We systematically calibrated a three-level hybrid quantum mechanical ONIOM method that is suitable for the accurate and efficient calculation of bond dissociation energies (BDE's) of phenyl-substituted hydrocarbons. We applied the combination ONIOM(G2MS(R):RMP2/6-31G(d):B3LYP/3-21G)//ONIOM(B3LYP/6-31G: B3LYP/3-21G) to the BDE calculation of hexaphenylethane (HPE). We predict that the BDE of HPE (including the temperature correction) is 16.6 kcal/mol, indicating that synthesis of HPE may be feasible, despite all attempts so far having been unsuccessful.