Mechanism of β-hydrogen abstraction from adsorbed alkoxides on supported metal oxide catalysts

The transition state and the mechanism of beta-hydrogen abstraction from alkoxides adsorbed on vanadia monolayers supported on both ceria and anatase titania were investigated using a combination of temperature programmed desorption (TPD) and microcalorimetry. The TPD studies demonstrated that the peak temperature for beta-hydrogen abstraction from adsorbed ethoxides to produce acetaldehyde increased as the methyl group in the ethoxide was fluorinated. The calorimetry results showed that methyl group fluorination did not affect the heat of dissociative adsorption of the ethanol reactant. These observations are consistent with a transition state in which there is a positive charge on thebeta-carbon in the ethoxide and indicates that the reaction proceeds via hydride transfer to a vanadium site.