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.