Bond Dissociation Enthalpies of Large Aromatic Carbon-Centered Radicals

Carbon−hydrogen bond dissociation enthalpy (BDE) values are computed for the class of benzylic radicals. An extended and representative set of large methylated polyaromatics has been submitted to an accurate computational study using various levels of theory. The hybrid B3P86 as well as two contemporary functionals (BMK and M05-2X) are applied. For a selection of species, the suitability of the DFT methods is validated through comparison with high-level G3(MP2)-RAD and SCS-ROMP2 results. The influence of the polyaromatic environment on the BDE results is thoroughly discussed. The results are compared with other hydrocarbon radical types in order to obtain a generalized radical stability scale. In order to complete this investigation, also carbon−carbon BDE values have been calculated, giving information about the influence of the local environment on removing the methyl group from the polyaromatic.