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(111) at 80 K to form an overlayer saturating at an exposure of ∼4 L (1 L=1×10−6 Torr s) and desorbs with a peak centered at ∼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 ∼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 ∼300 K to desorb ethylene and hydrogen and to deposit CO onto the surface. The adsorbed CO thermally desorbs at ∼460 K.