title: Tetrafluorobenzyne thermochemistry: experiment and theory.
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 H(2) (DeltaH degree (hyd) = 367 +/- 18 kJ mol(-1)) and the first and second CH 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.
authors.affiliation: Department of Chemistry, Fisk University, Nashville, TN 37208, USA.
authors.forename: Lawrence M
authors.initials: LM
authors.lastname: Pratt
authors.forename: Alireza
authors.initials: A
authors.lastname: Fattahi
authors.forename: Steven R
authors.initials: SR
authors.lastname: Kass
mesh_terms: D015195:Drug Design; D005464:Fluorobenzenes / Q000737:chemistry*; D005583:Fourier Analysis; D013058:Mass Spectrometry / Q000379:methods; D013816:Thermodynamics
chemical_list: D005464:Fluorobenzenes