Radicaux libres crées par irradiation gamma en série bicyclo[2,2,1]heptanique

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Abstract
Above the solid-plastic transition point, well-resolved E.S.R. spectra are recorded when globular compounds are irradiated by γ-rays. We have studied the free radicals observed after γ-irradiation of 15 derivatives of bicyclo[2,2,1]heptan and eight deuterated homologues. The E.S.R. spectra are analysed; they are consistent with the appearance of a free valence localized on one carbon of the cyclohexane ring (C2 for the hydrocarbons, alcohols and chlorides, C3 for the ketones). We note a strong inequivalence for the β-proton couplings and we explain this by a non-planarity of the three bonds surrounding the free radical centre; the deviation from planarity is estimated to be 20–30°. We also observe strong hyperfine interactions with γ-protons. Such long range interactions are inconsistent with the saturated model where spin density is transmitted by spin polarization of localized bonds; they are specific to the unsaturated character of bicyclic compounds which have an enhanced delocalization of the unpaired electron.