Comparison of the Results of Atomic Absorption and X-ray Fluorescence Analysis of Metals in Atmospheric Aerosols

Factors responsible for the systematic discrepancies between the results of atomic absorption (standard procedure) and X-ray fluorescence determination of metals in atmospheric aerosols preconcentrated on a filter were studied. Patterns describing the errors in the results of determining Fe, Cu, Pb, Zn, Mn, and Cr by the proposed procedures depending on the type of the metal compound and the concentration of SiO₂ in aerosol particles were found. It was shown that the underestimation of the results of atomic absorption analysis in comparison to those obtained by X-ray fluorescence is due to the incomplete decomposition of some analyte compounds and the adsorption of Fe, Cu, and Pb on the precipitated SiO₂.     

Estimation of the heat capacity of individual substances on the basis of experimental enthalpy increments

A method of determination of the high-temperature (T > 298.15 K) heat capacity function of individual substances by differentiation of enthalpy increment measurements with respect to temperature has been suggested. The approach is based on approximation of enthalpy increment measurements by a polynomial without free term, which makes it possible to strictly meet the boundary conditions of differentiation determined by the properties of the enthalpy increment function. In combination with the Shomate method, the approach enables the optimal choice of the form of temperature dependence of heat capacity that is consistent best of all with the concepts of classical thermodynamics and provides the best reproducibility of enthalpy increment measurements. When low-temperature heat capacity measurements for individual substances are not available, i.e., the Shomate method is inapplicable, the suggested strategy makes it possible to obtain the heat capacity change function in the temperature range of enthalpy increment measurements and to estimate the heat capacity of the substance at standard temperature.     

Synthesis of 1,5-Substituted Pyrrolidin-2-ones from Donor–Acceptor Cyclopropanes and Anilines/Benzylamines

We developed a straightforward synthetic route to pharmacologically important 1,5-substituted pyrrolidin-2-ones from donor–acceptor cyclopropanes bearing an ester group as one of the acceptor substituents. This method includes a Lewis acid-catalyzed opening of the donor–acceptor cyclopropane with primary amines (anilines, benzylamines, etc.) to γ-amino esters, followed by in situ lactamization and dealkoxycarbonylation. The reaction has a broad scope of applicability; a variety of substituted anilines, benzylamines, and other primary amines as well as a wide range of donor–acceptor cyclopropanes bearing (hetero)aromatic or alkenyl donor groups and various acceptor substituents can be involved in this transformation. In this process, donor–acceptor cyclopropanes react as 1,4-C,C-dielectrophiles, and amines react as 1,1-dinucleophiles. The resulting di- and trisubstituted pyrrolidin-2-ones can be also used in subsequent chemistry to obtain various nitrogen-containing polycyclic compounds of interest to medicinal chemistry and pharmacology, such as benz[g]indolizidine derivatives.     

Fluorescent Pyranoindole Congeners: Synthesis and Photophysical Properties of Pyrano[3,2-f], [2,3-g], [2,3-f], and [2,3-e]Indoles

This paper reports the synthesis of four types of annulated pyranoindole congeners: pyrano[3,2-f]indole, pyrano[2,3-g]indole, pyrano[2,3-f]indole, and pyrano[2,3-e]indole and photophysical studies in this series. The synthesis of pyrano[3,2-f], [2,3-g], and [2,3-e]indoles involve a tandem of Bischler–Möhlau reaction of 3-aminophenol with benzoin to form 6-hydroxy- or 4-hydroxyindole followed by Pechmann condensation of these hydroxyindoles with β-ketoesters. Pyrano[2,3-f]indoles were synthesized through the Nenitzescu reaction of p-benzoquinone and ethyl aminocrotonates and subsequent Pechmann condensation of the obtained 5-hydroxyindole derivatives. Among the pyranoindoles studied, the most promising were pyrano[3,2-f] and [2,3-g]indoles. These compounds were characterized by moderate to high quantum yields (30–89%) and a large (9000–15,000 cm⁻¹) Stokes shift. More detailed photophysical studies were carried out for a series of the most promising derivatives of pyrano[3,2-f] and [2,3-g]indoles to demonstrate their positive solvatochromism, and the data collected was analyzed using Lippert-Mataga equation. Quantum chemical calculations were performed to deepen the knowledge of the absorption and emission properties of pyrano[3,2-f] and [2,3-g]indoles as well as to explain their unusual geometries and electronic structures.     

Thermal characterization and sorption of FeIII ion by ternary polylactide–poly-3-hydroxybutyrate–chitosan compositions

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Method of approximation of dependence of isobaric heat capacity on temperature

A method of approximating temperature dependence of heat capacity has been developed on the basis of a power polynomial in variables with different exponents in combination with the Nelder-Mead simplex method. For especially complicated dependences, the method makes it possible to match polynomials at junction points with infinitesimal deviation. The method provides high reproducibility and correct interpolation of empirical and semiempirical data.     

X‐ray fluorescence determination of the manganese valence state and speciation in manganese ores

This work concerns determination of the manganese valence state and speciation by wavelength‐dispersive X‐ray fluorescence analysis. The authors investigated the effect of the manganese valence state and speciation on the intensity of some К‐series lines of the X‐ray emission spectrum for the samples of manganese compounds. The intensities of MnKβ₅ line and MnKβ′ satellite are least influenced by speciation, and they may be used for evaluating the manganese valence state for the samples containing low iron. The intensities of MnKβ″ and MnKβ^x satellites may be employed for assessing the manganese speciation. The results of X‐ray fluorescence determination of the manganese valence state and speciation in the manganese ores of the South Ural deposits agree with the X‐ray diffraction data. The X‐ray fluorescence method is definitely advantageous, because it does not require a complicated process of sample preparation and allows to receive fast information on the manganese valence state and speciation with the purpose to assess the quality of manganese ores. Copyright © 2015 John Wiley & Sons, Ltd.