Deep eutectic solvents (DESs) have been used for the purification of oils and the extraction of active ingredients from natural products but little is known about the mechanism of the extraction process. In this study a variety of molecular solutes are dissolved in alkanes and the thermodynamics of transfer into six DESs have been quantified. It is shown that the transfer of most solutes into the DES is endothermic and driven by entropy. The largest partition coefficients were demonstrated by the liquids with the lowest surface tensions and this is thought to arise because the enthalpy of hole formation controlling the rate of solute transfer. Accordingly, it was shown that the size of the solute has an effect on the partition coefficient with smaller solutes partitioning preferably into the DES. As expected, solutes capable of strongly hydrogen bonding partitioned much better into the DES as the enthalpy of transfer was negative.

While ionic liquids and deep eutectic solvents, DESs, have been extensively used for natural product extraction relatively little is known about the factors affecting extraction efficiency. In this study, 7...

It was previously shown that water distributes heterogeneously in deep eutectic solvents (DESs). The aim of this study was to see whether this behavior was common to other hydrogen bonding compounds and determine when a solute formed an emulsion or a homogeneous solution. Pulsed field gradient (PFG) and nuclear Overhauser effect (NOE) NMR, and dynamic light scattering (DLS) are employed to probe the phase behavior of glucose, 1-pentanol and phenol in Ethaline (ethylene glycol: choline chloride, 2:1). By comparing the measured values of self-diffusivities to those calculated assuming Stokesian behavior, it was discovered that glucose forms a homogeneous solution, whereas 1-pentanol forms a heterogeneous mixture. A change in aggregates size of 10 wt% phenol in Ethaline is observed at 313 K. Above 313 K aggregation is enhanced and larger aggregates are formed, suggesting a melting of phenol affects the phase behavior. { 1 H, 1 H}-NOESY NMR showed that glucose interacts strongly with Ethaline whilst with 1-pentanol and phenol this interaction is weaker. DLS experiments further indicated the heterogeneity and homogeneity. Results suggest that solid solutes that are capable of strong hydrogen bonding are soluble in DESs whereas liquid solutes form heterogeneous nanophases due to the weaker solute-solvent interactions and density difference.