Kinetics of the Gas-Phase Reaction of OH with Chlorobenzene

Abstract

The kinetics of the reaction of hydroxyl radicals with chlorobenzene was studied experimentally using a pulsed laser photolysis/pulsed laser induced fluorescence technique over a wide range of temperatures, 298-670 K, and at pressures between 13.33 and 39.92 kPa. The bimolecular rate constants demonstrate different behavior at low and high temperatures. At room temperature, T = 298.8±1.5 K, the rate constant is equal to (6.02 ± 0.34)×10-13 cm3 molecule-1 s-1; at high temperatures (474 - 670 K), the rate constant values are significantly lower and have a positive temperature dependence that can be described by an Arrhenius expression k1(T ) = (1.01 ± 0.35)×10-11 exp[(-2490 ± 170 K)/T] cm3 molecule-1 s-1. This behavior is consistent with the low-temperature reaction being dominated by reversible addition and the high-temperature reaction representing abstraction and addition-elimination channels. The potential energy surface of the reaction was studied using quantum chemical methods and a transition state theory model was developed for all reaction channels. The temperature dependences of the high-temperature rate constants obtained in calculations using the method of isodesmic reactions for transition states (IRTS) and the CBS-QB3 method are in very good agreement with experiment, with deviations smaller than the estimated experimental uncertainties. The G3//B3LYP-based calculated rate constants are in disagreement with the experimental values. The IRTS-based model was used to provide modified Arrhenius expressions for the temperature dependences of the rate constant for the abstraction and addition-elimination (Cl replacement) channels of the reaction.

Benchmarking of DFT functionals for the kinetics and mechanisms of atmospheric addition reactions of OH radicals with phenyl and substituted phenyl‐based organic pollutants

“…For the C 6 H 5 F, C 6 H 5 Cl, and C 6 H 5 Br reactions, the Δ E ‡ and Δ G ‡ values for • OH addition to ipso position are the highest, followed by those for addition to the meta position, which are both higher than those for • OH addition to the ortho and para positions at the same theoretical level. These conclusions for the preference for the position of • OH addition to C 6 H 5 F, C 6 H 5 Cl, and C 6 H 5 Br is consistent with previous findings at higher levels of theory . It should be mentioned that the CBr bond is broken (from 1.878 Å to 2.735 Å) when • OH is added to the ipso position of C 6 H 5 Br with the MPW1B95 functional.…”

“… k OH ×10 −13 (Experimental values for halogenated benzenes): for C 6 H 5 F + • OH, (6.9 ± 1.38) by Atkinson (298 K); (7.9 ± 2.2) by Andersen et al (296 K); (6.31 ± 0.81) by Wallington et al (296 K); (8.7 ± 0.3) by Ohta and Ohyama (298 K); (5.4 ± 0.5) by Zetzsch (296 K) . For C 6 H 5 Cl + • OH, (7.41 ± 0.94) by Wallington et al (296 K); (6.02 ± 0.34) by Bryukov et al (298 K); (6.70 ± 0.50) by Zetzsch (296 K); (5.50 ± 4.40) by Edney et al (297 K); (9.10 ± 1.20) by Atkinson et al (299 K); (8.8 ± 1.1) by Atkinson et al (room temperature) . For C 6 H 5 Br + • OH, (9.37 ± 2.04) by Nakano et al (295 K); (7.06 ± 1.6) by Witte et al (295 K); (9.15 ± 0.97) by Wallington et al (296 K); (7.7 ± 0.40) by Atkinson (298 K); (7.0 ± 0.7) by Zetzsch (296 K) .…”

“…These conclusions for the preference for the position of OH addition to C 6 H 5 F, C 6 H 5 Cl, and C 6 H 5 Br is consistent with previous findings at higher levels of theory. [60][61][62][63] It should be mentioned that the CABr bond is broken (from 1.878 Å to 2.735 Å) when OH is added to the ipso position of C 6 H 5 Br with the MPW1B95 functional. However, the CABr bond is maintained, although it becomes longer (from 1.876 Å to 1.966 Å with xB97; from 1.890 Å to 2.091 Å with CAM-B3LYP; and from 1.898 Å to 2.088 Å with BMKD3) for OH addition to the ipso site of C 6 H 5 Br.…”

Theoretical study on the mechanism and kinetics of addition of hydroxyl radicals to fluorobenzene

“…The more stable prereaction complex obtained by G3 calculations makes the overall reaction rate much faster than that from MP2, but still significantly slower than experimental values. [2,[55][56][57] However, for chlorobenzene [58] and bromobenzene, [59] it was also evaluated if phenol can be produced directly by the halogen atom elimination from their ipso-adducts. It was possible to reproduce the experimental reaction rates in the temperature range 230-310 K by treating the relative translation of OH radical and fluorobenzene as a twodimensional particle-in-the-box approximation and by lowering the prereaction complex well and reaction barriers by 0.7 kcal mol À1 .…”

Tropospheric Degradation of Perfluorinated Aromatics: A Case of Hexafluorobenzene

“…Contrary to this, the number of studies on aromatic compounds is quite limited. The detailed investigations on reaction mechanisms and reaction kinetics are available only for benzene, [7,8] toluene, [9] fluorobenzene, [10] chlorobenzene, [11,12] phenol [13] and naphthalene. [14] The major reason for a small number of studies on aromatic compounds is their significant size and complex reaction mechanism with OH radicals, thus sophisticated theoretical methods must be used in order to obtain meaningful results.…”