A structural, mechanistic, and kinetic study of the dehydrofluorination of 1,1,1,3,3-pentafluoropropane in the absence of catalyst

The catalyst-free dehydrofluorination of 1,1,1,3,3-pentafluoropropane (HFC-245fa) was investigated both experimentally and theoretically to elucidate the mechanism and kinetics of the reaction. The experimental results demonstrated easier generation of E-1,3,3,3-tetrafluoropropene (HFO-1234ze(E)) than HFO-1234ze(Z) under the same reaction conditions within a temperature range of 500–700 °C. When analyzing the geometry, energetics, and kinetic modeling of the reaction at the B3LYP/6−311++G (d,p) level of theory, it was found that the thermodynamic stability of HFO-1234ze(E) is relatively higher than its isomer (HFO-1234ze(Z). Besides, the rate constants of HFO-1234ze(E) were always larger than those of HFO-1234ze(Z) at 400–2000 K, which agreed well with the higher selectivity of HFO-1234ze(E) in the synthetic experiment results. Our theoretical demonstration provides a reference to investigate the mechanism and kinetics of other analogous reactions.