Spin trapping of the •CO2− radical in aqueous medium

The •CO2− radical has been generated by photolysis of a solution of sodium peroxydisulfate containing sodium formate and by hydrogen abstraction using TiCl3 and H2O2 in the presence of sodium formate. In both cases, the inclusion of DMPO resulted in the formation of a spin adduct with aN = 15.8 G, aβH = 19.1 G, and g = 2.0058 which is assigned to the •CO2− adduct. In addition the DMPO adduct of SO4−• is presented. Finally, it is shown that DMPO can react with anionic radicals and that the resultant spin adducts are themselves highly dissociated.