Journal of Solution Chemistry最新文献

Urea, as a nonelectrolyte molecular solute in aqueous solutions, has a vital role in the thermodynamic, thermophysical and physiochemical studies. To a large extent, addition of Urea to water does not alter the structural dynamics of water. Only a little amount of water molecules is supposed to be closely associated with urea molecules. Therefore, study of intramolecular as well as intermolecular interactions in the binary aqueous urea solution by conducting thermophysical and thermodynamic investigations is quite important. In this work, new experimental data on water activity for solutions containing urea under precisely controlled conditions and derived thermodynamic parameters were reported. Water activity of urea was also estimated from the Kirkwood–Buff integrals in a novel way.

In this study, we investigate some structural and dynamical properties of aqueous KCl solutions at different temperatures and concentrations. We study a 1.6 mol·kg^–1 aqueous KCl solution at five temperatures and five concentrations at ambient conditions only. Molecular dynamics simulations with the flexible SPC water model were conducted to characterize all partial pair correlation functions, the velocities auto-correlation ones, and the dielectric constants. The analysis of the water pair correlation functions shows a disruption of the H-bond network and a decrease of the oxygen-hydrogen coordination number as temperature or salt concentration increases. The increase of each parameter favors the exchange of molecules between the first and the second hydration shells. Ions pair correlation functions show principally that the fraction of K⁺-Cl⁻ contact ion pairs increases and that of separated ion pairs decreases with increasing temperature or concentration. For all particles, the values of the calculated self-diffusion coefficients rise with temperature and fall with salt concentration. The self-diffusion coefficients of K⁺ and Cl⁻ tend to towards each other at high concentration. Temperature or salt concentration causes a drop in the dielectric constant. For all studied temperatures or salt concentrations, the calculated ratio of the orientational correlation times τ₁/τ₂ for the OH vector indicates that the motion of water molecules can be accounted for by an angular jumps model.

The interaction mechanism between xanthan gum (XG) and bovine serum albumin (BSA) was studied by various spectral and molecular docking techniques. The fluorescence spectrum analysis reveals that XG and BSA are quenched, with XG quenching BSA in a static manner according to the Stern-Volmer equation. The Vant’s Hoff equation indicates negative values for the thermodynamic parameters ΔH, ΔG, and ΔS during the binding process. Therefore, it can be concluded that hydrogen bonding and van der Waals forces dominate the interaction between XG and BSA, resulting in a spontaneous and exothermic quenching process. The results of molecular docking simulation show that hydrogen bond and van der Waals force are the main forces between XG and BSA. Through multispectral analysis, it is observed that XG affects the microenvironment of BSA by increasing its polarity and hydrophilicity while weakening its hydrophobicity. This leads to changes in the secondary structure of BSA molecules. The binding distance between XG and BSA is calculated to demonstrate energy transfer between them, and overlap integral calculations confirm the presence of non-radiative energy transfer from XG to BSA. Analysis of the circular dichroism spectrum reveals that interaction between BSA and XG leads to protein relaxation, a decrease in α-helix structure, and an increase in β-sheet structure, providing further evidence for alterations in the secondary structure of BSA. Through the study of the interaction between XG and BSA, the interaction mechanism of both is analyzed, which provides data support for their future discussion and research.

Motivated by the scarcity of prior research, in this study we report the synthesis and photophysical characteristics of newly obtained benzanthrone ethynyl derivatives. Fourier-transform infrared spectroscopy, ¹H and ¹³C nuclear magnetic resonance spectroscopy and high-resolution mass spectrometry elucidated the structures of the compounds. To study photophysical characteristics, absorbance and emission spectra were measured in solvents with different polarities. Photofading proved high stability of the synthesized compounds (up to 96% of initial absorption after irradiation for 4 h). The analyzed compounds are fluorescent (quantum yields from 0.01 to 0.74 in ethanol) with a significant solvatochromic effect (from 466 nm in benzene to 720 nm in dimethyl sulfoxide). Based on these findings, there is a correlation between the electronic nature of substituents and photophysical parameters. Hence, these compounds could find applications as probes in fluorescence microscopy and sensors to detect polarity variations.

Graphical Abstract

Non-ionic hydrophobic eutectic solvents have emerged as a new class of eutectic solvents. They are prepared by mixing two non-ionic components. They have gained significant interest compared to their counterpart ionic hydrophobic eutectic solvents and hydrophobic ionic liquids due to the availability of a wide array of non-ionic substances that can be used to prepare these solvents. Understanding the distinct physical characteristics of these solvents is crucial to their practical application within process industries and associated fields. The present work reports the development of a density model for these solvents based on the conductor-like screening model (COSMO), a dielectric continuum solvation model. For this purpose, a comprehensive literature search was carried out, and 485 density points of 37 different hydrophobic non-ionic eutectic solvents were collected. COSMO volume, one of the outputs of the COSMO calculations, was correlated with the experimental molar volume for the model development. Two different models were developed, one at 298.15 K and another a general model that can predict the density over a wide temperature range at atmospheric pressure. The developed model only requires the molar ratio and COSMO volumes of the components forming the eutectic solvents to predict the density. The proposed general model performed better than most other models and was comparable with the best one reported in the literature, with an average relative deviation percent (ARD%) of 1.34%.

The zinc boron complex formation was studied as a function of temperature (25, 50 and 70 °C) in boric acid solutions of various concentration (0.25, 0.50 and 0.68 mol·kg⁻¹). pH was monitored during zinc ion addition by galvanostatic dissolution of a zinc metal electrode, in a solution of boric acid. The determination of the complex formation showed the importance of an accurate model of the polyborate speciation, recalculated for this work based on the previous literature data mainly potentiometric measurements completed by Raman spectroscopy and Ab Initio calculations. Modelling of our experimental results, considering various scenarios of boric acid speciation, was performed using R and PhreeqC, suggesting the formation of an aqueous triborate-zinc (II) complex, ({{text{ZnB}}}_{3}{{text{O}}}_{3}{({text{OH}})}_{4({text{aq}})}^{+},) according to the reaction: ({{text{Zn}}}^{2+}+3{{text{B}}({text{OH}})}_{3} rightleftharpoons {{text{ZnB}}}_{3}{{text{O}}}_{3}{({text{OH}})}_{4({text{aq}})}^{+}+2{{text{H}}}_{2}{text{O}}+{{text{H}}}^{+}). The nature and structure of this aqueous complex disagrees with the results reported previously in the literature. Three formation constants of the triborate-zinc (II) complex were determined at 25, 50 and 70 °C as ({{text{log}}}_{10}{K}_{text{ZnB}}) = − 4.73 ± 0.10, − 4.21 ± 0.16 and − 4.94 ± 0.12, respectively. The evolution of zinc boron complex formation as a function of temperature (between 25 and 70 °C) provides information on the effect of the polyborate predominance in the solution on the complexation of zinc.

In a binary liquid mixture containing pyrimidine-substituted azetidinone ultrasonic velocities, densities, and viscosities have been measured by unit of molality azetidinone at temperatures T = (298.15, 308.15, and 313.15 K). 3-chloro-4-(4-nitrophenyl)-1-(pyrimidin-2-yl)azetidin-2-one (AT₁) and 3-chloro-4-(4-chlorophenyl)-1-(pyrimidin-2-yl)azetidin-2-one (AT₂) in N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) were studied. The density, dynamic viscosity, and ultrasonic sound velocity have all been measured, among other acoustical and thermodynamic properties. Gibbs free energy of activation (ΔG*), enthalpy of activation (ΔH*), and entropy of activation (ΔS*) values have been studied further to determine how solvent changes and structural modifications impact these values. The molecular interactions between the components of the liquid combination have been used to explain these findings.

Titrimetric methods were used to estimate the molar solubility and apparent acid dissociation constant (K_c) of salicylic acid in water. This was done with varied ionic strength values ranging from 0.00 to 0.75 mol·L⁻¹ and over a temperature range of 15 to 60 °C. The thermodynamic dissociation constant (as pK_a) of salicylic acid was found to be 2.985 at 25 °C. Within the measured temperature range, there was no consistent association between the pK_a of salicylic acid and the temperature. The pK_a values exhibited an inverse relationship with temperatures between 15 and 40 °C, while they showed a direct relationship with temperatures between 40 and 60 °C. Through the use of the Van’t Hoff plot, the standard thermodynamic quantities (∆H°, ∆S°, and ∆G°) for the dissociation process of salicylic acid in water were calculated. For temperatures between 15 and 30 °C, these values were determined as 3.346 kJ·mol⁻¹, − 19.99 JK⁻¹·mol⁻¹, and 9.306 kJ·mol⁻¹ respectively. For the temperature range of 45 to 60 °C, the values were calculated as − 1.499 kJ·mol⁻¹, − 27.06 kJ·K⁻¹·mol⁻¹, and 6.564 kJ·mol⁻¹. The heat of solution (∆H ^°_sol ) was computed using the Van’t Hoff Isochore plot across the temperature range of 15 to 60 °C, resulting in a value of 15.03 kJ·mol⁻¹.

pH and thermo-sensitive polymeric nanoparticles with different morphology were synthesized by means of emulsion polymerization techniques. The materials were characterized by gravimetric techniques, dynamic light scattering (DLS), electrophoresis, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and X-Ray diffraction (XRD). The specific volumetric thermodynamic properties were calculated from density (ρ) and sound velocity (u) measurement and they are influenced by the proportions and location of the functional groups in the polymeric particles and the temperature. Rheological properties were also measured, observing that polymeric materials were a non-Newtonian and pseudo-plastic behavior because of they have a decrease in viscosity (left(eta right)) values as the shear rate rises (left(dot{gamma }right)). In addition, to try to elucidate the behavior that the materials could have with calcite rock in the oil reservoirs, the materials were treated with CaCl₂, and changes in the average particle size, colloidal stability and conformation of polymeric chains were observed. The obtained results show that the synthesized polymeric particles could be applied as a possible dosing agent in the interaction with calcium ions (Ca²⁺) in the calcite rock for petrol industry.

In the present work, the density, speed of sound, and refractive index of binary mixtures of propiophenone (PP) with 3-amino-1-propanol (AP), propylamine (PA), or isobutanol (IB) were measured over whole composition range at temperatures 298.15 to 308.15 K and ambient pressure (0.1 MPa). From these experimental data the excess molar volume, ({V}_{text{m}}^{text{E}}), excess isoentropic compressibility, ({kappa }_{text{S}}^{text{E}},) and excess refractive index, ({n}_{text{D}}^{text{E}}), were calculated. The calculated excess molar properties were correlated by Redlich–Kister equation, and their coefficients and standard deviations were calculated. The results show that the ({V}_{text{m}}^{text{E}}) values of PP + AP are positive in the entire composition range and at all temperatures, while the ({V}_{text{m}}^{text{E}}) values of PP + PA and PP + IB mixtures are negative over whole composition range and at all temperatures. The obtained ({V}_{text{m}}^{text{E}}) values were also correlated by Prigogine–Flory–Patterson (PFP) theory which show good agreement between experimental and predicted data.