Unlike Molecules Research Articles

Temperature Dependent Microwave Dielectric Characterization of Associated Liquids

The present paper reports static dielectric constants, densities, viscosities, and refractive indices of the binary mixtures of ethanol with DMSO measured at 303 K, 308 K, 313 K. These measured parameters are used to obtain the derived properties, such as the Bruggeman factor, the molar polarization, the excess molar volume, the excess viscosity, the excess static dielectric constant, and the excess molar polarization. The variation in magnitudes of these quantities with composition and temperature is used to discuss the type, strength, and nature of binary interactions. The excess parameters are fitted to the Redlich Kister (R-K) fit equation. The evaluated values of the excess dielectric constant and the excess molar polarization infer that deviations of their mixture values occur from the mole-fraction mixture law. The results confirm that there are dipole-dipole interactions between unlike molecules of ethanol+DMSO mixtures and that 1:1 complexes are formed. The excess static dielectric constant indicates that there is a decrease in the total number of parallel aligned effective dipoles that contribute to the mixture dielectric polarization. It is observed that the excess molar volume becomes more and more positive with the corresponding increase in the temperature. This observation certainly leads to the inference that the intermolecular interaction strength decreases with the temperature.

Investigation of molecular interactions in binary mixtures of homologous series of aliphatic alcohols with 2-methoxyaniline at various temperatures

ABSTRACTThermodynamic and transport properties (excess molar volume, excess isentropic compressibility and deviation in viscosity) are calculated from the experimental density, speed of sound and viscosity. The results are analysed in terms of rupture of hydrogen-bonded chain as the dipolar interaction between 2-methoxyaniline and 1-alkanol (1-hexanol, 1-heptanol and 1-octanol) exceeds the intermolecular interaction through dipole-dipole and hydrogen bonding between these unlike molecules. The VE results are analysed in the light of Prigogine-Flory-Patterson theory. Analysis of each of the three contributions viz. interactional, free volume and P* to VE has shown that interactional contribution are positive for all systems, the free volume effect and P* contribution are negative for all the mixtures.

Physical properties of deep eutectic solvents formed by the sodium halide salts and ethylene glycol, and their mixtures with water

Deep eutectic solvents (DESs), with their attractive properties, are currently of great interest. Introducing new kinds of eutectic solvents with different components as their hydrogen bond donors (HBD) and hydrogen bond acceptors (HBA), and investigating the (thermo-) physical properties of the new DESs can play an important role in promoting future research and use of such mixtures. In this study, we investigate the feasibility of the formation of new kinds of eutectic solvents based on the sodium halide salts as the hydrogen bond acceptors with ethylene glycol as the hydrogen bond donor. Different molar fractions of HBD/HBA were investigated. The results indicated that sodium fluoride does not form a DES throughout the whole concentration range investigated, while sodium chloride, sodium bromide, and sodium iodide do form eutectic mixtures at certain molar ratios. Differential scanning analysis was performed on the resulting eutectic solvents to measure the glass transition temperature. Other physical properties of the proposed DESs, namely density, viscosity, refractive index, and electric conductivity were also measured within the temperature range of 293–333 K. Furthermore, the effect of water in aqueous mixtures of the proposed DESs was investigated, with molar fractions of water ranging from 0.1 to 0.9. Based on the calculations of excess molar volume, the effect of water in the mixtures was investigated. Over the whole range of water concentrations in the mixture, the excess molar volumes had negative values, indicating intensive hydrogen-bonding between unlike molecules in the mixture and/or a void filling mechanism by the smaller molecules.

Investigation of molecular interactions in binary mixtures of 2-methoxyaniline with cyclic ketones at various temperatures through thermophysical properties

Densities (ρ) and speeds of sound (u) of binary mixtures of 2-methoxy aniline with acetophenone and cyclic ketones (cyclopentanone and cyclohexanone) including those of pure liquids, over the entire composition range, were measured at temperatures (303.15, 308.15, 313.15 and 318.15) K and atmospheric pressure 0.1 MPa. Using the experimental data, VE, $$\kappa_{\text{s}}^{\text{E}}$$ , $$\bar{V}_{\text{m,1}}^{\text{E}}$$ , $$\bar{V}_{\text{m,2}}^{\text{E}}$$ , $$\bar{K}_{\text{s,m,1}}^{\text{E}}$$ and $$\bar{K}_{\text{s,m,2}}^{\text{E}}$$ were calculated. The variation of these excess properties with the composition of the mixtures suggests hydrogen bond, dipole–dipole interactions and charge transfer complex formation between unlike molecules. The VE results have been analyzed in the light Prigogine–Flory–Patterson theory. An analysis of each of the three contributions viz. interactional, free volume and characteristic pressure $$P^{*}$$ to VE shows that interactional contribution is positive for all binary systems. The free volume effect and characteristic pressure $$P^{*}$$ contribution are negative for all the mixtures.

Refractive Indices, Molar Refractions, Surface Tension and Polarizability For Binary Mixtures of Benzyl Alcohol with Glycols and Their Deviations Sahar M. Tawfik and Farid M. Farag Refining division, Egyptian Petroleum Research Institute Nasr City, Cairo, 11727 Egypt E-mail: sahartawfikepri@yahoo.com

ABSTRACT Densities (ρ), refractive indices (nD) and surface tension (σ) have been measured as a function of composition for binary mixtures of benzyl alcohol (BA) with ethylene glycol (EG), diethylene glycol (DEG) and triethylene glycol (TEG)] at ambient temperature and atmospheric pressure. Using these data, excess molar volume (VE), excess refractive indices (nDE), molar refraction deviation (ΔR), excess surface tension (σE) and the polarizability (α) have been calculated. The results were interpreted interms of specific interactions between the unlike molecules

Thermodynamic properties of binary mixtures of n-butylammonium-based ionic liquids with ethanol at T = (293.15–313.15) K

In this study, density, speed of sound and viscosity of binary mixtures of ionic liquids + ethanol have been measured as a function of composition at T = (293.15–313.15) K and atmospheric pressure. The ionic liquids studied were: {n-butylammonium acetate (N4Ace), n-butylammonium propanoate (N4Pro), n-butylammonium hexanoate (N4Hex), and n-butylammonium decanoate (N4Dec)}. Excess molar volume, $$V_{\text{m}}^{\rm{E}}$$ , deviation in isentropic compressibility, $$\Delta \kappa_{\text{S}}$$ , deviation in viscosity, $$\Delta \eta$$ , and excess Gibbs energy of activation of viscous flow, $$\Delta G^{ * \rm{E}}$$ , were obtained from experimental results and correlated with the Redlich–Kister polynomial equation. Ionic liquids were synthesized and characterized using 1H-NMR, 13C-NMR and FTIR spectroscopy techniques. For all systems studied, the values of $$V_{\text{m}}^{\rm E}$$ , $$\Delta \kappa_{\text{S}}$$ and $$\Delta \eta$$ were negative over the entire composition range, whereas $$\Delta G^{ * \rm{E}}$$ values were positive over the entire composition range. The results obtained were discussed in terms of structural effects and intermolecular interactions between like and unlike molecules.

Thermodynamics of Ethanol + Water + 2-Propanol mixture at the range of temperature 288.15-323.15 K

The packing properties of hydroxylic chemicals is very unusual, however these substances find extensive application in food and alcoholic beverage industry. When short alcohols are mixed with water, the entropy of the final system increases far less than we could expected for an ideal solution of ramdomly interacting molecules. Experimental works on thermodynamics helps to understand how hydrophobic headgroups of alcohol molecules in aqueous media cluster together. To this aim, the densities and ultrasonic velocity of the ternary mixtures ethanol + water + 2-propanol at 288.15-323.15 K and atmospheric pressure, have been measured over the whole concentration range, due to the importance of the 2-propanol among the flavor compounds contained into spirit beverages. The experimental data have been analyzed in terms of different theoretical models, an adequate agreement between the experimental and predicted values both in magnitude and sign being obtained, despite the high non-ideal trend. The obtained experimental values indicate varying extent of interstitial accommodation among unlike molecules with strong influence of steric hindrance among aliphatic ends.

Helical inversions and phase separations in binary mixtures of cholesteric liquid crystalline molecules

ABSTRACTA mean field theory is introduced to describe a helical inversion in nematic-cholesteric mixtures and binary cholesteric mixtures. Taking into account a chiral coupling between unlike molecules, the helical pitch is derived as a function of orientational order parameters and concentration. We find the conditions of helical inversions for the mixtures and derive the concentration of the helical inversions, depending on the chiral interaction. The numerical results are in agreement with the experimental results. We also examine phase separations on the temperature-concentration plane, including the helical inversions. A large variety of phase separations, such as the two-phase coexistence between a right-handed rich and a left-handed rich phase, etc., are predicted.

Thermodynamics of mixtures containing a very strongly polar compound. 12. Systems with nitrobenzene or 1-nitroalkane and hydrocarbons or 1-alkanols

Mixtures involving nitrobenzene and hydrocarbons, or 1-alkanols and 1-nitroalkane, or nitrobenzene have been investigated on the basis of a whole set of thermophysical properties available in the literature. The properties considered are: excess molar functions (enthalpies, entropies, isobaric heat capacities, and volumes), vapour-liquid and liquid-liquid equilibria, permittivities or dynamic viscosities. In addition, the mixtures have been studied by means of the application of the DISQUAC, ERAS, and UNIFAC models, and using the formalism of the concentration-concentration structure factor. The corresponding interaction parameters in the framework of the DISQUAC and ERAS models are reported. In alkane mixtures, dipolar interactions between 1-nitroalkane molecules are weakened when the size of the polar compound increases, accordingly with the relative variation of their effective dipolar moment. Dipolar interactions are stronger in nitrobenzene solutions than in those containing the smaller 1-nitropropane, although both nitroalkanes have very similar effective dipole moment (aromaticity effect). Systems with 1-alkanols are characterized by dipolar interactions between like molecules which sharply increases when the alkanol size increases. Simultaneously, interactions between unlike molecules become weaker, as the OH group is then more sterically hindered. Interactions between unlike molecules are stronger in systems with nitromethane than in nitrobenzene solutions. The replacement of nitromethane by nitroethane in systems with a given 1-alkanol leads to strengthen those effects related with the alcohol self-association. Permittivity data and results on Kirkwood's correlation factors show that the addition of 1-alkanol to a nitroalkane leads to cooperative effects, which increase the dipolar polarization of the solution, in such way that the destruction of the existing structure in pure liquids is partially counterbalanced. This effect is less important when longer 1-alkanols are involved.

Thermo-acoustic and FTIR studies on binary liquids mixture of ethyl oleate and benzaldehyde at 303.15 to 318.15 K

Ultrasonic velocity, density and viscosity of two liquid mixtures ethyl oleate with benzaldehyde have been determined at various temperatures in the range of 303.15 to 318.15 K. The ultrasonic velocity, viscosity and density data are used to estimate adiabatic compressibility, free length, molar volume and free volume along with their excess values. The observed variations of the said parameters with concentration and temperature are discussed in terms of the intermolecular interactions between the unlike molecules of the binary mixtures. FT-IR spectra confirm the expected interactions.

Thermodynamics of mixtures with strongly negative deviations from Raoult's law. XV. Permittivities and refractive indices for 1-alkanol + n-hexylamine systems at (293.15–303.15) K. Application of the Kirkwood-Fröhlich model

Relative permittivities at 1 MHz, εr, and refractive indices at the sodium D-line, nD, are reported at 0.1 MPa and at (293.15–303.15) K for the binary systems 1-alkanol + n-hexylamine (HxA). Also, their corresponding excess functions are calculated and correlated. Positive values of the excess permittivities, εrE, are encountered for the methanol system, whereas the remaining mixtures show negative values. This reveals that interactions between unlike molecules contribute positively to εrE. This contribution is dominant for the methanol mixture, while those arising from the breaking of interactions between like molecules are prevalent for the remaining mixtures. At φ1 (volume fraction) = 0.5, εrE changes in the order: methanol > 1-propanol > 1-butanol > 1-pentanol < 1-heptanol. Similar variation with the chain length of the 1-alkanol is observed for mixtures such as 1-alkanol + heptane, or + cyclohexylamine, and can be explained in terms of the lower and weaker self-association of longer 1-alkanols. The effect of the replacement of HxA by cyclohexylamine, or by aniline, is also shown. Calculations on molar refractions indicate that dispersive interactions in the systems under study increase with the length of the 1-alkanol. The mixtures are studied by means of the application of the Kirkwood-Fröhlich model, and the Kirkwood correlation factors, including the corresponding excess values, are reported.

Solvent similarity analysis−from qualitative to quantitative

We put forward a new expression of similarity between solute and solvent in terms of the cohesive energy for unlike molecules, which provides a quantitative measure of the principle that ‘like dissolves like’. The investigation results indicate that as Vr (volume ratio) and SHSPR (the Square of Hansen Solubility Parameter Ratio) are far larger than unity (Vr ≫ 1, SHSPR ≫ 1), the similarity degree between solute and solvent is dominate by difference in molecular structure (size and interaction energy); as SHSPR approaches unity (SHSPR → 1), the similarity degree is irrelative with molecular size, and it depends only on its deviation from ideal solution (positive or negative deviation). Its applications in water−solvent miscibility analysis, appropriate solvent selection for polymers and chemical products purification (liquid-liquid extraction and re-crystallization) have been verified with successful results.

Thermodynamics properties of binary mixtures of aqueous solutions of glycols at several temperatures and atmospheric pressure

Abstract Densities (ρ), speeds of sound (u) and viscosities (η) for binary mixtures of {water + ethanol, or + ethylene glycol (EG), or + diethylene glycol (DEG), or + triethylene glycol (TEG), or + polyethylene glycol (PEG) 200, or + polyethylene glycol (PEG) 300, or + polyethylene glycol (PEG) 400, or + polyethylene glycol (PEG) 600, or + glycerol} have been determined as a function of composition at T = (293.15, 298.15, 303.15 and 308.15 K) and atmospheric pressure. From these results, excess molar volume ( V m E ), deviation in isentropic compressibility (ΔκS), deviation in viscosity (Δη), and excess Gibbs energy of activation for viscous flow (ΔG∗E) were calculated and fitted by the Myers-Scott equation, as a function of mole fraction. Values of V m E and ΔκS were negative over the entire composition range for all mixtures studied. The values of Δη were negative for the systems containing ethylene glycol and glycerol and positive for the systems containing ethanol, PEG 400 and PEG 600. For other systems, the deviation of viscosity presented an S-shape, with negative values at high water concentration. For all mixtures studied, the values of ΔG∗E were positive over the entire composition range. The results obtained were discussed in terms of structural effects and intermolecular interactions between like and unlike molecules.

The Study of Solute–Solvent Interactions in 1-Butyl-3-Methylimidazolium Hexafluorophosphate + 2-Pyrrolidone from Volumetric, Acoustic, Optical and Spectral Properties

The density (ρ), speed of sound (u) and refractive index (nD) of [Bmim][PF6], 2-pyrrolidone and their binary mixtures were measured over the whole composition range as a function of temperature between (303.15 and 323.15) K at atmospheric pressure. Experimental values were used to calculate the excess molar volumes \( \left( {V_{m}^{\text{E}} } \right) \), excess partial molar volumes \( \left( {\overline{V}_{m}^{\text{E}} } \right) \), partial molar volumes at infinite dilution \( \left( {\overline{V}_{m}^{{{\text{E}},\infty }} } \right) \), excess values of isentropic compressibility \( \left( {\kappa_{S}^{\text{E}} } \right) \), free length \( \left( {L_{\text{f}}^{\text{E}} } \right) \) and speeds of sound \( \left( {u^{\text{E}} } \right) \) for the binary mixtures. The calculated properties are discussed in terms of molecular interactions between the components of the mixtures. The results reveal that interactions between unlike molecules take place, particularly through intermolecular hydrogen bond formation between the C2–H of [Bmim][PF6] and the carbonyl group of pyrrolidin-2-one. An excellent correlation between thermodynamic and IR spectroscopic measurements was observed. The observations were further supported by the Prigogine–Flory–Patterson (PFP) theory of excess molar volume.

Thermodynamic and FT-IR study on molecular interactions between ethyl lactate with alkyl amines at different temperatures

ABSTRACTDensities (ρ) and speeds of sound () were measured for the binary mixtures formed by ethyl lactate with n-propylamine, diisopropylamine, dipropylamine and tripropylamine mixtures at temperatures (303.15, 308.15 and 313.15) K over the entire composition range. These data were used to compute the isentropic compressibilities (), intermolecular free lengths (), excess molar volume (), excess isentropic compressibility (), excess inter molecular free lengths () and excess speeds of sound (). The excess functions were fitted and correlated with Redlich–Kister equation. The measured data were discussed in terms of intermolecular interactions between component molecules. The values in the investigated mixtures were compared with various theoretical models to check their relative merits of pure component properties. FT-IR studies have been carried out and analysed to study the presence of interactions between unlike molecules of these mixtures. A good agreement is observed among the excess parameters and FT-IR studies.

Thermodynamics of amide + amine mixtures. 4. Relative permittivities of N,N-dimethylacetamide + N-propylpropan-1-amine, + N-butylbutan-1-amine, + butan-1-amine, or + hexan-1-amine systems and of N,N-dimethylformamide + aniline mixture at several temperatures. Characterization of amine + amide systems using ERAS

Relative permittivities at 1 MHz, εr, and at (293.15–303.15) K are reported for the binary systems N,N-dimethylacetamide (DMA) + N-propylpropan-1-amine (DPA), + N-butylbutan-1-amine (DBA), + butan-1-amine (BA) or + hexan-1-amine (HxA) and for N,N-dimethylformamide (DMF) + aniline. The excess permittivities, εrE, are large and negative for systems with DMA, whereas they are large and positive for the aniline mixture. From the analysis of these εrE data and of measurements previously reported, it is concluded: (i) the main contribution to εrE in systems with linear amines arises from the breaking of interactions between like molecules; (ii) in the DMF + aniline mixture, interactions between unlike molecules contribute positively to εrE, and such a contribution is dominant; (iii) longer linear amines are better breakers of the amide-amide interactions; (iv) interactions between unlike molecules are more easily formed when shorter linear amines, or DMF, participate. These findings are confirmed by a general study conducted in terms of excess values of molar orientational and induced polarizabilities and of the relative Kirkwood correlation factors for systems and components. The ERAS model is also applied to amide + amine mixtures. ERAS represents rather accurately the excess enthalpies and volumes of the mentioned systems. The variation of the cross-association equilibrium constants, determined using ERAS, with the molecular structure is in agreement with that observed for εrE.

Measurement and Modeling the Excess Molar Volumes and Refractive Index Deviations of Binary Mixtures of 2-Propanol, 2-Butanol and 2-Pentanol with N-Propylamine

The densities, ρ, and refractive indices, n D, of 2-alkanols (C3–C5) with N-propylamine have been measured for the whole range of composition at temperatures from (298.15–328.15) K at 10 K intervals and ambient pressure of 81.5 kPa, using an Anton Paar DMA 4500 oscillating tube densimeter and an Anton Paar Abbemat 500 automatic refractometer. From the experimental data, excess molar volumes \( V_{\text{m}}^{\text{E}} \) partial molar volumes \( \bar{V}_{i} \) apparent molar volumes V ϕi and refractive index deviations Δn D the binary systems consisting of N-propylamine + 2-alkanols (2-propanol, 2-butanol, 2-pentanol) were calculated and \( V_{\text{m}}^{\text{E}} \) and Δn D values were correlated with the Redlich–Kister polynomial. The effect of temperature and the chain length of the alcohol on the excess molar volumes and refractive index deviations are discussed in terms of molecular interaction between unlike molecules. The excess molar volumes are negative and refractive index deviations are positive over the entire composition range, which indicates strong hydrogen bonding between molecules of the mixtures. A comparative study has been made of the refractive indices obtained experimentally and those calculated by means of the Lorentz–Lorenz, Weiner and Arago–Biot relations. The perturbed chain statistical associating fluid theory (PC-SAFT), simplified PC-SAFT and Prigogine–Flory–Patterson theory were also applied to correlate and predict the density and excess molar volumes of the mixtures.

Dielectric and FTIR studies on the hydrogen bonded binary system of ester and alcohol

ABSTRACTConcentration dependent dielectric constant, relaxation time, excess dielectric constant, excess inverse relaxation time and the effective Kirkwood correlation factor of the binary mixture of methyl acetate with butanol and pentanol, over the entire mixing range have been determined at room temperature. The values of these functions emphasize on the hydrogen bond interactions between the unlike molecules in ester-alcohols mixtures, the nature of which depends on the extent of substitution of the alcohols. The concentration depending values of excess dielectric constant and excess inverses relaxation time were used to analyze the hydrogen bonding complexes formed between unlike molecules and the strength of the molecular connectivities in the binary mixtures. Conformational analysis of the formation of hydrogen bond is also supported by the FTIR study.

Thermodynamics of amide + ketone mixtures. 2. Volumetric, speed of sound and refractive index data for N,N-dimethylacetamide + 2-alkanone systems at several temperatures. Application of Flory's model to tertiary amide + n-alkanone systems

Data on density, ρ, speed of sound, c, and refractive index, nD, have been reported at (293–303.15) K for the N,N-dimethylacetamide (DMA)+CH3CO(CH2)u−1CH3 (u=1, 2, 3) systems, and at 298.15K for the mixture with u=5. These data have been used to compute excess molar volumes, VmE, excess adiabatic compressibilities, κSE, and excess speeds of sound cE. Negative VmE values indicate the existence of structural effects and interactions between unlike molecules. From molar excess enthalpies, HmE, available in the literature for N,N-dimethylformamide (DMF), or N-methylpyrrolidone (NMP)+n-alkanone systems, it is shown: (i) amide-ketone interactions are stronger in DMF systems than in those with NMP; (ii) they become weaker when u increases in mixtures with a given amide. Structural effects largely contribute toHmE and are more relevant in mixtures containing NMP. The application of the Flory's model reveals that the random mixing hypothesis is valid in large extent for DMF solutions, while NMP systems are characterized by rather strong orientational effects. From values of molar refraction and of the product PintVm (where Pint is the internal pressure and Vm the molar volume), it is concluded that dispersive interactions increase with u, or when DMF is replaced by DMA in mixtures with a fixed ketone.

Changes of refractive indices for Ethanol + Water + (Ethyl Acetate or 1-Pentanol) at 298.15 K

Analysis of different thermodynamic properties as refractive index in multicomponent systems provides valuable information about mixing characteristics in complex media. In this work, the refractive index of the ternary mixtures ethanol + water + (ethyl acetate or 1-pentanol) at 298.15 K and atmospheric pressure, has been measured over the whole concentration range, due to the importance of the latest compounds (ethyl acetate and 1-pentanol) as main trace chemicals in distillated liquors. The obtained experimental values indicate varying extent of interstitial accommodation among unlike molecules on mixing, the steric hindrance of the alkyl chains of ethyl acetate or 1-pentanol being the key factor. Because of the high accuracy technology for refractive index measurements, numerous theoretical/empirical models have been developed in the last few years. An adequate agreement between the measured and predicted values was showed by the tested methods, despite the high non-ideal trend of the studied ternary mixtures.