Laser photoemission generation and electrochemical study of methyl radicals as secondary products of OH radicals capture by dimethyl sulfoxide molecules

Abstract

Electrode reactions of intermediates formed during capture of OH radicals by dimethylsulfoxide molecules were studied by laser photoemission in aqueous buffer solutions and pH range from acidic to basic. The results were compared with those obtained previously for electrochemical behaviour of methyl radicals generated via photoemission from CH3Cl. The essential similarity was found for parameters of irreversible one-electron transfer from/to these intermediates, i.e. the potentials E 1/2 on time-resolved voltammograms and rate constants at E = E 1/2. Hence, both active particles were concluded to be equivalent and corresponded to methyl radical. The primary product of OH radicals capture by DMSO molecules, i.e. adduct (CH3)2SO·(OH), was spontaneously decomposed to form ·CH3 with time as low as <2 × 10−5 s. A simultaneous increase of the reduction wave height was observed at pH transition from low basic to low acidic and at illumination times T m of an electrode with UV light if T m ≥ 90–300 ms. The increase exceeded considerably the one-electron reduction level. These features were presumably caused by the rather slow formation of organomercury intermediates as interaction products of the components of the system with a mercury electrode.