FT-IRAS OF ADSORBED ALKOXIDES - ETHOXIDES ON CU(111)

The Fourier-transform infrared reflection absorption spectra (FT-IRAS) are presented for a set of deuterium-labelled ethoxides on Cu(111). S table ethoxides are formed by deprotonation of the corresponding ethan ols on the preoxidized Cu(111) surface. Comparison of the ethoxide vib rational spectra with those of gas phase ethanols and multilayer ethan ols on Cu(111) allowed a detailed assignment of the ethoxide spectra. The surface selection rules for IRAS were used to determine the averag e orientation of the adsorbed ethoxide. Comparing the spectra of ethox ide and the deuterated ethoxides in the CD and CH stretch regions show s the presence of a weak asymmetric methylene group stretch (nu(a)(CH2 )) and a loss in intensity of the symmetric methyl group stretch (nu(s )(CH3)) with respect to the same mode in the multilayer. These FT-IRAS results indicate that ethoxide has the C-3v axis of the methyl group, and hence the C-C bond, oriented roughly parallel with the surface, a nd the plane of the molecule, defined by the CCO atoms, tilted away fr om the surface normal.