New 1,3,5-triphenyl-2-pyrazoline-containing 3-hydroxychromones as highly solvatofluorochromic ratiometric polarity probes

Two novel 1,3,5-triphenyl-2-pyrazoline moiety containing derivatives of 3-hydroxychromone were synthesized and studied by ¹H NMR, absorption and fluorescence spectroscopy. The prospects of practical application of these compounds exhibiting high solvatofluorochromism into analytical chemistry and biophysics as effective ratiometric polarity probes were discussed proceeding from the data on their fluorescent properties.     

Structure of premixed flames of propylene oxide: Molecular beam mass spectrometric study and numerical simulation

The knowledge of the combustion chemistry of oxygenated fuels is essential for the development of detailed kinetic mechanisms suitable for the combustion processes involving biofuels. Moreover, epoxidized olefins, are increasingly used as chemical intermediates or as bulk chemicals. Nevertheless, a dearth of data for their reactivity in the oxidative environment can be observed in the current literature. This study reports the experimental and the model characterization of the flame structure of propylene oxide at stoichiometric and fuel-rich conditions at atmospheric pressure. To this aim, the species mole fractions in three premixed flames stabilized on a flat-flame burner have been quantitatively measured by using the flame sampling molecular beam mass spectrometry. Three chemical kinetic mechanisms retrieved from the current literature involving propylene oxide chemistry have been validated against the novel experimental data. In general, the predictions appeared to be in satisfactory agreement with measurements except for acetaldehyde and ketene. The rate of production analysis in the flame has shown that the discrepancies observed for these species are related basically to the incorrect ratio between the rates of primary reaction pathways of propylene oxide destruction.     

Magnesium Hexafluoridozirconates MgZrF6·5H2O,MgZrF6·2H2O,and MgZrF6: Structures,Phase Transitions,and Internal Mobility of Water Molecules

The MgZrF₆ · n H₂O (n = 5, 2 and 0) compounds were studied by the methods of X‐ray diffraction and ¹⁹F, MAS ¹⁹F, and ¹H NMR spectroscopy. At room temperature, the compound MgZrF₆ · 5H₂O has a monoclinic C‐centered unit cell and is composed of isolated chains of edge‐sharing ZrF₈ dodecahedra reinforced with MgF₂(H₂O)₄ octahedra and uncoordinated H₂O molecules and characterized by a disordered system of hydrogen bonds. In the temperature range 259 to 255 K, a reversible monoclinic ? two‐domain triclinic phase transition is observed. The phase transition is accompanied with ordering of hydrogen atoms positions and the system of hydrogen bonds. The structure of MgZrF₆ · 2H₂O comprises a three‐dimensional framework consisting of chains of edge‐sharing ZrF₈ dodecahedra linked to each other through MgF₄(H₂O)₂ octahedra. The compound MgZrF₆ belongs to the NaSbF₆ type and is built from regular ZrF₆ and MgF₆ octahedra linked into a three‐dimensional framework through linear Zr–F–Mg bridges. The peaks in ¹⁹F MAS spectra were attributed to the fluorine structural positions. The motions of structural water molecules were studied by variable‐temperature ¹H NMR spectroscopy.     

Acid-catalyzed intramolecular cyclization of N-(4,4-diethoxybutyl)sulfonamides as a novel approach to the 1-sulfonyl-2-arylpyrrolidines

Herein we report our studies on the acid-catalyzed cyclisation of N-(4,4-diethoxybutyl)sulfonamides at the presence of polyatomic phenols as an efficient one-pot approach to the synthesis of 1-sulfonyl-2-arylpyrrolidines from the acyclic precursors.     

Structural Inhomogeneity in Electrolyte Solutions: The Calcium Perchlorate–Water System

A new approach has been proposed to study the structure of aqueous electrolyte solutions. NIR, Raman and attenuated total reflectance, Fourier transform infra-red (ATR FTIR) spectra have been measured for aqueous calcium perchlorate solutions in the 0.22–4.3 mol·L^?1 (0.22–7.46 mol·kg^?1) concentration range at 25 °C. By the methods of principal component analysis (PCA) and multivariate curve resolution—alternating least squares (MCR-ALS) the number, spectra and concentration profiles have been determined for spectroscopically distinguishable forms of water and ClO ₄ ^? ion in solutions. The results have been analyzed using a phenomenological model, establishing thereby: concentration ranges for structural rearrangements of the solution, the nature of structural microirregularities and different states of the ClO ₄ ^? ion in the areas of domination of the natural water structure, and of cybotactic groups of calcium perchlorate hexa and tetra hydrates.