OH Radical and Chlorine Atom Kinetics of Substituted Aromatic Compounds: 4-chlorobenzotrifluoride (p-ClC6H4CF3)

Aparajeo Chattopadhyay; Yuri Bedjanian; Manolis N Romanias; Angeliki D Eleftheriou; Vasilios S Melissas; Vassileios C Papadimitriou; James B Burkholder

doi:10.1021/acs.jpca.2c04455

OH Radical and Chlorine Atom Kinetics of Substituted Aromatic Compounds: 4-chlorobenzotrifluoride (p-ClC₆H₄CF₃)

J Phys Chem A. 2022 Aug 18;126(32):5407-5419. doi: 10.1021/acs.jpca.2c04455. Epub 2022 Aug 9.

Authors

Aparajeo Chattopadhyay^{1

2}, Yuri Bedjanian³, Manolis N Romanias⁴, Angeliki D Eleftheriou⁵, Vasilios S Melissas⁶, Vassileios C Papadimitriou^{1

2

5}, James B Burkholder¹

Affiliations

¹ Chemical Sciences Laboratory, National Oceanic and Atmospheric Administration, 325 Broadway, Boulder, Colorado 80305-3327, United States.
² Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado 80309, United States.
³ Institut de Combustion, Aérothermique, Réactivité et Environnement (ICARE), CNRS 45071 Orléans Cedex 2, France.
⁴ Center for Energy and Environment, Institut Mines-Télécom Nord Europe, Université Lille, F-59000 Lille, France.
⁵ Laboratory of Photochemistry and Chemical Kinetics, Department of Chemistry, University of Crete, Vassilika Vouton, 70013, Heraklion, Crete, Greece.
⁶ Department of Chemistry, University of Ioannina, Ioannina GR-45110, Greece.

PMID: 35943137
DOI: 10.1021/acs.jpca.2c04455

Abstract

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-ClC₆H₄CF₃, 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, k₁, 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. k₁(298-353 K) was also measured using a relative rate method in the thermally regulated atmospheric simulation chamber (THALAMOS; Douai, France). k₁(T) displayed a non-Arrhenius temperature dependence with a negative temperature dependence between 275 and 385 K given by k₁(275-385 K) = (1.50 ± 0.15) × 10^-14 exp((705 ± 30)/T) cm³ molecule^-1 s^-1, where k₁(298 K) = (1.63 ± 0.03) × 10^-13 cm³ molecule^-1 s^-1 and a positive temperature dependence at elevated temperatures given by k₁(470-950 K) = (5.42 ± 0.40) × 10^-12 exp(-(2507 ± 45) /T) cm³ molecule^-1 s^-1. The present k₁(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, k₂, was also measured in THALAMOS using a relative rate technique that yielded k₂(298 K) = (7.8 ± 2) × 10^-16 cm³ 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.