Theoretical study of the hydrolysis of sulfur tetrafluoride

Abstract

The reaction between sulfur tetrafluorine (SF4) and H2O was computationally investigated using the G4//MP2/6-311G(d, p) theoretical model. Among four reactive channels in the initial attack process, the primary path, which occurred via a SN2 displacement reaction to produce SF3OH, is the rate-determining step in the complete hydrolysis of SF4, resulting in the formation of SO2 (H2SO3). The energy barrier (i.e., 22.48kcalmol−1) in the gas phase will be substantially reduced when catalyzed by H2O and/or HF, and the Berry pseudorotation reaction (BPR) process of SF3OH becomes the rate-controlling step. The hydrolysis mechanism of SF4 in aqueous solution and the activation energy of the rate-determining step using the PCM model do not substantially change compared to the gas phase results. The hydrolysis of SF4 in an aqueous solution has a higher enthalpy. For secondary reactions in aqueous solution, the intermediates are prone to dehydrofluorination instead of hydrolysis. Although the activation energy of SOF2 hydrolysis is higher than that of SF4, the relative energy of the former is lower than that of the latter in aqueous solution. Therefore, SOF2 might be an important intermediate for the formation of SO2.