We show that a single, reasonable assumption about the probability of rearrangements in a supercooled liquid necessarily implies a direct connection between kinetic and thermodynamic observables in these media. The prediction is tested against available experimental data for supercooled liquids spanning the range of observed kinetics.

Highly vibrationally excited fluoroethane and 1,1,1-trifluoroethane molecules were generated by combination of CH2F and CF3 radicals with CHS. The radicals were produced by cophotolysis of acetone and 1,3-difluoroacetone and by photolysis of trifluoroazomethane. The nonequilibrium unimolecular rate constant for HF elimination from CH3CH2F* was measured using the acetone mixture as the bath gas. The rate constants for CH3CF3* were measured with C2F6, CH3N2CF3, c-C4F8, C6Fi4, and C8Fi8 as bath gases. RRKM calculations were done using a four-centered activated complex model and currently favored thermochemical values; good agreement was found between the calculated and both thermal and chemical activation rate constants for CH3CH2F. For the high Z>(CH3-CF3) value of ~99 kcal mol-1, the chemical activation data support a high threshold energy, 68 ± 2 kcal mol-1, for HF elimination from CH3CF3. RRKM calculations for the dissociation reactions of CH3CF3* and CH3CH2F* indicate that radical dissociation should compete with HF elimination at energies near 110 kcal mol-1. The low pressure data for CH8CF3* were analyzed according to a cascade stepladder deactivation model to obtain estimates of the average energy lost per collision. An upper limit of 10-12 kcal mol-1 is implied for even the larger bath gas molecules.

The photochemistry of 1 ,l , 1-trifluoromethylazomethane has been partially characterized. The quantum yield for Nz formation from photolysis at 366 nm and room temperature was unity at low pressure and decreased to 0.5 at 630 torr. At room temperature the principal products were C2H6, C2F6, CH3CF3 (or CHzCFz + HF at reduced pressures), plus substituted hydrazines, which mainly arise from addition of CF3 to the parent followed by combination of these radicals with CH3 or CF3. These fluorinated methyl hydrazine products detract from the general utility of CFa-N2-R compounds as sources for simultaneous study of the chemistry of CF3 and R radicals. At room temperature the hydrazine products accounted for more than 50% of the total yield; however, these products can be reduced by lowering the temperature and at 195°K their yields are negligible. The quantum yield for intramolecular (direct) formation of CH3CF3 + NZ was shown to be <0.002.

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