1Department of Chemistry, University of Mashhad, P.O. Box 91735-654 Mashhad, I.R. IRAN
2Department of Chemistry Education, Seoul National University, Seoul 151-742, and Center for Molecular Science, 373-1 Kusungdong, Taejon 305-710, KOREA
3Department of Chemistry and Ontario Laser and Lightwave Research Center, University of Toronto, Toronto, M5S 1A1, CANADA
The surface-enhanced Raman scattering (SERS) spectra of maleic (cis; 2-butaneoic acid) and fumaric (trans; 2-butaneoic acid) acids adsorbed on aqueous silver sol particles are reported. These two acids form two groups of isomers which differ only in the relative positions of the two carboxylate groups. The photochemistry of maleic and fumaric acids adsorbed on the surface of silver colloids is investigated using SERS as a probe. The photochemical studies of these two acids adsorbed on colloidal silver surfaces show that the photoisomerization of maleic to fumaric acid has occurred. We interpret our spectra as indicating that fumaric acid p bounds through a C=C double bond, while maleic acid s bonds through lone pairs on the carboxylate groups.