizzi per estratti:
Indirizzo: von Sonntag, C Max Planck Inst Strahlenchem, Stiftstr 34-36,POB 101365, D-45470 Mulheim, Germany Max Planck Inst Strahlenchem Stiftstr 34-36,POB 101365 Mulheim Germany D-45470
Citazione:
R. Flyunt et al., "OH-Radical-induced oxidation of methanesulfinic acid. The reactions of themethanesulfonyl radical in the absence and presence of dioxygen", J CHEM S P2, (5), 2001, pp. 787-792

Abstract

Hydroxyl radicals were generated radiolytically in N2O-saturated solutions. As shown by pulse radiolysis, methanesulfinic acid reacts with . OH (k = 5.3x10(9) dm(3) mol(-1) s(-1)) and N-3(.) giving rise to an intermediate which has an absorption maximum at 330 nm (G epsilon approximate to5.2x10(-5)m(2) mol(-1)). This is attributed to the methanesulfonyl radical, CH3S(O)O-.. Pulse radiolysis with conductometric detection indicates that CH3S(O)O-. is formed in only similar to 80% yield. This is confirmed by scavenging experiments with Fe(CN)(6)(4-), ascorbate and sulfite, which are oxidised byCH3S(O)O-. with rate constants of similar to 2x10(9) dm(3) mol(-1) s(-1). Steady-state radiolysis of methanesulfinic acid shows that methanesulfonic acid is the major product (G=2.1x10(-7) mol J(-1)). Further products are sulfate (0.7x10(-7) mol J(-1)), methane (0.3x10(-7) mol J(-1)), ethane (0.08x10(-7) mol J(-1)) and dimethyl sulfone (not quantified). It is suggested that an OH-adduct is formed initially which mainly eliminates OH-, but also decomposes yielding (CH3)-C-. and bisulfite. The formation of methanesulfonic acid can be explained by a disproportionation of the methanesulfonyl radicals via recombination and subsequent hydrolysis. In the presence of dioxygen, a chain reaction occurs whereby 2 mol methanesulfonic acid are formed per 1 mol dioxygen consumed. G(methanesulfonic acid)approximate to 250x10(-7) mol J(-1) was found to be independent of dose rate (0.011-0.165 Gy s(-1)), methanesulfinic acid concentration [(0.1-4)x10(-3) mol dm(-3)] and dioxygen concentration. An efficient chain process was also observed upon electron beam irradiation [G(methanesulfonic acid)approximate to 200x10(-7) mol J(-1) at 0.8 Gy per pulse and 75x10(-7) mol J(-1) at 9 Gy per pulse (pulse duration 2 mus)]. It is proposed that the oxidation of the substrate by the methylsulfonylperoxyl radical, CH3S(O-2)OO., to give the strongly oxidising CH3S(O-2)O-. radical, initiates the chain reaction, with the latter propagating the chain by reacting with a substrate molecule to give methanesulfonic acid and the methanesulfonyl radical. Branching and partial removal of the chain-carrying CH3S(O-2)O-. radicals by H-abstraction from the substrate is suggested as the likely path leading to chain termination. Oxidation of methanesulfinate by ozone (k=2x10(6) dm(3) mol(-1) s(-1)) occurs only by O-atom transfer, and an electron transfer that would start a chain reaction was not observed.

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Documento generato il 06/04/20 alle ore 08:25:09