info:eu-repo/semantics/article
Probing elementary steps under reaction conditions using infrared spectroscopy
Autor
Stacchiola, Dario
Calaza, Florencia
Burkholder, Luke
Schwabacher, Alan
Neurock, Matthew
Tysoe, Wilfred
Institución
Resumen
The reaction pathway for the palladium-catalyzed synthesis of vinyl acetate from acetic acid, ethylene and oxygen is investigated using reflection-absorption infrared spectroscopy by monitoring the rate of acetate titration by gas-phase ethylene. This reveals that acetate species are removed by reaction with gas-phase ethylene resulting in vinyl acetate formation. Reaction with C2D4 reveals a large (ï ¾6) isotope effect indicating that hydrogen is involved in the rate-limiting step. This also results in the appearance of an infrared feature that is assigned to an acetoxyethyl- palladium intermediate. Acetate reaction rates are different for the isotopomers, CH2CD2 and CHDCHD. These observations are consistent with a reaction pathway first proposed by Samanos in which ethylene reacts with an acetate species to form an acetoxyethyl-palladium intermediate, which then reacts to form vinyl acetate by a ï ¢-hydride elimination reaction.