Search

The [S.sub.N]2 reaction of the trifluoromethanesulfonate and bis(trifluoromethanesulfonyl)imide salts of dimethyl-4-nitrophenylsulfonium with chloride ion has followed different pathway to when the same salts have reacted in molecular solvents.

The second-order rate constant ([k.sub.2]) is described for the esterification of methoxyacetic acid with benzyl alcohol. The studies on the effect of solvent basicity have shown that the hydrogen bond basicity of the solvent is the dominant parameter in determining the esterification rate and that the best rates are obtained in low basicity solvents.

Ultraviolet/visible (UV/vis) and fluorescence spectroscopy are used for exploring local solvation of the probe molecule Coumarin 153 (C153) in both the ground ([S.sub.0])and first excited state ([S.sub.1])electronic structures in two gas-expanded liquids (GXLs), acetone and MeOH. The studies have shown that preferential solvation is present at each simulated composition and that the local organic enrichment has increased with C[O.sub.2] concentration.

Molecular dynamics (MD) simulation is used to describe the local solvation and transport effects in gas-expanded liquids (GXLs). The local anisotropic pair correlation function, orientational correlation functions and diffusion rates are described for two systems, C[O.sub.2]-expanded methanol and C[O.sub.2]-expanded acetone at 298 K and pressures up to 6 MPa.

Gas-expanded liquids (GXLs) are a new and benign class of liquid solvents, which might offer many advantages for separations, reactions, and advanced materials. A study focuses on the synergism of experimental techniques with theoretical modeling resulting in a powerful combination for exploring chemical structure and transport in the cybotactic region of GXLs at the nanometer lengthscale.

The study reviews applications involving improved transport, catalyst recycling, and product separation as well as the in situ generation of catalyst. It concluded that although such tunable solvents are in no way a panacea, they do offer the chemical community alternatives that can often be applied creatively to many reaction opportunities.

Nonaqueous biocatalysis is rapidly becoming a desirable tool for chemical and fuel synthesis in both the laboratory and industry. Similarly, ionic liquids are increasingly popular anhydrous reaction media for a number of industrial processes. Consequently, the use of enzymes in ionic liquids as efficient, environment-friendly, commercial biocatalysts is highly attractive. However, issues surrounding the poor solubility and low stability of enzymes in truly anhydrous media remain a significant challenge. Here, we demonstrate for the first time that engineering the surface of a protein to yield protein-polymer surfactant nanoconstructs allows for dissolution of dry protein into dry ionic liquids. Using myoglobin as a model protein, we show that this method can deliver protein molecules with near native structure into both hydrophilic and hydrophobic anhydrous ionic liquids. Remarkably, using temperature-dependent synchrotron radiation circular dichroism spectroscopy to measure half-denaturation temperatures, our results show that protein stability increases by 55 °C in the ionic liquid as compared to aqueous solution, pushing the solution thermal denaturation beyond the boiling point of water. Therefore, the work presented herein could provide a platform for the realization of biocatalysis at high temperatures or in anhydrous solvent systems. [ABSTRACT FROM AUTHOR]

Tracerdiffusion coefficients of CO2in several brineswere measured by 13C pulsed-field gradient NMR at a temperatureof 298 K and at salt molalities of up to 5 mol·kg–1. The brines studied were NaCl(aq), CaCl2(aq), Na2SO4(aq), and a mixed brine prepared from sevensalts: NaCl, CaCl2, MgCl2, KCl, Na2SO4, SrCl2, NaHCO3. The experimentalresults are compared with the predictions of a modified Stokes–Einsteinrelation in which the Stokes–Einstein number is 4 and the hydrodynamicradius of the CO2molecule in aqueous solution is takento be 168 pm, as determined in an earlier study of the (CO2+ H2O) binary system at the same temperature (Cadoganet al. J. Chem. Eng. Data2014, 59, 519−525). This comparison shows agreement to withinthe experimental uncertainty, independent of salt type and molality.We conclude that the modified Stokes–Einstein relation providesa reliable means of estimating the tracer diffusion coefficient ofCO2in aqueous electrolyte solutions, based on knowledgeof the brine viscosity and the hydrodynamic radius of CO2in pure water at the same temperature. [ABSTRACT FROM AUTHOR]

The article presents a review of the study which describes the solvent-solute interactions in room temperature ionic liquids. It focuses on the benefits of using solvents in synthesis and catalysis in ionic liquids on transition metals. The authors contend s that the catalyst determines the outcomes of transition-metal-catalyzed reaction that even the small changes to a ligand can greatly impact catalysis performance.

The application of liquids that are salts at room temperature to chemical synthesis has become a hugely exciting field of study. The greatest promise that these ionic liquids hold is that they might offer process advantages, even novel behaviors that cannot be achieved in molecular solvents. We report here that the SN2 reaction of the trifluoromethanesulfonate and bis(trifluoromethanesulfonyl)imide salts of dimethyl-4-nitrophenylsulfonium ([p-NO2PhS(CH3)2]+[X]-; [X]- = [CF3SO3]-, [N(CF3SO2)2]-) with chloride ion follow a fundamentally different pathway to when the same salts react in molecular solvents. [ABSTRACT FROM AUTHOR]

This study establishes a foundation for the ionic liquid (IL) pretreatment of duckweed biomass. An optimized IL-based process was designed to exploit the unique properties of duckweed including efficient metal removal, potential starch accumulation, and protein accumulation. Two ILs, namely, dimethylethanolammonium formate ([DMEtA][HCOO]) and N,N -dimethylbutylammonium hydrogen sulfate ([DMBA][HSO 4 ]), were investigated for the pretreatment of two duckweed species ( Spirodela polyrhiza and Lemna minor ). The evaluation focused on starch recovery, sugar release, protein recovery, and metal extraction capabilities. [DMEtA][HCOO] demonstrated near-quantitative starch recoveries at 120 °C, while [DMBA][HSO 4 ] showed similar performance at 90 °C within a reaction time of 2 h. Saccharification yields for most pulps exceeded 90% after 8 h of hydrolysis, outperforming "traditional" lignocellulosic biomasses such as miscanthus or sugarcane bagasse. Approximately 50 and 80 wt % of the protein were solubilized in [DMEtA][HCOO] and [DMBA][HSO 4 ], respectively, while the remaining protein distributed between the pulp and lignin. However, the solubilized protein in the IL could not be recovered due to its low molecular weight. Regarding metal extraction, [DMEtA][HCOO] demonstrated higher efficiency, achieving 81% removal of Ni from Lemna minor 's pulps, whereas [DMBA][HSO 4 ] extracted only 28% of Ni with slightly higher pulp concentrations. These findings indicate the need for further optimization in concurrent metal extraction using ILs., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Novel drug candidates are continuously being developed to combat the most life-threatening diseases; however, many promising protein therapeutics are dropped from the pipeline. During biological and industrial processes, protein therapeutics are exposed to various stresses such as fluctuations in temperature, solvent pH, and ionic strength. These can lead to enhanced protein aggregation propensity, one of the greatest challenges in drug development. Recently, ionic liquids (ILs), in particular, biocompatible choline chloride ([Cho]Cl)-based ILs, have been used to hinder stress-induced protein conformational changes. Herein, we develop an IL-based strategy to predict protein aggregation propensity and thermodynamic stability. We examine three key variables influencing protein misfolding: pH, ionic strength, and temperature. Using dynamic light scattering, zeta potential, and variable temperature circular dichroism measurements, we systematically evaluate the structural, thermal, and thermodynamic stability of fresh immunoglobin G4 (IgG4) antibody in water and 10, 30, and 50 wt % [Cho]Cl. Additionally, we conduct molecular dynamics simulations to examine IgG4 aggregation propensity in each system and the relative favorability of different [Cho]Cl-IgG4 packing interactions. We re-evaluate each system following 365 days of storage at 4 °C and demonstrate how to predict the thermodynamic properties and protein aggregation propensity over extended storage, even under stress conditions. We find that increasing [Cho]Cl concentration reduced IgG4 aggregation propensity both fresh and following 365 days of storage and demonstrate the potential of using our predictive IL-based strategy and formulations to radically increase protein stability and storage., Competing Interests: The authors declare the following competing financial interest(s): Shmool, T. A.; Hallett, J. P. Stable Composition. Patent application No. PCT/GB2022/051392, June 1, 2022. Other authors have no conflicts to declare., (© 2022 The Authors. Published by American Chemical Society.)

Acid catalysts play a vital role in the industrial synthesis and production of a plethora of organic chemicals. But, their subsequent neutralization and disposal is also a giant source of waste. For example, for a Friedel-Crafts acylation with AlCl 3, a kilogram of product yields up to 20 kg of (contaminated) waste salt. Other processes are even worse, and this waste is both an environmental and economic shortcoming. Here we address this issue by showing a series of acid catalysts where the neutralization is "built in" to the system and thus eliminates waste. Clearly these will not replace all organic and mineral acid catalysts, but they can replace many. Further, we show how these self-neutralizing catalysts can often eliminate unwanted byproducts, improve selectivity, or elimination of mass transfer limitations by changing from heterogeneous to homogeneous systems. They readily facilitate separations and promote recycling, to promote both green chemistry and good economics. First is near-critical water, or liquid water under pressure, where the K W for dissociation goes up 3-4 decades between 0 degrees C and 250 degrees C, thus facilitating both acid and base catalysis. Moreover, as the exothermic hydrogen bonding diminishes, the dielectric constant goes down to the point at which both salts and organics are soluble in this very hot water. For example, toluene and water are completely miscible at 305 degrees C. This eliminates mass transfer limitations for the reactions, and postreaction cooling not only lowers the K W to neutralize the ions without waste but also results in facile separations from simple liquid-liquid immiscibility. Further, we show the formation of catalysts with alkylcarbonic acids from alcohols and CO2, analogous to carbonic acid from water and CO2. We show a number of applications for these self-neutralizing catalysts, including the formation of ketals, the formation of diazonium intermediates to couple with electron-rich aromatics to produce dye molecules, and the hydration of beta-pinene. Here also these systems often enhance phase behavior to cut mass transfer resistance. In an analogous application we show that peroxide and CO2 gives peroxycarbonic acid, also reversible upon the removal of the CO2, and we show application to epoxidation reactions. The bottom line is that these catalysts afford profound advantages for both green chemistry and improved economics. The methods outlined here have potential for abundant applications, and we hope that this work will motivate such opportunities.