Abstract
AbstractESR spectra of Lewis acids (VCl4, TiCl4, TiBr4, SnCl4, and AlBr3) and their mixtures with isobutylene were investigated in a n‐heptane solution in the dark and under irradiation at 400–480 nm at −80 to −150°C. A signal was observed only upon irradiating mixtures of VCl4, TiCl4, or TiBr4 and isobutylene. The signal was identified as an isobutylene radical‐cation by comparison with a simulated spectrum. A signal indicating the presence of peroxy radicals were recorded in measurements carried out in the presence of oxygen; these radicals originated from reaction of the isobutylene radical‐cation with oxygen. Radical‐cation initiation by visible light is indicated by the polymerization of isobutylene by VCl4, TiCl4, and TiBr4 and by ESR spectra. The inhibiting effect of oxygen in photochemically initiated polymerization of isobutylene was also elucidated.
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