Mechanism of hydrogenolysis. II. a molecular orbitals study of hydrogenolysis of toluene

In hydrogenolysis of toluene to produce benzene and methane, atomic cracking process H+ C6H5CH3 -> C6H6CH3 (a) or H+C6H5CH3 -> C6H5+CH4 (b) has been presumed as rate controlling in chain propagation step of the radical chain mechanism. These two alternative processes are compared on the energetics calculated by the extended Huckel M.O. method. The reaction (a), an addition of the attacking hydrogen atom to phenyl carbon atom adjacent to methyl group followed by an elimination of methyI radical in a concerted manner, is found to be the most likely pathway.