Thermal Decomposition of 2,3,3,3- and trans-1,3,3,3-Tetrafluoropropenes

The thermal decomposition reactions of 2,3,3,3- and trans-1,3,3,3-tetrafluoropropenes (TFPs) have been studied both experimentally and computationally to elucidate their kinetics and mechanism. The experiments were performed by observing the temporal profiles of HF produced in the decomposition of the tetrafluoropropenes behind shock waves at temperatures of 1540-1952 K (for 2,3,3,3-TFP) or 1525-1823 K (for trans-1,3,3,3-TFP) and pressure of 100-200 kPa in Ar bath. The reaction pathways responsible for the profiles were explored based on quantum chemical calculations. The decomposition of 2,3,3,3-TFP was predicted to proceed predominantly via direct 1,2-HF elimination to yield CHCCF₃, while trans-1,3,3,3-TFP was found to decompose to HF and a variety of isomeric C₃HF₃ products including CHCCF₃, CF₂CCHF, CCHCF₃, and CF₂CHCF. The C₃HF₃ isomers can subsequently decompose to either CF₂ + CHCF or CF₂CC + HF products. Multichannel RRKM/master equation calculations were performed for the identified decomposition channels. The observed formation rates and apparent yields of HF are shown to be consistent with the computational predictions.