Synthesis of oxime phosphoranes from reaction between triphenylphosphine and acetylenic esters in the presence of oxime derivatives

A new one-pot, simple and effective procedure is presented for the preparation of O-containing phosphorus ylides by the Michael addition reaction of N-methylpyrrole-2-carbaldehydoxime, pyridin-2-carbaldehydoxime or acetophenonoxime with acetylenic esters.     

Structural Phase Transition and the Dielectric Permittivity of the Model Lipid Bilayer [(CH2)12(NH3)2]CuCl4

Structural phase transitions in the lipid-like bilayer material [(CH₂)₁₂(NH₃)₂]CuCl₄ have been observed using differential thermal scanning. The compound shows an irreversible thermochromic transition at ? 465 K and three reversible transitions at T ₁ = 433 ± 4 K and T ₂ = 411 ± 2 K and T ₃ = 358 K. The transition at 350 K is ascribed to chain melting. The other two correspond to crystalline phase transformation.

Phase (IV) T₃ = 358 ± 2K Phase (III) T₂ = 411 ± 2K Phase (II) T₁ = 433 ± 4K Phase (I)

Dielectric permittivity is studied as a function of temperature in the range 300-440 K and frequency, range (60 Hz-100 kHz). It confirms the observed transitions. The dielectric permittivity reflects rotational and conformational transitions for the compound. The variation of the real part of the conductivity with temperature is thermally activated in the temperature range above 350 K, with frequency-dependent activation energy, the values of activation energy lie in the range of ionic hopping. The dependence of the conductivity on frequency follows the universal power law σ = σ₀ + A(T) ω ^{s ( T )} with 0<s<1. Comparison of this material with other members of the series is discussed     

New copper(II) complexes produced by the template reaction of acetoacetic-2-pyridylamide and amino-aliphatic alcohols

The template condensation of acetoacetic-2-pyridylamide with amino aliphatic alcohols such as 2-aminoethanol (HL1) and 3-amino propanol (HL2) in the presence of copper(II) ions gave octahedral complexes, which have been characterized by elemental analyses, u.v.-vis. and i.r. spectra, conductivity, d.t.a, magnetic and e.s.r. measurements. The molar conductance in DMF indicate that the complexes are non-ionic in character. The e.s.r. spectra of solid complexes (2) and (5) at room temperature indicate axial type symmetry (dx2-y2) with covalent bond character.     

Polyhydroxyquinoline-carbon nanotube chelating resin for selective adsorption of lead ions: multivariate optimization,isothermic, and thermodynamic study

In this work a facile hydrothermal route has been employed to prepare a multiwall carbon nanotube wrapped in a chelating resin. 8-Hydroxyquinoline and p-formaldehyde were used as monomer and linker for polymer synthesis. The prepared composite was employed as an efficient adsorbent for lead adsorption and preconcentration from various matrices. Effective parameters on lead adsorption have been optimized by central composite design. Results showed that equilibrium adsorption was obtained at pH = 4, with a shacking time of 15 min and adsorbent dosage of 15 mg. Isotherm study showed that the sorbent has adsorbent capacity of 250 mg g^?1; moreover, the process followed a Langmuir isotherm model. Thermodynamic investigation confirmed that lead adsorption is spontaneous, as well as follows endothermic path.     

Characterization and High Level Expression of Acidic Endoglucanase in Pichia pastoris

Bioconversion of cellulosic material into glucose needs cellulase enzymes. One of the most important organisms that produces cellulases is Trichoderma reesei, whose cellulose enzymes are probably the most widely used in the industry. However, these enzymes are not stable enough at high pH and temperatures. The optimized synthetic endoglucanase II gene with Pichia pastoris codon preferences was secretary expressed in P. pastoris. Recombinant enzyme characterization showed maximum activity at pH 4.8 and temperature 75 °C, and it demonstrated increasing thermal stability in high temperature. The enzyme maintained its activity in a wide pH range from 3.5 to 6.5. The optimization of fermentation medium was carried out in shaking flasks. Recombinant protein expression at optimum conditions (pH 7, temperature 25 °C, and 1 % methanol induction) for 72 h demonstrated 2,358.8 U/ml endoglucanase activity units. To our knowledge, this is the highest acidic thermophilic endoglucanase activity that is reported in crude intracellular medium in P. pastoris. We conclude that P. pastoris is an appropriate host for high-level expression of optimized endoglucanase gene with improved thermal stability.     

Optimization of cloud point extraction of copper with neocuproine from aqueous solutions using Taguchi fractional factorial design

Taguchi method was applied to optimize cloud point extraction (CPE) conditions for preconcentration and determination of trace amounts of copper by UV-Vis spectrophotometry. Briefly, the copper ions formed complexes with neocuproine in aqueous solution; then, Triton X-114 (0.15%, w/v) was added and phase separation occurred upon heating to 60°C. The copper complexes were preconcentrated into the small volume of the surfactant-rich phase; after centrifugation, the surfactant-rich phase was diluted with methanol and absorbance was measured at 455 nm. The main factors affecting the CPE were evaluated and optimized with Taguchi orthogonal array design (OA ₂₅). Under the optimum conditions, the calibration curve was linear in the range 2–500 μg/L (r ² > 0.997). The limit of detection and preconcentration factor were 1.8 μg/L and 37.2, respectively. The applicability of the proposed method was successfully confirmed by preconcentration and determination of trace amounts of copper in water samples and satisfactory results were obtained.     

Preconcentration of radioiodine as AgI and purification from radiotellurium waste

A radiochemical method was investigated for separation and preconcentration of radioiodine from alkaline radiotellurium waste solution as Ag¹²⁵I followed by recovery of ¹²⁵I into aqueous NH₃ solution and final purification by wet distillation. ¹²⁵I–^123mTe radiotracer solution (5 M NaOH) was equilibrated with prepared silver granules for different times and it was found that ¹²⁵I was quantitatively removed from the aqueous phase after 7.0 h. The ¹²⁵I-loaded silver was then equilibrated with ammonia solution in the presence of one of different reducing agents (namely, sodium borohydride, dextrose and zinc dust). Different concentrations of NH₃ solution and reducing agents were studied. Quantitative recovery of ¹²⁵I in the aqueous phase was achieved after 1.0 h of equilibration of ¹²⁵I-loaded silver granules with 2.7M NH₃ solution in the presence of Zn dust with a Zn:Ag molar ratio of 0.5. Purification of the recovered ¹²⁵I was carried out by wet distillation from 20 % H₂SO₄ in the presence of H₂O₂. The distilled off ¹²⁵I was received in a mixture solution of 0.1M NaOH and 0.01M Na₂S₂O₃ with a radionuclidic purity of ≥99.99 %, radiochemical purity of ~98.8 % (as I^? anions) and pH-value of ~13.     

Dioxouranium(VI) mixed ligand complexes containingo-substituted benzoic acid and α-amino acids

Summary Mixed ligand complexes of general formula [UO₂L¹L²-(H₂O)_n], where L¹ iso-hydroxy-,o-mercapto- oro-aminobenzoic acid and L² is glycine, L-alanine, or L-valine, have been prepared and characterized. The uranium atom in these complexes is 6- or 8-coordinate. Both acid ligands are bidentate, bonding through the ionized –COO^–– group and either O, N or S atoms.     

Role of bio-derived zinc oxide nanoparticles in antifungal and photocatalytic activities

Research on Chemical Intermediates - Zinc oxide nanoparticles (ZnO-NPs) are known as a material in the treatment of environmental pollutions. In this study, ZnO-NPs were synthesized using...