Solvent Parameters Research Articles

Comprehensive insight into solubility, dissolution properties and solvation behaviour of dapsone in co-solvent solutions

This research was mainly committed to the solubility profile, dissolution properties and solvation behavior for the systems formed by dapsone in aqueous solutions of ethanol/acetone/methanol (1) and non-aqueous solution of ethyl acetate (1) + ethanol (2) accompanied by numerous computational methodology. All experiments for solubility were conducted by using a shake-flask method at pressure p = 101.2 kPa and temperatures from 278.15 to 323.15 K. For each solvent solution system, the equilibrium solubility in magnitude of dapsone was recorded as highest in neat ethanol/ethyl acetate/methanol/acetone (1) at 323.15 K; and lowest in neat ethanol (2) or water (2) at 278.15 K. The three-dimensional Hansen solubility parameter was utilized here to investigate solubility performance. Numerous common relationships including modified van’t Hoff Jouyban–Acree model, mixture response surface model, Jouyban–Acree model, and modified Wilson model provided acceptable correlation consequences for the solubility magnitudes obtained with relative average deviations of < 12.33 %. The solubility magnitude at temperature of 298.15 K was also studied by the extended Hildebrand solubility approach, gaining RAD of < 3.24 %. By consideration of some accessible solution properties, the preferential solvation of dapsone was further examined through quantitation by employing the inverse Kirkwood–Buff integrals way. The positive parameters of preferential solvation in ethanol/acetone/methanol-rich and intermediate composition solutions indicates that the drug dapsone is preferentially solvated by ethanol/acetone/methanol. It can be speculated that dapsone performs as Lewis acid behavior with ethanol/acetone/methanol molecules in above composition regions. Nevertheless preferential solvation of dapsone is made neither by ethanol nor by ethyl acetate in the ethyl acetate + ethanol solution. The dissolution of dapsone in all studied systems was endothermic and entropy-driven process.

Solubility, solvation thermodynamics and solvent effect of thiabendazole in several cosolvent blends

Equilibrium solubility determination and model correlation were performed in the present research for the systems formed by solid solute of thiabendazole and binary aqueous blends of acetonitrile, methanol, n-propanol and isopropanol. Experiments at temperatures ranging from 283.15 to 323.15 K were conducted by the use of the shake-flask saturation technique at 101.2 kPa. For the given binary solvent blends, the minimum mole fraction solubility was recorded in water at 283.15 K; and the maximum one, in neat organic solvent at 323.15 K. The generated equilibrium solubility was satisfactorily described by two models, modified van’t Hoff-Jouyban–Acree and Jouyban–Acree, with the relative average deviations (%) of no more than 6.08. Good prediction results of extend Hildebrand solubility approach (relative average deviations < 4.10%) were observed in terms of quartic polynomial for the four solution systems to correlate the interaction parameter (W) and solubility parameters of the solvents’ blends in the absence of thiabendazole (δ1+2). Analysis of the relative contributions from intra- and inter-molecular interactions to solubility variation of solid solute of thiabendazole (298.15 K) was quantitatively carried out via the linear solvation energy relationships (LSER). The descriptors of blended solvents comprising solubility parameter and hydrogen-bond basicity were principally responsible for the variation of determined solubility. Besides, the preferential solvation of thiabendazole was quantitatively researched via the inverse Kirkwood–Buff integrals method on the basis of some accessible properties for blended solvent systems. The positive preferential solvation parameters for thiabendazole in the middle and cosolvent-rich blends powerfully suggested that thiabendazole was preferentially solvated by cosolvents of isopropanol, acetonitrile, n-propanol, ethanol and methanol. The conjecture was reasonable that in above compositions, thiabendazole mainly served as Lewis acidic in terms of its interactions with alcohol molecules; while for the acetonitrile mixtures, this behavior was contributed by polarization effect. Besides, thiabendazole was preferentially solvated by ethanol (2) in ethyl acetate (1) + ethanol (2) solutions with ethyl acetate-rich compositions, and by water (2) solvent in aqueous blends with rich water compositions.

Solubility and thermodynamic analysis of famotidine polymorphs in pure solvents

The present study investigates the solubility of famotidine polymorphs forms A and B between 298.15 K and 348.15 K in a range of pure solvents: water, methanol, ethanol, isopropanol and acetonitrile. Empirical and semi-empirical models have been fitted to solubility data determined experimentally by a gravimetric method. The solid phases have been characterized by FTIR and Raman spectroscopy, SEM and PXRD. In addition, heat capacities and melting data determined by DSC have been used to estimate the fusion thermodynamics and the activity of the solid phases as a function of temperature. The relationship between the famotidine polymorphs is monotropic, with form A being the stable polymorph. For both polymorphs, in terms of mass ratio, the solubility in the studied solvents decreases in the order methanol > water > ethanol > acetonitrile > isopropanol. The activity coefficient at saturation in all the solutions exceeds unity, showing a positive deviation with respect to ideality, which translates into solubilities significantly lower than the ideal values. Among the alcohols, a consistent correlation is observed between the polarity and the order of solubility.The Hildebrand solubility parameter is also well correlated with the order of solubilities in the studied solvents, with a higher solubility in more polar solvents, revealing the importance of the hydrogen bonding of the sulfamoyl group oxygens.

Effect of temperature and polarity on the solubility and preferential solvation of sinapic acid in aqueous mixtures of DMSO and Carbitol

Reported equilibrium mole fraction solubilities of sinapic acid (3) in {DMSO (1) + water (2)} and {Carbitol (1) + water (2)} mixtures at several temperatures were analyzed in terms of the Hildebrand solubility parameter of these aqueous mixtures. Moreover, the preferential solvation parameters of sinapic acid in these aqueous saturated mixtures at (298.15 and 313.15) K were determined based on the inverse Kirkwood-Buff integrals (IKBI) as widely described in the literature. Sinapic acid is preferentially solvated by water in water-rich mixtures, i.e. (0.00 < x1 < 0.21 in {DMSO (1) + water (2)}) and (0.00 < x1 < 0.12 in {Carbitol (1) + water (2)}) but preferentially solvated by the cosolvents in the other mixtures composition. In the former cases these results could be interpreted as a consequence of hydrophobic hydration around the non-polar moieties of sinapic acid. Moreover, in the last cases, the observed trends could be due to the Lewis acidic behavior of sinapic acid in front of DMSO or Carbitol molecules because both cosolvents exhibit higher Lewis basic character than water, as indicated by the respective solvatochromic parameters. A single cosolvency model for representing the equilibrium solubility of sinapic acid in binary solvents at various temperatures was also provided based on a combination of Hansen solubility parameters and Jouyban-Acree model.

Equilibrium solubility, inter- and intra-molecular interactions and solvation performance of flutamide in some aqueous blended co-solvents

The current research was devoted to the solubility profile and its computational methodologies, partial Hansen solubility parameter, inter- and intra-molecular interactions, and solvation performance for the systems formed by crystalline flutamide dissolved in water and cosolvent, i.e. ethanol/isopropanol/acetonitrile/1,4-dioxane. All solubility experimentations were done via a common shake-flask saturation method at a pressure of atmosphere (p = 101.2 kPa) and the temperature range from 278.15 to 323.15 K. The solubility in magnitudes of flutamide were recorded as the lowest in pure water at 278.15 K; and the highest in pure co-solvent at 323.15 K. The three-dimensional Hansen solubility parameters were utilized here to illustrate the solubility profile. The quantifiable explanation of solvent effect was carried out via modelling the flutamide solubility using linear solvation energy relationships. Satisfactory outcomes for correlating the solubility magnitudes were realized by means of modified van’t Hoff–Jouyban–Acree, modified Wilson and Jouyban–Acree models with the relative average errors of < 6. 67 %. The observed solubility data at 298.15 K were further studied by the extended Hildebrand solubility approach, acquiring the relative average deviations of < 1.54 %. The preferential solvation investigation of flutamide was further performed through quantitation by inverse Kirkwood–Buff integrals. The positive values of preferential solvation parameters in co-solvent-rich and middle composition blends point to that the drug flutamide is preferentially solvated by the co-solvent. In these composition ranges, flutamide is possibly acting as Lewis acid performance with 1,4-dioxane/ethanol/isopropanol molecules; while for the aqueous acetonitrile solutions, the solvation behavior is responsible for the polarization effect.

Preferential Solvation of 4-Carboxyl-2, 6-Dinitrophenylazohydroxynaphthalenes in Mixed Hydroxylic Solvents

Background: The applications of a group of 4-carboxyl-2,6-dintrophenylazohydroxynaphathalenes, AZ-01 to 04, as colourants, chemosensors or synthetic intermediates have been limited by their solubility.Aim: To investigate the effect of solvent mixture composition on the solubility, solution thermodynamics and position of equilibrium processes of the dyes.Method: The UV-visible spectral patterns of the dyes in binary mixtures including Methanol:Water, Ethanol:Water, Methanol:Ethanol, Methanol:Propan-1-ol, Methanol:Propan-2-ol, Propan-1-ol:Water and Propan-2-ol:Water were acquired. The type and quantitative estimation of solute-solvent interactions at play were determined by fitting spectral patterns to solvent parameters using multilinear regression.Results: Preferential solvation was detected by the non-ideality of the plots of E12 as against the mole fractions of co-solvent in all binary mixtures. In pure solvents, the spectral shifts of AZ-01, 03 and 04, which exist predominantly in the hydrazone form, were affected by polarity of solvent milieu while solvent basicity and acidity, in that order, were the significant parameters for AZ-02. In aqueous alcoholic mixtures, solvent polarity was contributory, although to different degrees, to the observed spectral data of the four dyes. However, solvent acidity and basicity were the primary determinants of spectral shifts observed with AZ-04 and AZ-03 respectively. Spectra-structure relationships identified the formation of the charged hydrazone tautomer which requires stabilisation by polar solvent milieu as responsible for the observed trend. In addition, interactions between new aggregated solvent-solvent species and the propionic acid substituent present in AZ-03 contributed to its spectral shifts.Conclusion: The solvatochromic properties of the phenylazonaphthalene series in binary mixtures have been successfully studied.

Three‐dimensional solubility parameters of natural rubber and its predictive power in diffusion coefficients

AbstractEquilibrium swelling test is employed to study the swelling responses of natural rubber (NR) in various solvents, and to determine the total Hildebrand solubility parameter (δt) of NR. The three‐dimensional solubility parameters (HSP) of NR is obtained by virtue of software package as the result of being δd = 17.50 MPa1/2, δp = 3.20 MPa1/2, δh = 1.40 MPa1/2, and δt = 17.85 MPa1/2, respectively. The swelling ratio (q) is correlated with the energy difference (Ra) in order to deeply understand the swelling principle of NR, and the results turn out that q decreased with the increase of the Ra and it can be used to explain the abnormal swelling phenomena of methyl acetate and ethyl acetate. One of the possible applications of Ra is the prediction or explanation of diffusion behaviors of small liquids in the rubber matrix. Therefore, the diffusion coefficient (D) is calculated in accordance with the Fick's law model and attempted to correlate with the Ra value. Two qualitative relationships between D and Ra and χHSP can be preliminarily established now, which can provide an easy way to predict the diffusion behavior of fluids in rubber matrix.

Electrospun scaffolds for wound healing applications from poly(4‐hydroxybutyrate): A biobased and biodegradable linear polymer with high elastomeric properties

AbstractElectrospun scaffolds of the biodegradable and biocompatible poly‐4‐hydroxybutyrate (P4HB) polyester have been prepared using horizontal and vertical set‐up configurations of electrospinning. Specifically, it has been evaluated the influence of solvent, polymer concentration, and processing parameters, such as applied voltage, flow rate, and needle tip‐collector distance. Scaffolds obtained under the most favorable conditions were characterized in terms of crystallinity, lamellar supramolecular order, thermal (including calorimetric and thermogravimetric data), mechanical, and surface properties. Results pointed out significant differences with respect to commercial sutures (based in P4HB, e.g., MonoMax®) and demonstrated that electrospun scaffolds were constituted by crystalline microfibers with a tangled distribution that leads to high modulus Young modulus (4 MPa), maximum strength (28 MPa), and elongation (360%). Furthermore, new scaffolds had thermal stability and a rough surface that led to a hydrophobic character (105°). Scaffolds could also be successfully loaded during the electrospinning process with a peptide analog to the fibroblast growth factor (e.g., CYRSRKYSSWYVALKRC), giving rise to fully biocompatible samples with a clear acceleration in wound healing.

On the applicability of regular solution and Flory‐Huggins theories to asphaltene liquid mixtures

AbstractWe critically review two classic, molecular‐based solution theories, the regular solution theory and the Flory‐Huggins theory, in the context of revealing their limited applicability to liquid mixtures containing asphaltenes, a significant fraction of crude oil. Asphaltene molecular structures, either as depicted by the Archipelago model or the island model, are non‐linear (not chain‐like) and rigid, making the application of the aforementioned theories to describe their phase behaviour problematic. In addition, since asphaltenes contain chemical moieties that are able to interact through directional dependent specific intermolecular interactions (e.g., hydrogen bonds), this renders the incorporation of Hildebrand solubility parameters into the theories inappropriate. As a result, the two theories do not always predict the onset and amount of asphaltene precipitation correctly for crude oil under different conditions (e.g., temperature, pressure, chemical composition of crude oil, solvent concentration). It is the hope of this author that researchers in the field channel their efforts into developing a brand‐new solution theory for asphaltene liquid mixtures by taking the key molecular attributes of asphaltenes into account.

Solubility modeling, Hansen solubility parameter, solvation thermodynamics and enthalpy–entropy compensation of 5-chlorooxine (form I) in several aqueous cosolvent solutions

The current contribution was dedicated to solubility profile, solvation behavior, and inter- and intramolecular interactions for the binary systems formed by 5-chlorooxine (I) in aqueous solutions of ethanol, N-methyl-2-pyrrolidinone (NMP), isopropanol and N,N-dimethylformamide (DMF) together with numerous computational approach. A shake-flask method conducted all experiments under local pressure p = 101.2 kPa over temperatures ranging from 278.15 to 323.15 K. For each cosolvent system, the highest equilibrium solubility of 5-chlorooxine (I) was recorded in neat cosolvent at temperature of T = 323.15 K; and the lowest one, in neat solvent of water at 278.15 K. The solubility performance was investigated by the use of the Hansen solubility parameter and extended Hildebrand solubility approach. Numerous models, e.g. mixture response surface, Jouyban–Acree, modified Wilson and Jouyban–Acree–van’t Hoff acceptably correlated the obtained mole fraction solubility with relative average deviations (RAD) no greater than 7.25 %. The relative contribution of solute–solvent and solvent–solvent interactions to equilibrium solubility variation of 5-chlorooxine (I) at the temperature of 298.15 K was analyzed quantitatively by employing the linear solvation energy relationships, indicating that the dipolarity-polarizability and solubility parameter of solvent systems were predominantly responsible for the 5-chlorooxine (I) solubility. The solvation behavior was inspected by the extended Hildebrand solubility approach applied to the solubility data at 298.15 K, gaining RAD of no more than 3.15 %. In addition, preferential solvation of 5-chlorooxine (I) was quantitatively analyzed by the method of inverse Kirkwood–Buff integrals in terms of some available solution properties. The positive preferential solvation parameters for 5-chlorooxine (I) in intermediate and cosolvent-rich solutions suggests that the solute 5-chlorooxine (I) is preferentially solvated by cosolvents. It is speculated that 5-chlorooxine (I) performs as a Lewis acid behavior with cosolvent molecules in above composition districts. The dissolution of 5-chlorooxine (I) in all aqueous solution systems was entropy-driven and endothermic process.

Self-stratifying behavior of a novel light-curable coating with gradient hydrophobic properties: Computational and experimental study

In this study, we report a rational approach to design a novel VOC-free self-stratifying light-curable coating containing bio-renewable materials based on the methacrylated gelatin (GelMA) and acrylated epoxidized soybean oil diluted by the acrylated glycidyl neodecanoate (AESO-CE). The self-stratified structures of the AESO-CE/GelMA coatings attained through the visible light curing were recognized by SEM-EDX and water contact angle (WCA) analyses. Hildebrand (δHild) and Hansen solubility parameters (δHans) of AESO-CE and GelMA were calculated by molecular dynamics simulation and Hansen solubility spheres, respectively. It was revealed that the computational immiscibility results had an illustrative agreement with the experimental incompatibility observations in different AESO-CE/GelMA weight ratios over time. Furthermore, the findings demonstrated that surface tension and solubility parameters can be considered when dealing with self-stratification prediction in the gelatin-soybean oil-based coatings. The results indicated that the coatings with both hydrophobic-hydrophilic natures with WCA of 66–84° can be achieved by a fast curing reaction without the aid of solvent evaporation. Besides, it was concluded that the stratifying level and surface hydrophobicity properties have been significantly affected by the AESO-CE/GelMA weight ratio and the mixture viscosity. Accordingly, this investigation provides a helpful insight to develop a green coating exhibiting gradient hydrophobic behavior, as a promising candidate for advanced breathable food and bio-applications.

Using COSMO-RS to Predict Solvatochromic Parameters for Deep Eutectic Solvents

The development of novel green solvents demands the knowledge of their properties, such as polarity, which can be described through solvatochromic parameters. However, while these are available for a wide range of conventional solvents, there is a lack of data for the emergent ones. Considering the need for such data, predictive models to estimate the Kamlet–Taft (K–T) parameters for deep eutectic solvents (DES) are developed here. The models, based on the conductor-like screening model for real solvents (COSMO-RS) descriptors, were initially developed and tested for 175 organic solvents to validate the applicability of the proposed approach. This approach was then extended for DES, which were classified into two categories, acids and nonacids. The developed equations showed a very good performance for all three K–T parameters, and this is the first work to propose models for all K–T parameters for DES. Moreover, a comparison between polarity data of DES and organic compounds showed that DES, rather than replace common solvents, can extend their range of polarities, reinforcing their designer solvent ability.

Prediction of the Miscibility of PBAT/PLA Blends.

Designing polymer structures and polymer blends opens opportunities to improve the performance of plastics. Blending poly(butylene adipate-co-terephthalate) (PBAT) and polylactide (PLA) is a cost-effective approach to achieve a new sustainable material with complementary properties. This study aimed to predict the theoretical miscibility of PBAT/PLA blends at the molecular level. First, the basic properties and the structure of PBAT and PLA are introduced, respectively. Second, using the group contribution methods of van Krevelen and Hoy, the Hansen and Hildebrand solubility parameters of PBAT and PLA were calculated, and the effect of the molar ratio of the monomers in PBAT on the miscibility with PLA was predicted. Third, the dependence of the molecular weight on the blend miscibility was simulated using the solubility parameters and Flory–Huggins theory. Next, the glass transition temperature of miscible PBAT/PLA blends, estimated using the Fox equation, is shown graphically. According to the prediction and simulation, the blends with a number-average molecular weight of 30 kg/mol for each component were thermodynamically miscible at 296 K and 463 K with the possibility of spinodal decomposition at 296 K and 30% volume fraction of PBAT. This study contributes to the strategic synthesis of PBAT and the development of miscible PBAT/PLA blends.

Development of Predictive Expressions for Infinite Dilution Activity Coefficients, Molar Solubilities and Partition Coefficients for Solutes Dissolved in 2-Pyrrolidone Based on the Abraham Solvation Parameter Model

Development of Predictive Expressions for Infinite Dilution Activity Coefficients, Molar Solubilities and Partition Coefficients for Solutes Dissolved in 2-Pyrrolidone Based on the Abraham Solvation Parameter Model

Photochemical and photophysical properties of tetracarboxylic acid phthalocyanines from glycolic and lactic acids in homogeneous and micro heterogeneous media

Glycolic acid and lactic acid substituted zinc phthalocyanines were studied concerning their photophysical and photochemical properties in eight organic solvents (homogeneous medium) and in aqueous media with the presence of CTAB and PVP 360 surfactants. Solvent effects were investigated according to several physical solvent parameters, including studies that used more than one parameter at a time, such as the ET(30) scale and the Lippet-Mataga equation. Computational studies were realized and was found in good agreement with experimental data indicating J-type dimers' formation through hydrogen bonds, which may not affect the spectroscopic properties. Fluorescence lifetimes were recorded using a time-correlated single-photon counting setup (TCSPC) technique. The direct method (analyzing the phosphorescence decay curves of singlet oxygen at 1270 nm) was employed to study singlet oxygen quantum yields. Phthalocyanine macrocycle with lactic acid substituent showed better solvation arrangement than the glycolic derivative, which can be explained based on the presence of the methyl group bonded to the chain. The water solvation of Pc’s in the presence of cationic surfactant (CTAB) and biocompatible polymer PVP 360 increses the importance of this study for appliance in photodynamic therapy (PDT).

Solubility, correlation, dissolution thermodynamics and preferential solvation of meloxicam in aqueous mixtures of 2-propanol

Background: Meloxicam is a powerful analgesic and anti-inflammatory drug widely prescribed by physicians in current therapeutics. Because of the very low aqueous equilibrium solubility of meloxicam, this property has been studied in {2-propanol + water} mixtures from (293.15 to 313.15) K to expand the solubility database about pharmaceutical compounds in mixed solvents useful for homogeneous liquid dosage forms design. Methods: Flask shaken method and UV-vis spectrophotometry were used for meloxicam solubility determinations. Jouyban-Acree model was challenged for solubility correlation. The van’t Hoff and Gibbs equations were employed here to calculate the respective apparent standard thermodynamic quantities for the dissolution and mixing processes, namely Gibbs energy, enthalpy, and entropy. In addition, the inverse Kirkwood-Buff integrals were employed to compute the preferential solvation parameters of meloxicam by 2-propanol in the mixtures. Results: Meloxicam solubility increases with temperature arising and maximum solubilities are observed in the mixture of x1 = 0.70 at all temperatures. Jouyban-Acree model correlates the meloxicam solubility very well. Dissolution processes were endothermic in all cases and entropy-driven in the interval 0.20 ≤ x1 ≤ 1.00. Non-linear enthalpy–entropy relationship was observed in the plot of enthalpy vs. Gibbs energy exhibiting negative but variant slopes in the composition region 0.00 &lt; x1 &lt; 0.40 and variant negative and positive slopes in the other mixtures. Meloxicam is preferentially solvated by water in water-rich mixtures, it is apparently solvated by water in 2-propanol-rich mixtures, but it is preferentially solvated by 2-propanol in the composition interval of 0.19 &lt; x1 &lt; 0.78. Conclusion: Solid-liquid equilibrium of meloxicam in {2-propanol + water} mixtures has been studied at several temperatures as a contribution to preformulation studies of homogeneous liquid pharmaceutical dosage forms based on this drug.

Understanding the Transport of Atmospheric Gases in Liquid Electrolytes for Lithium–Air Batteries

In metal–air batteries, carbon dioxide (CO2) and nitrogen (N2) are, apart from oxygen (O2), also present as dissolved species in the liquid electrolyte. These dissolved gases can strongly influence the battery performance, as they affect the discharge mechanism and the stability of the lithium metal anode. Therefore, their solubility and diffusivity are important parameters, that are rarely considered in the development of electrolytes for metal–air batteries. In this work, the diffusion coefficients (D) and Henry’s law solubility constants (H cp ) of O2, N2 and CO2 in common ether-based (diglyme (2G), triglyme (3G) and tetraglyme (4G)) and DMSO-based electrolytes are measured by means of gas uptake measurements. Additionally, the diffusion coefficients are calculated through molecular dynamics simulations. The results agree well with the experimental data. Furthermore, the influence of solvent parameters, such as surface tension and viscosity, on the solubility and the diffusivity as well as the impact of the addition of LiTFSI as conducting salt are investigated. The reported data will help to assess the impact of dissolved gases on the cell chemistry of nonaqueous lithium–air batteries, especially on the solid electrolyte interphase (SEI) at the lithium anode, and to predict diffusivity and gas solubility in other electrolytes.

Solubility, solvent effect, and modelling of oxcarbazepine in mono-solvents and N-methyl-2-pyrrolidone + water solvent mixtures at different temperatures and its application for the preparation of nanosuspensions

A solid–liquid equilibrium technique was used to measure the solubility of oxcarbazepine in a mono-solvent and a solvent mixture in the temperature range of 288.15–308.15 K under atmospheric pressure. Oxcarbazepine in N-methyl-2-pyrrolidone (NMP) showed the highest solubility. The KAT-LSER model was applied to determine solvent effect on the solubility of oxcarbazepine in mono-solvents at 298.15 K; the dipolarity–polarizability and cohesive energy density, as the Hildebrand solubility parameter, of the solvent had a greater effect on oxcarbazepine solubility than other parameters. The solubility results of oxcarbazepine in the mono-solvents and mixed (NMP + water) solvents were correlated by applying various models. The oxcarbazepine dissolution in the mono-solvents and mixed (NMP + water) solvents was endothermic and spontaneous. Oxcarbazepine nanosuspensions were prepared based on these solubility results of oxcarbazepine in a mono-solvent and mixed (NMP + water) solvent; the average particle size of all oxcarbazepine nanosuspensions was smaller than 200 nm. The experimental and calculated solubility results of oxcarbazepine may be utilized in drug development through the application of solubilization techniques to increase the bioavailability of poorly water-soluble drugs.

Dynamics of Meso–Chiral Interconversion in a Butterfly‐Shape Overcrowded Alkene Rotor Tunable by Solvent Properties

AbstractElucidation of dynamics of molecular rotational motion is an essential part and challenging area of research. We demonstrate reversible diastereomeric interconversion of a molecular rotor composed of overcrowded butterfly‐shape alkene (FDF). Its inherent dual rotatory motion (two rotors, one stator) with interconversion between two diastereomers, chiral trans‐FDF and meso cis‐FDF forms, has been examined in detail upon varying temperatures and solvents. The free energy profile of 180° revolution of one rotor part has a bimodal shape with unevenly positioned maxima (transition states). FDF in aromatic solvents adopts preferentially meso cis‐conformation, while in non‐aromatic solvents a chiral trans‐conformation is more abundant owing to the solvent interactions with peripheral hexyl chains (solvophobic effect). Moderate correlations between the trans‐FDF/cis‐FDF ratio and solvent parameters, such as refractive index, polarizability, and viscosity were found.

Dynamics of Meso-Chiral Interconversion in a Butterfly-Shape Overcrowded Alkene Rotor Tunable by Solvent Properties.

Elucidation of dynamics of molecular rotational motion is an essential part and challenging area of research. We demonstrate reversible diastereomeric interconversion of a molecular rotor composed of overcrowded butterfly-shape alkene (FDF). Its inherent dual rotatory motion (two rotors, one stator) with interconversion between two diastereomers, chiral trans-FDF and meso cis-FDF forms, has been examined in detail upon varying temperatures and solvents. The free energy profile of 180° revolution of one rotor part has a bimodal shape with unevenly positioned maxima (transition states). FDF in aromatic solvents adopts preferentially meso cis-conformation, while in non-aromatic solvents a chiral trans-conformation is more abundant owing to the solvent interactions with peripheral hexyl chains (solvophobic effect). Moderate correlations between the trans-FDF/cis-FDF ratio and solvent parameters, such as refractive index, polarizability, and viscosity were found.