Journal articles: 'Van’t Hoff enthalpy of solution'

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Aydi, Abdelkarim, Cherifa Ayadi, Kaouther Ghachem, Abdulaal Al-Khazaal, Daniel Delgado, Mohammad Alnaief, and Lioua Kolsi. "Solubility, Solution Thermodynamics, and Preferential Solvation of Amygdalin in Ethanol + Water Solvent Mixtures." Pharmaceuticals 13, no. 11 (November 16, 2020): 395. http://dx.doi.org/10.3390/ph13110395.

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The equilibrium solubility of amygdalin in [ethanol (1) + water (2)] mixtures at 293.15 K to 328.15 K was reported. The thermodynamic properties (standard enthalpy ΔsolnH°, standard entropy ΔsolnS°, and standard Gibbs energy of solution ΔsolnG°) were computed using the generated solubility data via van’t Hoff and Gibbs equations. The dissolution process of amygdalin is endothermic and the driving mechanism in all mixtures is entropy. Maximal solubility was achieved in 0.4 mole fraction of ethanol at 328.15 K and the minimal one in neat ethanol at 293.15 K. Van’t Hoff, Jouyban–Acree–van’t Hoff, and Buchowski–Ksiazczak models were used to simulate the obtained solubility data. The calculated solubilities deviate reasonably from experimental data. Preferential solvation parameters of amygdalin in mixture solvents were analyzed using the inverse Kirkwood–Buff integrals (IKBI) method. Amygdalin is preferentially solvated by water in ethanol-rich mixtures, whereas in water-rich mixtures, there is no clear evidence that determines which of water or ethanol solvents would be most likely to solvate the molecule.

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Bhalu, Ankita A., Kapil D. Bhesaniya, Nayan J. Vekariya, and Shipra H. Baluja. "Chalcones: A Solubility Study at Different Temperatures." International Letters of Chemistry, Physics and Astronomy 31 (March 2014): 7–19. http://dx.doi.org/10.18052/www.scipress.com/ilcpa.31.7.

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Some new chalcones are synthesized by the condensation of aryl ketones with aromatic aldehydes and solubility of these synthesized chalcones is determined in chloroform and dichloromethane at temperatures ranging between 293.15 K and 313.15 K by gravimetric method. The experimental data was correlated well with modified Apelblat equation. Further, from the experimental solubility data, some thermodynamic parameters such as dissolution enthalpy, Gibb’s energy and entropy etc. were evaluated using van’t Hoff equation. The positive Gibb’s energy and negative entropy suggests spontaneous dissolution and more ordered structure in solution.

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Bhalu, Ankita A., Kapil D. Bhesaniya, Nayan J. Vekariya, and Shipra Baluja. "Chalcones: A Solubility Study at Different Temperatures." International Letters of Chemistry, Physics and Astronomy 31 (March 28, 2014): 7–19. http://dx.doi.org/10.56431/p-d42l27.

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Some new chalcones are synthesized by the condensation of aryl ketones with aromatic aldehydes and solubility of these synthesized chalcones is determined in chloroform and dichloromethane at temperatures ranging between 293.15 K and 313.15 K by gravimetric method. The experimental data was correlated well with modified Apelblat equation. Further, from the experimental solubility data, some thermodynamic parameters such as dissolution enthalpy, Gibb’s energy and entropy etc. were evaluated using van’t Hoff equation. The positive Gibb’s energy and negative entropy suggests spontaneous dissolution and more ordered structure in solution.

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Hentschel, Lorena, Jan Hansen, Stefan U. Egelhaaf, and Florian Platten. "The crystallization enthalpy and entropy of protein solutions: microcalorimetry, van't Hoff determination and linearized Poisson–Boltzmann model of tetragonal lysozyme crystals." Physical Chemistry Chemical Physics 23, no. 4 (2021): 2686–96. http://dx.doi.org/10.1039/d0cp06113a.

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Microcalorimetric and van't Hoff determinations as well as a theoretical description provide a consistent picture of the crystallization enthalpy and entropy of protein solutions and their dependence on physicochemical solution parameters.

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Baluja, Shipra, Kapil Bhesaniya, Rahul Bhalodia, and Sumitra Chanda. "Solubility of Butylated Hydroxytoluene (BHT) in Aqueous and Alcohol Solutions from 293.15 to 313.15 K." International Letters of Chemistry, Physics and Astronomy 28 (February 2014): 48–58. http://dx.doi.org/10.18052/www.scipress.com/ilcpa.28.48.

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The solubility of Butylated hydroxyl toluene in aqueous and alcohol solutions were determined at different temperatures (293.15 to 313.15) K. Using Van’t Hoff and Gibb’s equations, some thermodynamic functions such as Gibbs energy, enthalpy and entropy of dissolution, and of mixing of Butylated hydroxyl toluene in aqueous and alcohol solutions, were evaluated from solubility data. The solubility was greater in butanol and minimum in water. The enthalpies, entropy and Gibb’s energy of dissolution were positive for all solvents.

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Baluja, Shipra, Kapil Bhesaniya, Rahul Bhalodia, and Sumitra Chanda. "Solubility of Butylated Hydroxytoluene (BHT) in Aqueous and Alcohol Solutions from 293.15 to 313.15 K." International Letters of Chemistry, Physics and Astronomy 28 (February 19, 2014): 48–58. http://dx.doi.org/10.56431/p-c5b9qj.

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The solubility of Butylated hydroxyl toluene in aqueous and alcohol solutions were determined at different temperatures (293.15 to 313.15) K. Using Van’t Hoff and Gibb’s equations, some thermodynamic functions such as Gibbs energy, enthalpy and entropy of dissolution, and of mixing of Butylated hydroxyl toluene in aqueous and alcohol solutions, were evaluated from solubility data. The solubility was greater in butanol and minimum in water. The enthalpies, entropy and Gibb’s energy of dissolution were positive for all solvents.

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Shakeel, Faiyaz, and Sultan Alshehri. "Solubilization, Hansen Solubility Parameters, Solution Thermodynamics and Solvation Behavior of Flufenamic Acid in (Carbitol + Water) Mixtures." Processes 8, no. 10 (September 23, 2020): 1204. http://dx.doi.org/10.3390/pr8101204.

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The solubilization, solution thermodynamics, solvation behavior and Hansen solubility parameters (HSPs) of an anti-inflammatory medicine flufenamic acid (FFA) in various Carbitol + water mixtures were evaluated in this study. The experimental solubility of FFA in mole fraction (xe) was measured at T = 298.2–318.2 K and p = 0.1 MPa using a static equilibrium method. The xe values of FFA in various Carbitol + water mixtures were correlated with van’t Hoff, Apelblat, Yalkowsky–Roseman, Jouyban–Acree and Jouyban–Acree–van’t Hoff models. All the studied models showed good correlation with mean error values of less than 2%. The xe value of FFA was found to increase significantly with the increase in temperature and Carbitol mass fraction in all Carbitol + water mixtures evaluated. The maximum and minimum xe values of FFA were recorded in pure Carbitol (2.81 × 10−1) at T = 318.2 K and pure water (5.80 × 10−7) at T = 298.2 K, respectively. Moreover, the HSP of FFA was found to be more closed with that of pure Carbitol, indicating the maximum solubility of FFA in pure Carbitol. The estimated values of activity coefficients showed higher molecular interactions in FFA–Carbitol combinations compared with FFA–water combinations. Thermodynamic studies indicated an endothermic and entropy-driven dissolution of FFA in all Carbitol + water mixtures. The solvation behavior of FFA was observed as enthalpy driven in all Carbitol + water combinations evaluated.

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Shakeel, Faiyaz, Sultan Alshehri, Mohd Imran, Nazrul Haq, Abdullah Alanazi, and Md Khalid Anwer. "Experimental and Computational Approaches for Solubility Measurement of Pyridazinone Derivative in Binary (DMSO + Water) Systems." Molecules 25, no. 1 (December 31, 2019): 171. http://dx.doi.org/10.3390/molecules25010171.

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The current research work was performed to evaluate the solubilization behavior, solution thermodynamics, and solvation behavior of poorly soluble pyridazinone derivative i.e., 6-phenyl-pyridazin-3(2H)-one (PPD) in various binary solvent systems of dimethyl sulfoxide (DMSO) and water using experimental and various computational approaches. The solubility of PPD in various binary solvent system of DMSO and water was investigated within the temperature range T = 298.2 K to 318.2 K at constant air pressure p = 0.1 MPa, by employing an isothermal technique. The generated solubility data of PPD was computationally represented by five different cosolvency models including van’t Hoff, Apelblat, Yalkowsky–Roseman, Jouyban–Acree, and Jouyban–Acree–van’t Hoff models. The performance of each computational model for correlation studies was illustrated using root mean square deviations (RMSD). The overall RMSD value was obtained <2.0% for each computational model. The maximum solubility of PPD in mole fraction was recorded in neat DMSO (4.67 × 10−1 at T = 318.2 K), whereas the lowest one was obtained in neat water (5.82 × 10−6 at T = 298.2 K). The experimental solubility of PPD in mole fraction in neat DMSO was much higher than its ideal solubility, indicating the potential of DMSO for solubility enhancement of PPD. The computed values of activity coefficients showed maximum molecular interaction in PPD-DMSO compared with PPD-water. Thermodynamic evaluation showed an endothermic and entropy-driven dissolution of PPD in all the mixtures of DMSO and water. Additionally, enthalpy–entropy compensation evaluation indicated an enthalpy-driven mechanism as a driven mechanism for the solvation property of PPD.

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Kumar, M., G. Elangovan, R. Tamilarasan, G. Vijayakumar, P. C. Mukeshkumar, and S. Sendhilnathan. "Biosorption of aniline blue from aqueous solution using a novel biosorbent Zizyphus oenoplia seeds: Modeling studies." Polish Journal of Chemical Technology 17, no. 3 (September 1, 2015): 70–77. http://dx.doi.org/10.1515/pjct-2015-0052.

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Abstract This article presents the feasibility for the removal of Aniline Blue dye (AB dye) from aqueous solution using a low cost biosorbent material Zizyphus oenoplia seeds. In this study, a batch mode experiments of the adsorption process were carried out as a function of pH, contact time, concentration of dye, adsorbent dosage and temperature. The experimental data were fitted with Freundlich and Langmuir isotherm equations. The feasibility of the isotherm was evaluated with dimensionless separation factor (RL). The kinetic data of sorption process are evaluated by using pseudo-first order and pseudo-second order equations. The mode of diffusion process was evaluated with intra-particle diffusion model. The thermodynamic parameters like change in enthalpy (ΔHº); change in entropy (ΔSº) and Gibbs free energy change (ΔGº) were calculated using Van’t Hoff plot. The biosorbent material was characterized with Fourier Transform Infrared (FTIR) spectroscopy and the morphology was identified with Scanning Electron Microscope (SEM) in before and after adsorption of AB dye.

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Le, D. T., E. V. Butyrskaya, and T. V. Eliseeva. "Cluster Adsorption of L-Histidine on Carbon Nanotubes in Aqueous Solutions at Different Temperatures." Russian Journal of Physical Chemistry A 96, no. 8 (August 2022): 1719–23. http://dx.doi.org/10.1134/s003602442208012x.

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Abstract Adsorption isotherms are obtained for L-histidine on carbon nanotubes using aqueous solutions at temperatures of 25, 35, 45, 55, 65, and 80°C. The isotherms are interpreted by using the cluster adsorption model and analyzing the dependence of the strength of the bond nanotube–amino acid on temperature. Equations of the adsorption isotherms are obtained for all temperatures. The calculated results indicate that L-histidine is fixed on a nanotube’s surface in the form of monomers and different clusters. The equilibrium characteristics of adsorption are found to change as the temperature rises. Values obtained for the coefficients of equilibrium are used to calculate apparent enthalpy ΔH* of L-histidine adsorption by nanotubes, according to the van’t Hoff equation.

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Dezhampanah, Hamid, Abdol Khalegh Bordbar, and Shamim Farshad. "Thermodynamic characterization of phthalocyanine–human serum albumin interaction." Spectroscopy 25, no. 5 (2011): 235–42. http://dx.doi.org/10.1155/2011/549403.

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The thermodynamic of the binding of nickel (II) tetrasulfonated phthalocyanine anion [Ni(tspc)4–], to human serum albumin (HSA) was investigated in 5 mM aqueous phosphate buffer of pH 7.40 at 25°C using optical absorption spectroscopy. The results show that [Ni(tspc)4–] does not have any affinity for aggregation due to increasing of salt concentration and exists as monomers even in homogeneous aqueous solutions of high ionic strengths (more than 2 M NaCl). The binding constant (K) was obtained by analysis of optical absorption spectra of mentioned complex at various HSA concentrations using SQUAD software. The value ofKwas estimated to be 4.89×105±0.03 (M–1) at 25°C. The thermodynamic parameters were calculated by van’t Hoff equation. The enthalpy and entropy changes were 28.08 kJ/mol and 203.09 J/(mol?·?K) at 25°C, respectively. The results indicate that the binding is mainly entropy driven and the enthalpy is unfavorable for it, the hydrophobic forces thus playing a major role in the binding process.

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Negrea, Adina, Sylwia Ronka, Mihaela Ciopec, Narcis Duteanu, Petru Negrea, and Maria Mihailescu. "Kinetics, Thermodynamics and Equilibrium Studies for Gold Recovery from Diluted Waste Solution." Materials 14, no. 18 (September 15, 2021): 5325. http://dx.doi.org/10.3390/ma14185325.

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2,2′-thiobisethanol dimethacrylate/ethylene glycol dimethacrylate copolymer (coP-TEDMA/EGDMA) was used as a sorbent for gold recovery from residual solutions resulting from the electroplating industry. Firstly, synthesized material was characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, and confocal laser scanning microscopy. The sorption process mechanism was evidenced on the basis of kinetic, thermodynamic and equilibrium studies. To highlight this, the influence of solution pH, temperature and gold initial concentration on maximum sorption capacity was studied. The obtained experimental data were modeled using Langmuir, Freundlich and Sips sorption isotherms, and it was observed that the Sips one was better for describing the studied sorption process. Kinetic data were fitted using pseudo-first-order and pseudo-second-order kinetic models. Of these models, the studied process was better described by the pseudo-second-order model. The thermodynamic parameters free Gibbs energy (ΔG0), enthalpy (ΔH0), and entropy (ΔS0) were evaluated on the basis of the van’t Hoff equation. On the basis of the thermodynamic study, it was concluded that gold recovery on coP-TEDMA/EGDMA is a spontaneous and endothermic process.

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Labidi, Abdelkader, Asier Salaberria, Susana Fernandes, Jalel Labidi, and Manef Abderrabba. "Functional Chitosan Derivative and Chitin as Decolorization Materials for Methylene Blue and Methyl Orange from Aqueous Solution." Materials 12, no. 3 (January 24, 2019): 361. http://dx.doi.org/10.3390/ma12030361.

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Dyes are classified as one of the major pollutants of water. They have negative impacts not only on environment but also on human health. In fact, wastewater that contains these harmful substances requires many types of treatments. Therefore, alternative methods and adsorption agents are needed. Herein, we propose to evaluate the decolorization of methylene blue (MB) and methyl orange (MO) as two models of soluble dyes from water using chitin and chitosan-graft-polyacrylamide. Furthermore, the applicability of these biomacromolecules as alternative adsorption agents, their sticking probability and desorption were also examined. Experimental parameters such as dye concentration, contact time, pH solution, adsorbent dosage and temperature were thoroughly examined for the grafted chitosan and chitin. The activation energy ( E a ) and the thermodynamic variables (i.e., standard Gibb’s free energy ( Δ G 0 ), standard enthalpy ( Δ H 0 ), and standard entropy ( Δ S 0 )) were determined using the Van’t Hoff and Arrhenius equations. The sticking probability ( S *) model for MB and MO removal by chitin and the chitosan derivative demonstrated that both dyes were successfully removed under the proposed conditions. Desorption studies of MB and MO showed the reusability of both materials, suggesting their application for removing dyes from aqueous solution.

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Romero Nieto, Alba Miledy, Nestor E. Cerquera, and Daniel Ricardo Delgado. "Measurement and correlation of solubility of ethylparaben in pure and binary solvents and thermodynamic properties of solution." Revista Colombiana de Ciencias Químico-Farmacéuticas 48, no. 2 (May 1, 2019): 332–47. http://dx.doi.org/10.15446/rcciquifa.v48n2.82702.

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Solubility data of bioactive compound such as ethylparaben (EtP) are important for the scientific and community. Therefore, in present study, solubility, solution thermodynamics and solute-solvent interactions (at molecular level) of EtP in nine cosolvent mixtures (1-propanol {n-PrOH) (1) + methanol (MeOH) (2)} including pure solvent (methanol and 1-propanol) at three different temperatures, i.e. (T =283.2 K, 298.2 K, and 313.2 K) and constant pressure (p = 0.1 MPa) were studied. Experimental solubility of EtP (expressed in mole fraction) was observed highest in n-PrOH at 313.2 K, so, mole fraction solubility of EtP (x3) increases when temperature arises and increases with n-PrOH proportion increasing. Ideal solubilities of EtP were estimated using their thermal parameters at three different temperatures. Ideal solubilities of EtP were observed similar to experimental solubilities of EtP at each temperature. With the help of ideal solubilities of EtP, activity coefficients were estimated. Based on estimated values of activity coefficients, highest interactions at molecular level were observed in rich-MeOH mixtures. Apparent thermodynamic analysis data showed endothermic and enthalpy-driven dissolution of EtP in each solvent and mixture studied. Solubility behavior was adequately correlated by means of the van’t Hoff and Yalkowsky-Roseman models combined.

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Varlan, Aurica, and Mihaela Hillebrand. "Spectral study of coumarin-3-carboxylic acid interaction with human and bovine serum albumins." Open Chemistry 9, no. 4 (August 1, 2011): 624–34. http://dx.doi.org/10.2478/s11532-011-0043-5.

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AbstractFluorescence spectroscopy and circular dichroism (CD) spectroscopy were used to investigate the interaction of coumarin-3-carboxylic acid with human serum albumin (HSA) and bovine serum albumin (BSA) under physiological conditions in a buffer solution of pH 7.4. Quenching constants were determined using the Lineweaver-Burk equation to provide a measure of the binding affinity of coumarin-3-carboxylic acid to HSA/BSA. Binding studies concerning the number of binding sites, n, and apparent binding constant, K, were performed by a fluorescence quenching method at different temperatures (298, 303 and 310 K). The thermodynamic parameters, enthalpy change (ΔH0) and entropy change (ΔS0) as calculated according to the van’t Hoff equation, indicated that hydrogen bonding and van der Waals forces play a major role in coumarin-3-carboxylic acid-HSA association whereas electrostatic interactions dominate in coumarin-3-carboxylic acid-BSA association. The distance, r, between the donor (HSA/BSA) and acceptor (coumarin-3-carboxylic acid) has been estimated using Förster’s equation, on the basis of resonance energy transfer. Furthermore, CD spectra were used to investigate the α-helix changes of the HSA and BSA molecules upon addition of coumarin-3-carboxylic acid.

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Ol’khovich, Marina, Angelica Sharapova, Svetlana Blokhina, and German Perlovich. "Isavuconazole: Thermodynamic Evaluation of Processes Sublimation, Dissolution and Partition in Pharmaceutically Relevant Media." Molecules 26, no. 16 (August 6, 2021): 4759. http://dx.doi.org/10.3390/molecules26164759.

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A temperature dependence of saturated vapor pressure of isavuconazole (IVZ), an antimycotic drug, was found by using the method of inert gas-carrier transfer and the thermodynamic functions of sublimation were calculated at a temperature of 298.15 K. The value of the compound standard molar enthalpy of sublimation was found to be 138.1 ± 0.5 kJ·mol−1. The IVZ thermophysical properties—melting point and enthalpy—equaled 302.7 K and 29.9 kJ mol−1, respectively. The isothermal saturation method was used to determine the drug solubility in seven pharmaceutically relevant solvents within the temperature range from 293.15 to 313.15 K. The IVZ solubility in the studied solvents increased in the following order: buffer pH 7.4, buffer pH 2.0, buffer pH 1.2, hexane, 1-octanol, 1-propanol, ethanol. Depending on the solvent chemical nature, the compound solubility varied from 6.7 × 10−6 to 0.3 mol·L−1. The Hansen s approach was used for evaluating and analyzing the solubility data of drug. The results show that this model well-described intermolecular interactions in the solutions studied. It was established that in comparison with the van’t Hoff model, the modified Apelblat one ensured the best correlation with the experimental solubility data of the studied drug. The activity coefficients at infinite dilution and dissolution excess thermodynamic functions of IVZ were calculated in each of the solvents. Temperature dependences of the compound partition coefficients were obtained in a binary 1-octanol/buffer pH 7.4 system and the transfer thermodynamic functions were calculated. The drug distribution from the aqueous solution to the organic medium was found to be spontaneous and entropy-driven.

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Khalaf, Bayan, Othman Hamed, Shehdeh Jodeh, Ghadir Hanbali, Roland Bol, Omar Dagdag, and Subhi Samhan. "Novel, Environment-Friendly Cellulose-Based Derivatives for Tetraconazole Removal from Aqueous Solution." Polymers 13, no. 3 (January 30, 2021): 450. http://dx.doi.org/10.3390/polym13030450.

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In this study, cellulose-based derivatives with heterocyclic moieties were synthesized by reacting cellulose with furan-2-carbonyl chloride (Cell-F) and pyridine-2,6-dicarbonyl dichloride (Cell-P). The derivatives were evaluated as adsorbents for the pesticide tetraconazole from aqueous solution. The prepared adsorbents were characterized by SEM, TGA, IR, and H1 NMR instruments. To maximize the adsorption efficiency of tetraconazole, the optimum conditions of contact time, pH, temperature, adsorbent dose, and initial concentration of adsorbate were determined. The highest removal percentage of tetraconazole from water was 98.51% and 95% using Cell-F and Cell-P, respectively. Underivatized nanocellulose was also evaluated as an adsorbent for tetraconazole for comparison purpose, and it showed a removal efficiency of about 91.73%. The best equilibrium adsorption isotherm model of each process was investigated based on the experimental and calculated R2 values of Freundlich and Langmuir models. The adsorption kinetics were also investigated using pseudo-first-order, pseudo-second-order, and intra-particle-diffusion adsorption kinetic models. The Van’t Hoff plot was also studied for each adsorption to determine the changes in adsorption enthalpy (∆H), Gibbs free energy (∆G), and entropy (∆S). The obtained results showed that adsorption by Cell-F and Cell-P follow the Langmuir adsorption isotherm and the mechanism follows the pseudo-second-order kinetic adsorption model. The obtained negative values of the thermodynamic parameter ∆G (−4.693, −4.792, −5.549 kJ) for nanocellulose, Cell-F, and Cell-P, respectively, indicate a spontaneous adsorption process. Cell-F and Cell-P could be promising absorbents on a commercial scale for tetraconazole and other pesticides.

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Olu, S. C., P. E. Dim, and J. O. Okafor. "REMOVAL OF CU (II) FROM DYE EFFLUENT USING NATURAL AND PHOSPHATE-MODIFIED NIGERIAN KAOLINITE CLAY." International Journal of Research -GRANTHAALAYAH 7, no. 8 (August 31, 2019): 402–14. http://dx.doi.org/10.29121/granthaalayah.v7.i8.2019.690.

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This study indicates kaolinite clay as an effective adsorbent for the uptake of Cu (II) from wastewater. The adsorption process was studied with variation of time, temperature and adsorbent dosage at the effluent pH of 6. X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), Brunauer Emmett and Teller (BET) and Scanning electron microscopy (SEM) were used to characterize the adsorbents. XRD spectra showed that modification with KH2PO4 did not significantly change the crystal spacing on the lattice structure of the clay mineral; however, there were shifts in the intensity of the peaks for the modified kaolinite clay. The FTIR spectra showed that certain functional groups are responsible for binding the metal ions from solution. SEM indicated an increase in the porosity of the modified adsorbent as compared with the unmodified kaolinite, which enhances metal ion adsorption on modified kaolinite clay. The BET indicate that acid modification increased the surface area and total pore volume of the kaolinite clay. The kinetic study revealed that the pseudo-first-order model fitted poorly to the equilibrium data, however, the pseudo-second-order model had a good fit for all reaction time at different initial concentrations. The mechanism of the sorption process was evaluated using thermodynamic properties such as enthalpy change (ΔH), Gibbs free energy change (ΔG), and entropy change (ΔS), which were evaluated using Van’t Hoff equations. The negative values of free energy change (ΔG), suggests spontaneity and feasibility of the process. The positive values of enthalpy change (ΔH) indicate endothermic nature of the process.

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Gigliuto, Antonio, Rosalia Maria Cigala, Anna Irto, Maria Rosa Felice, Alberto Pettignano, Demetrio Milea, Stefano Materazzi, Concetta De Stefano, and Francesco Crea. "The Solution Behavior of Dopamine in the Presence of Mono and Divalent Cations: A Thermodynamic Investigation in Different Experimental Conditions." Biomolecules 11, no. 9 (September 5, 2021): 1312. http://dx.doi.org/10.3390/biom11091312.

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The interactions of dopamine [2-(3,4-Dihydroxyphenyl)ethylamine, (Dop−)] with methylmercury(II) (CH3Hg+), magnesium(II), calcium(II), and tin(II) were studied in NaCl(aq) at different ionic strengths and temperatures. Different speciation models were obtained, mainly characterized by mononuclear species. Only for Sn2+ we observed the formation of binuclear complexes (M2L2 and M2LOH (charge omitted for simplicity); M = Sn2+, L = Dop−). For CH3Hg+, the speciation model reported the ternary MLCl (M = CH3Hg+) complex. The dependence on the ionic strength of complex formation constants was modeled by using both an extended Debye–Hückel equation that included the Van’t Hoff term for the calculation of enthalpy change values of the formation and the Specific Ion Interaction Theory (SIT). The results highlighted that, in general, the entropy is the driving force of the process. The sequestering ability of dopamine towards the investigated cations was evaluated using the calculation of pL0.5 parameter. The sequestering ability trend resulted to be: Sn2+ > CH3Hg+ > Ca2+ > Mg2+. For example, at I = 0.15 mol dm−3, T = 298.15 K and pH = 7.4, pL0.5 = 3.46, 2.63, 1.15, and 2.27 for Sn2+, CH3Hg+, Ca2+ and Mg2+ (pH = 9.5 for Mg2+), respectively. For the Ca2+/Dop− system, the precipitates collected at the end of the potentiometric titrations were analyzed by thermogravimetry (TGA). The thermogravimetric calculations highlighted the formation of solid with stoichiometry dependent on the different metal:ligand ratios and concentrations of the starting solutions.

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Masuelli, Martin Alberto. "Study of Bovine Serum Albumin Solubility in Aqueous Solutions by Intrinsic Viscosity Measurements." Advances in Physical Chemistry 2013 (May 29, 2013): 1–8. http://dx.doi.org/10.1155/2013/360239.

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The behavior of bovine serum albumin (BSA) in water is scarcely studied, and the thermodynamic properties arising from the experimental measurements have not been reported. Intrinsic viscosity measurements are very useful in assessing the interaction between the solute and solvent. This work discussed in a simple determination of the enthalpy of BSA in aqueous solution when the concentration ranges from 0.2 to 36.71% wt. and the temperature from 35 to 40°C. The relationship between the concentration and intrinsic viscosity is determined according to the method of Huggins. The temperature increase reduces the ratio between inherent viscosity and concentration (ηi/c). This is reflected in the Van't Hoff curve. Furthermore, this work proposes hydrodynamic cohesion value as an indicator of the degree of affinity of protein with water and thermodynamic implications in conformational changes.

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Marino, Antonio Di, and Franscisco Mendicuti. "Fluorescence of the Complexes of 2-Methylnaphthoate and 2-Hydroxypropyl-α-, -β-, and -γ-Cyclodextrins in Aqueous Solution." Applied Spectroscopy 56, no. 12 (December 2002): 1579–87. http://dx.doi.org/10.1366/000370202321115841.

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Fluorescence techniques were employed to study the inclusion complexes of 2-methylnaphthoate (MN) with 2-hydroxypropyl-α-cyclodextrin (αHPCD), 2-hydroxypropyl-β-cyclodextrin (βHPCD), and 2-hydroxypropyl-γ-cyclodextrin (γHPCD). Emission spectra of MN show two vibronic bands whose intensity ratio R is very sensitive to the polarity of the medium. The stoichiometry and formation constants of these complexes were investigated by obtaining R as a function of the cyclodextrin (CD) concentration. Results showed identical stoichiometry (1/1) for the three MN/αHPCD, MN/β-HPCD, and MN/γHPCD complexes. Formation constants at 25 °C were 780 ± 15, 2700 ± 130, and 165 ± 10 M−1, respectively. ΔH0 and ΔS0 were obtained from linear van't Hoff plots. Results reveal that the complexation of MN with αHPCD is enthalpy driven. With βHPCD, both the entropy and enthalpy terms favor the process, whereas the formation of the complex with γHPCD is entropically governed. The extrapolation of R at infinite CD concentration allows us to estimate the effective dielectric constants of the inner CD cavities, which are around 50, but which differ from their counterparts, the naturally occurring α-, β-, and γ-CDs. Fluorescence anisotropy, quencher lifetimes, and average lifetimes can also give additional information about the structure and driving forces accompanying the formation of such complexes.

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Saha, Tapan K., Subarna Karmaker, and Md F. Alam. "Kinetics, mechanism and thermodynamics involved in sorption of meso-tetrakis(4-sulfonatophenyl)porphyrin onto chitosan in aqueous medium." Journal of Porphyrins and Phthalocyanines 18, no. 03 (March 2014): 240–50. http://dx.doi.org/10.1142/s1088424613501174.

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Sorption of meso-tetrakis(4-sulfonatophenyl)porphyrin ( H 2 tpps ) onto chitosan has been investigated in aqueous medium. Kinetic and isotherm studies were carried out by considering the effects of various parameters, such as pH, initial concentration of H 2 tpps solution, and temperature. The kinetic data obtained from different batch experiments were analyzed using pseudo first-, second-order, intraparticle, and film diffusion kinetic models. The equilibrium sorption data was analyzed by using Tempkin, Langmuir and Freundlich models. The best results were achieved with the pseudo second-order kinetic, Langmuir and Freundlich isotherm models. The intraparticle diffusion and film diffusion are the rate limiting steps. The amount of sorbate adsorbed at equilibrium (qe) increased with increasing the initial concentration of H 2 tpps solution, showing maximum sorption capacity of 445.21 μmol.g-1. The activation energy (Ea) of sorption kinetics was found to be 19.47 kJ.mol-1. Thermodynamic parameters such as change in free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) were evaluated by applying the Van't Hoff equation. Thermodynamic activation parameters such as change in enthalpy of activation (ΔH‡), entropy of activation (ΔS‡), and free energy of activation (ΔG‡) were also calculated. The thermodynamics of H 2 tpps sorption onto chitosan in aqueous medium indicates its spontaneous and endothermic nature.

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Vasiliev, Aleksandr N., Nidhu L. Banik, Rémi Marsac, Stepan N. Kalmykov, and Christian M. Marquardt. "Determination of complex formation constants of neptunium(V) with propionate and lactate in 0.5–2.6 m NaCl solutions at 22–60°C using a solvent extraction technique." Radiochimica Acta 107, no. 7 (July 26, 2019): 623–34. http://dx.doi.org/10.1515/ract-2019-3107.

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Abstract Natural clay rocks like Opalinus (OPA) and Callovo-Oxfordian (COx) clay rock are considered as potential host rocks for deep geological disposal of nuclear waste. However, small organic molecules such as propionate and lactate exist in clay rock pore water and might enhance Np mobility through a complexation process. Therefore, reliable complex formation data are required in the frame of the Safety Case for a nuclear waste repository. A solvent extraction technique was applied for the determination of ${\rm{NpO}}_2^ + $ complexation with propionate and lactate. Extraction was conducted from isoamyl alcohol solution containing 10−3 M TTA and 5 · 10−4 M 1,10-phenanthroline. Experiments were performed in 0.5–2.6 m NaCl solutions at temperatures ranging from 22 to 60 °C. Formation of 1:1 Np(V) complexes for propionate and lactate was found under the studied conditions. The SIT approach was applied to calculate equilibrium constants β°(T) at zero ionic strength from the experimental data. Log β°(T) is found linearly correlated to 1/T for propionate and lactate, evidencing that heat capacity change is near 0. Molal reaction enthalpy and entropy ( ${\Delta _{\rm{r}}}H_{\rm{m}}^ \circ $ and ${\Delta _{\rm{r}}}S_{\rm{m}}^ \circ $ ) could therefore be derived from the integrated van’t Hoff equation. Data for log β° (298.15 K) are in agreement with literature values for propionate and lactate. Np(V) speciation was calculated for concentrations of acetate, propionate and lactate measured in clay pore waters of COx. In addition, the two site protolysis non-electrostatic surface complexation and cation exchange (2SPNE SC/CE) model was applied to quantitatively describe the influence of Np(V) complexation on its uptake on Na-illite, a relevant clay mineral of OPA and COx.

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24

A. Saeed1, Saba, and Dunya E. AL-Mammar2. "ADSORPTION POTENTIAL FOR A MIXTURE OF CHEMICALLY AND THERMALLY TREATED CLAYS TO REMOVE ORANGE G DYE FROM WASTE-WATER." iraq journal of market research and consumer protection 13, no. 2 (December 31, 2021): 10–31. http://dx.doi.org/10.28936/jmracpc13.2.2021.(2).

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This study examined the adsorption behavior of anionic dye (orange G) from aqueous solution onto the raw and activated a mixture of illite, kaolinite and chlorite clays from area of Zorbatiya (east of Iraq).The chemical treatment involved alkali and acid activation. The alkali activation obtained by treated the raw clay (RC) with 5M NaOH (ACSO) and the acid activation founded by treated it with 0.25M HCl (ACH) and 0.25M H_2 〖SO〗_4 (ACS). The thermal treatment carried out by calcination the produce activated clay at 750oC for acid activation and 105oC for alkali activation. Batch adsorption method was used to study the adsorption of orange G dye onto raw and activated clays. The impact of different factors related to the adsorption process was studied such as: agitation time, clay dosage, solution pH, starting OG dye concentration, temperature and ionic strength. The adsorption process was described by using Langmuir, Freundlich, Temkin and Dubinin-Raduchkevish isotherm models. Thermodynamic functions like change in enthalpy〖∆H〗^°, change in entropy 〖∆S〗^° and change in Gibbs free energy 〖∆G〗^°were estimated based on Vanʼt Hoff equation.

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Ibrahim Abubakar, Safiyya, Muhammad Adamu Ibrahim, and Muhammad Bashir Ibrahim. "Adsorption of Methyl Orange Dye onto Raw Maize Cob and Maize Cob Activated Carbon: Isotherms and Thermodynamic Studies." International Journal of Advanced Chemistry 8, no. 1 (June 14, 2020): 147. http://dx.doi.org/10.14419/ijac.v8i1.30676.

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This study was aimed to evaluate the adsorption of Methyl orange (MO) onto raw maize cob (RMC) and maize cob activated carbon (MCAC) from aqueous solution using batch adsorption studies. The produced adsorbents were characterized by Scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FTIR). The influence of contact time, dosage, concentration, temperature, and pH were investigated as well as Isotherm and Thermodynamic studies. Effect of contact time showed that Methyl orange adsorption were found to reach equilibrium within 125 and 110 minutes with optimum percentage removal of about 86.98% and 94.57% for raw maize cob and maize cob activated carbon respectively. The dye removal efficiency was found to increase with increasing initial dye concentration from 10 mg/L to 100 mg/L, and adsorption efficiency was found to be high at lower pH. However, increase in the dosage of the adsorbents lead to the increase in the adsorption process. The equilibrium adsorption data were analyzed using four adsorption models: Langmuir, Freundlich, Temkin, and D-R. The results revealed that MO with raw maize cob and maize cob activated carbon fit well to Freundlich with R2 value 0.977 and Temkin with R2 value 0.990 respectively and mean adsorption energy calculated from D-R shows it is physical adsorption and also values of enthalpy and Gibbs free energy proves that. Values of activation parameters such as free energy changes (∆G), enthalpy change (∆H) and entropy change (∆S) were calculated using Van't Hoff equation. All ∆G values were negative indicating that the adsorption was feasible and spontaneous. The result indicated that RMC and MCAC can be used for removal of MO from aqueous solution. The maize cob waste which is discarded as waste material was found to be effective adsorbent for the removal of Methyl orange dye from aqueous solution.

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Dezhampanah, Hamid, Abdol-Khalegh Bordbar, and Shahram Tangestaninejad. "Thermodynamic investigation of manganese(III) 5-(1-(4-carboxybutyl)pyridinium-4-yl) 10,15,20-tris-(1-methylpyridinium-4-yl)porphyrin with calf thymus DNA." Journal of Porphyrins and Phthalocyanines 13, no. 08n09 (August 2009): 964–72. http://dx.doi.org/10.1142/s1088424609001224.

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Binding properties of two water-soluble porphyrins, manganese(III) 5-(1-(4-carboxybutyl)pyridinium-4-yl) 10,15,20-tris(1-methylpyridinium-4-yl)porphyrin ( Mn(III)5-CBPyP ) and manganese(III) 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin ( Mn(III)TMPyP ), in the presence of various concentration of calf thymus DNA (ct-DNA), has been studied in 7.5 mM phosphate buffer, pH = 7.2 and at various temperatures by UV-vis absorption, resonance light scattering (RLS) and fluorescence spectroscopy and viscosity measurement. Optical absorption and RLS measurements have demonstrated three different species of both porphyrins form in DNA solution. The thermodynamic parameters were calculated by van't Hoff equation at various temperatures. The values of -4.89 kJ.mol-1 and +65.98 J.mol-1.K-1 for Mn(III)5-CBPyP and -14.92 kJ.mol-1 and +15.46 J mol-1.K-1 for TMPyP were estimated for enthalpy and entropy changes of interaction, respectively. The data indicate that the process is exothermic and enthalpy- and entropy-driven, suggesting that electrostatic forces play a considerable role in the interaction process. The binding of both porphyins to DNA quenches fluorescence emission of ethidium bromide (EB) and the quenching process obeys linear Stern-Volmer relationship, indicating the quenching of electron transfer of EB from its binding sites by these porphyrins. The results of using these techniques indicate the external mode of binding for both porphyrins and a higher binding affinity of Mn(III)5-CBPyP with respect to Mn(III)TMPyP .

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Tello-Solis, S. R., and A. Hernandez-Arana. "Effect of irreversibility on the thermodynamic characterization of the thermal denaturation of Aspergillus saitoi acid proteinase." Biochemical Journal 311, no. 3 (November 1, 1995): 969–74. http://dx.doi.org/10.1042/bj3110969.

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The thermal denaturation of the acid proteinase from Aspergillus saitoi was studied by CD and differential scanning calorimetry (DSC). This process seemed to be completely irreversible, as protein samples that were heated to temperatures at which the transition had been completed and then cooled at 25 degrees C did not show any reversal of the change in the CD signal. Similar results were obtained with DSC. Nevertheless, we were able to detect the presence of reversibly unfolded species in experiments in which the enzyme solution was heated to a temperature within the transition region, followed by rapid cooling at 25 degrees C. Accordingly, the denaturation of behaviour of the acid proteinase seems to be consistent with the existence of one (or more) reversible unfolding transition followed by an irreversible step. The van't Hoff enthalpy, delta HvH, which corresponds to the reversible transition was calculated from extrapolation to infinite heating rate as 310 kJ.mol-1. This parameter was also determined from direct estimation of the equilibrium constant at several temperatures (delta HvH = 176 kJ.mol-1). Comparison of the average delta HvH with the calorimetric enthalpy (delta Hcal. = 770 kJ.mol-1) gave a value of 3.2 for the delta Hcal./delta HvH ratio, indicating that the molecular structure of the enzyme is probably formed by three or four cooperative regions, a number similar to that of the acid proteinase, pepsin. It should be noted that a completely different conclusion would be obtained from a straightforward analysis of the calorimetric curves, disregarding the effect of irreversibility on the denaturation process.

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Prakash Mishra, Shiv, and R. P. Singh. "THERMODYNAMIC BASED AQUEOUS SOLVATION AND DISSOCIATION OF BENZOIC ACID." International Journal of Advanced Research 11, no. 01 (January 31, 2023): 194–201. http://dx.doi.org/10.21474/ijar01/16006.

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In article, we have reported a thermodynamic based study of aqueous solvation of benzoic acid (C6H5COOH) at 288 to 318 Kelvin temperature. At this temperature range the dissociation constant (Ka) of benzoic acid into aqueous solvent has been determined by applying of titration method against standard basic solution of NaOH at different ionic strength of NaCl. Although, in observation, the value of Ka is being inversely proportional in respect of temperature in between 289 K to 303 K, and at higher temperature in between 303 K to 314 K, it being directly proportional. This reports that, there are no regular correlation in between temperature and Ka of that acid. Graphically, the plot has shown the value of Ka of benzoic acid is being 4.176 at 298 K temperature. In finding of precious results for benzoic acid solvation and its dissociation into water the applying Vant Hoff equation with Gibbs free energy change relationship (âˆ†G = âˆ†H - Tâˆ†S) for reaction (endothermic or exothermic) process at standard condition of thermodynamic parameters as in terms of enthalpy (H) and entropy (S). Where, the thermodynamic parameters value (in kJ.mol-1) are being as âˆ†G = 12.507, âˆ†H = 3.823 and âˆ†S = -29.14, but, at 298 K it is show that, the acid dissociation into aqueous is an endothermic process and non-spontaneous.

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29

Khalegh Bordbar, A., Manuchehr Davari, Elham Safaei, and Valiollah Mirkhani. "Aggregation and DNA binding characteristics of tetrakis(N,N',N″,N‴-tetramethyltetra-3,4-pridino)porphyrazine cobalt(II)." Journal of Porphyrins and Phthalocyanines 11, no. 02 (February 2007): 139–47. http://dx.doi.org/10.1142/s1088424607000187.

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The association behavior of tetrakis( N , N ', N ″, N ‴-tetramethyltetra-3,4-pridino)porphyrazine cobalt(II) ([ Co (II)3,4- TMTPPA ]4+) was investigated in aqueous solution at 25°C and various ionic strengths using optical absorption and resonance light scattering spectroscopies. The results show that [ Co (II)3,4- TMTPPA ]4+ does not have any affinity for aggregation due to increasing salt concentration and exists as the monomer form even in homogeneous aqueous solutions at high ionic strengths (more than 1 M concentration of NaCl ). The interaction of [ Co (II)3,4- TMTPPA ]4+ with calf thymus DNA in aqueous solution has also been studied in 5 mM phosphate buffer pH 7.2, by optical absorption and resonance light scattering spectroscopies, and thermal denaturation experiments. The appearance of hypochromicity of less than 10% and a bathochromic shift of Δλ ≤ 8 nm in the UV-vis spectra of [ Co (II)3,4- TMTPPA ]4+, an increase in the thermal melting point of DNA, and no enhancement in resonance light scattering spectra of porphyrazine due to interaction with DNA, indicates the minor outside-groove binding mode without any stack aggregate formation. The thermodynamics of the binding of [ Co (II)3,4- TMTPPA ]4+-DNA has also been studied. The binding constant (K) was obtained by analysis of optical absorption spectra of the above-mentioned complex at various DNA concentrations using SQUAD software. The value of K was estimated as 1.31 × 106 ± 1.174 M-1 at 25°C. The thermodynamic parameters were calculated by van't Hoff equation. The enthalpy and entropy changes were 48.77 ± 2.50 kJ . mol -1 and 280.77 ± 9.62 J . mol -1. K -1 at 25°C, respectively. The results indicate that the process is entropy driven suggesting that hydrophobic interactions are the main driving forces for complex formation. The increase of ionic strength due to the addition of NaCl , destabilized porphyrazine-DNA complexes, which indicates the competition of Na + ions with porphyrazine complexes for occupation of minor groove binding sites.

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Schmitz, Hans-Uwe, Wigand Hübner, and Theodor Ackermann. "Thermodynamic and Spectroscopic Characterization of the Berenil and Pentamidine Complexes with the Dodecanucleotide d(CGCGATATCGCG)2." Zeitschrift für Naturforschung C 50, no. 3-4 (April 1, 1995): 263–74. http://dx.doi.org/10.1515/znc-1995-3-416.

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The dodecanucleotide d(CGCGATATCGCG)2 was characterized by thermodynamic and UV-spectrophotometric measurements. A van’t Hoff enthalpy of ΔHuvv.H. ~ - 190 kJ/mol was determined for the thermal transition using UV spectroscopy. This value was confirmed by differential scanning calorimetry (DSC). In addition we obtained the thermodynamic data ΔHDSC = -405.1 kJ/mol, ΔSDSC = -1290 J/mol·K and ΔGDSC = -53.2 kJ/mol for the helix to coil transition of the dodecanucleotide. The association of berenil and the oligonucleotide was accompanied with a stabilization of the host duplex (increase in Tm) and an increase in the van’t Hoff enthalpy. The berenil binding parameters (ΔΔHDSC = -32.6 kJ/mol, ΔΔSDSC = -72 J/mol·K and ΔΔGDSC = -11.1 kJ/mol) revealed significant differences compared to those of the pentamidine aggregation (ΔΔHDSC = -23.7 kJ/mol, ΔΔSDSC = -53 J/mol·K and ΔΔGDSC = -7.8 kJ/mol). The transition of the pure oligonucleotide was characterized by a substantial amount of intermediate states (σDSC = 0.43) which decreased significantly upon binding of the drugs (σDSC ~ 0.80). The structural features of the complexes were analyzed by FT-IR spectroscopy. From these experiments we conclude that the configurations in the berenil and pentamidine complexes are different.

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Ghazwani, Mohammed, Prawez Alam, Mohammed H. Alqarni, Hasan S. Yusufoglu, and Faiyaz Shakeel. "Solubilization of Trans-Resveratrol in Some Mono-Solvents and Various Propylene Glycol + Water Mixtures." Molecules 26, no. 11 (May 21, 2021): 3091. http://dx.doi.org/10.3390/molecules26113091.

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This research deals with the determination of solubility, Hansen solubility parameters, dissolution properties, enthalpy–entropy compensation, and computational modeling of a naturally-derived bioactive compound trans-resveratrol (TRV) in water, methanol, ethanol, n-propanol, n-butanol, propylene glycol (PG), and various PG + water mixtures. The solubility of TRV in six different mono-solvents and various PG + water mixtures was determined at 298.2–318.2 K and 0.1 MPa. The measured experimental solubility values of TRV were regressed using six different computational/theoretical models, including van’t Hoff, Apelblat, Buchowski–Ksiazczak λh, Yalkowsly–Roseman, Jouyban–Acree, and van’t Hoff–Jouyban–Acree models, with average uncertainties of less than 3.0%. The maxima of TRV solubility in mole fraction was obtained in neat PG (2.62 × 10−2) at 318.2 K. However, the minima of TRV solubility in the mole fraction was recorded in neat water (3.12 × 10−6) at 298.2 K. Thermodynamic calculation of TRV dissolution properties suggested an endothermic and entropy-driven dissolution of TRV in all studied mono-solvents and various PG + water mixtures. Solvation behavior evaluation indicated an enthalpy-driven mechanism as the main mechanism for TRV solvation. Based on these data and observations, PG has been chosen as the best mono-solvent for TRV solubilization.

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M. Alshahrani, Saad, and Faiyaz Shakeel. "Solubility Data and Computational Modeling of Baricitinib in Various (DMSO + Water) Mixtures." Molecules 25, no. 9 (May 1, 2020): 2124. http://dx.doi.org/10.3390/molecules25092124.

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The solubility and thermodynamic analysis of baricitinib (BNB) in various dimethyl sulfoxide (DMSO) + water mixtures were performed. The “mole fraction solubilities (xe)” of BNB in DMSO and water mixtures were determined at “T = 298.2–323.2 K” and “p = 0.1 MPa” using an isothermal saturation technique. “Hansen solubility parameters (HSPs)” of BNB, pure DMSO, pure water and “DMSO + water” mixtures free of BNB were also estimated. The xe data of BNB was regressed well by five different thermodynamics-based co-solvency models, which included “Apelblat, Van’t Hoff, Yalkowsky-Roseman, Jouyban-Acree and Jouyban-Acree-Van’t Hoff models” with overall deviations of <5.0%. The highest and lowest xe value of BNB was computed in pure DMSO (1.69 × 10−1 at T = 323.2 K) and pure water (2.23 × 10−5 at T = 298.2 K), respectively. The HSP of BNB was found to be closer to that of pure DMSO. Based on activity coefficient data, maximum solute–solvent molecular interactions were observed in BNB-DMSO compared to BNB-water. The results of “apparent thermodynamic analysis” indicated endothermic and entropy-drive dissolution of BNB in all “DMSO + water” combinations including mono-solvents (water and DMSO). “Enthalpy-entropy compensation analysis” showed enthalpy-driven to be the main mechanism of solvation of BNB.

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Xie, Jiao, Kanghuai Zhang, Haitao Wang, Xin Yang, Wenbin Mao, Chenwei Liu, and Na Wang. "Determination of the Solubility, Dissolution Enthalpy, and Entropy of Icariin in Acetone, Acetoacetate, Chloroform, and Light Petroleum." Natural Product Communications 15, no. 11 (November 2020): 1934578X2097149. http://dx.doi.org/10.1177/1934578x20971491.

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The solubility of icariin in acetone, acetoacetate, chloroform, and light petroleum in the 283.2‐318.2 K range was measured by ultraviolet-visible spectrophotometry. As the temperature increased, the solubility of icariin in the 4 solvents gradually increased. The solubility data correlated with the modified Apelblat equation. The dissolution enthalpy and entropy of icariin were determined using van’t Hoff plots. The dissolution enthalpy and entropy of icariin in the 4 solvents increases as acetone >acetoacetate >chloroform >light petroleum, which can be explained by the difference of the polarity indices between them. The polarity indices of the solvents affect the solubility behavior.

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Ge, Qiang, Xu Jia Ding, Gang Wu, Song Liang, and Si Zhu Wu. "Study on the Microstructure and Mechanical Properties of PET and PET/PTT Blends." Key Engineering Materials 340-341 (June 2007): 1085–90. http://dx.doi.org/10.4028/www.scientific.net/kem.340-341.1085.

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In this study, the thermal analysis FTIR Micro-Spectroscopy method was used to observe the energy changes of the functional groups of Poly(ethylene terephthalate) (PET) during manufacturing progress. The conformational apparent enthalpy H in the melting process has been calculated by the van’t Hoff equation at the constant pressure and then plotted with temperature. The structure and properties of PET/PTT (Polytrimethylene Terephthalate) blends with different blending ratio had also been studied by using DSC and DMA analysis.

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Ambrosone, Luigi, and Raffaele Ragone. "Electrochemical methods of evaluating the van’t Hoff enthalpy in reactions involving biological macromolecules." International Journal of Biological Macromolecules 27, no. 4 (July 2000): 241–44. http://dx.doi.org/10.1016/s0141-8130(00)00138-0.

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Chen, Zi Dan, Kun Kun Wang, Xue Li, Sheng Wang, Sha Wu, Min Li, and Er Hong Duan. "Solubility and Thermodynamic Properties of L-Proline in Methanol-Dichloromethane Mixtures." Applied Mechanics and Materials 775 (July 2015): 185–90. http://dx.doi.org/10.4028/www.scientific.net/amm.775.185.

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The solubility of L-proline in binary solvents of methanol and dichloromethane were measured by a dynamic method via a laser monitoring technique. In the binary solvent mixtures, the solubility increases with the increasing of temperature and proportion of the methanol. The experimental solubility were fitted to modified Apelblat equation and Van’t Hoff equation in this work can be used as essential data and models in the purification process of L-proline. The dissolving process is endothermic and the dissolution driving force converts from enthalpy-driving to entropy-driving.

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Shakeel, Faiyaz, Nazrul Haq, Ibrahim A. Alsarra, and Sultan Alshehri. "Solubility, Hansen Solubility Parameters and Thermodynamic Behavior of Emtricitabine in Various (Polyethylene Glycol-400 + Water) Mixtures: Computational Modeling and Thermodynamics." Molecules 25, no. 7 (March 28, 2020): 1559. http://dx.doi.org/10.3390/molecules25071559.

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This study was aimed to find out the solubility, thermodynamic behavior, Hansen solubility parameters and molecular interactions of an antiviral drug emtricitabine (ECT) in various “[polyethylene glycol-400 (PEG-400) + water]” mixtures. The solubility of ECT in mole fraction was determined at “T = 298.2 to 318.2 K” and “p = 0.1 MPa” using an isothermal method. The experimental solubilities of ECT in mole fraction were validated and correlated using various computational models which includes “Van’t Hoff, Apelblat, Yalkowsky-Roseman, Jouyban-Acree and Jouyban-Acree-Van’t Hoff models”. All the models performed well in terms of model correlation. The solubility of ECT was increased with the raise in temperature in all “PEG-400 + water” mixtures studied. The highest and lowest solubility values of ECT were found in pure PEG-400 (1.45 × 10−1) at “T = 318.2 K” and pure water (7.95 × 10−3) at “T = 298.2 K”, respectively. The quantitative values of activity coefficients indicated higher interactions at molecular level in ECT and PEG-400 combination compared with ECT and water combination. “Apparent thermodynamic analysis” showed an “endothermic and entropy-driven dissolution” of ECT in all “PEG-400 + water” combinations studied. The solvation nature of ECT was found an “enthalpy-driven” in each “PEG-400 + water” mixture studied.

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R. Delgado, Montserrat. "Structure and Stability of Gas Adsorption Complexes in Periodic Porous Solids as Studied by VTIR Spectroscopy: An Overview." Applied Sciences 10, no. 23 (November 30, 2020): 8589. http://dx.doi.org/10.3390/app10238589.

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Variable-temperature infrared (VTIR) spectroscopy is an instrumental technique that enables structural characterization of gas-solid adsorption complexes by analysis of meaningful vibrational modes, and simultaneous determination of the standard enthalpy change (ΔH0) involved in the gas adsorption process, which allows one to quantify the stability of the corresponding complex. This is achieved by a van’t Hoff analysis of a set of IR spectra recorded over a sufficiently large temperature range. Herein, the use of this versatile spectroscopic technique is demonstrated by reviewing its application to the study of carbon monoxide, carbon dioxide and dinitrogen adsorption on several (alkaline) zeolites, which can be regarded as the archetype of periodic porous solids.

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Alghaith, Adel F., Wael A. Mahdi, Nazrul Haq, Sultan Alshehri, and Faiyaz Shakeel. "Solubility and Thermodynamic Properties of Febuxostat in Various (PEG 400 + Water) Mixtures." Materials 15, no. 20 (October 19, 2022): 7318. http://dx.doi.org/10.3390/ma15207318.

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The solubility of the poorly soluble medicine febuxostat (FXT) (3) in various {polyethylene glycol 400 (PEG 400) (1) + water (H2O) (2)} mixtures has been examined at 298.2–318.2 K and 101.1 kPa. FXT solubility was measured using an isothermal method and correlated with “van’t Hoff, Apelblat, Buchowski–Ksiazczak λh, Yalkowsky–Roseman, Jouyban–Acree, and Jouyban–Acree-van’t Hoff models”. FXT mole fraction solubility was enhanced via an increase in temperature and PEG 400 mass fraction in {(PEG 400 (1) + H2O (2)} mixtures. Neat PEG 400 showed the highest mole fraction solubility of FXT (3.11 × 10–2 at 318.2 K), while neat H2O had the lowest (1.91 × 10–7 at 298.2 K). The overall error value was less than 6.0% for each computational model, indicating good correlations. Based on the positive values of apparent standard enthalpies (46.72–70.30 kJ mol−1) and apparent standard entropies (106.4–118.5 J mol−1 K−1), the dissolution of FXT was “endothermic and entropy-driven” in all {PEG 400 (1) + H2O (2)} mixtures examined. The main mechanism for FXT solvation in {PEG 400 (1) + H2O (2)} mixtures was discovered to be an enthalpy-driven process. In comparison to FXT-H2O, FXT-PEG 400 showed the strongest molecular interactions. In conclusion, these results suggested that PEG 400 has considerable potential for solubilizing a poorly soluble FXT in H2O.

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Shao, Huaiyu, Gongbiao Xin, Xingguo Li, and Etsuo Akiba. "Thermodynamic Property Study of Nanostructured Mg-H, Mg-Ni-H, and Mg-Cu-H Systems by High Pressure DSC Method." Journal of Nanomaterials 2013 (2013): 1–7. http://dx.doi.org/10.1155/2013/281841.

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Mg, Ni, and Cu nanoparticles were synthesized by hydrogen plasma metal reaction method. Preparation of Mg2Ni and Mg2Cu alloys from these Mg, Ni, and Cu nanoparticles has been successfully achieved in convenient conditions. High pressure differential scanning calorimetry (DSC) technique in hydrogen atmosphere was applied to study the synthesis and thermodynamic properties of the hydrogen absorption/desorption processes of nanostructured Mg-H, Mg-Ni-H, and Mg-Cu-H systems. Van’t Hoff equation of Mg-Ni-H system as well as formation enthalpy and entropy of Mg2NiH4was obtained by high pressure DSC method. The results agree with the ones by pressure-composition isotherm (PCT) methods in our previous work and the ones in literature.

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Shakeel, Faiyaz, Mohsin Kazi, Fars K. Alanazi, and Prawez Alam. "Solubility of Cinnarizine in (Transcutol + Water) Mixtures: Determination, Hansen Solubility Parameters, Correlation, and Thermodynamics." Molecules 26, no. 22 (November 22, 2021): 7052. http://dx.doi.org/10.3390/molecules26227052.

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Between 293.2 and 313.2 K and at 0.1 MPa, the solubility of the weak base, cinnarizine (CNZ) (3), in various {Transcutol-P (TP) (1) + water (2)} combinations is reported. The Hansen solubility parameters (HSP) of CNZ and various {(TP) (1) + water (2)} mixtures free of CNZ were also predicted using HSPiP software. Five distinct cosolvency-based mathematical models were used to link the experimentally determined solubility data of CNZ. The solubility of CNZ in mole fraction was increased with elevated temperature and TP mass fraction in {(TP) (1) + water (2)} combinations. The maximum solubility of CNZ in mole fraction was achieved in neat TP (5.83 × 10−2 at 313.2 K) followed by the minimum in neat water (3.91 × 10−8 at 293.2 K). The values of mean percent deviation (MPD) were estimated as 2.27%, 5.15%, 27.76%, 1.24% and 1.52% for the “Apelblat, van’t Hoff, Yalkowsky–Roseman, Jouyban–Acree, and Jouyban–Acree–van’t Hoff models”, respectively, indicating good correlations. The HSP value of CNZ was closed with that of neat TP, suggesting the maximum solubilization of CNZ in TP compared with neat water and other aqueous mixtures of TP and water. The outcomes of the apparent thermodynamic analysis revealed that CNZ dissolution was endothermic and entropy-driven in all of the {(TP) (1) + water (2)} systems investigated. For {(TP) (1) + water (2)} mixtures, the enthalpy-driven mechanism was determined to be the driven mechanism for CNZ solvation. TP has great potential for solubilizing the weak base, CNZ, in water, as demonstrated by these results.

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42

Doi, Koichi, Satoshi Hino, Hiroki Miyaoka, Takayuki Ichikawa, and Yoshitsugu Kojima. "Thermodynamic Characterization on Hydrogen Absorption and Desorption Reactions of Lithium – Silicon Alloy." Materials Science Forum 654-656 (June 2010): 2815–18. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.2815.

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Lithium hydride LiH is one of the attractive hydrogen storage materials, because it stores 12.7 mass% of H2. However, H2 desorption reaction occurs over 600 °C due to the large enthalpy change of H2 desorption Ho = 181 kJ/mol H2. The purpose of this work is to control the enthalpy change of LiH to much lower value by a mechanical alloying with Si, where the Li-Si alloy is thermodynamically more stable than Li. The alloy was synthesized from Li granule and Si powder by a mechanical alloying method. The H2 absorption and desorption properties were characterized by High-Pressure Differential Scanning Calorimetry and Thermogravimetry - Differential Thermal Analysis - Mass Spectroscopy, and X-ray diffraction measurement. Pressure - Composition - Isotherm measurements were performed at 400, 450, and 500 °C to estimate the enthalpy change. From the results, it was confirmed that reversible H2 ab/desorption reactions of the Li-Si alloy were expressed as 7LiH + 3Si ↔ (3/7)Li12Si7 + (13/7)LiH + (18/7)H2 ↔ Li7Si3 + (7/2)H2 (theoretically 5.0 mass% H2) at 400 °C. From van’t Hoff plot obtained by the results of PCI measurements, the enthalpy change of the former reaction was estimated to be Ho = 103 kJ/mol H2, which is lower than that of LiH.

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43

Hanyková, Lenka, Ivan Krakovský, Eliška Šestáková, Julie Šťastná, and Jan Labuta. "Poly(N,N′-Diethylacrylamide)-Based Thermoresponsive Hydrogels with Double Network Structure." Polymers 12, no. 11 (October 27, 2020): 2502. http://dx.doi.org/10.3390/polym12112502.

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Temperature response of double network (DN) hydrogels composed of thermoresponsive poly(N,N′-diethylacrylamide) (PDEAAm) and hydrophilic polyacrylamide (PAAm) or poly(N,N′-dimethylacrylamide) (PDMAAm) was studied by a combination of swelling measurements, differential scanning calorimetry (DSC) and 1H NMR and UV-Vis spectroscopies. Presence of the second hydrophilic network in DN hydrogels influenced their thermal sensitivity significantly. DN hydrogels show less intensive changes in deswelling, smaller enthalpy, and entropy changes connected with phase transition and broader temperature interval of the transition than the single network (SN) hydrogels. Above the transition, the DN hydrogels contain significantly more permanently bound water in comparison with SN hydrogels due to interaction of water with the hydrophilic component. Unlike swelling and DSC experiments, a rather abrupt transition was revealed from temperature-dependent NMR spectra. Release study showed that model methylene blue molecules are released from SN and DN hydrogels within different time scale. New thermodynamical model of deswelling behaviour based on the approach of the van’t Hoff analysis was developed. The model allows to determine thermodynamic parameters connected with temperature-induced volume transition, such as the standard change of enthalpy and entropy and critical temperatures and characterize the structurally different states of water.

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Marchetti, Nicola, Pier Paolo Giovannini, Martina Catani, Luisa Pasti, and Alberto Cavazzini. "Thermodynamic Insights into the Separation of Carotenoids in Reversed-Phase Liquid Chromatography." International Journal of Analytical Chemistry 2019 (January 3, 2019): 1–7. http://dx.doi.org/10.1155/2019/7535813.

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The retention mechanism of four major carotenoids, two xanthophylls (i.e., lutein and zeaxanthin) and two carotenes (i.e., lycopene and β-carotene), was investigated in reversed-phase liquid chromatography with the aim of thermodynamic analysis. The experimental variables considered in this study were the composition of mobile phase (MP) and the temperature. Chromatographic elutions were undertaken under linear, isocratic conditions by using a C18 stationary phase, four different MP compositions (by varying the ratio methanol/acetonitrile from 66.5/28.5 to 47.5/47.5 v/v), and column temperatures in the range 283–313 K. Traditional Van’t Hoff analysis has been used to estimate changes of standard enthalpy (ΔH∘) and Gibbs free energy (ΔG∘) associated with the solute transfer from the mobile to the stationary phase at each mobile phase composition. The thermodynamic quantities have been correlated to the structure of investigated carotenoids and their interaction with the octadecyl silica stationary phase.

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45

Largitte, L., and P. Lodewyckx. "Kinetics and Thermodynamics of the Adsorption of Lead (II) on a Activated Carbon from Coconut Shells." Eurasian Chemico-Technological Journal 15, no. 4 (October 15, 2013): 283. http://dx.doi.org/10.18321/ectj233.

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The effect of temperature on the adsorption of lead by an activated carbon from coconut shells is investigated. The pseudo second order equation is applied to the kinetic data obtained at different temperatures in order to determine the adsorption rate constants at these temperatures. Then, the Arrhenius equation is applied to the rate constants to determine the activation energy of the sorption reaction and the pre-exponential factor. By applying the Eyring equation to the rate constants, the standard thermodynamic activation parameters of the sorption reaction can also be calculated. In addition, the isotherms of lead adsorption on the activated carbon from coconut shells, at different temperatures, are determined and fitted by the Langmuir equation. The Van’t Hoff equation is applied to the Langmuir equilibrium constants in order to determine the standard enthalpy of the sorption reaction. The other standard thermodynamic parameters<br />(Gibbs standard enthalpy and standard entropy) are deduced. The isosteric standard sorption enthalpy is also determined by using both the classical approach and an adapted Clausius Clapeyron equation. The results are identical. The value obtained is higher, but more correct than that of Langmuir. On the basis of these<br />thermokinetic parameters, the activated carbon from Coconut shells can be considered as a very efficient carbon for the sorption of lead and its sorption efficiency (rate and quantity) increase with the temperature.

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46

Wang, Yongxi, Dandan Liu, Yili Zhang, Yanmei Tang, Jingfeng Zhao, and Baochun Shen. "Synthesis of a Novel Chiral Stationary Phase by (R)-1,1′-Binaphthol and the Study on Mechanism of Chiral Recognition." Symmetry 10, no. 12 (December 3, 2018): 704. http://dx.doi.org/10.3390/sym10120704.

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(R)-6-Acrylic-BINOL CSP, a novel chiral stationary phase was prepared by (R)-Binaphthol (R-BINOL) by introducing the acrylic group into the 6-position of (R)-BINOL before bonding it to the surface of silica gel. The structure of the CSP was characterized by IR, SEM, and element analysis. This new material was tested for its potential as a CSP for HPLC under normal phase conditions, especially for conjugated compounds. Six solutes were chosen to evaluate the chiral separation ability of the novel CSP. The effects of the mobile phase and temperature on enantioseparation were studied, and the chiral recognition mechanism was also discussed. The results showed that the space adaptability and π-π stacking between the solutes and the CSP affected the retention and enantioseparation. The Van’t Hoff curve indicated that under the experimental conditions, the separation mechanism of six solutes did not change, which were all enthalpy driven.

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47

Huang, Fang, and Ying Liu. "Study of Interaction between Human Serum Albumin and Miconazole Nitrate Using Multi-Spectroscopic Methods." Advanced Materials Research 955-959 (June 2014): 475–78. http://dx.doi.org/10.4028/www.scientific.net/amr.955-959.475.

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The interaction of human serum albumin (HSA) and miconazole nitrate (MIN) had been studied by multi-spectroscopic methods. The inner filter effect was corrected before used the original data. The results indicated that MIN induced the fluorescence quenching of HSA was static quenching procedure. According to the Van’t Hoff equation, the interaction of HSA and MIN was determined by negative enthalpy change and positive entropy change, which showed that electrostatic forces were the major force in the binding process. The displacement experiments revealed that MIN binds in the vicinity of site I of HSA. The binding distance between Trp214 of HSA and MIN was 3.82 nm. Furthermore, the alternations of HSA secondary structure were calculated by FT-IR spectra. Upon formation of HSA-MIN complexes, the amount of α-helix structure reduced from 43.28% to 29.92%, β-sheet reduced from 22.59% to 18.79%, β-turn increased from 20.33% to 30.11% and random increased from 13.80% to 21.19%.

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Alavianmehr, Mohammad Mehdi, Reza Yousefi, Fatemeh Keshavarz, and Delara Mohammad-Aghaie. "Probing the binding of thioTEPA to human serum albumin using spectroscopic and molecular simulation approaches." Canadian Journal of Chemistry 92, no. 11 (November 2014): 1066–73. http://dx.doi.org/10.1139/cjc-2013-0571.

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The present work is devoted to probing the molecular interaction of N,N′,N″-triethylenethiophosphoramide (thioTEPA) with human serum albumin (HSA) using UV-visible and fluorescence spectroscopies. Further, molecular dynamics and molecular docking simulations were used to investigate the binding site of thioTEPA. The outcomes of the spectroscopic observations and also the Stern−Volmer and van’t Hoff equations were employed to determine the binding thermodynamic parameters. It was found out that the interaction of thioTEPA with HSA is enthalpy driven through a quenching mechanism that is both static and dynamic at domain I of HSA. No significant changes in the local and overall secondary structure, polarity, and hydrophobicity of HSA were observed. The low values of binding free energies and binding constants are evidence for necessary high dosage of thioTEPA in chemotherapies. These results may be attributed to the spherical geometry and steric hindrance of the free vibrating aziridinyl groups of thioTEPA.

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Tinjacá, Darío A., Fleming Martínez, Ovidio A. Almanza, M. Ángeles Peña, Abolghasem Jouyban, and William E. Acree. "Increasing the Equilibrium Solubility of Meloxicam in Aqueous Media by Using Dimethyl Sulfoxide as a Cosolvent: Correlation, Dissolution Thermodynamics and Preferential Solvation." Liquids 2, no. 3 (August 12, 2022): 161–82. http://dx.doi.org/10.3390/liquids2030011.

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Meloxicam is widely prescribed as an analgesic and anti-inflammatory drug in human therapeutics. Owing the very low aqueous solubility of meloxicam, this property has been studied in dimethyl sulfoxide (DMSO)-aqueous solvent systems at several temperatures from 273.15 to 313.15 K to expand the solubility database about analgesic drugs in mixed solvents. The flask shake method followed by ultraviolet-visible (UV-vis) spectrophotometry analysis were used for meloxicam solubility determinations. A number of cosolvency models, including the Jouyban–Acree model, were challenged for solubility correlation/prediction of this drug in these mixtures. The van’t Hoff and Gibbs equations were employed to calculate the apparent standard thermodynamic quantities relative to dissolution and mixing processes. The inverse Kirkwood–Buff integral method was employed for calculating the preferential solvation parameters of meloxicam by DMSO in the mixtures. Meloxicam solubility increases with increasing temperature and maximum solubilities are observed in neat DMSO at all temperatures studied. Dissolution processes were endothermic in all cases and entropy-driven in the composition interval of 0.40 ≤ x1 ≤ 1.00. A nonlinear enthalpy–entropy relationship was observed in the plot of enthalpy vs. Gibbs energy for drug transfer processes. Meloxicam is preferentially solvated by water in water-rich mixtures but preferentially solvated by DMSO in the composition interval of 0.21 < x1 < 1.00.

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50

Yadav, Jyoti, Dan G. Dumitrescu, Thomas Kendall, Carmen Guguta, and Swati A. Patel. "Effect of Solvent Composition on Solubility, Thermodynamics, Metastable Zone Width (MSZW) and Crystal Habit of L-Ascorbic Acid." Crystals 12, no. 12 (December 9, 2022): 1798. http://dx.doi.org/10.3390/cryst12121798.

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This work investigates the effect of different solvent systems on solubility, thermodynamics, metastable zone width (MSZW), and crystal habit of ascorbic acid, in order to help optimize its crystallization process. The solubility curves and metastable zone (MSZ) limits were determined experimentally using the polythermal method in pure solvents: water and alcohols (methanol/ethanol/isopropanol), as well as water-alcohol binary solvent systems. The solubility decreases with increasing alcohol composition for all solvent systems. The solubility data were well correlated using the Jouyban–Acree model as a function of two variables: temperature and solvent composition. The dissolution enthalpy (ΔHdiss), dissolution entropy (ΔSdiss), and Gibbs free energy (ΔGdiss) were determined using Van’t Hoff and Jouyban–Acree models. The thermodynamic properties increase with increasing alcohol composition. The lowest and highest values of enthalpy were obtained for water (20.52 kJ mol −1) and isopropanol (35.33 kJ mol−1), respectively. Pure alcohols as solvents widen the metastable zone width, indicating high supersaturation required for the nucleation. Crystal images captured during cooling crystallization in water confirm the cubic crystal habit formation, whereas increasing alcohol composition in the solvent system promotes preferential growth along one crystallographic axis, leading to elongated prism-shaped crystals in methanol and ethanol and needle-shaped crystals in isopropanol.

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Journal articles on the topic 'Van’t Hoff enthalpy of solution'

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