| Abstract
| - Adsorption and reaction of ethyl pyruvate (EtPy), a model reactant in chiral hydrogenation of α-ketoester onPt/γ-Al2O3 were studied by IR spectroscopy. In vacuum and Ar flow at room temperature, several side reactionsof EtPy are detected by IR spectroscopy: decomposition on Pt, aldol condensation, and hydrolysis on γ-Al2O3.When the quantity of adsorbed EtPy is small, CO formed from EtPy decomposition on Pt can react with thehydroxyl groups of Al2O3 to generate formate species. It is very interesting to find out that H2 not only actsas a reactant for the hydrogenation reaction but also plays an important role in suppressing the side reactionsof EtPy on Pt/γ-Al2O3 catalysts. The suppressing effect of H2 is not observed on γ-Al2O3 alone. The functionof spilt-over H atoms in suppressing these side reactions was confirmed and discussed. Adsorbed cinchonidine(CD) alone cannot suppress the condensation and hydrolysis of EtPy on γ-Al2O3, but the decomposition ofEtPy on Pt can be suppressed by absorbed CD. The coexistence of CD and H2 thoroughly inhibits all of theseside reactions of EtPy on Pt/γ-Al2O3. Adsorbed CD can help hydrogen to avoid site-blocking with side-reaction products then facilitate hydrogenation on Pt, which may be a reason for the rate acceleration effectof the adsorbed CD.
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