NOVEL DEVIATIONS FROM THE 'MIXTURE LAW' IN THE RADIOLYSIS OF HYDROCARBON MIXTURES

Abstract

The 'mixture law' states that, if the radiolysis of material A gives a product M with yield G M , then, in a mixture where the mole fraction of A is X A , the yield of M is G M X A .In the radiolysis of dilute mixtures of cyclohexane-d 12 or of methylcyclohexane-d 14 with other aliphatic hydrocarbons D 2 is formed in a process which is first order with respect to the deutero compound. As a consequence these mixtures provide a sensitive method of detecting deviations from the mixture law.Experimentally the yield of D 2 and the yield of HD vary widely from one solvent to another amongst the C 5 to C 10 hydrocarbons selected. The yields of D 2 and HD are, approximately, linearly related. The solvents have similar quantitative effects on the yields for both deuterated hydrocarbons.These deviations from the mixture law cannot be explained in terms of kinetic effects (variations in rate constants caused by differing bond strengths), because the D 2 yield measures a process without free radical intermediates. Mechanisms involving excitation transfer, ion–molecule reactions, and subexcitation electrons are discussed.