Effects of Alkyl Chain Length and Solvents on Thermodynamic Dissociation Constants of the Ionic Liquids with One Carboxyl Group in the Alkyl Chain of Imidazolium Cations

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• 作者：Yuehua Chen ; Huiyong Wang ; Jianji Wang
• 刊名：Journal of Physical Chemistry B
• 出版年：2014
• 出版时间：May 1, 2014
• 年：2014
• 卷：118
• 期：17
• 页码：4630-4635
• 全文大小：224K
• 年卷期：v.118,no.17(May 1, 2014)
• ISSN：1520-5207

文摘

Thermodynamic dissociation constants of the Br酶nsted acidic ionic liquids (ILs) are important for their catalytic and separation applications. In this work, a series of imidazolium bromides with one carboxylic acid substitute group in their alkyl chain ([{(CH₂)_nCOOH}mim]Br, n = 1,3,5,7) have been synthesized, and their dissociation constants (pK_a) at different ionic strengths have been determined in aqueous and aqueous organic solvents at 0.1 mole fraction (x) of ethanol, glycol, iso-propanol, and dimethyl sulfoxide by potentiometric titrations at 298.2 K. The standard thermodynamic dissociation constants (pK_a^T) of the ILs in these solvents were calculated from the extended Debye鈥揌眉ckel equation. It was found that the pK_a values increased with the increase of ionic strength of the media and of the addition of organic solvent in water. The pK_a^T values also increased with the increase of the alkyl chain length of cations of the ILs. In addition, the effect of solvent nature on pK_a^T values is interpreted from solvation of the dissociation components and their Gibbs energy of transfer from water to aqueous organic solutions.