Kinetics of the Reactions of Acetonitrile with Chlorine and Fluorine Atoms

Abstract

The rate coefficients for the reactions of chlorine and fluorine atoms with acetonitrile have been measured using relative and direct methods. In the case of chlorine atoms the rate coefficient k1 was measured between 274 and 345 K using competitive chlorination and at 296 K using laser flash photolysis with atomic resonance fluorescence. The rate coefficient measured at ambient temperature (296 ± 2 K) is (1.15 ± 0.20) × 10-14 cm3 molecule-1 s-1, independent of pressure between 5 and 700 Torr (uncertainties are 2 standard deviations throughout). This result is a factor of 6 higher than the currently accepted value. The results from the three independent determinations reported here yield the Arrhenius expression k1 = (1.6 ± 0.2) × 10-11 exp[−(2140 ± 200)/T] cm3 molecule-1 s-1. Product studies show that the reaction of Cl atoms with CH3CN proceeds predominantly, if not exclusively, by hydrogen abstraction at 296 K. The rate coefficient for the reaction of fluorine atoms with acetonitrile was measured using...