Radiolysis products of the cyclohexane–bicyclic diene binary system

Solutions of 5-vinyl-2-norbornene (VNB, 5-vinylbicyclo[2.2.1]hept-2-ene) and the related compounds 5-ethylidene-2-norbornene (ENB, 5-ethylidenbicyclo[2.2.1]hept-2-ene) and 2-vinyl-2-norbornane (VNN, 2-vinylbicyclo[2.2.1]heptane) in cyclohexane have been irradiated with γ-rays at 40°C. The initial radiation-chemical yields G 0 for the consumption of the solutes and the formation of final products of γ-radiolysis of the solvent cyclohexane have been determined. It has been shown that solute consumption and molecular hydrogen formation yields G 0(−RH) and G 0(H2), respectively, are linearly related to the first vertical ionization potential of the solute. The G 0 values of molecular hydrogen, cyclopentadiene (CPD), butadiene, and methylallene, minor products of γ-radiolysis (40°C) of liquid VNB, ENB, and dicyclopentadiene (tricyclo[5.2.1.02.6]decadiene-3.8), have been determined. It has been shown that the G 0 values of CPD formation linearly depend on the first vertical ionization potentials of γ-irradiated bicyclic dienes. It is concluded that the γ-irradiation of cyclohexane generates two kinds of radical cations, which differ in mobility and reactivity.