FLUORINATED ALCOHOLS ON CLEAN AND PREOXIDIZED AG(110) SURFACES - HREELS AND TDS STUDIES

The surface chemistry of fluorinated alcohols (CF3(CF2)nCH2OH) adsorbed on clean and preoxidized Ag(110) surfaces has been studied by high-resolution electron energy loss spectroscopy (HREELS) and desorption measurements. The surface chemistry of these species is similar to that of the straight-chain alcohols in that on the clean Ag(110) surface they adsorb reversibly while on the oxidized surface they deprotonate to form a fluorinated alkoxide. The vibrational spectra indicate that the molecularly adsorbed species are oriented with their fluorinated chains interacting with the surface. The alkoxide formed by the deprotonation of 2,2,2-trifluoroethanol is oriented with its C-C bond close to the surface normal. The spectra of the longer chain fluorinated alcohols and alkoxides are almost identical, and it appears that the fluorinated chains lie roughly parallel to the surface. As in the cases of the hydrocarbon alkoxides, the fluorinated alkoxides decompose by beta-hydride elimination to generate the aldehyde. The fluorinated alkoxides are, however, much more stable than their hydrocarbon analogues, decomposing at 420 K as opposed to 270 K on the Ag(110) surface.