Determination by the phase shift method of the absolute rate constants of reactions of O(^3P) atoms with olefins at 25°C

Abstract

Technical improvements have been made in the application of the phase shift method, recently developed and used in this laboratory to measure the absolute values of the rate constants of the reactions of O(^3P) atoms with ethylene, propylene, 1-butene, and isobutene. More accurate rate constants have now been obtained for these olefins and the measurements have been also extended to three additional olefins (cis-2-butene, trimethylethylene, and tetramethylene).The mean least squares values of the rate constants of the reactions of O(^3P) with olefins at 26°C, expressed as k_2 × 10^(−9) (1./mole^2·sec), and their standard deviations are ethylene 0.43 ±0.05, propelene 2.02 ± 0.17, 1-butene 2.40 ± 0.32, isobutene 9.85 ± 1.34, cis-2-butene 9.00 ± 1.76, trimethylethylene 31.1 ± 3.0, and tetramethylethylene 44.4 ± 4.1. A value of (5.78 ± 0.08) × 10^(10)l.^2/mole^2·sec was obtained for the rate constant of the reaction O(^3P) + NO + M, with M = N_2O. Where comparison with the absolute rate constants in the literature is possible, agreement is very good, especially with some recent absolute values obtained by entirely different experimental techniques. Consistency with the relative rate constant of the O(^3P) reactions with olefins previously determined in this laboratory, is excellent.