ESR, Structure, and reactions of Specifically Deuterium-Labeled Pentane Cations in X-Irradiated Freon Matrices

Article abstract of DOI:10.1021/j100265a011

Solutions of 1-2 mol percent of pentane, pentane-3-d₂, pentane-2,4-d₄, and pentane-1,5-d₆ in CFCl3, CF3CCl3, and CF2ClClFCl2 have been X irradiated at 77 K.ESR spectra of the molecular ions were recorded at temperatures between 77 K and either the glass transition temperature for CF3CCl3 (140 K) and CF2ClClFCl2 (about 110 K) or the melting point for CFCl3 (162 K).It was found that the pentane molecular ions in these matrices have not only the structure of an extended chain, but also that of several gauche conformers.Their identity and proportions depend on the matrix and on the labeling.INDO calculations were made to elucidate the detailed structure of the conformers of the pentane molecular ions in these matrices.Tilting both methyl groups toward the central-CH2- leads to a significant decrease in the energy of the ion with a minimum at about 90 deg and to significant changes in hyperfine coupling constants, giving a much better agreement with experimental data.Isotope effects were discovered for the deprotonation reaction in CF2ClCFCl2 and especially for the photofragmentation in CF3CCl3.