Multistep Collisional Deactivation of Highly Vibrationally Excited 1,1,2,2-Tetrafluorocyclopropane

Article abstract of DOI:10.1021/j100243a024

The reaction of CH2(¹A1) with C2F4 was investigated at 298 K and pressures between 66 and 1837 torr.Chemically activated 1,1,2,2-tetrafluorocyclopropane was formed with an energy of about 41 kcal/mol above the threshold energy for decomposition to CF2 and CF2CH2.A significant dependence of the experimental specific rate constant for unimolecular decomposition with pressure was observed and is indicative of a multistep collisional deactivation process.The data could be fitted to a stepladder model, with down-energy loss of about 9 kcal/mol and with a minimum energy for the activated molecule of 85 +/-2 kcal/mol.In these experiments C2F4 is the major collision partner and the limiting high-pressure region could not be reached.With this value and the known heats of formation of CH2(¹A1) and C2F4, the heat of formation of tetrafluorocyclopropane was estimated to be ΔH_f^o ca. -140 kcal/mol.