The reaction of 1-chloro-2-methyl-2-propanol on oxygen-covered Ag(1 1 0): epoxide formation via a surface chlorohydrin reaction

Temperature programmed desorption and X-ray photoelectron spectroscopy have been used to study the reactions of 1-chloro-2-methyl-2-propanol (CltBuOH) on clean and oxygen-covered Ag(1 1 0) surfaces. CltBuOH reacts on the oxygen-covered surface to produce chloro-tert-butoxy (CltBuO(a)) intermediates and water. CltBuO(a) subsequently reacts to produce isobutylene oxide (IBO) and surface chlorine. Small amounts of methyl ethyl ketone were also detected in some coverage regimes. Multiple desorption channels for CltBuOH and IBO were observed; the relative importance of each channel depends on surface coverage. These studies suggest that formation of the IBO product proceeds either through an oxametallacycle intermediate that is not stable under the reaction conditions, or via a concerted process analogous to the olefin chlorohydrin synthesis of epoxides. Theoretical models for oxametallacycle ring closure are presented, and the implications of these studies for the silver-catalyzed epoxidation of olefins are discussed.