- Nature of 2?/1?* Three-Electron-Bonded Chlorine Adducts to Sulfoxides
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Reaction of sulfoxide radical cations, R2SO.+, with chloride ions in acidic aqueous solutions (pH * electron.The same species is formed upon oxidation of sulfoxides by Cl2*, although only with relatively low rate constants.The measured λmax are 390, 400, and 410 nm for the R2SO...Cl species with R = Me, Et, and n-Pr, respectively.Equilibrium constants for R2SO.+ + Cl- R2SO...Cl have been determined to be 560, 600, and 575 M-1, for the same respective series of species (error limit +/- 20percent).It is considered that our three-electron-bonded species is identical with an electronically not further specified chlorine-atom adduct to sulfoxide, R2SO(Cl)., observed earlier in sulfoxide-containing solutions of carbon tetrachloride and dichloromethane.The R2SO...Cl exhibit oxidizing properties and are shown to oxidize, for example organic sulfides and disulfides (rate constants on the order of 108 M-1 s-1) or SCN- (rate constants on the order of 109 M-1 s-1).The optical and kinetic results are discussed in light of the electronic properties of the radical species.
- Kishore, Kamal,Asmus, Klaus-Dieter
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p. 7233 - 7239
(2007/10/02)
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- Radical Cations from One-electron Oxidation of Aliphatic Sulphoxides in Aqueous Solution. A Radical Chemical Study
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Sulphoxide radical cations, (R2SO)+., have been observed upon one-electron oxidation of simple aliphatic sulphoxides by strongly oxidizing radicals with redox potentials >/=+2 V, e.g.SO4-., (CH3I)+., (CH3IICH3)+, or Ti2+ in pulse-irradiated aqueous solutions.They exhibit optical absorptions in the u.v. with λmax depending on the substituent (e.g. 300, 320, and 330 nm for R=Me, Et, and Pr, respectively).Extinction coefficients are of the order of 103 mol-1dm-3cm-1.The sulphoxide radical cations exist only at low pH and are probably best formulated in terms of an adduct with one water molecule, (R2SOOH2)+.The pK values for the equilibrium (R2SOOH2)+R2SO(OH). + H+ have been estimated to be 5.6, 6.1, and 6.5, for R=Me, Et, and Pr, respectively, from yield measurements.The neutral R2SO(OH). is identical with the hydroxyl radical adduct to sulphoxides formed at any pH in the reaction of R2SO + .OH, and decays irreversibly into R. + RSO2- + H+.The sulphoxide radical cationsare very good oxidants.Absolute rate constants have been measured for their reactions with a variety of electron donors, namely, organic sulphides, dithia compounds, disulphides, Br-, I-, and SCN-.The optical and kinetic results are discussed in the light of the electronic properties of the radical species.
- Kishore, Kamal,Asmus, Klaus-Dieter
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p. 2079 - 2084
(2007/10/02)
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