Stereochemical Studies of the Electrolytic Reactions of Organic Compounds. Part 18. Comparative Study of Hydrogenation on Metal-black Cathodes and Catalysts

Stereoselective hydrogenation on metal-black cathodes and catalysts, which were prepared by electrode-position under the same conditions, was comparatively investigated. Stereoisomeric ratios of alcohols formed from the ketones on the Pd- and Pt-black cathodes seemed to be almost equal to those on the corresponding metal-black catalysts, while the yields were quite different between the cathodic and catalytic hydrogenations. On the other hand, results of the hydrogenation of the acetylenes on the cathodes were also different, in not only the yield but also the isomeric ratio, from those on the catalysts. In addition to stereoselectivity, relative hydrogenation rates between cis- and trans-olefins were compared in both the cathodic and catalytic hydrogenations. It was also found that a mercury pool cathode gave quite different stereochemical results in the hydrogenation of the unsaturated compounds from those obtained with either the metal-black cathodes or the catalysts.