Hydrogen Formation in the Radiolysis of Saturated Hydrocarbons in the Liquid and Solid Phases. Effect of Temperature

Hydrogen yields have been determined for thirteen saturated hydrocarbons (n-pentane, cyclopentane, methylcyclopentane, 3-methylpentane, n-hexane, cyclohexane, methylcyclohexane, n-heptane, n-octane, 2,2,4-trimethylpentane, n-nonane, n-decane and polyethylene) γ-irradiated at 20°C, −72°C and −196°C. The decrease in hydrogen yield with decreasing temperature from 20°C to −196°C has been correlated with the yield of thermal hydrogen atoms, which was obtained by adding ethylene as a scavenger at 20°C; the decrease in most cases was nearly equal to a half of the thermal hydrogen atom yield. Evidence of thermal hydrogen atom production at −196°C has also been demonstrated by ESR measurement. It has been concluded that thermal hydrogen atoms abstract hydrogen atoms from solvent molecules at 20°C, but they mostly recombine with each other to form hydrogen molecules at −196°C. An empirical formula based on the C–H bond parameter has been presented which is adapted for the hydrogen yield from normal alkanes.