Sustainable hydrophobic terpene-based eutectic solvents for the extraction and separation of metals

Sustainable hydrophobic eutectic solvents, composed of low-priced and biodegradable terpenes and fatty acids, were used for the extraction and separation of Cu(ii) from other transition metals in mildly acidic solutions. Multiple parameters were evaluated for metal extraction and the hydrophobic eutectic solvent was successfully recovered and reused.

Aqueous solubilities of five N-(diethylaminothiocarbonyl)benzimido derivatives at T = 298.15 K

N-(diethylaminothiocarbonyl)benzimido derivatives are polar multifunctional substances. A set of these compounds was synthesised by successive substitution on the enamine side, resulting in similar substances with different polarities, providing a set of model compounds with respect to the study of substituent effects on physico-chemical properties. Experimental aqueous solubility data, at T = 298.15 K, of N-(diethylaminothiocarbonyl)benzamidine, PhCNH2NCSNEt2 (1),N-(diethylaminothiocarbonyl)-N'-phenylbenzamidine, PhCNHPhNCSNEt2 (2), N-(diethylaminothiocarbonyl)-N'-monoethylbenzamidine, PhCNHEtNCSNEt2 (3), N-(diethylaminothiocarbonyl)-N',N'-diethylbenzamidine, PhCNEt2NCSNEt2 (4), and N-(diethylaminothiocarbonyl)benzimido ethylester, PhCOEtNCSNEt2 (5) were measured at T = 298.15 K. The obtained data are supplemented by COSMO-RS aqueous solubility predictions as well as other environmentally important partition coefficients. This information is shown in a two-dimensional chemical space diagram, providing indications about the compartment into which the bulk of the compounds is likely to concentrate. The expected quality of COSMO-RS predictions for this type of screening exercise is illustrated on a set of pesticides with established thermophysical property data.

Solubility and solvation of monosaccharides in ionic liquids

Herein, solubility experimental data for six monosaccharides, viz.d-(+)-glucose, d-(+)-mannose, d-(-)-fructose, d-(+)-galactose, d-(+)-xylose and l-(+)-arabinose, in four ionic liquids (ILs), at temperatures ranging from 288.2 to 348.2 K, were obtained aimed at gathering a better understanding of their solvation ability and molecular-level mechanisms which rule the dissolution process. To ascertain the chemical features that enhance the solubility of monosaccharides, ILs composed of dialkylimidazolium or tetraalkylphosphonium cations combined with the dicyanamide, dimethylphosphate or chloride anions were investigated. It was found that the ranking of the solubility of monosaccharides depends on the IL; yet, d-(+)-xylose is always the most soluble while d-(-)-fructose is the least soluble monosaccharide. The results obtained show that both the IL cation and the anion play a major role in the solubility of monosaccharides. Finally, from the determination of the respective thermodynamic properties of solution, it was found that enthalpic contributions are dominant in the solubilization process. However, the observed differences in the solubilities of monosaccharides in 1-butyl-3-methylimidazolium dicyanamide are ruled by a change in the entropy of solution.

Why are some cyano-based ionic liquids better glucose solvents than water?

Among different classes of ionic liquids (ILs), those with cyano-based anions have been of special interest due to their low viscosity and enhanced solvation ability for a large variety of compounds. Experimental results from this work reveal that the solubility of glucose in some of these ionic liquids may be higher than in water - a well-known solvent with enhanced capacity to dissolve mono- and disaccharides. This raises questions on the ability of cyano groups to establish strong hydrogen bonds with carbohydrates and on the optimal number of cyano groups at the IL anion that maximizes the solubility of glucose. In addition to experimental solubility data, these questions are addressed in this study using a combination of density functional theory (DFT) and molecular dynamics (MD) simulations. Through the calculation of the number of hydrogen bonds, coordination numbers, energies of interaction and radial and spatial distribution functions, it was possible to explain the experimental results and to show that the ability to favorably interact with glucose is driven by the polarity of each IL anion, with the optimal anion being dicyanamide.

Densities, Viscosities and Derived Thermophysical Properties of Water-Saturated Imidazolium-Based Ionic Liquids

In order to evaluate the impact of the alkyl side chain length and symmetry of the cation on the thermophysical properties of water-saturated ionic liquids (ILs), densities and viscosities as a function of temperature were measured at atmospheric pressure and in the (298.15 to 363.15) K temperature range, for systems containing two series of bis(trifluoromethylsulfonyl)imide-based compounds: the symmetric [C n C n im][NTf2] (with n = 1-8 and 10) and asymmetric [C n C1im][NTf2] (with n = 2-5, 7, 9 and 11) ILs. For water-saturated ILs, the density decreases with the increase of the alkyl side chain length while the viscosity increases with the size of the aliphatic tails. The saturation water solubility in each IL was further estimated with a reasonable agreement based on the densities of water-saturated ILs, further confirming that for the ILs investigated the volumetric mixing properties of ILs and water follow a near ideal behaviour. The water-saturated symmetric ILs generally present lower densities and viscosities than their asymmetric counterparts. From the experimental data, the isobaric thermal expansion coefficient and energy barrier were also estimated. A close correlation between the difference in the energy barrier values between the water-saturated and pure ILs and the water content in each IL was found, supporting that the decrease in the viscosity of ILs in presence of water is directly related with the decrease of the energy barrier.

Salting-in with a salting-out agent: explaining the cation specific effects on the aqueous solubility of amino acids

Although the understanding of ion specific effects on the aqueous solubilities of biomolecules is crucial for the development of many areas of biochemistry and life sciences, a consensual and well-supported molecular picture of the phenomena has not yet been established. Mostly, the influence of cations and the nature of the molecular interactions responsible for the reversal of the Hofmeister trend in aqueous solutions of amino acids and proteins are still defectively understood. Aiming at contributing to the understanding of the molecular-level mechanisms governing the cation specific effects on the aqueous solubilities of biocompounds, experimental solubility measurements and classical molecular dynamics simulations were performed for aqueous solutions of three amino acids (alanine, valine, and isoleucine), in the presence of a series of inorganic salts. The evidence gathered suggests that the mechanism by which salting-in inducing cations operate in aqueous solutions of amino acids is different from that of anions, and allows for a novel and consistent molecular description of the effect of the cation on the solubility based on specific interactions of the cations with the negatively charged moieties of the biomolecules.