Electron spin resonance and optical studies of radiation-induced intermediates. Radical ions and radicals from α-methylstyrene in organic glasses

Abstract

Radical ion and radical intermediates derived from α-methylstyrene by gamma irradiation and photoionization in organic glasses have been assigned by e.s.r. and optical techniques. Measurements made in rigid solutions of the monomer in 3-methylpentane and methyltetrahydrofuran at –196° indicate that the radical anion is formed by electron capture during irradiation and exhibits absorption bands at 411 and 580 nm. When these glasses are warmed after gamma irradiation, the radical anion is converted to the neutral α,α-dimethylbenzyl radical by proton transfer from the positive ion. The latter radical is also observed in ethanol glasses immediately after irradiation, and the hyperfine splitting constants are 16.5 gauss for the 6 methyl protons and 5.5 gauss for the 3 protons (ortho and para) in the aromatic ring. Evidence from isotopic studies indicates that the neutral radical is formed in ethanol by proton transfer from the hydroxylic proton to the vinylidene group of the radical anion.