From Catalysis in Application

Rajinder Mann [1] , Graham J. Hutchings [2] , Werner van Rensburg [3] and David J. Willock [4].

1 INTRODUCTION

The hydrogenation of ketones over metal surfaces is an important step in many applications in heterogeneous catalysis, such as the production of unsaturated alcohols from ?- ? unsaturated ketones. Another important example is the enantioselective hydrogenation of pyruvate esters to lactates over modified supported Pt and Pd catalysts which has been widely studied due to the high e.e.s that can be achieved1. In the molecular level models of these reactions it has been assumed that the pyruvate ester adsorbs in a ?-bonded mode with the molecular plane parallel to the surface2 ,3 ,4. Recently, however, XPS and UPS results have suggested that the adsoiption of ethyl pyruvate on Pt(111) involves the interaction of the keto oxygen atom with the surface. This would suggest that the molecular plane is not parallel to the surface and so will have important implications in mechanistic models of the reaction. The lone pair bonding mode has also been observed for simpler ketones such as acetone. Some time ago Avery, using a combination of EELS and temperature programmed desorption experiments, suggested that at high coverage acetone adsorbs on Pt(111) through the lone pair of the oxygen taking up an "endon" orientation [ ? 1(O)-acetone] with the C=O bond toward the surface5. At low coverage a more strongly adsorbed species with a lower C=O stretch frequency was observed...

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