Nonequilibrium unimolecular reactions and collisional deactivation of chemically activated fluoroethane and 1,1,1-trifluoroethane

Abstract

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.

Thermal stability and bond dissociation energy of fluorinated polymers: A critical evaluation

“…It is interesting to compare our data with published pyrolysis studies of unimolecular elimination experiments on chemically activated mixed halogenated species [37][38][39][40][41][42][43][44][45][46][47][48]. In all these experiments HCl loss was dominant.…”

Mixed Quantum-Classical Reaction Path Dynamics of C2H5F → C2H4 + HF

“…Initially, chemically activated decomposition by radical recombination was performed to obtain dynamical data, [1][2][3][4][5][6][7][8][9][10][11] and shock tube pyrolysis was used to obtain kinetic data. 12,13 Later, product energy distributions were measured via infrared multiphoton dissociation (IRMPD) experiments.…”

Disproportionation reactions between alkyl and fluoroalkyl radicals. V. Perfluoro‐n‐propyl and ethyl radicals revisited

“…(11), it is assumed that the alternative disproportionation (cf., reaction (18)), (22) CsF7H6 + CsH5 -C6F7H7 + CzH4 is not contributing to ethylene formation at very low pressures of added propylene. However, in the experiment with 2 torr of added propylene (at least a 50-fold pressure increase over the runs recorded in Table IV), the system becomes primarily a n interaction between C2H5 and C6F7H6 radicals, so that we should expect reaction (22) to occur. In fact we found that the value of A(n-C3F7, C2H5) was far too large when calculated by eq.…”