Tetrafluorobenzyne thermochemistry: Experiment and theory

Lawrence M. Pratt, Alireza Fattahi, Steven R Kass

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

Gas-phase thermodynamic properties of 1,2,3,4-tetrafluorobenzyne (1-H 2) were determined by Fourier transform mass spectrometry and ab initio and density functional theory methods. 1,2,3,4-Tetrafluorobenzyne radical anion was generated by abstraction of a proton and a hydrogen atom upon reaction of 1,2,3,4-tetrafluorobenzene (1) with O-.. The resulting structure was confirmed by converting it to a species which could be independently prepared. Bracketing results provided the proton affinity of 1,2,3,4-tetrafluorobenzyne radical anion and the electron affinities of 1,2,3,4-tetrafluorobenzyne and 1,2,3,4-tetrafluorophenyl radical. These measured values were combined in a thermodynamic cycle to provide the heat of hydrogenation of 1-H2 (ΔH°hyd = 367 ± 18 kJ mol-1) and the first and second C-H bond dissociation energies of 1 (481 ± 11 and 321 ± 13 kJ mol -1). The same approach failed for the meta and para isomers, but their energetics were examined using B3LYP and CCSD(T) computations. Keywords: FT-MS, benzyne, thermochemistry, bond dissociation energies, radical anions, computations

Original languageEnglish (US)
Pages (from-to)813-818
Number of pages6
JournalEuropean Journal of Mass Spectrometry
Volume10
Issue number6
DOIs
StatePublished - Dec 1 2004

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