Kinetics of the reactions of vinyl radicals with molecular oxygen and chlorine at temperatures 200–362 K

Abstract

The kinetics of the C₂H₃ + O₂ and C₂H₃ + Cl₂ reactions have been studied in direct measurements at temperatures between 200–362 K using a tubular flow reactor coupled to a photoionization mass spectrometer (PIMS). The vinyl radicals were homogeneously generated by the pulsed laser photolysis of methyl vinyl ketone at 193 nm. The subsequent decays of the radical concentrations were monitored in time-resolved measurements to obtain the reaction rate coefficients under pseudo-first-order conditions. Reaction products identified were HCO and H₂CO for the oxygen reaction and C₂H₃Cl for the chlorine reaction, respectively. The rate coefficients of both reactions were independent of the bath gases (He or N₂) and pressures within the experimental range, 0.13–0.53 kPa, and can be expressed by the Arrhenius equations k(C₂H₃ + O₂) = (4.62 ± 0.40) × 10⁻¹²exp(1.41 ± 0.18 kJ mol⁻¹/RT) cm³ molecule⁻¹ s⁻¹ and k(C₂H₃ + Cl₂) = (4.64 ± 0.59) × 10⁻¹²exp(3.12 ± 0.27 kJ mol⁻¹/RT) cm³ molecule⁻¹ s⁻¹, where uncertainties are one standard deviation. These experimental results obtained by using our new apparatus are in good agreement with previous direct measurements.