Unimolecular reactions of 1,1,1-trichloroethane, 1,1,1-trichloropropane, and 3,3,3-trifluoro-1,1,1-trichloropropane: determination of threshold energies by chemical activation.

The recombination of CCl3 radicals with CH3, CH3CH2, and CF3CH2 radicals was used to generate CH3CCl3, CH3CH2CCl3, and CF3CH2CCl3 molecules with approximately 87 kcal mol(-1) of vibrational energy in a bath gas at room temperature. The competition between collisional deactivation and unimolecular reaction by HCl elimination was used to obtain the experimental rate constants for each molecule. These experimental rate constants were matched to calculated statistical unimolecular rate constants to assign threshold energies to the three HCl elimination reactions.

Effects of CF(3) and CH(3) groups on the threshold energy for the unimolecular interchange reaction of Cl- and F-atoms in CF(3)CHFCH(2)Cl and CH(3)CHFCH(2)Cl.

The recombination reactions of CH2Cl radicals with CF3CHF and with CH3CHF radicals were used to generate CF3CHFCH2Cl and CH3CHFCH2Cl molecules with 90-92 kcal mol(-1) of vibrational energy. The experimental rate constants for elimination of HCl and HF and the interchange of Cl and F atoms were measured and compared to RRKM calculated rate constants to assign the threshold energy for each unimolecular reaction channel. The Cl/F interchange reaction is approximately 18% of the total unimolecular reaction for both molecules.