Theoretical Study Of H-atom Abstraction Reactions From CH₃CH₂OCH₂CH₃,CHF₂CF₂OCH₂CF₃ And CF₃CH₂OCH₃ By NO₃ Radical And Subse

The nocturnal reactions of CH₃CH₂OCH₂CH₃,CHF₂CF₂OCH₂CF₃ and CF₃CH₂OCH₃initiated by NO₃ radicals are important sources of alkyl radicals and nitric acids.In this paper,the thermodynamics and kinetics of CH₃CH₂OCH₂CH₃,CHF₂CF₂OCH₂CF₃ and CF₃CH₂OCH₃ induced by NO₃ radical in gas phase were studied in detail by BHandHLYP method combined with 6-311G?d,p?basis set,and the single point correction is calculated by relatively accurate CCSD?T?method.Thermodynamic calculations and kinetic data of the title reaction indicate that the H-abstraction reactions at the-OCH2-sites are the main reaction pathways.The thermodynamic and kinetic data of the reaction CH₃CH₂OCH₂CH₃,CHF₂CF₂OCH₂CF₃ with NO₃ radical show that the reaction activity could be reduced due to the addition of fluorine atoms,which is further verified by the enthalpies,Gibbs free energies of the title reactions and C-H bond dissociation energies of the CH3CH2OCH2CH3,CHF₂CF₂OCH₂CF₃ and CF₃CH₂OCH₃ molecules.By comparing the reaction rate constants of ethyl ether and its isomer methyl propyl ether with NO₃ radical at 293±2 K,the higher the symmetry is,the faster the reaction rate of ether is.The reaction thermodynamics and kinetics are determined,and the formation mechanisms of the products are proposed,which are crucial to determine the influence of CH₃CH₂OCH₂CH₃,CHF₂CF₂OCH₂CF₃ and CF₃CH₂OCH₃ on air quality,as well as its atmospheric lifetime and durability.All the rate constants calculated by the canonical variational transition state theory and the small curvature tunneling are basically consistent with the limited experimental data.In the temperature range of 200–400K,the title reaction rate constant is fitted to the three-parameter Arrhenius formula:k₁=2.64×10^-33T^6.41exp?-1143.86/T?k₂=2.83×10^-34T^6.43exp?-3123.53/T?k₃=1.08×10^-15T^0.61exp?-3002.26/T?The atmospheric lifetimes of CH₃CH₂OCH₂CH₃,CHF₂CF₂OCH₂CF₃ and CF₃CH₂OCH₃are evaluated in the NO₃-concentration range of 5×10⁸–2×10⁹ molecule cm^-3 to fully consider the effects of different regions on their nocturnal migration.The products of title reaction CH₃CHOCH₂CH₃,CF₃CHOCF₂CHF₂ and CF₃CHOCH₃ are further oxidized into organic nitrates in the presence of O₂ and NO.Organic nitrite ester can react in two ways,which can be isomerized into organic nitrite ester or degraded to form CH₃C?O?HOCH₂CH₃,CF₃C?O?HOCF₂CHF₂ and CH₃C?O?HOCF₃ alkoxy radicals and NO₂.This work provides deep insight into the night migration and transformation mechanism of the three ethers.