Mechanistic and Kinetic Investigations on Decomposition of Trifluoromethanesulfonyl Fluoride in the Presence of Water Vapor and Electric Field.

As a potential insulation gas to replace sulfur hexafluoride (SF) due to environmental concerns, trifluoromethanesulonyl fluoride (CFSOF) has attracted great interests in various high-voltage electric applications. Thermal stability of CFSOF plays an important role in the rational design of the gas-insulated electric equipment. Unimolecular decomposition of CFSOF was investigated using high-level ab initio methods including the explicitly correlated RCCSD(T)-F12, the composite ROCBS-QB3, and the multireference RS2 extrapolated to complete basis set limit on the basis of M06-2X-, B2PLYPD3-, and CCSD-optimized geometrical parameters. Rate coefficients and decomposition temperatures were simulated using master equations. CFSOF decomposes predominantly via a simple C-S bond cleavage to form CF and SOF, accompanied by a roaming induced F-abstraction detour to release CF and SO, or isomerizes via CF migration to the more stable CFOSFO followed by the production of CFO and SOF. Various characteristic decomposition products (e.g., CF, CF, CFO, SO, SOF, SOF, CFH, and so on.) have been identified theoretically through secondary reactions and hydrolysis of CFSOF in the presence of water vapor. Electronic structures and stability of CFSOF could be affected significantly by the external electric field orientated along the S-C bond. The field-dependent electron-molecule capture rates support that CFSOF is superior to SF in dielectric strength. The present computational findings shed light on the practical use of CFSOF as the replacement gas for SF.