Complex formation of Al2(SO4)3 in water-formamide mixtures

The kinetics of formation of AlSO ₄ ⁺ has been investigated in mixtures of water and formamide. In contrast to similar measurements with BeSO₄, the substitution of solvating formamide molecules by the sulfate ion cannot be observed on the aluminum cation. On the other hand, with Al³⁺ cations three well separated water substitution processes are observed, as compared to a single one only with Be²⁺. An explanation for this behavior and for the different pH dependence of the sulfate complex formation for Al³⁺ and Be²⁺ cations is suggested.     

Charge transfer and curve crossings in the [BeH2O]2+ system

Summary Diabatic and adiabatic potential energy curves have been determined for the complexation of beryllium cation with a water molecule, by means of multi-reference perturbation CI. The quasi-diabatic states correspond to Be²⁺H₂O and to nine charge transfer states (Be⁺H₂O⁺): at short beryllium-water distances the ground state is essentially Be²⁺H₂O, but at large distances several charge transfer states have lower energies. The nature of the curve crossings of the ground and lowest excited states in the [BeH₂O]²⁺ system is clarified. The changes brought about by the presence of a second water molecule are investigated.     

Understanding the Localization of Berylliosis: Interaction of Be2+ with Carbohydrates and Related Biomimetic Ligands

The interplay of metal ions with polysaccharides is important for the immune recognition in the lung. Due to the localization of beryllium associated diseases to the lung, it is likely that beryllium carbohydrate complexes play a vital role for the development of berylliosis. Herein, we present a detailed study on the interaction of Be²⁺ ions with fructose and glucose as well as simpler biomimetic ligands, which emulate binding motives of saccharides. Through NMR and IR spectroscopy as well as single-crystal X-ray diffraction, complemented by competition reactions we were able to determine a distinctive trend in the binding affinity of these ligands. This suggests that under physiological conditions beryllium ions are only bound irreversibly in glycoproteins or polysaccharides if a quasi ideal tetrahedral environment and κ⁴-coordination is provided by the respective biomolecule. Furthermore, Lewis acid induced conversions of the ligands and an extreme increase in the Brønstedt acidity of the present OH-groups imply that upon enclosure of Be²⁺, alterations may be induced by the metal ion in glycoproteins or polysaccharides. In addition the frequent formation of Be-O-heterocycles indicates that multinuclear beryllium compounds might be the actual trigger of berylliosis. This investigation on beryllium coordination chemistry was supplemented by binding studies of selected biomimetic ligands with Al³⁺, Zn²⁺, Mg²⁺, and Li⁺, which revealed that none of these beryllium related ions was tetrahedrally coordinated under the give conditions. Therefore, studies on the metabolization of beryllium compounds cannot be performed with other hard cations as a substitute for the hazardous Be²⁺.     

Mass transport and effective diffusion coefficient in the reduction of hydrogen ions from aqueous sulfuric acid solutions: Numerical modeling

This work presents results of the numerical solution to a system of equations of material balance and the movement of particles in solution under the influence of the forces of diffusion, migration, and convection, which describe the process of mass transport during the reduction of hydrogen ions at a rotating disk electrode from aqueous sulfuric acid solutions with and without excess supporting electrolyte. Results of the calculations show that the diffusion kinetics of hydrogen ion reduction can be observed only with measurements in dilute (≤10^?3 M) sulfuric acid solutions with an excess of indifferent supporting electrolyte. For more acidic solutions it is necessary to take into account the simultaneous diffusion of hydrogen and bisulfate ions. In the study of the regularities of hydrogen ion reduction in sulfuric acid solutions with a sulfate supporting electrolyte, it is necessary to take into account that with excess supporting electrolyte, the limiting current of hydrogen reduction is caused solely by the diffusion of bisulfate ions, but for small concentration ratios of the supporting electrolyte to acid, the influence of migration effects is significant.     

Diffusion of ionic species labeled with35S in various aqueous electrolyte solutions at 25°C

Composite diffusion coeffcients have been measured for the various species labeled with³⁵S which are present in a number of aqueous solutions due to the introduction of the labeled material as³⁵SO ₄ ^2– . The solutions were of two components consisting of water and either sodium sulfate. The diffusion coeffcient measured for sodium chloride solutions is similar to literature data for the corresponding diffusion in sodium sulfate solutions. The results for sulfuric acid and ammonium hydrogen sulfate have been interpreted using literature data for the relative concentrations of the hydrogen sulfate and sulfate ions to obtain estimates for the diffusion coefficents of those ions. The results for perchloric acid, regarded as representing the diffusion coefficient of the hydrogen sulfate ion, have a much different concentration dependence to that observed for the estimates for that ion in sulfuric acid and ammonuim hydrogen sulfate. The difference is attributed to the effect of the perchlorate ion on the water structure.     

Kinetic study of the equilibrium in the methanesulfonic acid-water system

A kinetic study of the hydrolysis of ethyl isovalerate in the methanesulfonic acid-water system from pure water to 60.5% CH₃SO₃H at 25°C showed that the hydrolysis rate is directly proportional to the concentration of H₅O₂ ⁺ ions determined by IR spectroscopy. The hydrolysis mechanism is the same as in hydrochloric acid and sulfuric acid solutions. Evidence was found for correctness of the measurements of the equilibrium concentrations of molecules and ions in aqueous methanesulfonic acid solutions by multiple frustrated total internal reflection IR spectroscopy. The possibility was demonstrated for an independent measurement of the equilibrium concentrations of H₅O₂ ⁺ ions by a kinetic method in aqueous acid solutions.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1694–1697, July, 1991.     

Hydrogen bond strength in some beryllium salts,BeXO4·4H2O and Me2Be(XO4)2·2H2O (X = S,Se; Me = K,Rb): Correlation of structural data and infrared spectra

Infrared spectra of the title compounds are presented and discussed in the regions of the uncoupled O–D stretches of matrix-isolated HDO molecules (isotopically dilute samples). The strengths of the hydrogen bonds are analyzed in terms of the respective O_w?O bond distances, the Be–OH₂ interactions (synergetic effect), the proton acceptor capabilities of the sulfate and selenate oxygen atoms as deduced from Brown's bond valence sums of the oxygen atoms, the anti-cooperative effect (proton acceptor and proton donor competitive effect). The infrared spectroscopic experiments reveal that comparatively strong hydrogen bonds are formed in the compounds under study, analogical to other hydrated beryllium salts owing to the large ionic potential of the small Be²⁺ ions. The wavenumbers of ν_OD show that the water molecules in BeSO₄·4H₂O and in the double salts are strongly energetically distorted, i.e. their local symmetries deviate remarkably from the C_2v molecular symmetry (for example, Δν have values of 74 and 36 cm^?1 for H₂O(1) and H₂O(2) in K₂Be(SO₄)₂·2H₂O, and 119 cm^?1 in BeSO₄·4H₂O). The hydrogen bonds in K₂Be(SeO₄)₂·2H₂O are stronger than those in K₂Be(SO₄)₂·2H₂O due to the stronger proton acceptor capability of the SeO₄^2? ions. The proton donor strengths of the water molecules in K₂Be(SO₄)₂·2H₂O and K₂Be(SeO₄)₂·2H₂O are greater than those of the water molecules in BeSO₄·4H₂O and BeSeO₄·4H₂O (i.e. larger deviations from Mikenda's curve) due to the different compositions of the respective beryllium tetrahedra-Be(XO₄)₂(H₂O)₂ in the double salts and Be(H₂O)₄ in the simple ones (proton donor competitive effect). The intramolecular O–H bond lengths are derived from the ν_OD vs. r_OH correlation curve [H.D. Lutz, C. Jung, J. Mol. Struct. 404 (1997) 63].     

The oxidation of organic substances by compounds of trivalent manganese: XIV. Oxidation of malonic acid by manganese(III) sulfate in sulfuric acid medium and with hexaquomanganese(III) ions in noncomplexing perchloric acid medium

The oxidation of malonic acid by manganese(III) sulfate in a medium of sulfuric acid and by hexaquomanganese(III) ions in a noncomplexing perchloric acid medium was studied.The reaction stoichiometry was found and the effect of the concentrations of H⁺, Mn²⁺, and HSO₄^? ions and of the initial reactant concentrations on the course and rate of the reaction was studied.The optimum conditions have been found for analytical use of the reaction, procedures have been proposed for the determination of malonic acid using the two reagents, and the accuracy and reproducibility of the determinations have been found.     

Study on fluorescence and DNA-binding of praseodymium(III) complex containing 2,2'-bipyridine

Bentonite samples collected from vicinity of Petrovac and Aleksinac were treated with different sulfuric acid molarities. Acid attack dissolved the octahedral sheets by interlayer and edge attack. The effects of the H₂SO₄ acid caused an exchange of Al³⁺, Fe³⁺ and Mg²⁺ with H⁺ ions leading to a modification of the smectite crystalline structure. The Mg and Fe substitution in the octahedral sheets promoted the dispersion of corresponding layers and formation of amorphous silicon. The activated bentonites, after the treatment of sulfuric acid, exhibited a lower cation-exchange capacity (CEC) and significant increase of specific surface area from 6 to 387 m² g⁻¹ (bentonite from Petrovac) and from 11 to 306 m² g⁻¹ (bentonite from Aleksinac). The acid reaction caused a splitting of particles within the octahedral sheet which led to an increase in specific surface area and decrease in CEC in both bentonites.     

A DFT Study on the Selective Extraction of Metallic Ions by 12-Crown-4

In order to predict the extraction ability of 12-crown-4 for different metallic ions, the complexes [M(12-crown-4)] and [M(H₂O)₄] (where M=Li⁺, Na⁺, K⁺, Be²⁺, Mg²⁺, Ca²⁺, Cu²⁺ and Zn²⁺) were investigated by the density functional theory without restrictions for their geometry. The metal binding capability was evaluated using the binding energy, and the effect of nature of the metal on the binding properties was also studied. The results of the calculations showed that the coordination ability of a donor molecule towards different metal ions increased in proportion to their ionization potential. In addition, based on the extraction distribution coefficient, we found that 12-crown-4 can selectively extract Cu²⁺ and Be²⁺ ions from aqueous solutions of mixed cations. Obviously, the stability of complexes and the extraction power of extractants depend greatly on the nature of the metal ions. Calculation results from our study could be used to predict the extraction power of this crown ether and could play a guiding role in planning experiments.     

A theoretical study of the H2SO4+H2O → HSO4 −+H3O+ reaction at the surface of aqueous aerosols

The surface region of sulfate aerosols (supercooled aqueous concentrated sulfuric acid solutions) is the likely site of a number of important heterogeneous reactions in various locations in the atmosphere, but the surface region ionic composition is not known. As a first step in exploring this issue, the first acid ionization reaction for sulfuric acid, H₂SO₄ + H₂O HSO₄^– + H₃O⁺, is studied via electronic structure calculations at the Hartree–Fock level on an H₂SO₄ molecule embedded in the surface region of a cluster containing 33 water molecules. An initial H₂SO₄ configuration is selected which could produce H₃O⁺ readily available for heterogeneous reactions, but which involves reduced solvation and is consistent with no dangling OH bonds for H₂SO₄. It is found that at 0 K and with zero-point energy included, the proton transfer is endothermic by 3.4 kcal/mol. This result is discussed in the context of reactions on sulfate aerosol surfaces and, further, more complex calculations.Contribution to the Jacopo Tomasi Honorary Issue     

Synthesis and Characterization of Sol-Gel Cu-ZrO2 and Fe-ZrO2 Catalysts

Fe-ZrO₂ and Cu-ZrO₂ xerogels were prepared by a sol-gel method. The effect of the hydrolysis catalyst during the gelation step, namely H₂SO₄ or NH₄OH, on the properties of the resulting materials was investigated by XRD, BET, TGA/DTA, TPD of ammonia, FTIR, and TPR. Fe-ZrO₂ and Cu-ZrO₂ xerogels, with sulfuric acid introduced as the hydrolysis catalyst, mainly crystallyzed in the tetragonal phase and exhibited larger surface area and acid amount than those obtained with NH₄OH. Ammonia TPD shows that copper promoted sulfated zirconia is the most acidic material. TGA and FTIR reveal that under oxidizing conditions sulfated zirconia promoted with iron and copper retains more sulfate species than unpromoted sulfated zirconia. Regardless of the hydrolysis catalyst employed, copper promoted catalysts calcined at 600°C, contain a large fraction of copper oxide specieseasily reduced at low temperatures. These copper oxide species are believed to have different environment and interactions with the surface oxygen vacancies of the zirconia support. A FeO-like phase appears to be the most probable one after reduction of Fe-ZrO₂ catalysts prepared with NH₄OH as the hydrolysis catalyst. The formation of Fe° species may be hindered by the high dispersion and interaction of Fe²⁺ ions with the zirconia support. On the other hand, the reduction peaks of iron oxide and sulfate species exhibit a considerable overlap in the TPR profiles of sulfated Fe-ZrO₂ samples. Hence, the nature of the supported phase in the latter samples is rather uncertain.     

Gitterschwingungsspektren. LXIII. Be(lO3)2 · 4 H2O,ein Hydrat mit ungewöhnlicher Bindungsstruktur und Gitterdynamik

Lattice Vibration Spectra. LXIII. Be(IO₃)₂ · 4 H₂O, a Hydrate with Unusual Bonding and Lattice Dynamics The IR and Raman spectra (4000–50 cm^?1) of Be(IO₃)₂ · 4 H₂O and of deuterated specimens are recorded at 90 and 300 K and discussed in terms of the unusual relations of the masses of the atoms involved and the large polarization power of the beryllium ions. Thus, the translatory modes of the Be²⁺ ions (BeO₄ skeleton vibrations), the librations of the H₂O molecules, and the internal vibrations of the IO₃^? ions in the spectral regions of 300–400 and 600–1000 cm^?1 couple and coincide producing unusual v_H/v_D isotopic ratios of partly < 1. The H-bond donor strengths of the water molecules is so much increased (due to the very large ionic potential of Be²⁺ ions, viz. 49 e nm^?1) (synergetic effect) that the H-bonds formed are similar in strength as those in hydrates of hydroxides with the very strong H-bond acceptor group OH^? (v_OD of matrix isolated HDO molecules 2 074 and 2 244 (H₂O I) and 2 206 and 2 349 cm^?1 (H₂O II))     

Kinetics and mechanism of the oxidation of a ferrous complex with an α,α′-diimine chelate ligand by ceric sulfate in aqueous acidic medium by UV-vis absorption spectroscopy

Kinetics of the oxidation of tris(2,2′-bipyridine)iron(II) sulfate by ceric sulfate was spectrophotometrically studied in an aqueous sulfuric acid medium. Different methods, including isolation, integration and half-life, were employed to determine the reaction order. The redox reaction was found to be first-order with respect to the reductant, tris(2,2′-bipyridine)iron(II) sulfate, and the oxidant, ceric sulfate. Complex kinetics was observed with an increase in the initial concentration of the oxidant. The influence of the dielectric constant, [H⁺] and [SO₄ ^2-] on the rate was also investigated. The increase in the dielectric constant and H⁺ ion concentration of the medium retard the rate, while an increase in the SO₄ ^2- ion concentration first accelerates the rate, and then retards the reaction. The effect of each factor, i.e., the dielectric constant, H⁺ ions and SO₄ ^2- ions, suggests that Ce(SO₄)₃ ^2- is the active species of cerium(IV). A rate law consistent with the observed kinetic data and the proposed mechanism is suggested to be: {fx631-1     

The Soret effect with chemical reaction in aqueous sulfuric acid solutions

The Soret coefficient of aqueous sulfuric acid has been determined conductimetrically from 0.0005 to 0.2m at 25°C. The derived enthalpies of transport increase sharply as the concentration drops, approaching a limiting value near 35 kJ-mol^–1. The increase, in the enthalpy of transport at low concentrations is due to the large intrinsic enthalpies of transport of the hydrogen and sulfate ions that are produced by the dissociation of bisulfate ions. The enthalpy of dissociation of the bisulfate ions reduces the acid's enthalpy of transport by up to 1.8 kJ-mol^–1.     

Ammelinium Sulfate Monohydrate and Ammelinium Sulfate Cyanuric Acid – Synthesis and Structural Characterization

Two ionic carbon nitride type compounds containing the ammelinium cation, ammelinium sulfate cyanuric acid (6C₃N₅H₆O⁺ · 3SO₄^2– · 1?C₃N₃H₃O₃ · H₂O) ( 1 ) and ammelinium sulfate monohydrate (2C₃N₅H₆O⁺ · SO₄^2– · H₂O) ( 2 ) were synthesized through hydrolysis of melam (C₆N₁₁H₉) in diluted sulfuric acid. 1 crystallizes in hexagonal space group P6₃ (no. 173) with lattice parameters of a = 14.642(3), c = 13.113(4), and Z = 2. The structure is comprised of protonated ammelinium ions and neutral cyanuric acid molecules, which form a layered structure, as well as sulfate ions that span through these layers. 2 crystallizes in the triclinic space group P1 with lattice parameters of a = 7.404(3), b = 9.673(4), c = 10.040(4), α = 91.098(15), β = 109.884(10), γ = 92.567(13), and Z = 2. As for 1 , the ammelinium rings form layers with the sulfate ions located in between. In both structures, no extended hydrogen bond networks between the respective triazine‐based molecules are formed. Instead, single molecules or small building blocks occur isolated and interact primarily with sulfate anions. Compound 1 , which was obtained phase pure, was further investigated by FTIR spectroscopy, solid‐state NMR spectroscopy and powder X‐ray diffractometry.     

Boron–π interactions in two 3-(dihydroxyboryl)anilinium salts analyzed by crystallographic studies and supported by the noncovalent interactions (NCI) index theoretical approach

In the title compounds, 3-(dihydroxyboryl)anilinium bisulfate monohydrate, C₆H₉BNO₂⁺·HSO₄⁻·H₂O ( I ), and 3-(dihydroxyboryl)anilinium methyl sulfate, C₆H₉BNO₂⁺·CH₃SO₄⁻ ( II ), the almost planar boronic acid molecules are linked by pairs of O—H…O hydrogen bonds, forming centrosymmetric motifs that can be described by the graph-set R₂²(8) motif. In both crystals, the B(OH)₂ group acquires a syn–anti conformation (with respect to the H atoms). The presence of the hydrogen-bonding functional groups B(OH)₂, NH₃⁺, HSO₄⁻, CH₃SO₄⁻ and H₂O generates three-dimensional hydrogen-bonded networks, in which the bisulfate (HSO₄⁻) and methyl sulfate (CH₃SO₄⁻) counter-ions act as the central building blocks within the crystal structures. Furthermore, in both structures, the packing is stabilized by weak boron–π interactions, as shown by noncovalent interactions (NCI) index calculations.     

Electrochemical Condensation of Methylviologen on Specifically‐adsorbed Anion Layers

The adsorption of methylviologen dications (MV²⁺) on single‐crystalline Au electrodes in both H₂SO₄ and HClO₄ was examined. MV²⁺ strongly interacted with sulfate and bisulfate anions adsorbed on the Au(111) electrode surface in 0.05 M H₂SO₄ under a controlled potential of 1.25 V vs. the reversible hydrogen electrode (RHE). A characteristic non‐Faradaic current was observed at 1.10 V vs. RHE. When adsorption of MV²⁺ was carried out in 0.1 M HClO₄, the electrochemical response of MV²⁺ was less than that obtained in H₂SO₄. The results show that the formation of a highly ordered sulfate/bisulfate adlayer plays an important role in the formation of condensed MV²⁺ layers. Examination of polycrystalline Au and Au(100) electrodes revealed a poor electrochemical response due to the surface roughness of the Au substrate, but the electrochemical detection was applicable to polycrystalline Au electrodes. A systematic investigation of the structural dependency of viologen derivatives showed that molecular size is important for electrostatic interactions with a highly ordered sulfate/bisulfate adlayer. The findings of the present study demonstrate successful detection of MV²⁺ at a concentration of ≤1 pM with a non‐Faradaic current.     

The behaviour of beryllium μ4-oxo-μ-carboxylates under electron impact

The electron impact mass spectra of eight polynuclear beryllium complexes Be₄O(RCO₂)₆ (R?H, CH₃, C₂H₅) and Be₄O(RCO₂)₅OR′ (R?CH₃, R′?H, CH₃, C₂H₅, C₃H₇; R?C₂H₅, R′?C₂H₅) are reported. The major fragmentations involve the elimination of (RCO)₂O (RCOOR′) or Be(RCO₂)₂ (Be(RCO₂)OR′) from the ions [M? L]⁺ and of {(R? H)CO}, (R′? H), H₂O and BeO from the lighter ions. The fragmentation patterns are practically independent of the organic groups present and can be rationalized by stereochemical considerations.     

Kinetics of cerium (IV) oxidation of mandelic acid. Ionic strength and specific cation effects

The kinetics of the redox reaction between mandelic acid (MA) and ceric sulfate have been studied in aqueous sulfuric acid solutions and in H₂SO₄? MClO₄ (M⁺ = H⁺, Li⁺, Na⁺) and H₂SO₄? MHSO₄ (M⁺ = Li⁺, Na⁺, K⁺) mixtures under various experimental conditions of total electrolyte concentration (that is, ionic strength) and temperature. The oxidation reaction has been found to occur via two paths according to the following rate law: rate = k[MA] [Ce(IV)], where k = k₁ + k₂/(1 + a)²[HSO₄^?]² = k₁ + k₂/(1 + 1/a)²[SO₄^2?]², a being a constant. The cations considered exhibit negative specific effects upon the overall oxidation rate following the order H⁺ ? Li⁺ < Na⁺ < K⁺. The observed negative cation effects on the rate constant k₁ are in the order Na⁺ < Li⁺ < H⁺, whereas the order is in reverse for k₂, namely, H⁺ ? Li⁺ < Na⁺. Lithium and hydrogen ions exhibit similar medium effects only when relatively small amounts of electrolytes are replaced. The type of the cation used does not affect significantly the activation parameters.