Esterification of 3-hydroxy-2-naphthoic acid with homologous primary and secondary alkenyl alcohols with different chain lengths in the presence of N,N-carbonyldiimidazole (CDI) and 1,8-diazabicyclo[ 5.4.0]undec-7-ene (DBU) in N,N-dimethylformamide gave the corresponding esters.
The electronic structure and properties of the platinanaphthalenes, and ring-fused B-N platinanaphthalenes isomers have been explored using the hybrid density functional mpw1pw91 theory. The energetic aspect shows that stability of Ptb and Pta isomers are isoenergetic in platinanaphthalenes. On the other hand, BNa1 isomer is the most stable isomer of ring-fused B-N platinanaphthalenes. This is compatible with principles of minimum energy and minimum polarizability in ring-fused B-N platinanaphthalenes. Molecular orbital analysis shows increasing of hardness in ring-fused B-N platinanaphthalenes isomers. Also, electronic spectra analysis indicates that, in all the molecules HOMO-1 → LUMO transition makes the major contribution in most intense electronic transition.
The heat effects of complex formation between copper(II) ions and malonic, maleic, and succinic acids were measured in an isothermic-shell calorimeter at 298.15 K and several ionic strength values against the background of NaNO3. The standard thermodynamic characteristics of complex formation in aqueous solutions were calculated.
In order to propose mechanisms of complicated chemical systems, it is necessary to study simpler subsystems. The mechanism we have proposed for the Bray–Liebhafsky (BL) oscillating reaction is based on kinetic studies of several reactions of iodine compounds between them and with hydrogen peroxide. Because the reactants of the non-catalysed Briggs–Rauscher (BR) oscillating reaction are the same as those of the BL reaction plus malonic acid, we propose now to extend the mechanism of the BL reaction to the BR reaction. With this aim, we add radical reactions of iodine compounds and of malonic acid. The choice of these reactions is based on our recent study of the unusual kinetics of the iodate reduction by high concentrations of hydrogen peroxide.
Four tetraphenylsilane-carbazole derivatives with wide bandgaps (3.38–3.55 eV) were synthesized. The effects of the substitution position and of the presence of naphthalene groups on the photophysical, electrochemical and thermal properties were investigated. The derivatives exhibited maximum absorption peaks ranging from 293 to 304 nm and maximum emission peaks ranging from 347 to 386 nm. Changing the carbazole substitution position on the tetraphenylsilane did not significantly change the photophysical and electrochemical properties. However, p-substituted compounds exhibited higher glass transition temperatures than m-substituted compounds. Naphthalene groups with bulky structures had extended the conjugation lengths that red-shifted both the absorption and emission spectra. The LUMO level was decreased, which reduced the optical bandgap and triplet energy level. However, the naphthalene groups significantly improved the thermal stability by increasing the glass transition temperature of the compounds.
The paper presents the results of experimental studies of thermoelectrochemical systems comprising silver chloride and quinhydrone electrodes in aqueous-methanolic solutions of hydrogen, lithium, potassium, and cesium chlorides. These results and literature data are used to calculate the standard entropies of transfer of electrolytes, Soret thermal diffusion coefficients, and entropies of moving ions at 298.15 K. The influence of the nature of electrolytes and mixed solvent composition on the characteristics of thermal diffusion transfer in the systems studied is discussed.
The thermal oxidative decomposition of benzotriazolyl-substituted phthalocyanines and their copper complexes is investigated by means of thermogravimetric, elemental, and spectroscopic analysis. It is shown that the nature of peripheral substituents exerts the greatest effect on the thermal stability of the compounds.
A theory of deformation polarization is developed. The theory is based on the assumption that the energy of substance polarization in low electric fields virtually equals interaction energy. This approach allowed us to obtain several equations relating deformation characteristics of substance polarization.
The complexation of Ga3+ and In3+ with iminodisuccinic acid (H4L) at 25°C in 0.1, 0.4, 0.6, and 0.8 M KNO3 supporting solutions was studied by potentiometry and mathematical modeling. The thermodynamic constants of formation of neutral, protonated, and hydroxo complexes were calculated by extrapolating the concentration constants to the zero ionic strength using an equation with one individual parameter.
An equation is suggested for describing the kinetics of gas-liquid reactions first order with respect to the dissolved gas without assumptions on the reaction control mode (kinetic, diffusion, etc.). The equation was obtained with the use of the film model of gas-liquid reactions.
The mechanism of the cycloadditional reaction between singlet dichloro-germylidene(R1) and (acetaldehyde(R2) has been investigated with MP2/6-31G* method, including geometry optimization, vibrational analysis and energies for the involved stationary points on the potential energy surface. From the potential energy profile, we predict that the cycloaddition reaction between singlet dichloro-germylidene and acetaldehyde has two competitive dominant reaction pathways. Going with the formation of two side products (INT3 and INT4), simultaneously. The two competitive reactions both consist of two steps: (1) two reactants firstly form a three-membered ring intermediate (INT1) and a twisted four-membered ring intermediate (INT2), respectively, both of which are barrier-free exothermic reactions of 44.5 and 63.0 kJ/mol; (2) then INT1 and INT2 further isomerize to a four-membered ring product (P1) and a chlorine-transfer product (P2) via transitions (TS1 and TS2), respectively, with the barriers of 9.3 and 1.0 kJ/mol; simultaneously, P1 and INT2 react further with acetaldehyde(R2) to give two side products (INT3 and INT4), respectively, which are also barrier-free exothermic reaction of 65.4 and 102.7 kJ/mol.
The dependence of the specific conductance on the solute concentration for a solution of fullerol-d obtained by direct heterogeneous catalytic oxidation of C60 at 25°C is investigated. Values of the molar conductivity and the apparent degree of dissociation and dissociation constant of fullerol-d are calculated. A qualitative charge-transport mechanism for the investigated solutions is proposed.
DOI: 10.1134/S003602441212014X Anahtar Kelimeler:
fullerol, specific conductance, charge transport mechanism
ISSN: 1531-863X Cilt: 86 Sayı: 12 Sayfa: 1808-1815
The simplest isobaric–isothermic phase diagram for a five-component system can be considered a four-dimensional simplex (pentatope) containing 5 vertices, 10 edges, 10 triangular faces, and 5 tetrahedral hyperfaces. Adding one compound formed from r components (2 ≤ r ≤ 5) to the system partitions the simplex into 2–5 filial pentatopes, in which the neighboring pentatopes have a common tetrahedral face. It is proposed that the topology of the system be described using two graphs. The vertices of the graph of a diagram are labeled with the symbols of components and compounds, while its edges indicate which of these phases are in thermodynamic equilibrium. The vertices of the pentatope adjacency graph symbolize pentatopes, and the edge connects two adjacent pentatopes with a common tetrahedral hyperface. Knowledge of the adjacency graph allows enumeration of all elements of the diagram and determination of their relative positions in 4D space. Topological properties characteristic of phase diagrams are considered.
Phase equilibria in layering systems of water, polyethyleneglycol ethers of monoethanolamides of synthetic fatty acids (SFAs) (synthamide-5), and ammonium chloride are studied. The possibility of using such systems for the liquid extraction of metal ions is evaluated. The effect the nature of salting-out agents has on the processes of segregation of the systems has been considered.
The heat effects of complex formation between D,L-threonine and zinc(II) ions at 288.15, 298.15, and 308.15 K and ionic strengths of 0.25, 0.50, and 0.75 were determined calorimetrically against the background of potassium nitrate. The thermochemical results were processed taking step equilibria into account. Along with complex formation, side protolytic processes were considered. The standard heat effects of complex formation in the system studied were determined by extrapolation to zero ionic strength with the use of an equation with one individual parameter. The heats of solution of D,L-threonine in water and aqueous alkali were used to calculate the standard enthalpies of formation of the complexes.
By the conductivity measurements the effects of fructose and temperature (293–308 K) on the micellization of a cationic gemini surfactant (GS), pentanediyl-1,5-bis(dimethylcetylammonium) bromide in aqueous solutions have been investigated. The critical micelle concentration (CMC) of GS was measured at the different temperatures and fructose concentrations. An increasing trend of the CMC values is with addition of fructose. With increasing temperature, the CMC values are in a similar increasing trend. The CMC of GS by dye solubilization method at room temperature have been determined. The standard Gibbs energy, enthalpy and entropy of GS micellization have been evaluated. From these thermodynamic parameters, it was found that in presence of fructose, the stability of the GS aqueous solutions decreases.
A structural description of solutions was performed to find that deviations of the concentration behavior of the density and thermal expansion coefficient of a thermodynamically ideal solution from the mole-additive rule were caused by differences in the microparameters of pure liquids constituting solutions, such as the volume of molecules, packing coefficients, and molecular densities. The contribution of each microparameter to such deviations of the density of solutions of various types was estimated. It was found that, for associated solutions, along with differences in the purely geometric parameters (volume and closeness of packing of molecules), the difference in molecular densities was an influential factor. A method was suggested for distinguishing between the effects of the differences in the structure and energy characteristics of mixed liquids on the behavior of the thermodynamic properties of solutions.
The kinetics of product accumulation is studied in the azodiisobutyronitrile-initiated oxidation of 2-butanol. The relative reactivity for all types of the CH-bonds of 2-butanol is determined for reactions with peroxyl radicals at 60°C. It is established that the hydroxyl functional group of 2-butanol activates the CHbond in position 2 (α) and deactivates CH-bonds in positions 1, 3 (β), and 4 (γ), compared to the corresponding CH-bonds of saturated hydrocarbons.
The method of “quantum mechanics of atoms in molecules” was used to find the parameters of functional groups in isopropylalkanes. The relation between such concepts of the classic theory of the structure of molecules as inductive and steric effects and electron density distribution was shown. Branching could cause deformation of the shape of an atom in a molecule accompanied by changes in volume and energy with charge conservation. The degree of damping of intramolecular steric and inductive effects was substantiated and described. An analysis of transferability of groups and the corresponding parameters was performed to obtain procedures for calculating properties by additive methods.
DOI: 10.1134/S0036024410070174 Anahtar Kelimeler:
Inductive Effect, Steric Effect, Electron Density Distribution, Valence Angle, Isopropyl Group
ISSN: 1531-863X Cilt: 84 Sayı: 7 Sayfa: 1174-1181
The phase relations in the Pr–Mn–O system were studied by the static method at lowered oxygen pressure in combination with thermal analysis and high-temperature X-ray diffraction. The equilibrium oxygen pressure in dissociation of PrMn2O5 and PrMnO3 was measured, and the thermodynamic characteristics of formation of these compounds from elements were calculated. The Р–Т–х phase diagram of the Pr–Mn–O system was constructed in the “composition–oxygen pressure–temperature” coordinates.
Inverse gas-solid chromatography is used to study the adsorption of vapors of organic compounds with different structures and polarities on a carbon adsorbent modified with a monolayer of 4-(3-hydroxypropyloxy)-4′-formylazobenzene (HPOFAB) polar LIQUID crystal. The resulting thermodynamic characteristics of adsorption on the original and modified adsorbents are compared. The effect the nature and structure of adsorbate molecules and the liquid crystal modifier have on the thermodynamic characteristics of adsorption is considered.
A new equation relating the critical amplitudes of thermal oscillations of atoms (the Lindemann factor δ) to the enthalpy of fusion was suggested. According to this equation, δ = 0.13 for solid and 0.28 for liquefied rare gases (helium is not an exception) and 0.15 for metals. The structural and thermodynamic special features of the crystallization of rare gases are discussed.
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
∘(T) - H
∘(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
∘ and thermodynamic characteristics of formation Δf
∘, and Δf
∘ 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.
The sorption of aluminate from alkaline solutions on D-403 anion exchanger is studied. The sorption isotherm is described by the Langmuir and Freindlich classical equations and the Redlich-Peterson generalized equation. Thermodynamic parameters of sorption are determined using the Langmuir equation, modified to describe ion-exchange eqiulibria. A method for determining the type of the sorbed ion in the solid phases is proposed.
Gibbs energies for the transfer of glycylglycine and glycylglycinate ions from water to water-dimethylsulfoxide solvents are determined from the interface distribution of substances between immiscible phases in the composition range of 0.00 to 0.20 molar fractions of DMSO at 298.15 K. It is shown that with a rise in the concentration of nonaqueous components in solution, we observe the solvation of dipeptide and its anion, due mainly to the destabilization of the carboxyl group.
The experimental low-temperature heat capacities of some solid 4f metal trifluorides were used to reveal the trends in the behavior of variable parameters in the equation that described the lattice heat capacity component in the quasi-harmonic approximation for the whole series of LnF3 (Ln = La, … Lu) compounds. The results were used to describe the temperature dependences of heat capacity over the temperature range from 0 K to the melting point T
m. The measured high-temperature enthalpy increments were used to determine corrections to the quasi-harmonic description of heat capacities at T > ∼0.5T
m. The reduced Gibbs energies were calculated over the temperature range 298.15–2000 K. The thermodynamic functions of LnF3 in the gaseous state were determined over the same temperature range in the rigid rotator-harmonic oscillator approximation. All calculations were performed taking into account excited electronic states whose energies did not exceed 10000 cm−1. The reliability of the thermodynamic functions obtained was proved by the convergence of the enthalpies of sublimation calculated by the second and third laws of thermodynamics from the experimental data on saturated vapor pressures. The complete set of the consistent thermodynamic properties of these compounds is described.
Hybrid organic-inorganic ion exchangers are obtained by incorporating amorphous zirconium hydrophosphate into the gel of strong acidic cation exchange resin. Hybrid organic-inorganic ion exchangers are obtained by modifying strong acidic cation exchange resin with amorphous zirconium hydrophosphate. The synthesized materials are studied by standard porometry contact. It is found that raising the inorganic component content to 34 wt % diminishes the microporosity of the samples and simultaneously enhances the of meso- and macropore volume. Experiments establish that modification of a polymer matrix lowers the self-diffusion coefficient of Ni2+ from 8.1 × 10−12 to 2.4 × 10−12–4.1 × 10−12 m2 s−1; nevertheless, an inorganic ion exchanger minimizes the inhibitory effect of co-ions on the Ni2+ → H+ exchange rate. One possible mechanism for of filling of the matrix by with particles of zirconium hydrophosphate is discussed.
The equilibrium geometry of the ground electronic state of PS2 are calculated using B3LYP, B3P86, CCSD(T), and QCISD(T) methods with 6-311G** and cc-pVTZ basis sets. Compared with the experimental values and other available theoretical results, B3P86/cc-pVTZ method can give best energy calculations for PS2 molecule. Based on the principle of atomic and molecular reaction statics, the possible electronic states and their reasonable dissociation limits of PS2 molecule are determined. Then the contour potential lines of PS2 molecule is first derived in many-body expansion method form. The potential curves correctly reproduce the configurations and the dissociation energy for the PS2 molecule.