Shock Tube Study of the Decomposition Kinetics of SO2F2

Recent thermal decomposition studies of SF6 have led to interest in its principal oxidation product, sulfuryl difluoride. In the present study the thermal stability of SO2F2 at high temperatures has been investigated. Highly dilute SO2F2–Ar mixtures (∼ 0.1%) were shock heated in a conventional 1.5″ stainless-steel shock tube. The SO2F2 concentration was monitored as a function of time behind the incident shock wave by its infrared emission at 11.7 μ utilizing a liquid helium cooled Cu:Ge detector. The initial pressure in the shock tube was varied from 30 to 600 torr and the temperature range covered was 1900–2300°K. The monitored radiation was shown to be transparent over the range of densities employed. Effective first-order rate constants were evaluated from the logarithmic initial slopes of the radiation decay curves. For the 30-torr data, a unimolecular rate constant fit to the data is keff = 2.1 × 1011exp(− 39 200 / T) sec−1. The data are analyzed in the light of several modern unimolecular rate theories, yielding ∼ 81 kcal as the endothermicity for the reaction SO2F2+Ar→SO2F+F+Ar.