ANHYDRIDE RING CHEMISTRY AT A METAL-SURFACE

The adsorption of phthalic anhydride on clean and oxygen predosed Cu{1 10} surfaces has been studied by Fourier transform infrared spectrosco py in the temperature range 95-300 K. Further characterization of the adsorbed species and its thermal stability on these surfaces has been obtained from thermal desorption measurements. A variety of species ar e produced on the clean surface including the parent molecule, one in which the anhydride ring has been cleaved and one following the loss o f a CO unit which is the stable form at room temperature. In the prese nce of oxygen, CO loss is prevented and, instead, a phthalate species is formed. Infrared spectroscopy is ideally suited to identify these s pecies and their orientation, which varies both with coverage and temp erature in a complex manner. Thermal breakdown of the molecule occurs above 530 K on the clean surface to produce a variety of gas-phase pro ducts including benzene. The breakdown occurs at a somewhat higher tem perature (585 K) in the case of the oxygen-predosed surface and leads to an explosive release of the products into the gas phase.