Matrix effects on the photodissociation of alkane radical cations. Part 1.—Nature of the photodissociation of heptane radical cations in perfluorohexane and 1,1,2-trichlorotrifluoroethane matrices at cryogenic temperatures

Abstract

The nature of the photodissociation of heptane radical cations in perfluorohexane and 1,1,2-trichlorotrifluoroethane matrices has been studied by both EPR and electronic absorption spectrometry. Bleaching of heptane radical cations, formed by γ-irradiation of heptane in CCl₂FCF₂Cl matrices, occurs partly by dissociation under certain wavelength conditions. This photodissociation proceeds without formation of any new trapped paramagnetic entity, indicating dissociation into heptyl carbenium ions and hydrogen atoms (C₇H⁺_{1 6} [graphic omitted] C₇H⁺_{1 5}+ H˙).

Conclusive evidence for this reaction is obtained by observation of hydrogen-atom trapping by isobutene, during bleaching of heptane radical cations in perfluorohexane. The results obtained indicate that physical properties of the matrix have a pronounced effect on the photodissociation of heptane radical cations.