Isodesmic reactions and thermochemistry of ions

Thermochemical determination of the structure of negative ions on the basis of data from resonance electron capture mass spectrometry. Phenol, its chlorinated derivatives and a thioanalogue

“…However, from Scheme it is quite clear that the introduction of a stronger electron‐withdrawing (or more exactly more polarizable) group gives better stability to the less stable, in this case O‐centered, negative ion. In other words, the less stable ion (with more localized negative charge) extracts the higher stabilization effect from the same substituent compared with more stable ion species Similar tendencies were found previously for positive ions6–8 and free radicals 5,. 6 From Scheme we derive, by interpolation, the EA ( p ‐Cl 6 H 4 S · ) ≈2.8 eV.…”

Detection of Chlorobenzene Derivatives Using Vacuum Ultraviolet Ionization Time-of-Flight Mass Spectrometry

“…The appearance potentials of C6H4X + ions are more than 12 eV, which are much higher than the photon energy of 10.2 eV used in the present study. [26][27][28][29][30][31][32][33][34] Thus, fragmentation-free measurements of the mass spectra for chlorobenzene derivatives are expected in the SPI at 10.2 eV. Figure 2 shows the mass spectra of chlorobenzene, o-dichlorobenzene, and o-chlorophenol obtained by the SPI at 10.2 eV.…”

Isotope Effects and Final Products in Pyrolysis of Halomethanes and Perfluoroalkyl Iodides

“…The sharp difference between the new (4) and old (2) enthalpies of formation of the free ethyl radical frustrates the entire system [4,5] of thermochemical data. Some authors [8310] still try to use the old values (1) and (2), accepting a compromise value (5), but the rigorous quantummechanical calculation [11] provides an even higher value (6), which makes hopeless not only preservation of the obsolete value (2), but also of the compromise value (5).…”

“…The enthalpy of formation of the free biradical CFBr .. (D f H 0 0 = 80 + 20, D f H 0 298 = 60 + 20 kJ mol 31 ) was estimated. The dissociation energies E D,0 (ID 2 C3D), E D,298 (ID 2 C3D), and E D,0 (IH 2 C3D) equal to 437 + 6, 444 + 6, and 435 + 4 kJ mol 31 , respectively, were determined.Over almost half a century the standard enthalpies of formation of methyl and ethyl radicals have been accepted [133] to equal values (1) and (2).These values as well as some others have been used as the basis of the interpolation network [4,5] of thermochemical data, including many dozens of molecules and free radicals. However, recently new experimental methods [6,7] have led to much higher values (3) and (4).…”

“…These values as well as some others have been used as the basis of the interpolation network [4,5] of thermochemical data, including many dozens of molecules and free radicals. However, recently new experimental methods [6,7] have led to much higher values (3) and (4).…”