Computational study of the atmospheric oxidation and global warming potential of thionyl fluoride

Abstract

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 O2 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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 O2 produce HO2 and SO2F2 predominantly via the concerted S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/m2/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.