The selectivities and yields of various reactions (hydrogenolysis, isomerization, C5-cyclization, aromatization, olefin formation) of five hexane isomers are reported over palladium black and the dependence of these values on the hydrogen partial pressure was determined. The data are compared with those previously obtained for platinum black. General similarities can be observed with minor differences such as enhanced olefin formation and the similar rates of aromatization of n- and iso-hexanes. These are interpreted in terms of the marked ability of palladium to form π-complexes, as opposed to σ-type intermediates for hydrogenolysis. The "alternative" pathway of C6- and C5-cyclization is pointed out, the fate of the molecule being governed by the amount of hydrogen on the surface. 2,2-Dimethylbutane is not unreactive in skeletal rearrangement reactions to give either benzene or isomers; this finding, the opposite of most literature data, is explained by two types of bond shift isomerization mechanisms.
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