Excess Molar Refraction Research Articles

Isothermal Vapor−Liquid Equilibrium at 333.15 K and Excess Volumes and Molar Refractivity Deviation at 298.15 K for Binary System Dibutyl Ether (DBE) + 2,2,4-Trimethylpentane and for Ternary System DBE + Ethanol + 2,2,4-Trimethylpentane

Isothermal vapor−liquid equilibrium (VLE) data are reported for the binary system dibutyl ether (DBE) + 2,2,4-trimethylpentane at 333.15 K, as well as for the ternary system DBE + ethanol + 2,2,4-trimethylpentane using headspace gas chromatography. The experimental binary and ternary VLE data are correlated with common activity coefficient models. Excess volumes and deviations in molar refractivity data are also reported for the same binary and ternary systems at 298.15 K. These properties are correlated with the Redlich−Kister equation for binary systems and the Cibulka equation for ternary systems, respectively. The ternary excess volumes and deviations in molar refractivity data are also compared with the estimated values from the binary contribution models of Radojkovič, Tsao−Smith, Kohler, and Rastogi.

Density, Speed of Sound, and Refractive Index of 1-Ethyl-3-methylimidazolium Trifluoromethanesulfonate with Acetone, Methyl Acetate, and Ethyl Acetate at Temperatures from (278.15 to 328.15) K

Densities, speeds of sound, and refractive indices of the binary mixtures of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([emim][triflate]) with acetone, methyl acetate, and ethyl acetate were experimentally measured over the whole range of compositions at T = (278.15 to 328.15) K and a pressure of 0.1 MPa. From these experimental data, excess molar volumes, excess isentropic compressibilities, molar refractions, and deviations in refractive indices have been calculated and fitted to an extended version of the Redlich−Kister equation, which takes into account the dependence on composition and temperature simultaneously. The Prigogine−Flory−Patterson theory has been used to speculate on the cause of the volumetric variations for these mixtures.

Density and refractive index in binary mixtures of triethylamine–water in the temperature interval (283.15–291.35) K

Densities ρ, refractive indices n, excess molar volumes VE , refractive index deviations Δn, molar refractions Rm and excess molar refractions ΔRm were determined over the full range of compositions for the triethylamine–water binary mixture. The experimental measurements of these properties were carried out at atmospheric pressure and temperatures ranging from 283.15 to 291.35 K. The excess molar volumes VE , excess molar refractions ΔRm and refractive index deviations Δn have been fitted to the fourth-order Redlich–Kister polynomial equation. These quantities have been discussed in terms of intermolecular interactions between the compounds of the mixtures. Refractive indices were compared with those predicted using several mixing rules.

Prediction of biomagnification factors for some organochlorine compounds using linear free energy relationship parameters and artificial neural networks

Multiple linear regression and artificial neural networks (ANNs) as feature mapping techniques were used for the prediction of the biomagnification factor (BMF) of some organochlorine pollutants. As independent variables, or compound descriptors, the Abraham descriptors often employed in linear free energy relationships were used. Much better results were obtained from the nonlinear ANN model than from multiple linear regression. The average absolute error, average relative error and root mean square error in the calculation of log (BMF) by the ANN model were 0.055, 0.051 and 0.097 for the training set and 0.11, 0.086 and 0.175 for the internal validation set, respectively. The degree of importance of each descriptor was evaluated by carrying out a sensitivity analysis approach for the nonlinear model. The results obtained reveal that the order of importance is the pollutant volume, the pollutant dipolarity/polarizability and the pollutant excess molar refraction. In order to examine the credibility of the obtained ANN model the leave-many-out cross-validation test was applied which gave Q 2= 0.827 and SPRESS = 0.15. Also the Y-scrambling procedure was applied to the ANN model in order to examine the effect of chance correlations. The results obtained reveal that it is possible to predict the BMFs of organochlorine pollutants using a nonlinear ANN model with Abraham descriptors as inputs.

Characterization of biopartitioning micellar chromatography system using monolithic column by linear solvation energy relationship and application to predict blood–brain barrier penetration

The linear solvation energy relationship (LSER) was applied to characterize biopartitioning micellar chromatography (BMC) system using monolithic column, and was utilized to compare the above system with other physicochemical and biological processes in this study. The solute volume and HB basicity had the maximum influence on the retention of the solutes, and an increase in the dipolarity/polarizability, HB basicity, HB acidity or excess molar refraction of the solutes decreased the retention. Principal component analysis of LSER coefficients showed that the system had certain similarity to drug biomembrane transport processes, such as blood–brain barrier penetration, transdermal and oral absorption. The quantitative retention–activity relationship (QRAR) of drug penetration across blood–brain barrier was established and its predictive capability for this biological process was evaluated. With the aid of the high flow rate, the monolithic column significantly facilitated the high-throughput analysis of large compounds’ bank without changing the mechanism of the retention in BMC and without impairing good predictive capability of the biological processes. Accordingly, the BMC system, together with monolithic column, allows for high-throughput profiling the biological processes, such as blood–brain barrier penetration.

Physical and transport properties of aqueous amino alcohol solutions for CO 2 capture from flue gas streams

Densities, viscosities and refractive indices of 4-diethylamino-2-butanol + water mixtures were measured over the entire concentration range of 0–1 mole fraction and temperature range from 298.15 to 343.15 K. Excess molar volumes, viscosity deviations, and molar refraction changes were calculated from the measurement results and correlated as a function of the mole fractions. Various models were used for correlation with the measured data. Out of these, the Redlich–Kister equation was the most suitable model that correlated best with experimental data. The percent absolute deviations obtained with this model were 0.03% for density, 0.88% for viscosity and 0.009% for refractive index.

Refractive Index and Density Measurements for Selected Binary Protic‐Protic, Aprotic‐Aprotic, and Aprotic‐Protic Systems at Temperatures from 298.15 K to 308.15 K

AbstractThe refractive indices (n) and the densities (ρ) of: (1) protic‐protic solvent mixtures (methanol‐ethanol, methanol‐porpanol, methanol‐butanol and ethanol‐water), (2) aprotic‐aprotic solvent mixtures (acetonitrile‐dimethylformamide, acetonitrile‐dimethylsulphoxide, and acetonitrile‐1,4‐dioxane) and (3) aprotic‐protic solvent mixtures (dimethylformamide, acetonitrile with water and some aliphatic alcohols) were measured experimentally at different temperatures (25, 30 and 35 °C). From the values of the measured refractive indices and densities, the excess refractive indices (nE), molar refractions (R), atomic polarization (PA), molar volumes (V), solvated radii (r) and polarizabilities (α) of the mixed solvents were calculated.The results show that the solvent‐solvent interaction reaches maximum value at a definite mole fraction (x) of each solvent depending on its nature. Also, the excess refractive indices, densities and atomic polarizations are found to decrease as the temperature increases. On the other hand, the molar volumes, solvated radii, molar refractions and polarizabilities are found to increase as the temperature increases.

Isothermal vapor–liquid equilibrium at 333.15 K and excess volumes and molar refractivity deviation at 298.15 K for the ternary system di-butyl ether (1) + ethanol (2) + toluene (3) and its binary subsystems

Isothermal vapor–liquid equilibrium data at 333.15 K are reported for the ternary system di- n-butyl ether (DBE) + ethanol + toluene and for its subbinary subsystems DBE + toluene and ethanol + toluene by using headspace gas chromatography. The experimental ternary VLE data were correlated with the Wilson, NRTL and UNIQUAC models, and the binary VLE data were correlated with the same models. The excess molar volumes ( V E) and deviations in molar refractivity (Δ R) at 298.15 K for the same ternary and binary systems were also determined from measured densities ( ρ) and refractive indices ( n D). The experimental V E and Δ R data of the ternary system are correlated with Cibulka equation and the binary data were correlated with the Redlich–Kister equation. The ternary V E and Δ R are additionally compared with estimated values using the contribution models of Tsao–Smith, Kohler, Rastogi and Radojkovic.

Distribution model for Folch partition

Partition coefficients for 86 varied compounds were determined for the chloroform-methanol-water (8:4:3 v/v) biphasic partition system and used to derive a model for the distribution of neutral compounds between the water-rich and chloroform-rich layers. The partition coefficients, log K(p), were correlated through the solvation parameter model giving log K(p) = 1.336 - 0.014E + 0.413S + 1.583A + 1.344B - 1.378V with a multiple correlation coefficient of 0.973, standard error of the estimate 0.151, and Fischer statistic 286. In the model the solute descriptors are excess molar refraction, E, dipolarity/polarizability, S, overall hydrogen-bond acidity, A, overall hydrogen-bond basicity, B, and McGowan's characteristic volume, V. The model is expected to be able to estimate further values of the partition coefficient to about 0.13 log units. The chloroform-methanol-water partition system is shown to have different selectivities to 44 common water-organic solvent and totally organic biphasic partition systems.

Comparative study of solvation parameter models accounting the effects of mobile phase composition in reversed-phase liquid chromatography

Solvation parameter models relate linearly compound properties with five fundamental solute descriptors (excess molar refraction, dipolarity/polarizability, effective hydrogen-bond acidity and basicity, and McGowan volume). These models are widely used, due to the availability of protocols to obtain the descriptors, good performance, and general applicability. Several approaches to predict retention in reversed-phase liquid chromatography (RPLC) as a function of these descriptors and mobile phase composition are compared, assaying the performance with a set of 146 organic compounds of diverse nature, eluted with acetonitrile and methanol. The approaches are classified in two groups: those that only allow predictions of retention for the mobile phases used to build the models, and those valid at any other mobile phase composition. The first group includes the use of ratios between the regressed coefficients of the solvation models that are assumed to be characteristic for a column/solvent system, and the application of offsets to transfer the retention from a reference mobile phase to any other. Maximal accuracy in predictions corresponded, however, to the approaches in the second group, which were based on models that describe the retention as a function of mobile phase composition (expressed as the solvent volume fraction or a normalised polarity measurement), where the coefficients were made dependent on the solvent descriptors. The study revealed the properties that influence the retention and distinguish the particular behaviour of acetonitrile and methanol in RPLC.

Mathematical correlation of salicylamide solubilities in organic solvents with the Abraham solvation parameter model

The Abraham solvation parameter model is used to calculate the numerical values of the solute descriptors for salicylamide from experimental solubilities in organic solvents. The mathematical correlations take the form of where C S and C W refer to the solute solubility in the organic solvent and water, respectively, C G is a gas phase concentration, E is the solute excess molar refraction, V is McGowan volume of the solute, A and B are measures of the solute hydrogen-bond acidity and hydrogen-bond basicity, S denotes the solute dipolarity/polarizability descriptor, and L is the logarithm of the solute gas phase dimensionless Ostwald partition coefficient into hexadecane at 298 K. The remaining symbols in the above expressions are known solvent coefficients, which have been determined previously for a large number of gas–solvent and water–solvent systems. The Abraham solvation parameter model was found to describe the available experimental solubility, partition coefficient, chromatographic retention and toxicity data of salicylamide within an overall SD of 0.091 log units.

Distribution of neutral organic compounds between n-heptane and fluorine-containing alcohols

Partition coefficients for a number of varied compounds were determined for n-heptane-2,2,2-trifluoroethanol and n-heptane-1,1,1,3,3,3-hexafluoro-2-propanol and used to derive a general model for the distribution of neutral compounds in the biphasic systems. The partition coefficient, logKp, was correlated through the solvation parameter model giving logKp=0.160+1.190V+0.856E−1.538S−1.325A−2.965B for the n-heptane-2,2,2-trifluoroethanol system with a multiple correlation coefficient of 0.988, standard error of the estimate 0.136, and Fischer statistic 599 for 77 compounds. For n-heptane-1,1,1,3,3,3-hexafluoro-2-propanol, the model is logKp=−0.225+1.161V+0.720E−1.357S−0.577A−2.819B with a multiple correlation coefficient of 0.982, standard error of the estimate 0.148, and Fischer statistic 421 for 84 compounds. In the models, the solute descriptors are excess molar refraction E, dipolarity/polarizability S, overall hydrogen bond acidity and basicity A and B, respectively, and McGowan's characteristic volume V. Either model is expected to be able to estimate further values of the partition coefficient to about 0.13log units and is applicable to a wide range of compounds. Applications include the choice of partitioning systems for sample clean-up and countercurrent chromatography and for estimating solute descriptors for water insoluble or reactive compounds.

Insights into the Retention Mechanisms on Perfluorohexylpropylsiloxane-Bonded (Fluophase-RP) and Octadecylsiloxane-Bonded (Betasil C18) Stationary Phases Based on the Same Silica Substrate in RP-LC

The solvation parameter model is used to elucidate the retention mechanism on a perfluorohexylpropylsiloxane-bonded (Fluophase RP) and octadecylsiloxane-bonded (Betasil C18) stationary phases based on the same silica substrate with acetonitrile–water and methanol–water mobile phase compositions. Dewetting affects the retention properties of Fluophase RP at mobile phase compositions containing less than 20% (v/v) acetonitrile or 40% (v/v) methanol. It results in a loss of retention due to an unfavorable change in the phase ratio as well as changes in specific intermolecular interactions. Steric repulsion reduces retention of bulky solutes on fully solvated Betasil C18 with methanol–water (but not acetonitrile–water) mobile phase compositions but is not important for Fluophase RP. The retention of weak bases is affected by ion-exchange interactions on Fluophase RP with acetonitrile–water, and to a lesser extent, methanol-water mobile phases but these are weak at best for Betasil C18. The system constants of the solvation parameter model and retention factor scatter plots are used to compare selectivity differences for Fluophase RP, Betasil C18 and a perfluorophenylpropylsiloxane-bonded silica stationary phase Discovery HS F5 for conditions where incomplete solvation, steric repulsion and ion-exchange do not significantly contribute to the retention mechanism. Lower retention on Fluophase RP results from weaker dispersion and/or higher cohesion moderated to different extents by polar interactions since solvated Fluophase RP is a stronger hydrogen-bond acid and more dipolar/polarizable than Betasil C18. Retention factors for acetonitrile–water mobile phases are highly correlated for Fluophase RP and Betasil C18 except for compounds with a large excess molar refraction and weak hydrogen-bonding capability. Selectivity differences are more significant for methanol–water mobile phases. Retention factors on Fluophase RP are strongly correlated with those on Discovery HSF5 for acetonitrile–water mobile phases while methanol–water mobile phases retention on Fluophase RP is a poor predictor of the retention order on Discovery HS F5.

Solvation parameter models for retention on perfluorinated and fluorinated low temperature glassy carbon stationary phases in reversed-phase liquid chromatography

The retention of solutes on two fluorinated low temperature glassy carbon (F-LTGC) stationary phases under reversed-phase liquid chromatographic conditions was studied by employing the solvation parameter model. The two fluorinated glassy carbon stationary phases were produced by slowly heating zirconia particles that were encapsulated with oligo[1,3-dibutadiyne-1,3-(tetrafluoro)phenylene] precursor polymer to two different final temperatures (200 and 400 °C). The resulting carbon particles had different amounts of fluorine after thermal processing. The solvation parameter models indicated that different intermolecular interactions are important in describing retention on the two stationary phases. The interactions that are important for describing retention on the 200 °C processed F-LTGC stationary phase are hydrogen bond basicity ≥ dispersion > hydrogen bond acidity > dipolarity/polarizability. The interactions that describe the retention on the 400 °C processed F-LTGC are hydrogen bond basicity > dispersion > excess molar refraction ≥ hydrogen bond acidity. The solvation parameter model for the 200 °C processed F-LTGC showed similar trends in the relative importance of intermolecular interactions as previously found for octadecyl-polysiloxane stationary phases, while the 400 °C processed F-LTGC had similar intermolecular interactions with solutes as found with porous glassy carbon in that π–π interactions with the carbon surface contribute more so to the retention.

Distribution of neutral organic compounds betweenn-heptane and methanol orN,N-dimethylformamide

Partition coefficients for a number of varied compounds were determined for the n-heptane-methanol and n-heptane-DMF partition systems and used to derive a general model for the distribution of neutral compounds in the biphasic systems. The partition coefficient, log Kp, was correlated through the solvation parameter model giving log Kp = -0.056 + 0.164E-0.620S-1.337A-0.957B + 0.507V for the n-heptane-methanol system with a multiple correlation coefficient of 0.986, standard error of the estimate 0.086, and Fischer statistic 413 for 65 compounds. For n-heptane-DMF, the model is log Kp = 0.065 + 0.030E-1.405S-2.039A-0.806B + 0.721V with a multiple correlation coefficient of 0.991, standard error of the estimate 0.080, and Fischer statistic 560 for 59 compounds. In the models the solute descriptors are excess molar refraction E, dipolarity/polarizability S, overall hydrogen bond acidity, and basicity A and B, respectively, and McGowan's characteristic volume V. Either model is expected to be able to estimate further values of the partition coefficient to about 0.08 log units and is applicable to a wide range of compounds. Applications include the choice of partitioning systems for sample clean-up, countercurrent chromatography, and estimation of solute descriptors for water insoluble or unstable compounds.

Mathematical correlation of 1-chloroanthraquinone solubilities in organic solvents with the Abraham solvation parameter model

The Abraham solvation parameter model is used to calculate the numerical values of the solute descriptors for 1-chloroanthraquinone from experimental solubilities in organic solvents. The mathematical correlations take the form of where C S and C W refer to the solute solubility in the organic solvent and water, respectively, C G is a gas phase concentration, E is the solute excess molar refraction, V is McGowan volume of the solute, A and B are measures of the solute hydrogen-bond acidity and hydrogen-bond basicity, S denotes the solute dipolarity/polarizability descriptor, and L is the logarithm of the solute gas phase dimensionless Ostwald partition coefficient into hexadecane at 298 K. The remaining symbols in the above expressions are known solvent coefficients, which have been determined previously for a large number of gas/solvent and water/solvent systems. The Abraham solvation parameter model was found to describe the experimental solubility data of 1-chloroanthraquinone to within an overall standard deviation of 0.126 log units.

Mathematical correlation of phenothiazine solubilities in organic solvents with the Abraham solvation parameter model

The Abraham solvation parameter model is used to calculate the numerical values of the solute descriptors for phenothiazine from experimental solubilities in organic solvents. The mathematical correlations take the form of where C S and C W refer to the solute solubility in the organic solvent and water, respectively, C G is a gas phase concentration, E is the solute excess molar refraction, V is McGowan volume of the solute, A and B are measures of the solute hydrogen-bond acidity and hydrogen-bond basicity, S denotes the solute dipolarity/polarizability descriptor, and L is the logarithm of the solute gas phase dimensionless Ostwald partition coefficient into hexadecane at 298 K. The remaining symbols in the above expressions are known solvent coefficients, which have been determined previously for a large number of gas/solvent and water/solvent systems. The Abraham solvation parameter model was found to describe the experimental solubility data of phenothiazine within an overall standard deviation of 0.094 log units.

Volumetric Properties, Viscosities, and Refractive Indices for Aqueous 2-((2-Aminoethyl)amino)ethanol Solutions from (298.15 to 343.15) K

Densities and viscosities at six temperatures in the range (298.15 to 343.15) K and refractive indices at five temperatures in the range (298.15 to 333.15) K are reported for the aqueous 2-((2-aminoethyl)amino)ethanol solutions. Excess molar volumes, viscosity deviations, and molar refraction changes are calculated from the measurement results and correlated as a function of the mole fractions. Partial molar volumes at infinite dilutions are determined from apparent molar volumes. Negative values for both excess molar volumes and molar refraction changes are observed over the entire range of mole fractions, whereas viscosity data exhibit both negative and positive deviations.

Partitioning properties of linear and branched ethers: Determination of linear solvation energy relationship (LSER) descriptors

Solute descriptors of linear solvation energy relationship (LSER) for dialkyl ethers were examined as a means for improving predictions of their fate and behavior in the environment. LSER solute descriptors consist of the excess molar refraction, the polarizability/dipolarity parameter, the effective hydrogen (H)-bond acidity/basicity, McGowan's characteristic volume and the hexadecane–air partitioning coefficient. Descriptor determination was done based on partitioning coefficients measured in this study for six alkyl ethers including linear and branched compounds. Calibration of the solute descriptors revealed that the effective solute H-bond basicity of branched ethers is significantly higher than that of linear ethers, which has been neglected in previous LSER studies. Revised solute descriptors accurately calculated measured partitioning coefficients in most systems. The inspection of solute H-bond basicities of ethers in different solvent–water and solvent–air systems suggested that the H-bond basicity of an ether can vary depending on the solvent in which the ether dissolves. Neglecting this donor-dependency of the H-bond basicity could lead to significantly poorer estimations by the LSER, when the solvent or sorbent of concern is a strong H-bond acid. Other H-bond basic compounds possibly pose a donor-dependent basicity as well.

Mathematical correlation of 1,2,4,5-tetramethylbenzene solubilities in organic solvents with the Abraham solvation parameter model

The Abraham solvation parameter model is used to predict the experimental solubilities of 1,2,4,5-tetramethylbenzene in organic solvents, from the correlation equations, below, and already determined descriptors for 1,2,4,5-tetramethylbenzene. The mathematical correlations take the form of where C s and C w refer to the solute solubility in the organic solvent and water, respectively, C G is a gas phase concentration, E is the solute excess molar refraction, V is McGowan volume of the solute, A and B are measures of the solute hydrogen-bond acidity and hydrogen-bond basicity, S denotes the solute dipolarity/polarizability descriptor, and L is the solute gas phase dimensionless Ostwald partition coefficient into hexadecane at 298 K. The remaining symbols in the above expressions are known solvent coefficients, which have been determined previously for a large number of gas/solvent and water/solvent systems. The Abraham solvation parameter model was found to predict the experimental solubility data of 1,2,4,5-tetramethylbenzene to within an overall standard deviation of 0.15 log units.