ESR Spectrum of a Trioxide Radical

Abstract

ESR examination of the radical produced by the photolysis in solution at −196°C of CF₃OOCF₃ in the presence of small amounts of oxygen enriched in ¹⁷O shows that the radical so obtained contains two oxygen atoms with ¹⁷O hyperfine constants of 23.3 and 14.0 G. An experiment with CF₃OOCF₃ enriched in ¹⁷O and normal oxygen shows the presence of a third oxygen with an ¹⁷O hyperfine constant of 3.59 G. These data plus simple chemical arguments point very strongly to CF₃OOO· as the structure of this radical. Comparison of the two large ¹⁷O coupling constants and the $g$ factor (2.00373) to those of FOO· indicates a very close similarity in the electronic configuration around the two terminal oxygen atoms of these radicals. It is suggested that radicals of the type RO₃ (including HO₃) may have similar $g$ factors.