TY - JOUR
T1 - Tetrafluorobenzyne thermochemistry
T2 - Experiment and theory
AU - Pratt, Lawrence M.
AU - Fattahi, Alireza
AU - Kass, Steven R
PY - 2004
Y1 - 2004
N2 - 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
AB - 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
UR - http://www.scopus.com/inward/record.url?scp=17444385927&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=17444385927&partnerID=8YFLogxK
U2 - 10.1255/ejms.699
DO - 10.1255/ejms.699
M3 - Article
C2 - 15775041
AN - SCOPUS:17444385927
SN - 1469-0667
VL - 10
SP - 813
EP - 818
JO - European Journal of Mass Spectrometry
JF - European Journal of Mass Spectrometry
IS - 6
ER -