Choice of electrolyte composition for liquid-absorption concentration of mercury from air for subsequent inversion-voltammetric determination

An electrolyte composition is suggested for absorption recovery and concentration of mercury from air and its subsequent inversion-voltammetric determination on a gold electrode in a solution of the same composition.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 10, 2004, pp. 1659–1662.Original Russian Text Copyright © 2004 by Ermakov, Averyaskina, Moskvin.     

Regioselectivity of reduction of 1,3-dinitrobenzene with potassium (sodium) tetrahydridoborate and electronic structure of reagents and their complexes

Reaction of 1,3-dinitrobenzene with the tetrahydridoborate ion was studied by means semi-empirical PM3 calculations in the isolated molecule and reactant complex approximations. The deviation of the nitro groups from the benzene ring plane, resulting from their rotation about the C-N bond, changes the reaction pathway from the preferred aromatic ring reduction to nitro group reduction. On this basis an explanation of published data on the effect of the temperature and the polarity of the medium on the regioselectivity of the reaction is offered.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 12, 2004, pp. 2023–2029.Original Russian Text Copyright © 2004 by Ermakov, Atroshchenko, Dubenkov, Markushin, Shakhkeldyan.This revised version was published online in April 2005 with a corrected cover date.     

Model for phase coexistence in phase transitions

We propose a general model for describing the phenomena of phase coexistence in relation to pressure induced phase transformations by means of the T–P distribution in statistical thermodynamics. Using the well‐known B1–B2 transition in NaCl as a prototype, we demonstrate how phase coexistence gives rise to the changes in the bulk modulus and the equation‐of‐state across the transition. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004     

Self-association of N-methyltrifluoromethanesulfonamide in the gas phase and in inert solvents

IR spectroscopy and quantum-chemical calculations (B3LYP/6-31G*) were used to show that N-methyltrifluoromethanesulfonamide in the gas phase and in a low-polarity inert solvent (CCl₄) exists as an equilibrium mixture of monomers and cyclic dimers. In a more polar solvent (CH₂Cl₂), highly polar open-chain dimers are stabilized.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 10, 2004, pp. 1659–1664.Original Russian Text Copyright © 2004 by Chipanina, Sherstyannikova, Turchaninov, Shainyan.This revised version was published online in April 2005 with a corrected cover date.     

Synthesis of Nitroesters Based on Methylol Derivatives of Parabanic and Isocyanuric Acids

Nitroesters synthesis based on methylol derivatives of parabanic and cyanuric acids was performed. The corresponding alloxan nitroxymethyl derivative was unstable.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 2, 2005, pp. 264–265.Original Russian Text Copyright © 2005 by Ermakov, Bulatov, Vinogradov, Tartakovskii.     

Basis Set Orbital Relaxation in Atomic and Molecular Hydrogen Systems

Orbital relaxation (OR) amounts to variation of the orbital exponents in hydrogen molecules and ions relative to the exponents of the isolated atom; it is represented as the sum of the one- and two-center contributions depending on the effective atomic charge and on the presence of other atoms in the molecule. The procedure for isolating the contributions of the exponent includes treatment of the OR of hydrogen in a special set of neutral and charged atoms and molecules with certain multiplicities of their electronic states. Within the framework of the spin-unrestricted Hartree-Fock method, we found and discussed the optimal values of the exponents of the basis orbitals of hydrogen atoms and molecules using the minimal split valence-shell basis set, the basis set that includes the polarization function, and the expanded set of grouped natural orbitals. A simple energy model is suggested for OR. Expressions are derived for evaluating the exponents of the relaxed orbitals in hydrogen-containing systems.Original Russian Text Copyright © 2004 by A. I. Ermakov, A. E. Merkulov, A. A. Svechnikova, and V. V. Belousov__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 6, pp. 973–978, November–December, 2004.     

Relaxation Effect of Basis Orbitals on the Properties of Atomic and Molecular Hydrogen Systems

The effect of orbital relaxation on the properties of atomic and molecular hydrogen systems H, H ₂ ⁺ , H₂, H ₂ ⁻ , and H ₃ ⁺ calculated using the minimal basis set, the split valence shell basis set including the polarization function, and an extended basis set of grouped natural orbitals is considered. Inclusion of orbital relaxation in calculations results in a decreased total energy and more accurate energies of electron affinity. The strongest effect is produced on the calculated characteristics of the anions. The calculated activation energy of the radical reaction of hydrogen elimination. H₂ + H = H + H₂ depends strongly on the degree to which electron correlation is taken into account. Due to inclusion of orbital relaxation, the activation energy also approximates the experimental value, although to a lesser extent. The semiempirical PM3 method fails to adequately describe the transition state of this reaction, but this disadvantage is eliminated by using the exponent of the relaxed orbital of hydrogen.Original Russian Text Copyright © 2004 by A. I. Ermakov, A. E. Merkulov, A. A. Svechnikova, and V. V. Belousov__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 6, pp. 979–985, November–December, 2004.     

New Synthetic Approaches to Functionally Substituted 4,5-Dihydro-1,2,3-oxadiazole 2-Oxides

A practical procedure has been proposed for the synthesis of functionally substituted 4,5-dihydro-1,2,3-oxadiazole 2-oxides on the basis ofsulfamic acid derivatives.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 1, 2005, pp. 121–123.Original Russian Text Copyright © 2005 by Tartakovskii, Ermakov, Strelenko, Vinogradov, Petrov.     

Thermodynamic analysis of the phase separation during the polymerization of a thermoset system into a thermoplastic matrix. II. Prediction of the phase composition and the volume fraction of the dispersed phase

A thermodynamic simulation of the phase‐separation process of an off‐critical blend, based on a thermoplastic matrix with a reactive epoxy system undergoing polycondensation at a constant temperature, was performed. The model considered the composition dependence of the interaction parameter, χ(T,Φ₂) (where T is the temperature and Φ₂ is the volume fraction of polystyrene), along with the polydispersity of both polymers. For every level of conversion, the simulation provided the amount, composition, stoichiometric ratio, and conversion of each phase present. The accuracy of the model was proved by the good agreement between the experimental and predicted glass‐transition temperatures and heat capacity changes at the glass‐transition temperatures for both phases. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1361–1368, 2004     

Infrared spectra and electronic configuration of anionic forms of nickel and cobalt octaethylporphin in the solid phase

On the basis of an investigation of IR spectra, electronic configurations have been established for the monoanions of Ni and Co octaethylporphin and the dianion of Ni octaethylporphin in the solid phase; characteristic features have been revealed in the effects on the IR spectra of metalloporphyrins from occupancy of their vacant and orbitals by additional electrons. It has been shown that interaction of the anions with alkali metal countercations may lead (depending on the electronic configuration of the anion and the type of cation) to activation of bands of composite vibrations in the IR spectrum. It has been found that the monoanions of Ni octaethylporphin are capable of existing in d- and -electronic configurations, depending on the phase state (solution or film) and the crystal modification in the solid phase.Translated from Teoreticheskaya i Éksperimental/naya Khimiya, Vol. 26, No. 5, pp. 573–579, September–October, 1990.The authors wish to thank I. F. Gurinovich for useful discussion of the results obtained in this work.     

Effect of high electric fields on the isotropic phase of a lyotropic liquid‐crystalline system

The effect of high (>1000 V/mm) electric fields on solutions of a lyotropic liquid‐crystalline polymer, poly(n‐hexyl isocyanate) in p‐xylene, is presented. The concentrations are adjusted such that the solutions are strictly within the isotropic phase domain region, thus exhibiting no spontaneous liquid crystallinity. The effects of field strength, frequency, and concentration are varied and the morphological changes are noted. The results are analyzed with birefringence measurements via comparison with the optical Kerr effect. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4116–4125, 2004     

Arylation of furan derivatives via the Meerwein reaction

Meerwein arylation of 2-arylfurans and 2-furylnitroethylene gave 2,5-diarylfurans and 5-aryl-2-furylnitroethylenes. Meerwein arylation of 2-acylfurans gives 2,5-diarylfurans and substituted azobenzenes in addition to 2-acyl-5-arylfurans.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 452–456, April, 1975.The authors thank N. P. Solov'eva, O. S. Anisimova, and A. I. Ermakov for recording the PMR and mass spectra and for the interest they displayed with respect to the present research.     

NMR and X-ray diffraction studies of the influence of adsorbed molecule nature on phase transitions in a ZSM-5 silicalite

Pulsed NMR and X-ray diffraction analysis are employed to study the influence of adsorbed toluene, p-xylene, acetone, and di(ethylene glycol) (DEG) molecules on phase transitions in a ZSM-5 silicalite. In the region of phase transitions, times T₁ and T₂ of longitudinal and transverse magnetic relaxation of apolar molecules adsorbed in silicalite micropores increase and decrease in a jumpwise manner, respectively, with a rise in the total content of the liquid. Such changes in T₁ and T₂ occur for hexane, decane, toluene, and p-xylene molecules. Qualitatively different concentration dependences of T₁ and T₂ are observed for polar acetone and DEG molecules, because these liquids do not cause a earrangement in the crystal lattice of silicalite; this is confirmed by the X-ray diffraction data.Translated from Kolloidnyi Zhurnal, Vol. 66, No. 6, 2004, pp. 802–806.Original Russian Text Copyright © 2004 by Pimenov, Skirda, Maksimenko, Morozov, Opanasyuk.     

Variation of the parameters of inhibited oxidation of polyethylene in the region of phase transition

Parameters of oxidation of polyethylene with molecular oxygen in the presence of a phenolic antioxidant, 2,2-methylenebis(4-methyl-6-methylcyclohexylphenol), at 80–210°C were studied. The possible mechanism of interaction of the polymer with the antioxidant near the melting point was considered theoretically. The suggested theoretical relationships are consistent with experimental data.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 8, 2004, pp. 1378–1381.Original Russian Text Copyright © 2004 by Shlyapnikov, Kolesnikova.     

Shear banding in strained semicrystalline polyamide 6 films as revealed by atomic force microscopy: Role of the amorphous phase

Atomic force microscopy (AFM) has been used to visualize the plastic deformation mechanisms that are responsible for the yielding of semicrystalline polymers of low degree of crystallinity (<50%). Indeed, AFM, if operated in suitable conditions, is able to image both the amorphous and the crystalline phases. Polyamide 6 films have been drawn at temperatures T < 160 °C. Postmortem AFM observations show that, at yield, shear bands nucleate and propagate in the amorphous phase. They cross the crystalline lamellae and run over the whole surface of the sample. By crossing the lamellae, they form nanoblocks of uniform size. Neither the size of the nanoblocks nor the angle between the tensile axis and the shear bands can be explained in terms of crystal plasticity. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 687–701, 2004     

Microencapsulation of cholesteryl alkanoate by polymerization‐induced phase separation and its association with drugs

A new microencapsulation technique is presented in which cholesteryl nonanoate (CN)/poly(methyl methacrylate) (PMMA) microcapsules are produced by the induction of phase separation between CN and PMMA within the droplets during the polymerization. The concentration of CN is the most important factor determining the final morphology of the microcapsules. For example, a polynuclear type is obtained at a low concentration (<20 wt %), a mononuclear type is obtained at a medium concentration (20–30 wt %), and an irregular phase is obtained at a high concentration (>40 wt %). To evaluate the effectiveness of the technique for stabilizing an unstable drug, we selected retinol (vitamin A) as a model drug and loaded it into the CN/PMMA microcapsules. We used a process called solute codiffusion, in which a fine solvent emulsion containing the retinol was diffused uniformly into the CN/PMMA microcapsules. The loading efficiency of retinol was predicted successfully with the aid of a thermodynamic equation. In the thermal stability test of retinol, we found that an effective association with the CN phase was the most important factor determining the limit of its molecular stability. The technique reported in this article has great potential for the microencapsulation of soft materials via a simple process and for the stabilization of unstable drugs. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2202–2213, 2004     

Transformation of phase size distribution into scattering intensity

A practical method of calculating the small-angle scattering intensity and the density correlation function from the phase size distribution is presented for a sample with a random two-phase morphology. The correlation function can be calculated in terms of joint probability distribution functions of the phase size distributions of the two individual phases with information from the chord length distribution. The phase size distribution is approximated as a weighted sum of exponentials, which is then transformed analytically into the correlation function and hence the small-angle scattering for any combination of phase size distributions of the two phases. This represents an extension of the Debye method for materials with more complex phase size distributions. The inverse problem of calculating the phase size distributions from the small-angle scattering requires a thermodynamic model or simplifying approximation. An example of the reverse transformation is given for a nanoporous polymer thin film. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3070–3080, 2004     

Dielectric study of the phase diagram of the poly(γ‐benzyl‐L‐glutamate)/dimethylformamide system

The phase diagram for solutions of poly(γ‐benzyl‐L ‐glutamate) in dimethylformamide has been investigated over the entire composition and temperature ranges with dielectric spectroscopy. The dielectric response in this system is dominated by ionic mobility, and phase transitions have been detected as changes in the ionic conductivity. The phase boundaries, determined by dielectric spectroscopy, are consistent with earlier published results obtained by a combination of optical microscopy observations and nuclear magnetic resonance and differential scanning calorimetry studies. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3943–3952, 2004     

Conformational changes and phase transformation mechanisms in PVDF solution‐cast films

The supramolecular crystal structure in poly(vinylidene fluoride) (PVDF) solution‐cast films is studied through changing crystallization conditions in two solvents of different structures and polarities. The crystalline‐state chain conformations of isothermally solution‐crystallized PVDF in N, N‐dimethylacetamide (DMAc), and cyclohexanone are studied through the specific FTIR absorption bands of α, β, and γ phase crystals. There are no changes in the FTIR spectra of cyclohexanone solution‐crystallized films in the temperature range of 50–120 °C. In the case of DMAc solution‐crystallized films, low temperature crystallization mainly results in formation of trans states (β and γ phases), whereas at higher temperatures gauche states become more populated (α phase). This is due to the variations in solvent polarity and ability to induce a specific conformation in PVDF chains, through the changes in chain coil dimensions. This indicates that in spite of cyclohexanone solutions, the intermolecular interactions between PVDF and DMAc are temperature‐sensitive and more important in stabilizing conformations of PVDF in crystalline phase than temperature dependence of PVDF chain end‐to‐end distance <r²>. The high‐resolution ¹⁹F NMR spectroscopy also showed little displacement in PVDF characteristic chemical shifts probably due to changes in PVDF chain conformation resulting from temperature variations. Upon uniaxial stretching of the prepared films under certain conditions, contribution of trans state becomes more prominent, especially for the originally higher α phase‐containing films. Due to formation of some kink bands during film stretching and phase transformation, α phase absorption bands are still present in infrared spectra. Besides, uniaxial stretching greatly enhances piezoelectric properties of the films, maybe due to formation of oriented β phase crystals, which are of more uniform distribution of dipole moments. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3487–3495, 2004     

Influence of the chain length of K-soaps on the phase diagram and structural parameters of nonaqueous liquid crystals and the gel phase in K-soap/glycerol binary systems

 Analogously to the aqueous K-soap/water systems already examined, the five glycerol · (Gl)-containing systems KC _n /Gl (n = 12, 14, 16, 18, 22) also built up hexagonal (H_α), lamellar (L_α), isotropic micellar (S), gel-like (G) and crystalline phases (C). These phases were identified by texture observations with a polarizing microscope, by differential scanning calorimetry measurements and by X-ray diffraction investigations. The appertaining phase regions were plotted in the binary phase diagram. Binary Gl-containing K-soap systems have the following properties. The H_α phase is built up at low soap concentration. The L_α phase is formed at high soap concentrations. The temperature of the phase transition H_α ⇆ S runs through a maximum. Increasing the chain lengths of the soaps shifts the formation of the H_α phase to lower soap concentration. A strong correlation between the chain length of K-soaps and the d values of L_α, H_α, G and C phases is found. Based on the comparison of the X-ray diffractograms of the G phase a structural model is proposed. The G phase consists of two groups of domains with two different dimensions. Received: 9 August 1999/Accepted in revised form: 20 September 1999