The rate constants for the reactions of OH radicals with fully fluorinated alkenes containing different numbers of -CF(3) groups next to olefinic carbon, CF(2)═CF(2), CF(2)═CFCF(3), CF(3)CF═CFCF(3), and (CF(3))(2)C═CFC(2)F(5), were measured between 230 and 480 K using the flash photolysis resonance fluorescence technique to give the following expressions: k(C(2)F(4))(250-480 K) = 1.32 × 10(-12) × (T/298 K)(0.9) × exp(+600 K/T) cm(3) molecule(-1) s(-1), k(C(3)F(6))(230-480 K) = 9.75 ×10(-14) × (T/298 K)(1.94) × exp(+922 K/T) cm(3) molecule(-1) s(-1), k(trans-C(4)F(8))(230-370 K) = 7.50 × 10(-14) × (T/298 K)(1.68) × exp(+612 K/T) cm(3) molecule(-1) s(-1), k(cis-C(4)F(8))(230-370 K) = 2.99 × 10(-14) × (T/298 K)(2.61) × exp(+760 K/T) cm(3) molecule(-1) s(-1), and k(C(6)F(12))(250-480 K) = 2.17 × 10(-15) × (T/298 K)(3.90) × exp(+1044 K/T) cm(3) molecule(-1) s(-1). The kinetics of the OH reaction in an industrial sample of octofluoro-2-propene (a mixture of the cis- and trans-isomers of CF(3)CF═CFCF(3)) was studied to determine the "effective" reaction rate constant for the typically industrial mixture: k(
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Environ Sci Pollut Res Int
December 2024
Departamento de Química Física, Facultad de Ciencias y Tecnologías Químicas, Universidad de Castilla-La Mancha, Avda. Camilo José Cela, 1B, 13071, Ciudad Real, Spain.
In this work, the rate coefficients for OH radical, k(T), and Cl atom, k(T), reaction with allyl 1,1,2,2-tetrafluoroethyl ether, CH=CHCHOCFCHF, were studied as a function of temperature and pressure in a collaborative effort made between UCLM, Spain, and LAPKIN, Greece. OH rate coefficients were determined in UCLM, between 263 and 353 K and 50-600 Torr, using the absolute rate method of pulsed laser photolysis-laser-induced fluorescence technique, while Cl kinetics were studied in temperature (260-363 K) and pressure (34-721 Torr) ranges, using the relative rate method of the thermostated photochemical reactor equipped with Fourier transform infrared spectroscopy as the detection technique. In both OH and Cl reactions, a negative temperature dependence of the measured rate coefficients was observed, which is consistent with complex association reactions.
View Article and Find Full Text PDFJ Phys Chem A
December 2024
ISM, UMR 5255, CNRS, Bordeaux INP, Université de Bordeaux, F-33400 Talence, France.
J Phys Chem A
December 2024
Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036, India.
The rate coefficients for the reactions for XO (XO, X = Cl, Br, I) + isoprene were calculated using the RRKM and ILT approach in master equation simulation (MESMER) in the temperature range of 200-400 K at 1 atm pressure. The thermochemical and energy parameters for ClO + isoprene were calculated using the CCSD(T)/aug-cc-pVDZ//B3LYP/6-31g(2df,p) theory. In the case of the BrO and IO radical reaction, all thermochemical parameters were calculated using CCSD(T)/AVDZ//M06-2X/AVDZ (AVDZ = aug-cc-pVDZ for C, H, and O atoms and aug-cc-pVDZ-pp for the Br atom with effective core potential (ECP) approximation) and CCSD(T)/AVDZ_ecp//M06-2X/AVDZ_ecp (AVDZ_ecp = aug-cc-pVDZ for C, H, and O atoms and Def2SVP for I atom with ECP), respectively.
View Article and Find Full Text PDFACS Earth Space Chem
October 2024
Departamento de Química Física, Facultad de Ciencias y Tecnologías Químicas, Universidad de Castilla-La Mancha, Avda. Camilo José Cela 1B, 13071 Ciudad Real, Spain.
Formamide (NHC(O)H) has been observed both in the interstellar medium (ISM), being identified as a potential precursor of prebiotic molecules in space, and in the Earth's atmosphere. In these environments where temperature is very distinct, hydroxyl (OH) radicals may play an important role in the degradation of NHC(O)H. Thus, in this work, we report for the first time the experimental study of the temperature dependence of the gas-phase removal of OH in the presence of NHC(O)H over the 11.
View Article and Find Full Text PDFJ Phys Chem A
September 2024
Department of Chemistry, University of California, Irvine, Irvine, California 92697, United States.
Criegee intermediates, formed by alkene ozonolysis in the troposphere, can react with volatile organic compounds (VOCs). The temperature-dependent kinetics of the reactions between the Criegee intermediate CHOO and three aliphatic aldehydes, RCHO where R = H, CH, and CH (formaldehyde, acetaldehyde, and propionaldehyde, respectively), have been studied using a laser flash-photolysis transient absorption spectroscopy technique. The experimental measurements are supported by calculations at various composite levels of theory that characterize stationary points on the reaction potential and free energy surfaces.
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