Investigation of the surface chemistry of crown ethers: the adsorption and reaction of 1,4-dioxane on palladium(111)

1,4-Dioxane adsorbs on Pd(lll) at 80K to form an overlayer saturating at an exposure of similar to 4L (1 L = 1 x 10(-6) Torr s) and desorbs with a peak centered at similar to 268 K in temperature-programmed desorption. Multilayer growth commences for exposures >2 L suggesting that they form before the monolayer is completed. The multilayers desorb at similar to 160 K. Reflection-absorption infrared spectroscopy of both normal and perdeuterated dioxane suggests that it converts from its usual chair conformation in the gas phase into a boat conformation in the monolayer, allowing the lone pairs on both oxygen atoms to interact with the surface. A portion of the adsorbed dioxane thermally decomposes at or below similar to 300 K to desorb ethylene and hydrogen and to deposit CO onto the surface. The adsorbed CO thermally desorbs at similar to 460 K. (C) 2000 Elsevier Science B.V. All rights reserved.