Deep Eutectic Solvents Formed between Choline Chloride and Carboxylic Acids:  Versatile Alternatives to Ionic Liquids

• Published in: Journal of the American Chemical Society Vol. 126; no. 29; pp. 9142 - 9147
• Main Authors: Abbott, Andrew P, Boothby, David, Capper, Glen, Davies, David L, Rasheed, Raymond K
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 28.07.2004
• Subjects: Chemistry; Exact sciences and technology; General and physical chemistry; Solution properties; Solutions; Quaternary ammonium compound; Organic solution; Choline chloride; Electrical conductivity; Carboxylic acid; Temperature effect; Specific viscosity; Composition effect; Surface tension; Experimental study; Physicochemical properties
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja048266j

Deep Eutectic Solvents (DES) can be formed between a variety of quaternary ammonium salts and carboxylic acids. The physical properties are significantly affected by the structure of the carboxylic acid but the phase behavior of the mixtures can be simply modeled by taking account of the mole fraction of carboxylic acid in the mixture. The physical properties such as viscosity, conductivity, and surface tension of these DES are similar to ambient temperature ionic liquids and insight into the cause of these properties is gained using hole-theory. It is shown that the conductivity and viscosity of these liquids is controlled by ion mobility and the availability of voids of suitable dimensions, and this is consistent with the fluidity of other ionic liquids and molten salts. The DES are also shown to be good solvents for metal oxides, which could have potential application for metal extraction.