Thermal unimolecular decomposition of 1,1,2,2-tetrafluorocyclobutane

Abstract

The thermal decomposition of 1,1,2,2-tetrafluorocyclobutane has been studied in the gas phase in the temperature range 485–593°C and at pressures around 5–9 Torr. There are two homogeneous first order decomposition pathways, one yielding 1,1-difluoroethylene (k₁) and the other ethylene and tetrafluoroethylene (k₂). Arrhenius equations have been obtained for these processes viz.: log k₁/s^–1= 15.34 ± 0.05 –(292.0 ± 0.8 kJ mol^–1)/RT ln 10 log k₂/s^–1= 15.27 ± 0.06 –(308.1 ± 0.9 kJ mol^–1)/RT ln 10. The decomposition is almost certainly unimolecular and at the pressures studied the rate constants are close to their infinite pressure values. Rate constants were also determined from 22 to 0.01 Torr at 542.2 °C and the values obtained compared with those calculated using RRKM theory on the basis of various models. The energetics of the decomposition pathways are compared with cyclobutane and the fluorinated cyclobutanes.