MULTISTEP COLLISIONAL DEACTIVATION OF HIGHLY VIBRATIONALLY EXCITED 1,1,2-TRIFLUORO-2-(TRIFLUOROMETHYL)CYCLOPROPANE

The reaction of CH2(1A1) with C3F6 was investigated at 298 K and pressures between 50 and 1428 Torr by using TMS as the internal standard. Also, some runs were done without TMS at low pressures. Chemically activated 1,1,2-trifluoro-2-(trifluoromethyl)cyclopropane was formed with an average energy of about 57 kcal/mol above the threshold energy for decomposition to CF2 and CF3CF=CH2. A significant dependence of the experimental specific rate constant for unimolecular decomposition with pressure was observed, which is indicative of a multistep collisional deactivation process. Also at pressures higher than 600 Torr, the rate constants increased with increasing pressure as a result of the failure of complete internal energy relaxation of the nascent activated molecule. The data could be fitted to a stepladder model with down-energy loss of about 4 kcal/mol and with a minimum energy of the activated molecule of 100 ± 2 kcal/mol. Some experiments with CO2 as the main collisional partner gave a down-energy loss of about 2.5 kcal/mol. © 1990 American Chemical Society.