Chemical mechanism and atmospheric degradation of C4F9N initiated by OH radical: Ab initio kinetic exploration

This work presents a thoroughgoing theoretical study on the OH-initiated combustion chemical kinetics and atmospheric degradation mechanism of C4F9N by employing high-level quantum chemical methods and RRKM/master-equation theory. Stationary points on potential energy surface were cautiously investigated at B3LYP/6-311++G(d,p) level for geometry optimizations, and thereby their single-point energies were refined by applying CCSD(T)/6-311++G(d,p) method. Based on quantum calculations, kinetics and branching ratios for the major channels were predicted within 300-3000 K and 0.01-100 atm by solving the RRKM/master-equations. The OH addition to C4F9N generating M1 dominates the overall kinetics at low temperatures. Subsequently, its two beta-scission channels of C-C bonds to CF3CF2N(sic)CF(OH) + CF3 and CF2(sic)NCF(OH)CF3 + CF3 become competitive and play a lead role in whole C4F9N + OH system at the corresponding high temperatures and elevated pressures. The CF3 radical generated prompts these two routes to potentially have the significant contribution to flame inhibition in actual applications. Additionally, the complex degradation pathways of C4F9N were also looked into by successively reacting with various oxides, including OH, O-2, NO, and HO2, to finally generate the removal products CF3CF2N(OOH)CF(OH)CF3, CF3CFO, and CF3CF2NO. The atmospheric lifetime of C4F9N was evaluated as 49 years regarding to the kinetic for one step addition of OH radical.

Automated summary

This work presents a comprehensive theoretical study on the OH-initiated combustion chemical kinetics and atmospheric degradation mechanism of C4F9N using high-level quantum chemical methods and RRKM/master-equation theory. The study shows that at low temperatures, the OH addition to C4F9N dominates the kinetics, while at high temperatures and pressures, the beta-scission channels of C-C bonds become competitive and play a lead role. Additionally, the complex degradation pathways of C4F9N through reactions with various oxides were investigated, and the atmospheric lifetime of C4F9N was evaluated.