Theoretical Elucidation of the Mechanism and Kinetic Experimental Phenomena on the Esterification of α-Tocopherol with Succinic Anhydride: Catalysis of a Histidine Derivative vs an Imidazolium-Based Ionic Liquid,The Journal of Organic Chemistry

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Theoretical Elucidation of the Mechanism and Kinetic Experimental Phenomena on the Esterification of α-Tocopherol with Succinic Anhydride: Catalysis of a Histidine Derivative vs an Imidazolium-Based Ionic Liquid
The Journal of Organic Chemistry ( IF 3.3 ) Pub Date : 2017-11-10 00:00:00 , DOI: 10.1021/acs.joc.7b02102
Yaru Jing ₁ , Rongxiu Zhu ₁ , Chengbu Liu ₁ , Dongju Zhang ₁

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DFT calculations have been conducted to gain insight into the mechanism and kinetics of the esterification of α-tocopherol with succinic anhydride catalyzed by a histidine derivative or an imidazolium-based ionic liquid (IL). The two catalytic reactions involve an intrinsically consistent molecular mechanism: a rate-determining, concerted nucleophilic substitution followed by a facile proton-transfer process. The histidine derivative or the IL anion is shown to play a decisive role, acting as a Brönsted base by abstracting the hydroxyl proton of α-tocopherol to favor the nucleophilic substitution of the hydroxyl oxygen of α-tocopherol on succinic anhydride. The calculated free energy barriers of two reactions (15.8 kcal/mol for the histamine-catalyzed reaction and 22.9 kcal/mol for the IL-catalyzed reaction) together with their respective characteristic features, the catalytic reaction with a catalytic amount of histamine vs the catalytic reaction with an excessed amount of the IL, rationalize well the experimentally observed kinetics that the former has faster initial rate but longer reaction time while the latter is initiated slowly but completed in a much shorter time.

中文翻译：

琥珀酸酐使α-生育酚酯化的机理和动力学实验现象的理论解释：组氨酸衍生物与基于咪唑鎓的离子液体的催化作用

已经进行了DFT计算，以了解由组氨酸衍生物或咪唑基离子液体（IL）催化的α-生育酚与琥珀酸酐酯化的机理和动力学。这两个催化反应涉及一个内在一致的分子机制：确定速率，协调一致的亲核取代，然后进行简单的质子转移过程。组氨酸衍生物或IL阴离子显示出决定性的作用，通过提取α-生育酚的羟基质子以促进α-生育酚的羟基氧在琥珀酸酐上的亲核取代而充当布朗斯台德碱。计算出的两个反应的自由能垒（组胺催化的反应为15.8 kcal / mol，22为22。

更新日期：2017-11-11

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