Excess Molar Volumes and Excess Viscosities of the Propan-2-ol + Tetrahydrofuran + 1-Chlorobutane Ternary System at 25°C

Excess molar volumes and excess viscosities of the propan-2-ol + tetrahydrofuran+ 1-chlorobutane system have been determined at 25°C from measurements ofdensities and viscosities. Various expressions are proposed in the literature tocalculate these excess properties from binary data. The empirical correlation ofCibulka is shown to be the best in this system for excess volume, viscosity, andenergy of activation for viscous flow. An application to excess molar volumeshas been made by using Flory's theory. For viscosities, we applied the equations ofGrunberg and Nissan, Katti and Chaudhri, Bloomfield and Dewan, and Wu—andfinally the GC-UNIMOD model.     

Thermodynamic Investigation of the Azeotropic Mixture Composed of Water and Benzene

The molar heat capacity of the azeotropic mixture composed of water and benzene was measured by an adiabatic calorimeter in the temperature range from 80 to 320 K. The phase transitions took place in the temperature range from 265.409 to 275.165 K and 275.165 to 279.399 K. The phase transition temperatures were determined to be 272.945 and 278.339 K, which were corresponding to the solid-liquid phase transitions of water and benzene, respectively. The thermodynamic functions and the excess thermodynamic functions of the mixture relative to standard temperature 298.15 K were derived from the relationships of the thermodynamic functions and the function of the measured heat capacity with respect to temperature.     

Theoretical Description of Excess Molar Functions in the Case of Very Small Excess Values. Investigation of Excess Molar Volumes of Propan-2-ol + Alkanol Mixtures

The densities of propan-2-ol + pentan-1-ol, + hexan-1-ol, + heptan-1-ol, + octan-1-ol + nonan-1-ol and speeds of sound in propan-2-ol + pentan-1-ol, + heptan-1-ol, + nonan-1-ol have been measured over the whole composition range at 298.15 K. Excess molar functions determined from the experimental data have been plotted as functions of composition. The excess molar volumes have been interpreted on the basis of the Symmetrical Extended Real Associated Solution Model (S-ERAS).     

Measurements of the Molar Heat Capacities and Excess Molar Heat Capacities for Water + Organic Solvents Mixtures at 288.15 K to 303.15 K and Atmospheric Pressure

Experimental molar heat capacity data (Cp _m) and excess molar heat capacity data (Cp^E_m\mathit{Cp}^{\mathrm{E}}_{\mathrm{m}}) of binary mixtures containing water + (formamide or N,N-dimethylformamide or dimethylsulfoxide or N,N-dimethylacetamide or 1,4-dioxane) at several compositions, in the temperature range 288.15 K to 303.15 K and atmospheric pressure, have been determined using a modified 1455 PAAR solution calorimeter. The excess heat capacities are positive for aqueous solutions containing 1,4-dioxane, N,N-dimethylformamide or dimethylsulfoxide, negative for solutions containing water + formamide and show a sigmoid behavior for mixtures containing water + N,N-dimethylacetamide, over the whole composition range. The experimental excess molar heat capacities are discussed in terms of the influence of temperature and of the organic solvent type present in the binary aqueous mixtures, as well as in terms of the existing molecular interactions and the organic solvent’s molecular size and structure.     

Spin–Spin Relaxation in the 17O NMR Spectra of Na+ and K+ Water Clusters

Relaxation characteristics of Na⁺ and K⁺ water clusters were studied by ¹⁷O NMR spectroscopy. The influence of viscosity and pH of solution was taken into account; for both electrolytes in the concentration range -4 M, spin–spin relaxation times are greater than those for pure water. For K⁺ clusters, maxima of the concentration dependence of ¹⁷O spin–spin relaxation time have been found.     

Infrared Spectrum of the Adamantane+–Water Cation: Hydration-Induced C−H Bond Activation and Free Internal Water Rotation

Diamondoid cations are reactive intermediates in their functionalization reactions in polar solution. Hydration is predicted to strongly activate their C−H bonds in initial proton abstraction reactions. To study the effects of microhydration on the properties of diamondoid cations, we characterize herein the prototypical monohydrated adamantane cation (C₁₀H₁₆⁺–H₂O, Ad⁺–W) in its ground electronic state by infrared photodissociation spectroscopy in the CH and OH stretch ranges and dispersion-corrected density functional theory (DFT) calculations. The water (W) ligand binds to the acidic CH group of Jahn–Teller distorted Ad⁺ via a strong CH⋅⋅⋅O ionic H-bond supported by charge–dipole forces. Although W further enhances the acidity of this CH group along with a proton shift toward the solvent, the proton remains with Ad⁺ in the monohydrate. We infer essentially free internal W rotation from rotational fine structure of the ν₃ band of W, resulting from weak angular anisotropy of the Ad⁺–W potential.     

Excess Molar Volumes and Excess Viscosities of the Ternary System Diethylamine(1) + Ethyl Acetate(2) + n-Heptane(3) at 25°C

Densities and viscosities were experimentally determined in the whole range ofcomposition at 25°C for the ternary system diethylamine(1) + ethyl acetate(2)+ n-heptane(3) and for the three corresponding binary systems. Excess molarvolumes and excess viscosities were calculated for the binaries and the ternarysystems. Results were fitted and predicted with expressions from the literatureand are analyzed to gain insight about liquid mixture interactions.     

Limiting Partial Molar Excess Heat Capacities and Volumes of Selected Organic Compounds in Water at 25°C

Well-known Picker flow microcalorimeters for the differential measurements of volumetric heat capacities have been employed in conjunction with vibrating tube densimeters to determine the molar heat capacity, volume, and the apparent properties in dilute aqueous solutions for 17 organic solutes of moderate hydrophobicity. The dependence on concentration of the apparent properties allowed the limiting partial molar quantities at infinite dilution to be extrapolated and the limiting partial molar excess quantities to be evaluated. Comparison with available literature data shows good agreement. The application of group contribution rules to the limiting partial properties has been tested using the original method and parameters proposed by Cabani et al. The predicted values of the partial molar volumes are in fair agreement with the present data except for some less common solutes. With partial molar heat capacities, the agreement is less satisfactory. To improve the performance of the method, missing parameters for some types of monofunctional and bifunctional molecules have been evaluated.     

Investigation of the Thermodynamic Properties of the Cationic Surfactant CTAC in EG + Water Binary Mixtures

To understand the thermodynamic characteristics of cationic surfactants in binary mixtures, the aggregation behavior of hexadecyltrimethylammonium chloride (CTAC) has been investigated in ethylene glycol (EG) + water solvent mixtures at different temperatures and EG to water ratios. The critical micelle concentration (CMC) and degree of counter ion bonding (β) were calculated from electrical conductivity measurements. An equilibrium model for micelle formation was applied to obtain the thermodynamic parameters for micellization, including the standard Gibbs energies of micellization (DG_mic^o)\Delta G_{\mathrm{mic}}^{\mathrm{o}}), standard enthalpies of micelle formation (DH_mic^o)\Delta H_{\mathrm{mic}}^{\mathrm{o}}) and standard entropies of micellization (DS_mic^o)\Delta S_{\mathrm{mic}}^{\mathrm{o}}). Our results show that DG_mic^o\Delta G_{\mathrm{mic}}^{\mathrm{o}} is always negative and slightly dependent on temperature. The process of micellization is entropy driven in pure water, whereas in EG + water mixtures the micellization is enthalpy driven.     

Theoretical Study on the Structures and Properties of Hydrogen Bonding Complexes between Diazines and Water

Density functional theory B3LYP method and second-order Moller-Plesset perturbation theory MP2 method were employed to obtain the optimized geometries of the ground state and interaction energy for diazines and water complexes. The results show that the ground state complexes have strong hydrogen bonding interaction with -20.99, -16.73 and -15.31 kJ/mol after basis set superposition error and zero-point vibration energy correction for pyridazine-water, pyrimidine-water and pyrazine-water, respectively, and large red-shift for the symmetric H-O stretching vibration frequencies due to the formation of N…H-O hydrogen bond in the diazine-water complexes. The NBO analysis indicates that intermolecular charge transfer are 0.0316, 0.0255 and 0.0265 e respectively. In addition, the first singlet （n,n＊） vertical excitation energy of the monomer and the hydrogen bonding complexes between diazines and water was investigated by time-dependent density functional theory.     

Influence of the Water Content on the Thermal Behaviour of β-Cyclodextrin at Low and Very Low Temperature

Heat capacities of -CD·9.7H₂O weremeasured by adiabatic calorimetry in the temperature range10–300 K. Differential scanning calorimetry wasused to follow the evolution of the thermalbehaviour versus hydration ratio between 170 and300 K. At least three different behaviours wereobserved, according to the number, n, of watermolecules: 0 < n < 7, 7 < n < 10, and n > 10.These macroscopic results are discussed in terms oforganization differences between the most or theleast hydrated -CD. The structuring effectof the hydration water molecules is emphasised. Theexistence of two energetically distinct -CDhydrates (n < 10 and n > 10) seems to be confirmed. Thishypothesis is discussed in comparison with previousspectroscopic and structural studies.     

Thermodynamic Properties of the Ternary System Potassium Bromide + Lithium Bromide + Water at 25°C

Activity coefficients of potassium bromide in aqueous mixtures of potassium bromide and lithium bromide were determined by emf measurement at 25°C and at six ionic strengths from 0.1 to 2.5 mol·kg^-1. The experimental data were fitted using the Scatchard–Rush–Johnson and Pitzer models. The osmotic coefficients, excess Gibbs energies of mixing, and activity coefficients of lithium bromide in aqueous mixtures were calculated using Pitzer mixing parameters obtained in this work.     

Excess Molar Volumes, Excess Molar Enthalpies, and Excess Isentropic Compressibilities of Binary Mixtures Containing N-Methyl-2-Pyrrolidone and Isomeric Xylenes at 308.15?K

Excess molar volumes, excess molar enthalpies and speeds of sound of 1-methyl pyrrolidin-2-one?+?o- or m- or p-xylene binary mixtures have been measured over the entire composition range at 308.15?K. The speed of sound data were used to determine the excess isentropic compressibilities. It is observed that while the values of the excess molar enthalpies for the investigated mixtures are positive, the values of the excess molar volumes and excess isentropic compressibilities are negative over the entire composition range. The measured thermodynamic data have been analyzed in terms of Graph, Prigogine?CFlory?CPatterson, and the Sanchez and Lacombe theories. It is observed that Graph theory correctly predicts the signs and magnitudes of the excess molar volumes, excess molar enthalpies, and excess isentropic compressibilities of the studied mixtures. However, the excess molar volumes, excess molar enthalpies and excess isentropic compressibilities predicted by Prigogine?CFlory?CPatterson and Sanchez and Lacombe theories are of same sign.     

Molecular Organization of Reagents in the Kinetics and Catalysis of Liquid-Phase Reactions: XI. Manifestation of the Structure of Solution in the Kinetics of Water Addition to Isocyanate in Water–Dioxane Mixtures

Evidence for the structural effect of liquids associated by hydrogen bonds on the kinetics of molecular reactions was experimentally found. The kinetics of hydrolysis of (phenylaza)phenyl isocyanate in water–dioxane mixtures was studied at various temperatures and in the presence of structure-making and structure-breaking additives. The apparent order of reaction with respect to water concentration increased with temperature because of the partial breaking of the H-bond solution structure. It was found that the value of was affected by salt additives, for which positive (Et₄NCl) or negative (KI) hydration is typical. This hydration resulted in strengthening or partially breaking the H-bond structure of water, respectively. It follows from the kinetic data that the addition of 0.1 mol/l Et₄NCl was equivalent to a decrease in the solution temperature by 6 to 7°, whereas the addition of 0.1 mol/l KI was equivalent to an increase in the temperature by 5 to 6°. The effect of poly(ethylene oxide) additives (which stabilize the structure of water) on the value of was similar to the effect of the tetraethylammonium salt, which is characterized by positive hydration.     

On the Role of the Solvent and Substituent on the Protonation Equilibria of Di-Substituted Anilines in Dioxane–Water Mixed Solvents

Protonation constants of a number of di-substituted anilines were determined potentiometrically in 0, 20, 30, 40, 50, and 60% (v/v) dioxane–water mixtures at (25.00 ± 0.02) ^∘C with an ionic strength of 0.10 mol-dm⁻³ sodium perchlorate. The data are discussed in terms of the electronic character of the substituents. Two different methods were used to study the effects of the solvents on the protonation constants; one involved a single polarity parameter, the Dimroth–Reichardt parameter E_T(30); the other involved the Kamlet–Taft multi-parametric method. The protonation constants of di-substituted anilines correlate with the molecular parameters for the dipolarity/polarizability of the solvent, π^∗, and its hydrogen-bond acceptor ability, β.     

Analysis of the long range potentials of the X 1Σ+ and a 3Σ+ states of NaK

The difference in energy between the singlet and triplet states of NaK dissociating to Na(3s) and K(4s) is found from experimental data and from pseudopotential calculations. The contributions of various one- and two-electron integrals are evaluated, illustrating the present ambiguity over the exchange integral and the exchange interaction terms.