Study of simultaneous solubility of salts in the ammonium nitrate–ammonium chloride–water system

Ternary eutectic of the NH₄NO₃–NH₄Cl–H₂O system at–23.6°С has been found using a set of theoretical and experimental methods. According to the data of visual-polythermal and differential thermal analyses data, crystallization surface of the system has been plotted at–23.6 to 100°С.     

Electrochemical and ESR-study of the mechanism of organic compound oxidation in the presence of mediators—Radical cations of substituted pyrazin-di-N-oxydes

The mechanism of methanol, ethanol, diethyl ether, triethyl-o-formate, cyclohexanol, and cyclohexane oxidation in the presence of electrochemically generated radical cations of 2,5-dimethyl-, 2,3,5,6-tetramethyl-, 2,3-dimethyl-5,6-cyclohexa-, and 3-phenyl-5,6-cyclohexapyrazin-di-N-oxydes as mediators was studied by cyclic voltammetry, ESR-electrolysis, and gas chromatography. The studies were carried out at glassy-carbon-, Pt-, and Au-electrodes in 0.1 M LiClO₄ solutions in acetonitrile and methanol, the alcohol being used as a solvent and substrate simultaneously. ESR-spectra of the radical cations of the pyrazin-di-N-oxydes were recorded. Effects of temperature, oxygen, admixtures of water and acid, and the nature of substrate and solvent on the shape of the cyclic voltammograms and intensity of the ESR-spectra of the pyrazin-di-N-oxydes are elucidated. By comparing experimental and calculated voltammograms, the rate constants for the interaction between the pyrazin-di-N-oxydes and the substrates C-H-bonds are determined. Mechanism of the ultimate two-electron catalytic oxidation of the organics as a constituent of complexes, formed with the radical cations of the mediators (pyrazin-di-N-oxydes), is suggested.     

Structure and properties of fibroin filaments during their processing in water—salt solutions of calcium chloride

Russian Chemical Bulletin - The results of studying the modification of fibroin threads in water—salt solutions of calcium chloride are presented. A complex of methods, including optical and...     

421 — Electrochemical and enzymic oxidation of biological purines

The electrochemical and enzymic oxidation of uric acid, various N-methylated uric acids and of guanine, 8-oxyguanine and uric acid-9-riboside have been studied. The voltammetric, spectral and kinetic evidence supports the conclusion that the electrochemical and enzymic (peroxidase) reactions proceed by similar, if not identical, chemical mechanisms.     

Liquid—liquid equilibria in water—aliphatic alcohol systems in the presence of sodium chloride

Liquid—liquid equilibria in mixtures of water, propyl or butyl alcohol isomers and sodium chloride have been studied experimentally at 25 °C The solvent behaviour of the various alcohols is discussed. Setschenow constants, calculated from the measured data, are compared with the results of the scaled particle theory.     

Electrochemical oxidation of organosilicon compounds: V. Electrochemical oxidation of α-silyethers. remarkable effect of silicon on oxidation potentials and reaction pathways

Substitution of a silyl group for hydrogen at the α-position of ethers caused a significant decrease in their oxidation potentials. This effect is attributed to an interaction of the carbonsilicon σ-bond with the lone pair of the oxygen atom. The preparative anodic oxidation of α-silylethers proceeded smoothly in methanol and the carbonsilicon bond was selectively cleaved to give the corresponding acetals.     

Phase and extraction equilibria in water–polyethyleneglycol ethers of monoethanolamides of synthetic fatty acid–ammonium chloride systems

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.     

Electrochemical oxidation of conjugated arylolefins to ∝-bromoketals

Conjugated arylolefins electrolyzed in alcohols in the presence ofalkali metal bromides are transformed into α-bromoketals.     

Surface oxidation and water desorption of CdS

The surface oxidation and HP desorption of powder CdS were studied by means of X-ray photoetectron spectroscopy (XPS), quadrupole mass spectrometry (QMS) and in-situ FTIR. The results show that with the changes of surface composition and the elongation of store time of CdS there are four types of H2O thermally desorbed at different temperatures. It has also been found that through high-temperature air treatment for a short time the oxidized surface layer of CdS can prevent O2 and H2O in air from further attacking the inner CdS molecules.     

Vapor—liquid equilibria of the binary mixtures methyl chloride — methanol and dimethyl ether — methyl chloride and of the ternary mixture dimethyl ether — methyl chloride — methanol

Vapor Liquid Equilibria in mixtures of dimethyl ether, methyl chloride and methanol were investigated in a static equilibrium apparatus for temperatures 250 K < T <350 K and pressures up to 1 MPa. Temperature, pressure and the composition of the liquid and the vapor phase were determined.The consistency of the binary experimental data was checked and parameters of several g^E-models were fitted. The binary parameters were used to predict the ternary VLE and the calculated results were compared with the experimental data.     

The reaction of substituted ethylα-bromocinnamates with tetrabutyl ammonium fluoride

The reaction of ethyl α-bromocinnamates with tetrabutyl ammonium fluoride(TBAF) was influenced largely by the position of the substituent at the phenyl ring.While the substrates without an ortho substituent at the phenyl ring were transformed to the corresponding β-fluoro ethyl cinnamates under the reaction conditions,the presence of an ortho substituent only resulted in the formation of ethyl 3-phenylpropiolate derivatives.The reaction of ethyl 2-bromo-3-(4-methoxyphenyl) acrylate also failed to deliver the hydrofluorination product due to the electron-donating effect of the methoxy group.     

Bulk properties and hydration numbers of components of water–salt,water–urea,and water–urea–salt systems

With an increase in the concentration of additives, the hydration numbers of compounds decrease. Thus, in a saturated 54.6% solution, urea loses approximately 3/4 of the initial amount of water, forming an aquacomplex of the composition (NH₂)₂CO?H₂O. In a supersaturated 44% solution, the sodium chloride aquacomplex is dehydrated by 2/3, and in a supersaturated 67% solution, sodium sulfate is dehydrated by 5/6. The density of these solutions is 1.354÷1.360 g/cm³ (44% NaCl) and 1.800÷1.849 g/cm³ (67% Na₂SO₄). In a saturated urea solution, NaNO₃, NaCl, and Na₂SO₄ complexes lose 53÷55% of hydration water. It is shown that the interactions in the binary water–urea system somewhat increase the hydration number of the salts (structural hydration). The hydration water density, a structurally important characteristic, increases in the series of solutions of urea, NaNO₃, NaCl, and Na₂SO₄. In the same series of additives, the excess volume of binary water–urea and water–salt systems becomes more negative.     

Thermal degradation of hydroxypropyl trimethyl ammonium chloride chitosan–Cd complexes

Thermal degradation of hydroxypropyl trimethyl ammonium chloride chitosan–Cd complexes (HTCC–Cd) was investigated by thermogravimetric analysis. The results indicate that the degradation of HTCC–Cd in nitrogen atmosphere was two-step reaction. For the first step of degradation, the initial temperature of mass loss (T ₀), the final temperature of mass loss (T _f), and the temperature of maximum mass loss (T _p) increase linearly with the rising of heating rate (B). T _o = 1.241B + 220.3, T _p = 1.111B + 245.8, and T _f = 1.335B + 358.2. Using different methods, the kinetic parameters of the two steps were investigated. The results show that the activation energies of the first step of degradation obtained using Friedman and Flynn–Wall–Ozawa methods are 1.684 × 10⁵ and 1.646 × 10⁵ J mol^?1, and the corresponding activation energies for the second step are 1.165 × 10⁵ J mol^?1 and 1.373 × 10⁵ kJ mol^?1. The results obtained from Phadnis–Deshpande methods indicate that the two degradation processes are both nucleation and growth process, and follow A₄ mechanism with intergral form g(X) = [?ln(1 ? X)]⁴.     

Synthesis of substituted benzoxazoles by the iron(Ⅲ)-catalyzed aerobic oxidation process

The FeCl3-catalyzed aerobic oxidation process for the synthesis of benzoxazoles,benzothiazole and benzimidazole has been discovered.This method has proved to be effective to a wide range of substrates,and it has been applied for the synthesis of JTP-426467.     

Electrochemical investigation of the permselectivity of a novel positively-charged sol–gel silicate prepared from tetraethyloxysilane and N-octadecyldimethyl[3-(trimethoxysilyl)propyl]ammonium chloride

A positively-charged sol–gel silicate was simply prepared by hydrolyzed and co-polymmerized N-octadecyldimethyl[3-(trimethoxysilyl)propyl]ammonium chloride (C₁₈-TMS) and tetraethyloxysilane (TEOS). The permeation of the prepared silica film was investigated by cyclic voltammetry (CV). The film shows selectivity by charge exclusion, that is, favorably selective permeation of anionic redox probe and rejection of cationic one. Furthermore, the film shows a little higher relative response to inorganic anionic redox probe than its organic counterpart.     

Shift of reaction pathway by added chloride ions in the oxidation of aromatic ketones by dichloroisocyanuric acid—A kinetic study

Role of added chloride ions on the shift of reaction pathway of oxidation of aromatic ketones (acetophenone, desoxybenzoin) by dichloroisocyanuric acid (DCICA) was studied in aqueous acetic acid—perchloric acid medium. Participation of enolic and protonated forms of ketones in the rate determining steps is manifested from zero and first orders with respect to the oxidant in absence and presence of added chloride ions, respectively. Positive and negative effects of acid and dielectric constant on the reaction rate were observed. The observations deduce plausible mechanisms involving (i) rate-determining formation of enol from the conjugate acid of the ketone (SH⁺) in the absence of added chloride ions and (ii) rapid formation of molecular chlorine species from HOCl (hydrolytic species of DCICA) in the presence of added chloride ions, which then interacts with SH⁺ in a rate-determining step prior to the rapid steps of product formation. The order of Arrhenius parameters substantiate the proposed plausible mechanisms based on order of reactants both in presence and absence of added chloride ions.     

Bubble points of hydrogen chloride–water–isopropanol and hydrogen chloride–water–isopropanol–benzene systems and liquid–liquid equilibria of hydrogen chloride–water–benzene and hydrogen chloride–water–isopropanol–benzene systems

Bubble points of the HCl–water–isopropanol and the HCl–water–isopropanol–benzene systems and liquid–liquid equilibria (LLE) of the HCl–water–benzene and the HCl–water– isopropanol–benzene systems were measured at 25–85°C and 30–70°C, respectively. The electrolyte nonrandom two-liquid model proposed by Chen et al. [C.-C. Chen, H.I. Britt, J.F. Boston, L.B. Evans, AIChE J. 28 (1982) 588–596] can satisfactorily correlate bubble points and liquid–liquid equilibria of the present mixed-solvent electrolyte systems over the entire range of temperature and concentrations using only binary adjustable parameters.     

Acid-base and counter ion dependent solid-state assembly of a ferrocene β-aminoalcohol and the corresponding ammonium salt

2-(Ferrocenylmethyl)amino-2-methylpropan-1-ol was synthesized and converted to the respective ammonium bromide ([1H]Br ≡ 2) and dihydrogenphosphate ([1H]H₂PO₄ ≡ 3). The solid-state structures of 1, 2 and the solvated salt 3 · 1/6Et₂O (3a) have been determined by X-ray diffraction. The solid-state assemblies of 1 and 2 are dominated by infinite ladder-like arrays interconnected by hydrogen bonds whereas the solid-state structure of 3a is built up from linear hydrogen-bonded dihydrogenphosphate chains, which are interlinked via hydrogen bonds to the cations [1H]⁺ into a complicated three-dimensional network. Compound 1 and its interactions with Bu₄NBr and Bu₄NH₂PO₄ in solution were further studied by electrochemical methods and NMR titrations.     

Synthesis,growth and characterization of nonlinear optical urea–ammonium chloride crystals

Semi-organic nonlinear optical urea–ammonium chloride (UAC) crystals have been grown from aqueous solution by slow evaporation technique. The lattice parameters of the grown crystals were determined by X-ray diffraction studies. The presence of functional groups was determined using Fourier transform infrared (FTIR) analysis. The thermal analysis studies indicate that the material possess optimum thermal stability. Optical absorption studies show low absorption in the entire visible region and UV cut – off is found to be at 240 nm. The presence of second harmonic generation (SHG) for the grown crystal was confirmed by Kurtz powder technique.