An investigation of the surface chemistry of methyl pyruvate on Cu(1 1 1)

The surface chemistry of an α-ketoester, methyl pyruvate, has been studied on a model Cu(1 1 1) single crystal surface. Monolayers of methyl pyruvate at 180 K consist predominately (ca. 66%) of a chemisorbed methyl pyruvate moiety, with its keto-carbonyl bonded to the surface in a η2 configuration, this moiety desorbs intact at 365 K. The rest of the monolayer contains weakly adsorbed methyl pyruvate, which desorbs at 234 K, which interacts with the surface through the lone pair electrons of the oxygen atoms of the CO groups, adopting a η1 configuration. Previous studies of simple ketones on model noble metal surfaces have only observed weakly bonded η1 configurations. The observation of a strongly chemisorbed moiety in the present study is attributed to the activation of the keto-carbonyl by the electron withdrawing ester group. This behaviour is consistent with the homogeneous inorganic chemistry of ketones. Given both the formation of a η2 bonded methyl pyruvate moiety on Cu(1 1 1) and the known activity of Cu as a selective hydrogenation catalyst, it is suggested that it maybe worthwhile considering the possibility of testing the effectiveness of chirally modified supported Cu as an enantioselective catalyst.