Radiolytic Reductions and Oxidations in Dimethyl Sulfoxide Solutions. Solvent Effects on Reactivity of Halogen Atom Complexes

Article abstract of DOI:10.1021/j100187a032

Radiolysis of dimethyl sulfoxide (DMSO) solutions containing various additives was used to achieve clean one-electron reduction or oxidation of solutes.Pulse radiolysis of benzoquinone in DMSO solutions containing acetone and triethylamine permitted conversion of all primary radicals into reducing species.The total yield of reduction in the γ-radiolysis of methyl viologen solutions was found to be 0.37 μmol/J.In the pulse radiolysis of TMPD and triphenylamine in aerated DMSO containing LiCl and/or CCl4, all the primary radicals were converted into oxidizing species and gave a maximum yield of 0.39 μmol/J.In the latter systems, oxidation was partly by halogen atom complexes.The reactivity of complexes of DMSO (DMSO*Cl, DMSO*Br) and of halide ions (Br2^.1-, I2^.1-) was examined for several organic compounds.DMSO*Cl oxidizes chlorpromazine, triphenylamine, and zinc porphyrin with rate constants of the order of 1E7-1E8 M^-1 s^-1, and the rates increase upon addition of CH2Cl2 as well as upon addition of water and formamide.DMSO*Cl also reacts with olefins by addition of Cl to the double bond; the rate constants increase upon increasing the electron-donating properties of the substituents on the double bond.The rate constants for oxidation of chlorpromazine by Br2^.1- and I2^.1- increase by more than 2 orders of magnitude upon changing the solvent from DMSO gradually to water.The change was less with acetonitrile/water mixtures, and the difference is probably due to differences in ion solvation.