Understanding the Surface Chemistry of Enantioselective Heterogeneous Reactions: Influence of Modification Variables on the Interaction of Methylacetoacetate with (S)-Aspartic Acid Modified Ni{111}

Abstract

It has long been established that the adsorption of α-amino acids onto Ni surfaces results in the formation of catalysts capable of the enantioselective hydrogenation of β-ketoesters. Reflection absorption infrared spectroscopy (RAIRS) has been employed to investigate the chiral modification of Ni{111} surfaces by (S)-aspartic acid as functions of modification temperature and pH. Correlations are drawn between the coverage and molecular conformation of aspartic acid on the modified model catalysts and the effectiveness of chirally modified Ni catalysts prepared under analogous conditions. In addition, we investigated the interaction of the simplest β-ketoester, methylacetoacetate, with chirally modified surfaces and identified how the tautomeric form of methylacetoacetate is strongly influenced by both modification pH and temperature. We discuss the implications of our findings for understanding the enantioselective behavior of aspartic acid-modified Ni surfaces.