Electronic and steric effects in the hydrogenation of alkyl aryl ketones on palladium

The hydrogenation of some forty aromatic ketones to the corresponding alcohols has been studied in ethanol using carbon-supported palladium as the catalyst. Zero order kinetics with respect to ketone is observed. For acetophenones electronic substituent effects may be expressed in terms of a Hammett-Yukawa relationship with ρ = 0.7. 2-Alkylacetophenones react very slowly. With alkyl phenyl ketones increase of size of the alkyl group causes increasing rate of hydrogenation. The adsorbed state is discussed on the basis of competition experiments.

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