Free Energy Change For Formation Research Articles

Conductometric investigation of nano MnSO4 association parameters and complex formation with glycylglycine in aqueous and methanol-water mixtures: Thermodynamic parameters and potential applications

This study aimed to investigate the ion pair association values and association parameters of nano MnSO4 in water and methanol-water mixtures (20 % and 40 % methanol by mass percentage) at varying temperatures (298.15, 303.15, 308.15, and 313.15 K) using the conductometric technique. Additionally, the parameters for complex formation between nano MnSO4 and glycylglycine as a ligand were determined. The focus was on elucidating the thermodynamic formation parameters for the nano Mn2+-glycylglycine interaction, with particular emphasis on comparing the 1: 1 and 1: 2 (M: L) complexes to understand the complexation behavior more comprehensively. The results indicated that the complexation process was spontaneous, as evidenced by negative ΔGf (formation free energy change) values, which increased with temperature, highlighting the enhanced spontaneity of the process. The findings provide valuable insights into designing new materials and procedures by enhancing our understanding of the complexation behavior of nano MnSO4 with ligands like glycylglycine, thus contributing to advancements in various applications such as chemical synthesis, medicines, and environmental remediation. By elucidating the thermodynamic aspects of these interactions, the study aimed to provide valuable information that could be utilized in practical applications and further research endeavors.

Tailored electronic structure by sulfur filling oxygen vacancies boosts electrocatalytic nitrogen oxyanions reduction to ammonia

Electrocatalytic reduction of nitrogen oxyanions (NOx−, x = 3 and 2) to ammonia (NH3) under ambient conditions is an alternative to the Haber-Bosch process (HBP). Recent catalysts are vulnerable to low-rate and -selectivity NH3 synthesis due to the multi-step electron–proton transfer process and water as a proton donor, especially in neutral media. Herein, we introduce sulfur species into Co3O4 spinel nanosheets (S-Co3O4) inspired by the bio-nitrogenase of metal-sulfur clusters to alleviate the above dilemma. The S5-Co3O4 exhibits an NH3 yield rate of 174.2 mmol h−1 g−1 at − 0.6 V versus reversible hydrogen electrode (RHE) with a Faradaic efficiency of 89.9 %, nitrate (NO3−) as feedstock. Furthermore, nitrite (NO2−) reduction possesses comparable NH3 Faradaic efficiency (87.6 %) and a higher yield rate (314.5 mmol h−1 g−1) at the same conditions. Theoretical calculations demonstrated that sulfur species reduce the free energy change of formation *H, boosting the activation of *NOx (x = 3 and 2). A two-electrode device, S5-Co3O4 as bifunctional catalysts, demonstrates excellent NH3 Faradaic efficiency (>95 %) over a wide voltage range for NO2−RR, while the anode produces high value-added benzoic acid.

Reaction lumping in metabolic networks for application with thermodynamic metabolic flux analysis

Thermodynamic metabolic flux analysis (TMFA) can narrow down the space of steady-state flux distributions, but requires knowledge of the standard Gibbs free energy for the modelled reactions. The latter are often not available due to unknown Gibbs free energy change of formation , {Delta }_{f} G^{0}, of metabolites. To optimize the usage of data on thermodynamics in constraining a model, reaction lumping has been proposed to eliminate metabolites with unknown {Delta }_{f} G^{0}. However, the lumping procedure has not been formalized nor implemented for systematic identification of lumped reactions. Here, we propose, implement, and test a combined procedure for reaction lumping, applicable to genome-scale metabolic models. It is based on identification of groups of metabolites with unknown {Delta }_{f} G^{0} whose elimination can be conducted independently of the others via: (1) group implementation, aiming to eliminate an entire such group, and, if this is infeasible, (2) a sequential implementation to ensure that a maximal number of metabolites with unknown {Delta }_{f} G^{0} are eliminated. Our comparative analysis with genome-scale metabolic models of Escherichia coli, Bacillus subtilis, and Homo sapiens shows that the combined procedure provides an efficient means for systematic identification of lumped reactions. We also demonstrate that TMFA applied to models with reactions lumped according to the proposed procedure lead to more precise predictions in comparison to the original models. The provided implementation thus ensures the reproducibility of the findings and their application with standard TMFA.

Effect of ultrasonic vibration on the intermetallic compound layer formation in Al/Cu friction stir weld joints

Dissimilar aluminium alloy and pure copper joints were produced using a novel ultrasonic vibration assisted friction stir welding (UVaFSW) assembly. The intermetallic compounds (IMCs) formed at the Al-Cu interfaces were characterized using a scanning electron microscope and energy-dispersive X-ray spectroscopy analysis. The thermodynamic prediction of the first intermetallic compound formation using effective Gibbs free energy change of formation (EGFEF) model was used to calculate the first intermetallic compound layer to nucleate or form during each process condition at the joint interface. The results show that irrespective of the welding conditions (with and without ultrasonic vibrations) intermetallic compounds are formed at the interface. However, the ultrasonic vibration effectively reduced the thickness of the IMC layer at the joint interface and consequently improved the mechanical properties of the joints.

Electrode and Redox Potentials of Molybdenum and Stability of Molybdenum Chloro-Species in Alkali Chloride Melts

Molybdenum electrode and Mo(III)/(IV) redox potentials were measured in fused alkali chlorides. Experiments were performed in individual salts (LiCl, NaCl, KCl, RbCl and CsCl) and in several binary and ternary eutectic or low-melting mixtures between 633 and 1173 K (depending on the melting point of the solvent salt). Formal standard electrode potentials E*Mo/Mo(III) and redox potentials E*Mo(III)/Mo(IV) in respect to Cl−/Cl2 couple and Gibbs free energy change of formation of molybdenum(III) chloride in alkali chloride melts were calculated. Electronic absorption spectra of Mo(III) ions were recorded, and spectroscopic parameters of MoCl63− complex ions determined. High temperature spectroscopy measurements were used to study the stability of Mo(III) chloro-species in fused chlorides and the reaction rates of Mo(III) ions disproportionation were also determined. Diffusion coefficients of molybdenum ions in LiCl-KCl-CsCl and NaCl-CsCl eutectic based melts were determined from the results of electrochemical measurements.

DFT-based inhibitor and promoter selection criteria for pentagonal dodecahedron methane hydrate cage

Density functional theory (DFT)-based simulations have been performed to provide electronic structure property correlation based reasoning for conceptualizing the effect of encapsulated methane molecule on the formation of methane hydrate cages, the role of methanol and ethylene glycol as inhibitor and the role of tetra-hydro-furan (THF) and cyclopentane as promoter of methane hydrate. Geometry optimization of 512 cage, 51262 cage and 51264 cage with and without encapsulated methane and the cluster of 512 cage with ethylene glycol, methanol, cyclopentane have been performed by density functional theory using ωB97X-D/6-31+ +G(d,p) method. Methane hydrate formation inhibition by methanol and ethylene glycol as well as methane hydrate stabilization by cyclopentane and tetrahydrofuran are critically analysed based on the interaction energy, free energy change, dipole moment and infrared frequency calculation. Calculation of free energy change for formation of methane hydrate with/without reagents at various temperature and pressure using optimized structure is reported here. It is observed that hydrogen bond between water molecules of clathrate 512 cages become stronger in the presence of cyclopentane and tetrahydrofuran but weaker/broken in the presence of ethylene glycol and methanol. Simulated results correspond well with experimental findings and can be useful for designing new inhibitor and promoter molecules for gas hydrate formation. DFT studies have been performed to show the effect of some inhibitor and promoter molecules on pentagonal dodecahedron methane hydrate cage (1CH4@512) structures and electronic properties. It illustrates scientifically the role of promoter (e.g., cyclopentane) and inhibitor (e.g., methanol) on stability and formation possibility of (1CH4@512).

ChemInform Abstract: A Review on Mechanochemical Syntheses of Functional Materials

AbstractReview: 35 refs.

Rice Os9BGlu31 Is a Transglucosidase with the Capacity to Equilibrate Phenylpropanoid, Flavonoid, and Phytohormone Glycoconjugates

Glycosylation is an important mechanism of controlling the reactivities and bioactivities of plant secondary metabolites and phytohormones. Rice (Oryza sativa) Os9BGlu31 is a glycoside hydrolase family GH1 transglycosidase that acts to transfer glucose between phenolic acids, phytohormones, and flavonoids. The highest activity was observed with the donors feruloyl-glucose, 4-coumaroyl-glucose, and sinapoyl-glucose, which are known to serve as donors in acyl and glucosyl transfer reactions in the vacuole, where Os9BGlu31 is localized. The free acids of these compounds also served as the best acceptors, suggesting that Os9BGlu31 may equilibrate the levels of phenolic acids and carboxylated phytohormones and their glucoconjugates. The Os9BGlu31 gene is most highly expressed in senescing flag leaf and developing seed and is induced in rice seedlings in response to drought stress and treatment with phytohormones, including abscisic acid, ethephon, methyljasmonate, 2,4-dichlorophenoxyacetic acid, and kinetin. Although site-directed mutagenesis of Os9BGlu31 indicated a function for the putative catalytic acid/base (Glu(169)), catalytic nucleophile residues (Glu(387)), and His(386), the wild type enzyme displays an unusual lack of inhibition by mechanism-based inhibitors of GH1 β-glucosidases that utilize a double displacement retaining mechanism.

A review on mechanochemical syntheses of functional materials

This paper reviews mechanochemical (MC) syntheses of functional materials by means of dry grinding operation without heating. First of all, the authors have shown that the MC reaction is dependent on not only material function such as Gibbs free energy change of formation (ΔG<0) and structure type of the starting samples but also machine function enabling us to storage and accumulate the stress energy to the target materials. Then, they have concentrated the former one that the solid-phase reaction can be achieved by the necessary condition like ΔG<0 as well as the structure of the starting samples. The first example is MC synthesis of perovskite complex oxides, ABO3, where A and B trivalent oxides, respectively. Then, another type of complex ones such as ABO4 from A2B3 and B2O5, where B is pentavalent oxides, were shown. In these reactions, the structure of the starting samples are very important to determine the reaction completion or not. A reaction/non-reaction map has been introduced in this paper, and it is seen from the data that the radius (rA, rB and rO) of the each metal elements in the reaction systems are crucial parameters in the reaction systems. The paper has extended to the synthesis of halides and sulfides conversion, and final example is a doping with non-ferrous metal element into oxide like TiO2, attempting the improvement of its visible light photoreactivity. These information would be helpful to understand and estimate the MC solid-state reaction of the starting materials.

Electrochemical and spectrophotometric study on trivalent neodymium ion in molten binary mixtures of LiCl and alkali earth chlorides

The thermodynamic stability of Nd(III) complexes was studied by electrochemical techniques for molten binary mixtures composed of LiCl and an alkali earth chloride, CaCl 2, SrCl 2, or BaCl 2 at 923 K. The Gibbs free energy change of formation of Nd(III) in the melts was determined. The obtained values showed a good correlation with the polarizing power of solvent cations. The Nd(III) complex was more stable in the melts with low polarizing power. The electronic absorption spectrum of the hypersensitive f– f transition of Nd 3+ was investigated to obtain information about the structural change of the NdCl 6 3 - complex. The estimated oscillator strength of the 4 G 5/2, 2 G 7/2 ← 4 I 9/2 transition and the degree of the energy splitting in electronic energy levels showed different trends upon the polarizing power for each of added alkali earth chloride. This indicates that the coordination environments further from second neighbors could have significant impact on the electronic energy levels of Nd(III) in the mixtures including alkali earth cations.

Thermodynamic measurement of (Al 2O 3 + B 2O 3) system by double Knudsen cell mass spectrometry

Thermodynamic properties of B 2O 3 in the (Al 2O 3 + B 2O 3) binary system were investigated by vapor pressure measurement of B 2O 3 in equilibrium with (Al 2O 3 + B 2O 3) compounds or melts using double Knudsen cell mass spectrometry. The Gibbs free energy change of formation of Al 18B 4O 33 (9Al 2O 3·2B 2O 3) was estimated from the vapor pressure in equilibrium with a mixture of Al 18B 4O 33 and Al 2O 3 at 1573 K to 1673 K. And activities of B 2O 3 in the two-phase region Al 18B 4O 33 and B 2O 3-rich liquid, and (Al 2O 3 + B 2O 3) melts were obtained at 1373 K to 1423 K by vapor pressure measurements.

Mechanism-based Labeling Defines the Free Energy Change for Formation of the Covalent Glycosyl-enzyme Intermediate in a Xyloglucan endo-Transglycosylase

Xyloglucan endo-transglycosylases (XETs) are key enzymes involved in the restructuring of plant cell walls during morphogenesis. As members of glycoside hydrolase family 16 (GH16), XETs are predicted to employ the canonical retaining mechanism of glycosyl transfer involving a covalent glycosyl-enzyme intermediate. Here, we report the accumulation and direct observation of such intermediates of PttXET16-34 from hybrid aspen by electrospray mass spectrometry in combination with synthetic "blocked" substrates, which function as glycosyl donors but are incapable of acting as glycosyl acceptors. Thus, GalGXXXGGG and GalGXXXGXXXG react with the wild-type enzyme to yield relatively stable, kinetically competent, covalent GalG-enzyme and GalGXXXG-enzyme complexes, respectively (Gal=Galbeta(1-->4), G=Glcbeta(1-->4), and X=Xylalpha(1-->6)Glcbeta(1-->4)). Quantitation of ratios of protein and saccharide species at pseudo-equilibrium allowed us to estimate the free energy change (DeltaG(0)) for the formation of the covalent GalGXXXG-enzyme as 6.3-8.5 kJ/mol (1.5-2.0 kcal/mol). The data indicate that the free energy of the beta(1-->4) glucosidic bond in xyloglucans is preserved in the glycosyl-enzyme intermediate and harnessed for religation of the polysaccharide in vivo.

Mycobacterium tuberculosis H37Rv ESAT‐6–CFP‐10 complex formation confers thermodynamic and biochemical stability

The 6-kDa early secretory antigenic target (ESAT-6) and culture filtrate protein-10 (CFP-10), expressed from the region of deletion-1 (RD1) of Mycobacterium tuberculosis H37Rv, are known to play a key role in virulence. In this study, we explored the thermodynamic and biochemical changes associated with the formation of the 1 : 1 heterodimeric complex between ESAT-6 and CFP-10. Using isothermal titration calorimetry (ITC), we precisely determined the association constant and free energy change for formation of the complex to be 2 x 10(7) M(-1) and -9.95 kcal.mol(-1), respectively. Strikingly, the thermal unfolding of the ESAT-6-CFP-10 heterodimeric complex was completely reversible, with a T(m) of 53.4 degrees C and DeltaH of 69 kcal.mol(-1). Mixing of ESAT-6 and CFP-10 at any temperature below the T(m) of the complex led to induction of helical conformation, suggesting molecular recognition between specific segments of unfolded ESAT-6 and CFP-10. Enhanced biochemical stability of the complex was indicated by protection of ESAT-6 and an N-terminal fragment of CFP-10 from proteolysis with trypsin. However, the flexible C-terminal of CFP-10 in the complex, which has been shown to be responsible for binding to macrophages and monocytes, was cleaved by trypsin. In the presence of phospholipid membranes, ESAT-6, but not CFP-10 and the complex, showed an increase in alpha-helical content and enhanced thermal stability. Overall, complex formation resulted in structural changes, enhanced thermodynamic and biochemical stability, and loss of binding to phospholipid membranes. These features of complex formation probably determine the physiological role of ESAT-6, CFP-10 and/or the complex in vivo. The ITC and thermal unfolding approach described in this study can readily be applied to characterization of the 11 other pairs of ESAT-6 family proteins and for screening ESAT-6 and CFP-10 mutants.

A Study of the Effect of Electrolyte on the Swelling and Stability of Poly(N-isopropylacrylamide) Microgel Dispersions

Poly(N-isopropylacrylamide) (poly(NIPAM)) microgel dispersion stability has been investigated in the presence of a range of electrolytes. The stability of the dispersions to flocculation is strongly related to the free energy change of formation in aqueous solution for the anions (ΔGfo) and their position in the lyotropic series. The ability of the anions to induce particle deswelling and flocculation has been investigated using photon correlation spectroscopy and turbidity-wavelength measurements, respectively. Anions with a high charge density (and high negative values for ΔGfo) have the ability to dehydrate the poly(NIPAM) chain and induce flocculation. The ability of cations to induce particle deswelling and flocculation was also investigated. The ability of the cations to induce particle deswelling did not coincide with their values for ΔGfo and their position in the lyotropic series. Time-dependent turbidity measurements of collapsed particles in the presence of NaCl were used to calculate the Hamak...

Effective Sintering Aids for Low-temperature Sintering of AlN Ceramics

A disappearing sintering aid was used to promote densification during the initial and middle stages of sintering and to be removed in gaseous form from the specimens during the final stage of sintering. From thermodynamic consideration such as assessment of Gibbs free energy change of formation of Al2O3 compounds including metal-oxide and evaluation of the vapor pressure of metal-oxide, Li2O is expected to become a disappearing sintering aid for AlN sintering. Doping with Li2O resulted in densification of AlN ceramics with Y2O3 and CaO additives by sintering at a firing temperature of 1600 °C. The amount of Li2O in the specimens decreased by volatilization at temperatures higher than 1300 °C, and its amount was at a level of several ppm after firing at 1600 °C for 6 h. Low-temperature densification of AlN specimens by addition of Li2O also caused the improvement of thermal conductivity and mechanical strength of sintered specimens. Present results indicate that a Li2O addition is effective for AlN sintering. Furthermore, LiYO2 was also used as a new sintering aid instead of Li2O and Y2O3, and the results of thermal conductivity and mechanical strength are shown.

High temperature enthalpies and heat capacities of YbMnO 3 and YMnO 3

Heat capacities of YbMnO 3 and YMnO 3 were measured by differential scanning calorimetry (DSC) from room temperature to 850 K. Enthalpy changes of YbMnO 3 and YMnO 3 were measured by drop calorimeter in the temperature range 573 to 1373 K and heat capacity equations were also estimated. The heat capacity equations were determined by combining the data from both calorimeters and the equations derived for YbMnO 3 from 298 K to 1373 K were Cp,m (J K −1 mol −1)=125.3+11.5×10 −3· T−1.78×10 6· T −2 and for YMnO 3 Cp,m( J K −1 mol −1)=120.8+15.8·10 −3· T−2.41·10 6· T −2. The standard Gibbs free energy changes of formation for YbMnO 3 and YMnO 3 at 298 K were also calculated by using above data. The values were determined to be −1317.6 kJ mol −1 and −1367.1 kJ mol −1, respectively.

Standard free energy change of formation per unit volume: a new parameter for evaluating nucleation and growth of oxides, sulphides, carbides and nitrides

The present paper introduces a thermodynamic parameter, the standard free energy changes of formation of oxide, sulphide, carbide and nitride per unit volume, as a criterion for comparing the formation tendency of these compounds. The diagrams for the standard free energy change of formation of common oxides, sulphides, carbides and nitrides per unit volume vs temperature have been calculated and established based on the available thermodynamic data. It is believed that these diagrams can provide better explanations to some oxidation phenomena including the effects of reactive elements on the selective oxidation of Cr2O3 and Al2O3.

Decomposition behavior of Ln2Mn4/3W2/3O7 (Ln = Eu and Er) in reducing atmosphere and their thermodynamic properties

Decomposition behavior of Ln2Mn4/3W2/3O7 (Ln = Eu and Er) in reducing atmosphere at 1273 K was determined. These compounds decomposed to LnMnO3 and Ln2MnWO7 at PO2 = 10−8.46 atm for Ln = Eu and 10−7.46 atmosphere for Ln = Er, respectively. Decomposition product Eu2MnWO7 decomposed to Eu2MnWO6 at PO2 = 10−15.67 atm, while Er2MnWO7 decomposed to Er2O3, MnO, and W less than 10−17 atm. The standard Gibbs free energy changes of decomposition for Eu2Mn4/3W2/3O7, Eu2MnWO7, and Er2Mn4/3W2/3O7 at 1273 K were determined to be 34.4 kJ · mol−1, 191.9 kJ · mol−1, and 44.8 kJ · mol−1, respectively. The standard Gibbs free energy changes of formation of Er2Mn4/3W2/3O7 and Er2MnWO7 were also determined to be −2429.5 and −2463.2 kJ · mol−1 at 1273 K, respectively.

Studies on oxygen dissociation pressure of LnMnO3 (Ln = rare earth) with the e.m.f. technique

The oxygen dissociation pressure of LnMnO3 (Ln  La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y or Sc) was measured at high temperature (1170–1400 K) by means of e.m.f. using stabilized ZrO2 as a solid electrolyte. Assuming that the decomposition reaction proceeds in a stoichiometric form, a standard Gibbs free energy change of decomposition was determined from the oxygen dissociation pressure. The variation of the free energy change with change in identity of Ln was investigated. It was found that the energy change depends strongly upon both the crystal structure and the ionic radius of Ln3+. The standard Gibbs free energy change of formation for LnMnO3 compounds was obtained from the standard Gibbs free energy change for the decomposition reactions and those for the formation of the decomposition materials.

鉄・クロム硫化物(Fe, Cr)&lt;SUB&gt;1&amp;minus;&amp;delta;&lt;/SUB&gt;Sの高温における非化学量論組成

Deviation from stoichiometric composition of ferrous-sulfide Fe1−δS and solid solution sulfides (Fe, Cr)1−δS containing Cr up to 0.3 cation fraction was measured as functions of sulfide composition ξ, sulfur pressures (1∼10−5 Pa) and temperatures (973∼1173 K) using a thermogravimetric technique.Nonstoichiometry δ increased with increasing Cr content in the (Fe, Cr)1−δS and sulfur pressures, while it decreased with increasing temperature at a constant composition and sulfur pressure. Cation vacancy is a predominant lattice defect in the (Fe, Cr)1−δS sulfide, and from the Libowitz model nonstichiometry δ and sulfur activity aS could be expressed by the following relation:(This article is not displayable. Please see full text pdf.) \ oindentwhere μMeS is a free energy change for formation of a sulfide with stoichiometric composition as well as qVMe and σVMe are the formation and interaction energies of cation vacancies. It was observed that the values of σVMe were positive, ranging from 50 to 70 kJ/mol, independent of sulfide compositions, and the values of qVMe decreased from 56 to 17 kJ/mol with increasing sulfide composition.