Energetics of CC Bond Scission in Ethane Hydrogenolysis:
A Theoretical Study of Possible
Intermediates and Reaction Pathways

A. V. Zeigarnik * and O. N. Myatkovskaya **

* Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, Moscow, 119992 Russia

** All-Russia Research Institute of Chemical Technology, Moscow, 115230 Russia

Received February 22, 2000

Abstract—C–C bond scission steps, which are often considered as rate-determining in ethane hydrogenolysis,
are studied by the Unity Bond Index–Quadratic Exponential UBI–QEP method. The binding energies of atomic
carbon with Group VIII and IB metal surfaces Ni(111), Pd(111), Pt(111), Rh(111), Ru(001), Ir(111), Fe(110),
Cu(111), and Au(111) are estimated using experimental data on the adsorption of various species on these sur-
faces. These estimates are corrected using data from density functional theory (DFT) on the adsorption heats
of the CH_x species. Metal surfaces are arranged in the following series according to the binding strength of a
carbon atom: Cu(111) < Au(111) < Pd(111) < Ru(001) Pt(111) < Ni(111) Rh(111) < Ir(111) < Fe(110). The
values of chemisorption heats range from 121 kcal/mol for Au(111) to 193 kcal/mol for Fe(110). The activity
of these surfaces toward C–C bond scission increases in the same series. The results of this work suggest that
the most probable C–C bond scission precursors are ethyl, ethylidyne, adsorbed acetylene, CH₂CH, CH₂C, and
CHC. Theoretical data obtained by different methods are compared and found to agree well with each other. An
overview of experimental data on ethane hydrogenolysis mechanisms is given.

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