EPR Spectra and Kinetics of some Carbonyloxyl Radicals, XCO2 .

We have demonstrated that aroyloxyl,1 ArCO2 . and alkoxycarbonyloxyl,2 ROCO2 ., radicals can be generated by laser flash photolysis (LFP) of appropriate peroxides and tert-butyl peresters and that the kinetic behaviour of these radicals can be monitored via a broad absorption they possess in the visible region of the spectrum. The lifetimes of some of these radicals were sufficiently great as to suggest that certain XCO2 . might be observable by conventional EPR spectroscopy during continuous UV irradiation of suitable precursors in solution at low temperatures.