Reaction Ratesof OH Radicals with CH₃OCF₂CHFCF₃ and CHF₂CF₂OCH₂CF₂CHF₂: Measurements and EstimationUsing Neural Network Method

Abstract

The reaction rates of OH radicals with CH₃OCF₂CHFCF₃ (k₁) and CHF₂CF₂OCH₂CF₂CHF₂ (k₂) were measured over a temperature range of 250–430 K. Kinetic measurements were performed using the flash and laser photolysis methods combined with a laser-induced fluorescence technique. The Arrhenius rate parameters were determined as k₁ = (2.52 ± 0.25) × 10^–12·exp­[−(1390 ± 30)/T], k₂ = (1.83 ± 0.20) × 10^–12·exp­[−(1420 ± 35)/T] cm³ molecule^–1 s^–1. The infrared absorption spectra of the two hydrofluoroethers were measured at approximately 298 K in 760 Torr of N₂. The atmospheric lifetimes of CH₃OCF₂CHFCF₃ and CHF₂CF₂OCH₂CF₂CHF₂ have been estimated as 2.5 and 3.8 years, respectively, and their global warming potentials were determined as 245 and 405, respectively. Additionally, a method, using a three-layered feed-forward neural network, for estimating the rates of the reaction of the OH radicals with alkanes, ethers, and alcohols was investigated. The ratios of the calculated reaction rates to the observed ones agreed within a factor of 2. The ability of the neural network method to predict reaction rates was examined by using a leave-one-out test.