Kinetic isotope effects in the dehydrofluorination of chemically activated 1,1,1-trifluoroethane

Abstract

Hexafluoroacetone was cophotolyzed with acetone and with acetone-dg, and the rate of the unimolecular dehydrofluorination of the 1,1,1-trifluoroethanes formed from combination of CFg and CHg or CDs radicals was determined from the difluoroethene/trifluoroethane ratio. This ratio was found to depend on the extent of conversion because of secondary reactions. Extrapolations to zero conversion corrected for this effect. The measured kinetic isotope effect was found to be 2.84 ± 0.07. Values of the isotope effect and rate constants predicted by applying RRKM theory to two different models of• the activated complex show that both models predict results similar to observations.

A reformulation of the theory of unimolecular reactions

“…Most importantly, although much emphasis is placed upon the selection of a hypothetical reaction coordinate and the corresponding activated complex, it hardly matters what reaction coordinate is chosen (5,7,8) because the calculated fall-off behaviour is very innate d o not appear, and it becomes evident in the later discussion (section XIB) that the puzzle surrounding collision efficiencies is part experimental in origin, and part a matter of theoretical interpretation.…”

A Novel Ni/NiF2‐AlF3 Catalyst with Mild‐Strength Lewis Acid Sites for Dehydrofluorination of 1, 1, 1, 2‐Tetrafluoroethane to Synthesize Trifluoroethylene

“…Also, the activation of Ni on dehydrofluorination is important. For the dehydrofluorination of HFCs, the cleavage route of C−F and C−H bond is hemolysis and heterolysis ,. Whatever the cleavage route of C−X, the rapid cleavage of C−H is beneficial to dehydrofluorination.…”

“…For the dehydrofluorination of HFCs, the cleavage route of CÀ F and CÀ H bond is hemolysis and heterolysis. [28,29] Whatever the cleavage route of CÀ X, the rapid cleavage of CÀ H is beneficial to dehydrofluorination. On the study of Ni and/or supported catalyst for heterogeneous catalysis, metal Ni could act as efficiently activation of CÀ H bond.…”

Radiation‐induced hydrogen fluoride formation in fluorine‐containing ethanes and ethenes

“…The formation of H F from fluoroethanes C2H,F, in gas phase reactions has been reported from photolysis [ 12,131, chemical activation experiments [14][15][16][17][18][19], and shock tube investigations [20-231. A generally accepted reaction mechanism involves the formation of a vibrationally excited fluoroethane molecule which subsequently may eliminate an H F molecule [reaction (l)] or undergo collisional stabilization [reaction (2)] :…”