Understanding the Formation of Deep Eutectic Solvents: Betaine as a Universal Hydrogen Bond Acceptor

• Published in: ChemSusChem Vol. 13; no. 18; pp. 4916 - 4921
• Main Authors: Abranches, Dinis O., Silva, Liliana P., Martins, Mónia A. R., Pinho, Simão P., Coutinho, João A. P.
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 18.09.2020
• Subjects: Eutectics; green chemistry; Hydrogen bonds; Molecular interactions; natural deep eutectic solvents; non-ideality; Polarity; Solvents; trimethylglycine; zwitterions; zwitterions; natural deep eutectic solvents; non-ideality; green chemistry; trimethylglycine
• ISSN: 1864-5631; 1864-564X
• DOI: 10.1002/cssc.202001331

The mechanism of formation of betaine‐based deep eutectic solvents (DES) is presented for the first time. Due to its polarity unbalance, it was found that betaine displays strong negative deviations from ideality when mixed with a variety of different organic substances. These results pave the way for a comprehensive design of novel deep eutectic solvents. A connection to biologically relevant systems was made using betaine (osmolyte) and urea (protein denaturant), showing that these two compounds formed a DES, the molecular interactions of which were greatly enhanced in the presence of water. Better with betaine: Betaine is an attractive deep‐eutectic‐solvent (DES)‐forming compound due to its sustainable character (non‐toxic, biodegradable, renewable, cheap, osmolyte in biological systems, widespread industrial use). In this work the mechanism of formation of betaine‐based DES is presented and discussed in terms of molecular interactions. A particular system (betaine/urea) is found to be highly water sensitive, encouraging the paradigm of natural DES being the missing link in understanding cellular physiology.