Solute Solvent Interaction Parameters Research Articles

Spectral characterization, solvation effects on topological aspects, and biological attributes of Fmoc-L-glutamic acid 5‑tert‑butyl ester: An effective reagent in anticancer evaluations

In this study, the solvation effects, structural characterization, and biological properties of the Fmoc-L-glutamic acid 5-tert-butyl ester (Fmoc-L-Glu(OtBu)) were described with experimental (UV–Vis, FT-IR, and FT-Raman,) and DFT techniques. The topological analysis of the compound was done in order to ensure that self-assembled forces (weak non-bonded contacts) existed between the chemical functionalities (carbonyl, amine, carboxylic acid, & hydroxyl) in the solution phases. The spectral techniques were utilized to assess the compound structure as well as the relationship between potential energy distribution and structural properties. The chemical reactivity has been discussed in terms of Molecular electrostatic potential, FMOs, and Fukui function analyses. Also, the stability and optical properties of the chemical were computationally obtained by NBO and NLO studies. The highest electron transferability of molecular orbitals was examined through UltraViolet-Visible absorptions spectra of Fmoc-L-Glu(OtBu). The effects of polar and non-polar solvents on the title molecule were also detailed using the solute-solvent interaction parameters. The chemical's biological functions were investigated further via molecular docking with cancer cell proteins.

Solvation and Solvatochromism: An Overview#

Different examples of solvatochromic shifts are shown and the theory that explain the non-specific general solvent effects are discussed here. The use of solvatochromic shifts for the determination of excited state dipole moment has been presented in detail in connection with a brief overview of different solvent polarity functions. The lack of proper theoretical expressions to explain the specific solvent effect stimulates to introduce the concept of “empirical measures of solvent polarity”, based on well known, convenient, solvent sensitive model processes. Various solvent sensitive polarity probes are discussed in this context. So far as quantitative estimation of various parameters responsible for the observed solvatochromic shifts are concerned, introduction of multiparameter approaches, its application in recent years has been carefully analyzed. The review also focuses some of the recent developments on the theoretical calculations of various solute-solvent interaction parameters based on quantum mechanical approaches. This issue solvation interaction by the use of mixed solvents has been discussed in detail, starting from the early development of the theories related to preferential solvation to the recent scenario, with a critical survey on the application of the concept of preferential solvation in the solubilization of drugs, polymers considering the emerging ‘green approach’ in recent years.

Viscosity and Related Quasi Thermodynamic Properties of Alkali Metal Salts In 10%(W/W) 2-(Ethoxy) Ethanol - Water Mixture

Relative viscosities of NaCl, KCl, KBr, RbCl, KI in 10% (W/W) 2-(Ethoxy) ethanol - water mixture are measured at 30o , 35o and 40oC. Joules-Dole equation is used to analyze the data to calculate B-coefficients. Transition state theory is applied to calculate Enthalpy activation of viscous flow ( H-20# ) and entropy of activation of viscous flow ( S20# ). The temperature coefficients of ( H20# ) , ( S2 0 #) and B-coefficients show that in the present solvent system Na+ is a structure making ion while K+. Rb+, Cl-, Br-, I- are structure breaking ions. An attempt is made to split the enthalpy and entropy values of the electrolytes into their ionic contributions. Solute-solvent interaction parameter ( ) , solvation numbers and ionic volumes are also calculated. These values support the conclusions drawn from H-20# and S20# . Dimensions of the ions are calculated from the viscosity B-coefficients and are compared with Pauling’s crystal radius of the ions.

A simple model for prediction of dipole moments of isolated molecules

A method for determination of molecular dipole moments (DMs) by extrapolation of the values measured in a series of selected solvents is proposed. The DM values of 26 organic compounds are calculated. Most of the compounds cannot be studied in the vapor phase. A discrete–continuum solvation model is applied to investigate the influence of solvent nature on solubility of the compounds under investigation. It is shown that universal interactions between the solvent and solute molecules, including the dispersive, inductive, and dipole–dipole interactions, dominate the solvation process. Analytic expressions describing the dependences of the solvent induced changes of the DM values on the solute–solvent interaction parameters are obtained for nonpolar and polar solvents.

Quantifying the Solubility of Boron Nitride Nanotubes and Sheets with Static Light Scattering and Refractometry

The dissolution of nanoparticles, particularly those containing boron, is an important area of interest for polymer nanocomposite formation and material development. In this work, the solubility of boron nitride nanotubes (BNNT), functionalized boron nitride nanotubes (FBNNT), and boron nitride sheets (BN-ZG) is quantified in toluene and THF with static light scattering, refractometry, UV–vis spectroscopy, and physical observations. UV–vis spectroscopy provides a method to determine the concentration and solubility limits of the solutions tested. Using light scattering, the second virial coefficient, A2, is determined and used to calculate χ, the solute–solvent interaction parameter. The Hildebrand solubility parameter, δ, is then extracted from this data using the Hildebrand–Scatchard Solution Theory. A list of potential good solvents based on the estimated δ value is provided for each nanoparticle. Single-walled carbon nanotubes (SWNTs) and prepolymers (EN4 and EN8) used to synthesize polyurethanes were...

Differential Hydration Induced Coil-Sphere Transition of Gelatin Chains in Binary Liquid Solutions

Specific hydration induced coil-globule transition in gelatin-B(GB) chain, a polypeptide, in ethanol, ethylene glycol and glycerol solutions (organo-solutions) was studied by Raman spectroscopy, viscosity and dynamic light scattering techniques to map its differential hydration behavior in mono, di and tri-ol solutions (alcohols are non-solvents for this polypeptide). The chain stiffness, determined from the hydrodynamic radius to radius of gyration ratio Rg/Rh, was estimated to be around 0.67 in water which was found to be dependent on the nature of alcohol and its concentration. This clearly attributed same random coil conformation to GB in all thesolutions at low alcohol concentration, but chain collapse to a near-globular shape (Rg/Rh=0.77) was observed when alcohol concentration was increased which was found to occur in glycerol at ≈ 60% (v/v), in ethylene glycol at ≈ 35% and in ethanol at ≈ 40% (v/v) concentrations consistence with the intrinsic viscosity data. The Huggins (KH) and Kraemer (KK) solute-solvent interaction parameter determined from the concentration dependence plot of relative viscosity revealed poorer interaction between GB and organo-solvents with increase in concentration of the organic phase. Differential chain hydration was evaluated from characteristic Raman active modes of water molecule. Three signatures Raman peaks were observed at 3200, 3310, and 3460 cm-1 specific to structured, partially structured and amorphous water respectively. The peak at 3310 cm-1 was observed to decrease with alcohol concentration while the peak at 3200 cm-1 was observed to increase indicating the increase in the water structure in all the solutions and depletion of water density near the first hydration sheath of the protein molecule which caused GB chain to collapse.

Quantifying the thermodynamic interactions of polyhedral boranes in solution to guide nanocomposite fabrication

The solubility of boron containing nanoparticles in a variety of solvents is quantified using static light scattering in conjunction with refractometry. Four polyhedral boranes were tested in this work, using refractometry to obtain dn/dc, while static light scattering quantifies A2. A2 obtained from these measurements was then used to calculate χ, the solute–solvent interaction parameter, and the Hildebrand solubility parameter, δ, which provides a quantifiable method to identify good solvents. Of the nanoparticles studied, 1,3-di-o-carboranylpropane is thermodynamically stable in toluene, with a χ less than 0.5, a solubility limit of 2.47 mg/mL, and all solutions remaining clear with no visible particle settling. For all of the particles tested, there was good correlation between the physical observations of the solutions, χ, and δ. For instance, lower values of χ correspond to a smaller radius of gyration (Rg). A list of suitable solvents based on δ is also presented.

Surface Tension, Density and Viscosity Studies on the Associative Behaviour of Oxyethylene-Oxybutylene Diblock Copolymers in Water at Different Temperatures

The associative properties of methoxy (CH3O-) ended E58B11 and hydroxyl (-OH) ended E56B19 oxyethylene-oxybuty- lene diblock copolymers in aqueous solution at different temperature are reported in this paper. For both copolymers, E represents an oxyethylene (-[CH2CH2O]-) unit and B an oxybutylene (-[CH(C2H5)CH2O]-) unit while the subscripts denote the number average block length. Surface tension measurements were used to find out surface excess concentrations (Γm), area per molecule (αs1 ) at air/water interface and Gibbs free energy for adsorption (△G0ads ) for the pre-micellar region at four temperatures. Likewise thermodynamic parameters of micellization such as, critical micelle concentrations (CMC), enthalpy of micellization (△H0mic ), standard free energy of micellization (△G0mic) and entropy of micellization (△S0mic ), were also obtained using surface tension measurements. Solution densities were used to deter-mine the partial specific volume of micelle ( Vmic) and micellar density (ρmic). Dilute solution viscosities have been used to estimate the intrinsic viscosities [η], solute-solvent interaction parameter (KH) and hydration value of micelle (Wh) at various temperatures. The effect of temperature on the micelle properties is also discussed.

Kinetics study of a Diels‐Alder reaction in mixtures of an ionic liquid with molecular solvents

AbstractThe second‐order rate constants for cycloaddition reaction of cyclopentadiene with naphthoquinone were determined spectrophotometrically in various compositions of 1‐(1‐butyl)‐3‐methylimidazolium terafluoroborate ([bmim]BF4) with water and methanol at 25 °C. Rate constants of the reaction in pure solvents are in the order of water > [bmim]BF4 > methanol. Rate constants of the reaction decrease sharply with mole fraction of the ionic liquid in aqueous solutions and increase slightly to a maximum in alcoholic mixtures. Multi‐parameter correlation of logk2 versus solute–solvent interaction parameters demonstrated that solvophobicity parameter (Sp), hydrogen‐bond donor acidity (α) and hydrogen‐bond acceptor basicity (β) of media are the main factors influencing the reaction rate constant. The proposed three‐parameter model shows that the reaction rate constant increases with Sp, α and β parameters. Copyright © 2008 John Wiley & Sons, Ltd.

Thermodynamic study of functionally modified chitosan and its blends in aqueous media at 298.15 K

Linear polysaccharides, negatively charged N-methylene phosphonic chitosan (NMPC) and positively charged quaternized chitosan (QC) were synthesized. Thermodynamic study of the synthesized materials NMPC, QC and the mixture of equal concentrations of NMPC + QC was carried out in aqueous media at 298.15 K. Solute–solvent interactions have been studied through ultrasonic, viscometry and densitometric techniques. Isentropic compressibilities of the polymer solutions and hydration number of monomeric units in the functionalized chitosan and their blends or different systems were derived using experimental values of speed of sound and densities. Viscometric studies were used in estimating average molecular weight M v of polymers and their blends and solute–solvent interaction parameter χ for quantitative estimation of solute–solvent interactions.

Vapour–Liquid Equilibrium of Water/Ethanol/1-Butanol/Salt: Prediction and Experimental Verification

Experimental vapour–liquid equilibrium data of water/ethanol/1-butanol saturated with NaCl, KCl and NH4Cl compared well with those predicted by Tan–Wilson and Tan–NRTL models for multicomponent solvent–solute mixture. The Wilson and NRTL solvent–solvent interaction parameters were obtained by the regression of the experimental vapour–liquid equilibrium data of the salt-free solvent mixture. The solute–solvent interaction parameters were calculated from the experimental bubble points of the individual solvent components saturated with the respective salts. Water was significantly salted-into the liquid phase by all the three salts giving a vapour phase rich in organic solvent components and a liquid phase rich in water. Both NaCl and NH4Cl showed little or no preference in salting-out the two organic solvent components while KCl showed preferential salting-out of ethanol. These results are consistent with previous reports that solvent component i would be salted-in or out of the liquid phase relative to solvent component j depending on whether the ratio of the solute-solvent interaction parameter, Asj/Asi (Tan–Wilson model) or exp(Tis – Tjs) (Tan–NRTL model) is less than or greater than 1. These findings show that the two models describe reasonably well the effect of salts on the liquid–phase activity coefficient of the solvent components in a ternary solvent mixture. The criteria and the rapid screening method proposed by Tan on the selection of a suitable non–volatile soluble solute for the elimination of azeotropes and for the salt distillation of close-boiling and azeotropic binary solvent mixtures are therefore equally applicable to ternary solvent mixture.

Prediction and experimental verification of the effect of salt on the vapour–liquid equilibrium of ethanol/1-propanol/water mixture

The vapour–liquid equilibria of ethanol/1-propanol/water mixture saturated with sodium chloride, potassium chloride and copper sulphate predicted by Tan–Wilson and Tan–NRTL phase models compared well with the experimental data. The prediction was based on the solvent–solvent interaction parameters obtained from the regression of the experimental vapour–liquid equilibrium of the salt-free mixture and the solute–solvent interaction parameters calculated from the bubble points of the individual solvent components saturated with the respective salt. The extent of salting-out of the solvent components from the liquid phase by the three salts generally decreased in the order of 1-propanol, ethanol and water giving a vapour phase rich in 1-propanol and ethanol and a liquid phase rich in water at equilibrium. These effects are slightly different between sodium and potassium chloride and are significantly greater than those of copper sulphate. These observed salting effects are consistent with the criteria that solvent component, i, would be preferentially salted-in or out of the liquid phase than solvent component, j, if the ratio of their solute–solvent interaction parameters A s j / A s i (Tan–Wilson) or exp( τ is − τ js ) (Tan–NRTL) is less or greater than one. These results confirm the good accuracy of the two phase models in describing the effect of a non-volatile solute on the liquid phase activity of a solvent component in a ternary solvent mixture. These results suggest that the rapid screening method and criteria for selecting a suitable non-volatile solute to separate close-boiling and azeotropic binary solvent mixture developed by Tan based on these phase models can be extended to include the ternary solvent mixtures.

Solute–solvent interaction parameters by gas chromatography

Gas–liquid distribution coefficients at ideal dilution in non-volatile solvents can be measured by gas chromatography. The numerical value of a coefficient depends on the choice of the concentration unit in the solvent and in the gas phase. The relationships between different coefficients characterizing gas–liquid equilibria are discussed and summarized. Coefficients determined at several temperatures permit calculation of the standard chemical potential difference of the solute with the ideal gas phase as reference as a function of temperature, the g-SPOT. Following the proposal of Kirchhoff the latter can be formulated as an equation with three constants. As in the gas phase the molecules of the solute have no interacting partners, the three constants, ΔH, ΔS and ΔC, characterize the interaction between solvent and solute molecules. They will be called the “solute–solvent interaction parameters”. In the same system the values of these parameters depend on the choice of the distribution coefficient. Five different distribution coefficients result five sets of interaction parameters. It is shown that conversion of a parameter set to another implies additive corrections independent of the nature of the solute. If g-SPOT-s are measured in a series of solvents, the data may be used to calculate the corresponding liquid–liquid partition coefficients by electing one of the solvents as reference (l-SPOT). The corresponding “relative interaction parameters” can be calculated by simple substraction. In a second chapter the precautions are summarized, necessary for gas chromatographic determination of distribution coefficients and examples are given for interaction parameters in different systems. It is concluded that there are significant differences between g-SPOT-s related to different distribution coefficients. On the other hand, differences between l-SPOT-s are negligible.

Solute–solvent interaction parameters by gas chromatography

Gas–liquid distribution coefficients at ideal dilution in non-volatile solvents can be measured by gas chromatography. The numerical value of a coefficient depends on the choice of the concentration unit in the solvent and in the gas phase. The relationships between different coefficients characterizing gas–liquid equilibria are discussed and summarized. Coefficients determined at several temperatures permit calculation of the standard chemical potential difference of the solute with the ideal gas phase as reference as a function of temperature, the g-SPOT. Following the proposal of Kirchhoff the latter can be formulated as an equation with three constants. As in the gas phase the molecules of the solute have no interacting partners, the three constants, Δ H, Δ S and Δ C, characterize the interaction between solvent and solute molecules. They will be called the “solute–solvent interaction parameters”. In the same system the values of these parameters depend on the choice of the distribution coefficient. Five different distribution coefficients result five sets of interaction parameters. It is shown that conversion of a parameter set to another implies additive corrections independent of the nature of the solute. If g-SPOT-s are measured in a series of solvents, the data may be used to calculate the corresponding liquid–liquid partition coefficients by electing one of the solvents as reference ( l-SPOT). The corresponding “relative interaction parameters” can be calculated by simple substraction. In a second chapter the precautions are summarized, necessary for gas chromatographic determination of distribution coefficients and examples are given for interaction parameters in different systems. It is concluded that there are significant differences between g-SPOT-s related to different distribution coefficients. On the other hand, differences between l-SPOT-s are negligible.

A mode coupling theory analysis of microscopic friction in the macroscopic limit

In order to understand the physical origin of the cross-over of solute diffusion to the hydrodynamic regime, we present an analytical and numerical calculation of the microscopic friction obtained from the mode coupling theory (MCT) at the limit of large solute size. In this limit we have shown that in the MCT expression of the microscopic friction/diffusion the contribution from the density mode vanishes and the current contribution to the diffusion reduces to the famous Stokes–Einstein form. Our numerical calculation shows that along with the size of the solute if we accordingly change the mass and the solute–solvent interaction parameters then cross-over to the current dominated regime happens early.

Prediction and experimental verification of the salt effect on the vapour–liquid equilibrium of water–ethanol–2-propanol mixture

Experimental vapour–liquid equilibria of water–ethanol–2-propanol saturated with NaNO 3, NaCl, KCl and containing 0.05 mol CH 3COOK/mol total solvent compared well with those predicted by Tan–Wilson and Tan–non-random two liquid (NRTL) models for multicomponent solvent–solute mixture using a set of solvent–solvent interaction parameters obtained from the regression of the vapour–liquid equilibrium of the solvent mixture without the dissolved solute and a set of solute–solvent interaction parameters calculated from the bubble points of the individual solvent components saturated or containing the same molar ratio of solute/total solvents as the mixture. The results also showed that a solvent component i is salted-in or out of the liquid phase relatively more than solvent component j would depend on whether A s j / A s i (Tan–Wilson model) or exp( τ is − τ js ) (Tan–NRTL model) is less or greater than 1. This is consistent with earlier publications on the effect of dissolved solutes (electrolytes and non-electrolytes) on the binary solvents mixtures. These findings confirmed that Tan–Wilson and Tan–NRTL models for multicomponent solvent–solute system can provide an accurate and rapid screening of electrolytes and non-electrolytes for their suitability in facilitating solvent separation by salt distillation of ternary solvent mixtures simply by determining the relative ratios of the solute–solvent interaction parameters from the respective bubble points of the solvent components containing the dissolved solute. The results also suggest that this may also be extended to other multicomponent solvent mixtures.

Liquid–liquid equilibria of water/1-propanol/methyl ethyl ketone/potassium chloride

The liquid–liquid equilibrium of water/1-propanol/methyl ethyl ketone (MEK) at 25°C was significantly modified by the presence of dissolved potassium chloride. Water is salted out of the organic phase while MEK is more preferentially salted out of the aqueous phase than 1-propanol. These results in considerable enlargement of the two-phase region and enhancement of the extractive efficiency of MEK for the separation of 1-propanol from its aqueous mixture. Good correlation of the liquid–liquid equilibria (LLE) of the system in the presence of potassium chloride up to saturation was obtained with Tan’s modified NRTL phase model for multicomponent solute–solvent mixtures with the solute–solvent interaction parameters expressed as a third-order polynomial function in salt concentration. Similar to the observation reported for vapour–liquid equilibrium (VLE) of solvent–solute mixtures, salting-in and salting-out of the solvent components from the respective phases can be predicted according to the relative solute–solvent interaction parameters of the solvent components in the two phases.

Solution photophysics of ketocyanine dyes in neat and mixed binary solvents

The effect of the solvent on the excited state photophysics of two ketocyanine dyes was examined by studying the lifetime () of the S 1 state in the picosecond domain. The overall luminescence decay constant (1/Gt) shows a linear correlation with the polarity parameter E T(30) in neat solvents. The radiative decay constant is practically independent of solvation, whereas the radiationless deactivation constant is sensitive to solvation; this has been attributed to hydrogen bond interaction of the solute carbonyl oxygen with the solvent. Preferential solvation by the protic component occurs in protic-aprotic binary mixed solvents. The influence of the solute-solvent interaction parameters and solvent non-ideality in determining the preferential solvation characteristics has been examined.

POLYMER SOLUBILITY THEORY PREDICTS EFFICIENCY OF RESIDUAL OIL EXTRACTION BY POLAR SOLVENTS

ABSTRACT Light paraffinic solvents (C2 to C7) have traditionally been utilized by the petroleum refining industry to extract oils from crude distillation residua. Extracted oils constitute feedstock to lubricants manufacture and, to a lesser extent, additional cracking stock. More recent literature reveals a growing interest in polar, non-hydrocarbon partially oil-soluble solvents such as alcohols, ketones, and esters of lower carboxylic acids. In this work, articles and patents which report the separation of residua into asphalt and extracted oil by means of polar solvents are briefly reviewed, and the separation performance of same of those solvents is correlated to the solute-solvent interaction parameter (ϰ) in the Flory-Huggins theory of polymer solubility. The three dimensional solubility parameter (δ) approach is followed to estimate ϰ for the solvents of interest at the appropriate operating conditions. The saturate, aromatic, and polar compounds fractions of a bitumen are characterized by solubil...

New expressions to describe solution nonideal osmotic pressure, freezing point depression, and vapor pressure.

New empirical expressions for osmotic pressure, freezing point depression, and vapor pressure are proposed based on the concepts of volume occupancy and (or) hydration force. These expressions are in general inverse relationships in comparison to the standard ideal expressions for the same properties. The slopes of the new equations are determined by the molecular weight of the solute and known constants. The accuracy and precision of the molecular weights calculated from the slope are identical and approximately 1% for the experiments reported here. The nonideality of all three colligative expressions is described by a dimensionless constant called the solute-solvent interaction parameter I. The results on sucrose have the same I = 0.26 for all three solution properties. The nonideality parameter I increased from 0.26 on sucrose to 1.7 on hemoglobin to successfully describe the well-known nonideal response of macromolecules.