Computational Study of the Atmospheric Oxidation and Global Warming Potential of Thionyl Fluoride

Thionyl fluoride (SOF2) is the dominant decomposition by-product in SF6 under electrical discharges and a novel fluorinating reagent for organic synthesis to replace sulfuryl fluoride (SO2F2). Since both SF6 and SO2F2 are strong green-house gases, for the sake of environmental concern, tropospheric oxidation of SOF2 by OH radicals in the presence of O-2 has been investigated using various computational methods including density functional M06-2X, coupled-cluster (CCSD), the explicitly correlated RCCSD(T)-F12, Gaussian-4, ROCBS-QB3, and Weizmann-1 theories. The S(sic)O bond association between SOF2 and OH proceeds via the barriers of 1-3 kcal/mol to form various shallow wells HOSOF2 (-3 to -8 kcal/mol) linked by Berry pseudorotations and followed by HF-elimination. Interception of the HOSOF2 adducts by O-2 produce HO2 and SO2F2 predominantly via the concerted S(sic)O bond association/dissociation and proton-transfer. The atmospheric lifetime and radiative efficiency for SOF2 were calculated to be 1.2-1.5 years and 0.223 W/m(2)/ppb, respectively. The global warming potential of SOF2 was estimated to be 169-211, as indicative of an eco-friendly gas. However, the environmental impact of SOF2 should take into account the production of SO2F2 and HO2 due to oxidation.