Absolute rate constants for the reactions of F(²P) with C₂H₂ and C₂H₄ at T = 298 K

Absolute rate constants for the reactions of C₂H₂ and C₂H₄ with F(²P) atoms have been measured using the discharge-flow kinetic technique coupled to mass spectrometric detection at T = 298 K and 1 Torr nominal pressure. The results obtained were k(F+C₂H₂) = (6.2 ± 1.3) × 10^-12 cm³ molecule^-1 s^-1, which at low pressures is associated with the abstraction channel forming C₂H + HF, and k(F+C₂H₄) = (2.7 ± 0.5) × 10^-10 cm³ molecule^-1 s^-1, which is a measure of the total rate. Product studies were also conducted. This study represents the first direct measurements of the rate constants for both F + C₂H₂ and F + C₂H₄ reactions. A comparison between the absolute rate constants and previous relative rate measurements is made. Further comparisons are made with the rates and products of the reactions of the other halogen atoms with C₂H₂ and C₂H₄ and the reactions of the pseudohalogen CN with the same molecules. The suitability of these reactions as precursors for vinyl and ethynyl for discharge-flow studies is briefly discussed.