Abstract
The stereoselective hydrogenation of three xylene isomers to yield cis- and trans-dimethylcyclohexane has been investigated on eight kinds of transition metal catalysts by the gas chromatographic pulse technique. The selectivity for the formation of trans-dimethylcyclohexane was found to be of the following sequence with respect to the hydrogenation of o-, m- and p-xylene. [chemicalformula] It was pointed out that the selectivity sequence parallels with the ability of the transition metals to form π-allylic complexes in the case of the hydrogenation of o- and p-xylene and that the remarkable suppression of transformation, as found in the case of m-xylene, is due to the steric hindrance rather than the poor ability of the transition metals to form an adsorbed π-allylic adsorbed intermediate on the surface.
