The effect of properties of water-organic solvent mixtures on the solvation enthalpy of 12-crown-4, 15-crown-5, 18-crown-6 and benzo-15-crown-5 ethers at 298.15 K

Crown ethers are preferential solvated by organic solvents in the mixtures of water with formamide, N-methylformamide, acetonitrile, acetone and propan-1-ol. In these mixed solvents the energetic effect of the preferential solvation depends quantitatively on the structural and energetic properties of mixtures. The energetic properties of the mixtures of water with hydrophobic solvents (N,N-dimethylformamide, dimethylsulfoxide, N,N-dimethylacetamide, hexamethylphosphortriamide) counteract the preferential solvation of the crown ether molecules. The effect of the hydrophobic and acid-base properties of the mixture of water with organic solvent on the solvation of 12-crown-4, 15-crown-5, 18-crown-6 and benzo-15-crown-5 ethers was discussed. The solvation enthalpy of one -CH₂CH₂O- group in water, N,N-dimethylformamide and hexamethylphosphortriamide is equal to −24.21, −16.04 and −15.91 kJ/mol, respectively. The condensed benzene ring with 15-crown-5 ether molecule brings about an increase in the exothermic effect of solvation of the crown ether in the mixtures of water with organic solvent.     

Ultrasonic and viscometric studies of molecular interactions in binary mixtures of tetrahydrofuran with some aromatic hydrocarbons at temperatures from 288.15 to 318.15 K

Densities of the binary systems of 2,2′-oxybis[propane] with ethyl acrylate, butyl acrylate, methyl methacrylate, and styrene have been measured as a function of the composition, at 298.15 K and atmospheric pressure, using an Anton Paar DMA 5000 oscillating U-tube densimeter and used to calculate the partial and excess volumes. The latter were correlated with the Redlich-Kister equation and with a series of Legendre polynomials. The excess volumes are negative for all the systems reported here.     

Blood porphyrins in binary mixtures of N,N-dimethylformamide with 1-octanol and chloroform: The energetics of solvation, (solute + cosolvent) interactions and model calculations

This study provides the first accurate analysis of the energetics of solvation of blood porphyrins in binary solvents which are considered as appropriate models for a smooth transition from a polar protein-like phase to an apolar lipid-like environment. Our results do indicate that hematoporphyrin dimethylether dimethylester (HDEDE) and deuteroporphyrin dimethylether (DDE), as well as the model of their ester side-chains ethyl acetate (EtOAc), reveal more exothermic solvation in chloroform (CHCl₃) than in dimethylformamide (DMF) and, especially, in 1-octanol (OctOH). The energetics of pair interaction between dissolved species and cosolvent molecules both in a protein-like and a lipid-like environment are clearly associated with these solvation effects. The interaction between blood porphyrins and DMF in OctOH is accompanied by large negative enthalpy changes at both temperatures, whereas in chloroform, forming strong H-bonds with dissolved species, the interaction is strongly thermochemically repulsive. All solute molecules interact in the energetically unfavorable way with OctOH and CHCl₃ in DMF, the effect being much stronger pronounced for chloroform. The most significant result of this work is that it is possible to connect this pair interaction in a highly diluted solution with the solute behavior in the entire range of the binary mixture. The approach proposed is independent of a solute and solvent structure, it provides a good prediction of the energetics of solvation in mixed solvents and can be extended for a lot of other biologically active solutes.     

Topological and thermodynamic investigations of molecular interactions in binary mixtures: Molar excess volumes and molar excess enthalpies

Molar excess volumes and molar excess enthalpies of butyl acetate (i) with cyclohexane or benzene or toluene or o-, m- or p-xylene (j) binary mixtures have been measured dilatometrically and calorimetrically over the entire composition range at 308.15 K. The observed data have also been analyzed in terms of graph theoretical approach. The analysis of V^E data by graph theoretical approach suggests that butyl acetate in pure state exists as associated entity and (i + j) mixtures are characterized by the presence of (i–j) molecular entity. It has further been observed that V^E and H^E values calculated by this approach agree well with the corresponding experimental values. The presence of molecular entity is further confirmed by IR study of (i + j) mixture.     

Volumetric and transport properties of binary liquid mixtures of N-methylacetamide with lactones at temperatures (303.15 to 318.15) K

The values of density (ρ), viscosity (η) and speed of sound (u) have been measured for binary liquid mixtures of γ-butyrolactone (GBL), δ-valerolactone (DVL), and ε-caprolactone (ECL) with N-methylacetamide (NMA) over the whole composition range at T = (303.15 to 318.15) K and atmospheric pressure. From these data, excess molar volume (V^E), deviation in viscosity (Δη), and deviation in isentropic compressibility (Δκ_s), are calculated. The results are fitted to a Redlich–Kister type polynomial equation to derive binary coefficients and standard deviations.     

Preferential solvation of Fe(phen)2(CN)2 in binary aqueous acetone and 2-methoxyethanol mixtures

Summary Preferential solvation ofbis-1,10-phenanthroline-bis-cyanoiron(II) was investigated in aqueous acetone and 2-methoxyethanol binary mixtures. The solvatochromic behaviour is discussed in terms of donor and acceptor numbers. The thermodynamic model ofFrankel was used to treat preferential solvation in the binary aqueous 2-methoxyethanol mixtures and reveals that preferential solvation by the organic solvent occurs. The preferential solvation constant at 298.15K was found to be equal to 3.30±0.039, and the free energy of preferential solvation amounts to 2.96kJ·mole^–1.

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Bevorzugte Solvatation von Fe(phen)₂(CN)₂ in binären Mischungen aus Wasser und Aceton bzw. 2-Methoxyethanol

Zusammenfassung Die bevorzugte Solvatation vonbis-1,10-Phenanthrolin-bis-cyanoeisen(II) wurde in binären wäßrigen Mischungen mit Aceton bzw. 2-Methoxyethanol als organischer Komponente untersucht. Das solvatochrome Verhalten wird in Zusammenhang mit Donor- und Akzeptorzahlen diskutiert. Die theoretische Behandlung erfolgte mit Hilfe des thermodynamischen Modells vonFrankel und zeigt, daß das organische Lösungsmittel bevorzugt solvatisiert. Die entsprechende Konstante bei 298.15K wurde zu 3.30±0.039 ermmittelt. Die freie Energie der bevorzugten Solvatation beträgt 2.96kJ·mol^–1.

     

Volumetric, ultrasonic and viscometric studies of binary mixtures of dimethyl sulphoxide with chloro and nitro substituted aromatic hydrocarbons at T = 303.15 K

Excess volumes (V^E) ultrasonic sound velocities (u), isentropic compressibilities (K_s) and viscosities (η) have been measured for the binary mixtures of dimethylsulphoxide (DMSO) with 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,2,4-trichlorobenzene, o-chlorotoluene, m-chlorotoluene, p-chlorotoluene, o-nitrotoluene and m-nitrotoluene at T = 303.15 K. The measured V^E values were positive over the entire composition range in all the binary mixtures. Isentropic compressibilities (K_s) have been computed for the same systems from precise sound velocity and density data. Further, deviation in isentropic compressibility (ΔK_s) from ideal behaviour was also calculated. The viscosity data are analysed on the basis of corresponding states approach. Deviation in viscosities are positive over the entire composition range. The measured data is explained on the basis of intermolecular interactions between unlike molecules.     

Study of molecular interactions in the polar binary mixtures of N-methyl aniline and alcohols,using excess dielectric and thermodynamic parameters

Molecular interactions between the polar systems N-methyl aniline and alcohols (propan-1-ol/propan-2-ol) for various mole fractions at different temperatures are studied by determining the dielectric permittivity using LF impedance analyzer, Microwave bench and Abbe’s refractometer in radio, microwave and optic frequency regions respectively. The dipole moment, excess dipole moment, excess Helmholtz energy, excess permittivity, excess inverse relaxation time and excess thermodynamic values are calculated using experimental results. The optimized geometry, harmonic vibrational wave numbers and dipole moments of pure and equimolar binary mixtures have been calculated theoretically from the ab initio Hartree–Fock (HF) and Density Functional Theory (DFT – B3LYP) methods with 6-31+G¹ and 6-311+G⁷ basis sets using Spartan 08 modelling software. Conformational analysis of the formation of hydrogen bond in the equimolar binary mixture systems of N-methyl aniline and alcohols (propan-1-ol/propan-2-ol) is supported by experimental FT-IR spectra. The calculated wave numbers and dipole moments agree well with the experimental values. Further, the correlations among the parameters are discussed in detail.     

Acoustic,viscometric and optical properties of binary mixtures of tetrahydrofuran with 1-propanol and 2-propanol

The values estimated from various mixing rules for the ultrasonic velocity, viscosity and refractive index have been compared with the respective values measured earlier at 293, 303, and 313?K over the entire mole fraction range of two binary mixtures of tetrahydrofuran (THF) with 1-propanol (1-p) and 2-propanol (2-p). There is an excellent agreement between the experimental values of ultrasonic velocity and of refractive index with the respective values obtained from the mixing rules. The mixing rules for viscosity provide values agreeing broadly with those obtained from experimental measurements. The relative merits and interrelations of these mixing rules are discussed.     

Volumetric,viscometric and acoustic properties of binary mixtures of 2-propanol with n -alkanes (C6, C8, C10) at 298.15 and 308.15 K

Densities (ρ), viscosities (η), and speeds of sound, (u) of the binary mixtures of 2-propanol with n-alkanes (n-hexane, n-octane, and n-decane) were measured over the entire composition range at 298.15 and 308.15 K and at atmospheric pressure. Using the experimental values of density, viscosity and speed of sound, the excess molar volumes (V ^E), viscosity deviations (Δη), deviations in speed of sound (Δu), isentropic compressibility (κ _s), deviations in isentropic compressibility (Δκ _s), and excess Gibbs energies of activation of viscous flow (ΔG* ^E) were calculated. These results were fitted to the Redlich–Kister type polynomial equation. The variations of these excess parameters with composition were discussed from the viewpoint of intermolecular interactions in these mixtures. The excess properties are found to be either positive or negative depending on the molecular interactions and the nature of liquid mixtures.     

Volumetric and viscosity studies of interactions between sodium phosphate salts and poly(propylene glycol) 400 in aqueous solutions at different temperatures

Density and sound velocity at the 288.15–313.15 K and viscosity at the 298.15–313.15 K temperature range at 5 K intervals for polypropylene glycol (PPG) in aqueous solutions of sodium di-hydrogen phosphate, di-sodium hydrogen phosphate and tri-sodium phosphate with salt mass fractions 0.00, 0.010 and 0.020 are reported at atmospheric pressure. From the experimental density and sound velocity data, the apparent specific volume, excess specific volume, isentropic compressibility and isentropic compressibility deviation values have been determined. The infinite dilution apparent specific volume and isentropic compressibility values of PPG have been obtained and from which the infinite dilution apparent specific volumes of transfer of PPG from water to aqueous sodium phosphate solutions have been obtained for the investigated salt concentrations and temperatures. The excess specific volume, isentropic compressibility and viscosity deviation are negative and decrease in magnitude as temperature, concentration of sodium phosphate and charge on the anion of electrolyte increases.     

Volumetric,acoustic, and viscometric studies of molecular interactions in binary mixtures of diethylene glycol monomethyl ether with 1-alkanols at temperatures from (293.15 to 308.15) K

In this work, densities ρ, speeds of sound u, and viscosities η, have been measured over the whole composition range for the binary mixtures of diethylene glycol monomethyl ether (DEGMME), CH₃(OCH₂CH₂)₂OH with 1-hexanol, CH₃(CH₂)₅OH, 1-octanol, CH₃(CH₂)₇OH, and 1-decanol, CH₃(CH₂)₉OH at T = (293.15, 298.15, 303.15, and 308.15) K along with the properties of the pure components. By using the experimental values of ρ, u, and η, excess molar volume, $V_m^E$, deviations in viscosity, Δη, isentropic compressibility κ_S, deviations in isentropic compressibility Δκ_S, deviations of the speed of sound Δu, have been calculated. The viscosity results have also been analysed in terms of some semi-empirical equations.     

NMR studies of preferential solvation of sodium cation in mixtures of N-methylformamide with water and some nonaqueous solvents

Sodium-23 NMR chemical shifts and linewidths have been measured for 0.1M NaClO₄ in binary mixtures of N-methylformamide (NMF) with a series of other solvents, as a function of the solvent mole fraction. The relative solvent composition at the isosolvation point, the mid-value of the Na-23 chemical shift between those measured in the respective pure solvents, reveals preferential solvation of the sodium cation in many cases. The isosolvation composition correlates well with the relative solvating abilities of the two solvents-as characterized by their donicities-provided that the cation-solvent interactions are of the hard-hard type and that they are not complicated by interionic interactions. The variation in the electric field gradient around the sodium nucleus, as the composition of the solvent changes, results in broadening of the resonance line. Maximum broadening occurs close to the solvent mole fraction corresponding to the isosolvation point.     

Excess and deviation properties for the binary mixtures of methylcyclohexane with benzene, toluene, p-xylene, mesitylene, and anisole at T = (298.15, 303.15, and 308.15) K

Experimental data on density, viscosity, and refractive index at T = (298.15, 303.15, and 308.15) K, while speed of sound values at T = 298.15 K are presented for the binary mixtures of (methylcyclohexane + benzene), methylbenzene (toluene), 1,4-dimethylbenzene (p-xylene), 1,3,5-trimethylbenzene (mesitylene), and methoxybenzene (anisole). From these data of density, viscosity, and refractive index, the excess molar volume, the deviations in viscosity, molar refraction, speed of sound, and isentropic compressibility have been calculated. The computed values have been fitted to Redlich-Kister polynomial equation to derive the coefficients and estimate the standard errors. Variations in the calculated excess quantities for these mixtures have been studied in terms of molecular interactions between the component liquids and the effects of methyl and methoxy group substitution on benzene ring.     

Peculiar properties of sodium lodide in alcohols,acetone, and alcohol-water mixtures at lower temperatures

The enthalpies of solution of sodium iodide in methanol, ethanol and acetone and in mixtures of methanol and ethanol with water were measured over wide ranges of electrolyte concentration and temperature. Standard enthalpies of solution, transfer enthalpies of NaI from alcohols to alcohol-water mixtures, and temperature coefficients of enthalpies of solution have been calculated. Thermodyanmic characteristics of solution and solvation of the Na⁺ and I^– ions in acetone and ethanol were determined at 243–298 K. It is noted that at lower temperatures the disruption of solvent structure by ions is a local effect. The presence of negative solvation of the Na⁺ and I^– ions in alcohol-water mixtures at lower temperatures is demonstrated.