Reaction F + C2H4: Rate Constant and Yields of the Reaction Products as a Function of Temperature over 298–950 K

The kinetics and products of the reaction of F + C 2 H 4 have been studied in a discharge flow reactor combined with an electron impact ionization mass spectrometer at nearly 2 Torr total pressure of helium in the temperature range 298–950 K. The total rate constant of the reaction, k 1 = (1.78 ± 0.30) × 10 –10 cm 3 molecule –1 s –1, determined under pseudo-first-order conditions, monitoring the kinetics of F atom consumption in excess of C 2 H 4, was found to be temperature independent in the temperature range used. H, C 2 H 3 F, and HF were identified as the reaction products. Absolute measurements of the yields of these species allowed to determine the branching ratios, k 1b / k 1 = (0.73 ± 0.07) exp(−(425 ± 45)/ T ) and k 1a / k 1 = 1 – (0.73 ± 0.07) exp(−(425 ± 45)/ T ) and partial rate constants for addition–elimination (H + C 2 H 3 F) and H atom abstraction (HF + C 2 H 3 ) pathways of the title reaction: k 1a = (0.80 ± 0.07) × 10 –10 exp(189 ± 37/ T ) and k 1b = (1.26 ± 0.13) × 10 –10 exp(−414 ± 45/ T ) cm 3 molecule –1 s –1, respectively, at T = 298–950 K and with 2σ quoted uncertainties. The overall reaction rate constant can be adequately described by both the temperature independent value and as a sum of k 1a and k 1b . The kinetic and mechanistic data from the present study are discussed in comparison with previous absolute and relative measurements and theoretical calculations.