Stepwise or concerted addition of 1,3-butadiene to oxygen adsorbed on the silver (110) surface?

Abstract

The interaction of 1,3-butadiene with atomically adsorbed oxygen on a A g ( l l 0 ) surface is studied. Three different approaches of 1,3-butadiene to a n 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-cycloaddition, a n interaction with the terminal carbon, and a n interaction with the internal carbon of the 1,3-butadiene. Extended Hiickel tight-binding calculations show that the interaction of one of the terminal carbons of 1,3-butadiene with the surface oxygen is favored. This intermediate shows a preference for a 1,4 ring closure reaction rather than a 1,2 ring closure reaction, leading to 2,5-dihydrofurane instead of vinyl epoxide. The interaction between the suggested intermediates and the Ag( 1 10) surface as well as the bonding of different adsorbed products are analyzed and discussed in relation to the experimental results.

Adsorption of 1,3-butadiene on supported and promoted silver catalysts

“…By employing surface-enhanced Raman spectroscopy and using ab initio molecular orbital frequency calculations, Itoh and co-workers showed that BD adsorption below 120 K on evaporated Ag films gave rise to one absorption feature in the C=C-stretching region at 1636 cm −1 , which was ascribed to BD adsorbed via one of the C=C bonds coordinated to a positively charged Ag site, whereas at 180 K this band shifted to 1631-1625 cm −1 and another band at 1606 cm −1 formed, which was associated with BD coordinated through both C=C bonds at positively charged sites [18][19][20]. Using extended Hückel theory, Schiøtt and Jør-gensen probed the interaction between BD and atomically adsorbed oxygen on Ag (110) and reported that the interaction of only one of the terminal carbons of BD with surface oxygen was favored [22]. Their calculations indicated that when BD adsorbs on oxygen-covered Ag, the intermediate loses a considerable amount of its double-bond character and the C 2 -C 3 overlap population increases, indicating this latter band increases its double-bond characteristics.…”

“…As noted earlier, Schiøtt and Jørgensen used extended Hückel tight-binding calculations to show that the BD intermediate on Ag (110) binds through one of its C=C bonds and reacts with an oxygen atom to preferentially form 2,5-dihydrofuran rather than EpB [22]. Monnier has reported that the reaction between BD and atomic oxygen produces EpB on CsCl-promoted Ag/α-Al 2 O 3 and the formation of 2,5-dihydrofuran proceeds by the isomerization of EpB [5,9].…”

“…Itoh and co-workers showed with both surface-enhanced Raman scattering spectroscopy (SERS) and ab initio molecular orbital calculations that, depending on the temperature, BD may adsorb on positively charged Ag atoms via either a single C=C bond (at 120 K) or both C=C bonds (at 180 K) [18][19][20]. Madix and co-workers [21] and Schiøtt and Jørgensen [22] studied the reaction of BD with oxygen atoms on Ag (110) using TPD and extended Hückel tight-binding calculations, and they showed that 1,4 addition to give 2,5-dihydrofuran was favored. On the other hand, Monnier and co-workers showed that when BD is adsorbed on dispersed, oxygencovered Ag crystallites, EpB is formed with high selectivity due to 1,2 addition [5,9,[23][24][25].…”