离子液体酸性强度探针  

The probes of acidic strength in ionic liquids

作　　者：周瑜[1] 邓耿[1] 郑燕珍[1] 孙海源 徐静[1] 尉志武[1] 

机构地区：[1]清华大学化学系,生命有机磷化学及化学生物学教育部重点实验室,北京100084

出　　处：《科学通报》2015年第26期2476-2481,共6页Chinese Science Bulletin

基　　金：国家自然科学基金(21133009)资助

摘　　要：离子液体作为绿色溶剂和催化剂在有机合成和催化反应中具有重要作用.酸性离子液体因同时拥有液体酸高密度的反应活性位和固体酸的不挥发性,近年来受到了广泛的关注.离子液体的酸性强度会影响化学反应的活性和作用位点的选择,测定离子液体的酸性强度对于认识酸催化反应机理、寻找合适的催化剂具有十分重要的指导意义.使用探针分子的分子光谱研究离子液体性质是一种重要的实验方法.本文主要介绍几种离子液体酸性的探针,着重介绍如何利用这些探针来测定离子液体的酸性强度.As a class of alternative green solvents and catalysts, ionic liquids play an important role in catalytic and organic reactions. Over the last years, acidic ionic liquids have evoked particular attention because of their ability to provide dense reactive sites like liquid acids and non-volatility like solid acids. Therefore, acidic ionic liquids are ideal for replacing traditional liquid/solid acids. The acidity of ionic liquids has strong influence on the activity of the involved chemical reactions and the selectivity of reaction sites. In Diels-Alder reaction, for example, chemical reaction rates and selectivity in acidic ionic liquids proved to be far superior to that observed in traditional polar and nonpolar media. Determination of acidity of ionic liquids, therefore, is very important for understanding the mechanisms of the respective catalytic reactions and searching for high efficient catalysts. In this mini review, we summarized the recent progress in establishing molecular probe-based spectroscopic methods to determine the acidity of ionic liquids. First, phenylamine and its derivatives have been used as UV-visible spectroscopic probes, through which the Hammett acidity functions （H0） can be evaluated. Second, mesityl oxide has been proposed as anuclear magnetic resonance spectroscopic probe. The Hammett acidity can be derived with the help of a calibration curve of 13C NMR spectrum. These two methods determine the BrCnsted acidity of ionic liquids. Third, acetonitrile and pyridine have been employed as infrared spectroscopicprobes, through which the relative strength of Lewis acidity of various ionic liquids can be compared qualitatively. In comparing the three methods, each has its merits and disadvantages. The first two are quantitative methods, whilst the third one is only a qualitative means. The low solubility of the UV-vis probes in ionic liquids may greatly affect their application. Overlapping of peaks may be a big problem of the UV-vis and IR-based methods. Readers are suggested to select

关 键 词：离子液体 酸性强度 探针 红外光谱 13C NMR波谱 

分 类 号：O643.36[理学—物理化学]