TY - JOUR

T1 - Kinetics of the reactions of acetonitrile with chlorine and fluorine atoms

AU - Tyndall, Geoffrey S.

AU - Orlando, John J.

AU - Wallington, Timothy J.

AU - Sehested, Jens

AU - Nielsen, Ole J.

PY - 1996/1/11

Y1 - 1996/1/11

N2 - 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 both the relative rate technique and pulse radiolysis with time-resolved ultraviolet absorption spectroscopy. The rate coefficient for the reaction of F atoms with CH3-CN was found to be dependent on total pressure. The observed rate data could be fitted using the Troe expression with Fc = 0.6, k0 = (2.9 ± 2.1) × 10-28 cm6 molecule-2 s-1, and k∞ = (5.8 ± 0.8) × 10-11 cm3 molecule-1 s-1, with a zero pressure intercept of (0.9 ± 0.4) × 10-11 cm3 molecule-1 s-1. The kinetic data suggest that the reaction of F atoms with CH3CN proceeds via two channels: a pressure-independent H atom abstraction mechanism and a pressure-dependent addition mechanism. Consistent with this hypothesis, two products were observed using pulsed radiolysis with detection by UV absorption spectroscopy. As part of the product studies, relative rate techniques were used to measure k(Cl+CH2ClCN) = (2.8 ± 0.4) × 10-14 and k(F+CH2FCN) = (3.6 ± 0.2) × 10-11 cm3 molecule-1 s-1.

AB - 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 both the relative rate technique and pulse radiolysis with time-resolved ultraviolet absorption spectroscopy. The rate coefficient for the reaction of F atoms with CH3-CN was found to be dependent on total pressure. The observed rate data could be fitted using the Troe expression with Fc = 0.6, k0 = (2.9 ± 2.1) × 10-28 cm6 molecule-2 s-1, and k∞ = (5.8 ± 0.8) × 10-11 cm3 molecule-1 s-1, with a zero pressure intercept of (0.9 ± 0.4) × 10-11 cm3 molecule-1 s-1. The kinetic data suggest that the reaction of F atoms with CH3CN proceeds via two channels: a pressure-independent H atom abstraction mechanism and a pressure-dependent addition mechanism. Consistent with this hypothesis, two products were observed using pulsed radiolysis with detection by UV absorption spectroscopy. As part of the product studies, relative rate techniques were used to measure k(Cl+CH2ClCN) = (2.8 ± 0.4) × 10-14 and k(F+CH2FCN) = (3.6 ± 0.2) × 10-11 cm3 molecule-1 s-1.

UR - http://www.scopus.com/inward/record.url?scp=0001762468&partnerID=8YFLogxK

U2 - 10.1021/jp9521417

DO - 10.1021/jp9521417

M3 - Journal article

AN - SCOPUS:0001762468

VL - 100

SP - 660

EP - 668

JO - Journal of Physical Chemistry

JF - Journal of Physical Chemistry

SN - 0022-3654

IS - 2

ER -