A flat mask‐based model is almost universally used in macromolecular crystallography to account for disordered (bulk) solvent. This model assumes any voxel of the crystal unit cell that is not ...occupied by the atomic model is occupied by the solvent. The properties of this solvent are assumed to be exactly the same across the whole volume of the unit cell. While this is a reasonable approximation in practice, there are a number of scenarios where this model becomes suboptimal. In this work, we enumerate several of these scenarios and describe a new generalized approach to modeling the bulk‐solvent which we refer to as mosaic bulk‐solvent model. The mosaic bulk‐solvent model allows nonuniform features of the solvent in the crystal to be accounted for in a computationally efficient way. It is implemented in the computational crystallography toolbox and the Phenix software.
The basicities of simple organic bases – aliphatic and aromatic amines, amidines, phosphazenes, as well as saturated and unsaturated nitrogen heterocycles – are examined in acetonitrile, dimethyl ...sulfoxide, tetrahydrofuran, water and the gas phase. The basicities (pKaH values) of conjugate acids of a large variety of bases in these media are presented and discussed. Equations employing easily usable structural descriptors have been derived for approximately converting basicities from acetonitrile to other solvents. Recommendations are given on their practical use and a number of pKaH values that are experimentally unavailable are estimated from these relationships. An important part of the minireview is a large compilation of pKaH and GB values of the compounds in solvents and the gas phase, respectively, as well as the revised basicity scale in acetonitrile, now containing more than 270 pKaH values.
Basicity values for simple nitrogen bases in different solvents and in the gas phase were compiled and discussed. The self‐consistent basicity scale in acetonitrile was updated and expanded to contain 279 compounds. Simple equations for conversion of the pKaH values from acetonitrile to other solvents have been formulated and discussed.
An efficient and environment friendly process for the synthesis of α-aminophosphonates has been devised. Through a one-pot three-component condensation of various aldehydes, amines, and triethyl ...phosphite in the presence of Fe3O4@SiO2-imid-PMAn nanoparticles as magnetic catalysts under solvent-free conditions and ultrasonic irradiation, α-aminophosphonates were obtained with excellent yields. The reactions under solvent-free conditions at room temperature are compared with the ultrasonic-assisted reactions. This new procedure has notable advantages such as short reaction time, excellent yields, easy purification, and the absence of any tedious workup or purification. The aforementioned catalyst could be easily recovered by an external magnetic field and can be reused for six consecutive reaction cycles without significant loss of activity. In addition, SEM and DLS of the catalyst after the reaction cycle were investigated.
The global bio-based chemical market is growing in size and importance. Bio-based solvents such as glycerol and 2-methyltetrahydrofuran are often discussed as important introductions to the ...conventional repertoire of solvents. However adoption of new innovations by industry is typically slow. Therefore it might be anticipated that neoteric solvent systems (e.g., ionic liquids) will remain niche, while renewable routes to historically established solvents will continue to grow in importance. This review discusses bio-based solvents from the perspective of their production, identifying suitable feedstocks, platform molecules, and relevant product streams for the sustainable manufacturing of conventional solvents.
‘Ideal’ solvents in biocatalysis have to fulfill a large number of requirements, such as high substrate solubility, high enzyme activity and stability, and positive effects on reaction equilibrium. ...In the past decades, many enzymatic synthesis routes in water-based and nonaqueous (organic solvents, ionic or supercritical fluids) reaction media have been developed. However, no solvent meets every demand for different reaction types at the same time, and there is still a need for novel solvents suited for different reaction types and applications. Deep eutectic solvents (DESs) have recently been evaluated as solvents in different biocatalytic reactions. They can improve substrate supply, conversion, and stability. The best results were obtained when the DES is formed by the substrates of an enzymatic reaction.
A wide range of inexpensive renewables can be used as components of deep eutectic solvents; therefore, the solvents are often biodegradable, nontoxic, nonvolatile, and nonflammable.
A broad range of enzymatic and chemo-enzymatic synthesis reactions can be performed in deep eutectic solvents. Most of the reactions, covering transesterifications, epoxidations, and C–C bond formations, are catalyzed by lipases.
Deep eutectic solvents can be used to enable new biocatalytic synthesis routes that cannot be realized in conventional reaction media (i.e., aqueous buffers).
Components of deep eutectic solvents can be used as substrate and solvent at the same time; this virtually solvent-free approach enables processes with high substrate conversion and high atom efficiency.
The present work aims to determine to what extent the value of the dielectric constant of the solvent can influence the dative bond in Lewis electron pair bonding systems. For this purpose, two ...different systems, namely H
B←NH
and {Zn←(NH
)}
, were studied in selected solvents with significantly different dielectric constants. Based on the results from state-of-the-art computational methods using DFT, constrained DFT, energy decomposition analyses, solvent accessible surface area, and charge transfer calculations, we found that the stability of the neutral H
B←NH
system increases with increasing solvent polarity. In contrast, the opposite trend is observed for the positively charged {Zn←(NH
)}
. The observed changes are attributed to different charge redistributions in neutral and charged complexes, which are reflected by a different response to the solvent and are quantified by changes in solvation energies.
•Green solvents SFE, SWE and NADES are promising for green extraction.•Increasing use of SFE at industrial level for a lot of applications in different industries.•SWE is suitable for extraction of ...both, polar and non-polar compounds.•NADES have unique properties and possibility of designing it for particular purpose.•Green solvents are solvent for future industry.
In many industrial processes, large quantities of volatile and flammable organic solvents are used in various reaction systems and separation steps define a major part of the environmental and economic performance of a process. Accordingly, a growing area of research in the development of green technologies is devoted to designing new, environmentally-friendly, and tunable solvents the use of which would meet both technological and economical demands. A brief overview of the up to date knowledge regarding most proposed green solvents, including supercritical and subcritical fluids (e.g. CO2 and water) and natural deep eutectic solvents is presented herein, with a special emphasis on green extraction of plant biologically active compounds.
Phlorotannins are secondary metabolites produced mainly by brown seaweeds (Phaeophyceae) and belong to the class of polyphenolic compounds with diverse bioactivities. The key factors in the ...extraction of polyphenols are the selection of a suitable solvent, method of extraction and selection of optimal conditions. Ultrasonic-assisted extraction (UAE) is one of the advanced energy-saving methods suitable for the extraction of labile compounds. Methanol, acetone, ethanol and ethyl acetate are the most commonly used solvents for polyphenol extraction. As alternatives to toxic organic solvents, a new class of green solvents, natural deep eutectic solvents (NADES), has been proposed for the efficient extraction of a wide range of natural compounds including polyphenols. Several NADES were screened previously for the extraction of phlorotannins; however, the extraction conditions were not optimized and chemical profiling of NADES extract was not performed. The purpose of this work was to study the effect of selected extraction parameters on the phlorotannin content in NADES extract from
optimization of extraction conditions and chemical profiling of phlorotannins in the NADES extract. A fast and green NADES-UAE procedure was developed for the extraction of phlorotannins. Optimization was performed through an experimental design and showed that NADES (lactic acid:choline chloride; 3:1) provides a high yield (137.3 mg phloroglucinol equivalents per g dry weight of algae) of phlorotannins under the following extraction conditions: extraction time 23 min, 30.0% water concentration and 1:12 sample to solvent ratio. The antioxidant activity of the optimized NADES extract was equal to that of EtOH extract. In total, 32 phlorotannins have been identified (one trimer, two tetramers, six pentamers, four hexamers, six heptamers, six octamers and seven nonamers) in NADES extracts from arctic
using the HPLC-HRMS and MS/MS technique. It was noted that all the above-mentioned phlorotannins were identified in both EtOH and NADES extracts. Our results suggest that NADES could be considered as an alternative to the conventional techniques for the effective extraction of phlorotannins from
with high antioxidant potential.
Deep eutectic solvents have emerged in green chemistry only seventeen years ago and yet resulted in a plethora of publications covering various research areas and diverse fields of application. Deep ...eutectic solvents appear as promising alternatives to conventional organic solvents due to their straightforward preparation using highly accessible and natural compounds. They display also high tunability. Here we present the classification and preparation methods of deep eutectic solvents. We detail their physicochemical properties such as phase behavior, density, viscosity, ionic conductivity, surface tension, and polarity. Properties are controlled by the choice of the forming compounds, molar ratio, temperature, and water content.
PDF
