Unstable intermediates. Part LXIV. A comparison between the reactions of atomic hydrogen with some substituted benzenes and those induced by γ-irradiation

Abstract

The e.s.r. spectra of radicals obtained by reactions between hydrogen atoms and a range of substituted benzenes are compared with those obtained from the γ-irradiated materials. The most significant feature of these results is the formation of cyclohexadienyl radicals. Whilst in many cases these radicals were formed by both processes, certain compounds, such as para-substituted benzoic acids, only gave these radicals on bombardment with hydrogen atoms, whereas others, such as resorcinol and biphenyl, gave good yields only on exposure to γ-rays. No example of addition at the substituted site was found, addition being ortho or para to all substituents. Addition to 1,3-disubstituted compounds was far more effective than either to 1,2- or 1,4-disubstituted compounds. Loss of tertiary hydrogen by both techniques occurred for cumene and cumic acid.