Kinetics of Electron Reactions in the γ Irradiated Liquids Ethane, Propane, Ethylene, Propylene, and Cyclopropane: Effect of Molecular Structure

Abstract

The influence of molecular structure on the kinetics of electron reactions in liquids was studied by measuring the efficiency of electron scavenging in five C₂ and C₃ hydrocarbons at 183°K. γ radiation and nitrous oxide scavenger were used. The relative efficiencies of electron scavenging in the five liquids were in the decreasing order ${\mathrm{C}}_2{\mathrm{H}}_6>{\mathrm{C}}_3{\mathrm{H}}_8\mathrm{>c}{\mathrm{–C}}_3{\mathrm{H}}_6>{\mathrm{C}}_3{\mathrm{H}}_6>{\mathrm{C}}_2{\mathrm{H}}_4$ ; choosing the efficiency in ethylene as unity, the relative values are about $\text{40>17>2.7>1.3>1.0}$ , respectively. The results are analyzed according to both the stochastic and the ``square root'' models for radiolysis kinétics. The conclusions drawn from the two models agree with each other. The smaller efficiency of electron scavenging in the olefins, compared to that in the alkanes, is mainly due to the shorter ranges of the secondary electrons in the olefins. Energy degradation of the secondary electrons in ethylene is an order of magnitude more efficient than it is in liquid ethane. The difference between the behavior of an electron in a liquid mono‐olefin and that in the saturated analog decreases with increasing chain length. The behavior of cyclopropane falls between those of propane and propylene, which is consistent with the classical organic chemical reactivity of the compounds. There is no correlation between the electron range in the liquid and the magnitude of the permanent dipole moment of these molecules, but there is a correlation between the electron range and the nature of the polarizability of the molecules.