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 k 1 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 cm 3 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 k 1 ) (1.6 ( 0.2) × 10 -11 exp [-(2140 ( 200)/T] cm 3 molecule -1 s -1 . Product studies show that the reaction of Cl atoms with CH 3 CN 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 CH 3 -CN was found to be dependent on total pressure. The observed rate data could be fitted using the Troe expression with F c ) 0.6, k 0 ) (2.9 ( 2.1) × 10 -28 cm 6 molecule -2 s -1 , and k ∞ ) (5.8 ( 0.8) × 10 -11 cm 3 molecule -1 s -1 , with a zero pressure intercept of (0.9 ( 0.4) × 10 -11 cm 3 molecule -1 s -1 . The kinetic data suggest that the reaction of F atoms with CH 3 CN 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+CH 2 ClCN) ) (2.8 ( 0.4) × 10 -14 and k(F+CH 2 FCN) ) (3.6 ( 0.2) × 10 -11 cm 3 molecule -1 s -1 .

Atmospheric chemistry ofn‐CH3(CH2)xCN (x = 0–3): Kinetics and mechanisms

“…Previously, Tyndall et al. cited k 7 = (1.15 ± 0.20) × 10 −14 cm 3 molecule −1 s −1 , and Poulet et al. reported k 7 = (8.89 ± 1.24) × 10 −15 .…”

“…Acetonitrile (CH 3 CN) is found in earth's atmosphere, whereas propionitrile (CH 3 CH 2 CN), butyronitrile (CH 3 (CH 2 ) 2 CN), and pentanenitrile (CH 3 (CH 2 ) 3 CN) have all been found in interstellar space and in the atmosphere of one of Saturn's moons, Titan . The presence of CH 3 CN in earth's atmosphere is due to emissions from anthropogenic sources in the form of vehicle exhaust, biomass burning, solvent use, and tobacco smoke . The atmospheric chemistry of CH 3 CN has been studied previously, with HCN identified as one of the oxidation products under atmospheric conditions .…”

“…The atmospheric chemistry of CH 3 CN has been studied previously, with HCN identified as one of the oxidation products under atmospheric conditions . It has also been shown that due to its large proton affinity and large dipole moment, CH 3 CN can form so‐called nonproton hydrates (hydrated complexes with substituted water ligands) in the stratosphere . Studies of the atmospheric chemistry of CH 3 CH 2 CN and CH 3 (CH 2 ) 4 CN can also be found in the literature.…”

Environmental effects of large igneous province magmatism: a Siberian perspective

“…Cl + CH 3 CN. The recommendation is based on results of the study of Tyndall et al [1353]. The results of this study, using both relative and absolute methods and measured over a wide range of experimental conditions are preferred over the results of earlier studies of Kurylo and Knable [756], Poulet et al [1071], and Olbregts et al [1009].…”

Detection of Chlorine in a Non-aqueous Solution via Anodic Oxidation and a Photochemical Reaction

“…Furthermore, high sensitivity for chlorine detection is possible if a photochemical reaction of chlorine is sensed. [26][27][28][29][30][31] In this study, we proposed a new method for detecting temporarily solvated chlorine gas in a polar aprotic solvent, and for detecting chlorine molecules based on an anodic oxidation reaction. Among the various solvents available, we selected acetonitrile (AN) (donor number 14.1; acceptor number 18.9; relative permittivity 35.9) and dimethyl sulfoxide (DMSO) (donor number 29.8; acceptor number 19.3; relative permittivity 46.5).…”