Heats of Formation of C6H5•, C6H5+, and C6H5NO by Threshold Photoelectron Photoion Coincidence and Active Thermochemical Tables Analysis

Threshold photoelectron photoion coincidence has been used to prepare selected internal energy distributions of nitrosobenzene ions [C6H5NO+]. Dissociation to C6H5+ + NO products was measured over a range of internal energies and rate constants from 10(3) to 10(7) s(-1) and fitted with the statistical theory of unimolecular decay. A 0 K dissociative photoionization onset energy of 10.607 +/- 0.020 eV was derived by using the simplified statistical adiabatic channel model. The thermochemical network of Active Thermochemical Tables (ATcT) was expanded to include phenyl and phenylium, as well as nitrosobenzene. The current ATcT heats of formation of these three species at 0 K (298.15 K) are 350.6 (337.3) +/- 0.6, 1148.7 (1136.8) +/- 1.0, and 215.6 (198.6) +/- 1.5 kJ mol(-1), respectively. The resulting adiabatic ionization energy of phenyl is 8.272 +/- 0.010 eV. The new ATcT thermochemistry for phenyl entails a 0 K (298.15 K) C-H bond dissociation enthalpy of benzene of 465.9 (472.1) +/- 0.6 kJ mol(-1). Several related thermochemical quantities from ATcT, including the current enthalpies of formation of benzene, monohalobenzenes, and their ions, as well as interim ATcT values for the constituent atoms, are also given.