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Analysis of the kinetics of the thermal and chemically activated elimination of HF from 1,1,1‐trifluoroethane: the CC bond dissociation energy and the heat of formation of 1,1,1‐trifluoroethane
Author(s) -
Rodgers Alan S.,
Ford W. G. F.
Publication year - 1973
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550050606
Subject(s) - chemistry , kinetics , bond dissociation energy , kinetic energy , dissociation (chemistry) , yield (engineering) , radical , bond energy , atmospheric temperature range , activation energy , computational chemistry , thermodynamics , organic chemistry , molecule , physics , quantum mechanics
The thermal, unimolecular elimination of HF from CH 3 CF 3 was studied by three different groups over the temperature range 1000° to 1800°K. While the reported kinetic parameters varied greatly, it is shown here that these data may be satisfactorily correlated in terms of a four‐center transition state. This correlation results in Δ E 00 + += 69.2 kcal/mol, and log ( k / s −1 ) = 14.6 – 72.6/θ. These results may then be combined with the kinetics of the chemically activated elimination of HF from CH 3 CF 3 formed by the recombination of methyl and trifluoromethyl radicals. The data from three different laboratories are shown to be in excellent agreement. These data, combined with extant thermal data, yield as a best value DH 0 0 (CH 3 CF 3 ) = 99.6 ± 1.1 kcal/mol. This gives the unexpectedly high value of DH 298 °(CH 3 CF 3 ) = 101.2 ± 1.1 kcal/mol. It is suggested that dipoledipole interactions, primarily in CH 3 CF 3 , account for this surprisingly strong CC bond dissociation energy. These results also yield δ H f 0 (CH 3 CF 3 ; g, 298) = −178.6 ± 1.5 kcal/mol.