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Quasiclassical trajectory calculations on a six-dimensional, analytically constructed potential energy surface have been used to assess the selectivity of reactant vibrational and rotational energy on reactive cross sections for the reaction OH + Cl2 - HOCl + Cl.

Geometries for possible transition states and energy minima of the potential-energy surface for the reaction between BrO and CIO radicals and for conformers of CIOOBr peroxide are identified and harmonic frequency calculations are carried out. The results of the study assist in the qualitative understanding of the mechanism and kinetics of BrO + CIO reaction.

The mechanisms for the OH radical and Cl atom gas-phase reaction kinetics of substituted aromatic compounds remain a topic of atmospheric and combustion chemistry research. 4-Chlorobenzotrifluoride ( p -chlorobenzotrifluoride, p -ClC 6 H 4 CF 3 , PCBTF) is a commonly used substituted aromatic volatile organic compound (VOC) in solvent-based coatings. As such, PCBTF is classified as a volatile chemical product (VCP) whose release into the atmosphere potentially impacts air quality. In this study, rate coefficients, k 1 , for the OH + PCBTF reaction were measured over the temperature ranges 275-340 and 385-940 K using low-pressure discharge flow-tube reactors coupled with a mass spectrometer detector in the ICARE/CNRS (Orléans, France) laboratory. k 1 (298-353 K) was also measured using a relative rate method in the thermally regulated atmospheric simulation chamber (THALAMOS; Douai, France). k 1 ( T ) displayed a non-Arrhenius temperature dependence with a negative temperature dependence between 275 and 385 K given by k s 1 (275-385 K) = (1.50 ± 0.15) × 10 -14 exp((705 ± 30)/T) cm 3 molecule -1 s -1 s k 1 (298 K) = (1.63 ± 0.03) × 10 -13 cm 3 molecule -1 s -1 and a positive temperature dependence at elevated temperatures given by k 1 (470-950 K) = (5.42 ± 0.40) × 10 -12 exp(-(2507 ± 45) /T) cm 3 molecule -1 s -1 s k 1 (298 K) results are in reasonable agreement with two previous 296 K (760 Torr, syn. air) relative rate measurements. The rate coefficient for the Cl-atom + PCBTF reaction, k 2 , was also measured in THALAMOS using a relative rate technique that yielded k 2 (298 K) = (7.8 ± 2) × 10 -16 cm 3 molecule -1 s -1 . As part of this work, the UV and infrared absorption spectra of PCBTF were measured (NOAA; Boulder, CO, USA). On the basis of the UV absorption spectrum, the atmospheric instantaneous UV photolysis lifetime of PCBTF (ground level, midlatitude, Summer) was estimated to be 3-4 days, assuming a unit photolysis quantum yield. The non-Arrhenius behavior of the OH + PCBTF reaction over the temperature range 275 to 950 K is interpreted using a mechanism for the formation of an OH-PCBTF adduct and its thermochemical stability. The results from this study are included in a discussion of the OH radical and Cl atom kinetics of halogen substituted aromatic compounds for which only limited temperature-dependent kinetic data are available.