Synergistic extraction of some univalent cations into nitrobenzene by using cesium dicarbollylcobaltate and calix[4]arene-bis(t-octylbenzo-18-crown-6)

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M⁺ (aq) + CsL⁺ (nb) ? ML⁺ (nb) + Cs⁺ (aq) taking place in the two–phase water–nitrobenzene system (M⁺ = K⁺, Rb⁺, $ {\text{NH}}_{4}^{ + } $ , Ag⁺, Tl⁺; L = calix[4]arene-bis(t-octylbenzo-18-crown-6); aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Furthermore, the stability constants of the ML⁺ complexes in nitrobenzene saturated with water were calculated; they were found to increase in the following cation order: $ {\text{NH}}_{4}^{ + } $  < K⁺ < Ag⁺ < Rb⁺ < Tl⁺.     

Extraction of cesium into nitrobenzene by using ammonium and thallium dicarbollylcobaltates in the presence of polypropylene glycol PPG 425

Extraction of microamounts of cesium by nitrobenzene solutions of ammonium dicarbollylcobaltate (NH₄ ⁺B^?) and thallium dicarbollylcobaltate (Tl⁺B^?) in the presence of polypropylene glycol PPG 425 (L) has been investigated. The equilibrium data have been explained assuming that the complexes ML⁺ (M⁺ = NH ₄ ⁺ , TI⁺, Cs⁺; L = PPG 425) are present in the organic phase. Furthermore, the stability constants of the cationic complex species NH₄L⁺ and TlL⁺ in nitrobenzene saturated with water have been determined as log β (NH₄L _org ⁺ ) = 4.58 and log β (TlL _org ⁺ ) = 5.27.     

Complexation of the cesium cation with 1,3-alternate-25,27-bis(1-octyloxy)calix[4]arene-crown-6

From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium Cs⁺(aq) + I^?(aq) + 1(nb) ? 1·Cs⁺(nb) + I^?(nb) taking place in the two–phase water–nitrobenzene system (1 = 1,3-alternate-25,27-bis(1-octyloxy)calix[4]arene-crown-6; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log K _ex (1·Cs⁺, I^?) = 2.9 ± 0.1. Further, the stability constant of the 1·Cs⁺ complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log β_nb (1·Cs⁺) = 8.8 ± 0.1. Finally, by using quantum–mechanical DFT calculations, the most probable structure of the resulting cationic complex species 1·Cs⁺ was derived.     

Complexation of the cesium cation with lithium ionophore VIII: extraction and DFT study

From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium Cs⁺(aq) + 1·Na ⁺ (nb) = 1·Cs⁺(nb) + Na⁺(aq) taking place in the two-phase water-nitrobenzene system (1 = lithium ionophore VIII; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log K _ex (Cs⁺, 1·Na⁺) = ?0.5 ± 0.1. Further, the stability constant of the 1·Cs⁺ complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log β _nb (1·Cs⁺) = 4.8 ± 0.2. Finally, by using quantum mechanical DFT calculations, the most probable structure of the cationic complex species 1·Cs⁺ was derived. In the resulting complex, the “central” cation Cs⁺ is bound by six bond interactions to the corresponding six oxygen atoms of the parent ligand 1.     

Synergistic extraction of some divalent metal cations into nitrobenzene by using strontium dicarbollylcobaltate and electroneutral macrocyclic lactam receptor

From extraction experiments and $ \gamma $ -activity measurements, the exchange extraction constants corresponding to the general equilibrium M²⁺(aq) + 1·Sr²⁺(nb) $ \Leftrightarrow $ 1·M²⁺(nb) + Sr²⁺(aq) taking place in the two-phase water–nitrobenzene system (M²⁺ = Mg²⁺, Ca²⁺, Ba²⁺, Pb²⁺, Cu²⁺, Zn²⁺, Cd²⁺, $ {\hbox{UO}}_{2}^{2 + } $ , Mn²⁺, Co²⁺, Ni²⁺; 1 = macrocyclic lactam receptor–see Scheme 1; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Moreover, the stability constants of the 1·M²⁺ complexes in nitrobenzene saturated with water were calculated; they were found to increase in the following cation order: Mg²⁺ < Co²⁺ < Cu²⁺, Mn²⁺, Ni²⁺ < Cd²⁺ < Ca²⁺ < Ba²⁺, Zn²⁺ < Pb²⁺ <  $ {\hbox{UO}}_{2}^{2 + } $ .

Anaerobic treatment of rapeseed meal

Rapeseed meal is a solid by-product obtained from rapeseed after oil extraction. This contribution summarises experiences from batch experiments as well as the long-term processing of this substrate in a laboratory stirred anaerobic reactor (continuous stirred-tank reactor). On the basis of the batch tests of hydrolysis, acidogenesis, and methanogenic activity, it was concluded that the anaerobic degradation of rapeseed meal can be performed using a one-step system and it is not necessary to include a hydrolytic-acidogenic step prior to the methanogenic step. Although the methanogenic potential of rapeseed meal appears to be very promising, the long-term processing as a single substrate led to serious problems arising from the inhibitory effects. It was, therefore, co-fermented with crude glycerol from biodiesel production. From the long-term operation of the laboratory model, it may be stated that, due to the co-fermentation of by-products from biodiesel production, the individual inhibition effects can be suppressed to a large extent and biogas production can be stabilised. The maximum organic loading rate in the continuous stirred reactor achieved 2.42 kg m^?3 d^?1 of volatile solids (15 g of rapeseed meal and 20 mL of gas-phase), which was 3.13 kg m^?3 d^?1 of chemical oxygen demand.     

A Proton Complex of p-tert-Butylcalix[4]arene-tetrakis(N,N-dimethylthioacetamide): NMR Evidence and Probable Structure

Using ¹H and ¹³C NMR together with density functional theoretical (DFT) calculations, it is shown that p-tert-butylcalix[4]arene-tetrakis(N,N-dimethylthioacetamide) (1) forms a stable equimolecular complex with proton in the form of hydroxonium ion in nitrobenzene-d ₅. Protons were offered by hydrogen bis(1,2-dicarbollyl) cobaltate (HDCC) and converted to hydroxonium ions by traces of water. The complex 1·H₃O⁺ adopts a slightly asymmetric but rapidly motionally averaged conformation, which is distinctly more cone-like than ligand 1. The hydroxonium ion H₃O⁺ is bound partly to thiocarbonyl sulphur atoms and partly to phenoxy oxygen atoms of 1 by strong hydrogen bonds and other electrostatic interactions.

     

Restriction of Spin Probe Motions in Polymer Composites Due to Chemical Factors

Abstract

Hyperfine splitting constants of the nitroxyl radical, with and without hydrogen bonds to the surrounding molecules, have been calculated using the UHF method on a 6-31G* base. In polyethylene filled with silica, hydrogen bonds are formed between nitroxyl radicals and —OH groups of the filler. The formation of hydrogen bonds leads to a change in the A _zz value from 3.33 mT for an isolated nitroxyl radical to 3.83 mT for a radical with a hydrogen bond. The relevant values as measured experimentally are 3.4 and 4.0 mT, respectively. The same procedure was used to calculate the theoretical A _zz value for a nitroxyl radical interacting with polyamide via a hydrogen bond. The value was found to be 3.63 mT (experimental value = 3.6 mT). Hydrogen bond formation results in a restricted motion of the nitroxyl radical in a polymeric medium.     

Structural relaxation of PbO–WO3–P2O5 glasses

The structural relaxation of three compositional series of PbO–WO₃–P₂O₅ glasses with composition (0.5 ? x/2)PbO·xWO₃·(0.5 ? x/2)P₂O₅, x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5; 0.5PbO·xWO₃·(0.5 ? x)P₂O₅, x = 0, 0.1, 0.2, and 0.3; and (0.5 ? x)PbO·xWO₃·0.5P₂O₅, x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5 was studied by thermomechanical analysis. The structural relaxation was studied in the transformation region using the Tool–Narayanaswamy–Moynihan’s and Tool–Narayanaswamy–Mazurin’s models. The relaxation function of Kohlrausch Williams and Watts was used. The parameters of both models were calculated by nonlinear regression analysis of thermodilatometric curves measured by thermomechanical analyzer under the constant load. Both models very well describe the experimental data. It was found that the modulus is increasing with increasing amount of WO₃ in all glasses. On the contrary, the width of the spectrum of relaxation times is decreasing with increasing amount of WO₃ in all studied glasses. Both models possess the values of metastable melt thermal expansion coefficient equal to their experimental value.     

Expanding the structural chemistry of the weakly coordinating closo-carborane CB11H12 −: its monoiodo derivatives with and without C 5v symmetry

Two iodo derivatives of closo-CB₁₁H₁₂ ^?, i.e., 12-I-1-CB₁₁H₁₁ ^? (C _5v symmetry) and 7-I-1-CB₁₁H₁₁ ^? (C _s symmetry), were prepared (the latter for the first time) and the influence of differently positioned iodine substituents on the geometry of the CB₁₁ icosahedral core was structurally examined both by X-ray diffraction and quantum-chemical computation at the MP2 level. Observed and computed molecular geometries are in overall agreement. Supramolecular architectures of these two anionic substituted monocarboranes are shown. According to DFT computations at the ZORA-SO/BP86 level, the ¹¹B chemical shifts of the boron atoms to which iodine substituents are bonded are dominated by spin–orbit coupling. Different positions of iodine atoms in these two isomers may result in different acidities of the (C)-H atoms in the icosahedral bodies, as suggested by visually analyzing the corresponding lowest unoccupied molecular orbitals.