Showing papers in "Liquids in 2022"

Abraham Solvation Parameter Model: Examination of Possible Intramolecular Hydrogen-Bonding Using Calculated Solute Descriptors

Abstract: Published solubility data for 4,5-dihydroxyanthraquinone-2-carboxylic acid dissolved in several organic solvents of varying polarity and hydrogen-bonding character are used to calculate the Abraham model solute descriptors. Calculated descriptor values suggest that 4,5-dihydroxyanthraquinone-2-carboxylic acid engages in intramolecular hydrogen formation between the two phenolic hydrogens and the proton acceptor sites (the lone electron pairs) on the neighboring quinone oxygen atom. Our study further shows that existing group contribution and machine learning methods provide rather poor estimates of the experimental-based solute descriptors of 4,5-dihydroxyanthraquinone-2-carboxylic acid, in part because the estimation methods to not account for the likely intramolecular hydrogen-bonds. The predictive aspect of the Abraham model is illustrated by predicting the solubility of 4,5-dihydroxyanthraquinone-2-carboxylic acid in 28 additional organic mono-solvents for which experimental data does not exist.

Development of Machine Learning Flood Model Using Artificial Neural Network (ANN) at Var River

Abstract: Data-driven flow forecasting models, such as Artificial Neural Networks (ANNs), are increasingly used for operational flood warning systems. In this research, we systematically evaluate different machine learning techniques (random forest and decision tree) and compare them with classical methods of the NAM rainfall run-off model for the Vésubie River, Nice, France. The modeled network is trained and tested using discharge, precipitation, temperature, and evapotranspiration data for about four years (2011–2014). A comparative investigation is executed to assess the performance of the model by using Root Mean Squared Error (RMSE), Mean Absolute Error (MAE), and a correlation coefficient (R). According to the result, Feed Forward Neural Network (FFNN) (a type of ANN) models are less efficient than NAM models. The precision parameters correlation coefficient of ANN is 0.58 and for the NAM model is 0.76 for the validation dataset. In all machine learning models, the decision tree which performed best had a correlation coefficient of 0.99. ANN validation data prediction is good compared to the training, which is the opposite in the NAM model. ANN can be improved by fitting more input variables in the training dataset for a long period.

Aligning Liquid Crystal Materials through Nanoparticles: A Review of Recent Progress

Abstract: Liquid crystals (LCs) have become indispensable materials in everyday life, with their applications ranging from high-resolution television displays to being a part of sophisticated and modern equipment for telecommunications and sensing purposes. Various important features of LC-based devices such as their response time, driving voltage, contrast ratio and brightness are controlled by the uniform alignment of the constituting molecules along the substrate surface. This alignment control can be achieved through various mechanical and non-mechanical techniques. Nanoparticles (NPs), which have become an underbelly of the latest technological developments, can also be incorporated into these tunable materials in order to achieve the desired alignment in them. The present review highlights the advantages of NPs -induced alignment technique over the other contemporary techniques available for aligning LCs. The NPs-induced alignment process is found to be cost-effective and reliable, and it does not require extreme physical conditions such as a low pressure for its operation. This alignment process enables manufacturers to effectively control the pretilt angle of the LC molecules by simply varying the concentration of the doped NPs in the host LC matrix. Furthermore, the alignment behavior in LCs is found to be a function of shape, size, concentration and solubility of the doped NPs in these materials. At the end, this review focuses on the methodology of developing new innovative devices based on this alignment process. With the fabrication of new NPs of different morphologies in recent times, the horizon of the LC nanoscience field is continuously increasing, thus paving way for new devices capitalizing on this alignment technique.

Development of Abraham Model Correlations for Solute Transfer into the tert-Butyl Acetate Mono-Solvent and Updated Equations for Both Ethyl Acetate and Butyl Acetate

Abstract: Experimental solubilities were determined for 31 solid nonelectrolyte organic compounds dissolved in tert-butyl acetate at 298.15 K. Results of the experimental measurements were combined with published mole fraction solubility data for two lipid-lowering medicinal compounds (lovastatin and simvastatin) in order to derive Abraham model expressions for solute transfer into the tert-butyl acetate mono-solvent. The derived correlations provided an accurate mathematical description of the observed experimental data. As part of the current study, previously published Abraham model solvent correlations for both ethyl acetate and butyl acetate were updated using much larger datasets that contained an additional 64 and 35 experimental data points, respectively. The mathematical correlations presented in the current study describe the observed solubility ratios of solutes dissolved in tert-butyl acetate, ethyl acetate, and butyl acetate to within an overall standard deviation of 0.15 log units or less.

Automated Particle Tracing & Sensitivity Analysis for Residence Time in a Saturated Subsurface Media

Abstract: Residence time of water flow is an important factor in subsurface media to determine the fate of environmental toxins and the metabolic rates in the ecotone between the surface stream and groundwater. Both numerical and lab-based experimentation can be used to estimate the residence time. However, due to high variability in material composition in subsurface media, a pragmatic model set up in the laboratory to trace particles is strenuous. Nevertheless, the selection and inclusion of input parameters, execution of the simulation, and generation of results as well as post-processing of the outcomes of a simulation take a considerable amount of time. To address these challenges, an automated particle tracing method is developed where the numerical model, i.e., flow and reactive transport code, MIN3P, and MATLAB code for tracing particles in saturated porous media, is used. A rectangular model domain is set up considering a fully saturated subsurface media under steady-state conditions in MIN3P. Streamlines and residence times of the particles are computed with a variety of seeding locations covering the whole model surface. Sensitivity analysis for residence time is performed over the varying spatial discretization and computational time steps. Moreover, a comparative study of the outcomes with Paraview is undertaken to validate the automated model (R2 = 0.997). The outcome of the automated process illustrates that the computed residence times are highly dependent on the accuracy of the integration method, the value of the computational time step, ∆t, spatial discretization, stopping criterion for the integration process of streamlines, location, and amount of seed points. The automated process can be highly beneficial in obtaining insights into subsurface flow dynamics with high variability in the model setup instead of laboratory-based experimentation in a computationally efficient manner.

Structures of Hydrated Metal Ions in Solid State and Aqueous Solution

Abstract: This review article summarizes the reported crystallographically determined structures of compounds containing a hydrated metal ion and the reported structures of hydrated metal ions in aqueous solution. A short overview of the methods available to study structures of metal complexes in solution is given.

Techno-Economic Analysis of Atmospheric Water Generation by Hybrid Nanofluids to Mitigate Global Water Scarcity

Abstract: Globally, multiple efforts are being made to develop active atmospheric water generation (AWG) or atmospheric water extraction (AWE) systems, particularly using direct air-cooling technology to produce water from ambient air. However, this legacy technique is highly energy-intensive; it can only be operated when the local dew point is above the freezing point of water, and does not scale to create enough water to offer solutions for most industries, services, or agriculture. Liquid-desiccant-based AWG methods show promising performance advantages, and offer a versatile approach to help address the thermodynamics, health risks, and geographic constraints currently encountered by conventional active AWG systems. In this study, we performed a techno-economic analysis of a liquid-desiccant-based AWG system with a continuous operating style. An energy balance was performed on a single design point of the AWG system configuration while using a LiCl liquid desiccant loaded with multiwalled carbon nanotubes (MWCNTs). We showed that the MWCNTs can be doped in LiCl for effective heat transfer during water desorption, resulting in lowering of the sensible heat load by ≈49% on the AWG system. We demonstrated that the specific energy consumption (SEC) can currently be obtained as low as 0.67 kWh per US gallon, while changing the inlet desiccant stream concentration of MWCNT-doped LiCl under the given conditions. While the production cost of water (COW) showed a significant regional dependency, economic analysis revealed that water can be produced at a minimum selling price of USD 0.085 per US gallon, based on the 2021 annual average wholesale electricity cost of USD 0.125 per kWh in the U.S.A., thereby providing a strong foundation for future research to meet desirable and competitive water costs by 2026, but before 2031.

Abraham Solvation Parameter Model: Calculation of L Solute Descriptors for Large C11 to C42 Methylated Alkanes from Measured Gas–Liquid Chromatographic Retention Data

Abstract: Abraham model L solute descriptors have been determined for 149 additional C11 to C42 monomethylated and polymethylated alkanes based on published Kovat’s retention indices based upon gas–liquid chromatographic measurements. The calculated solute descriptors, in combination with previously published Abraham model correlations, can be used to predict a number of very important chemical and thermodynamic properties including partition coefficients, molar solubility ratios, gas–liquid chromatographic and HPLC retention data, infinite dilution activity coefficients, molar enthalpies of solvation, standard molar vaporization and sublimation at 298 K, vapor pressures, and limiting diffusion coefficients. The predictive computations are illustrated by estimating both the standard molar enthalpies of sublimation and the enthalpies of solvation in benzene for the monomethylated and polymethylated alkanes considered in the current study.

Experimental and Computational Study of the Properties of Imidazole Compounds with Branched and Cycloalkyl Substituents

Abstract: N-functionalized imidazole compounds with linear alkyl groups have been widely utilized precursors for imidazolium ionic liquids (ILs) while the effects of branched and cycloalkyl substituents on properties of imidazole compounds have not been studied; however, such compounds are just as synthetically accessible as those with linear alkyl groups. In this work, two fundamental properties, density and viscosity, of selected N-functionalized imidazoles bearing iso-propyl, iso-butyl, sec-butyl methylcyclopropyl, cyclopentyl, and methylcyclohexyl groups have been measured in the temperature range of 293.15–353.15 K for the guidance of molecular design for future applications. A linear and parabolic model were used for temperature-density correlation while temperature dependence of viscosity was summarized using the Andrade Equation and the Vogel-Fulcher-Tammann equation. In addition to experimental data, density, viscosity, vapor pressure and vaporization of enthalpies of target imidazole compounds were predicted using COSMOtherm calculations and compared with experimental data. It was found that the calculated densities were quite close to the experimental data, while viscosity data, obtained from COSMOtherm, underestimated experimental measurements and a scaling factor provided agreement with experiments. Predictions of vapor pressure were relatively reliable at low temperature, although the difference between experiment and prediction tended to expand with increasing temperature. Variances of vaporization enthalpies were small upon temperature change and a maximum error of ~12.3% was observed for all compounds studied.

Revision and Extension of a Generally Applicable Group Additivity Method for the Calculation of the Refractivity and Polarizability of Organic Molecules at 298.15 K

Abstract: In a continuation and extension of an earlier publication, the calculation of the refractivity and polarizability of organic molecules at standard conditions is presented, applying a commonly applicable computer algorithm based on an atom group additivity method, where the molecules are broken down into their constituting atoms, these again being further characterized by their immediate neighbor atoms. The calculation of their group contributions, carried out by means of a fast Gauss–Seidel fitting calculus, used the experimental data of 5988 molecules from literature. An immediate subsequent ten-fold cross-validation test confirmed the extraordinary accuracy of the prediction of the molar refractivity, indicated by a correlation coefficient R2 and a cross-validated analog Q2 of 0.9997, a standard deviation σ of 0.38, a cross-validated analog S of 0.41, and a mean absolute deviation of 0.76%. The high reliability of the predictions was exemplified with three classes of molecules: ionic liquids and silicon- and boron-containing compounds. The corresponding molecular polarizabilities were calculated indirectly from the refractivity using the inverse Lorentz–Lorenz relation. In addition, it could be shown that there is a close relationship between the “true” volume and the refractivity of a molecule, revealing an excellent correlation coefficient R2 of 0.9645 and a mean absolute deviation of 7.53%.

Application of Reichardt’s Solvent Polarity Scale (ET(30)) in the Selection of Bonding Agents for Composite Solid Rocket Propellants

Abstract: Bonding agents (BA) are key compounding ingredients for the correct formulation of composite solid rocket propellants (CSRP). In particular, the addition of BA is essential to achieve suitable mechanical properties of CSRP in terms of adequate tensile strength and elongation at the break. It is shown that the polarity of each conventional BA as well as new potential BA can be measured through the Reichardt’s ET(30) polarity scale. Using this methodology, it was possible to propose a substitute for MAPO (tris-(methylaziridinyl)-phosphine oxide), a conventional BA with the drawback of high toxicity and high reactivity, with TTPT (tris-(pyrrolidine)-phosphine oxide), a completely safe and effective BA. In this work, several other potential BA were evaluated through the Reichardt’s ET(30) polarity scale but only a selection of the potential BA were effectively tested in a standard CSRP. The evaluation of TTPT vs. MAPO showing the ability of the former BA to match the mechanical properties of the latter BA was particularly interesting. A reasonable correlation between the elongation at break of the CSRP and the ET(30) value of the BA used in the compound was found.

Hydrolysis of Al3+ in Aqueous Solutions: Experiments and Ab Initio Simulations

Abstract: An experimental and computational study on the hydrolysis of Al3+ in aqueous solutions is here reported. Speciation model and formation constants were determined by potentiometric titrations at T = 298.15 K, 0.1 ≤ I/mol L−1 ≤ 1 in aqueous NaCl, NaNO3, NaCl/NaNO3 solutions. The dependence of formation constants on ionic strength is reported in all the ionic media over the range of 0.1–1.0 mol L−1. Under the studied experimental conditions, the formation of Al3(OH)45+ and Al13(OH)327+ species is observed in all the investigated ionic media and ionic strengths. The formation constants of the species formed by Al3+ with Cl− were determined together with the dependence on the ionic strength. Moreover, with the aim of unveiling the molecular structure of the formed Al complexes, quantum-mechanical calculations and state-of-the-art ab initio molecular dynamics simulations under explicit solvation were executed. These computations show, for the first time, the highly cooperative role played by the surrounding water molecules in neutralising mononuclear systems–such as AlCl2+ and AlClOH+–and the hydrolytic polynuclear system, Al3(OH)45+.

Thermodynamic Analysis of the Solubility of Sulfadiazine in (Acetonitrile 1-Propanol) Cosolvent Mixtures from 278.15 K to 318.15 K

Abstract: Drug solubility is one of the most significant physicochemical properties as it is related to drug design, formulation, quantification, recrystallization, and other processes, so understanding it is crucial for the pharmaceutical industry. In this context, this research presents the thermodynamic analysis of the solubility of sulfadiazine (SD) in cosolvent mixtures {acetonitrile + 1-propanol} at 9 temperatures (278.15 K–318.15 K), which is a widely used drug in veterinary therapy, and two solvents of high relevance in the pharmaceutical industry, respectively. The solubility of SD, in cosolvent mixtures {acetonitrile + 1-propanol} is an endothermic process where the maximum solubility was reached in pure acetonitrile at 318.15 K and the minimum in 1-propanol at 278.15 K. Although the solubility parameters of acetonitrile and propanol were similar, the addition of acetonitrile to the cosolvent mixture leads to a positive cosolvent effect on the solubility of DS. As for the thermodynamic functions of the solution, the process is strongly influenced by enthalpy, and according to the enthalpy–entropy compensation analysis, the process is enthalpy-driven in intermediate to rich mixtures in 1-propanol and entropy-driven in mixtures rich in acetonitrile.

Isomorph Invariance in the Liquid and Plastic-Crystal Phases of Asymmetric-Dumbbell Models

Abstract: We present a numerical study of the asymmetric dumbbell model consisting of “molecules” constructed as two different-sized Lennard-Jones spheres connected by a rigid bond. In terms of the largest (A) particle radius, we report data for the structure and dynamics of the liquid phase for the bond lengths 0.05, 0.1, 0.2, and 0.5, and analogous data for the plastic-crystal phase for the bond lengths 0.05, 0.1, 0.2, and 0.3. Structure is probed by means of the AA, AB, and BB radial distribution functions. Dynamics is probed via the A and B particle mean-square displacement as functions of time and via the rotational time-autocorrelation function. Consistent with the systems’ strong virial potential-energy correlations, the structure and dynamics are found to be isomorph invariant to a good approximation in reduced units, while they generally vary considerably along isotherms of the same (20%) density variation. Even the rotational time-autocorrelation function, which due to the constant bond length is not predicted to be isomorph invariant, varies more along isotherms than along isomorphs. Our findings provide the first validation of isomorph-theory predictions for plastic crystals for which isomorph invariance, in fact, is found to apply better than in the liquid phase of asymmetric-dumbbell models.

Correlation of Surface Tension of Mono-Solvents at Various Temperatures

Abstract: Surface tension is among the most important factors in chemical and pharmaceutical processes. Modeling the surface tension of solvents at different temperatures helps to optimize the type of solvent and temperature. The surface tension of solvents at different temperatures with their solvation parameters was used in this study to develop a model based on the van’t Hoff equation by multiple linear regression. Abraham solvation parameters, Hansen solubility parameters, and Catalan parameters are among the most discriminating descriptors. The overall MPD of the model was 3.48%, with a minimum and maximum MPD of 0.04% and 11.62%, respectively. The model proposed in this study could be useful for predicting the surface tension of mono-solvents at different temperatures.

Solute-Induced Perturbation of the Solvent Microstructure in Aqueous Electrolyte Solutions: Some Uses and Misuses of Structure Making/Breaking Criteria

Abstract: In this article, we raise awareness about the misuses of frequently invoked criteria for structure making/breaking phenomena, resulting from the absence of any explicit cause–effect relationship between the proposed markers and the microstructural perturbation of the solvent induced by the solute. First, we support our assessment with rigorous molecular-based foundations to determine, directly and quantitatively, the solute-induced perturbation of the solvent structure leading to an unambiguous definition of a structure making/breaking event. Then, we highlight and discuss the sources of concealed ambiguities in two of the most frequently invoked structure making/breaking criteria, i.e., Hepler’s thermal expansivity-based and Jones–Dole’s B coefficient-based markers. Finally, we illustrate how the implementation of rigorous molecular-based arguments, in conjunction with the available experimental evidence on a variety of aqueous species at infinite dilution, rule out the validity of these two criteria as structure making/breaking markers and suggest their discontinuation to avoid the perpetuation of myths.

Solvent and H/D Isotopic Substitution Effects on the Krichevskii Parameter of Solutes: A Novel Approach to Their Accurate Determination

Abstract: We establish a direct route for the accurate determination of the solvent effect on the Krichevskii parameter of a solute, based solely on the contrasting solvation behavior of the solute in the desired solvent relative to that of the reference solvent, i.e., in terms of the distinct solvation Gibbs free energies of the solute and the corresponding Krichevskii parameters of an ideal gas solute in the pair of solvents. First, we illustrate the proposed approach in the determination of the H/D−solvent effect on the Krichevskii parameter of gaseous solutes in aqueous solutions, when the solvents are different isotopic forms (isotopomers) of water, and then, by generalizing the approach to any pair of solvents. For that purpose, we (a) identify the links between the standard solvation Gibbs free energy of the i−solute in the two involved solvent environments and the resulting Krichevskii parameters, (b) discuss the fundamentally based linear behavior between the Krichevskii parameter and the standard solvation Gibbs free energy of the i−solute in an α−solvent, and interpret two emblematic cases of solutions involving either an ideal gas solute or an i−solute behaving identically as the solvating species, as well as (c) provide a novel microstructural interpretation of the solvent effect on the Krichevskii parameter according to a rigorous characterization of the critical solvation as described by a finite unambiguous structure making/breaking parameter Siα∞(SR) of the i−solute in the pair of α−solvents.

Liquid-State Volumetric Properties of a Set of Alcohols with Up to Five Carbon Atoms

Abstract: This work provides density data (~1300 values) of 14 alcohols with up to five carbon atoms at p ∈ [0.1–40] MPa and T ∈ [278–358] K. The information obtained is modeled with a convenient reformulation of the Tait equation from which the volumetric coefficients, α and β, are derived both analytically and numerically. The general EoS containing α and β is also used for checking the consistency of the hypothesis on the invariability of the cited thermophysic parameters. The results obtained can be considered reliable because of the low estimated errors between the experimental data and those of the literature, which are below 0.4% for volume, while for the volumetric coefficients there is always a reference diverging 10%, or less, from the proposed model estimations. By including the averages of α and β into the general state of equation the errors increase, being <15%, compared to those based on the Tait equation. Hence, the assumption on the stability of the volumetric coefficients in this working interval is sufficient to make rough estimations of the molar volume of the selected alcohols.

Estimating Equivalent Alkane Carbon Number Using Abraham Solute Parameters

Abstract: The use of equivalent alkane carbon numbers (EACN) to characterize oils is important in surfactant-oil-water (SOW) systems. However, the measurement of EACN values is non-trivial and thus it becomes desirable to predict EACN values from structure. In this work, we present a simple linear model that can be used to estimate the EACN value of oils with known Abraham solute parameters. We used linear regression with leave-one-out cross validation on a dataset of N = 80 oils with known Abraham solute parameters to derive a general model that can reliably estimate EACN values based upon the Abraham solute parameters: E (the measured liquid or gas molar refraction at 20 °C minus that of a hypothetical alkane of identical volume), S (dipolarity/polarizability), A (hydrogen bond acidity), B (hydrogen bond basicity), and V (McGowan characteristic volume) with good accuracy within the chemical space studied (N = 80, R2 = 0.92, RMSE = 1.16, MAE = 0.90, p < 2.2 × 10−16). These parameters are consistent with those in other models found in the literature and are available for a wide range of compounds.

Solvent Exchange around Aqueous Zn(II) from Ab Initio Molecular Dynamics Simulations

Abstract: Hydrated zinc(II) cations, due to their importance in biological systems, are the subject of ongoing research concerning their hydration shell structure and dynamics. Here, ab initio molecular dynamics (AIMD) simulations are used to study solvent exchange events around aqueous Zn2+, for which observation in detail is possible owing to the considerable length of the generated trajectory. While the hexacoordinated Zn(H2O)62+ is the dominant form of Zn(II) in an aqueous solution, there is a non-negligible contribution of the pentacoordinated Zn(H2O)52+ complex which presence is linked to the dissociative solvent exchange events around Zn2+. The pentacoordinated Zn(II) has a much tighter hydration sphere and is characterized by a trigonal bipyramidal structure, in contrast to the usual octahedral symmetry of the hexacoordinated complex. In total, two full exchange events are registered in the analyzed trajectory. AIMD simulations on an adequate length scale thus provide a direct way of studying such solvent exchange events around ions in molecular detail.

An Ab Initio Investigation of the Hydration of Lead(II)

Abstract: The structure of lead(II) is not well known in aqueous solution. The Hartree–Fock and second order Møller–Plesset levels of theory using the CEP, LANL2, and SDD effective core potentials in combination with their associated basis sets, or with the 6-31G* and 6-31+G* basis sets were used to calculate the energies, structures, and vibrational frequencies of Pb2+(H2O)n, n = 0–9, 18. The lead–oxygen distances and totally symmetric stretching frequency of the aqualead(II) ions from different levels of theory were compared with each other, and with solution measurements where available. The calculations support a hemidirected hexacoordinate structure.

Increasing the Equilibrium Solubility of Meloxicam in Aqueous Media by Using Dimethyl Sulfoxide as a Cosolvent: Correlation, Dissolution Thermodynamics and Preferential Solvation

Abstract: Meloxicam is widely prescribed as an analgesic and anti-inflammatory drug in human therapeutics. Owing the very low aqueous solubility of meloxicam, this property has been studied in dimethyl sulfoxide (DMSO)-aqueous solvent systems at several temperatures from 273.15 to 313.15 K to expand the solubility database about analgesic drugs in mixed solvents. The flask shake method followed by ultraviolet-visible (UV-vis) spectrophotometry analysis were used for meloxicam solubility determinations. A number of cosolvency models, including the Jouyban–Acree model, were challenged for solubility correlation/prediction of this drug in these mixtures. The van’t Hoff and Gibbs equations were employed to calculate the apparent standard thermodynamic quantities relative to dissolution and mixing processes. The inverse Kirkwood–Buff integral method was employed for calculating the preferential solvation parameters of meloxicam by DMSO in the mixtures. Meloxicam solubility increases with increasing temperature and maximum solubilities are observed in neat DMSO at all temperatures studied. Dissolution processes were endothermic in all cases and entropy-driven in the composition interval of 0.40 ≤ x1 ≤ 1.00. A nonlinear enthalpy–entropy relationship was observed in the plot of enthalpy vs. Gibbs energy for drug transfer processes. Meloxicam is preferentially solvated by water in water-rich mixtures but preferentially solvated by DMSO in the composition interval of 0.21 < x1 < 1.00.

Using Two Group-Contribution Methods to Calculate Properties of Liquid Compounds Involved in the Cyclohexanone Production Operations

Abstract: A numerical application has been carried out to determine the thermophysical properties of more than fifty pure liquid compounds involved in the production process of cyclohexanone, whose real values are unknown, in many cases. Two group-contribution methods, the Joback and the Marrero–Gani methods, both used in the fields of physicochemistry and engineering, are employed. Both methods were implemented to evaluate critical properties, phase transition properties, and others, which are required for their use in industrial process simulation/design. The quality of the estimates is evaluated by comparing them with those from the literature, where available. In general, both models provide acceptable predictions, although each of them shows improvement for some of the properties considered, recommending their use, when required.

Stability of Detonation Nanodiamond Colloid with Respect to Inorganic Electrolytes and Anionic Surfactants and Solvation of the Particles Surface in DMSO–H2O Organo-Hydrosols

Abstract: In this article, the stability of sols of detonated nanodiamonds, DND, with positively charged colloidal particles, is studied in different salt solutions in water–dimethyl sulfoxide (DMSO) binary systems containing 95 vol.% organic solvent. Additionally, several CCC values are determined in 95 vol.% acetonitrile for comparison. The critical coagulation concentrations (CCC) are determined using the dynamic light scattering technique and the Fuchs function. As coagulators, NaCl, NaBr, NaNO3, NaClO4, Nan-C8H17SO3, and Nan-C12H25OSO3 are used. Comparison of the CCC values in DMSO–H2O and CH3CN–H2O with those obtained in water allows us to make some conclusions. The variations of these values in different solvents are explained in terms of good and poor interfacial solvation of colloidal particles, “structural” contribution to the interparticle interaction energy, lyotropic series for anions, and more or less pronounced adsorption of surfactants. The study of the stability of DND hydrosol in solutions of anionic surfactants with different hydrocarbon tail length demonstrated the crucial role of adsorption in the coagulation process.

The Solubility of Ethyl Candesartan in Mono Solvents and Investigation of Intermolecular Interactions

Abstract: In this work, the experimental solubility of ethyl candesartan in the selected solvents within the temperature ranging from 278.15 to 318.15 K was studied. It can be easily found that the solubility of ethyl candesartan increases with the rising temperature in all solvents. The maximum solubility value was obtained in N,N-dimethylformamide (DMF, 7.91 × 10−2), followed by cyclohexanone (2.810 × 10−2), 1,4-dioxanone (2.69 × 10−2), acetone (7.04 × 10−3), ethyl acetate (4.20 × 10−3), n-propanol (3.69 × 10−3), isobutanol (3.38 × 10−3), methanol (3.17 × 10−3), n-butanol (3.03 × 10−3), ethanol (2.83 × 10−3), isopropanol (2.69 × 10−3), and acetonitrile (1.15 × 10−2) at the temperature of 318.15 K. Similar results of solubility sequence from large to small were also obtained in other temperatures. The X-ray diffraction analysis illustrates that the crystalline forms of all samples were consistent, and no crystalline transformation occurred during the dissolution process. In aprotic solvents, except for individual solvents, the solubility data decreases with the decreasing values of hydrogen bond basicity (β) and dipolarity/polarizability (π*). The largest average relative deviation (ARD) data in the modified Apelblat equation is 1.9% and observed in isopropanol; the maximum data in λh equation is 4.3% and found in n-butanol. The results of statistical analysis show that the modified Apelblat equation is the more suitable correlation of experimental data for ethyl candesartan in selected mono solvents at all investigated temperatures. In addition, different parameters were used to quantify the solute–solvent interactions that occurred in the dissolution process including Abraham solvation parameters (APi), Hansen solubility parameters (HPi), and Catalan parameters (CPi).

An Ab Initio Investigation of the Hydration of Tin(II)

Abstract: The structure of tin(II) is not well known in aqueous solution. The energies, structures, and vibrational frequencies of [Sn(H2O)n,]2+ n = 0–9, 18 have been calculated at the Hartree–Fock and second order Møller–Plesset levels of theory using the CEP, LANL2, and SDD effective core potentials in combination with their associated basis sets, or with the 6-31G* and 6-31+G* basis sets. The tin–oxygen distances and totally symmetric stretching frequency of the aquatin(II) ions were compared with each other, and with solution measurements where available.

Density and Refractive Index of Binary Ionic Liquid Mixtures with Common Cations/Anions, along with ANFIS Modelling

Abstract: Ionic liquids have many interesting properties as they share the properties of molten salts as well as organic liquids, such as low volatility, thermal stability, electrical conductivity, non-flammability, and much more. Ionic liquids are known to be good solvents for many polar and nonpolar solutes. Combined with their special properties, ionic liquids are good replacements for the conventional toxic and volatile organic solvents. Each ionic liquid has different properties than others. In order to alter, tune, and enhance the properties of ionic liquids, sometimes, it is necessary to mix different ionic liquids to achieve the desired properties. However, using mixtures of ionic liquids in chemical processes requires reliable estimations of the mixtures’ physical properties such as refractive index and density. The ionic liquids used in this work are 1-butyl-3-methylimidazolium thiocyanate ([BMIM][SCN]), 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]), 1-hexyl-3-methylimidazolium tetrafluoroborate ([HMIM][BF4]), and 1-hexyl-3-methylimidazolium hexafluorophosphate ([HMIM][PF6]). These ionic liquids were supplied by Io-li-tec and used as received. However, new measurements for the density and refractive index were taken for the pure ionic liquids to be used as reference. In the present work, the densities and refractive indices of four different binary mixtures of ionic liquids with common cations and/or anions have been measured at various compositions and room conditions. The accuracy of different empirical mixing rules for calculation of the mixtures refractive indices was also studied. It was found that the overall absolute average percentage deviation from the ideal solution in the calculation of the molar volume of the examined binary mixtures was 0.78%. Furthermore, all of the examined mixing rules for the calculation of the refractive indices of the mixtures were found to be accurate. However, the most accurate empirical formula was found to be Heller’s relation, with an average percentage error of 0.24%. Furthermore, an artificial intelligence model, an adaptive neuro-fuzzy inference system (ANFIS), was developed to predict the density and refractive index of the different mixtures studied in this work as well as the published literature data. The predictions of the developed model were analyzed by various methods including both statistical and graphical approaches. The obtained results show that the developed model accurately predicts the density and refractive index with overall R2, RMSE, and AARD% values of 0.968, 7.274, 0.368% and 0.948, 7.32 × 10−3 and 0.319%, respectively, for the external validation dataset. Finally, a variance-based global sensitivity analysis was formed using extended the Fourier amplitude sensitivity test (EFAST). Our modelling showed that the ANFIS model outperforms the best available empirical models in the literature for predicting the refractive index of the different mixtures of ionic liquids.

Vibrational Raman Spectroscopy of the Hydration Shell of Ions

Abstract: Ionic perturbation of water has important implications in various chemical, biological and environmental processes. Previous studies revealed the structural and dynamical perturbation of water in the presence of ions, mainly with concentrated electrolyte solutions having significant interionic interactions. These investigations highlighted the need of selective extraction of the hydration shell water from a dilute electrolyte solution that is largely free from interionic interactions. Double-difference infrared (DDIR) and Raman multivariate curve resolution (Raman-MCR), as well as MD simulation, provided valuable insight in this direction, suggesting that the perturbed water mainly resides in the immediate vicinity of the ion, called the hydration shell. Recently, we have introduced Raman difference spectroscopy with simultaneous curve fitting (Raman-DS-SCF) analysis that can quantitatively extract the vibrational response of the perturbed water pertaining to the hydration shell of fully hydrated ions/solute. The DS-SCF analysis revealed novel hydrogen-bond (H-bond) structural features of hydration water, such as the existence of extremely weakly interacting water–OH (νmax ~ 3600 cm−1) in the hydration shell of high-charge-density metal ions (Mg2+, Dy3+). In addition, Raman-DS-SCF retrieves the vibrational response of the shared water in the water–shared-ion pair (WSIP), which is different from the hydration shell water of either the interacting cation and anion. Herein, we discuss the perturbation of water H-bonding in the immediate vicinity of cation, anion, zwitterion and hydrophobes and also the inter-ionic interactions, with a focus on the recent results from our laboratory using Raman-DS-SCF spectroscopy.

Solvation Structure and Ion–Solvent Hydrogen Bonding of Hydrated Fluoride, Chloride and Bromide—A Comparative QM/MM MD Simulation Study

Abstract: In this study, the correlated resolution-of-identity Møller–Plesset perturbation theory of second order (RIMP2) ab initio level of theory has been combined with the newly parameterised, flexible SPC-mTR2 water model to formulate an advanced QM/MM MD simulation protocol to study the solvation properties of the solutes F−, Cl− and Br− in aqueous solution. After the identification of suitable ion–water Lennard–Jones parameters for the QM/MM coupling, a total simulation period of 10 ps (equilibration) plus 25 ps (sampling) could be achieved for each target system at QM/MM conditions. The resulting simulation data enable an in-depth analysis of the respective hydration structure, the first shell ligand exchange characteristics and the impact of solute–solvent hydrogen bonding on the structural properties of first shell water molecules. While a rather unexpected tailing of the first shell ion–oxygen peak renders the identification of a suitable QM boundary region challenging, the presented simulation results provide a valuable primer for more advanced simulation approaches focused on the determination of single-ion thermodynamical properties.

Application of Solution Calorimetry to Determining the Fusion Enthalpy of an Arylaliphatic Compound at 298.15 K: n-Octadecanophenone

Abstract: Evaluating the temperature dependence of the fusion enthalpy is no trivial task, as any compound melts at a unique temperature. At the same time, knowledge of the fusion enthalpies under some common conditions, particularly at the reference temperature of 298.15 K, would substantially facilitate the comparative analysis and development of the predictive schemes. In this work, we continue our investigations of the temperature dependence of the fusion enthalpy of organic non-electrolytes using solution calorimetry. As an object of study, n-octadecanophenone, an arylaliphatic compound was chosen. The solvent appropriate for evaluating the fusion enthalpy at 298.15 K from the solution enthalpy of crystal was selected: p-xylene. The heat capacity and fusion enthalpy at the melting temperature were measured by differential scanning calorimetry to derive the fusion enthalpy at 298.15 K from the Kirchhoff’s law of Thermochemistry. An agreement between the independently determined values was demonstrated. This particular result opens a perspective for further studies of the fusion thermochemistry of arylaliphatic compounds at 298.15 K by solution calorimetry.