Observation of Short-lived Free Radicals in Solution

Abstract

THE direct detection of short-lived free radicals by physical methods such as spectroscopy and mass spectrometry has become a valuable means of identification and kinetic study in the gas phase. It has not hitherto been possible to study these radicals in a comparable manner in solution, although radicals which exist in detectable equilibrium concentrations, such as triphenyl methyl, are, of course, readily observed spectroscopically. During our study of triplet states in solution, it was necessary to use purified solvents of high viscosity which had been thoroughly freed from dissolved gases, and we have found that these solvents are suitable for the detection and study of a number of reactive free radicals. The function of such solvents is to retard the diffusion-controlled recombination without offering alternative rapid reactions with the solvent itself.