A kinetic study of the thermal elimination of hydrogen fluoride from 1,2‐difluoroethane. Determination of the bond dissociation energies D(CH2FCH2F) and D(CH2FH).

The kinetics of the thermal elimination of HF from 1,2‐difluoroethane have been studied in a static system over the temperature range 734–820°K. The reaction was shown to be first order and homogeneous, with a rate constant of where θ = 2.303RT in kcal/mole. The A‐factor falls within the normal range for such reactions and is in line with transition state theory; the activation energy is similarly consistent with an estimate based on data for the analogous reactions of ethyl fluoride and other alkyl halides. The above activation energy has been compared with values of the critical energy calculated from data on the decomposition of chemically activated 1,2‐difluoroethane by the RRKM theory and the bond dissociation energy, D(CH2FCH2F) = 88 ± 2 kcal/mole, derived. It follows from thermochemistry that ΔHf0(CH2F) = ‐7.8 and D(CH2FH) = 101 ± 2 kcal/mole. Bond dissociation energies in fluoromethanes and fluoroethanes are discussed.