Gas‐phase rate coefficients for a series of alkyl cyclohexanes with OH radicals and Cl atoms

Abstract

The rate coefficients of the reactions of OH radicals and Cl atoms with three alkylcyclohexanes compounds, methylcyclohexane (MCH), trans-1,4-dimethylcyclohexane (DCH), and ethylcyclohexane (ECH) have been investigated at (293 ± 1) K and 1000 mbar of air using relative rate methods. A majority of the experiments were performed in the Highly Instrumented Reactor for Atmospheric Chemistry (HIRAC), a stainless steel chamber using in situ FTIR analysis and online gas chromatography with flame ionization detection (GC-FID) detection to monitor the decay of the alkylcyclohexanes and the reference compounds. The studies were undertaken to provide kinetic data for calibrations of radical detection techniques in HIRAC. The following rate coefficients (in cm 3 molecule −1 s −1 ) were obtained for Cl reactions: k (Cl+MCH) = (3.51 ± 0.37) × 10 -10 , k (Cl+DCH) = (3.63 ± 0.38) × 10 −10 , k (Cl+ECH) = (3.88 ± 0.41) × 10 −10 , and for the reactions with OH radicals: k (OH+MCH) = (9.5 ± 1.3) × 10 -12 , k (OH+DCH) = (12.1 ± 2.2) × 10 −12 , k (OH+ECH) = (11.8 ± 2.0) × 10 −12 . Errors are a combination of statistical errors in the relative rate ratio (2 ) and the error in the reference rate coefficient. Checks for possible systematic errors were made by the use of two reference compounds, two different measurement techniques, and also three different sources of OH were employed in this study: photolysis of CH 3 ONO with black lamps, photolysis of H 2 O 2 at 254 nm, and nonphotolytic trans-2-butene ozonolysis. For DCH, some direct laser flash photolysis studies were also undertaken, producing results in good agreement with the relative rate measurements. Additionally, temperature-dependent rate coefficient investigations were performed for the reaction of methylcyclohexane with the OH radical over the range 273-343 K using the relative rate method; the resulting recommended Arrhenius expression is k (OH + MCH) = (1.85 ± 0.27) × 10 -11 exp((-1.62 ± 0.16) kJ mol −1 /RT) cm 3 molecule −1 s −1 . The kinetic data are discussed in terms of OH and Cl reactivity trends, and comparisons are made with the existing literature values and with rate coefficients from structure-activity relationship methods. This is the first study on the rate coefficient determination of the reaction of ECH with OH radicals and chlorine atoms, respectively. K E Y W O R D Scalibration of OH detector, kinetics, OH and Cl structure activity relationships, substituent effect 544

Cl-Atom-Initiated Atmospheric Degradation of Saturated Cyclic Hydrocarbons: Kinetic and Mechanistic Investigation

“…Consequently, the obtained temperature-dependent (283−363 K) rate coefficient for the reaction of MCH with a Cl atom is k(T) = [(4.48 ± 0.75) × 10 −11 ]exp[(604.42 ± 24.66)/T] cm 3 molecule −1 s −1 . The average rate coefficient for the reaction of MCH with a Cl atom at 298 K is (3.36 ± 0.34) × 10 −10 cm 3 molecule −1 s −1 , which is in excellent agreement with the reported rate coefficients of (3.47 ± 0.12) × 10 −10 , (3.51 ± 0.37) × 10 −10 , and (3.11 ± 0.16) × 10 −10 cm 3 molecule −1 s −1 by Aschmann et al, 18 Bejan et al, 19 and Ballesteros et al 17 respectively. Although the rate coefficients obtained for the reaction of MCH with Cl atoms relative to propylene appear to be consistently higher, they are well within the experimental uncertainties/error limits.…”

“…Aschmann et al 18 measured the rate coefficient using the RR method for the reaction of MCH with Cl atoms at 298 K and is reported to be (3.47 ± 0.12) × 10 −10 cm 3 molecule −1 s −1 . Bejan et al 19 reported the rate coefficient for the reaction of Cl atoms with MCH as k (MCH+Cl) = (3.45 ± 0.37) × 10 −10 cm 3 molecule −1 s −1 using the RR technique. Sprengnether et al 20 reported the rate coefficient for the reaction of OH radicals with MCH using the absolute technique at 298 K as k (MCH+OH) = (9.42 ± 0.12) × 10 −12 cm 3 molecule −1 s −1 .…”

Ab initio kinetic study on the abstraction reactions of methylcyclohexane and implications for high‐temperature ignition simulations from shock tube experiment

“…20 The derived results have been incorporated in the JetSurF II mechanism. 15 The reactions of OH radical and Cl atom with a series of alkylcyclohexanes were also experimentally studied by Bejan et al 21 at 293 K. Besides the above experiments, few studies are performed on the elementary reactions related to MCH combustion to the best of our knowledge due to the limitations of experimental methods. On the other hand, ab initio chemical kinetics have become an important tool for accurate rate constant predictions.…”

Comprehensive Multipath Variational Kinetics Study on Hydrogen Abstraction Reactions from Three Typical Dimethylcyclohexane Isomers by Hydroxyl Radicals: from the Electronic Structure to Model Applications

“…Begum et al 31 evaluated the total and site-specific rate constants for MCH+OH at 298 K and 1 atm by using quantum chemical calculations and the canonical transition state theory. For reactions between poly-alkyl substituted cycloalkanes and OH, only Bejan et al 29 and Ballesteros et al 28 reported the rate constants at room temperatures, involving D14MCH+OH at 293 and 298 K, and T135MCH+OH at 298 K. However, to the best of our knowledge, the site-specific kinetics over a wide temperature range regarding H-abstraction reactions for poly-alkyl sub-stituted cycloalkanes with OH have not been systematically explored yet, even for the most representative and the simplest dimethylcyclohexane isomers.…”

“…For the pentatomic-ring chemistry, Wu et al and Chen et al conducted the kinetics investigation for the reaction of cyclopentane (CPT) with OH, H, CH 3 , and C 2 H 5 radicals by the variational transition state theory and multidimensional tunneling approximation. In the case of MCH+OH, many room-temperature (293–298 K) measurements of the total rate constants were available by using various technologies including Fourier transform infrared (FTIR) spectrometer, GC-MS, and laser-induced fluorescence (LIF). − Sprengnether et al and Bejan et al further measured the temperature-dependent rate constants for MCH+OH at 230–379 K and 273–343 K, respectively by using the relative rate method. Sivaramakrishnan and Michael conducted the total rate measurements of MCH+OH with the reflected shock tube over the range of 836–1273 K and evaluated the site-specific rate constants based on ab initio and transition states calculations.…”