Gas-Phase Chemistry of 1,1,2,3,3,4,4-Heptafluorobut-1-ene Initiated by Chlorine Atoms

The possibility of mitigating climate change by switching to materials with low global warming potentials motivates a study of the spectroscopic and kinetic properties of a fluorinated olefin. The relative rate method was used to determine the rate constant for the reaction of heptafluorobut-1-ene (CF₂=CFCF₂CF₂H) with chlorine atoms in air. A mercury UV lamp was used to generate atomic chlorine, which initiated chemistry monitored by FTIR spectroscopy. Ethane was used as the reference compound for kinetic studies. Oxidation of heptafluorobut-1-ene initiated by a chlorine atom creates carbonyl difluoride (CF₂=O) and 2,2,3,3 tetrafluoropropanoyl fluoride (O=CFCF₂CF₂H) as the major products. Anharmonic frequency calculations allowing for several low-energy conformations of 1,1,2,3,3,4,4 heptafluorobut-1-ene and 2,2,3,3 tetrafluoropropanoyl fluoride, based on density functional theory, are in good accord with measurements. The global warming potentials of these two molecules were calculated from the measured IR spectra and estimated atmospheric lifetimes and found to be small, less than 1.