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Abstract The densities of the binary mixture {water (1) + tetramethylurea (2)} have been measured in the entire composition range in the temperature range from 274.15 K to 333.15 K at atmosphere pressure. Excess molar volumes and molar isobaric thermal expansions of the mixture, apparent and partial molar volumes, partial molar isobaric expansions of water and tetramethylurea (TMU), including their limiting values, are calculated. It is shown that the formation of the water + tetramethylurea mixture occurs with a decrease in the volume of the mixture at all temperatures, and the partial molar volumes of water and TMU increase with increasing temperature. The temperature dependences of the limiting partial molar isobaric thermal expansions of both components are characterized by the presence of the extremum. The obtained results are discussed in terms of solute-solvent and solute-solute interactions. Graphical abstract Unlabelled Image Highlights • Temperature-dependent densities of water + tetramethylurea mixtures were measured. • Excess molar volumes and partial molar volumes of components were calculated. • Molar isobaric expansion for mixture was discussed. [ABSTRACT FROM AUTHOR]

Densities of the mixture {water (1) + N- methylurea (2)} in the concentration range to mole fraction x2 = 0.07071 (or to the solution molality concentration m2 = 4.22335 mol·kg-1) at atmospheric pressure in the temperature range from 274.15 to 333.15 K and compression k = ΔV/V0 at pressures to 100 MPa (10, 25, 50, 75, and 100) in the temperature range from 278.15 to 323.15 K (278.15, 288.15, 288.15, 308.15, 323.15) in the same concentration range were calculated in this study. The apparent molar volumes of N-methylurea Vφ,2 and the partial molar volumes of both components V1 and V2 in the mixture, molar isothermal compressibilities KT,m, molar isobaric thermal expansions EP,m, and isochoric coefficients of thermal pressure β of the mixture were calculated. Moreover, volumetric measures for the infinitely dilute solution of N-methylurea solution were calculated: limiting partial molar volumes V2∞, the limiting partial molar isothermal compressibilities KT,2∞, and the limiting partial molar isobaric thermal expansions EP,2∞. The results obtained are discussed from the point of view of solute-solvent and solute-solute interactions. [ABSTRACT FROM AUTHOR]

The density of {water (1) + ethylenediamine (2)} binary mixture was measured over the whole concentration range at temperatures from 274.15 to 333.15 K and at atmospheric pressure. The experimental values were used to calculate a whole number of the mixture parameters such as the excess molar volumes, molar isobaric expansions, apparent and partial molar volumes, partial molar isobaric expansions, limiting partial molar volumes and limiting partial molar isobaric expansions both of water and ethylenediamine. The extremal dependence of the partial molar volumes of the mixture components was observed; the mixture excess molar volumes were negative at all temperatures and depended weakly on temperature. The concentration dependences of the partial molar volumes of the mixture components were very similar to the dependences for aqueous mixtures of the nonelectrolytes with hydrophobic properties. The mixture molar isobaric expansion increased with ethylenediamine concentration over the whole concentration range. The concentration dependences of partial molar isobaric expansions of both water and ethylenediamine were rather complex and correlated with the mixture melting diagram. [ABSTRACT FROM AUTHOR]

The coefficients of compressibility, k = Δ V / V o , of liquid binary mixture of {water (1) + glycerol (2)} were measured over the whole composition range at pressures from (0.1 to 100) MPa and temperatures from (278.15 to 323.15) K. Excess molar volumes of the mixture, V m E , partial molar volumes of the mixture components, V ¯ i , as well as their limiting values, molar isothermal compression K T , m , molar isobaric expansion E P , m , molar isochoric elasticity (isochoric coefficient of thermal pressure) β m were calculated. It was revealed that with glycerol molar fraction increasing the coefficients of compressibility, k , decreased to x 2 ≈ 0.3 ÷ 0.4 (where x 2 was glycerol molar fraction), and further changed insignificantly. It was shown that all isobars of excess molar volumes were negative and their absolute values, V m E , decreased on temperature and pressure rising. No extremes were observed on concentration dependences of partial molar volumes of glycerol in the mixture at its low concentrations. Under the state parameters studied limiting partial volumes of water and glycerol decrease with pressure rising but increase with temperature growth. Dependences of molar isothermal compression and molar isochoric elasticity on glycerol molar fraction passed extremes, and similar dependences of molar isobaric expansion had the temperature inversion regions. [ABSTRACT FROM AUTHOR]

Abstract: Molar isothermal compressions, molar isobaric expansions, molar coefficients of thermal pressure, and internal pressures of {water (1)+ethylene glycol (2)} mixture over the whole concentration range, as well as partial molar isothermal compressions and partial isobaric expansions of water in ethylene glycol and of ethylene glycol in water at infinite dilution were calculated at pressures from 0.1 to 100MPa and at temperatures from 278.15 to 323.15K. It was revealed that concentration dependences of molar isothermal compressions K T,m , molar isobaric expansions E P,m , and thermal pressure coefficients, β, on ethylene glycol molar fraction had extremes. Temperature and baric dependences of internal pressure of the mixture were almost linear, and coefficients of these dependences at low ethylene glycol concentrations differed from those coefficients for water, ethylene glycol, and their mixtures with high diol content. Analysis of the volume characteristics obtained confirmed both hydrophilic and hydrophobic ethylene glycol nature. [Copyright &y& Elsevier]

Abstract: Molar isothermal compressions, molar isobaric expansions, molar coefficients of thermal pressure, and internal pressure were calculated over the whole concentration range of {water (1)+ tert-butanol (2)} mixture at pressures from 0.1 to 100MPa and temperatures from 278.15 to 323.15K. It was revealed that the extremes, observed on concentration dependences of molar isothermal compression and molar isobaric expansion of the mixture, became more pronounced with pressure growth and temperature lowering. Values of molar thermal pressure coefficients of the mixture sharply rose at compositions with small TBA mole fraction and then decreased practically linearly with the alcohol content increasing. Temperature and pressure dependences of the mixture internal pressure were almost linear, and at low TBA concentrations changed significantly from the dependences of water, tert-butanol and their mixtures at large alcohol content. [Copyright &y& Elsevier]

Abstract: The coefficient of compressibility, k = ΔV/Vo , of {water (1)+ tert-butanol (2)} binary mixture was measured at pressures from 0.1 to 100MPa and temperatures from 278.15 to 323.15K over the concentration range of liquid mixture occurrence. The whole composition range from 0 to 1 tert-butanol mole fraction was studied at 323.15K only because of the mixture freezing at lower temperatures. Over the whole pressure range in question partial molar volumes of the components at all temperatures studied and excess molar volumes of the mixture only at 323.15K were calculated. It was shown that when pressure increased, the values of excess molar volume decreased, and minimum on concentration dependence of VE on tert-butanol mole fraction shifted to the region of low tert-butanol content. For every pressure studied extremes were observed on the concentration dependences of partial molar volumes of the mixture components. The values of limiting partial molar volumes increased with temperature growth and tended to maximum at pressure slightly higher of 100MPa. [Copyright &y& Elsevier]

Abstract: The coefficient of compressibility, k =ΔV/V o , of {water (1)+ethylene glycol (2)} binary mixture was measured at pressures from 0.1 to 100MPa and temperatures from 278.15 to 323.15K over the whole concentration range. At all state parameters the following characteristics were calculated: excess molar volumes of the mixture, ; changes of excess molar Gibbs energy, ; changes of excess molar entropy, ; changes of excess molar enthalpy, ; mixing enthalpy, , of water with ethylene glycol at high pressure, and partial molar volumes of the components. It was shown that the coefficients of compressibility, k, sharply decreased over the concentration interval x 2 =0–0.2, where x 2 was ethylene glycol mole fraction, and further changed insignificantly. It was revealed that excess molar volumes were negative at all temperatures studied and went down with pressure increasing. The dependence of partial molar volumes of the mixture components on ethylene glycol mole fraction passes extreme at all isobars. Limiting partial molar volumes of water and ethylene glycol decrease with pressure growth. The mixture compression leads to its ordering due to new hydrogen bonds formation. [Copyright &y& Elsevier]

Abstract: Densities of ethylene glycol(1)+ tert-butanol(2) mixtures were measured between (278.15–348.15) K at atmospheric pressure over the entire composition range with a vibrating tube densimeter. It was found that specific volume of mixture increases with growth of tert-butanol concentration at all temperatures under study. Excess molar volumes, apparent and partial molar volumes of ethylene glycol and tert-butanol, coefficients of isobaric expansion of mixture and partial molar isobaric expansion of the components were calculated. Excess molar volumes of the mixture are negative at all temperatures, and deviation from ideality is increased with temperature rise. Excess molar volumes were described by Redlich–Kister equation. Partial molar volumes of ethylene glycol decrease sharply at x 2 →1. Temperature dependence of partial molar volumes of ethylene glycol is characterized by inversion at х 2 ≈0.7. The “negative expansion” of limiting partial volumes of ethylene glycol was observed. Coefficients of isobaric expansion of the mixtures increased with rise both of tert-butanol concentration and temperature. [Copyright &y& Elsevier]

Measurements of the binary mixture {water (1) + 1,3-dimethylurea (2)} density within the temperature range of 274.15 to 333.15 K were performed within a wide range of compositions at the atmospheric pressure by using the density gauge with a U-shaped vibrating tube. There are calculated apparent and partial molar volumes of water and 1,3-dimethylurea (1,3-DMU) in the mixture, limiting (standard) partial molar volumes of 1,3-DMU in water, molar isobaric thermal expansion of the mixture and molar isobaric thermal expansion of 1,3-DMU at infinite dilution. It is shown that concentration dependences of partial molar volumes of the water and 1,3-DMU are characterized by the presence of extremums thus revealing manifestation of hydrophobic nature of the 1,3-dimethylurea molecule. Limiting partial molar volumes of 1,3-DMU increase with the increase of the temperature. Increasing both the temperature and the concentration of 1,3-DMU lids to the increasing of the molar isobaric expansion of the mixture. The obtained results are discussed in terms of the solute – solvent and solute – solute interactions. A comparison of the obtained characteristics with similar characteristics of the urea, N -methylurea and tetramethylurea is performed. Unlabelled Image • Temperature-dependent densities of water +1,3-dimethylurea mixtures were measured. • Apparent/partial molar volumes of components were calculated. • Molar isobaric expansion for mixture was discussed. • A comparison with other methyl substituted urea analogues was made. [ABSTRACT FROM AUTHOR]

• Temperature-dependent densities of water – N-methylacetamide mixtures were measured. • Excess molar volumes and partial molar volumes of components were calculated. • The comparison of volumetric characteristics at the changes in the structure of amide molecules was considered. The densities ρ of the binary mixture of N -methylacetamide with water have been measured in the entire composition range of the mixture liquid state at T = (278.15, 288.15, 298.15, 308.15, 323.15 and 333.15) K at atmospheric pressure (0.1 MPa). The densities were also measured for dilute aqueous solutions of N -methylacetamide (from 0.00455 to 0.05743 mol fractions) at a temperature from 274.15 to 283.15 K, with an increment of 1 K at atmospheric pressure, in order to study the effect of N -methylacetamide on the temperature of the maximum water density. These data were later used to calculate the excess molar volumes. V m E., partial molar volumes of water V 1 and N -methylacetamide V 2 , and to obtain the limiting partial molar volumes V i ∞ and limiting partial molar isobaric expansion of N -methylacetamide E P ,2 ∞. The following volumetric characteristics were then obtained from these values: the shift temperature of the maximum density, Hepler's constant, the pressure derivative of the second virial coefficient, relative volumetric parameter of hydration. The obtained parameters show the effect of N -methylacetamide on water. The study also included a comparison of these volumetric characteristics for several aqueous solutions of amides: acetamide, urea and N -methylurea. The paper also presents a comparison of these parameters at the changes in the structure of amide molecules. [ABSTRACT FROM AUTHOR]

[Display omitted] • Behavior of the volumetric properties of the binary water-NMA mixture was studied over wide pressure ranges. • Hydrogen bonds in NMA–water mixtures were analyzed using computer chemistry and vibrational spectroscopy. • The analysis of the strength of the hydrogen bond between amides and surrounding water molecules is carried out. • The hydrogen atoms of water and amide compete as hydrogen bond donors. A combined approach of computational chemistry, vibrational spectroscopy experiments, and density measurements was used to study the structural properties of water-N-methylacetamide mixtures over the entire concentration range. The structure of N-methylacetamide dimers and hydrogen-bonded complexes of N-methylacetamide with water molecules was investigated by the quantum chemical method on the basis of the density functional theory. The vibrational spectra of aqueous solutions of N-methylacetamide were recorded. Based on quantum chemical calculations, the bands of the vibrational spectrum were identified, which made it possible to trace the change in hydrogen bonding in the system. At increased N-methylacetamide concentration, the hydrogen bond network rearranges. The number of hydrogen bonds between water molecules decreases, water molecules bind to N-methylacetamide molecules, changing the nature of its environment. Aqueous mixture containing N-methylacetamide shows strong deviations of volumetric properties from ideality. For the further analysis of the data obtained, molecular dynamics simulation of this system was conducted at various temperatures and pressures. It was shown that the resulting hydrogen bonds are of medium strength, but their strength depends on the water molecule environment, which is proved by NBO and QTAIM data. A network of hydrogen bonds is formed in N-methylacetamide aqueous solution, which is noticeably destroyed with an increase in temperature and slightly changes with an increase in pressure. [ABSTRACT FROM AUTHOR]