[Skip to Content](https://www.sigmaaldrich.com#main-content) [![MilliporeSigma](https://www.sigmaaldrich.com/static/logos/purple/millipore_sigma.svg)](https://www.sigmaaldrich.com/US/en) Products Cart0 USEN Products [Login / Register](https://www.sigmaaldrich.com/oidc-sign-in) [Order Lookup](https://www.sigmaaldrich.com/US/en/order-lookup) [Quick Order](https://www.sigmaaldrich.com/US/en/quick-order) Cart0 [Home](https://www.sigmaaldrich.com/US/en)[Reaction Design & Optimization](https://www.sigmaaldrich.com/US/en/applications/chemistry-and-synthesis/reaction-design-and-optimization)Task-Specific Ionic Liquids # Task-Specific Ionic Liquids __Roland St. Kalb1, Michael J. Kotschan1__ Proionic Production of Ionic Substances GmbH, Leoben, Austria __Section Overview__ - [Introduction](https://www.sigmaaldrich.com#introduction) - [Trioctylmethylammonium Thiosalicylate (TOMATS): A Novel, High Performance, Ionic Liquid for the Extraction of Heavy Metals from Aqueous Solutions](https://www.sigmaaldrich.com#tri) - [Other Task-Specific Ionic Liquids](https://www.sigmaaldrich.com#other-task-specific-ionic-liquids) - [Related Products](https://www.sigmaaldrich.com#products) ## [](https://www.sigmaaldrich.com)Introduction Task-specific ionic liquids (TSILs) are a class of ionic liquids designed to perform specific functions or tasks in various applications. Unlike conventional ionic liquids, which are typically used for their solvent properties, TSILs are engineered to have specific functional groups that enable them to interact selectively with certain substances or to facilitate chemical reactions. TSILs contain functional groups tailored for specific applications, such as catalysis, extraction, or separation processes. TSILs often exhibit improved solubility, stability, and selectivity compared to traditional solvents. ![Schematic of Thiourea derivatized Ionic Liquid](https://www.sigmaaldrich.com/content/dam/cms-commons/sigmaaldrich/marketing/global/images/technical-documents/articles/chemistry-and-synthesis/reaction-design-and-optimization/thiourea-derivatized-ionic-liquid.jpg "Schematic of Thiourea derivatized Ionic Liquid") __Figure 1.__Thiourea derivatized Ionic Liquid These ionic liquids were the first to contain specific functionalities to enable well defined chemical properties and therefore undoubtedly be called “designer solvents.” However, these pioneering ionic liquids show some major drawbacks: the hexafluorophosphate anion is known to be quite unstable toward hydrolysis and produces toxic and corrosive HF or fluorides. The toxicity of the imidazolium cation is difficult to be estimated; an expensive toxicological study is risky. The disposal of these fluorous compounds is expensive and problematic. The synthesis at larger scale is complicated; starting materials are expensive. ## [](https://www.sigmaaldrich.com)Trioctylmethylammonium thiosalicylate (TOMATS): A Novel, High Performance, Ionic Liquid for the Extraction of Heavy Metals from Aqueous Solutions To overcome the aforementioned drawbacks—especially in consideration of a possible industrial application at larger scales—and to enhance the performance, proionic Production of Ionic Substances GmbH developed a new Ionic Liquid in their laboratories: Trioctylmethylammonium thiosalicylate (“TOMATS,” Product No. [08354](https://www.sigmaaldrich.com/US/en/product/sial/08354), __Figure 2__). ![Schematic of Trioctylmethylammonium thiosalicylate (TOMATS): A Novel, High Performance, Ionic Liquid for the Extraction of Heavy Metals from Aqueous Solutions](https://www.sigmaaldrich.com/content/dam/cms-commons/sigmaaldrich/marketing/global/images/technical-documents/articles/chemistry-and-synthesis/reaction-design-and-optimization/tomats.jpg "Schematic of Trioctylmethylammonium thiosalicylate (TOMATS): A Novel, High Performance, Ionic Liquid for the Extraction of Heavy Metals from Aqueous Solutions") __Figure 2.__TOMATS TOMATS contains no fluorine and is absolutely stable to any hydrolysis. It therefore does not release HF or fluorides, is not corrosive, and is much easier to dispose. The toxicity of the cation is known from common compounds like trioctylammonium chloride (a phase-transfer catalyst). The toxicity of the anion is known from thiosalicylic acid and its salts; they are found to be irritants. The distribution coefficients of heavy metals typically show values in the range of 1500 to more than 5000, which may be explained by the chelating effect of the ortho- positioned carboxylate group additional to the known formation of metal-thiolates. The synthesis of TOMATS is simple and can be done at industrial scales. ### [](https://www.sigmaaldrich.com)Application of TOMATS __Figure 3__ shows the extraction of copper out of a blue-colored aqueous Cu2+-tetramine phase (left test tube). After adding the TOMATS Ionic Liquid and before shaking, nice diffusion zones can be seen (middle test tube), showing a copper-free, uncolored region and a dark copper-containing upper region. After shaking and waiting for the separation of the phases, all the copper is extracted into the upper phase, forming an organic, dark-colored copper compound (right test tube). ![Three test tubes showing the extraction of copper.](https://www.sigmaaldrich.com/content/dam/cms-commons/sigmaaldrich/marketing/global/images/technical-documents/articles/chemistry-and-synthesis/reaction-design-and-optimization/extraction-copper.jpg "Three test tubes showing the extraction of copper.") __Figure 3.__Extraction of Copper Phase separation sometimes can last a long period of time because of the relative high viscosity of TOMATS of 1,500 mPa.s at 20 °C. This drawback can be overcome by either adding some percent of a water-immiscible organic solvent like ethyl acetate or dichloromethane (decreasing the viscosity down to hundred mPa.s), or by heating. Phase separation can be optimized using a centrifuge and adding some sodium sulfate to the aqueous phase before shaking. If the aqueous phase still looks turbid, it can be filtered through a common membrane filter (μM pore size). ### [](https://www.sigmaaldrich.com)Characterization of TOMATS Appearance: olive green, viscous liquid  Solubility:  - Soluble in alcohols, ethyl acetate, THF, acetonitrile, acetone, dichloromethane, DMSO - nsoluble in water, hexane Nernst distribution coefficients: 1 Cd2+ >1,500; Cu2+ >3,000; Pb2+, Hg2+ >5,000  Refractive index: nD20 = 1.5185  Leaching into aqueous phase: <0.5%  Density, Viscosity: | | | | | | |-------------|----------------|-------------------------------|----------------|----------------| | | TOMATS 100% | TOMATS 95% (5% ethyl acetate) | | | | __T \[°C]__ | __d \[g/cm3]__ | __n \[mPa.s]__ | __d \[g/cm3]__ | __n \[mPa.s]__ | | 20 | 0.9556 | 1.5 | 0.9534 | 509 | | 40 | 0.9445 | 352 | 0.9424 | 158 | | 60 | 0.9325 | 119 | 0.93 | 63 | | 80 | 0.9213 | 50 | 0.9185 | 30 | ## [](https://www.sigmaaldrich.com)Other Task-Specific Ionic Liquids Recently, zwitterionic, sulfonic acid-functionalized ionic liquids have been used as alternatives to conventional acids in acid-catalyzed reactions.2 Several task-specific ionic liquids for this application are now commercially available. ## Related Products Sorry, an unexpected error has occurred Response not successful: Received status code 500 ### References 1\. Visser AE, Swatloski RP, Reichert WM, Davis Jr. JH, Rogers RD, Mayton R, Sheff S, Wierzbicki A. 2001. Task-specific ionic liquids for the extraction of metal ions from aqueous solutions. Chem. Commun..(1):135-136. [https://doi.org/10.1039/b008041l](https://doi.org/10.1039/b008041l) 2\. Cole AC, Jensen JL, Ntai I, Tran KLT, Weaver KJ, Forbes DC, Davis JH. 2002. Novel Brønsted Acidic Ionic Liquids and Their Use as Dual Solvent?Catalysts. J. Am. Chem. Soc.. 124(21):5962-5963. [https://doi.org/10.1021/ja026290w](https://doi.org/10.1021/ja026290w) 3\. Gu Y, Shi F, Deng Y. 2003. SO3H-functionalized ionic liquid as efficient, green and reusable acidic catalyst system for oligomerization of olefins. Catalysis Communications. 4(11):597-601. 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