Multiconformer transition state theory rate constant and branching ratios for the OH-initiated reaction of CH3OCF2CHF2 and its primary product, HC(O)OCF2CHF2

Obtaining rate constants and branching ratios for the atmospheric degradation of organic compounds is crucial for their environmental assessment and for a deeper understanding of their atmospheric chemistry and reactivity. The theoretical prediction of such quantities is a challenging endeavor that grows with conformational complexity. In this work, we have theoretically calculated the rate constants and branching ratios for the tropospheric OH-initiated oxidation reactions of the CH3OCF2CHF2 hydrofluoroether and its primary product, the HC(O)OCF2CHF2 fluorinated ester. The calculations were performed with a cost-effective multiconformer transition state theory protocol employing the recently developed constrained transition state randomization method. The calculated k(HO center dot + CH3OCF2CHF2) =1.6 x 10(-14) cm(3) molecule(-1) s(-1) rate constant lies within the error bars of the recommended experimental value, while the calculated rate coefficient of k(HO center dot + HC(O)OCF2CHF2) 2.6 x 10(-14 )cm(3) molecule(-1) s(-1) represents, to our knowledge, the first determination of this reaction's rate constant. The results provide new insight and elucidate the main mechanistic issues discussed in recent experimental work while they also encourage the use of this protocol in investigations of the tropospheric reactivity of other fluorinated organic compounds.