TEMPERATURE-DEPENDENCE OF THE REACTION C2H(C2D)-2 BETWEEN 295 AND 700K(O)

The rate coefficients for the reactions of C2H and C2D with O-2 have b een measured in the temperature range 295 K less than or equal to T le ss than or equal to 700 K. Both reactions show a slightly negative tem perature dependence in this temperature range, with k(C2H+O2) = (3.15 +/- 0.04) x 10(-11) (T/295 K)(-(0.16+/-0.02)) cm(3) molecule(-1) s(-1) . The kinetic isotope effect is k(C2H)/k(C2D) = 1.04 +/- 0.03 and is c onstant with temperature to within experimental error. The temperature dependence and the C2H + O-2 kinetic isotope effect are consistent wi th a capture-limited metathesis reaction, and suggest that formation o f the initial HCCOO adduct is rate-limiting.