Atmospheric Oxidation of Fluorinated Ethers, E143a (CF₃OCH₃), E134 (CHF₂OCHF₂), and E125 (CHF₂OCF₃)

Abstract

The atmospheric oxidation mechanisms of E143a (CF3OCH3), E134 (CHF2OCHF2), and E125 (CHF2OCF3) have been investigated using experimental and ab initio methodology. The oxidation of E143a produces the stable reservoir species trifluoromethyl formate, CF3OCOH, which further oxidizes to CF2O and CO2. Oxidation of E134 and E125 shows the presence of only CF2O under the condition of high O2 concentrations. Carbonyl fluoride can be formed from two competing pathways involving the halogenated alkyl radicals formed from hydrogen abstraction of E134 and E125. CO bond fission reactions and O2 addition reactions compete to produce carbonyl fluoride and a CF x H3 - x radical fragment. Computational modeling of the reaction pathways provides insight into the molecular steps of the degradation process.

The Trifluoromethoxy Carbonyl Peroxy Radical CF3OC(O)OO

“…While the related species CF 3 C(O)OO is partly characterized, [20,21] to our knowledge no data are available for CF 3 OC(O)OO. The peroxy radical CF 3 OC(O)OO is postulated in studies of the atmospheric degradation of CF 3 OCH 3 , [22,23] which leads first to CF 3 The trifluoromethyl formate can also be attacked by Cl atoms or OH radicals with subsequent addition of molecular oxygen as seen in Equations (4) and (5): [22,23] CF 3 OC(O)H X 3 CF 3 OCO HX (X OH, Cl) (4)…”

Assessment of theoretical methods for the study of hydrogen abstraction kinetics of global warming gas species during their degradation and byproduct formation (IUPAC Technical Report)

“…Good et al [171] used experimental and theoretical methods to understand the atmospheric oxidation of CF 3 OCH 3 , CHF 2 OCHF 2 , and CHF 2 OCF 3 . These compounds are oxidized to trifluoromethyl formate, and then CF 3 OCH 3 is further oxidized to carbonyl difluoride and carbon dioxide, while CHF 3 OCHF 2 and CHF 2 OCF 3 are converted to carbonyl fluoride only.…”

Hydrogen-Atom Abstraction Reaction of CF3CH2OCF3by Hydroxyl Radical

“…12 Therefore, considerable attention has been paid in recent years to perform experimental and theoretical studies on the decomposition kinetics of HFEs. [13][14][15][16] Tropospheric degradation is expected to be initiated mainly by the attack of OH radicals in the gas phase 17 and CF 3 CH 2 OCF 3 (HFE-246cb2) may undergo H atom abstraction as follows.…”