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 6 ) due to environmental concerns, trifluoromethanesulonyl fluoride (CF 3 SO 2 F) has attracted great interests in various high-voltage electric applications. Thermal stability of CF 3 SO 2 F plays an important role in the rational design of the gas-insulated electric equipment. Unimolecular decomposition of CF 3 SO 2 F 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. CF 3 SO 2 F decomposes predominantly via a simple C-S bond cleavage to form CF 3 and SO 2 F, accompanied by a roaming induced F-abstraction detour to release CF 4 and SO 2 , or isomerizes via CF 3 migration to the more stable CF 3 OSFO followed by the production of CF 2 O and SOF 2 . Various characteristic decomposition products (e.g., CF 4 , C 2 F 6 , CF 2 O, SO 2 , SOF 2 , SO 2 F 2 , CF 3 H, and so on.) have been identified theoretically through secondary reactions and hydrolysis of CF 3 SO 2 F in the presence of water vapor. Electronic structures and stability of CF 3 SO 2 F could be affected significantly by the external electric field orientated along the S-C bond. The field-dependent electron-molecule capture rates support that CF 3 SO 2 F is superior to SF 6 in dielectric strength. The present computational findings shed light on the practical use of CF 3 SO 2 F as the replacement gas for SF 6 .