Binary Liquid Systems Research Articles

Turbidity patterns of spontaneous peptidization in an aqueous abiotic system and possible secondary peptide structures

The non-linear dynamics of spontaneous peptidization running in 10 monocomponent and binary abiotic liquid systems of L- and D-Ala and L- and D-Phe is investigated with use of turbidimetry with continuous registration, high-performance liquid chromatography with light scattering detection (HPLC-ELSD), mass spectrometry (MS), and spectroscopy of far UV circular dichroism (CD). The turbidity patterns represent a sum of the light scattering effects caused by insoluble peptides of unknown yields, structures, and molecular weights. The auxiliary analytical techniques confirm the non-linear nature of peptidization (HPLC-ELSD) and spontaneous formation of the homo- and heteropeptides (MS). CD spectroscopy seems to confirm the presence of the secondary α-helix structures. The similarity of turbidity patterns is revealed with the monocomponent (L or D) and binary (L-L or D-D) systems of equichiral α-amino acids, and dissimilarity of patterns is observed with the binary systems of inequichiral α-amino acids (L-D). The tentative conclusion is drawn that the peptides assembled of equichiral α-amino acid units are able to assume the secondary (right- or left-handed α-helix) structures, which in a certain way could foster the similarity of turbidity patterns, and the peptides built of inequichiral α-amino acid units cannot ensure an efficient enough stringing of monomer molecules into equichiral heptades to form complete segments of an α-helix. This randomness of the α-amino acids arrangement in the inequichiral peptide molecules most probably manifests itself as a lack of similarity among the respective turbidity patterns.

Analytical representation of the concentration dependences of the thermodynamic functions of liquid binary metallic systems with negative deviations from ideal behavior

The application of a number of algebraic expressions for describing the concentration dependences of the thermodynamic functions in liquid binary metallic systems with negative deviations from ideal behavior is considered.

Theoretical Evaluation of Ultrasonic Velocities in the Liquid Binary System of Isomeric Xylenes with Ethyl Lactate

Theoretical Evaluation of Ultrasonic Velocities in the Liquid Binary System of Isomeric Xylenes with Ethyl Lactate

High pressure densities for mixed ionic liquids having different functionalities: 1-butyl-3-methylimidazolium chloride and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide

In this work, high pressure density measurements were made of mixed ionic liquid systems (1-butyl-3-methylimidazolium chloride ([bmim]Cl) and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([bmim][Tf2N])) for the purpose of developing efficient reaction and separation systems for processing biomass. The mixed ionic liquids were prepared at mole ratios, [bmim]Cl:[bmim][Tf2N] of 0.75: 0.25, 0.50: 0.50 and 0.25: 0.75. Density data were measured (10–200MPa, 312–392K) and correlated (up to 100MPa) with the ε∗-modified Sanchez-Lacombe equation of state (ε∗-mod SL EoS). The density of the binary mixed ionic liquid system was modeled in two ways: (i) as a single pseudo-component or (ii) as two discrete components. By treating the mixed ionic liquids as a single pseudo-component, the ε∗-mod SL EoS could correlate the high pressure density data to within a maximum average relative deviation (ARD) of 0.06%. On the other hand, by treating the mixed ionic liquids as discrete components, higher ARD values (0.15%) were obtained from the ε∗-mod SL EoS that can be attributed to the EoS mixing rules. Both approaches for modeling the ionic liquid mixtures had sufficiently low deviations and will be applied to multicomponent CO2-containing systems in future works.

An overview of the performance of the COSMO-RS approach in predicting the activity coefficients of molecular solutes in ionic liquids and derived properties at infinite dilution.

This paper reports a comprehensive evaluation of the conductor-like screening model for real solvents (COSMO-RS) in predicting infinite dilution activity coefficients (γ∞) of molecular solutes in ionic liquids (ILs). In particular, comparative analysis of two quantum chemical levels of calculations used in the COSMO part of COSMO-RS, namely, TZVP-COSMO and TZVPD-FINE, is presented and discussed. The final assessment of the model performance is established based on a comparison of its predictions with the experimental data pool consisting of 41 868 data points extracted form 182 references, covering 233 ILs (including salts belonging to 12 different cationic families) and 150 molecular solutes (including a great variety of non-polar, polar and self-associating organic compounds and water) combined with 8554 distinct binary systems. The impact of the chemical family of both IL and molecular solute on the accuracy of the COSMO-RS predictions is analyzed in terms of both quantitative and qualitative measures. Relevant thermodynamic properties derived from γ∞, namely, infinite dilution partial excess enthalpy of mixing and infinite dilution selectivity are considered and their values obtained from experimental and COSMO-RS predicted γ∞ data are confronted. Finally, the impact of the molecular conformation of cations/anions/solutes on the quality of predictions is demonstrated based on some representative systems.

Electrotransport in binary iron-based metal melts

The mobility of ions in binary iron-based liquid metal systems is calculated for the first time, based on studies on the specific resistance and self-diffusion coefficient in a wide range of concentrations. It is established that iron ions move toward the anode in Fe–V and Fe–Mo systems, and toward the cathode in Fe–W and Fe–Pt systems; i.e., there is inversion of electrotransport for iron ions. When the concentration of a component is reduced, the mobility of its ions grows in modulus.

Prediction of refractive index of binary solutions consisting of ionic liquids and alcohols (methanol or ethanol or 1-propanol) using artificial neural network

In recent years, a new class of solvent called ionic liquids had successfully demonstrated potential applications in industrial chemistry and chemical technology due to its desirable properties. To this end, understanding their physico-chemical properties is of high importance. The current study presents a model for predicting the refractive index of binary ionic liquid system containing alcohol (methanol or ethanol or 1-propanol) using the artificial neural network (ANN) algorithm. The refractive index data were correlated as function of temperature, mole fraction, number of carbon atoms in the cation, number of atoms in the anion, number of hydrogen atoms in the anion and number of carbon atoms in the alcohol. Refractive index data from ThermoIL Database were used. Using ANN, a total of 752 data points were used in the calculation and to obtain the optimum neural network parameters. The 6-6-9-1 neural network architecture was found to be the best network using two hidden layers as shown by mean absolute error of 0.00783 and an overall average percentage error of 0.55%. The obtained correlation satisfactorily represents the experimental refractive index data and can be reliably used to predict the refractive index of other binary systems containing the considered cation and anions and the studied alcohols.

Experimental and computational study of the molecular interactions between 2-chloroaniline and substituted ethanols

The intermolecular interactions between 2-chloroaniline+substituted ethanol binary liquid systems were studied both at the macro- and microscopic levels using a combined experimental and computational methodology. Thermophysical properties of 2-chloroaniline (2CA) and 2-aminoethanol (2AE), 2-chloroethanol (2CE), 2-phenylethanol (2PE) binary mixtures are studied at ambient atmospheric pressure over the entire composition range and at T=(303.15K–318.15K). Excess properties derived from the experimental ones were correlated using Redlich-Kister (RK) equation, for binary mixtures. In the present study the calculated excess properties are discussed in terms of molecular interactions of binary mixtures. The existence of the hydrogen bonding in the binary mixtures of 2-chloroaniline with substituted ethanol's were further conformed by high level theoretical calculation namely, the density functional theory (DFT-B3LYP) of 6-311++G (d, p) basis set was used to study the geometries, bond characteristics, interaction energies and noncovalent interaction plots (NCI) of the hydrogen bonded complexes in gas phase were investigated via quantum chemical calculations.

Viscosities of binary liquid systems: Prediction and correlation

The viscosity of binary liquid systems of 1-Butanol, C 4 H 9 OH with Hexadecane, C 16 H 34 and Squalane, C 30 H 62 , were determined theoretically over the complete concentration range, at 298.15, 303.15, 308.15 K and at atmospheric pressure. Hinds relation and modified Kendall-Monroe method is employed in the calculation. Deviation in viscosity is calculated and the obtained results were analysed in terms of the applied approach, the structure of the investigated system, the nature of components of the binary liquid systems and the interactions in the system.

Thermophysical and spectroscopic properties of binary liquid systems

The thermophysical properties, viz. excess molar volume (V E), viscosity (η), speed of sound (u) and spectroscopic parameter (FT-IR), have been measured for binary mixtures of 3-chloroaniline with acetophenone, cyclopentanone and cyclohexanone over the entire range of mole fraction at T = (303.15–318.15) K. Excess isentropic compressibility ( $$ \kappa_{\text{s}}^{\text{E}} $$ ), deviation in viscosity (Δη) and excess Gibbs energy of activation of viscous flow (G *E) have also been estimated and analyzed. The variation of these properties with composition of the mixtures suggests hydrogen bond, dipole–dipole interactions and charge transfer complex formation between 3-chloroaniline and ketones. The spectroscopic measurement confirms that the interaction between unlike molecules takes place through carbonyl groups of ketones. A good agreement is obtained between excess quantities and spectroscopic data.

Determination of liquid-liquid critical point composition using 90^{∘} laser light scattering.

Despite over a century of characterization efforts, liquid-liquid critical point compositions are difficult to identify with good accuracy. Reported values vary up to 10% for even well-studied systems. Here, a technique is presented for high-precision determination of the critical composition of a partially miscible binary liquid system. Ninety-degree laser light-scattering intensities from single-phase samples are analyzed using an equation derived from nonclassical power laws and the pseudospinodal approximation. Results are reported for four liquid-liquid systems (aniline + hexane, isobutyric acid + water, methanol + cyclohexane, and methanol + carbon disulfide). Compared to other methods, the 90^{∘} light-scattering approach has a strong dependence on composition near the critical point, is less affected by temperature fluctuations, and is insensitive to the presence of trace impurities in the samples. Critical compositions found with 90^{∘} light scattering are precise to the parts-per-thousand level and show long-term reproducibility.

Effect of the hockey-shaped mesogen as an additive on the critical behaviour at the smectic A to nematic phase transition

We present systematic experimental data on high resolution measurements of temperature dependence of optical birefringence (Δn) in a binary liquid crystalline system comprising calamitic 4-cyano-4′-octyloxybiphenyl (8OCB) and a hockey stick-shaped compound, 4-(3-decyloxyphenyliminomethyl) phenyl 4-decyloxycinnamate (SF7). The hockey stick-shaped mesogen shows a smectic A (SmA) phase in addition to two polymorphic tilted smectic phases. From an analysis of the Δn data, a quotient Q(T) has been derived which exhibits power law divergences both above and below the smectic A-nematic (SmA-N) phase transition. A noticeable shrinkage in width of the nematic range has been observed for a small increase in concentration of the angular mesogenic dopant. In the vicinity of the SmA-N phase transition, the values of effective critical exponent (α′), characterizing the critical fluctuation at this transition, have appeared to be in between those predicted by the 3D-XY and tricritical hypothesis. Furthermore, with increasing hockey stick-shaped molecular concentration, the SmA-N transition shows a tendency to be driven towards a first order nature.

Thermodynamic properties of binary liquid systems of ethanoic acid, propanoic acid, and butanoic acid with 3-chloroaniline as a function of various temperatures

The densities (ρ) and viscosities (η) are reported for binary mixtures of 3-chloroaniline with carboxylic acids such as ethanoic acid, propionic acid and butanoic acid over the entire range of mole fractions at T = (303.15–318.15) K and at constant atmospheric pressure. The excess properties such as excess volume and deviation in viscosity are calculated from the density and viscosity data. Excess properties are correlated by the Redlich–Kister equation. The variations of these properties with the composition of binary mixtures suggest the loss of dipolar association, difference in size and shape of the component molecules, dipole–dipole interactions and hydrogen bonding between unlike molecules.

Prediction of mutual diffusion coefficients in binary liquid systems with one self-associating component from viscosity data and intra-diffusion coefficients at infinite dilution

A new model for prediction of mutual diffusion coefficients is proposed over the whole composition range for binary liquid systems of one self-associating component and one non-polar component. The model is based on the Darken equation with the knowledge of intra-diffusion coefficients at infinite dilution of both species and viscosity data for the system, and takes into account the cluster diffusion approach with a scaling power on the thermodynamic correction factor. The model was validated to show good concurrence with the experimental mutual diffusion data. Following the analysis that the mutual diffusion coefficients at infinite dilution can be identified with the molecular intra-diffusion coefficient of the species (i.e., the intra-diffusion coefficient at infinite dilution in the absence of self-association), the proposed equation was extended to binary liquid systems without significant association. The accuracy of prediction for systems of cross associating species is expected to be limited. The model relies on the knowledge of the viscosity of the mixture over the whole composition range and may be used as a valid alternative to models based on measuring intra-diffusion coefficients as a function of composition. Indeed, such data are not always available or are more difficult to obtain whereas viscosity measurements can be readily available and more easily measured.

English

English

Thermodynamic properties of n-methylformamide + short carboxylic acids as a function of temperature

Density, viscosity and speed of sound of three binary liquid systems: N-methylformamide (N-MFA) with carboxylic acids (ethanoic acid, propanoic acid and butanoic acid) have been determined at T = (303.15–318.15) K over the entire composition range. These experimental data have been used to calculate the excess volume (VE), excess isentropic compressibility (κsE), deviation in viscosity (Δη) and excess Gibbs free energy of activation of viscous flow (G∗E). The variations of these properties with composition of binary mixtures suggest loss of dipolar association, difference in size and shape of the component molecules, dipole–dipole interactions and hydrogen bonding between unlike molecules. The viscosity data have been correlated with Grunberg and Nissan, Katti and Chaudhri, and Hind et al. equations and the results are compared with the experimental results. The excess parameters have been fitted to the Redlich–Kister polynomial equation using multi parametric nonlinear regression analysis to derive the binary coefficients and to estimate the standard deviation.

Thermophysical and spectroscopic properties of binary liquid systems: acetophenone/cyclopentanone/cyclohexanone with N-methylformamide

ABSTRACTThe intermolecular interactions in the binary liquid systems of N-methylformamide with acetophenone and cyclic ketones (cyclopentanone and cyclohexanone) were studied with combined experimental and computational methodology. The speed of sound (u), density (ρ) and viscosity () values are measured for binary mixtures of N-methylformamide with ketones over the entire range of mole fraction at temperatures (T) of 303.15–318.15 K, at atmospheric pressure. From the experimental results, the values of excess molar volume (VE), excess isentropic compressibility (κsE), deviation in viscosity (Δη) and excess Gibbs free energy of activation of viscous flow () are evaluated. The experimental results indicate an intermolecular association between the binary liquid mixtures. Furthermore, the nature of the hydrogen bond of the associated complexes is further confirmed by high-level theoretical calculations. The structures, interactional energies and natural bonding orbital analysis of the hydrogen-bonded complex have been calculated in the gas phase using the density functional theory method at the B3LYP/6-311++G (d, p) level.

STUDY OF MOLECULAR INTERACTION IN CERTAIN BINARY AND TERNARY LIQUID SYSTEM S BY EXPOSING IT TO ULTRASONIC FREQUENCY OF 2 MHZ AT 293.15 K

The essential frame work of manufacturing material is composed of scientific and practical interrelationship. It plays the role among the structure, structural properties and performance of all classes of materials that are potentially useful to the society. Even after manufacturing the materials further it is necessary to study the physical and chemical properties of those materials. One of such properties can be studied by exposing the liquid or solid materials to ultrasonic vibrations .In the liquid binary system chosen for this study is toluene with benzene, hexane, heptane and cyclohexane at temperature i.e. 293.15K. The experimental value of ultrasonic velocity and density of binary mixtures are taken from the work of P.S.Nikam etal’ and the sample chosen is mainly due to the availability of the experimental data. The various acoustical parameters like ultrasonic velocity, percentage deviation, excess impedance, and excess velocity are calculated and obtained results are suitably interpreted. The ternary system chosen for this study are cyclohexane plus toluene plus 2-propanol, studied at 293.15K.The experimental value of ultrasonic velocity and density for this mixture has been taken from the work of G. Arul etal. The values of sound velocity have been evaluated theoretically using three different methods namely Nomoto, Van-deal and CFT. For both binary and ternary mixtures, the observed result shows that the Nomoto method seems to give good results for the evaluation of acoustical parameters compared to collision factor theory (CFT) and Van-deal’s method.

Excess properties and spectral studies for binary system tri-ethylene glycol + dimethyl sulfoxide

Density and viscosity of the binary liquid system, tri-ethylene glycol (TEG)+dimethyl sulfoxide (DMSO), were studied over the whole composition range at T=(293.15, 298.15, 303.15, 308.15, 313.15 and 318.15) K under a pressure of 0.1MPa. Based on these density and viscosity data, their excess molar volume (VmE), viscosity deviation (Δη), apparent molar volumes (Vφ,1 and Vφ,2) and partial molar volumes (V_1 and V_2) were determined, respectively. Their VmE and Δη values were then fitted to a Redlich–Kister equation to obtain the coefficient and the standard deviation. Additionally, the intermolecular interaction, obtained from FTIR and UV–Vis, indicated that hydrogen bonding between hydroxyl hydrogen atom in TEG and oxygen atom in DMSO was formed.

Calorimetric measurements of liquid (Al + Li + Zn) alloys

The integral molar enthalpies of mixing are described by drop calorimetry for liquid alloys based on the (Al+Li) and (Al+Li+Zn) system, with the use of the Setaram MHTC 96 Line Evo calorimeter.The measurements for the (Al+Li) system were carried out at two temperatures, 1023K and 1027K, and compared with the literature data. The integral molar enthalpies of mixing of the liquid binary system over the entire concentration range have negative values. Moreover, for the mole fraction of lithium (XLi=0.5053), the minimum value of the integral enthalpy of mixing of the (Al+Li) system is equal to ΔmixHm=−12.1kJ·mol−1.The experimental studies for the (Al+Li+Zn) system involved measurements at three different temperatures: 942K for the (Al0.90Li0.10)1−xZnx alloy composition; 978K for the (Al0.35Li0.65)1−xZnx and (Al0.65Li0.35)1−xZnx alloy composition and finally, 1014K for the (Al0.50Li0.50)1−xZnx alloy composition.This work presents a complete study of mixing enthalpies in (Al+Li) and (Al+Li+Zn) systems and may therefore provide reference for earlier attempts on calorimetric measurements of the (Al+Li+Zn) system.