Number Of Solvents Research Articles

Sodium Alkyl(trimethylsilyl)amides: Substituent- and Solvent-dependent Solution Structures and Reactivities.

The preparation of sodium isopropyl(trimethylsilyl)amide (NaPTA), sodium (1-phenylethyl)(trimethylsilyl)amide (NaPETA), sodium tert-butyl(trimethylsilyl)amide (NaBTA), and isotopologues [15N]NaPTA and [15N]NaBTA are described. Solution structural studies using a combination of 29Si NMR spectroscopy, the Method of Continuous Variations, and density functional theory computations provided insights into aggregation and solvation in a range of solvents including toluene, N,N-dimethylethylamine, triethylamine, MTBE, THF, 1,2-dimethoxyethane (DME), diglyme, N,N,N',N'-tetramethylethylenediamine (TMEDA), N,N,N',N'-tetramethylcyclohexanediamine (TMCDA), N,N,N',N″,N″-pentamethyldiethylenetriamine (PMDTA). 12-crown-4, 15-crown-5, and 18-crown-6 revealed solvent- and substituent-dependent dimer-monomer mixtures with affiliated solvation numbers. Complexation of the three crown ethers documented both crown and substituent dependencies. Qualitative studies of reactivity showed a variety of reactions of NaPETA. Aminolysis of methyl benzoate with dialkylamines mediated by NaPTA afforded high yields of benzamides. Quantitative rate studies of aminolysis of methyl benzoate by NaPTA revealed a 47,000-fold range of rates. Detailed rate studies in toluene and THF showed dimer-based mechanisms. The role of primary- and secondary-shell solvation by THF is discussed, including nuances of methods used to separate the two contributions. PMDTA-solvated NaPTA monomer reacts as a monomer whereas bis-diglyme solvated monomer reacts as a dimer. Rate studies exploring the structure-reactivity correlations of the three crown ethers show mono- and bis-crown-based pathways in which 15-crown-5─the crown ether often said to be of choice for sodium─was decidedly inferior as an accelerant.

Study of the Optical and Acoustic Parameters and Surface Tensions of 3,4,4′-Trichlorodiphenylurea in Binary Mixtures with Different Organic Solvents between (293.15 and 323.15) K

In the present investigations, the density, refractive index and speed of sound for pure organic solvents and binary liquid mixtures of 3,4,4′-Trichlorodiphenylurea between (293.15 and 323.15) K temperatures have been measured up to the solubility limit. From these experimental results, the acoustic impedance, the isentropic compressibility coefficient, the space-filling factor, the specific refraction, the relaxation strength, the intermolecular free length, the surface tension, the solubility and the solvation number of triclocarban in six organic solvents, namely ethyl alcohol, n-Propyl alcohol, n-Butyl alcohol, Tetrahydrofuran, N,N-Dimethylformamide and N,N-Dimethylacetamide have been computed. The studied acoustic and optical parameters and surface tension behavior versus temperature in pure solvents and binary mixtures were useful in understanding the nature and the extent of interaction between the solute and solvent molecules. The results also show the presence of higher degree of interaction between triclocarban and nitrogen-containing solvents in comparison with other solvents. The distribution of triclocarban in water/organic solvent mixtures is frequently encountered in wastewater treatment plants.

Effect of Cage Occupancies on Molecular Vibrations of Methane in Structure H Clathrate Hydrate: Ab Initio Molecular Dynamics Simulation.

The structure H (sH) of methane hydrate, which has a distinctive structure with large (LL) cages capable of encapsulating multiple methane molecules, has been suggested as a methane reservoir in large icy bodies such as Titan, making it important in planetary science. This high-pressure phase, which exists in the GPa range, lends itself to the study of methane states and dynamics using powerful experimental techniques such as IR and Raman spectroscopy. However, the interpretation of the vibrational spectra of methane in the sH structure has been challenging because of the spectral complexities. The signals attributed to the methane molecules in the LL cage, as well as those of the other two cage types, overlap in the spectra. In this study, we investigated the microscopic origins of the shape of the C-H stretching vibration spectrum of methane in the LL cage using ab initio molecular dynamics (AIMD) simulations. For a single methane molecule in the LL cage, the ν3 band of the C-H stretching mode was observed at a higher frequency typical of isolated molecules in vacuum due to the large size of the LL cage. As the number of methane molecules in the LL cage increased beyond one, a tendency to blue-shift with increasing methane occupancy was observed, consistent with a loose-cage-tight-cage model. By characterizing the time correlation function of methane stretching vibrations based on the solvation number of methane and water molecules proximal to methane within the LL cage, we showed that the complicated spectral line shape observed in cases of higher methane occupancy in the LL cage resulted from the wider variation of the solvation shell states. Analysis of the solvation structures of the AIMD trajectories provided interpretations of the experimental spectral line shape, demonstrating the complementary nature of AIMD to the experiment and its effectiveness in analysis.

Use of di-(2-ethylhexyl)-orthophosphoric acid for the extraction of lanthanum, neodymium, samarium and yttrium from nitric acid solutions

The process of separating rare-earth elements into individual components is considered the most important problem in rare-earth technology because of the similarity in their physical and chemical properties. Currently in the world dialkyl phosphate compounds are widely used as effective extractors for rare earths. However, most extraction processes have been studied from hydrochloric acid or perchlorate solutions. In Russia, tributyl phosphate has long been used to extract rare earths from nitric acid solutions, but the distribution coefficients of the elements are not high, and the process must be repeated multiple times. In this study di-(2-ethylhexyl)-orthophosphoric acid was used for the extraction of lanthanum, neodymium, samarium, and yttrium from nitric acid solutions. When the concentration of nitric acid increased, distribution coefficient of elements gradually decreased to minimum (in the range of 1 to 5M) then increased backward. However, when the concentration was too high (C > 5M), nitric acid was extracted to the organic phase due to the properties of the phosphoryl group. Moreover, the study of dependence of solvation number of neodymium on the concentrations of nitric acid shows that rare earths in the organic phase can be extracted as Re(HA2)3 (C < 1M) or Re(NO3)3«3HA (C > 5M).

Dominant Solvent-Separated Ion Pairs in Electrolytes Enable Superhigh Conductivity for Fast-Charging and Low-Temperature Lithium Ion Batteries.

The low ionic conductivities of aprotic electrolytes hinder the development of extreme fast charging technologies and applications at low temperatures for lithium-ion batteries (LIBs). Herein, we present an electrolyte with LiFSI in acetone (DMK). In DMK electrolytes, the solvation number is three, and solvent-separated ion pairs (SSIPs) are the dominant structure, which is largely different from other linear aprotic electrolytes where salts primarily exist as contact ion pairs (CIPs). With incompact solvation structures due to the weak solvation ability of DMK with Li+, the ionic conductivity reaches 45 mS/cm at room temperature. The percentage of SSIPs increases as temperatures decrease in DMK electrolytes, which is totally different from the carbonate-based electrolytes but greatly beneficial to low-temperature ionic conductivity. With the appropriate addition of VC and FEC, DMK-based electrolytes still exhibit a superhigh ionic conductivity. Even at -40 °C, the ionic conductivity is greater than 10 mS/cm. With DMK-based electrolytes, LIBs with thick LiFePO4 electrodes can be cycled at high rates and at low temperatures.

Thermodynamic Properties of Pyridine Based 1,3,4-Oxadiazole Scaffolds

Background: The present work describes the synthesis, characterization, and thermo-acoustical parameters of binary solutions of 1-(2-(4-fluorophenyl)-5-(pyridin-4-yl)- 1,3,4-oxadiazol-3(2H)-yl)-3-(pyridin-2-yl)prop-2-en-1-one, (AS1-08) and 1-(2-(4- methoxyphenyl)-5-(pyridin-4-yl)-1,3,4-oxadiazol-3(2H)-yl)-3-(pyridin-2-yl)prop-2-en-1- one, (AS1-12) in dimethyl sulfoxide (DMSO) and N, N-dimethylformamide (DMF) were estimated. Methods: Viscosity, ultrasonic velocity, and density methods at different solvents (DMSO and DMF) and different temperatures (298.15, 308.15, and 318.15 K) were used during the experimental research work. Results: Some acoustic parameters such as adiabatic compressibility (κs), intermolecular free path length (Lf), Rao’s molar sound function (Rm), Van der Waals constant (b), internal pressure (π), free volume (Vf) and solvation number (Sn) were calculated. The results obtained were interpreted in terms of solute-solvent and solute-solute interactions. Conclusion: The thermodynamic and various acoustical properties were determined at three different temperatures viz. (298.15, 308.15, and 318.15 K) at atmospheric pressure. Likewise, the similarity between experimental results of the binary solutions was studied to analyze how the change in the structural modification and solvent changes the values of Gibbs energy of activation (ΔG*), enthalpy of activation (ΔH*), and entropy of activation (ΔS*).

Regulating the interfacial chemistry of graphite in ethyl acetate‐based electrolyte for low‐temperature Li‐ion batteries

AbstractLithium‐ion batteries suffer from severe capacity loss and even fail to work under subzero temperatures, which is mainly due to the sluggish Li+ transportation in the solid electrolyte interphase (SEI) and desolvation process. Ethyl acetate (EA) is a highly promising solvent for low‐temperature electrolytes, yet it has poor compatibility with graphite (Gr) anode. Here, we tuned the interfacial chemistry of EA‐based electrolytes via synergies of anions. ODFB− with low solvation numbers, participates in the solvation sheath, significantly reducing the desolvation energy. Meanwhile, combined with the high dissociation of FSI−, the reduction of both anions constructs an inorganic‐rich SEI to improve interfacial stability. The electrolyte enables Gr anode to deliver a capacity of 293 mA h g−1 and 2.5 Ah LiFePO4||Gr pouch cell to exhibit 96.85% capacity retention at −20°C. Remarkably, LiFePO4||Gr pouch cell with the designed electrolyte can still retain 66.28% of its room‐temperature capacity even at −40°C.

Review of Density and Ultrasonic Velocity of Various Complexes and Its Applications

This review paper delves into the fundamental principles, measurement techniques, and diverse applications of ultrasonic velocity and density. Ultrasonic velocity serves as a crucial parameter in various fields such as materials science, acoustics, and medical diagnostics whereas density is used for identifying substances, quality control, analyzing mixtures, assessing purity, explaining buoyancy, determining concentrations, calibrating instruments, monitoring pollution, and understanding reactivity. This paper provides an in-depth exploration of the underlying concepts, different measurement methods, and the wide-ranging applications of ultrasonic velocity and density. The ultrasonic velocity and density data have also been used to evaluate various acoustic parameters such as isentropic compressibility, apparent isentropic molar compressibility, solvation number of the solute and relative association. Ultrasonic velocity measurements are found to be useful for on-line assessment of the extent of degradation of mechanical properties associated with precipitation of intermetallics. Keywords: Density, Ultrasonic velocityThis review paper delves into the fundamental principles, measurement techniques, and diverse applications of ultrasonic velocity and density. Ultrasonic velocity serves as a crucial parameter in various fields such as materials science, acoustics, and medical diagnostics whereas density is used for identifying substances, quality control, analyzing mixtures, assessing purity, explaining buoyancy, determining concentrations, calibrating instruments, monitoring pollution, and understanding reactivity. This paper provides an in-depth exploration of the underlying concepts, different measurement methods, and the wide-ranging applications of ultrasonic velocity and density. The ultrasonic velocity and density data have also been used to evaluate various acoustic parameters such as isentropic compressibility, apparent isentropic molar compressibility, solvation number of the solute and relative association. Ultrasonic velocity measurements are found to be useful for on-line assessment of the extent of degradation of mechanical properties associated with precipitation of intermetallics. Keywords: Density, Ultrasonic velocity

Experimental determination of solvation free energy of protons in non-protic ionic liquids using Raman spectroscopy.

Room temperature imidazolium-based ionic liquids (ILs) often present super-acidity, which can be characterized by the free energy of solvation of protons in ILs, ΔsolvG°(H+)IL. It can be derived from the consensus value of the free energy of solvation of protons in water if the free energy of transfer of protons from water to the ILs, ΔtG°(H+), is determined. However, the experimental determination of the free energy of transfer of protons relies on extra-thermodynamic hypotheses, as protons cannot be transferred from one solvent to another without a counterion. Here we propose to measure the Hammett acidity functions, which relies on the protonation equilibrium of specific pH-reporters, for the first time by Raman spectroscopy directly in acidic solution of 2,6-dichloro-4-nitroaniline in three 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ILs. We demonstrated that the ΔtG°(H+) obtained by Raman spectroscopy and UV-visible spectroscopy were identical in the same 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. Also, when the butyl substituent is replaced by a longer alkyl chain such as an octyl chain, the acidity in the IL is lowered. The free energies of solvation are calculated in four ILs from Raman spectroscopy data recorded directly in the acidic solutions. These values confirmed that the protons are less solvated in ILs than in water, hence their acidity. Raman spectroscopy also enables determination of the solvation number of the proton in imidazolium-based bis(trifluoromethylsulfonyl)imide ILs. The benefits of implementing Raman spectroscopy to determine the Hammett acidity function in ILs using a non-colored pH-reporter and in colored media are also discussed.

Linear ether-based highly concentrated electrolytes for Li-sulfur batteries.

Li-S batteries have attracted attention as next-generation rechargeable batteries owing to their high theoretical capacity and cost-effectiveness. Sparingly solvating electrolytes hold promise because they suppress the dissolution and shuttling of polysulfide intermediates to increase the coulombic efficiency and extend the cycle life. This study investigated the solubility of polysulfide (Li2S8) in a range of liquid electrolytes, including organic electrolytes, highly concentrated electrolytes, and ionic liquids. The Li2S8 solubility was well correlated with the donor number (DNNMR), estimated via23Na-NMR, and was lower than 100 mM_(elemental sulfur) in electrolytes with DNNMR < 14, regardless of the type of electrolyte. Highly concentrated electrolytes comprising lithium bis(trifluoromethanesulfonyl)amide (LiTFSA) and linear chain dialkyl ethers such as methyl propyl ether (MPE), n-butyl methyl ether (BME), and ethyl propyl ether (EPE) were studied as sparingly solvating electrolytes for Li-S batteries. Monomethyl ethers, such as BME, showed more pronounced Li-ion coordination and higher ionic conductivity, whereas the steric hindrance of the longer alkyl chains in EPE lowered the solvation number, enhanced ion association, and lowered the ionic conductivity despite the solvents having similar dielectric constants. The charge-discharge rate capabilities of Li-S cells with dialkyl ether-based electrolytes were more impressive than those of cells with a localized high-concentration electrolyte using sulfolane (SL) and hydrofluoroether (HFE), [Li(SL)2][TFSA]-2HFE. The higher rate performance was attributed to the superior Li-ion transport properties of the dialkyl ether-based electrolytes. A pouch-type cell using lightweight [Li(BME)3][TFSA] demonstrated an energy density exceeding 300 W h kg-1 under lean electrolyte conditions.

Compular Simulator: Automated Computational Screening of Battery Electrolytes

The vast compositional space and intricate ionic interactions of modern liquid battery electrolytes make the connected R&D very challenging. A comprehensive workflow for reliable computational screening of electrolytes would therefore be highly valuable, which motivated the development of CHAMPION [1-4] and laid the foundation for Compular [5].Within this context, we present Compular Simulator, a new web application automating advanced computational screening of electrolytes, based on molecular dynamics simulations, density functional theory calculations, and machine learning (ML) models. The Simulator can be used in three different modes with increasing degree of sophistication: 1) single system simulation, 2) manual screening, and 3) property optimization by a design of experiments (DoE) methodology.In the single system mode, the user specifies the stoichiometry and thermodynamic state. Simulator then automatically creates a simulation cell with a physically reasonable initial geometry, sets up and runs suitable simulations and CHAMPION analyses on our HPC cloud. Throughout, the user can follow the status of the computations. The results are presented on three levels: a) overall system, b) molecular species, and c) dynamic species. Examples of the former properties are total ionic conductivity, density, electrochemical stability window (ESW), rate of solvation dynamics, conformational entropy, degree of aggregation, and viscosity, while for molecular species, properties including concentration, diffusivity, partial ionic conductivity, ESW, solvation and coordination numbers, average lifetimes, and transference numbers. These are all computed and presented in tables and charts. Finally, dynamic species are structures formed by non-covalent bonds, e.g. solvation shells and ionic aggregates, with the same set of properties as molecular species and presented in the same manner. The tables and graphs can be sorted and filtered w.r.t. properties and constituents and all predictions are given with statistical error bars.Manual screening can be done either by repeatedly creating single systems with varying composition or state, or by creating several systems at once by sweeping a given parameter, such as temperature or a species concentration over a range. Once all systems have been simulated and analyzed as described above, the user can compare the properties of the systems in the screening view. Similarly to the single system view, the screening view consists of three levels: a) overall system properties, shown as a table of systems vs. properties and one chart per property, b) molecular properties, presented as one table per property with systems vs. species and corresponding graphs, and c) dynamic species, similarly displayed. Tables in the screening view can be sorted and filtered similarly to those in the single system view, but in addition, systems can be filtered based on whether they fulfill requirements on their properties, e.g. greater or less than some value, or whether they are on the Pareto front of the target properties.Finally, in the DoE mode, the user specifies: the candidate species, whether any components should be held constant (e.g. fixed solvent composition in a salt screening), if so the total concentration (range) of the candidate species, the state, and the target properties, as well as whether they should be maximized or minimized. The state variables can also optionally be varied within a range. Simulator suggests a batch of systems to run in order to learn as much as possible about the parameter space. Based on the results, it builds a model for how the target properties vary as functions of the input parameters. Simulator then suggests another batch of systems, to add further information where most needed and explore regions near the Pareto front. In addition to the computational predictions, experimental data of target properties can be uploaded and used in the optimization. After each batch, the user is presented with the set of Pareto optimal systems among those sampled, and an assessment of the quality of the current model.While the Compular Simulator web application has hitherto been optimized for liquid electrolytes, we plan to extend it in the future and would love to hear from anyone who has an idea of a different use case. In summary, this is our biggest contribution yet towards fulfilling Compular’s vision of making battery materials R&D digital first.

Tight-Binding Modelling of Deep Eutectic Solvent Based Electrolytes

Deep eutectic solvents (DES) have in recent years gained momentum in the development of new electrolytes for lithium-ion batteries (LiBs)1. Due to their easy creation, tuning possibilities, wide electrochemical stability windows, and low vapor pressures, they are not only able to create safer LiB electrolytes as compared to traditional organic electrolytes, but more importantly, they may enable high voltage LIB cells2. One aspect not yet fully understood is the connection between the symmetry and entropy of the DES local structure and their macroscopic properties. Exploring this connection could assist in rational design of more performant electrolytes, including controlled electrochemical properties, by symmetry and entropy tuning.Herein, we have studied in detail a few simple DES electrolytes created using the hydrogen bond donor N-methyl-acetamide (MAc) combined with each of the three different lithium salts: LiBF4, LiDFOB, and LiBOB, in 1:4 molar ratios – as previously shown advantageous 3. We chose these salts as they exhibit pseudospherical (BF4-), asymmetrical linear (DFOB), and symmetric linear (BOB) anion geometries and thus are plausible to introduce local symmetry differences. Molecular dynamic simulations were run using DFTB+ 4 and the xTB method 5, and as a first level geometrical analysis we look at the (partial) coordination and solvation numbers of the lithium ions.

Molecular interactions in ternary system of K-contin and (2-Aminoacetamido)acetic acid at various temperatures–ultrasonic and viscometric analysis

Ultrasonic techniques are frequently used in organic molecule conformation analysis. Mixtures of ternary liquid complexes are extensively used for comprehending the strength as well as the characteristics of the interactions between molecules. Experimentally, the thermo physical properties of ternary liquid mixtures such as viscosity (η), density (ρ) and velocity (u) of K-contin, (2-Aminoacetamido)acetic acid and non-aqueous medium were determined over temperature ranges of 298.15, 308.15 and 318.15 K. The experimental data were used to ascertain the thermoacoustic parameters such as free volume, internal pressure, adiabatic compressibility, solvation number, specific acoustic impedance and intermolecular free length. These parameters are more useful for predicting and validating molecular interactions.

Solvation number, thermochemical parameter, and viscosity study of sweeteners in aqueous and non-aqueous media through ultrasonic measurements

Solvation number, thermochemical parameter, and viscosity study of sweeteners in aqueous and non-aqueous media through ultrasonic measurements

Tailoring the Self-Assembly of Steviol Glycoside Nanocarriers with Steroidal Amphiphiles.

Bile salts are biosurfactants that can induce structure transformations in supramolecular nanoassemblies with conventional surfactants owing to their unique, planar amphiphilic character and the rigidity of their hydrophobic steroid skeleton. However, structural information about the association of bile salts and amphiphilic glycosides is lacking. In this work, we investigated the micelle structure of two anionic di- and trihydroxy bile salts [sodium deoxycholate (SDC) and sodium cholate (SC)] and a conventional anionic surfactant [sodium dodecyl sulfate (SDS)] in mixtures with a nonionic steviol glycoside [α-glucosyl stevia (Stevia-G)] and studied their potential as a nanocarrier system for two poorly water-soluble drugs (clotrimazole and ketoconazole). Decreased critical micelle concentrations determined from surface tension measurements demonstrate synergistic interactions between Stevia-G and SDS/SDC/SC in a decreasing order. Small-angle X-ray and neutron scattering, interpreted by a core-shell ellipsoid model, indicate that SDS and bile salts act differently on the mixed micelle structure. Compared with SDS/Stevia-G, bile salt/Stevia-G had a core-shell structure more similar to that of pure Stevia-G micelles. SDC and SDS had an increasing and decreasing influence, respectively, on the available molecular surface area in mixtures with Stevia-G on the micelle core but a similar influence on the micelle shell solvation number relative to that of their pure micellar structures. The number of bile salt hydroxyl groups was influential in determining the micelle stoichiometry: an increasing number of hydroxyl groups corresponded to decreasing bile salt aggregation numbers and a smaller hydrophobic micellar core. The core volume was the most important structural factor in explaining the drug solubilization capacity of the nanocarrier systems. Therefore, bile salt-steviol glycoside mixed micellar assemblies exhibit structure control mechanisms allowing the fine-tuning of their interior hydrophobic domains important for nanocarrier applications toward solubilization of poorly water-soluble drugs.

Interactions of ammonium based ionic liquids with DNA in aqueous medium through Volumetric, acoustic and viscometric properties

Ionic liquids (ILs) have emerged as a promising alternative solvent for DNA based studies as most of the studied ILs enhance the stability of DNA and act as a media for extraction and storage. Investigation of IL-DNA interactions through spectroscopic and computational analysis have been carried out earlier and we here attempt to explore the interaction through physicochemical properties of IL-DNA mixture in water medium that provide fundamental knowledge of the solvation behaviour. Properties such as density, ρ, speed of sound, u and viscosity, η, of two ILs, Benzyltributylammonium chloride ([BTBA]Cl) and Tetrabutylammonium bromide ([TBA]Br) in water as well as in aqueous DNA solutions with varying concentrations were measured over a temperature range from 293.15 − 323.15 K and at atmospheric pressure. The derived volumetric properties were calculated to understand the strength and extent of the solute–solvent interactions prevail in the solution. The analysis of partial molar volume at infinite dilution, V2∞, helped in the comparison of the strength of the interactions in between the studied solutes. The second derivative of V2∞ with respect to temperature, (∂2V2∞/∂T2)P facilitated in identifying the influence of the solutes in water structure formation around the solute and it was interesting to note that, although both the ILs behaved similarly in water as structure makers, [TBA]Br showed variation in the presence of DNA by demonstrating water structure breaking effects. Similar results were obtained from the analysis of viscometric properties as well. Further, the capability of the ILs to stay solvated in the DNA aqueous solution was confirmed by the results from the solvation number calculations.

Investigation of molecular interactions of streptomycin sulphate with aqueous L-aspartic acid through volumetric, ultrasonic and viscometric approach

In the present study, physicochemical properties of streptomycin sulphate have been investigated in aqueous and mixed aqueous (0.0099, 0.0199, 0.0300) mol.kg−1 L-aspartic acid media at discrete temperatures (293.15 to 313.15 K) and experimental pressure, P = 101.3 kPa. The empirically measured physical properties such as density, velocity of sound, and viscosity have been utilized for the computation of several parameters such as apparent molar volume (Vϕ), limiting apparent molar volume (Vϕo), hydration number (nH), limiting apparent molar expansivity (Eϕo), apparent molar isentropic compression (Kϕ,s), limiting apparent molar isentropic compression (Kϕ,so), solvation number (Sn), Jones-Dole coefficients, and transfer parameters. Further, the cosphere overlap model has been employed for the acquaintance of varied probable intermolecular interactions operating in the prepared systems. The structure making tendency of the considered solute has been investigated via inference of 2c (Hepler’s constant) data. In addition, UV spectral analysis confirmed the persistence of effective dipole–dipole interactions in the prepared systems of study.

3D Characterization of the Molecular Neighborhood of •OH Radical in High Temperature Water by MD Simulation and Voronoi Polyhedra.

Understanding the properties of the •OH radical in aqueous environments is essential for biochemistry, atmospheric chemistry, and the development of green chemistry technologies. In particular, the technological applications involve knowledge of microsolvation of the •OH radical in high temperature water. In this study, the classical molecular dynamics (MD) simulation and the technique based on the construction of Voronoi polyhedra were used to provide 3D characteristics of the molecular vicinity of the aqueous hydroxyl radical (•OHaq). The statistical distribution functions of metric and topological features of solvation shells represented by the constructed Voronoi polyhedra are reported for several thermodynamic states of water, including the pressurized high-temperature liquid and supercritical fluid. Calculations showed a decisive influence of the water density on the geometrical properties of the •OH solvation shell in the sub- and supercritical region: with the decreasing density, the span and asymmetry of the solvation shell increase. We also showed that the 1D analysis based on the oxygen-oxygen radial distribution functions (RDFs) overestimates the solvation number of •OH and insufficiently reflects the influence of transformations in the hydrogen-bonded network of water on the structure of the solvation shell.

STUDY OF MOLECULAR INTERACTIONS OF SUBSTITUTED 2-OXO-2-H-CHROMENE-3-CARBOHYDRAZIDE DERIVATIVES IN BINARY SOLVENTS USING ULTRASONIC INTERFEROMETER

At 32°C, the apparent molal volume (v), apparent molal compressibility (k), relative association (RA), and solvation number (Sn) of substituted 2-oxo-2-H-chromene-3-carbohydrazide derivatives in 60% DMF-water were measured. The data is used to determine the interaction that is taking place in the solution. The ultrasonic technique is used to determine the interaction of a solute and a solvent. The variation of factors in binary mixtures with different concentrations indicates a significant interaction between solute and solvent molecules, associative molecular interaction, and ion-solvent interaction.

Sodiated Oppolzer Enolates: Solution Structures, Mechanism of Alkylation, and Origin of Stereoselectivity.

NMR spectroscopic studies reveal camphorsultam-derived sodium enolates known as Oppolzer enolates reside as monomers in neat THF and THF/HMPA solutions and as dimers in toluene when solvated by N,N,N',N'-tetramethylethylenediamine (TMEDA) and N,N,N',N'',N''-pentamethyldiethylenediamine (PMDTA). Density functional theory (DFT) computations attest to the solvation numbers. Rate studies show analogy with previously studied lithiated Oppolzer enolates in which alkylation occurs through non-chelated solvent-separated ion pairs. The origins of the selectivity trace to transition structures in which the alkylating agent is guided to the exo face of the camphor owing to stereoelectronic preferences imparted by the sultam sulfonyl moiety. Marked secondary-shell solvation effects are gleaned from the rate studies.