KINETICS OF BRANCHING STEP IN HYDROGEN-OXYGEN REACTION

Lower explosion limits in hydrogen-oxygen and deuterium-oxygen mixtures have been measured in the diffusion régime. From the data, rate constants are calculated for the reactions H + O2 → OH + O and D + O2 → OD + O between 800° and 1 000°K. Activation energies are found to differ by the difference in zero-point energies of OH and OD. Temperature-independent pre-exponential factors differ by a factor of two. Transition states of fixed geometry are not reconcilable with the observed kinetics; nor is the classical collision theory. With a transition state of very loose structure, the observed rate constants can be explained and successfully extrapolated down to 300°K and up to 1 650°K. © 1968.