Kinetic isotope effect in the thermal dissociation of ethane

Abstract

The rate constants for the dissociation of ethane and ethane-d₆ have been measured at temperatures from 778 to 878 K and over pressures between 1.33 and 214 kN m^–2. The secondary kinetic isotope effect, (k^D₁/k^H₁), is greater than unity under all conditions studied. The results mirror the temperature dependence of the corresponding equilibrium constant ratio and are in line with measurements of (k^D_–1/k^H_–1) for methyl recombination at room temperature. The results are higher than a prediction for the infinite pressure limit by an adiabatic open channel theory of unimolecular dissociation.