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).

✍ Scribed by J. A. Kerr; D. M. Timlin

• Publisher: John Wiley and Sons
• Year: 1971
• Tongue: English
• Weight: 619 KB
• Volume: 3
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.550030505

✦ Synopsis

The kinetics of the thermal elimination of H F from 1,2-difluoroethane CHzFCHzF -+ CHz=CHF + H F have been studied in a static system over the temperature range 734-820'K. was shown to be first order and homogeneous, with a rate constant of The reaction log kz(s-l) = 13.39 f 0.2 -(62.9 f 0.9)/0 where e = 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 beenc ompared 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(CHZF-CH2F) = 88 f 2 kcal/mole, derived. It follows from thermochemistry that AHrO(CH2F) = -7.8 and D(CH2F-H) = 101 f 2 kcal/mole. Bond dissociation energies in fluoromethanes and fluoroethanes are discussed.