The orientation of cinchonidine (CD) adsorbed on a Pt surface, a model system of enantioselective catalysis for hydrogenation reactions, is studied in 1,2-dichloroethane by in situ surface-enhanced infrared absorption spectroscopy in attenuated total reflection configuration. The quinoline (QN) moiety of CD is shown to be reoriented from a pi-bonded nearly parallel orientation to an N-bonded upright one by bubbling the solution with H-2. The origin of the reorientation is ascribed to the repulsive interaction of a QN pi-orbital and the negative surface charge induced by dissociative adsorption of H-2 and hydrogenation of the vinyl moiety.