Deciphering the impact of both hydrogen bond donor and acceptor on the physicochemical properties of eutectic solvents

Solvent selection plays a crucial role in many chemical reactions and solvent tunability has the potential to improve many of them. However, commonly used organic solvents only offer certain interactions, hindering their usability. In this study, we explore the possibility of solvent tuning by studying the physicochemical properties of both binary and ternary eutectic solvents. Here, we rationally designed solvents by varying the number of carbons of hydrogen bond acceptors (HBAs) and hydrogen bond donors (HBDs), and generating linear combinations of binary solvents to form ternary and quaternary solvents. The physical properties we studied were density and viscosity, while the chemical properties were acidity, basicity and polarity as determined by the Kamlet-Taft solvatochromic scale. The results showed that the HBD dictated the overall physicochemical properties of the solvent since a change in number of carbons led to significant changes in all the properties. Meanwhile, the acceptor only influenced physical properties as they were the only ones affected by a change in the number of carbons in the HBA. Additionally, using ternary and quaternary mixtures of these eutectic solvents, we demonstrated how solvent tunability is achievable as they exhibit a linear relationship between solvent properties and composition. Developing an understanding of how the individual components affect the overall physicochemical properties of ternary eutectic solvents is crucial for the fine-tuning of these solvents to improve chemical reactions. Synopsis: This study explores the composition-properties relationship of eutectic solvents and their mixtures to establish design-rules for sustainable solvents. • The physicochemical properties of eutectic solvents can be tuned by composition. • Carbon chain length of hydrogen bond donor controls chemical properties. • Linear mixtures of binary solvents result in linear properties of ternary solvents.