Competing epoxidation and allylic hydrogen abstraction in heterogeneous oxidation of olefins: Trans-β-methylstyrene oxidation on Au(111)

PETR 34

Xiaoying Liu, liu15@fas.harvard.edu and C. M. Friend, friend@chemistry.harvard.edu. Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford St., Cambridge, MA 02138
The reaction of trans-β-methylstyrene, an analog to propene, with chemisorbed oxygen on the Au(111) single-crystal surface has been investigated under ultra-high vacuum conditions in order to elucidate the role of the competition between addition to the C=C bond and allylic hydrogen activation in determining olefin epoxidation selectivities. Partial oxidation products—epoxide, benzoic acid, and cinnamic acid—are observed along with carbonaceous deposits and combustion products, CO2 and water, by temperature-programmed reaction. Cinnamic acid is formed by nucleophilic attack of oxygen on the terminal carbon in combination with allylic hydrogen removal. Our results provide direct evidence that both addition of adsorbed O to the C=C bond to form epoxide and allylic hydrogen abstraction are facilitated by the Au(111) surface.
 

Mechanism in Homogeneous and Heterogeneous Catalytic Epoxidation
8:00 AM-12:00 PM, Monday, August 20, 2007 Boston Park Plaza -- Whittier Rm, Oral

Division of Petroleum Chemistry

The 234th ACS National Meeting, Boston, MA, August 19-23, 2007