An Electron Spin Resonance Study of the Spin Adducts of OH and HO2 Radicals with Nitrones in the Ultraviolet Photolysis of Aqueous Hydrogen Peroxide Solutions

The photolysis of H2O2 in aqueous solution has been used to study and characterize electron spin resonance (e.s.r.) spectra of the •OH and •HO2 radical spin adducts with the spin traps 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) and phenyl-t-butyl nitrone (PBN). At high concentrations of spin trap and low concentrations of H2O2 an e.s.r. spectrum is obtained which we assign to the •OH radical adduct (for DMPO, aN = 15.3 G, aβH = 15.3 G, [Formula: see text] and g = 2.0060; for PBN, aN = 15.3 G, aβH = 2.75 G, and g = 2.0057). At low concentrations of spin trap and high concentrations of H2O2• a second spin adduct spectrum is obtained which we assign to the spin adduct of the HO2 radical (for DMPO, aN = 14.3 G, aβH = 11.7 G, aγH = 1.25 G, g = 2.0061; for PBN, aN = 14.8 G, aβH = 2.75 G, and g = 2.0057).