STEPWISE OR CONCERTED ADDITION OF 1,3-BUTADIENE TO OXYGEN ADSORBED ONTHE AG(110) SURFACE

The interaction of 1,3-butadiene with atomically adsorbed oxygen on a Ag(110) surface is studied, Three different approaches of 1,3-butadien e to an oxygen atom that is adsorbed in the two-fold bridging site of the grooves on the Ag(110) surface are studied: a cheletropic 1,4-cycl oaddition, an interaction with the terminal carbon, and an interaction with the internal carbon of the 1,3-butadiene. Extended Huckel tight- binding calculations show that the interaction of one of the terminal carbons of 1,3-butadiene with the surface oxygen is favored. This inte rmediate shows a preference for a 1,4 ring closure reaction rather tha n a 1,2 ring closure reaction, leading to 2,5-dihydrofurane instead of vinyl epoxide. The interaction between the suggested intermediates an d the Ag(110) surface as well as the bonding of different adsorbed pro ducts are analyzed and discussed in relation to the experimental resul ts.