Abstract
Organic peroxy radicals (RO(2)) are important intermediates for oxidation processes in aerobic chemical systems. Their self- and "cross"-reactions (i.e., with themselves and other RO(2)) are increasingly receiving attention in a wide range of applications, from atmospheric chemistry to cancer therapies. However, their mechanism has been debated for decades. The Russell mechanism, widely assumed for these reactions today, is characterized by a tetroxide intermediate, only observed once and partially since its postulate in 1957. Here we report the observation of tetroxides in the gas-phase reactions of different RO(2) by direct mass spectrometry, in which ionic and gas-phase dimerization could be ruled out. Within the uncertainties in the kinetic profiles, the lifetime for CH(3)OOOOCH(3) was determined to be in the range 0.2 and 200 milliseconds, consistent with an intermediate and supporting the Russell mechanism.