Investigating the mechanism of chiral surface reactions: the interaction of methylacetoacetate with (S)-glutamic Acid modified Ni{111}.
Investigating the mechanism of chiral surface reactions: the interaction of methylacetoacetate with (S)-glutamic Acid modified Ni{111}.
复制标题
研究手性表面反应的机理：乙酰乙酸甲酯与 (S)-谷氨酸修饰的 Ni{111} 的相互作用。
作者：
Jones Te;C. Baddeley
β-酮酯在镍基催化剂上的对映选择性加氢反应是一种罕见的多相催化手性反应。催化剂制备的关键步骤是从溶液中吸附手性分子(修饰剂)。一种特别有趣的修饰剂是(S)-谷氨酸，因为催化反应中的主要对映体产物取决于修饰温度。报道了用反射吸收红外光谱研究了乙酰乙酸甲酯(最简单的β-酮酯)在(S)-谷氨酸修饰的镍表面上的吸附随改性剂覆盖度和修饰温度的变化。我们发现乙酰乙酸甲酯在饱和的(S)-谷氨酸覆盖的表面上的粘附率接近于0。在较低的改性剂覆盖率下，可以发生对乙酰乙酸甲酯的吸附。在300K时，乙酰乙酸甲酯在经谷氨酸修饰的镍表面上以二酮互变形式存在，观察到S谷氨酸与乙酰乙酸甲酯之间存在1：1的相互作用。相反，350K时，乙酰乙酸甲酯在经(S)-谷氨酸修饰的镍表面上的吸附完全是以烯醇互变异构体的形式发生的。讨论了多相催化反应的意义。
The enantioselective hydrogenation of beta ketoesters over Ni-based catalysts is a rare example of a heterogeneously catalyzed chiral reaction. The key step in catalyst preparation is the adsorption from solution of chiral molecules (modifiers). One particularly interesting modifier is (S)-glutamic acid because the dominant enantiomeric product in the catalytic reaction depends upon the modification temperature. We report a reflection absorption infrared spectroscopy (RAIRS) study of the adsorption of methylacetoacetate (the simplest beta ketoester) onto (S)-glutamic acid modified Ni{111} surfaces as functions of the modifier coverage and modification temperature. We show that the sticking probability of methylacetoacetate is close to 0 on saturated (S)-glutamic acid covered surfaces. At lower modifier coverage, methylacetoacetate adsorption can occur. Adsorption of methylacetoacetate onto a Ni{111} surface modified by (S)-glutamic acid at 300 K results in the diketo tautomeric form, with evidence being observed for a 1:1 interaction between zwitterionic (S)-glutamate and methylacetoacetate. In contrast, adsorption of methylacetoacetate onto a Ni{111} surface modified by (S)-glutamic acid at 350 K occurs exclusively in the enol tautomeric form. The implications for the heterogeneous catalytic reaction are discussed.