The use of the catalyst [Formula: see text] in the reduction of the ethylenic system of styryl ketones by 1-phenylethanol permits the hydrogenation reaction to proceed at 50 °C. Some substituent effects in the α,β-unsaturated ketones were demonstrated at this temperature. These showed an increase in the initial rate of reduction for electron-attracting groups and the inverse effect for electron-donating groups. The observation of a relation between the electrochemical reduction potential of these ketones and their rate of hydrogenation suggests a transfer of hydrogen to the ketone by a hydride ion intermediate. [Journal translation]