Theoretical Study for Pyridinium-Based Ionic Liquid 1-Ethylpyridinium Trifluoroacetate: Synthesis Mechanism, Electronic Structure, and Catalytic Reactivity

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• 作者：Xueying Zhu ; Peng Cui ; Dongju Zhang ; Chengbu Liu
• 刊名：Journal of Physical Chemistry A
• 出版年：2011
• 出版时间：July 28, 2011
• 年：2011
• 卷：115
• 期：29
• 页码：8255-8263
• 全文大小：1030K
• 年卷期：v.115,no.29(July 28, 2011)
• ISSN：1520-5215

文摘

By performing density functional theory calculations, we have studied the synthesis mechanism, electronic structure, and catalytic reactivity of a pyridinium-based ionic liquid, 1-ethylpyridinium trifluoroacetate ([epy]⁺[CF₃COO]^{鈭?/sup>). It is found that the synthesis of the pyridinium salt follows a S_N2 mechanism. The electronic structural analyses show that multiple H bonds are generally involved in the pyridinium-based ionic liquid, which may play a decisive role for stabilizing the ionic liquid. The cation鈥揳nion interaction mainly involves electron transfer between the lone pair of the oxygen atom in the anion and the antibonding orbital of the C*鈥揌 bond (C* denotes the carbon atom at the ortho-position of nitrogen atom in the cation). This present work has also given clearly the catalytic mechanism of [epy]+[CF₃COO]鈭?/sup> toward to the Diels鈥揂lder (D-A) reaction of acrylonitrile with 2-methyl-1,3-butadiene. Both the cation and anion are shown to play important roles in promoting the D-A reaction. The cation [epy]+, as a Lewis acid, associates the C鈮 group by C鈮路路路H H bond to increase the polarity of the C鈺怌 double bond in acrylonitrile, while the anion CF₃COO鈥?/sup> links with the methyl group in 2-methyl-1,3-butadiene by C鈥揌路路路O H bond, which weakens the electron-donating capability of methyl and thereby lowers the energy barrier of the D-A reaction. The present results are expected to provide valuable information for the design and application of pyridinium-based ionic liquids.}