Stability of 3<Emphasis Type="Italic">d</Emphasis>-element cyclotetraphosphates in water

The hydrolysis kinetics of the anion in 3d-element cyclotetraphosphates is considered. The thermodynamic functions of formation (Δ _f H ⁰, Δ _f G ⁰, and Δ _f ? _at ⁰ ) of the cyclotetraphosphates are calculated using the ion increment method. A linear correlation is established between and log K Δ _f ? _at ⁰ for these compounds.     

Stability of <Emphasis Type="Italic">s</Emphasis>-, <Emphasis Type="Italic">p</Emphasis>-, and <Emphasis Type="Italic">d</Emphasis>-element diphosphates in water

The mean atomic Gibbs energies of formation of (Δ _f ? _at ⁰ ) of s-, p-, and d-element diphosphates have been calculated using ion increments of the Gibbs energy (Δ _f G ⁰). The diphosphate hydrolysis kinetics is considered, and a correlation between the Δ _f ? _at ⁰ values and the hydrolysis rate constants is presented.     

Adsorption equilibrium at the metal-oxide film interface in the oxidation reactions of Ni,Cr, and their alloys

An adsorption thermodynamic model of the oxidation of Ni-Cr alloys is proposed. According to this model, the adsorption of the alloy component with a lower surface energy (Ni) at the alloy-oxide film interface shifts the equilibrium of the solid-phase reaction 3NiO + 2Cr = Cr₂O₃ + 3Ni (1) toward the enrichment of the oxide film in NiO. It was demonstrated that the total Gibbs energy change for reaction (1) can be presented as ΔG _{T, S} = ΔG _T + ΔG _S, where ΔG _T < 0 is the contribution from the Gibbs energy of the thermochemical reaction of oxidation of Ni and Cr atoms and ΔG _S > 0 is the contribution from the surface Gibbs energy of formation of the alloy associated with the replenishment of the surface layer of the alloy during its oxidation. Calculations of ΔG _S are based on the published data on the surface energy of the pure metal ΔG _S ^o and results of authors’ theoretical studies. It was found that the dependence of \({{a_{NiO}^3 } \mathord{\left/ {\vphantom {{a_{NiO}^3 } {a_{Cr_2 O_3 } }}} \right. \kern-\nulldelimiterspace} {a_{Cr_2 O_3 } }}\) on the content of Cr in the alloy determined from calculated equilibrium characteristic of reaction (1) at 1373 K proved to be in satisfactory agreement with the available experimental data on the composition of the oxide film on Ni-Cr alloys. In addition, the values of the potentials of metal-oxide Ni and Cr electrodes in an aqueous solution at 298 K are calculated, which nearly coincide with the published values of the Flade potential for the passivation of these metals.     

Substituted benzotriazoles as inhibitors of copper corrosion in borate buffer solutions

The adsorption of substituted 1,2,3-benzotriazoles (R-BTAs) onto copper is measured via ellipsometry in a pure borate buffer (pH 7.4) and satisfactorily described by Temkin’s isotherm. The adsorption free energy (?ΔG _a ⁰ ) values of these azoles are determined. The (?ΔG _a ⁰ ) values are found to rise as their hydrophobicity, characterized by the logarithm of the partition coefficient of a substituted BTA in a model octanol–water system (logP), grows. The minimum concentration sufficient for the spontaneous passivation of copper (C _min) and a shift in the potential of local copper depassivation with chlorides (E _pt) after an azole is added to the solution (i.e., ΔE = E _pt ⁱⁿ ? E _pt ^backgr characterizing the ability of its adsorption to stabilize passivation) are determined in the same solution containing a corrosion additive (0.01М NaCl) for each azole under study. Both criteria of the passivating properties of azoles (logC _min and ΔE) are shown to correlate linearly with logP, testifying to the role played by surface activity of this family of organic inhibitors in protecting copper in an aqueous solution.     

Surface disordering of classic and superionic crystals: A description in the framework of the stern model

The surface potential (φ_S) in ionic crystals: binary compounds of the type NaCl and superionic oxygen conductors of the type M _{1 ? c} ^IV Me _c ^III O_{2 ? c/2} are calculated with the aid of the Stern model. Effect of the energy of formation of defects, concentration of accessible sites (N _S), and concentration of admixtures on the temperature dependences of φ_S(T) is studied. Instances of high and low potentials are analyzed. It is demonstrated that the surface potential increases proportionally to the difference between the adsorption energies of individual defects, provided the absolute value of |ΔG _i| (ΔG _i < 0) and concentration N _S are sufficiently large. Values of isoelectric temperatures in NaCl crystals doped with admixtures of other valence are calculated. An attempt is undertaken to describe experimental data for silver halides with the aid of the model. Calculations of the surface potential in superionic oxygen conductors show that increasing concentration of surface vacancies is accompanied by segregation of the admixture cations in the surface layer.     

Volatility and crystal lattice energy of palladium(II) chelates

Temperature dependence of saturated vapor pressure has been measured by gas saturation technique for volatile bis-chelates of palladium(II) with such ligands as acetylacetone, hexafluoroacetylacetone, diethyldithiocarbamate, diisopropyldithiophosphate, and also mixed ligand complex with acetylacetone and cyclooctadiene-2,4. Standard thermodynamic parameters of vaporization ΔH _T ⁰ and ΔS _T ⁰ were calculated. Crystal molecular packings and intermolecular interactions were analyzed basing on structural data. Atomatom potential calculation of van der Waals energy E_cryst in crystal lattice was performed and compared to the experimentally obtained values of sublimation enthalpy for the complexes under study.     

Heat capacity and thermodynamic functions of ferrocenemethanol

The heat capacity (C _{p, m}) of ferrocenemethanol (FM) C₅H₅FeC₅H₄CH₂OH have been measured by the low-temperature adiabatic calorimetry method in the range 6–371 K. The triple point temperature, the enthalpy of fusion, and the purity of the substance under consideration have been determined. The ideal gas thermodynamic functions of FM—absolute entropy S _m(g) ⁰ and change in the enthalpy Δ ₀ ^T H _m at 298.15 K—have been derived from the heat capacity data and the known values of the saturation vapor pressure and enthalpy of sublimation. The ideal gas thermodynamic functions C _{p, m} ⁰ and S _m(g) ⁰ and the enthalpy of formation of FM have been calculated by the empirical difference method at T = 298.15 K. The experimental and calculated values of the thermodynamic functions are consistent within error limits, which proves their reliability.     

The thermodynamic properties of 5-vinyltetrazole and poly-5-vinyltetrazole over the temperature range from <Emphasis Type="Italic">T</Emphasis> → 0 to 350 K

The temperature dependences of the heat capacities of 5-vinyltetrazole and poly-5-vinyltetrazole were measured by adiabatic vacuum calorimetry over the temperature range 6-(350–370) K with errors of ～0.2%. The results were used to calculate the thermodynamic functions of the compounds, C _p ^° , H ^°(T) - H ^°(0), S ^°(T), and G ^°(T) - H ^°(0), over the temperature range from T → 0 to 350–370 K. The energy of combustion of 5-vinyltetrazole and poly-5-vinyltetrazole was measured in an isothermic-shell static bomb calorimeter. The standard enthalpies of combustion Δ _c H ^° and thermodynamic characteristics of formation Δ_f H ^°, Δ_f S ^°, and Δ_f G ^° at 298.15 K and p = 0.1 MPa were calculated. The results were used to determine the thermodynamic characteristics of polymerization of 5-vinyltetrazole over the temperature range from T → 0 to 350 K.     

Electrical conductivity and ionic association of lithium and sodium perchlorates in tetrahydrofuran

The total limiting molar electrical conductivities of ions and triads of ions and the association constants of ions with the formation of ion pairs and triads of ions were calculated from the concentration dependences of the electrical conductivity of solutions of lithium and sodium perchlorates in tetrahydrofuran at 278.15–318.15 K with the use of the method specially developed earlier. The experimental total limiting electrical conductivities were used to calculate the limiting molar electrical conductivities and attraction friction factors of separate ions (Li⁺, Na⁺, ClO ₄ ^? , Li₂ClO ₄ ⁺ , Na₂ClO ₄ ⁺ , Li(ClO₄) ₂ ^? , and Na(ClO₄) ₂ ^? ). The constants of ion association into ion pairs were used to calculate the Gibbs energy of non-Coulomb interionic interaction (ΔG*_+?), and the constants of association into triads of ions, to determine the a ₃ distance parameter between the centers of the ion and the dipole of the ion pair. Positive ΔG*_+?), values and deviations of the experimental a ₃ value from the distance parameter calculated theoretically (a ₃ ⁰ ) for the triad of ions (Δa ₃ = a ₃ ? a ₃ ⁰ ) were related to non-Coulomb repulsion in the region of overlap of the solvation shells of ions and the influence of temperature and ion charge density on this repulsion.     

Thermal properties of dimethylgold(III) 8-hydroxyquinolinate and 8-mercaptoquinolinate

Dimethylgold(III) complexes with 8-hydroxyquinoline Me₂Au(Ox) (I) and 8-mercaptoquinoline Me₂Au(Tox) (II) were synthesized and studied. Complex II obtained for the first time was identified from the elemental analysis, IR, ¹H NMR, and mass spectrometry data. The thermal properties of complexes I, II in condensed state were investigated by thermography. The temperature dependences of the saturated vapor pressure over crystals were measured by the Knudsen effusion method with mass spectrometric recording of the gas phase composition and the thermodynamic characteristics of the sublimation process were determined: for I, log P[Torr] = (14.6 ± 0.3) ? (6.34 ± 0.10) × 10³/(T, K), Δ H _subl ^o = 121.2 ± 1.9 kJ^?1, Δ S _subl ^o = 224.1 ± 4.6 J mol^?1 K^?1 (the temperature interval under study 80–115°C); for II, log P [Torr] = (13.3 ± 0.2) ? (6.30 ± 0.09) × 10³/(T, K), Δ H _subl ^o = 120.5 ± 1.7 kJmol^?1, ΔS _subl ^o = 199.3 ± 3.0 J mol^?1 K^?1 (86–145°C).     

Sigmatropic hydrogen shifts in aryltetraphenylcyclopentadienes

Dynamic NMR has revealed intramolecular migrations of hydrogen atom over the periphery of the five-membered ring in 5-(p-tolyl)-1,2,3,4-tetraphenylcyclopentadiene in a deuteronitrobenzene solution with energy barrier ΔG ₁₈₀ ^≠ = 24.8 kcal/mol. Quantum-chemical DFT calculations B3LYP/6-311++G** have shown that such migrations in 1,2,3,4,5-pentaphenylcyclopentadiene in the gas phase occur in a chiral conformation of propeller type by the mechanism of 1,5-sigmatropic hydrogen shifts with retention of configuration through asymmetric transition state with energy barrier ΔE _ZPE ^≠ = 25.9 kcal/mol. Enantiomers P and M can readily interconvert into each other (ΔE _ZPE ^≠ = 3.9 kcal/mol) owing to synchronous flip rotations of the phenyl groups.     

Thermodynamic properties of lanthanum and lanthanide halides: IV. Enthalpies of atomization of LnCl,LnCl<Superscript>+</Superscript>, LnF,LnF<Superscript>+</Superscript>, and LnF<Subscript>2</Subscript>

The results of measurement of equilibrium constants of 30 reactions involving lanthanum and lanthanide fluorides (LnF, LnF₂, and LnF₃) and 14 reactions involving lanthanum and lanthanide monochlorides (Ln = La-Lu) have been summarized. These constants have been used for calculating the enthalpies of reactions by the second and third laws, from which the enthalpies of atomization Δ_at H ₀ ⁰ of LnCl, LnF, and LnF₂ have been determined. Comparison of the calculation results shows that the thermodynamic functions of LnCl and LnF (Ln = Ce-Yb) in which the electronic excitation contribution has been calculated from the excitation energies of Ln⁺ ions allow one to adequately determined the Δ_at H ₀ ⁰ values from experimental data. Using the trends in the change in Δ_at H ₀ ⁰ as a function of the atomic number of a lanthanide, the enthalpies of atomization of compounds for which experimental data are lacking have been estimated. The Δ_at H ₀ ⁰ values for LnCl⁺ ions have been calculated. The reliability of the Δ_at H ₀ ⁰ values for LnF⁺ ions have been assessed.     

Synthesis,structure, physicochemical properties,and solid-phase thermolysis of Co<Subscript>2</Subscript>Sm(Piv)<Subscript>7</Subscript>(2,4-Lut)<Subscript>2</Subscript>

Heterometallic pivalate Co₂Sm(Piv)₇(2,4-Lut)₂ (1) was prepared for the first time and structurally characterized at 293 and 160 K. Antiferromagnetic exchange interactions are dominant in complex 1. This compound experiences a first-order phase transition within 210–260 K. A set of thermodynamic functions was obtained for this complex (C _p , H _T ⁰ - H ₁₈₀ ⁰ , and S _T ⁰ ), and parameters were determined for solid-phase thermolysis where samarium cobaltate SmCoO₃ is the only product.     

Solution Thermodynamics of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis><Superscript>/</Superscript>-Ethylenebis-(salicylideneiminato)-diaquochromium(III) Chloride in Aqueous Dimethylsulphoxide

The densities, viscosities and refractive indices of N,N ^/-ethylene-bis(salicylideneiminato)-diaquochromium(III) chloride, [Cr(salen)(H₂O)₂]Cl, in aqueous dimethylsulfoxide (DMSO) with different mass fractions (w ₂ = 0.20, 0.40, 0.60, 0.80 and 1.00) of DMSO were determined at 298.15, 308.15 and 318.15 K under atmospheric pressure. From measured densities, viscosities and refractive indices the apparent molar volumes (V _φ ), standard partial molar volume (V _φ ⁰ ), the slope (S _V ^* ), standard isobaric partial molar expansibility (φ _E ⁰ ) and its temperature dependence (?φ _E ⁰ /?T) _p , the viscosity B-coefficient, its temperature dependence (?B/?T), solvation number (S _n ) and apparent molar refractivity (R _D ^φ ), etc., were calculated and discussed on the basis of ion–ion and ion–solvent interactions. These results revealed that the solutions are characterized by ion–solvent interactions rather than by ion–ion interactions and the complex behaves as a long range structure maker. Thermodynamics of viscous flow was discussed in terms of transition state theory.     

A comparison of energy changes accompanying growth processes by <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>

Calculations are made using the equations Δ_r G = Δ_r H ? TΔ_r S and Δ_r X = Δ_r H ? Δ_r Q where Δ_r X represents the free energy change when the exchange of absorbed thermal energy with the environment is represented by Δ_r Q. The symbol Q has traditionally represented absorbed heat. However, here it is used specifically to represent the enthalpy listed in tabulations of thermodynamic properties as (H _T  ? H ₀) at T = 298.15 K, the reason being that for a given substance TS equals 2.0 Q for solid substances, with the difference being greater for liquids, and especially gases. Since Δ_r H can be measured, and is tangibly the same no matter what thermodynamics are used to describe a reaction equation, a change in the absorbed heat of a biochemical growth process system as represented by either Δ_r Q or TΔ_r S would be expected to result in a different calculated value for the free energy change. Calculations of changes in thermodynamic properties are made which accompany anabolism; the formation of anabolic, organic by-products; catabolism; metabolism; and their respective non-conservative reactions; for the growth of Saccharomyces cerevisiae using four growth process systems. The result is that there is only about a 1% difference in the average quantity of free energy conserved during growth using either Eq. 1 or 2. This is because although values of TΔ_r S and Δ_r Q can be markedly different when compared to one another, these differences are small when compared to the value for Δ_r G or Δ_r X.     

Thermodynamic parameters of phase transitions of perfluoro-N-(4-methylcyclohexyl)piperidine

The heat capacity of perfluoro-N-(4-methylcyclohexyl)piperidine (PMCP) was measured by low-temperature adiabatic calorimetry. The purity of the substance (N ₁ = 99.66 mol %), triple point temperature (T _tp = 293.26 K), and enthalpy of fusion (Δ_fus H _m ^° = 8.32 kJ/mol) were determined. The enthalpy of vaporization was measured by calorimetry at 298.15 K (Δ_vap H _m ^° (298.15 K) = 56.56 kJ/mol). The temperature dependence of the saturated vapor pressure of PMCP over the pressure range 6.2–101.6 kPa was determined by comparative ebulliometry. The normal boiling point (T _n.b. = 460.74 K), ehthalpies of vaporization (at various temperatures), and critical parameters of PMCP were calculated. The calculated and experimental values of Δ_vap H _m ^° (298.15 K) agree to within measurement errors, which proves the reliability of these values and pT parameters used in calculations.     

A study of the polymerization of ethylene on Ti(III) monocyclopentadienyl compounds by the density functional theory method

Density functional theory was used to study model ethylene reactions with CpTi^IIIEt⁺A^? (A^? = CH₃B(C₆F₅) ₃ ^? , or B(C₆F₅) ₄ ^? ; A^? can be absent) compounds. The polymerization of ethylene on an isolated CpTiEt⁺ cation is hindered because of equilibrium between the CpTi(C₂H₄)Et⁺ primary complex and the primary product of CpTiBu⁺ insertion. At the same time, the polymerization of ethylene on CpTiEt⁺A^? ion pairs (A^? = CH₃B(C₆F₅) ₃ ^? or B(C₆F₅) ₄ ^? ) is thermodynamically allowed (ΔE from ?26.2 to ?25.6 kcal/mol and ΔG ₂₉₈ from ?10.9 to ?10.4 kcal/mol) and is not related to overcoming substantial energy barriers (ΔE ^# = 8.2?12.3 kcal/mol and ΔG ₂₉₈ ^≠ ) = 7.8?13.3 kcal/mol). The degree of polymerization can be low because of the effective occurrence of polymer chain termination by hydrogen transfer from the polymer chain to the monomer.     

Prediction of changes in the heat capacity of the liquid–vapor phase transition based on modified Randič indices. Alkanes and oxygen-containing compounds

The work proposes a method to predict changes in the heat capacity of the liquid—vapor phase transition Δ _l ^g Ср ⁰ (298.2) based on modified Randi? indices for alkanes and acyclic oxygen-containing compounds: alcohols, aldehydes, ketones, ethers, and esters. Based on the obtained Δ _l ^g Ср ⁰ (298.2) values heat capacities in the liquid phase Cp _liq ⁰ (298.2) are calculated for the compounds under study.     

Modelling of proton and metal exchange in the alginate biopolymer

Acid–base behaviour of a commercial sodium alginate extracted from brown seaweed (Macrocystis pyrifera) has been investigated at different ionic strengths (0.1≤I/mol l^?1≤1.0) and in different supporting electrolytes (Et₄NI, NaCl, KCl, LiCl, NaCl+MgCl₂), with the aim of examining the influence of ionic medium on the proton-binding capacity and of quantifying the strength of interaction with light metal ions in the perspective of speciation studies in natural aqueous systems. Potentiometric ([H⁺]-glass electrode) and titration calorimetric data were expressed as a function of the dissociation degree (α) using different models (Henderson–Hasselbalch modified, Högfeldt three parameters and linear equations). The dependence on ionic strength of the protonation constants was taken into account by a modified specific interaction theory model. Differences among different media were explained in terms of the interaction between polyanion and metal cations of the supporting electrolytes. Quantitative information on the proton-binding capacity, together with the stabilities of different species formed, is reported. Protonation thermodynamic parameters, at α=0.5, are log K ^H=3.686±0.005, ΔG ⁰=?21.04±0.03 kJ mol^?1, ΔH ⁰=4.8±0.2 kJ mol^?1 and TΔS ⁰=35.7±0.3 kJ mol^?1, at infinite dilution. Protonation enthalpies indicate that the main contribution to proton binding arises from the entropy term. A strict correlation between ΔG and TΔS was found, TΔS=?9.5–1.73 ΔG. Results are reported in light of building up a chemical complexation model of general validity to explain the binding ability of naturally occurring polycarboxylate polymers and biopolymers. Speciation profiles of alginate in the presence of sodium and magnesium ions, naturally occurring cations in natural waters, are also reported.     

Phase equilibria in the Tl-TlCl-Te system and thermodynamic properties of the compound Tl<Subscript>5</Subscript>Te<Subscript>2</Subscript>Cl

The Tl-Te-Cl system was studied in the Tl-TlCl-Te composition region by differential thermal analysis, X-ray powder diffraction, and emf and microhardness measurements. A series of polythermal sections, an isothermal section at 400 K, and a projection of the liquidus surface of the phase diagram were constructed. The ternary compound Tl₅Te₂Cl characterized by a wide homogeneity region and incongruent melting by a syntectic reaction at 708 K was shown to exist. This compound was found to crystallize in tetragonal lattice (space group I4/mcm) with the parameters a = 8.921 Å, c = 12.692 Å, Z = 4. Wide phase separation regions were also found in the system, including a three-phase separation region in the Tl-TlCl-Tl₂Te subsystem. Regions of primary crystallization of phases, and the types and coordinates of in- and monovariant equilibria in the T-x-y diagram were determined. From emf measurement data, the standard thermodynamic functions of formation and the standard entropy were calculated for the compound Tl₅Te₂Cl, as follows: ?ΔG ₂₉₈ ⁰ = 355.9 ± 1.1 kJ/mol, ?ΔH ₂₉₈ ⁰ = 377.1 ± 5.0 kJ/mol, and S ₂₉₈ ⁰ = 474.1 ± 6.8 J/(mol K).