Partial Molar Volume Of Solute Research Articles

Analysis of the solution structure parameter α in the relationship between the molar fraction and the freezing points, and hydration parameter h determined from viscosity and density measurements, for sugar alcohols and related sugars in water.

The parameter α was obtained from the molar fraction of solute and the freezing points of sugar alcohols and their related sugars in water. For comparison with this parameter, simple measurement of the hydration parameter h was performed using a capillary viscometer and a density meter. This parameter was calculated from the viscosity B coefficient and the partial molar volume of solute. The viscosity B coefficient was more suitable than the partial molar volume for h calculation, as indicated by the determination coefficients of the linear regression lines. h correlated well with α for various compounds, including sugar alcohols in water, supporting the parameters' theoretical correspondence (α =-h). In addition, the activation energy required for hydration implies that the thermal stability increases with the saccharide molecular weight.

Investigations of solute–solvent interactions in aqueous solutions of amino acids ionic liquids having the common nitrate as anion at different temperatures

Amino acids ionic liquids (AAILs) have huge potential applications in the green chemistry, as these are synthesized from the naturally occurring 20 amino acids and having strong hydrogen bonding ability, hydrophobic tuning, biodegradability, low-toxicity. These specialities are useful for the solubilization and stabilization of biomolecules in aqueous solutions and biofluids. We realize that the buffering capacity of such ionic salts in biofluids may cause some–sort of control in biological processes. It is expected that similar to carbonate–bicarbonate equilibria, the interaction of amino acids may be contributing to ionic interactions. In the present work, we report the synthesis of amino acids–based nitrate protic ionic liquids involving an infrequently used cations amino acids such as glycine ([HOOC–CH2–NH3]+) and ւ–alanine ([HOOC–(CH3)CH–NH3]+) with common inorganic planner anion as nitrate ([NO3]−). To understand the ionic and molecular interactions between the new class of solvents so called “bio–ionic liquids” such as glycine nitrate ([HOOC–CH2–NH3]+ [NO3]−) and ւ–alanine nitrate ([HOOC–(CH3)CH–NH3]+ [NO3]−) in aqueous solutions, the density property has been measured in the concentration range of 0.01974–0.52080 mol·kg−1 at different temperatures (288.15–308.15 K in steps of 5 K) and at 0.1 MPa. Further, experimental density data were used to calculate the apparent molar volume (Vϕ) of solute, partial molar volume of solute (V¯2) and partial molar volume of solvent (V¯1) as a function of concentration at 288.15–308.15 K. Using the appropriate thermodynamic equations incorporating the corrections due to Debye–Hückel limiting law, the apparent molar volume of solute at infinite dilution (Vϕ0) at all studied temperatures has been calculated along with the deviation parameters. The isobaric expansivity coefficient (α) and apparent molar expansivity (Eϕ) of solute at finite concentrations as well as limiting apparent molar expansivity (Eϕ0) of solute are also obtained at 293.15, 298.15 and 303.15 K. The results have been discussed to obtain information about the ion–solvent and ion–ion interactions along with influence of hydrophobic group on the volumetric properties.

Peptides in aqueous protic ionic liquid solutions: Apparent and transfer volumes at 298.15 K and at 0.1 MPa

The densities of glycine based peptides namely glycyl-glycine (digly), glycine-ւ-valine (gly-val), glycyl-ւ-leucine (gly-leu) and glycyl-glycyl-glycine (triglycine/trigly) in aqueous solutions containing ~0.20 mol·kg−1 of triethylammonium acetate [TEAA], triethylammonium glycolate [TEAG], triethylammonium pyruvate [TEAPy] and triethylammonium propionate [TEAP] protic ionic liquids (PILs) are reported at 298.15 K and at atmospheric pressure. Experimental density data obtained for these systems were used to estimate apparent molar volume (ϕV), the limiting apparent molar volume (ϕV0), partial molar volume of solute (V¯2) and partial molar volume of mixed solvent (PILs + water) (V¯1). The change in limiting apparent molar volume due to transfer (ΔtrϕV0) of peptides from water to aqueous ionic liquid solutions were also estimated. The outcomes obtained from all these thermodynamic parameters were discussed in terms of ion–peptide interactions, ion–ion interactions, hydrophobic solvation, peptide group contributions to limiting volumes, etc.

Excess volumes and partial molar volumes of binary liquid mixtures of furfural or 2–methylfuran with alcohols at 298.15 K

In this work, densities, excess molar volumes, partial molar volumes and excess partial molar volumes for binary liquid mixtures of furfural and 2–methylfuran with 1–propanol or 2–propanol or 2–butanol or 1–pentanol or 2–pentanol or 1–hexanol at 298.15 K and 0.1 MPa over the entire range of composition were determined. Excess molar volumes were correlated with Redlich–Kister equation with average absolute deviations smaller than 0.0164. Excess molar volumes were negative for furfural + 1–propanol or 2–propanol and positive for all other studied binary systems. Solute partial molar volumes determined increase as alcohol carbon chain length increase, except for furfural + 2–pentanol, which presented smaller values than 2–butanol for molar fractions below 0.2. A maximum/minimum was observed from the excess partial molar volume plots. FTIR spectra data indicate bands at 3135 cm−1, for furfural systems, and 3122 cm−1 for 2–methylfuran systems, are related to the behavior found for excess molar volumes and that H–bonds are smaller for furfural systems than for 2–methylfuran.

Connections between the Anomalous Volumetric Properties of Alcohols in Aqueous Solution and the Volume of Hydrophobic Association.

The partial molar volumes of alcohols in water exhibit a non-monotonic dependence on concentration at room temperature, initially decreasing with increasing concentration before passing through a minimum and rising to the pure liquid plateau. This anomalous behavior is associated with hydrophobic interactions. We report molecular simulations of short chain alcohols and alkanes in water to examine the volumetric properties of these mixtures at infinite dilution over a range of temperatures. Our simulations find this anomaly disappears at a crossover temperature, above which the solute volume only varies monotonically with concentration. A Voronoi volume analysis of solution configurations finds that solutes in clusters take up less space than individual solutes at low temperature and more space at elevated temperatures. These changes in cluster volumes are subsequently shown to correlate with the derivative of the solute partial molar volume with respect to solute concentration. The changes in solute volume upon nonpolar solute association impact the response of molecular-scale hydrophobic interactions for assembly with increasing pressure.

Challenges in the Structure Determination of Self-Assembled Metallacages: What Do Cage Cavities Contain, Internal Vapor Bubbles or Solvent and/or Counterions?

Proving the structures of charged metallacages obtained by metal ion coordination-driven solution self-assembly is challenging, and the common use of routine NMR spectroscopy and mass spectrometry is unreliable. Carefully determined diffusion coefficients from diffusion-ordered proton magnetic resonance (DOSY NMR) for six cages of widely differing sizes lead us to propose a structural reassignment of two molecular cages from a previously favored trimer to a pentamer or hexamer, and another from a trimer to a much higher oligomer, possibly an intriguing tetradecamer. In the former case, strong support for the reassignment to a larger cage is provided by an observation of a slow reversible transformation of the initially formed cage into a smaller but spectrally very similar one upon dilution. In the latter case, freeze-fracture transmission electron micrographs demonstrate that at least some of the solutions are colloidal, and high-resolution electron transmission and atomic force microscopy images are compatible with a tetradecamer but not a trimer. Comparison of solute partial molar volumes deduced from measurement of solution density with volumes anticipated from molecular models argues strongly against the presence of large voids (solvent vapor bubbles) in cages dissolved in nitromethane. The presence of bubbles was previously proposed in an attempt to account for the bilinear nature of the Eyring plot of the rate constant for pyridine ligand edge exchange reaction in one of the cages and for the unusual activation parameters in the high-temperature regime. An alternative interpretation is proposed now.

Hydrated nonpolar solute volumes: Interplay between size, Attractiveness, and molecular structure

A solute's partial molar volume determines its response to pressure, which can result in changes in molecular conformation or assembly state. Computing speed advances have made accurate partial molar volume evaluation in water routine, allowing for the dissection of the molecular factors underlying this significant thermodynamic variable. A recent simulation analysis of the volumes of nonpolar molecular solutes in water reported that the apparent solvent-free border thickness enshrouding these solutes grows with increasing solute size, based on the assumption the solute can be treated as an individual sphere [Biophys. Chem. 161 (2012) 46]. This suggests the solvent dewets these solutes as they grow in size. Via simulations of dewetted repulsive spherical solutes, we show that the border thicknesses of the largest non-polar molecular solutes tend towards that of a repulsive sphere. When attractive interactions are accounted for, however, the spherical solute border thicknesses fall below that of the largest molecular solutes. We demonstrate that if the molecular solutes are treated with atomic detail rather than approximated as an individual sphere, the border thickness variation is minimal. A geometric model is put forward that reproduces the inferred border thickening, indicating the implied dewetting results from a breakdown in the spherical volume approximation.

Stress analysis of a cylindrical composition-gradient electrode of lithium-ion battery in generalized plane strain condition

A novel cylindrical composition-gradient electrode is considered to be one of most potential structures in lithium-ion battery. To investigate the mechanism of a cylindrical composition-gradient electrode under potentiostatic operation, we take Li1.2(Mn0.62Ni0.38)0.8O2 for example. The effects of the three main factors, i.e., diffusion coefficient, Youngs modulus, partial molar volume of solute, on the stress field in the cylindrical electrode are discussed. Each of the three material parameters is assumed to be a linear function of the distance from the center to surface. The small deformation theory and thermodynamic theory are employed to establish the mathematical model of composition-gradient cylindrical electrode. The mechanics equations and diffusion equation of cylindrical electrode are derived for an inhomogeneous material in plane strain condition. By comparing with single-phase electrode, it is found that Youngs modulus increasing from the center to the surface greatly reduces the max tensile radial stress and tensile hoop stress and changes the location of max radial stress since the radial displacement of the center is restricted. The time for the lithium-ions to reach the center is longer and the tensile stress near the center decreases at dimensionless time =0.0574 when diffusion coefficient decreases along the radial direction. Owing to the smaller diffusion coefficient at the surface, there is a reduction in the number of lithium-ions through the unit area in unit time when their corresponding concentration gradients are the same. The variation of partial molar volume means that the volume expansion caused by the intercalation of lithium-ions decreases along the radial direction. Therefore the partial molar volume decreasing along the radial direction considerably reduces the radial stress and the distribution of tangential stress becomes flat. The center point is picked, showing the development of hoop stress. The results show that the hoop stress increases and reaches a maximal value close to the dimensionless time =0.0574. Maximal tensile hoop stress at the center is reduced in an inhomogeneous material. The tensile hoop stress turns into compressive stress over time when elastic modulus and partial molar volume are denoted with E(r) and (r) respectively. The results indicate that the cylindrical composition-gradient electrode with core enriched Ni and edge enriched Mn reduces the max tensile radial stress and tensile hoop stress. It is an efficient way to avoid mechanical fracture in electrode since evidence has accumulated that tensile stress is the lead cause of crack in electrode. The result also provides useful guidance for mitigating the stresses in a cylindrical electrode.

Analysis of hydration parameter for sugars determined from viscosity and its relationship with solution parameters

The hydration parameter h was obtained from the viscosity B-coefficients and the partial molar volume of solute, V2, for various sugars and urea in aqueous solutions. The parameter h showed a good correlation with the parameter α, determined from the activity coefficient of water, representing the solute-solvent interaction. The parameter h also showed a good correlation with the number of equatorial-OH groups (e-OH) for sugars, suggesting that the sugar molecules with the higher e-OH fit more to the water-structure. From the temperature dependence of the parameter h (dh/dT), the negative dh/dT for sugars suggested their water-structure making activity while the positive dh/dT for urea corresponded to its structure breaking effect. From the Arrhenius plot, the activation energy for h, Ea, was determined to be as low as 10kJ/mol for disaccharides suggesting the stable hydration structure. The Ea increased with a decrease in molecular weight for sugars.

Limiting Ionic Partial Molar Volumes of R4N+ and Ī in Aqueous Methanol at 303.15 K

From density measurements of solutions of R4NI (R = CH3 through n –C4H9), NaBPh4 and NaI in 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 mass % methanol + water at 298.15 K, limiting partial molar volumes of solutes and limiting ionic partial molar volumes of R4N+ and I– have been calculated and interpreted in terms of ion- ion, ion- solvent and solvent- solvent interactions.

Note: Nonpolar solute partial molar volume response to attractive interactions with water

The impact of attractive interactions on the partial molar volumes of methane-like solutes in water is characterized using molecular simulations. Attractions account for a significant 20% volume drop between a repulsive Weeks-Chandler-Andersen and full Lennard-Jones description of methane interactions. The response of the volume to interaction perturbations is characterized by linear fits to our simulations and a rigorous statistical thermodynamic expression for the derivative of the volume to increasing attractions. While a weak non-linear response is observed, an average effective slope accurately captures the volume decrease. This response, however, is anticipated to become more non-linear with increasing solute size.

Thermodynamic studies of ionic interactions in aqueous solutions of N-butyl-pyridinium bromide at 298.15 K

Density and osmotic coefficient measurements for aqueous solutions of N-butyl-pyridinium bromide [Bpy][Br] in concentration range ~0.019 to ~0.39mol·kg−1 at 298.15K are reported. The density data are used to obtain apparent molar volume (ϕV), partial molar volume of solute and solvent V¯2andV¯1 respectively as well the limiting partial molar volume ϕ¯V0=V¯20 of the solute [Bpy][Br] (by appropriate extrapolation). The experimental osmotic coefficient (ϕ) data are used to determine the activity and mean ionic activity coefficients of solute and solvent respectively. Experimental activity coefficient data are compared with those obtained from Debye–Hückel and Pitzer models. The activity data have been further processed to obtain the Gibbs free energy change due to mixing (ΔGm) and excess Gibbs free energy change (ΔGE). The aggregation number (n) and critical micelle concentration (cmc) are obtained for ionic salt in solution phase by applying pseudo-phase separation model to ϕ and ϕV data respectively. Application of McMillan–Mayer theory of solutions to the data is made. The results have been interpreted on the basis of structural characteristic of salt, ion–solvent and ion–ion interactions.

Estudio hidrofóbico de soluciones acuosas diluidas de isómeros de pentanodiol a varias temperaturas a partir de datos volumétricos

Density of dilute aqueous solutions of 1,2 pentanediol, 2,4 pentanediol, 1,4 pentanediol and 1,5 pentanediol at 283.15, 288.15, 293.15, 298.15, 303.15 and 308.15 K in the concentration range 0.0000 to 0.0060 in mole fraction were determined by using Wood-Brusie type capillary neck pycnometers. The solute partial molar volume as a function of solute concentration for each system was correlated with a linear equation for each temperature to estimate the slope limit and the partial molar volume at infinite dilution, and the predominant hydrophilic-hydrophobic effect was found in this region.

Pseudo-critical behavior on the partial molar volume of solutes in the isotropic phase of liquid crystal

Temperature dependence of partial molar volume of 4-amino-4′-nitrobiphenyl (ANB) and 4,4′-dinitrobiphenyl (DNB) in the isotropic phase of 4-n-pentyl-4′-cyanobiphenyl (5CB) was determined. Addition of ANB to 5CB causes increase of isotropic–nematic phase transition temperature (TIN) [1]. The decrease of partial molar volume of ANB was observed while the increase of partial molar volume of DNB and triphenyl phosphite (TPP) [8] was observed with approaching TIN. The anomalous behavior of partial molar volume was discussed using treatments similar to that of other thermodynamic derivatives in the I–N transition.

Apparent molal volumes of HMT and TATD in aqueous solutions around the temperature of maximum density of water

Apparent molal volumes V ϕ have been determined from density measurements for several aqueous solutions of 1,3,5,7-tetraazatricyclo[3.3.1.1(3,7)]decane (HMT) and 1,3,6,8-tetraazatricyclo[4.4.1.1(3,8)]dodecane (TATD) at T = (275.15, 275.65, 276.15, 276.65, 277.15, 277.65 and 278.15) K as function of composition. The infinite dilution partial molar volumes of solutes in aqueous solution are evaluated through extrapolation. Interactions of the solutes with water are discussed in terms of the effect of the temperature on the volumetric properties and the structure of the solutes. The results are interpreted in terms of water structure-breaking or structure forming character of the solutes.

Parsing Partial Molar Volumes of Small Molecules: A Molecular Dynamics Study

We used molecular dynamics (MD) simulations in conjunction with the Kirkwood-Buff theory to compute the partial molar volumes for a number of small solutes of various chemical natures. We repeated our computations using modified pair potentials, first, in the absence of the Coulombic term and, second, in the absence of the Coulombic and the attractive Lennard-Jones terms. Comparison of our results with experimental data and the volumetric results of Monte Carlo simulation with hard sphere potentials and scaled particle theory-based computations led us to conclude that, for small solutes, the partial molar volume computed with the Lennard-Jones potential in the absence of the Coulombic term nearly coincides with the cavity volume. On the other hand, MD simulations carried out with the pair interaction potentials containing only the repulsive Lennard-Jones term produce unrealistically large partial molar volumes of solutes that are close to their excluded volumes. Our simulation results are in good agreement with the reported schemes for parsing partial molar volume data on small solutes. In particular, our determined interaction volumes() and the thickness of the thermal volume for individual compounds are in good agreement with empirical estimates. This work is the first computational study that supports and lends credence to the practical algorithms of parsing partial molar volume data that are currently in use for molecular interpretations of volumetric data.

Propiedades Volumétricas y Viscosimétricas de Soluciones Acuosas Diluidas de 1,4 Pentanodiol a varias Temperaturas

Density and viscosity of dilute aqueous solutions of 1.4 Pentanediol were determined at temperatures between 283 and 308K, in a concentration range between 0 and 0.0060 in mole fraction. A Wood -Brusie type capillary neck pycnometer and an Ubbelohde viscometer were used. The partial molar volume of solute in terms of the solute concentration showed a negative slope for all temperatures, indicating that solute behaves in a hydrophobic way. The relative viscosity values were adjusted to a second order equation to obtain the coefficient B, which is related to the size and shape of the molecule of solute.

Thermal expansion and structure of tetrapropylammonium bromide aqueous solutions derived from density measurements

The density of tetrapropylammonium bromide aqueous solutions has been measured with six-figure precision at T/K – 273.15 = (5, 10, 15, 20, 25, 30, and 35) and molality from 0.05 to 8 (at 18 closely spaced intervals) using a vibrating-tube densitometer. The apparent molar volume, as well as both the solute and solvent partial molar volumes and their derivatives with respect to temperature, were calculated and compared with those of the tetra-alkyl ammonium (R 4N +, R: from methyl to butyl) halide solution series to detect structural transformations due to hydration and hydration interactions. Except for Me 4N–Cl, the results indicate progressive solvent structure enhancement in the R 4N + series and significantly different solute–solvent ratios for the “ideal” spatial (“interstitial”) and energetic co-sphere arrangements.

Impurity diffusion activation energies in Al from first principles

Activation energies for vacancy-mediated impurity diffusion in face-centered-cubic aluminum have been computed ab initio for all technologically important alloying elements, as well as for most of the lanthanides. The so-called five-frequency rate model is used to establish the limiting vacancy interchange process. Many elements were shown to be limited by Al-vacancy interchanges. For these elements we showed that the diffusion activation energy is rather close to that for Al self-diffusion, and additionally the diffusion pre-exponential factor is of the same order as that for Al self-diffusion. The diffusion activation energy is shown to exhibit a linear relation with the solute partial molar volume in Al. In contrast, transition metals are shown to deviate strongly from these generalities. Diffusion of transition-metal atoms is limited by solute-vacancy interchanges that require remarkably high activation energies. Transition-metal diffusivities in Al show strong trends with the number of $d$-valence electrons but not with partial molar volume.

Molar volumes of LiI in H 2O and D 2O solutions; Structural hydration interactions

According to a recent study of the H 2O and D 2O molar volume isotope effect (MVIE) of the alkali metal chloride solutions, neither the standard nor the excess MVIE of the LiCl corresponds to the usual hydrophilic hydration characteristics of the inorganic ions above room temperatures. This phenomenon can not be rationalized by electrostriction, with the collapse of the “loose” tetrahedral (“ice-like”) water structure due to the electrostatic (ion + dipole) interaction. It seemed possible that this unique hydration behaviour of the Li + would be stronger and could reveal further structural information with a less hydrophilic anion than the chloride. Therefore we have determined the MVIE of the LiI as a function of temperature and concentration. The densities of normal and heavy water solutions of LiI have been measured with six-figure precision at T = (288.15, 298.15, and 308.15) K from (0.03 to 4) molal, m, using a vibrating-tube densitometer. The solvent isotope effect on the apparent molar volume, as well as on the solute and solvent partial molar volumes, was evaluated. As expected, with the rationalization of the MVIE of LiI instead of the geometric structural differences of the isotopic solvents, the energetic contributions have to be considered at all the temperatures investigated. At infinite dilution, a high degree of compensation between the reversed influences of the Li + and I − on the activities of the isotopic solvents determines the MVIE. By increasing concentration, the highly asymmetric energetic interactions of the Li + and the I − with the solvent apparently result in a “mutual salting-out” effect. At a concentration ≈0.7 m, a uniquely abrupt structural rearrangement results in a “solvent-separated ion-pair” solution structure.