Reaction kinetics of 1,4-cyclohexadienes with OH radicals: an experimental and theoretical study
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Embargo End Date:
V-T Mai, Tam
Nguyen, Thi T-D
Nguyen, Hieu T
Huynh, Lam K.
KAUST DepartmentChemical Kinetics & Laser Sensors Laboratory
Clean Combustion Research Center
Mechanical Engineering Program
Physical Science and Engineering (PSE) Division
Embargo End Date2023-03-02
Permanent link to this recordhttp://hdl.handle.net/10754/676412
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AbstractThis work presents the OH-initiated oxidation kinetics of 1,4-cyclochexadiene (1,4-CHD). The temperature dependence of the reaction was investigated by utilizing a laser flash photolysis flow reactor and laser-induced fluorescence (LPFR/LIF) technique over the temperature range of 295-438 K and a pressure of ∼50 torr. The kinetics of the reaction was followed by measuring the LIF signal of OH radicals near 308 nm. The reaction of OH radicals with 1,4-CHD exhibited a clear negative temperature dependence. To discern the role of various channels, ab initio and RRKM-based ME calculations (RRKM-ME) were performed over temperatures of 200-2000 K and pressures of 0.76-7600 torr. The computed energy profile revealed that the reaction proceeds via the formation of a pre-reaction van der Waals complex at the entrance channel. The complex was found to be more stable than that usually seen in other alkenes + OH reactions. Both the addition channel and the abstraction reaction of allylic hydrogen were found to have negative energy barriers. Interestingly, the abstraction reaction exhibited a negative temperature dependence at low temperatures and contributed significantly (∼37%) to the total rate coefficients even under atmospheric conditions. At T ≥ 900 K, the reaction was found to proceed exclusively (>95%) via the abstraction channel. Due to the competing channels, the reaction of OH radicals with 1,4-CHD displays complicated kinetic behaviours, reflecting the salient features of the energy profile. The role of competing channels was fully characterized by our kinetic model. The calculated rate coefficients showed excellent agreement with the available experimental data
CitationGiri, B. R., V.-T. Mai, T., Assali, M., Nguyen, T. T.-D., Nguyen, H. T., Szőri, M., Huynh, L. K., Fittschen, C., & Farooq, A. (2022). Reaction kinetics of 1,4-cyclohexadienes with OH radicals: an experimental and theoretical study. Physical Chemistry Chemical Physics. https://doi.org/10.1039/d1cp04964j
SponsorsResearch reported in this publication was supported by the Office of Sponsored Research at King Abdullah University of Science and Technology (KAUST). Experiments in Lille were supported by the French ANR agency under contract No. ANR-11-Labx-0005-01 CaPPA (Chemical and Physical Properties of the Atmosphere). This work has received financial support from the Institute for Computational Science and Technology (ICST) – Ho Chi Minh City (Grant No. 454/QĐ-KHCNTT) and the Department of Science and Technology (DOST) – Ho Chi Minh City. C. F. and M. Sz. acknowledge financial support from the Hungarian-French BALATON program (TéT No. 2021-1.2.4-TÉT-2021-00016/PHC No. 48235NE). Further support was also provided by the National Research, Development and Innovation Fund (Hungary) within the TKP2021-NVA-14 project.
PublisherRoyal Society of Chemistry (RSC)
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