Solubility diagrams of the potassium iodide-water-N,N-dimethylformamide and iodine-iodide-water-N,N-dimethylformamide systems at 25°C

The solubility diagrams of the potassium iodide-water-N,N-dimethylformamide (DMFA) and iodine-iodide-water-N,N-dimethylformamide systems were studied at 25°C by the method of sections. The systems are characterized by three-phase equilibria of the peritonic and eutonic types, respectively. Potassium iodide in the I₂-KI-/H₂O-DMFA (95: 5 wt %)/ system was found to salt in crystalline iodine. The selected composition of the H₂O-DMFA mixed solvent possessed a higher iodine-solving ability compared with pure mixture components.     

Reaction of 4-amino-4′-methoxydiphenylamine oxidation in surfactant solutions

The kinetics of noncatalytic and catalytic oxidation reactions of 4-amino-4′-methoxydiphenylamine with different oxidants in aqueous solutions and in the presence of surfactants was studied. The catalytic activity of iridium(IV) in this reaction in weakly acidic solutions (pH = 3) was estimated. The dependences of the rates of noncatalytic and catalytic processes on the component concentrations in the reaction mixture, the acidity of solutions, and their temperature were determined. A method for the catalimetric determination of iridium(IV) was proposed and verified against model mixtures.     

Reactions of Fused Carbonyl-containing Spirodihydrofurans with Hydrogen Sulfide and Acids

Reactions were studied of fused spirodihydrofurans originating from 1,3-cyclohexanedione with hydrogen sufide arising in situ. Depending on a substituent at the atom C ³ of the heterocycle the reaction ended by thionation of the conjugated carbonyl group followed by heterocyclization involving the spirodimedonyl fragment. A quantum-chemical forecasting of the protonation stages of substrates and their thionated analogs was performed applying the semiempirical PM3 procedure. A probable mechanism of investigated transformations of the spirodihydrofurans was suggested.     

Investigation into the structural composition of hydroalcoholic solutions as basis for the development of multiple suppression pulse sequences for NMR measurement of alcoholic beverages

An eight‐fold suppression pulse sequence was recently developed to improve sensitivity in ¹H NMR measurements of alcoholic beverages [Magn. Res. Chem. 2011 (49): 734–739]. To ensure that only one combined hydroxyl peak from water and ethanol appears in the spectrum, adjustment to a certain range of ethanol concentrations was required. To explain this observation, the structure of water–ethanol solutions was studied. Hydroalcoholic solutions showed extreme behavior at 25% vol, 46% vol, and 83% vol ethanol according to ¹H NMR experiments. Near‐infrared spectroscopy confirmed the occurrence of four significant compounds (‘individual’ ethanol and water structures as well as two water–ethanol complexes of defined composition – 1 : 1 and 1 : 3). The successful multiple suppression can be achieved for every kind of alcoholic beverage with different alcoholic strengths, when the final ethanol concentration is adjusted to a range between 25% vol and 46% vol (e.g. using dilution or pure ethanol addition). In this optimum region, an individual ethanol peak was not detected, because the ‘individual’ water structure and the 1 : 1 ethanol–water complex predominate. The nature of molecular association in ethanol–water solutions is essential to elucidate NMR method development for measurement of alcoholic beverages. The presented approach can be used to optimize other NMR suppression protocols for binary water–organic solvent mixtures, where hydrogen bonding plays a dominant role. Copyright © 2014 John Wiley & Sons, Ltd.     

A comparative analysis of the solubility diagrams of iodine-water-alkanol ternary systems at 25°C

The solubilities of the components of the iodine-water-propanol (1-C₃H₇OH) ternary system at 25°C and atmospheric pressure were measured for the first time. The solubility diagram of this system is a ternary system diagram with salting out. Iodine stratifies water-propanol mixtures containing 16.2–73.0 wt % alcohol. The solubility of crystalline iodine increases as the content of alcohol in the mixed solvent grows and is maximum in a mixture containing 79.0 wt % alcohol. A comparative analysis of the phase diagrams of the iodine-water-alkanol (ethanol, propanol-1, and propanol-2) systems was performed. The differences between them can likely be explained by an increase in the electron donor ability of the alcohols, which is also in agreement with the enthalpies of solution of the alcohols in water.     

Application of modern chemometric methods to the study of equilibria in solutions

The possibility of the spectrometric-chemometric study of equilibria in solutions is demonstrated for substances with strongly overlapping spectra, in particular, using the independent component analysis (MILCA and SIMPLISMA algorithms) and the alternating least squares algorithm (MCR-ALS). Using the chemometric approach allows one to resolve spectral curves, identify species present in the solution, and calculate the characteristics of equilibria. The proposed approach is illustrated on a series of examples (study of a tautomeric equilibrium and complexation reactions).     

Catalymetric Determination of Rhodium Based on the Reaction of the Oxidation of Triphenylamine-4-Sulfonic Acid by Sodium Periodate

The catalytic activity of rhodium(III) was studied in the reaction of the oxidation of triphenylamine-4-sulfonic acid by sodium periodate at pH 3. The dependence of the reaction rate on the technique of catalyst preparation, the presence of activators, the concentrations of the components, and the acidity and temperature of solutions was revealed. A sensitive and selective method for the catalymetric determination of rhodium(III) is proposed and tested with synthetic mixtures.     

Self-injection length in La0.7Ca0.3MnO3-YBa2Cu3O7-δ ferromagnet-superconductor multilayer thin films

We have carried out extensive studies on the self-injection problem in barrierless heterojunctions between La_0.7Ca_0.3MnO₃ (LCMO) and YBa₂Cu₃O_7-δ (YBCO) thin films. The heterojunctions were formed in situ by sequentially growing LCMO and YBCO films on 〈100〉 LaAlO₃ (LAO) substrate using a pulsed laser deposition (PLD) system. YBCO micro-bridges with 64 μm width were patterned both on the LAO (control) and LCMO side of the substrate. Critical current, I _c, was measured at 77 K on both the control side as well as the LCMO side for different YBCO film thickness. It was observed that while the control side showed a J _c of ∼ 2 × 10⁶ A/cm², the LCMO side showed about half the value for the same thickness (1800 ?). The difference in J _c indicates that a certain thickness of YBCO has become ‘effectively’ normal due to self-injection. From the measurement of J _c at two different thicknesses (1800 ? and 1500 ?) of YBCO films both on the LAO as well as the LCMO side, the value of self-injection length (at 77 K) was estimated to be ∼ 900 ?. To the authors’ best knowledge, this is the first time that self-injection length has been quantified. A control experiment carried out with LaNiO₃ deposited by PLD on YBCO did not show any evidence of self-injection.     

Methodology of chemometric modeling of spectrometric signals in the analysis of complex samples

A generalized algorithm of the multivariate simulation of spectrometric data is considered for solving typical analytical problems, like the determination of the concentration of a particular analyte and the assignment of a sample to one of predefined classes. In particular, we considered preliminary data processing, exploratory analysis, optimization of a chemometric model, calculation of performance characteristics, transfer of the model to other spectrometers, and automation of chemometric processing for the routine analysis of samples. To illustrate the potential of the method, we selected a system of bovine and porcine heparin, mixtures of soy and sunflower lecithin, and a set of red and white wine samples as test samples. Partial least squares and discriminant analysis were used as chemometric methods. We used proton nuclear magnetic resonance (1H NMR) to record signals. Using the MATLAB environment, chemometric programs were developed for automated data processing in the context of problems under consideration and for the transfer of multivariate models to other spectrometers. Based on the results obtained, a methodology is proposed for the multivariate analysis of spectrometric data, which can be used in the analysis of various types of matrices and spectrometric signals.