Oxidation pathways and kinetics of the 1,1,2,3-tetrafluoropropene (CF2CF–CH2F) reaction with Cl-atoms and subsequent aerial degradation of its product radicals in the presence of NO

Abstract

To give a comprehensive account of the environmental acceptability of 1,1,2,3-tetrafluoropropene (CF₂CF–CH₂F) in the troposphere, we have examined the oxidation reaction pathways and kinetics of CF₂CF–CH₂F initiated by Cl-atoms using the second-order Møller–Plesset perturbation (MP2) theory along with the 6-31+G(d,p) basis set. We also performed single-point energy calculations to further refine the energies at the CCSD(T) level along with the basis sets 6-31+G(d,p) and 6-311++G(d,p). The estimation of the relative energies and thermodynamic parameters of the CF₂CF–CH₂F + Cl reaction clearly shows that Cl-atom addition reaction pathways are more dominant compared to H-abstraction reaction pathways. The value of the rate coefficient for each reaction channel is calculated using the conventional transition state theory (TST) over the temperature range of 200–1000 K at 1 atm. The estimated overall rate coefficients for the title reaction are found to be 1.10 × 10⁻¹², 1.21 × 10⁻¹⁰, and 1.13 × 10⁻⁸ cm³ per molecule per s via the respective calculation methods viz. MP2/6-31+G(d,p), CCSD(T)//MP2/6-31+G(d,p), and CCSD(T)/6-311++G(d,p)//MP2/6-31+G(d,p), at 298.15 K. Moreover, the calculated rate coefficients and percentage branching ratio values suggest that the Cl-atom addition reaction at the β-carbon atom is more preferable to that of the α-carbon addition to CF₂CF–CH₂F. Based on the rate coefficient values calculated by the three different methods, the atmospheric lifetime for the title reaction at 298.15 K is estimated. The radiative efficiency (RE) and Global Warming Potential (GWP) results of the title molecule show that its GWP would be negligible. Further, we have explored the degradation of its product radicals in the presence of O₂ and NO. From the degradation results, we have found that CF₂(Cl)COF, FCOCH₂F, FCFO and FCOCl are formed as stable end products along with various radicals such as ˙CF₂Cl and ˙CH₂F. Therefore, these findings of kinetic and mechanistic data can be applied to the development and implementation of a novel CFC replacement.