CHEMISTRY OF CHLOROETHYLENES ON CU(100) - BONDING AND REACTIONS

The bonding and reactions of chloroethylenes (vinyl chloride, trans- a nd cis-dichloroethylene, trichloroethylene) on a Cu(100) surface have been investigated by temperature-programmed desorption and reaction, n ear-edge X-rap absorption fine structure (NEXAFS) studies and measurem ents of changes of the surface work function. The monolayer molecules adsorb molecularly intact at 95 K via pi coordination. The molecules o rient with their molecular planes parallel to the surface with little increase (<0.02 Angstrom) in the C-C bond distance compared with the g as phase values. The degree of thermal dissociation increases with the extent of halogenation, and no chlorine is present in the hydrocarbon reaction products liberated from the surface. Both cis- and trans-1,2 -chloroethylene produce acetylene and a small amount of benzene, while dissociation of trichloroethylene generates acetylene and deposits a carbon residue on the surface. Vinyl chloride desorbs from Cu(100) wit hout reaction. (C) 1997 Elsevier Science B.V.