物理化学学报 >> 2005, Vol. 21 >> Issue (05): 528-533.doi: 10.3866/PKU.WHXB20050514

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离子液体酸性的红外光谱探针法研究

王晓化; 陶国宏; 吴晓牧; 寇元   

  1. 北京大学化学与分子工程学院, 分子动态与稳态国家重点实验室, 北京    100871
  • 收稿日期:2004-11-03 修回日期:2005-01-19 发布日期:2005-05-15
  • 通讯作者: 寇元 E-mail:yuankou@pku.edu.cn

Investigation of the Acidity of Ionic Liquids by IR Spectroscopy

WANG Xiao-Hua; TAO Guo-Hong; WU Xiao-Mu; KOU Yuan   

  1. State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry and Molecular Engineering, Peking University, Beijing    100871
  • Received:2004-11-03 Revised:2005-01-19 Published:2005-05-15
  • Contact: KOU Yuan E-mail:yuankou@pku.edu.cn

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摘要： 以吡啶和乙腈分子为探针, 使用红外光谱法研究了常用室温离子液体的酸性. 采用吡啶为探针分子时, 出现的～1450 cm－1、～1540 cm－1吸收带可以分别指示离子液体的Lewis、Brønsted酸性；采用乙腈为探针分子时, ～2253 cm－1的C≡N伸缩振动向高波数移动并伴有新峰的出现，可以指示离子液体的Lewis酸性。可以通过比较吡啶探针～1450 cm－1吸收带的峰位置对离子液体的Lewis酸强度进行排序，并且可以用乙腈探针更灵敏地区分出不同离子液体的Lewis酸的强度，使用该方法研究了离子液体的结构对其Brønsted / Lewis酸性的影响。

关键词: 离子液体, Lewis酸性, Brø, nsted酸性, 酸性测定, 红外光谱法

Abstract: The determination of the acidity of ionic liquids is of crucial significance to the utilization of ionic liquids. By using pyridine and acetonitrile as IR spectroscopic probes, the acidity of common room temperature ionic liquids was determined. For the probe pyridine, the IR band near 1450, 1540 cm－1 of pyridine is indicative the Lewis/Brønsted acidity of ionic liquids respectively. For another probe acetonitrile, the increase of the C≡N stretching wave number near 2253 cm－1 with a new band appear at the higher wave number is indicative of the Lewis acidity. The influence of the structure of ionic liquids on the Lewis/Brønsted acidity by the IR spectroscopy was investigated. The Lewis acid strength of different ionic liquids has been compared through the shift of the 1450 cm－1 of pyridine. A more obvious comparison of the Lewis acid intensity of different ionic liquids has been made by acetonitrile probe.

Key words: Ionic liquids, Lewis acidity, Brø, nsted acidity, Acidity determination, IR spectroscopy