Temperature dependence of the reaction C2H (C2D) + O2 between 295 and 700 K

The rate coefficients for the reactions of C₂H and C₂D with O₂ have been measured in the temperature range 295 K T 700 K. Both reactions show a slightly negative temperature dependence in this temperature range, with k_C2H+O2 = (3.15 ± 0.04) × 10⁻¹¹ (T/295 K)^{−(0.16 ± 0.02)} cm³ molecule⁻¹ s⁻¹. The kinetic isotope effect is k_C2H/k_C2D = 1.04 ± 0.03 and is constant with temperature to within experimental error. The temperature dependence and the C₂H + O₂ kinetic isotope effect are consistent with a capture-limited metathesis reaction, and suggest that formation of the initial HCCOO adduct is rate-limiting.