Dimethylselenide as a probe for reactions of halogenated alkoxyl radicals in aqueous solution. Degradation of dichloro- and dibromomethane.

Using pulse radiolysis and steady-state gamma-radiolysis techniques, it has been established that, in air-saturated aqueous solutions, peroxyl radicals CH 2HalOO (*) (Hal = halogen) derived from CH 2Cl 2 and CH 2Br 2 react with dimethyl selenide (Me 2Se), with k on the order of 7 x 10 (7) M (-1) s (-1), to form HCO 2H, CH 2O, CO 2, and CO as final products. An overall two-electron oxidation process leads directly to dimethyl selenoxide (Me 2SeO), along with oxyl radical CH 2HalO (*). The latter subsequently oxidizes another Me 2Se molecule by a much faster one-electron transfer mechanism, leading to the formation of equal yields of CH 2O and the dimer radical cation (Me 2Se) 2 (*+).

Reactions of halogenated hydroperoxides and peroxyl and alkoxyl radicals from isoflurane in aqueous solution.

Model systems, based on aqueous solutions containing isoflurane (CHF(2)OCHClCF(3)) as an example, have been studied in the presence and absence of methionine (MetS) to evaluate reactive fates of halogenated hydroperoxides and peroxyl and alkoxyl radicals. Primary peroxyl radicals, CHF(2)OCH(OO*)CF(3), generated upon 1-e-reduction of isoflurane react quantitatively with MetS via an overall two-electron oxidation mechanism to the corresponding sulfoxide (MetSO). This reaction is accompanied by the formation of oxyl radicals CHF(2)OCH(O*)CF(3) that quantitatively rearrange by a 1,2-hydrogen shift to CHF(2)OC*(OH)CF(3).