Primary products of the reaction between O(3P)-atoms and C2H4 studied with ESR- and LMR-detection

Abstract

The primary products of the reaction between O(3P)-atoms and C2H4 O(3P)+C2H4→products (1) have been studied at room temperature in the gas phase. The products in the low pressure regime were investigated in two isothermal discharge flow systems with Electron Spin Resonance (ESR) detection of O- and H-atoms and Far Infrared Laser Magnetic Resonance (LMR) detection of O-atoms and HCO- as well as CH2-radicals. The absolute concentrations of these species were determined using several independent titration reactions. The experiments yielded the branching ratios for the following reaction channels: O+C2H4→C2H3O+H k1a/k1=(0.50±0.10) (1a) O+C2H4→CH3+HCO k1b/k1=(0.44±0.15) (1b) O+C2H4→CH2+H2CO k1c/k1=(0.06±0.03) (1c) The formation of the high pressure stabilization products ethylene oxide and acetaldehyde from the reaction channels O+C2H4+M→C2H4O+M (1d) O+C2H4+M→CH3CHO+M (1e) was observed in a static system at pressures between 5 bar ≦p≦70 bar using Hg*-sensitized decomposition of N2O as the O-atom source and gaschromatographic analysis. From the half pressure for CH3CHO production the lifetime of the addition complex from O+C2H4 with respect to redissociation and dissociation into fragments is concluded to be of the order 10−11 s. Thus, 1.2 H-atom migration in the addition complex has to proceed on this time scale.