Phase Diagrams of Fullerenol-d–LaCl3–H2O and Fullerenol-d–GdCl3–H2O Systems at 25°С

Russian Journal of Physical Chemistry A - Isothermal phase diagrams of ternary systems fullerenol-d–LaCl3–H2O and fullerenol-d–GdCl3–H2O at 25°C are studied via...     

Preparation and electrocatalytic performance of Fe–N–C for electroreduction of H2O2

Fe–N–C catalysts were prepared through metal-assisted polymerization method. Effects of carbon treatment, Fe loading, nitrogen source, and calcination temperature on the catalytic performance of the Fe–N–C for H₂O₂ electroreduction were measured by voltammetry and chronoamperometry. The Fe–N–C catalyst shows optimal performance when prepared with pretreated active carbon, 0.2 wt.% Fe, paranitroaniline (4-NA) and one-time calcination. The Fe–N–C catalyst displayed good performance and stability for electroreduction of H₂O₂ in alkaline solution. An Al–H₂O₂ semi-fuel cell was set up with Fe–N–C catalyst as cathode and Al as anode. The cell exhibits an open-circuit voltage of 1.3 V and its power density reached 51.4 mW cm⁻² at 65 mA cm⁻².     

A Thermodynamic Study of 1-Propanol–Glycerol–H2O at 25°C: Effect of Glycerol on Molecular Organization of H2O

The excess chemical potential, partial molar enthalpy, and volume of 1-propanol were determined in ternary mixtures of 1-propanol–glycerol–H₂O at 25°C. The mole fraction dependence of all these thermodynamic functions was used to elucidate the effect of glycerol on the molecular organization of H₂O. The glycerol molecules do not exert a hydrophobic effect on H₂O. Rather, the hydroxyl groups of glycerol, perhaps by forming clusters via its alkyl backbone with hydroxyl groups pointing outward, interact with H₂O so as to reduce the characteristics of liquid H₂O. The global hydrogen bond probability and, hence, the percolation nature of the hydrogen bond network is reduced. In addition, the degree of fluctuation inherent in liquid H₂O is reduced by glycerol perhaps by participating in the hydrogen bond network via OH groups. At infinite dilution, the pair interaction coefficients in enthalpy were evaluated and these data suggest a possibility that the interaction is mediated through H₂O.     

Kinetics of nonisothermal crystallization of Cs2O–Fe2O3–P2O5 glasses

The crystallization kinetics of Cs₂O–Fe₂O₃–P₂O₅ glasses containing 12.5–27 mol% Cs₂O were studied by using differential scanning calorimetry under nonisothermal conditions. Strong dependence of activation energy with temperature was observed, indicating the complex nature of the crystallization process. The various crystallization products were identified by X-ray diffraction technique. CsFeP₂O₇ was found to be the major crystalline phase in all cases. The overall activation energy obtained by classical model-free kinetic method was compared with that of isoconversional method; and from the results, the dependence of activation energy on extent of reaction and average temperature was delineated.     

Interaction parameters and (solid + liquid) equilibria calculation for KCl–H2O–HCl–C2H5OH,K2SO4–H2O–H2SO4 and K2SO4–H2O–C2H5OH mixed solvent-electrolyte systems

This work deals with the prediction and experimental measurements of the (solid + liquid) equilibrium (SLE) in acid medium for industrial purposes. Specific systems including KCl–ethanol–water–HCl and K₂SO₄–water–H₂SO₄ were analyzed. At first, a critical discussion of SLE calculations was given, based on the well-known UNIQUAC extended and LIQUAC models. Two new proposals were derived, considering the explicit necessity of a new reference state for SLE calculations for the studied (solvents + acid) mixtures. The solubility of KCl in water–ethanol–HCl mixed solvents was measured in the temperature range of 300.15 to 315.15 K using an analytical gravimetric method. These results combined with some other experimental data reported in the open literature let us to propose a set of parameters for the new models. They included the interaction parameters between ethanol and the H⁺ ion. The prediction capability of the new models, for calculations in acid medium, was illustrated. Experimentally, it was observed that the (K₂SO₄ + water + H₂SO₄) system presented the unusual behavior of increasing K₂SO₄ solubility with an increase in the sulfuric acid concentration. This was accurately predicted by the newly proposed models.     

Synthesis of sulfonyl chlorides and thiosulfonates from H2O2–TiCl4

A new method is described for the oxidative chlorination of thiols to sulfonyl chlorides using titanium tetrachloride in combination with the oxidant hydrogen peroxide. Direct conversion of thiols into their corresponding thiosulfonates is also reported. Good to excellent yields, short reaction times, high efficiencies, cost-effectiveness, and, facile isolation of the desired products make the present methodology a practical alternative.     

Features of strong O–H⋯O and N–H⋯O hydrogen bond manifestation in vibrational spectra

The work deals with the establishment of the dependence of the vibrational frequencies of strong O–H?O and N–H?O hydrogen bonds for the diagnosing the bonds themselves. To this end, the Raman spectra of a large number of different normal and deutero-substituted crystals characterized by the presence of strong O–H?O and N–H?O bonds are measured and the quantum chemical calculation is performed for one of these compounds. The dependence of the O–H stretching frequency on the O?O distance is constructed differing from that previously known for short O?O contacts. The mechanisms of significant broadening of the O–H vibration band in strong O–H?O hydrogen bonds are considered. Different dependences of the N–H vibrational frequencies in N–H?O bonds are reported and the causes of this diversity are discussed.     

Flow Injection Chemiluminescence Determination of Hemin Using the Rhodamine B–H2O2–NaOH System

A flow injection chemiluminescence method has been developed and applied to the determination of hemin in tablets and animal blood. The proposed method is based on the luminescent properties of the Rhodamine B–H₂O₂–NaOH system and the addition of sodium dodecyl sulfonate (SDS) as emission-sensitizer. Hemin was determined over the concentration range of 8.6×10^–10–8.6×10^–7M with a detection limit of 8.6×10^–11M (3). The relative standard deviation (RSD) for seven independent detections of 1.72×10^–8M hemin was 3.0%. The proposed method was successfully applied to the analysis of hemin in pharmaceutical preparations and animal blood with a recovery of 96–108%. A possible CL mechanism of the present system was discussed, and free radicals were suggested to be involved in this reaction.     

Synchrotron FTIR microscopy of synthetic and natural CO2–H2O fluid inclusions

Fluid inclusions provide a record of the physical and chemical composition of fluids that flow through the Earth's crust. Here, we describe a novel use of synchrotron Fourier Transform Infrared (FTIR) microscopy to map three parameters in individual fluid inclusions: (1) very low concentrations of CO₂, (2) variations of the state of CO₂ and (3) variations in water structure. The intensity of the synchrotron light source allows compositional mapping of individual fluid inclusions, which provides high-resolution images of the distribution of different CO₂ and H₂O species within individual inclusions. High resolution spectra of the CO₂, recorded here for the first time in fluid inclusions, show the rotational lines of CO₂ gas. The results reveal predicted as well as unexpected distributions of CO₂ gas in the inclusions.     

Mechanism of•OH Formation in the thermal decomposition of (≡Si–O)2Si(C2H5)(O–O•) radicals

ESR andIR spectroscopy and quantum chemical calculations are used to obtain the mechanistic data on the reaction . The IR bands are assigned by simulating the vibrational spectra of model low-molecular compounds. Quantum chemical calculations provided the data on the shapes of potential energy surface for the systems under study and transition states. These data are used to interpret the experimental data. The title reaction occurs much more readily in the case of organosilicon peroxy radicals than in the case of their hydrocarbon analogs. Surface silanone groups of silica react with ethylene molecules to form the siloxacyclobutane group.     

Phase diagram studies of methanol–CHF3 and methanol–H2O–CHF3 mixtures

Comprehensive phase diagrams of methanol/CHF₃ and methanol/H₂O/CHF₃ mixtures over the temperature range of 25–100°C and pressure range of atmospheric to 340 atm are reported. Fluoroform is expected to be useful as an alternative to CO₂ for enhancing the fluidity of liquid mixtures due to its high polarity and low viscosity. Therefore, these mixtures will be studied as mobile phases for enhanced-fluidity liquid chromatography and extraction. The phase behavior of methanol/CHF₃ and methanol/H₂O/CHF₃ was compared to that of methanol/CO₂ and methanol/H₂O/CHF₃. Fluoroform is markedly more miscible with methanol or methanol/H₂O than is CO₂. Data for methanol/CHF₃ binary mixtures were also modeled by the Peng–Robinson equation of state. The correlation results showed that the PR equation of state with two temperature-independent binary parameters was capable of representing the experimental data over the entire temperature range with an average relative deviation within 6%.     

Structure of (C3H5NH3)2H2P2O7·H2O

The bis(cyclopropylammonium)dihydrogenodiphosphate monohydrate is a new diphosphate associated with the organic molecule C₃H₅NH₂. We report the chemical preparation and the crystal structure of this organic cation diphosphate. (C₃H₅NH₃)₂H₂P₂O₇.H₂O is orthorhombic (S.G. : P2₁2₁2₁), with Z = 4 and the following unit-cell parameters : a = 4.828(1) Å, b = 11.011(1) Å, c = 25.645(2) Å. The P₂O₇ groups and H₂O water molecules form a succession of bidimensional layers perpendicular to the c axis. The organic cations ensure the three-dimensional cohesion by NH-O hydrogen bonds.     

The effect of mechanical activation on the thermal reactions of P2O5–Al2O3–Fe2O3–Na2O phosphate glasses

The effect of mechanical activation on the structure and thermal reactions of glasses has been studied on the example of Na–Al–Fe phosphate glasses. These glasses are used in nuclear technology for immobilization of radioactive waste. The glasses were activated by grinding in a planetary mill. Mechanical activation causes a decrease of the T _g temperature as well as of the glass crystallization temperature. The type of crystalline phases formed and the quantitative proportions between them are changing. Analysis of inter-atomic interactions in the structure of glass was applied to explain the observed regularities governing the crystallization of the activated glasses.     

Determination of the Activity Coefficients of NaCl in the System NaCl–NH4Cl–H2O

Using ion-selective electrode(s) (ISE) the activity coefficients of NaCl in the system NaCl–NH₄Cl–H₂O at 10, 25, and 40°C were measured by a computer-controlled automatic titration system. The ionic strength fractions of NH₄Cl were 0.2, 0.4, 0.6, and 0.8, respectively. It was found that the influence of the NH₄⁺ cation on the Na glass ISE was small enough to be neglected up to 3.0 mol-kg^-1. The Pitzer equation was adopted to calculate the activity coefficients of NaCl in this system and compared with the experimental data. Comparison of results indicates that the Pitzer parameters correlated from solubility data are suitable for calculating the activity coefficients for this system within the saturated solutions.     

Experimental Study on Phase Equilibria in Na2B4O7–Na2SO4–H2O and Li2B4O7–Na2B4O7–H2O Aqueous Ternary Systems at 273 K

Russian Journal of Physical Chemistry A - The solubility data for ternary systems Na2SO4–Na2B4O7–H2O and Li2B4O7–Na2B4O7–H2O at 273 K were obtained experimentally by the...     

Iodination of B12H11OC(O)CH2–3, B12H11OH2–, and B12H11SCN2–

Reactions of iodination of monosubstituted derivatives of B₁₂H₁₁X^2–anion (X = OC(O)CH₃, OH, SCN) were studied. The reactions were shown to proceed smoothly to give B₁₂H₁₀(OC(O)CH₃)I^2–((carboxy)(iodo)[decahydro[I _h1551-²⁰-closo]dodecaborate(2–)] anion), B₁₂H₁₀(OH)I^2–((hydroxo)(iodo)[decahydro[I _h1551-²⁰-closo]dodecaborate(2–)] anion), and B₁₂H₁₀(SCN)I^2–((thiocyanato)(iodo)[decahydro[I _h1551-²⁰-closo]dodecaborate(2–)] anion) in high yields, irrespective of the solvent used (benzene, H₂O–ROH, where R = C₂H₅, CH₂CH₂CH₃).¹