C−C bond scission steps are often considered rate-determining in ethane hydrogenolysis. This paper is devoted to the calculations of the activation energies of these steps using the unity bond index−quadratic exponential potential method, formerly known as the bond-order conservation−Morse potential method. Binding energies of atomic carbon with groups VIII and IB metals Ni(111), Pd(111), Pt(111), Rh(111), Ru(0001), Ir(111), Fe(110), Cu(111), and Au(111) are estimated from experimental data on the chemisorption of various species on these surfaces. The resulting estimates are corrected taking into account DFT data on CH x binding energies. The strengths of carbon binding to the surfaces allow arranging the metals into the following series:  Cu(111) < Au(111) < Pd(111) < Ru(0001) < Pt(111) ≈ Ni(111) < Rh(111) < Ir(111) < Fe(110). The values of carbon binding energies range from 122.9 kcal/mol for Cu(111) to 192.5 kcal/mol for Fe(110). The activities of these surfaces toward C−C bond scission increase in the same series.

Recent research has led to the development of interactive computer programs that enable a comprehensive search for reaction mechanisms. These programs enable a new strategy of interactive mechanistic study which borrows heavily from the century-old method of multiple working hypotheses proposed by T. C. Chamberlin. We propose that mechanistic studies should follow the method of considering at the outset a complete set of plausible mechanisms, rather than just one or a small number, which has the drawbacks described well by Chamberlin. This general methodology has become much more practical with the development of interactive computer programs that search comprehensively while building on the experimenter's prior knowledge. This paper illustrates the methods in detail, using as a vehicle the hydrogenation of ethylene, which is among the most studied reactions in the history of heterogeneous catalysis.