Determination of enthalpies of formation of organic free radicals from bond dissociation energies - 1. Hydrocarbon radicals

The enthalpies of formation (Delta Hf degrees) for 24 hydrocarbon radicals (R-.), mainly polycyclic aromatic radicals with the complex structure, were determined from the published data on bond dissociation energies. The Delta Hf degrees values of the corresponding molecules were calculated, in the majority of cases, by the macroincrement method. Calculations by the group contribution method were performed. Some Delta H(f)degrees(R-.) values were compared to those calculated by the additive-group method. Calculations were performed, and the conjugation energies of the radicals were discussed. The errors of determination of the Delta H(f)degrees(R-.) values found were estimated. Due to this work, the database for Delta H(f)degrees values of hydrocarbon radicals was increased more than by 25%.