Surface-enhanced Raman spectroscopy has been utilized to probe the adsorption of the chiral modifier cinchonidine on polycrystalline platinum. Surfaces were prepared by electrodeposition of ultrathin platinum films onto roughened gold, which provided stable and intense SERS activity for performing these studies. The vibrational properties of adsorbed cinchonidine on platinum in ethanol solutions at 25 degreesC have been probed in situ. Based on the appearance and trends in the strong ring breathing mode at 1357cm(-1), the modifier is strongly and irreversibly adsorbed through the quinoline portion of cinchonidine by pi-bonding with the pi surface. Furthermore, analysis of both in-plane and out-of-plane vibrations suggests that the aromatic group of cinchonidine is tilted with respect to the surface. The degree of tilt appears to increase as concentration increases over the range of cinchonidine liquid-phase concentrations examined here (0.03-1.2 mM). The presence of an H-abstracted alpha-quinolyl species is also tentatively suggested by the appearance of a downshifted aromatic C=C stretching band not associated with adsorbed cinchonidine. These findings are largely consistent with what has been observed previously for cinchonidine adsorption on Pt from different solvents using in situ infrared spectroscopy. Addition of hydrogen into the system results in enhanced Raman scattering from adsorbed cinchonidine. Comparisons with SERS measurements of 10, 11-dihydrocinchonidine adsorption in ethanol suggest that the H-induced changes likely result from hydrogenation of the vinyl group on cinchonidine. The data suggest a more flat orientation of this species, resulting from increased interaction of the aromatic ring structure with the surface. The results are consistent with kinetic studies of cinchonidine hydrogenation, which have implied much stronger adsorption of 10, 11-dihydrocinchoni dine as compared with cinchonidine. (C) 2003 Elsevier B.V. All rights reserved.