Kinetics of oxidation of transition-metal ions by halogen radical anions. Part III. The oxidation of manganese(II) by dibromide and dichloride ions generated by flash photolysis

Laurence, Gerald S.; Thornton, Andrew T.

doi:10.1039/dt9730001637

Cited by 19 publications

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“…One-Electron Reduction Potential of (DMS) 2 •+ . In ref 17 the below equilibria were measured From these values and E 0 (Br 2 •-/2Br -) ) 1.62 V, 18,19 we obtain E 0 ((DMS) 2 •+ /2DMS) ) 1.37 V vs NHE. In the present work we attempted to determine this potential more directly by having the (DMS) 2•+ /2DMS couple equilibrate with N 3 • /N 3 -.…”

Section: Resultsmentioning

confidence: 94%

The Dimethylhydroxysulfuranyl Radical

1996

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By use of pulse radiolysis the one-electron reduction potentials, E 0(DMS•+/DMS) and E 0((DMS)2 •+/2DMS) (dimethyl sulfide, DMS) were determined to be 1.66 ± 0.03 and 1.40 ± 0.02 V vs NHE, respectively. DMS•+ was found to be in equilibrium with DMSOH• with a pK a = 10.2. The conditional equilibrium constant for the reaction DMSOH• + DMS ⇌ (DMS)2 •+ + OH- was found strongly dependent on both ionic strength and DMS concentration. In the thermodynamic limit this equilibrium constant is ≈1.3. The dimerization reaction DMS•+ + DMS ⇌ (DMS)2 •+ was shown to have its equilibrium constant between 104 and 5 × 104 M-1. DMSOH• reacts with O2 with a rate constant of 2 × 108 M-1 s-1, independent of pH (11−14). From this and other observations, we estimate the pK a for deprotonation of DMSOH• to exceed 17. From spectral and kinetic data, the maximum lifetime of the radical (DMS)2OH• was predicted to be 10 ns. The stability of DMS−X• (X = OH, I, Br, Cl) in aqueous solution was shown to correlate with the one-electron reduction potential of X•. Comparison of gaseous and aqueous behavior of DMS−OH• reveals that aqueous solvation strongly stabilizes the S−O bond against dissociation into DMS and OH•. The Gibbs free energy of solvation of DMSOH• was calculated to be −12 ± 3 kcal/mol, an unusually large value for a neutral species.

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Section: Resultsmentioning

confidence: 94%

The Dimethylhydroxysulfuranyl Radical

1996

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“…In this case, the radical of interest was obtained by photolysis of solutions containing Br 3 - (more likely, HBr 3 ), HBr, and Br 2 at 355 nm. The procedure used for studies in aqueous solutions was followed here . The reaction was monitored at 365 nm; in aqueous solution, Br 2 •- has λ max at 360 nm (ε 9.9 × 10 4 L mol -1 cm -1 ) …”

Section: Methodsmentioning

confidence: 99%

Kinetics of Manganese(III) Acetate in Acetic Acid: Generation of Mn(III) with Co(III), Ce(IV), and Dibromide Radicals; Reactions of Mn(III) with Mn(II), Co(II), Hydrogen Bromide, and Alkali Bromides

Jiao

Espenson

2000

Inorg. Chem.

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The reaction of cobalt(III) acetate with excess manganese(II) acetate in acetic acid occurs in two stages, since the two forms Co(IIIc) and Co(IIIs) are not rapidly equilibrated and thus react independently. The rate constants at 24.5 degrees C are kc = 37.1 +/- 0.6 L mol-1 s-1 and ks = 6.8 +/- 0.2 L mol-1 s-1 at 24.5 degrees C in glacial acetic acid. The Mn(III) produced forms a dinuclear complex with the excess of Mn(II). This was studied independently and is characterized by the rate constant (3.43 +/- 0.01) x 10(2) L mol-1 s-1 at 24.5 degrees C. A similar interaction between Mn(III) and Co(II) is substantially slower, with k = (3.73 +/- 0.05) x 10(-1) L mol-1 s-1 at 24.5 degrees C. Mn(II) is also oxidized by Ce(IV), according to the rate law -d[Ce(IV)]/dt = k[Mn(II)]2[Ce(IV)], where k = (6.0 +/- 0.2) x 10(4) L2 mol-2 s-1. The reaction between Mn(II) and HBr2., believed to be involved in the mechanism by which Mn(III) oxidizes HBr, was studied by laser photolysis; the rate constant is (1.48 +/- 0.04) x 10(8) L mol-1 s-1 at approximately 23 degrees C in HOAc. Oxidation of Co(II) by HBr2. has the rate constant (3.0 +/- 0.1) x 10(7) L mol-1 s-1. The oxidation of HBr by Mn(III) is second order with respect to [HBr]; k = (4.10 +/- 0.08) x 10(5) L2 mol-2 s-1 at 4.5 degrees C in 10% aqueous HOAc. Similar reactions with alkali metal bromides were studied; their rate constants are 17-23 times smaller. This noncomplementary reaction is believed to follow that rate law so that HBr2. and not Br. (higher in Gibbs energy by 0.3 V) can serve as the intermediate. The analysis of the reaction steps then requires that the oxidation of HBr2. to Br2 by Mn(III) be diffusion controlled, which is consistent with the driving force and seemingly minor reorganization.

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“…H 2 O 2 + Mn 4+ Mn 2+ + 2H + + O 2 R81 1.25 × 10 8 estimated from Jacobsen et al NO 3 + Mn 2+ Mn 3+ + NO 3 - R82 1.1 × 10 6 Neta and Huie Cl 2 - + Mn 2+ Mn 3+ + 2Cl - R83 8.5 × 10 6 4090 Laurence and Thornton Cl 2 - + Mn 2+ MnCl 2 + R84 2.0 × 10 7 4090 Laurence and Thornton 365 MnCl 2 + Mn 2+ + Cl 2 - R85 3.0 × 10 5 Laurence and Thornton 365 MnCl 2 + Mn 3+ + 2Cl - R86 2.1 × 10 5 2100 Laurence and Thornton 365 HSO 5 - + Mn 2+ Mn 3+ + SO 4 - + OH - R87 3.0 × 10 4 = k R26 estimated SO 4 - + Mn 2+ Mn 3+ + SO 4 2- R88 1.8 × 10 7 4100 Buxton et al SO 5 - + Mn 2+ + H 2 O Mn 3+ + HSO 5 - + OH - R89 1.0 × 10 8 Fronaeus et al …”

Section: 3 Proposed Chemical Mechanism For In Cloud Chemistry Modelmentioning

confidence: 98%

Transition Metals in Atmospheric Liquid Phases: Sources, Reactivity, and Sensitive Parameters

et al. 2005

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His research focuses on multiphase chemistry inside clouds by a modeling approach. He participates in the Exchange program within the European Science Foundation activity entitled "Interdisciplinary Tropospheric Research: from the laboratory to global change". From July 2005, he will carry out postdoctoral research on mesoscale chemistry modeling at the Laboratoire Inter-Universitaire des Systèmes Atmosphérique in Paris. Maud Leriche was born in Le Havre, France, in 1974. She received her B.Sc. in physics from Pierre et Marie Curie University (Paris, France) in 1995 and, then, her M.Sc. in atmospheric physics from the Blaise Pascal University (Clermont-Ferrand, France) in 1997. She obtained her Ph.D. in atmospheric physics and chemistry from Blaise Pascal University in 2000 with Dr. Nadine Chaumerliac, studying multiphase chemistry inside clouds. After a temporary position as assistant professor at Blaise Pascal University and a visiting fellowship from NATO at Harvard University with Professor Daniel Jacob, she joined the Centre National de la Recherche Scientifique in 2002, where she is presently a researcher at the Laboratoire de Météorologie Physique at Clermont-Ferrand. Her research interests are mainly in the areas of atmospheric cloud chemistry including the cloud processing of aerosols and the coupling between microphysical and chemical processes in clouds. She is involved in the international AMMA program looking at the redistribution of soluble chemical species by convective clouds. Karine V. Desboeufs received her M.Sc. in atmospheric chemistry in 1997 and her Ph.D. in 2001 from the Paris 7 University with Professor Jean-Louis Colin. Her graduate research focused on the dissolution processes of aerosol particles in cloud droplets and, more particularly, on the release of dissolved trace metals from dust particles. After her Ph.D., she worked as a CNES postdoctoral researcher at the Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), where she performed atmospheric dust transport modeling to study interactions of dust particles with clouds. Currently, she is an assistant professor in chemistry at the Paris 7 University, and she develops her research in the LISA (Laboratoire Interuniversitaire des Systèmes Atmosphériques). Her research interests are iron biogeochemistry and its atmospheric cycling. Gilles Mailhot obtained his Ph.D. in physical chemistry in 1991 from the University Blaise Pascal at Clermont-Ferrand. He studied polymerization photoindiced by charge transfer in a coordination complex. After a postdoctoral fellowship under the supervision of Pr. Gabor Somorjai at the University of California in Berkeley, in 1995 he joined the Centre National de Recherche Scientifique, where he is presently a researcher at the Laboratoire de Photochimie Moléculaire et Macromoléculaire (Clermont-Ferrand, France). His research interests are principally in the areas of photochemistry. He especially focuses on pollutant decomposition in aquatic environments (continental waters, atmospheric liquid phases...

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Kinetics of oxidation of transition-metal ions by halogen radical anions. Part III. The oxidation of manganese(II) by dibromide and dichloride ions generated by flash photolysis

Cited by 19 publications

References 0 publications

The Dimethylhydroxysulfuranyl Radical

The Dimethylhydroxysulfuranyl Radical

Kinetics of Manganese(III) Acetate in Acetic Acid: Generation of Mn(III) with Co(III), Ce(IV), and Dibromide Radicals; Reactions of Mn(III) with Mn(II), Co(II), Hydrogen Bromide, and Alkali Bromides

Transition Metals in Atmospheric Liquid Phases: Sources, Reactivity, and Sensitive Parameters

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