Despite these limitations, one can assume that the underlying principle of matching electronegativities for good catalysts might also affect the principles of electrocatalysis 66 . Hence, the consideration of voltage changes may affect the ground state energies of electrode materials which also change the resulting electronegativies. Further studies are needed to compare the resulting electronegativities of the materials with the corresponding values of the product and reactant species. We hope this approach enhances the understanding of the underlying mechanisms of the Sabatier principle. As can be seen in Table , the corresponding products and methyl eugenol differ only slightly in their electronegativities. Larger differences can be mainly seen for the chemical hardnesses. In general, all molecules are rather Lewis basic components with high polarizabilities. The results for the catalysts in Table show that the species are represented by rather Lewis basic catalysts (ferrocene) as well as rather Lewis acidic compounds such as FeCl 2 . In addition, also the chemical hardnesses differ widely with ferrocene and FeCl 2 as the most significant examples.