Multiconformer transition state theory rate constants for the reaction between OH and α,ω-dimethoxyfluoropolyethers

In this work, we have calculated rate constants for the tropospheric reaction between the OH radical and alpha,omega-dimethoxyfluoropolyethers. The latter are a specific class of the hydrofluoropolyethers family with the general formula CH3(OCF2CF2)(p)(OCF2)(q)OCH3, from which we have selected three case studies: p0q2, p0q3, and p2q0. The calculations were performed by applying a cost-effective protocol developed for bimolecular hydrogen-abstraction reactions and based on multiconformer transition state theory relying on computationally accessible M08-HX/apcseg-2//M08-HX/pcseg-1 calculations. Within the protocol's uncertainties and approximations, the results show that (1) the calculated rate constants have the same order of magnitude and (2) if observed together with previous experimental and theoretical investigations, the chain length (that varies with q and p) is seen to have a small effect on the rate constant, which is consistent with the "no discernible effect" reported in the experimental work.