It has been recently determined that heterogeneous hydrogenation catalysts such as platinum can be made enantioselective by the use of molecular modifiers. For instance, alpha-ketoesters such as ethyl pyruvate can be selectively hydrogenated by cinchona-modified platinum catalysts to produce the corresponding optically-pure (R)- or (S)-alpha-hydroxoesters (ethyl lactates from the pyruvate). In these, the adsorption geometry of the modifier appears to be critical to the performance of the catalyst. Here we report on infrared studies on the characterization of the adsorption of those modifiers from the liquid phase onto platinum surfaces. A number of cinchona molecules were probed, and the effects of concentration and solvent on the adsorption were investigated.