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In efforts to develop environmentally harmonious processes and achieve the SDGs, deep eutectic solvents (DESs) have attracted considerable attention in recent years.1-3) A deep eutectic solvent is a eutectic mixture composed of a hydrogen-bond donor and a hydrogen-bond acceptor that becomes liquid around room temperature. Although DESs resemble ionic liquids, they differ in that ionic liquids are single salts consisting of an anion and cation ion pair, whereas DESs are mixtures of two or more components. For example, the eutectic mixture (Product No. C4110) of choline chloride (melting point 302 °C) and urea (melting point 133 °C) exhibits a melting point of 12 °C,4) which is significantly lower than that of each individual component.
DESs have been explored as new green alternatives to conventional organic solvents and ionic liquids, and their applications and uses continue to expand. For example, in the field of organic synthesis, various catalytic reactions have been reported by taking advantage of their high solubility and low volatility.5-7)When a DES is employed in organic synthesis, the product can be recovered by extraction with an organic solvent after the reaction, while the DES containing the dissolved catalyst can be directly reused in the next reaction. As a result, waste solvent generation can be reduced, contributing to process designs with lower waste factors such as the E-factor and PMI.
DESs also exhibit a variety of advantageous properties, including ionic conductivity, flame retardancy, low toxicity, fluorine-free composition, and biodegradability. Owing to these features, numerous applications have been reported, such as CO2 capture,8) recovery of valuable natural products such as quercetin and caffeine from agricultural residues,9) recovery of base metals from waste materials, enzymatic reactions, biodiesel synthesis via transesterification of soybean oil,10) and various electrochemical processes including electrodeposition, coating, and electropolishing. Additional reported uses include antistatic agents and lubricant additives.11)
We have three representative DESs in our product lineup: choline chloride / urea (1:2) (Product No. C4110), choline chloride / ethylene glycol (1:2) (Product No. C4111), and choline chloride / glycerol (1:2) (Product No. C4112). Below, we introduce the physical properties and example usage of each product. Please feel free to contact us regarding custom synthesis or large-scale supply of other deep eutectic solvents as well.
Products
Advantages
- High solvating power and ionic conductivity
- Non-volatile and flame-retardant
- Recyclable
- Environmentally friendly and low-toxicity (fluorine-free)
- Low cost and scalable
Physical Properties
| Product | Melting Point (°C) | Density (g/cm3) | Viscosity (cP) | Ionic Conductivity (mS/cm) |
| Choline Chloride / Urea (1:2) (Product No. C4110） | 12 | 1.25 | 632 - 750 | 0.75 |
| Choline Chloride / Ethylene Glycol (1:2) (Product No. C4111） | −66 | 1.12 | 36 - 52 | 7.61 |
| Choline Chloride / Glycerol (1:2) (Product No. C4112） | −40 | 1.18 | 259 - 376 | 1.05 |
Applications
Negishi Cross Coupling Reaction between Aryl Bromides and Organozinc Compounds 5)
The products can be recovered after the reaction by extraction with CPME. It has been reported that the catalyst remains dissolved in the deep eutectic solvent and can be recycled up to seven times.
Copper-Catalyzed Ligand-Free Ullmann Cross Coupling Reaction 6)
The products can be recovered after the reaction by extraction with CPME. It has been reported that the catalyst remains dissolved in the deep eutectic solvent and can be recycled up to six times.
Natural Amino Acid-Catalyzed Stereoselective Cross Aldol Reaction 7)
The products can be recovered after the reaction by extraction with ethyl acetate. It has been reported that the catalyst remains dissolved in the deep eutectic solvent and can be recycled up to five times.
References
- 1) Deep Eutectic Solvents (DESs) and Their Applications
- 2) Natural Deep Eutectic Solvents – Solvents for the 21st Century
- 3) Metal-Free Deep Eutectic Solvents: Preparation, Physical Properties, and Significance
- 4) Novel solvent properties of choline chloride/urea mixtures
- 5) Scalable Negishi Coupling between Organozinc Compounds and (Hetero)Aryl Bromides under Aerobic Conditions when using Bulk Water or Deep Eutectic Solvents with no Additional Ligands
- 6) Reshaping Ullmann Amine Synthesis in Deep Eutectic Solvents: A Mild Approach for Cu-Catalyzed C–N Coupling Reactions With No Additional Ligands
- 7) L-Isoleucine in a Choline Chloride/Ethylene Glycol Deep Eutectic Solvent: A Reusable Reaction Kit for the Asymmetric Cross-Aldol Carboligation
- 8) A Membrane Contactor Enabling Energy-Efficient CO2 Capture from Point Sources with Deep Eutectic Solvents
- 9) Green extraction of caffeine from coffee pulp using a deep eutectic solvent (DES)
- 10) Choline-based deep eutectic solvents for enzymatic preparation of biodiesel from soybean oil H. Zhao, C. Zhang, T. D. Crittle
- 11) Evaluating water miscible deep eutectic solvents (DESs) and ionic liquids as potential lubricants
