Mechanistic Study of Glucose-to-Fructose Isomerization in Water Catalyzed by [Al(OH)2(aq)]+

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• 作者：Jinqiang Tang ; Xiawei Guo ; Liangfang Zhu ; Changwei Hu
• 刊名：ACS Catalysis
• 出版年：2015
• 出版时间：September 4, 2015
• 年：2015
• 卷：5
• 期：9
• 页码：5097-5103
• 全文大小：485K
• ISSN：2155-5435

文摘

The nature of the active aluminum species and their interaction with glucose in water are studied to establish a detailed mechanism for understanding AlCl₃-catalyzed glucose-to-fructose isomerization. The combination of activity results with electrospray ionization tandem mass spectrometry (ESI-MS/MS) reveal that [Al(OH)₂(aq)]⁺ species contribute a lot to the isomerization. Attenuated total reflection infrared spectroscopy (ATR-IR) results show that glucose undergoes a ring-opening process which is accelerated by the [Al(OH)₂(aq)]⁺ species. The binding of acyclic glucose with [Al(OH)₂(aq)]⁺ species occurs at the C1鈥揙 and C2鈥揙 positions of glucose, which initiates the hydride shift of the aldose-to-ketose isomerization. The in situ ²⁷Al NMR data elucidate the maintenance of the hexa-coordinated form of Al species throughout the reaction. An obvious kinetic isotope effect occurs with the C2 deuterium-labeled glucose, confirming that the intramolecular hydride shift from the C2 to C1 positions of glucose is the rate-limiting step for the isomerization. The apparent activation energy (E_a) of the AlCl₃-catalyzed glucose-to-fructose isomerization reaction is estimated to be 110 卤 2 kJ路mol^鈥?.