Cl-Initiated Oxidation Mechanism and Thermochemistry of Trifluoromethyl Methyl Ether CH3OCF3(HFE- 143a): An Insight from DFT Study

Review Article

Austin Environ Sci. 2019; 4(2): 1040.

Cl-Initiated Oxidation Mechanism and Thermochemistry of Trifluoromethyl Methyl Ether CH3OCF3(HFE- 143a): An Insight from DFT Study

Subrata Paul1, Satyajit Dey Baruah1, Gargi Goswami2, Ritika Borah2, Nand Kishor Gour1* and Ramesh Chandra Deka1*

¹Department of Chemical Sciences, Tezpur University Tezpur, Assam, India

²Department of Chemistry, Darrang College Tezpur, Assam, India

*Corresponding author: Nand Kishor G and Ramesh Chandra D, Department of Chemical Sciences, Tezpur University Tezpur, Assam, India

Received: December 02, 2019; Accepted: December 17, 2019; Published: December 24, 2019


In this work, we have performed theoretical investigations on the oxidation of trifluoromethyl methyl ether (CH3OCF3) molecule initiated by Cl atom using the Density Functional Theory (DFT) method. Here we have constructed an energy profile diagram for the three reaction channels viz. CH3OCF3 + Cl → C•H2OCF3 + HCl (R1), CH3OCF3 + Cl → CH3O• + CF3Cl (R2) and CH3OCF3 + Cl → CF3O• + CH3Cl (R3) along with the transition states at M06-2X/6-31+G (d,p) level of theory. Our energy profile result shows that R1 channel is found to be the lowest energy barrier reaction as compared to the other two channels. Thermochemical results also suggest that the product of R1 reaction is more stable than others. In addition to this, we have also determined heats of formation (Δf298) using isodesmic reactions method and Bond Dissociation Energy (BDE) of CH3OCF3 molecule. The value of Δf298 and BDE of the molecule are found to be good agreement with the value reported in the literature.

Keywords: HFE; DFT; Isodesmic; Heat of formation; BDE


Hydrofluoroethers (HFEs) are a class of non-ozone depleting organic compounds. They serve as an alternative to Chlorofluorocarbons (CFCs), Hydrofluorocarbons (HFCs), and Hydrochlorofluorocarbons (HCFCs) for a wide range of commercial applications such as cleaning of electronic equipment, heat transfer fluid in refrigerators, lubricant deposition and foam blowing agents. Chlorine and bromine atoms are responsible for ozone depletion which remains absent in HFE [1,2]. The C-F bonds of HFEs absorb infrared radiation, thus acting as greenhouse gases [3]. Consequently, HFEs are considered to be the potential candidate for the global warming effect. In general, the HFEs having C-H bond, happens to get oxidized in the atmosphere by highly reactive radical species, such as OH radical and Cl atom. These reactions constitute the initial step of their degradation and thus results in short atmospheric lifetimes and Global Warming Potentials (GWPs) reducing their environmental impact. Also, the presence of an ether (-O-) linkage in HFEs enhances their reactivity in the troposphere, resulting in a shorter atmospheric lifetime which limits their accumulation in the atmosphere and decreases their potential impact as greenhouse gases [4]. Numerous studies on HFEs with OH radical has been explored both theoretically and experimentally [5-7]. The study of HFEs with Cl atom is also important in the marine regions, which can not be ignored. There are very limited studies are reported in the literature in this regard.

In the present work, we aim to address the degradation pathways of the trifluoromethyl methyl ether (CH3OCF3) with Cl atom using the quantum chemical method. The reaction between CH3OCF3 and Cl atom will proceed by H-atom abstraction as well as Cl atom addition and C-O bond breaking, leading to the formation of alkyl and alkoxy radicals. The following reactions are considered for the study and shown in Scheme 1.