Comparison of muonated free radicals formed in pure liquids with those in dilute solutions: Origins of radicals

Abstract

LCR spectroscopy was used to explore the mechanism by which muonated free radicals form in unsaturated organic liquids. This was achieved by comparing the relative yields of the different radicals formed from the compound as a pure liquid with those found when it was studied as a solute in dilute aqueous micelle solutions. In the latter medium, thermalized muonium atoms are the only precursors. Two types of examples were evaluated: first, styrene and allylbenzene since they give a full range of side-chain and ring addition products: and second, methyl acrylate and acrylonitrile since the former alone shows conformational s-cis-trans isomerism. Both types of process were expected to be particularly sensitive to the nature and charge of the reactive species involved. The results suggest that neutral muonium is the dominant precursor in all these liquids, with ‘hot’ muonium perhaps contributing about 30% of the radicals.