Revelation of Nonideal Properties of the Diffuse Layer Near the Surface of a Charged Electrode

It is shown that the charge dependence of the difference between reciprocal differential capacitances for two La₂(SO₄)₃concentrations at the same charge qreliably reveals that properties of the diffuse layer at |q| of 1 to 2 C/cm²are not ideal. Experimental values of the capacitance of Hg, Tl–Ga, and Cd–Ga electrodes in La₂(SO₄)₃aqueous solutions suggest that this phenomenon is adequately described by the Gonzalez–Sanz theory, which links activity coefficients of ions in the diffuse layer with the average stoichiometric activity coefficient in the electrolyte and the electrode charge.     

A mixed DFT‐MD methodology for the in silico development of drug releasing macrocycles. Calix and thia‐calix[N]arenes as carriers for Bosutinib and Sorafenib

Interaction energies between a family of 36 calix[n]arenes, their corresponding thia‐ analogues, and two commercially available second generation tyrosine kinase III inhibitors—Bosutinib and Sorafenib—were calculated through DFT methods at the B97D/6‐31G(d,p) level of theory, based on Natural Population Analysis, for the in silico development of suitable drug carriers based on the aforementioned macrocycles which can increase their bioavailability and in turn their pharmaceutical efficiency. Molecular Dynamics simulations (production runs: +500 ns) using the General Amber Force Field were also carried out in order to assess the releasing process of these drugs in an explicit aqueous environment. In total, 144 host–guest complexes are examined. According to our results, five‐membered ? SO₃H and i–Pr functionalized‐calixarenes are the best candidates for Sorafenib‐carriers while six‐membered ones ? SO₃H and C₂H₄NH₂ functionalized– are the lead candidates for Bosutinib‐carriers. © 2015 Wiley Periodicals, Inc.     

Activity coefficients of alkyl sulfate and alkylsulfonate ions in aqueous and water-salt premicellar solutions

Potentiometry has been employed to determine the activity coefficients of n-decyl sulfate and n-alkyl(C₅–C₁₀)sulfonate ions in aqueous solutions of their sodium salts containing NaCl or Na₂SO₄ as a background electrolyte. The selectivity factors have been estimated for ion-selective electrodes exhibiting responses to surfactant ions in the presence of inorganic salts. The pattern of the dependences of the activity coefficients of the surfactant anions on the length of their hydrocarbon radicals and the nature of functional groups has been revealed. The results obtained have been compared with the data on long-chain carboxylates.     

The temperature dependences and methods for the functional representation of the rates of proton magnetic relaxation in aqueous solutions of electrolytes

The paper presents the results of temperature dependence measurements for the rate of proton relaxation (1/T ₁) in sea water with salinity 35‰ over the temperature range −22−+120°C at atmospheric pressure and in some salt solutions at two concentrations (0.5 and 1 mol/l). The possibility of approximating the temperature dependences of magnetic relaxation rates by various functions in pure water, sea water, and solutions of salts with various concentrations was studied. The parameters of these dependences and trends of their variations under the influence of salt components are reported. The most well grounded method for the functional representation of the temperature dependences of 1/T ₁ is the use of the sum of exponents with the number of terms depending on solution concentration. This representation takes into account structural changes in solutions as the concentration grows and corresponds to the Frenkel model of the thermal motion of molecules in aqueous solutions of electrolytes. The combined use of the parameters of the temperature dependences of the rate of relaxation represented by various functions can be a mutually augmenting method for studying the dynamic properties of aqueous solutions of electrolytes with low and moderate concentrations.     

Thermodynamic properties of surfactant sodium n-heptyl sulfonate in water and in aqueous solutions of poly(ethylene glycol) at different temperatures

The volumetric, compressibility and electrical conductivity properties of sodium n-heptyl sulfonate (C₇SO₃Na) in pure water and in aqueous poly(ethylene glycol) (PEG) solutions were determined at different temperatures below and above the micellar composition range. At each temperature, the infinite dilution apparent molar volumes of the monomer and micellar state of C₇SO₃Na in aqueous PEG solutions respectively are smaller and larger than those in pure water. However, the values of the infinite dilution apparent molar isentropic compressibility of both monomer and micellar states of C₇SO₃Na in aqueous PEG solutions are larger than those in pure water. Thermodynamic parameters of micellization of investigated surfactant in water and in aqueous solutions of PEG at different temperatures were estimated and it was found that the micelle formation process is endothermic and therefore, this process must be driven by entropy increase. The calculated Gibbs free energies of micellization for aqueous PEG solutions are more negative than those for pure water and become more negative by increasing temperature. The variation of the critical micelle concentration (CMC) of C₇SO₃Na in water and in aqueous PEG solutions with temperature was obtained and a comparison between the CMC of C₇SO₃Na obtained from different thermodynamic properties was also made.     

Isopiestic Measurement of the Osmotic Coefficients of Aqueous {xH 2 SO 4 + (1− x)Fe 2 (SO 4 ) 3 } Solutions at 298.15 and 323.15 K

This study measures the osmotic coefficients of {xH₂SO₄ + (1−x)Fe₂(SO₄)₃}(aq) solutions at 298.15 and 323.15 K that have ionic strengths as great as 19.3 mol,kg⁻¹, using the isopiestic method. Experiments utilized both aqueous NaCl and H₂SO₄ as reference solutions. Equilibrium values of the osmotic coefficient obtained using the two different reference solutions were in satisfactory internal agreement. The solutions follow generally the Zdanovskii empirical linear relationship and yield values of a _w for the Fe₂(SO₄)₃–H₂O binary system at 298.15 K that are in good agreement with recent work and are consistent with other M₂(SO₄)₃–H₂O binary systems.     

Simulating Unstable States during the Coumarin Adsorption on a Mercury Electrode

Dependences of differential capacitance C on potential E of a stationary electrode (hanging mercury drop) in aqueous 0.1 M NaF solutions containing 4.6 × 10^–4 to 3 × 10^–3 M C₉H₆O₂ are obtained using an automatic impedancemeter. At coumarin concentrations below 0.001 M and potential slowly scanned near –1.1 V (SCE) the capacitance is unstable, which results in differently-shaped C vs. E curves in this potential range. The obtained results are attributed to nonequilibrium phase transitions in the adsorption layer, during which the orientation of coumarin molecules at the electrode surface alters. These phenomena are explained semiquantitatively on the basis of a developed theory.     

Dispersity of stratum corneum in the mixed aqueous solutions of binary mixtures between N,N-dimethyldodecylamine oxide and sodium dodecyl sulfate or two terpenes

Solubilization of cholesterol, differential scanning calorimetric (DSC), nuclear magnetic resonance (NMR) and dynamic light scattering (DLS) measurements were performed in order to reveal the dispersion mechanisms of stratum corneum (SC) into each intact corneocytes in the following systems: (1) in the aqueous mixed solutions of sodium dodecyl sulfate (SDS) and N,N-dimethyldodecylamine oxide (C₁₂DMAO); (2) in the aqueous micellar solutions of C₁₂DMAO containing solubilized α-terpineol (α-T); and (3) in the aqueous micellar solutions of C₁₂DMAO containing solubilized limonene. The intercellular lamellar structure of SC was revealed to be disrupted and/or removed in all these solutions. However, considering the micellar sizes and the interaction among molecules in micelle, the dispersion mechanisms in these three systems were different each other. The three dispersion mechanisms of SC were estimated and discussed on the basis of the results of solubilization, DSC, NMR and DLS, respectively.     

Raman spectra of aqueous lithium sulfate and potassium thiocyanate in strong electric fields

The effects of high-voltage pulsed discharge (HVPD) activation on the Raman spectra of saturated aqueous solutions of lithium sulfate (Li₂SO₄/H₂O) in the range of the ν₁(A) totally symmetric vibrations of the SO ₄ ^2? anion and on the spectra of potassium thiocyanate KSCN/H₂O in the region of the ν₁(C≡N) vibrations of the SCN^? anion have been studied. The temperature dependences of the width and frequency of the corresponding spectral lines have been investigated.     

Effect of the solvent on the 13C NMR spectra of pyrimidine nucleosides

The ¹³C NMR spectra of uridine and cytidine in d₆-DMSO, d₇-DMF, d₉-trimethyl phosphate, d₄-methanol, d₅-pyridine, and D₂O were investigated. A linear correlation between the C₁' chemical shifts and the J₁' vicinal spin-spin coupling constants of the protons was established. From the experimental data it may be assumed that the chief reason for the effect of the solvent on the C₁'₂' chemical shift is the different contribution of the effect of the base as a consequence of a change in the conformational equilibrium of the ribose ring. Deviations from the correlation in aqueous solutions and solutions of cytidine in pyridine are observed as a result of a change in the electron density in the base. The effect of the nature of the solvent on the position of the conformational equilibrium of the base relative to the glycoside bond was demonstrated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1550–1552, November, 1980.     

Simultaneous Delamination and Rutile Formation on the Surface of Ti3C2Tx MXene for Copper Adsorption

In this work, we studied the formation of the rutile phase of titanium dioxide (TiO₂) on delaminated MXene (d‐Ti₃C₂T_x) flakes by the reaction of Ti₃C₂T_x with amino acids in water. Three types of amino acids with varied side‐chain polarity were used to delaminate Ti₃C₂T_x. d‐Ti₃C₂T_x flakes formed stable colloidal solutions due to the negative surface charges of chemisorbed amino acids on the d‐Ti₃C₂T_x. Rutile formed on d‐Ti₃C₂T_x at room temperature upon the intercalation of aromatic amino acids and subsequent sonication of the solution, while flakes intercalated with aliphatic amino acids did not oxidize. X‐Ray diffraction (XRD), transmission electron microscopy (TEM) and Raman spectroscopy revealed the nanosize rutile formation on the surface of Ti₃C₂T_x flakes. The XPS results indicated the surface functionalization of histidine on d‐Ti₃C₂T_x flakes. As‐synthesized histidine functionalized rutile TiO₂@d‐Ti₃C₂T_x hybrid was used for adsorption of Cu²⁺ ions from aqueous solution with a maximum uptake of 95 mg g^?1.     

Characterization of Silicate Complexes in Aqueous Sodium Sulfate Solutions by FAB-MS

When the sodium ion (Na⁺) concentration is increased above 0.5 mol-dm⁻³ (M), the concentrations of dissolved silica in aqueous sodium chloride (NaCl) and sodium nitrate (NaNO₃) solutions decrease because of the salting out effect. On the other hand, the concentration of the dissolved silica in aqueous sodium sulfate (Na₂SO₄) solutions increases monotonously as the concentration of Na⁺ is increased above 0.5 M. The purpose of this study is to determine the reasons why the salting-out effect is not observed in Na₂SO₄ solutions. FAB-MS (Fast Atom Bombardment Mass Spectrometry) was used to sample directly the silica species dissolved in aqueous Na₂SO₄, NaCl, and NaNO₃ solutions. In the FAB-MS spectra of these solutions, the peak intensity ratios of the linear tetramer to the cyclic tetramer largely increased for Na⁺ concentrations between (0.1 and 1) M. This shows that some characteristics of the Na₂SO₄ solutions are similar to those of the NaCl and NaNO₃ solutions. In Na₂SO₄ solutions, however, when the concentration of Na⁺ is higher than 1 M, the peak intensity of the dimer is much higher than those of the other silicate complexes. In Na₂SO₄ solutions, the SO₄²⁻ ion undergoes partial hydrolysis to form HSO⁻₄ and OH⁻ is produced. In particular, in the range where the concentration of SO₄²⁻ is high, the pH of the solution increases slightly. This higher pH yields more dimers from the hydrolysis of silicate complexes. This increase in dimer production agrees with the observation that silica dissolves in sodium hydroxide (NaOH) solutions mainly as a dimer when the concentration of NaOH is less than 0.1 M. In Na₂SO₄ solutions at high concentrations, a salting-out effect is not observed for silica. This is due to the increase in the concentration of OH⁻, which accelerates the hydrolysis of silica and results in dimer formation.     

Thermal decomposition of hydrogen peroxide in the presence of sulfuric acid

Hydrogen peroxide (H₂O₂) is popularly employed as a reaction reagent in cleaning processes for the chemical industry and semiconductor plants. By using differential scanning calorimetry (DSC) and vent sizing package 2 (VSP2), this study focused on the thermal decomposition reaction of H₂O₂ mixed with sulfuric acid (H₂SO₄) with low (0.1, 0.5 and 1.0 N), and high concentrations of 96 mass%, respectively. Thermokinetic data, such as exothermic onset temperature (T ₀), heat of decomposition (ΔH _d), pressure rise rate (dP/dt), and self-heating rate (dT/dt), were obtained and assessed by the DSC and VSP2 experiments. From the thermal decomposition reaction on various concentrations of H₂SO₄, the experimental data of T ₀, ΔH, dP/dt, and dT/dt were obtained. Comparisons of the reactivity for H₂O₂ and H₂O₂ mixed with H₂SO₄ (lower and higher concentrations) were evaluated to corroborate the decomposition reaction in these systems.     

Solvation of the Electrolytic Components of Seawater

A new modification of the adiabatic compressibility method of investigating solvation in solutions is presented and applied to the analysis of the following structurally-related characteristics of hydrated complexes of seawater electrolytes (NaCl, KCl, MgCl₂, CaCl₂, Na₂SO₄, MgSO₄) at different concentrations (0.1 to 5.0 mol⋅kg⁻¹) and temperatures (278.15 to 308.15 K): solvation numbers (h) and their dependences on concentration, volumes of stoichiometric mixtures of ions without their hydration shells (V _2h ), compressibilities (β _1h ) and molar volumes of water in their solvation shells (V _1h ), their dependences on concentration and temperature, etc.     

A computational study of the non-covalent bindings in complexes pairing sulfur tetroxide (SO4(C2V)) with the nitrous oxide (NNO)

The computational investigations are carried out on heterodimers containing sulfur tetroxide (SO₄(C_2V)) with the nitrous oxide (NNO) through MP2/cc–pVDZ and MP2/aug–cc–pVTZ//MP2/cc–pVDZ levels. Eight heterodimers are located on the potential energy surface of SO₄(C_2V)–NNO system. Binding energies of heterodimers in the SO₄(C_2V)–NNO system corrected with BSSE and ZPE are in the range of 1.17–7.90 kJ/mol. The calculated results reveal that the individual interaction of NNO terminal nitrogen atom with one of oxygen atoms of OSO ring in the SO₄(C_2V) monomer leads to the formation of the more stable heterodimer of SO₄(C_2V)–NNO system. The atoms in molecules theory were applied to analyze the nature of intermolecular interactions.     

Extraction of mercury from aqueous iodide solutions by trilaurylamine N-oxide and its subsequent determination by atomic absorption spectrometry

A solvent extraction technique using 0.01M solution of trilaurylamine N-oxide in benzene as extractant has been used to concentrate mercury efficiently from water solutions with or without the presence of 0.02M KI in weakly acidic media. In addition to unmodified aqueous solutions, mercury can be extracted quantitatively from aqueous iodide solutions that are up to 1M in HCl, H₂SO₄, and HNO₃ in a single equilibration. Distribution coefficients and separation factors of several elements relative to mercury(II) are reported for media that contain 0.1 M HCl and 0.02M KI. The reagent is superior to aliphatic amines and quaternary amines for the extraction of mercury from aqueous iodide solutions.     

Reversible SO2 Uptake by Tetraalkylammonium Halides: Energetics and Structural Aspects of Adduct Formation Between SO2 and Halide Ions

Contact with SO₂ causes almost immediate dissolution of tetraalkylammonium halides, R₄NX, (R = CH₃ (Me), X = I; R = C₂H₅ (Et), X = Cl, Br, I; R = C₄H₉ (nBu), X = Cl, Br), with the formation of an adduct, [R₄N]⁺[(SO₂)_nX]^– (n = 1–4). Vapor pressure measurements indicate the proclivity for SO₂ uptake follows the order N(CH₃)₄⁺ < N(C₂H₅)₄⁺ < N(C₄H₉)₄⁺. This trend is in accord with the Jenkins–Passmore volume‐based thermodynamic model. Born–Haber cycles, incorporating the lattice energy and gas phase energy terms, are used to evaluate the energetic feasibility of reactions. Density functional theory calculations (B3PW91; 6‐311+G(3df)) have been used to calculate the energetics of (SO₂)_nX^– (X = Cl and Br) anions in the gas phase. The experimental studies show that tetraalkylammonium halides are feasible sorbents for SO₂. In order to correlate the theoretical model, experimental enthalpy, Δ_rH° and entropy, Δ_rS° changes have been determined by the van't Hoff method for the binding of one SO₂ molecule to (C₂H₅)₄NCl, resulting in the liquid adduct (C₂H₅)₄NCl · SO₂. The structure of the analogous 1:1 bromide adduct, (C₂H₅)₄NBr · SO₂, has been determined by single‐crystal X‐ray diffraction (monoclinic, P2₁/c, a = 9.1409(14) Å, b = 12.3790(19) Å, c = 11.3851(17) Å, β = 107.952(2)°, V = 1225.6(3) ų). The structure consists of discrete alkylammonium cations, bromide anions and SO₂ molecules with short contacts between the anion and SO₂ molecules. The (C₂H₅)₄N⁺ cationadopts a transoid conformation with D_2d symmetry, and represents a rare example of a well‐ordered (C₂H₅)₄N⁺ cation in a crystal structure. The Br^– anions and SO₂ molecules forms a chain, (SO₂Br^–)_n, with bifurcated contacts. Non‐bonding electron pairs on the halide anions engage in electrostatic interactions with the sulfur atoms and charge‐transfer interactions with the antibonding S–O orbitals of the bound SO₂ moiety. Raman and ¹⁷O NMR spectra provide compelling evidence for a charge‐transfer interaction between SO₂ molecules and the halide ions.     

Synthesis and characterization of tetramethylammonium trifluorosulfate

[Me₄N]⁺[SO₂F₃]^?, the first example of a [SO₂F₃]^? salt, has been prepared from Me₄NF and SO₂F₂. The colorless, microcrystalline solid was characterized by its infrared and Raman spectra. The trigonal bipyramidal structure of C_2v symmetry of the [SO₂F₃]^? anion is predicted by ab initio calculations. Two oxygen atoms with d(SO)=143.2 pm and one fluorine atom with d(SF)=157.9 pm occupy the equatorial plane. The two fluorine atoms in the axial position with d(SF)=168.5 pm are repulsed by the two oxygen atoms forming a bent axis with ?(F_axSF_ax)=165.2°.     

The Electronic Structure of Mixed Metcars Ti7MC12 (M = Y,Zr, Nb,..., Ag)

The electronic structures of a series of mixed metallocarbohedrenes (metcars) Ti₇MC₁₂formed as a result of replacement of the titanium atom in the Ti₈C₁₂metcar by 4dtransition metal ions (M = Y, Zr, Nb, ..., Ag) are established using the ab initioelectron density functional method in the discrete-variational scheme. The dependences of electronic structure, charge distributions, and chemical bonds in the Ti₇MC₁₂metcars on the cluster symmetry (T _hor T _d) and position of the 4datom in a molecular cage are discussed. The electronic states of 4datoms in molecular titanium carbide (Ti₈C₁₂metcar) are compared with those in crystal titanium carbide (cubic TiC phase with rock salt structure). The effect of doping of the Ti₈C₁₂metcar with 4datoms on its reactivity is studied.     

Aqueous extract of Acacia cyanophylla leaves as environmentally friendly inhibitor for mild steel corrosion in 1 M H2SO4 solution

The efficiency of Acacia cyanophylla leaves extract as an environmentally friendly inhibitor for mild steel in aerated aqueous 1 M H₂SO₄ solution has been investigated by potentiodynamic polarization measurements and electrochemical impedance spectroscopy techniques. Addition of inhibitor decreases the corrosion current whereas the corrosion potential values show slight shifts in positive directions. Inhibition efficiency was found to be about 93% (the maximum value was determined from the polarization curve). Efficiencies obtained from both electrochemical techniques are in good agreement. Adsorption of Acacia cyanophylla leaves extract on mild steel surface in 1 M H₂SO₄ solution obeys Langmuir adsorption isotherm. Polarization curves were also obtained at different temperatures in order to measure changes of corrosion rate. Corrosion current increases and inhibition efficiency decreases with temperature increasing in H₂SO₄ solutions with and without Acacia cyanophylla extract. Corrosion parameters also changed with exposure time. Copyright © 2010 John Wiley & Sons, Ltd.