Kinetische und thermodynamische Untersuchungen im System AgCl-LiCl-NaCl

In the ternary system silver chloride-lithium chloride-sodium chloride the kinetics of the galvanic deposition of silver on graphite electrodes was investigated as well as its dissolution without current in the molten salt saturated with chlorine gas.In addition the emf-values were measured in the temperature range between 923 K and 1,173 K by means of, the formation cell graphite/Ag(s)/AgCl(l)–LiCl(l)–NaCl(l)/Cl₂ graphite From these data the partial molar free excessGibbs energies were calculated. Using the equation for a multicomponent system as suggested byRedlich-Kister ¹ G _AgCl ^E values were obtained by a non-linear fitting process, where the fit was performed for all investigated temperatures and over the entire concentration range in the ternary system. With the parameters obtained the partial and integral excess valuesG _i ^E ,G ^E ,H _i ^E ,H ^E ,S _i ^E andS ^E were calculated.

     

Complexes of dioxouranium(VI) with zwitter-ionic forms of Bi- and tetra-dentateSchiff bases

Potentially bi- and tetra-dentateSchiff bases derived from salicylaldehyde react with hydrated uranyl salts to give complexes: UO₂H₂ LX ₂, UO₂H₂ LX ₂ and UO₂(HL)₂ X ₂ [H₂ L=N,N-propane-1,3-diylbis(salicylideneimine), H₂ L=N,N-ethylenebis(salicylideneimine) and HL=N-phenylsalicylideneimine;X ^–=Cl^–, Br^–, I^–, NO₃ ^–, ClO₄ ^–, and NCS^–]. Because of marked spectral similrities with the structurally known Ca(H₂ L) (NO₃)₂, theSchiff bases are coordinated through the negatively charged phenolic oxygen atoms and not the nitrogen atoms of the azomethine groups which carry the protons transferred from phenolic groups on coordination. Halide, nitrate, perchlorate and thiocyanate groups are covalently bonded to the uranyl ion, resulting a 6-coordinated uranium ion in the halo and thiocyanato complexes and 8-coordinated in nitrato and perchlorato complexes.

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Komplexe von Dioxouranyl(VI) mit zwitterionischen Formen von zwei- und vierzähnigen Schiff-Basen

Zusammenfassung Von Salizylaldehyd abgeleitete zwei- und vierzähnigeSchiff-Basen reagieren mit hydratisierten Uranylsalzen zu Komplexen folgenden Typs: UO₂H₂ LX ₂, UO₂H₂ LX ₂ und UO₂(HL)₂ X ₂ [H₂ L=N,N-Propan-1,3-diylbis(salicylidenimin), H₂ L=N,N-Ethylen-bis(salicylidenimin) und HL=N-Phenylsalicylidenimin;X ^–=Cl^–, Br^–, I^–, NO₃ ^–, ClO₄ ^– und NCS^–]. Auf Grund eindeutiger spektraler Ähnlichkeiten mit dem bekannten Ca(H₂ L) (NO₃)₂ wird auf Koordination über die negativ geladenen phenolischen Sauerstoffatome (und nicht über die Azomethin-Stickstoffe) geschlossen. Die AnionenX ^– sind kovalent an das Uranyl-Ion gebunden; damit ergibt sich ein hexakoordiniertes Uranyl-Ion für die Halogen- und Thiocyanat-Komplexe und Oktakoordination für die Nitrat- und Perchlorat-Komplexe.

     

Asymmetric Synthesis of （R）- and （S）-Moprolol

A simple and effective procedure for the enantioselective synthesis of （R）- and （S）-moprolol was described. The key step was the asymmetric synthesis of enantiopure （R）- and （S）-guaifenesin, which were synthesized from enantioenriched （R）-3-chloro-l,2-propanediol and （S）-epichlorohydrin via kinetics of hydrolysis resolution of racemic epichlorohydrin by chiral Salen-Co^Ⅲ complex. The e.e. values of both the optical compounds were above 98%, and the chemical structures of the target compounds were confirmed by ^1H NMR, ^13C NMR, IR, and MS.     

Solvation Structure and Complexation of the Manganese(II) Ion in N,N-Dimethylpropionamide and N,N,N′,N′-Tetramethylurea Studied by Means of Titration Calorimetry and Raman Spectroscopy

Aprotic N,N-dimethylpropionamide (DMPA) and N,N,N′,N′-tetramethylurea (TMU) are both strong donor solvents and coordinate to metal ions through the carbonyl oxygen atom. These solvents show a different conformational aspect in the bulk phase, i.e., DMPA exists as either a planar cis or a nonplanar staggered conformer, while TMU exists in a single planar cis conformer. It has been established that the manganese(II) ion is solvated by five molecules in both solvents. Interestingly, although the planar cis conformer of DMPA is more favorable than the nonplanar staggered one in the bulk phase, the reverse is the case in the coordination sphere of the metal ion, i.e., a conformational change occurs upon solvation. To reveal the thermodynamic aspect of this conformational change, the complexation of Mn(II) with bromide ions in DMPA and TMU has been studied by titration calorimetry at 298 K. It was found that the Mn(II) ion forms mono-, di- and tri-bromo complexes in both solvents, and their formation constants, enthalpies and entropies were obtained. The Δ H∘₁ value for MnBr⁺ strongly depends on the solvent, i.e., it is positive (19.4 kJ-mol⁻¹) in DMPA and negative (−8.7 kJ-mol⁻¹) in TMU, whereas the Δ H^∘₂ and Δ H∘₃ values for the stepwise formation of MnBr₂ and MnBr₃⁻ are both small and negative. The enthalpy of transfer Δ_tH^∘ from DMPA to TMU, which is evaluated on the basis of the extrathermodynamic TATB assumption, is 25.5 kJ-mol⁻¹ for Mn²⁺ and −3.6 kJ-mol⁻¹ for MnBr⁺. These values indicate that the difference between the formation enthalpy of MnBr⁺ in the two solvents, Δ H^∘₁ (DMPA) – Δ H∘₁ (TMU), is mainly ascribed to the value of Δ_tH^∘(Mn²⁺). It is found that the metal ion is also five-coordinated in the monobromo complex, MnBr(DMPA)₄⁺ . The enthalpy for the conformational change of DMPA from its planar cis to the nonplanar staggered form is evaluated to be −11 and −5.5 kJ-mol⁻¹ for Mn(DMPA)₅^{2 +} and MnBr(DMPA)₄⁺, respectively. Note that these values are significantly smaller than the corresponding value (5.0 kJ-mol⁻¹) in the bulk phase. We thus conclude that, although steric hindrance among solvent molecules is reduced by replacing one DMPA of Mn(DMPA)₅^{2 +} with the relatively small bromide ion, DMPA molecules are still sterically hindered in the MnBr(DMPA)₄⁺ complex.     

Effect of copper and manganese ions on activities of laccase and peroxidases in three Pleurotus species grown on agricultural wastes

Copper (Cu²⁺) and manganese (Mn²⁺) ions influenced laccase (Lac) and peroxidase production in Pleurotus eryngii, Pleurotus ostreatus, and Pleurotus pulmonarius. In P. eryngii, the optimum Cu²⁺ concentration for Lac production was 1 mM and for peroxidases 10mM, and Mn²⁺ concentration of 5mM led to peaks of Lac and peroxidase activity. In P. ostreatus HAI 493, the highest level of Lac activity was at Cu²⁺ concentrations of 1 and 10 mM and Mn²⁺ concentration of 1mM, respectively. The absence of Cu²⁺ and Mn²⁺ caused the highest levels of peroxidase production. In P. ostreatus HAI 494, the highest level of Lac activity was at a Cu²⁺ concentration of 5 mM and at Mn²⁺ concentration of 1 mM, respectively. High levels of peroxidase activity were found in the medium without and with 1mM Cu²⁺, and at 1 and 5 mM Mn²⁺, respectively. In P. pulmonarius, the highest Lac activity was found in the presence of 5 mM Cu²⁺ and 5 mM Mn²⁺, respectively. The absence of Cu²⁺ and Mn²⁺ as well as their presence at a concentration of 1 mM led to the peaks of peroxidase activities.     

On the inverse miniemulsion copolymerization and terpolymerization of acrylamide, <Emphasis Type="Italic">N,N′</Emphasis>-methylenebis(acrylamide) and methacrylic acid

The kinetics of free-radical copolymerization and terpolymerization of acrylamide (AAm), N, N′-methylenebis(acrylamide) (MBA) and methacrylic acid (MA) in the inverse water/monomer/cyclohexane/Tween 85 miniemulsion was investigated. Polymerizable sterically-stable miniemulsions were formulated in cyclohexane as a continuous medium. Polymerizations are very fast and reach the final conversion within several minutes. The dependence of the polymerization rate vs. conversion is described by a curve with two nonstationary rate intervals. The maximum rate of polymerization slightly increases with increasing concentration of crosslinking monomer (MBA) and strongly decreases by the addition of MA. The rate of polymerization is inversely proportional to the 0.9 ^th and 1.8 ^th power of the particle concentration without and with MA, respectively. The number of polymer particles is inversely proportional to the 0.18 ^th and 0.13 ^th power of MBA concentration. The kinetic and colloidal parameters of the miniemulsion polymerization are discussed in terms of microemulsion polymerization model.     

Synthesis,spectral characterization,redox and antimicrobial activity of Schiff base transition metal(II) complexes derived from 4-aminoantipyrine and 3-salicylideneacetylacetone

A novel tetradentate N₂O₂ type Schiff base, synthesized from 1-phenyl-2,3-dimethyl-4-aminopyrazol-5-one(4-aminoantipyrine) and 3-salicylidene-acetylacetone, forms stable complexes with transition metal ions such as Cu ^II , Ni ^II , Co ^II and Zn ^II in ethanol. Microanalytical data, magnetic susceptibility, IR, UV-Vis.,¹H-NMR, ESR and Mass spectral techniques were used to confirm the structures. Electronic absorption spectra of the complexes suggest a square-planar geometry around the central metal ion. These complexes show higher conductance values, supporting their electrolytic nature. The monomeric nature of the complexes was confirmed from their magnetic susceptibility values. Cyclic voltammogram of the copper(II) and nickel(II) complexes in DMSO solution at 300 K were recorded and the results are discussed. The X-band ESR spectra of the copper complex were recorded and the molecular orbital coefficient values were calculated from the spectra. The in vitro antimicrobial activities of the investigated compounds were tested against bacteria such as Klebsiella pneumoniae, Staphylococcus aureus, Bacillus subtilis and Escherichia coli and fungi like Aspergillus niger and Rhizoctonia bataicola. Most of the metal chelates show higher antimicrobial activity for the above microorganisms than that of the free ligand.     

Kinetics of electrode reaction coupled to ion transfer across the liquid/liquid interface

In the theoretical model it is assumed that a graphite disk electrode is covered by a thin film of solution of decamethylferrocene (dmfc) and some electrolyte CX in nitrobenzene and immersed in an aqueous solution of the electrolyte MX. Oxidation of dmfc is accompanied by the transfer of anion X ⁻ from water into nitrobenzene since it is also assumed that cations dmfc ⁺ and C ⁺ are insoluble in water and cation M ⁺ is insoluble in nitrobenzene. Kinetic parameters of the electrode reaction can be determined if the total potential difference across the nitrobenzene/water interface is maintained constant by adding the electrolytes CX and MX in concentrations which are much higher than the initial concentration of dmfc in nitrobenzene.     

Kinetic and equilibrium study of the deprotonation of 4-nitrophenyl[bis(ethylsulphonyl)]methane by organic bases in acetonitrile in the presence of common cation BH<Superscript>+</Superscript> and tetrabutylammonium perchlorate

The results of kinetic and equilibrium experiments with the set of reaction of proton abstraction from 4-nitrophenyl[bis(ethylsulphonyl)]methane in acetonitrile are reported. Two strong organic bases are used: 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) and 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD). The rates of proton transfer reaction have been measured by T-jump method in the presence of perchlorate of the appropriate base as a common cation BH⁺ and supporting electrolyte-tetrabutylammonium perchlorate (TBAP) in the temperature range between 20–40°C are: k _H =1.32×10⁷−2.00×10⁷ and 2.82×10⁷−4.84×10⁷ dm ³mol⁻¹s⁻¹ for MTBD and TBD respectively. The enthalpies of activation ΔH _MTBD ^≠ =13.5 and ΔH _TBD ^≠ =18.1 kJmol⁻¹. The entropies of activation are negative: ΔS _MTBD ^≠ =−62.3 and ΔS _TBD ^≠ =−40.3 Jmol⁻¹K⁻¹. The change of the absorbance of the anion of 4-nitrophenyl[bis9ethylsulphonyl)]methane at the temperature 25°C in the presence of common cation BH⁺ gives the equilibrium constants K=705 and 906 M⁻¹ for MTBD and TBD respectively. Kinetic and equilibrium results are discussed. The possible mechanism of proton transfer reaction between 4-nitrophenyl[bis(ethylsulphonyl)]methane and cyclic organic bases: MTBD and TBD in acetonitrile is proposed.     

Removal of <Superscript>60</Superscript>Co<Superscript>2+</Superscript> and <Superscript>137</Superscript>Cs<Superscript>+</Superscript> ions from low radioactive solutions using <Emphasis Type="Italic">Azolla caroliniana</Emphasis> willd. water fern

This study concerns the removal of the ¹³⁷Cs⁺ and ⁶⁰Co²⁺ β+γ-radioactive ions in Azolla caroliniana Willd. water fern. The living fern and two different types of biosorbent prepared from Azolla caroliniana were tested to remove the above-mentioned radioactive ions from dilute solutions, in the absence and in the presence of the ionic competition. Effective ¹³⁷Cs⁺ and ⁶⁰Co²⁺ ions removal from low radioactive wastewaters was demonstrated. The time dependent K _d (t) values were calculated from the absorption data. These results indicate that removal process achieved equilibrium in about 120 min and that it involves two steps: rapid and slow absorption; the active process (metabolic bioaccumulation on the living fern) was responsible for above one half of the total removal process. A thin layer radiochromatography study leads to the conclusion that the biochemical components in which ¹³⁷Cs⁺ and ⁶⁰Co²⁺ place themselves are of a polysaccharide and lipoid fractions.     

B-frame supported bimetallics. [(PMe2ph)2PtB9H11Ru(η-PrC6H4Me)] and [(PMe2ph)2PtB9H9Ru(η-PrC6H4Me)]; an interesting pair of electron-deficient nido and closo geometries

[7,7-(PMe₂Ph)₂-9-(η⁶-^isoPrC₆H₄Me)-7,9-PtRuB₉H₁₁] has a formal closo Wadian cluster-electron count, but a nido geometry, whereas [1-(η⁶-^isoPrC₆H₄Me)-4,4-(PMe₂Ph)₂-1-4-RuPtB₉H₉], which does have a closo geometry, has a formal sub-closo cluster electron count; both compounds are formed in the reaction between [6-(η⁶-^isoPrC₆H₄Me)-nido-6 RuB₉H₁₃], KH and [PtCl₂(PMe₂Ph)₂].     

ESR study of the thermal decomposition of di-tert-butoxy-tert-butyl alumotrioxide formed in the reaction of tri-tert-butoxyaluminum with tert-butyl hydroperoxide

Tri-tert-butoxyaluminum reacts with tert-butyl hydroperoxide to produce di-tert-butoxy-tert-butyl alumotrioxide, which decomposes heterolytically to form singlet dioxygen and homolytically with the O—O bond cleavage. The Bu^tOO^·, (Bu^tO)₂AlOO^·, Bu^tO^·, and (Bu^tO)₂AlO^· radicals were identified by ESR using spin traps. These findings confirm the formation of aluminum-containing trioxide. The above radicals initiate alkylarene oxidation by the tri-tert-butoxyaluminum—tert-butyl hydroperoxide system. The carbon-centered and alkylperoxy radicals originated from the oxidized substrates were identified.     

Der Einfluß großer Salzkonzentrationen auf die Oxydationsreaktion von Fe(phen) 3 2+ mit Ce(IV) in Schwefelsäure

The influence of NaClO₄, NaCl and Na₂SO₄ on the oxidation of Fe(phen) ₃ ²⁺ by Ce(IV) was investigated by means of the stopped-flow method. At the concentrations range of NaClO₄ and NaCl 0.1–1.0M the rate constant values decrease from 1.03·10⁵ to 0.56·10⁵M^–1s^–1 and from 1.08·10⁵ to 0.81·10⁵M^–1s^–1 respectively.In varying concentrations of Na₂SO₄ solutions (0.05–0.35M) the rate constant values decrease from 1.05·10⁵M^–1s^–1 to 0.45·10⁵M^–1s^–1.Taking into account the negative salt effect the mechanism of the reaction progress is proposed.

     

Synthesis,structure and isomerism of “three-bridge” exo-nido-osmacarborane clusters

The reaction of OsCl₂(PPh₃)₃ with [nido-7-R¹-8-R²-C₂B₉H₁₀]K⁺ produced a series of new exo-nido-osmacarborane complexes exo-nido-5,6,10-[Cl(Ph₃P)₂Os]-5,6,10-(-H)₃-10-H-7-R¹-8-R²-7,8-C₂B₉H₆ (1: R¹ = R² = H; 2: R¹ = R² = Me; 3: R¹ = R² = PhCH₂; 4: R¹ + R² = 1,2-C₆H₄(CH₂)₂; 5: R¹ = H, R² = Me) in which the osmium-containing group is linked to the nido-carborane ligand through three two-electron three-center bonds. Compounds 1—5 are formed as mixtures of symmetric (a) and asymmetric (b) isomers; pure symmetric isomers 2a and 4a were isolated by fractional crystallization, and the mixture of isomers 3a, was quantitatively separated into individual compounds 3a and 3b by column chromatography on silica gel. Detailed analysis of the ³¹P{¹H}, ¹H, ¹¹B NMR spectra of 1a,b—5a,b and 2D ¹H-¹H{¹¹B} and ¹¹B{¹H}-¹¹B{¹H} NMR spectra of 3a and 3b was performed. The structures of isomers 2a and 4a were confirmed by an X-ray diffraction study. According to the NMR and X-ray diffraction data, the isomerism of exo-nido-complexes 1a,b—5a,b is actually the cis—trans-isomerism of ligand arrangement in the octahedral coordination of the Os atom.     

Konzentrations- und Temperaturabhängigkeit der Viskosität von Polyacrylnitril-Lösungen in Dimethylformamid

Viscosity measurements were carried out with polyacrylonitrile dissolved in dimethylformamide up to 0.36 g/ml. The temperature range was 20°C to 130°C, the highest shear gradient applied, 5.6·10³s^–1. The temperature variation of viscosity is reproduced with sufficient accuracy by the equation =k·exp (Q/RT). Bothk andQ increase as concentration increases, and the viscosity increases withc ^1.12 toc ^6.4 Inverse proportionality appears to exist between concentration and the longest relaxation time.

     

On the electrochemical reduction of some Cr(III) complexes inDMSO investigated by cyclic voltammetry

The compounds investigated were: [Cr(en)₃]³⁺, [Cr(ur)₆]³⁺, [Cr(DMSO)₆]³⁺, [Cr(dien)₂]³⁺, [Cr(en)₂(acac)]²⁺, [Cr(en) (acac)₂]⁺ and Cr(acac)₃.A distinctly different behaviour is caused by the introduction of one or moreacac ligands into the molecule. The first step is much more cathodic and quite irreversible, while it is reversible or quasi reversible for the first group of ions. This is due to a -type interaction between theacac ligand and the central ion. This interaction is responsible for a third peak occurring for the second group of compounds and may be attributed to the reduction of the Cr(I) ion.Some correlations were found e.g. between the extinction of thed-d band of the first group of ions and the potential of the first peak, and the number ofacac groups introduced in the second group of compounds and the shift of the potential of the first peak.The determined electrochemical data are tabulated.

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Untersuchungen zur elektrochemischen Reduktion einiger Cr(III)-Komplexe in DMSO mittels zyklischer Voltammetrie

Zusammenfassung Die elektrochemischen Daten einer Reihe von Cr(III)-Komplexen miten-, ur-, DMSO-, dien- undacac-Liganden werden präsentiert und einige Möglichkeiten der Korrelation der physikalischen Eigenschaften der Komplexe werden aufgezeigt.Die erste Stufe bei der Einführung vonacac-Liganden ist auf Grund einer -Wechselwirkung zwischen Ligand und Zentralion irreversibel.

     

Preparation,Structural Characterization and the Molecular Structure of 2,3,5-Trinitro-<Emphasis Type="Italic">p</Emphasis>-xylene

2,3,5-trinitro-p-xylene (TPX) is synthesized by nitration of p-xylene in mixed acid of nitric and sulfuric acid. Single crystal of TPX is cultured from DMF solution using a slow cooling method. The compound is characterized by FT-IR, ¹H NMR and MS techniques. The crystal structure is determined by X-ray⁴ single-crystal diffraction analysis. The crystal belongs to the monoclinic system with space group P_n. Its unit cell parameters are as follows: a = 0.8271(2), b = 0.6011(1), c = 1.0487(2) nm, β = 105.42(2)^∘, V = 0.50263(2) nm³, D_c = 1.593 g/cm³, Z = 2, F(0 0 0) = 248. The molecular structures of TPX have been calculated at the B3LYP/6-31G^** and B3LYP/6-311G^** levels of theory, and its frequencies analysis have also been accomplished at the same level of theory. The thermal decomposition process of the compound was studied using DSC and TG-DTG techniques. The predicted nitro group vibrations with B3LYP/6-311G^** calculation considerably agree with the observed frequencies. The calculated results propose that the structural parameters from the theory are close to those of the crystal structure from the experiments.     

Partial Molar Volumes of Tetraalkylammonium Ions in N, N-Dimethylformamide

The densities of tetraalkylammonium bromide, R₄NBr (R = Et, Pr, Bu, Hex, Hep, Oct), solutions in dimethylformamide have been measured for the composition range (0.05–0.4) mol-kg⁻¹ at 25 ^∘C. Apparent molar V_φ and limiting partial molar volumes ⫫₂^o of the electrolytes have been evaluated. Using the extrapolation values, the limiting partial molar volumes of the tetraalkymammonium ions (⫫_i^o) have been calculated. Analysis of different contributions to the ionic ⫫_i^o indicated partial penetration of solvent molecules into the van der Waal’s volume of tetraalkylammonium (TAA) ions.     

The thermal decomposition of N , N -dimethyl-3-oxaglutaramic acid and the kinetics of its second-stage thermal decomposition reaction

N,N-dimethyl-3-oxa-glutaramic acid was purified and characterized by ¹H-NMR, Fourier transform infrared spectroscopy (FT-IR) and elemental analysis. The thermal decomposition of the title compound was studied by means of thermogravimetry differential thermogravimetry (TG-DTG) and FT-IR. The kinetic parameters of its second-stage decomposition reaction were calculated and the decomposition mechanism was discussed. The kinetic model function in a differential form, apparent activation energy and pre-exponential constant of the reaction are 3/2 [(1−α)^1/3−1]⁻¹, 203.75 kJ·mol⁻¹ and 10^17.95s⁻¹, respectively. The values of ΔS ^≠, ΔH ^≠ and ΔG ^≠ of the reaction are 94.28 J·mol⁻¹·K⁻¹, 203.75 kJ·mol⁻¹ and 155.75 kJ·mol⁻¹, respectively. Supported by the National Natural Science Foundation of China (Grant No. 20106009)     

Über Erdalkalimetalloxogallate. VIII Synthese und Aufbau eines neuen Calciumoxogallats: Ca3Ga4O9

The hitherto unknown compound Ca₃Ga₄O₉ was prepared and investigated by X-ray single crystal methods. Ca₃Ga₄O₉ has orthorhombic symmetry:a=1435.8;b=1682.5;c=532.1 pm; space group C _2v ¹¹ –Cmm2,Z=6. The tetrahedra network (circles of 4 and 5 GaO₄-tetrahedra) and the surrounding of Ca²⁺ are described and discussed with respect to other oxogallates.