Department of Chemistry, Assam University, Silchar-788011, Assam, India.
Department of Chemical Sciences, Tezpur University, Tezpur-784028, Assam, India.
Environ Sci Process Impacts. 2024 Apr 24;26(4):734-750. doi: 10.1039/d3em00545c.
To give a comprehensive account of the environmental acceptability of 1,1,2,3-tetrafluoropropene (CFCF-CHF) in the troposphere, we have examined the oxidation reaction pathways and kinetics of CFCF-CHF 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 CFCF-CHF + 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, 1.21 × 10, and 1.13 × 10 cm per molecule per s the respective calculation methods 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 CFCF-CHF. 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 O and NO. From the degradation results, we have found that CF(Cl)COF, FCOCHF, FCFO and FCOCl are formed as stable end products along with various radicals such as ˙CFCl and ˙CHF. Therefore, these findings of kinetic and mechanistic data can be applied to the development and implementation of a novel CFC replacement.
为全面评估 1,1,2,3-四氟丙烯（CF3CF=CHF）在对流层中的环境可接受性，我们使用二阶 Møller-Plesset 微扰（MP2）理论和 6-31+G(d,p)基组，研究了 Cl 原子引发的 CF3CF=CHF 的氧化反应途径和动力学。我们还进行了单点能计算，以在 CCSD(T)水平以及基组 6-31+G(d,p)和 6-311++G(d,p)上进一步优化能量。CF3CF=CHF+Cl 反应的相对能量和热力学参数的估算清楚地表明，Cl-原子加成反应途径比 H 抽提反应途径更为占优势。使用传统过渡态理论（TST）在 1 atm 下于 200-1000 K 的温度范围内计算了每个反应通道的速率系数。使用分别为 MP2/6-31+G(d,p)、CCSD(T)//MP2/6-31+G(d,p)和 CCSD(T)/6-311++G(d,p)//MP2/6-31+G(d,p)的三种计算方法，在 298.15 K 下估算的标题反应的总速率系数分别为 1.10×10-12、1.21×10-12 和 1.13×10-12 cm3 分子-1 s-1。此外，计算的速率系数和分支比值表明，CF3CF=CHF 中β-碳原子上的 Cl-原子加成反应比α-碳原子加成反应更可取。基于三种不同方法计算的速率系数值，估算了该反应在 298.15 K 时的大气寿命。标题分子的辐射效率（RE）和全球变暖潜能（GWP）结果表明，其 GWP 可以忽略不计。此外，我们还研究了在存在 O 和 NO 时其产物自由基的降解。从降解结果中，我们发现形成了 CF(Cl)COF、FCOCHF、FCFO 和 FCOCl 等稳定的终产物，以及 ˙CFCl 和 ˙CHF 等各种自由基。因此，这些动力学和机理数据的研究结果可以应用于新型 CFC 替代品的开发和实施。
