Gibbs Free Energy Of Activation Research Articles

Volumetric behaviour of tetra-n-butyl ammonium bromide in various solvents at different temperatures

Measurement of ultrasonic velocity, density and viscosity of solutions of Tetra Butyl Ammonium Bromide have been carried outin different solvents (water, methanol, ethanol, 1-propanol and 1-butanol) as functions of concentration (1 to 0.1 M) at different temperatures (298.15 K to 318.15 K). Using these experimental data, various acoustical and apparent parameters such as acoustical impedance, intermolecular free length, adiabatic compressibility, molar compressibility, Van der Waals constant, relaxation strength, apparent molar isentropic compressibility, apparent molar volume have been evaluated. Further, some thermodynamic parameters such as Gibbs free energy of activation, enthalpy and entropy of activation have been evaluated. All these parameters have been evaluated to understand type of interactions present in studied solutions.

Synthesis of CuInS2 Particles in Aqueous Solution for Printable Photovoltaic Device

CuInS2(CIS) is one of the most effective photovoltaic devices with high stability and efficiency, since the bandgap of CIS is 1.5eV while ideal band gap for solar cell is 1.4eV. Moreover, unlike Cu(In,Ga)Se2(CIGS), it does not contain toxic materials, such as Se. However, since vaporizing temperature of four elements (Cu, In, Ga, Se) is extremely different, productivity under the gas phase is relatively low, which read the large amount of waste of resources. Thus, it is required to develop a synthesis method of CIS solar cell materials within liquid phase. Here, we have already developed a synthesizing method of single phase and homogenous copper-indium(CI) alloy nanoparticles in aqueous solution. In this method, the concentration of the metal complexes in the solution are calculated by using the critical stability constants, and the reduction reaction rate of both metal ions is also controlled. Synthesized CI nanoparticles were spin coted onto Mo/glass substrate and selenized, consequently it shows the photo voltaic effect. Thus, printable solar cells can be formed by using this method. The synthesizing method contains the selenization which is a sort of evaporation method, so it is not liquid process completely. To synthesize CIS solar cells without the selenization, we tried to sulfurize CI nanoparticles but CIS particles were not synthesized. It is difficult to sulfurize CI nanoparticles because they are stable and hard to react with sulfur ions, so it is necessary to synthesize from copper ions and indium ions to CuInS2 particles directly. However, nobody can synthesize CuInS2 particles in aqueous solution because there is a difference between the sulfurization reaction rate of copper and indium ions. If the sulfurization reaction rate of both metal ions is different, they are sulfurized independently to form their own sulfides, such as Cu2S or CuS and In2S3. It is necessary to control and approximate the sulfurization reaction rate of both metal ions for synthesis of CuInS2 particles. Here, in the sulfurization process, the sulfurization reaction rate is correlation with potential energy such as gibbs free energy (ΔG) or activation energy (Ea ). Hence, CuInS2 particles can be synthesized under the condition that the ΔG or Ea in the sulfurization reaction of copper and indium ions are approximated. To synthesize CuInS2 particles in aqueous solution, we tried to approximate the ΔG of the sulfurization reaction of copper and indium ions. By calculating ΔGCu2S and ΔGIn2S3 , we obtained the correlation of KIn and KCu and we were able to select appropriate complexing agents, so we tried to synthesize CuInS2 particles by using these reagents. XRD data indicates that several peaks with a dominant CuInS2 peak were observed. From the above results, it can be said that the synthesis of the precursor of CuInS2 particles in aqueous solution was successful because the Ea of the sulfurization process are approximated in both metal ions. In addition, it was found that the ΔG of copper and indium ions are approximated in the sulfurization system (Cu-In-IDA), so it is necessary to control and approximate both the ΔG and Ea for synthesis of CuInS2 particles in aqueous solution. Although the precursor of CuInS2 were synthesized in aqueous solution, the size and shape of the particles were not uniform. Therefore, for preventing degradation of conversion efficiency, it is needed to develop a technique for homogenizing the shape and the size of the particles. Detailed and another results will be introduced in our presentation. This work has been supported by the Grant-in-Aid for Scientific Research (B) (18H03416).

Synthesis, Spectroscopic Studies, and Biological Activity of Some New N2O2 Tetradentate Schiff Base Metal Complexes

The new tetradentate Schiff base N,N′-ethylene bis[1-ethyl-6-fluoro-4-imine-7-(piperazine-1-yl)-quinoline-3-carboxylic acid] (Nor-en) has been synthesized. Its chelated complexes with Co(II), Ni(II), Cu(II), Zn(II), Y(III), Zr(IV), La(III), and U(VI) are characterized using molar conductivity, magnetic moment, FT-IR, UV-Vis, 1H NMR, and mass spectra, and thermal analysis. It is determined that the complexes have monomeric structures and exist in the octahedral configuration. The molar conductance values indicate the electrolytic nature of the complexes. According to the spectroscopic data, the complexes share the same coordination environment around the metal ions, consisting of N2O2 and one or two water molecules. The thermodynamic parameters (activation energy, E*, entropy, ΔS*, enthalpy, ΔH*, and Gibbs free energy, ΔG*) are calculated using Coats-Redfern and Horowitz-Metzger methods. The carried out tests indicate the compounds’ high antibacterial activity against Staphylococcus aureus, Bacillus cereus, and Salmonella typhi. Anticancer activity of the ligand and its metal complexes is evaluated against HepG-2 cells (human Hepatocellular carcinoma) and determined to be very low.

Spectroscopic and thermodynamic interaction studies of anti-diabetic drug with globular proteins

Drug-protein interaction is a fundamental problem in estimating the serious side effects of the drug. Hence, the main objective of this study was to study the interaction of acarbose with three different globular proteins i.e.; bovine serum albumin (BSA), human serum albumin (HSA), and hemoglobin (Hb) via UV-Visible absorption spectroscopic analysis. We were determined physicochemical parameters, binding constant, distribution constant and thermodynamic parameters activation energy, enthalpy, entropy, and Gibbs free energy by using UV-visible data. These both properties of acarbose-protein complexes indicated that the hydrogen bonding and weak van der Waals force played a major role in the interaction for complexation. The binding of acarbose with different proteins leads to change in the structure of protein folding which confirms by physicochemical and thermodynamic analysis.

A DFT investigation of the retro-ene reactions of β-hydroxyacetylenes: concerted or stepwise mechanism

The retro-ene reactions of β-hydroxyacetylene and its 10 derivatives have been investigated theoretically at the B3LYP/6-31+G(d) level. The reactions are found to proceed through asynchronous concerted transition states. The thermodynamic data reveal that the reactions are exergonic with increase in the standard entropy. However, due to high values of the activation Gibbs free energy (∆G#) and negative values of the activation entropy (∆S#), reactions occur at elevated temperatures. The substituent groups in general do not have pronounced effect on the activation enthalpies, except the phenyl group in which case, it is lowered. The concerted versus stepwise mechanism has been investigated by complete active space-self consistent field (CASSCF) calculations also.

Molecular interactions of gentamicin sulphate in aqueous-l-asparagine/l-glutamine solutions at different temperatures: Volumetric, acoustic and viscometric properties

The solute-solute and solute-solvent interactions are investigated by using the experimental values densities, ρ, ultrasonic speeds, u and viscosities, η of gentamicin sulphate in water and in aqueous l-asparagine/l-glutamine (1% and 2% l-asparagine/l-glutamine in water) solvents at temperatures (293.15, 298.15, 303.15, 308.15, 313.15 and 318.15) K and at atmospheric pressure. The experimental ρ and u data have been used to calculate the apparent molar volumes, Vφ, limiting apparent molar volumes, Vϕ°, apparent molar compressibilities, Ks, ϕ, limiting apparent molar compressibilities, Ks, ϕ°, transfer volumes, Vϕ, tr°, transfer compressibilities, Ks, ϕ, tr° and limiting partial molar expansivity of solute, Eϕ°. Also, the Falkenhagen Coefficients, A and Jones-Dole coefficients, B were evaluated from experimental viscosity data. The Gibbs free energies of activation of viscous flow per mole of solvent, Δμ1°# and per mole of solute, Δμ2°#, entropies, ΔSο and enthalpies, ΔHο of activation of viscous flow were also calculated and discussed in terms of transition state theory. These parameters have been discussed in connection with the electrostatic interactions between the zwitterionic groups of amino acids and drug molecules. The structure-making/breaking ability of the drug in these solutions was also analyzed using the signs and magnitudes of (∂2Vϕ°/∂T2) and dB/dT coefficients.

Thermodynamic and theoretical investigations on [Emim][Bf4]/[Bmim][Bf4] and aniline binary mixtures

Viscosity and refractive index values are measured for various binary compositions of 1-ethyl-3-methylimidazolium tetrafluoroborate/1-butyl-3-methylimidazolium tetrafluoroborate and aniline at temperatures from T = (293.15 to 323.15) K under atmospheric pressure. The experimental data is used to calculate molar Gibbs free energy of activation, enthalpy, entropy and also the excess values of viscosity, refractive index, molar Gibbs free energy of activation. Various theoretical models are used to estimate the refractive index values. Redlich-Kister equation is used to estimate the deviations between the calculated and experimental excess values. The variations in the calculated parameters are analysed to understand the nature of molecular interactions between the chemical species. The assumptions on the behaviour of molecular interactions from the analysis of excess parameters are supported by the experimental and computational FT-IR studies.

Understanding the Role of Surface Oxygen in Hg Removal on Un-Doped and Mn/Fe-Doped CeO2 (111).

Effects of surface-adsorbed O and lattice O for the CeO2 (111) surface on Hg removal has been researched. In this work, periodic calculations based on density functional theory (DFT) were performed with the on-site Coulomb interaction. Hg is oxidized to HgO via the surface-adsorbed O by overcoming a Gibbs free energy barrier of 114.1 kJ·mol-1 on the CeO2 (111) surface. Mn and Fe doping reduce the activation Gibbs free energy for the Hg oxidation, and energies of 70.7 and 49.6 kJ·mol-1 are needed on Ce0.96 Mn0.04 O2 (111) and Ce0.96 Fe0.04 O2 (111) surfaces. Additionally, lattice O also plays an important role in Hg removal. Hg cannot be oxidized leading to the formation of HgO on the un-doped CeO2 (111) surface owing to the inertness of lattice O, which can be easily oxidized to HgO on Ce0.96 Mn0.04 O2 (111) and Ce0.96 Fe0.04 O2 (111) surfaces. It can be seen that both surface-adsorbed O and lattice O play important roles in removing Hg. The present study will shed light on understanding and developing Hg removal technology on un-doped and Mn/Fe-doped CeO2 (111) catalysts. © 2019 Wiley Periodicals, Inc.

Biochemical characterization and kinetic/thermodynamic study of Aspergillus tamarii URM4634 β-fructofuranosidase with transfructosylating activity.

This study reports on the biochemical characterization as well as the kinetic and thermodynamic study of Aspergillus tamarii URM4634 β-fructofuranosidase (FFase) with transfructosylating activity. Conditions for FFase activity were optimized by means of a central composite rotational design using pH and temperature as the independent variables, while residual activity tests carried out in the temperature range of 45-65°C enabled us to investigate FFase thermostability and estimate the kinetic and thermodynamic parameters of enzyme denaturation. Optimal conditions for sucrose hydrolysis and fructosyl transfer catalyzed by crude FFase were 50°C, and pH 6.0 and 7.4, respectively. The thermodynamic properties of irreversible enzyme inactivation were found to be activation energy of 293.1 kJ mol-1 , and activation enthalpy, entropy, and Gibbs free energy in the ranges 290.3-290.4 kJ mol-1 , 568.7-571.0 J mol-1 K-1 , and 97.9-108.8 kJ mol-1 , respectively. The results obtained in this study point out satisfactory enzyme activity and thermostability at temperatures commonly used for industrial fructo-oligosaccharide (FOS) synthesis; therefore, this novel FFase appears to be a promising biocatalyst with great potential for long-term FOS synthesis and invert sugar production. To the best of our knowledge, this is the first report on kinetic and thermodynamic parameters of an A. tamarii FFase.

Thermodynamic analysis of precipitation behavior of M23C6 carbide in Nimonic 105 superalloy

AbstractThe Time–Temperature–Precipitation diagram ofM23C6carbide formation was established for a Nimonic 105 Ni-based superalloy by means of microstructural observation and mathematical-thermodynamic analysis. The results showed that during heat treatment at 750 °C,M23C6carbide usually forms at grain boundaries due to the decomposition ofMC carbides, indicating that the grain boundaries promoteM23C6carbide precipitation. Also, by increasing temperature or time, diffusion rate increases and new diffusional paths (such as γ matrix and twinning) are provided leading to the nucleation of these phases inside the matrix by means of γ→M23C6+ γ′ reaction. According to thermodynamic analysis, the interactions betweenM23C6formation Gibbs free energy and diffusion activation energy of elements, especially carbon, definesM23C6precipitation behavior. The peak of the Time–Temperature–Precipitation diagram was calculated to be about 900 °C based on experimental results, and about 927 °C based on thermodynamic results. These two temperatures can be considered as approximately equal.

Experimental and theoretical study on the regioselective synthesis and reaction of some bis- and poly(3-mercapto-1,2,4-triazin-5(4H)-one) derivatives

The synthetic utility of 3-thioxo-1,2,4-triazin-5-ones 1 and 4-amino-3-mercapto-1,2,4-triazin-5(4H)-ones 2 as building blocks for novel bis- and poly(1,2,4-triazines) via alkylation with the corresponding bis- and poly(halo) compounds was investigated. Prediction of the site of alkylation has been confirmed using spectroscopic data. Theoretical calculation using hybrid density functional method wb97xd and 6-311++g(d,p) as basis set was implemented to investigate the reaction products energetics parameters. The atomic charges were calculated and discussed in details using three different methods. The transition state search were implemented to estimate the Gibbs free activation energy barrier of the reaction to emphasis the experimental results.

On the behaviour of molecular interactions of ionic liquids with organic solvent from T = (298.15 to 323.15) K at 0.1 MPa

ABSTRACT Density, speed of sound and viscosity values are measured for different binary mixture concentrations of ([Bmim][NTf2] + aniline) and ([Bmim][Pf6] + aniline) systems at temperatures from T = (298.15 to 323.15) K. VTF equation is used to fit the experimental viscosity values. The excess values of – molar volume, isentropic compressibility, molar Gibbs free energy of activation and speed of sound have been calculated. R-K equation is utilised to evaluate coefficients and standard deviations. The assumptions on the behaviour of molecular interactions from the analysis of excess parameters are supported by the spectroscopic studies.

Kinetic and thermodynamic studies of oil palm mesocarp fiber cellulose conversion to levulinic acid and upgrading to ethyl levulinate via indium trichloride-ionic liquids

This study investigated the kinetic and thermodynamic studies of oil palm mesocarp fiber cellulose conversion to levulinic acid and upgrading to ethyl levulinate via an eco-friendly Bronsted-Lewis acidic ionic liquid, that is, indium trichloride-1-methylimidazolium hydrogen sulfate (InCl3-[HMIM][HSO4]). The conversion reactions, i.e. cellulose depolymerisation to levulinic acid, and the subsequent upgrading esterification to ethyl levulinate, were conducted at a temperature range of 135–175 °C and 65–105 °C, respectively. Pseudo-homogeneous kinetic models were adapted to evaluate the best reaction order. The results indicate that both reactions followed the pseudo-homogeneous first-order kinetic models. Relative low activation energies of 56.5 kJ mol−1 and 28.1 kJ mol−1 were obtained for the cellulose depolymerisation, and the subsequent upgrading esterification, respectively, implying a higher energy and catalytic efficiency system. The first-order rate constants were calculated to analyse the thermodynamic activation parameters. The Gibbs free energy of activation for the cellulose depolymerisation, and the subsequent upgrading esterification were +115.5 kJ mol−1 and +90.3 kJ mol−1 respectively, which were relatively lower than the previous works that used various type of catalysts. These kinetic and thermodynamic parameters provide insights to the oil palm mesocarp fiber cellulose conversion to levulinic acid and ethyl levulinate via the proposed eco-friendly ionic liquids.

Structural and Mechanistic Studies of γ-Fe2O3 Nanoparticle as Hydroxyurea Drug Nanocarrier

In this study, the noncovalent interactions and four mechanisms of covalent functionalization of hydroxyurea have been examined using the density functional theory. Quantum molecular descriptors were also studied in noncovalent interactions. Hydroxyurea is an anticancer drug that, when loaded onto the γ-Fe 2 O 3 nanoparticles, will have additional properties and efficacy in the medical applications. The Lumo-Homo energy gap of hydroxyurea is greater than that of noncovalent configurations, indicating the high reactivity of hydroxyurea. Hydroxyurea can bond to the γ-Fe 2 O 3 nanoparticles through various functional groups such as the CO (k 1 mechanism), the NH 2 (k 2 mechanism), the OH (k 3 mechanism) and the NH (k 4 mechanism). These reactions were considered to calculate the activation energies, the activation enthalpies and the activation Gibbs free energies. Using these calculations, the product of k 4 mechanism was found to be a thermodynamic and kinetic product. These results can be applied to other similar medications. DOI: http://dx.doi.org/10.17807/orbital.v11i3.1367

NMR spectroscopic and theoretical studies on the isomerism of 1,5-benzodiazepin-2-one derivatives containing a perfluorinated side chain

The isomerism of 1,5-benzodiazepin-2-ones 3 containing a perfluorinated side chain was investigated by 1H-, 13C-, 15N- and 19F NMR spectroscopy in different solvents. Compounds 3 exist in CDCl3, (D6)acetone, CD3CN and (D5)pyridine solution as one species, whereas in (D6)DMSO and (D7)DMF partial (E/Z) isomerisation about the exocyclic C2=C3 bond occurs resulting in two isomers. Gibbs free energies (ΔG) and Free activation energies (ΔG≠) were calculated based on BP86 and BP86-SCRF DFT computations.

One-step preparation of reduced graphene oxide/Prussian blue/polypyrrole aerogel and their enhanced photo-Fenton performance

Abstract In this manuscript, hierarchical porous reduced graphene oxide/Prussian blue/polypyrrole (rGO/PB/PPy) aerogel with a surface area of 70 m2/g was prepared and used as a photo-Fenton catalyst. In aerogel, rGO nanosheet acted as skeleton, PPy as cross-linker and PB nanoparticle as active site. The influence of experimental parameters, including H2O2 dosage, rhodamine B (RhB) concentration, catalyst amount, and pH value, on degradation efficiency was investigated. The optimal condition was: 10 mg of catalyst, 10 mg/L of RhB, 100 µL of H2O2, and 6.18 of pH value. Under this condition, 95.2% of RhB was degraded within 30 min and the rate constant was 7.66 × 10−2 min−1. Activation energy, enthalpy change, entropy change, and Gibbs free energy change (298 K) were calculated to be 35 kJ/mol, 35 kJ/mol, 96.5 J/mol K, and 6.4 kJ/mol, respectively. In cyclic experiments, 91.5% of degradation efficiency was remained after the 4th cycle. Besides RhB, other dyes and antibiotics also could be degraded within 75 min. The inhibitory effect of anions was investigated, and H2PO4− had the most significant influence.

Molecular Interactions in Solutions of 1,1-Bis(4-(2-oxopropoxy)phenyl)cyclohexane on Ultrasonic Velocity, Density, and Viscosimetric Data

The ultrasonic velocity, density, and viscosity are measured at various concentrations 0.1–0.01 mol dm–3 in the solutions of 1,1-bis(4-(2-oxopropoxy)phenyl)cyclohexane (BMAPC) in 1,4-dioxane (DO), ethyl acetate (EA), tetrahydrofuan (THF) at 298–313 K and at atmospheric pressure. Parameters: acoustical impedance, adiabatic compressibility, Rao’s molar sound function, Van der Waals constant, internal pressure, free volume, intermolecular free path length, classical absorption coefficient and viscous relaxation time, Gibbs free energy of activation, enthalpy of activation and entropy of activation were determined. Change of the parameters with T indicated existence of strong molecular interactions in solutions and further supported by positive values of solvation number. Gibbs free energy of activation decrease linearly with increasing C and T in the DO system while it decreases with C and increase with T in EA and THF. Enthalpy and entropy of activation were found to be slightly concentration dependent.

One-step preparation of reduced graphene oxide aerogel loaded with mesoporous copper ferrite nanocubes: A highly efficient catalyst in microwave-assisted Fenton reaction.

Heterogeneous Fenton reaction is an attractive method for degradation of organic pollutants due to its high efficiency and non-selectivity and it also causes no secondary pollution. However, low degradation rate and poor recyclability of the catalysts limit its applications for water purification. To overcome this, herein, copper ferrite/reduced graphene oxide (CF/rGO) aerogel was prepared by a one-step hydrothermal method, as a highly efficient catalyst for the microwave-assisted Fenton reaction (MAFR). Under optimal conditions (500 W of microwave power, 600 μL of H2O2, 15 mg of catalyst, and 30 mg/L of RhB), the degradation efficiency of CF/rGO aerogel at 1.0 min (95.7%) was higher than that of reference samples at 3.0 min. Thermodynamical study showed the activation energy, enthalpy change, entropy change, and Gibbs free energy change were 0.73 kJ/mol, -49.5 kJ/mol, -0.135 kJ/mol·K, and -6.8 kJ/mol, respectively, indicating that MAFR was an endothermic and non-spontaneous process.Radical trapping experiments showed that OH, O2-, and h+ played a combined role in RhB degradation. Besides high catalytic activity, CF/rGO aerogel also displayed good reusability, showing removal efficiency of 87.4% after 5 cycles. The high efficiency, good reusability, and simple process make CF/rGO aerogel a promising catalyst for wastewater treatment.

Conversion of C2–4 Carboxylic Acids to Hydrocarbons on HZSM-5: Effect of Carbon Chain Length

The conversion of C2–4 carboxylic (acetic, propionic, and n-butyric) acids on HZSM-5 was studied at 350 °C. The reaction proceeds through ketonization (to acetone, 3-pentanone, and 4-heptanone, respectively), aldol condensation, and tertiary reactions to aromatics-rich hydrocarbons. The product distribution is influenced by the carbon chain length of carboxylic acids due to the shape selectivity of ZSM-5. The turnover frequency (TOF) of ketonization of carboxylic acids decreases while the TOF of aldol condensation of corresponding ketones increases with increasing carbon chain length. Langmuir–Hinshelwood mechanism analysis shows that the true activation enthalpy of both ketonization and aldol condensation increases with increasing carbon chain length, due to the increased steric hindrance for the formation of a C–C bond. However, the true Gibbs free activation energy increases for ketonization but decreases for aldol condensation with increasing chain length, due to a greater contribution of activation e...

Exploring Hydrogen Evolution Accompanying Nitrogen Reduction on Biomimetic Nitrogenase Analogs: Can Fe-N xH yIntermediates Be Active Under Turnover Conditions?

Nitrogen reduction reaction (N2RR) carried out on biomimetic catalytic systems is considered to be a promising alternative for the traditional Haber-Bosch ammonia synthesis. Unfortunately, the selectivity of the currently known biomimetic catalysts is poor, as they also catalyze the unproductive hydrogen evolution reaction (HER). In the present computational study, we examine the HER activity of early N2RR intermediates in EP3 (E = B, Si) ligated single-site biomimetic iron complexes by calculating and comparing the activation Gibbs free energies of HER and N2RR elementary steps. We find that, in contrast to previous suggestions, early N2RR intermediates are not likely sources of HER under turnover conditions, as the barriers of the competing N2RR steps are significantly lower. Consequently, future research should focus on preventing other potential HER mechanisms, e.g., hydride formation, rather than accelerating the consumption of early N2RR intermediates as proposed earlier to design more efficient biomimetic catalysts.