Effects of Halogen Bonding in Chemical Activity of Lead(II) Electron Pair: Sonochemical Synthesis,Structural Studies,and Thermal Analysis of Novel Lead(II) Nano Coordination Polymer

The nanoflower lead(II) coordination compound {[Pb(phen)(μ‐CH₃COO)][PF₆]}_n ( 1 ) (phen = 1,10‐phenanthroline) was synthesized by a sonochemical method. The nanostructure was characterized by using scanning electron microscopy (SEM), X‐ray powder diffraction, elemental analysis, and thermal analysis. The single‐crystal X‐ray structure shows that the overall structure of 1 is a 1D coordination polymer. Complex 1 has a bridging acetate pathway. Three halogen bonds observed in the structure and the strong halogen bonding of F–Pb causes chemical activity of the lead electron pair. This is further extended into a 3D supramolecular structure by weak π–π intermolecular interactions. The coordination number of the lead(II) ions is six, resulting in PbN₂O₄. PbO nanoparticles were obtained by the thermolysis of 1 at 180 °C with oleic acid as a surfactant. The morphology and size of the prepared PbO nanoparticles were further observed using scanning electron (SEM) and transmission electron microscopy (TEM), and were analyzed by X‐ray photoelectron spectroscopy (XPS).     

Determination of olive oil acidity by CE

In this work, a CE method for the determination of olive oil acidity was proposed. The method was based on an ethanolic extraction (at 60 degrees C) of the oil long-chain free fatty acids (LC-FFAs) components followed by CE determination in pH 6.86 phosphate buffer at 15 mmol/L concentration containing 4 mmol/L sodium dodecylbenzenesulfonate (SDBS), 10 mmol/L polyoxyethylene 23 lauryl ether (Brij 35), 2% v/v 1-octanol and 45% v/v ACN under indirect UV detection at 224 nm. Although this electrolyte promoted baseline separation of myristic acid (C14:0) (internal standard (IS)) and olive oil major components (palmitic acid (C16:0), oleic acid (C18:1c) and linoleic acid (C18:2cc)) in less than 8 min, after a few injections, the electropherogram profiles were severely altered (peak broadening, migration time shifts, etc.) and the current increased substantially. An adsorption study was conducted revealing that the dissolution of the capillary external polyimide coating during the electrophoretic run caused the detrimental effect. After removal of the capillary tip coating, ten consecutive injections could be performed without any disturbances and this simple procedure was, therefore, implemented during quantitative purposes. The reliability of the proposed method was further investigated by the determination of acidity of an extra virgin olive oil sample in comparison to the established methodology (AOCS method Ca 5a-40, alkaline volumetric titration (AVT)). No statistical differences were found within 95% confidence level. A % acidity of 0.39 +/- 0.02 was found for the olive oil sample under consideration.     

Activity of metal chromate and phosphate supported on ion‐exchange resins toward hydrogen peroxide decomposition

The mixed resins, Dowex MR‐3 and MR‐12, in the H⁺/Cl⁻ form, and the cation resin, Dowex‐50W, in the H⁺ form, were used as a support for some metal chromate and phosphate salts. Similarly, anionic resin, Amberlite IRA‐400, in the Cl⁻ form, was used as a support for some metal chromate salts. The activity of these metal salt‐supported on four different resins toward hydrogen peroxide decomposition was investigated. The decomposition of H₂O₂, with these catalysts, was found to follow first‐order kinetics with respect to [H₂O₂]. Factors that affected the rate of reaction, such as mesh size of the support, amount of supported salt, and the electrostatic interactions, were investigated. With Ag(I)‐chromate supported on mixed resin MR‐3 in the Ag⁺/NO₃⁻ form, the rate of reaction was greater than that with the mixed resin MR‐12 in the same form. Moreover, the rate with Ag(I) chromate supported on the anion resin IRA‐400 in the R‐NO₃⁻ form was greater than mixed resins. Also, the rate with Fe(III) chromate supported on Amberlite IRA‐400 in the R‐CrO₄²⁻ form was greater than other counter‐anionic forms as well as Dowex‐50W resin in the metal ion form. However, Fe(III)‐chromate supported on cation resin R‐Fe³⁺ showed greater activity than other cationic forms. On the other hand, the rate with MR‐3 resin in the Na⁺/PO₄³⁻ form was greater than that in the presence of supported Fe(III) phosphate. However, the rate of reaction increased when Fe(III) was replaced by Ba(II). Iron(III) phosphate supported on Dowex‐50W resin in the Na⁺ form showed greater activity compared to MR‐3 resin in the Na⁺/PO₄³⁻ form. In the case of Fe(III) phosphate supported on mixed resin MR‐12, the rate was much greater than that with unsupported resin. However, when Ba(II) phosphate was incorporated instead of Fe(III) phosphate, the rate of reaction increased considerably. The activity of Fe(III) chromate is greater than that of Fe(III) phosphate supported on the same cation resin. Activation parameters were evaluated and a probable reaction mechanism was proposed. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 667–675, 2000     

Study of Acidity of Aerogels ZrO2-SO42− by Isopropanol Dehydration Reaction, Surface Potential and X-Ray Photoelectron Spectroscopy

Sulphated zirconia aerogels, with definite atomic ratio S/Zr and hydrolysis ratio (H = H₂O/Zr) were prepared by the autoclave method. The addition of sulphate ions causes a decrease of the cristallinity of zirconia. XPS results show the O1s photoelectronpeak which could be decomposed in two components for the reticular oxygen of the zirconia framework and for oxygen attributed to the OH groups and/or sulphates groups, and the S2p photopeak characteristic of sulphates species. The Kelvin probe shows that the value of pure zirconia is around 200 mV. This value grows up to 1200 mV for sulphate doped catalysts. The modification of the work function is probably due to the charge transfer from the zirconium to an oxygen species, responsible for the increase of Lewis acidity. The catalysts prepared with hydrolysis ratio of H = 4 exhibit higher activities in the isopropanol dehydration reaction than those with H = 2 in the temperature range 373 K–423 K.     

Kinetic parameters for thermal decomposition of microcrystalline,vegetal, and bacterial cellulose

Cellulose can be obtained from innumerable sources such as cotton, trees, sugar cane bagasse, wood, bacteria, and others. The bacterial cellulose (BC) produced by the Gram-negative acetic-acid bacterium Acetobacter xylinum has several unique properties. This BC is produced as highly hydrated membranes free of lignin and hemicelluloses and has a higher molecular weight and higher crystallinity. Here, the thermal behavior of BC, was compared with those of microcrystalline (MMC) and vegetal cellulose (VC). The kinetic parameters for the thermal decomposition step of the celluloses were determined by the Capela-Ribeiro non-linear isoconversional method. From data for the TG curves in nitrogen atmosphere and at heating rates of 5, 10, and 20 °C/min, the E _α and B _α terms could be determined and consequently the pre-exponential factor A _α as well as the kinetic model g(α). The pyrolysis of celluloses followed kinetic model g(a) = [ - ln(1 - a)]^{1 \mathord}

Preparation of nonspherical particles via dual-seeded dispersion polymerization in the presence of saturated hydrocarbon droplets

In this study, the effect of various polymerization conditions on the shape of the particles produced by dual-seeded dispersion polymerization of a second monomer with polystyrene (PS) and poly(methyl methacrylate) (PMMA) seed particles in the presence of saturated hydrocarbon droplets in a polar media was discussed. It was observed that with changing the affinity between the hydrocarbon and PS seed particles, second monomer type, polarity, and alcohol type of the medium nonspherical particles with a variety of shapes can be produced. Furthermore, we suggested that the presence of PMMA seed particles in the medium affects the distribution of the second polymer domains on the surface of the PS seed particles in addition to the absorbed amount of the hydrocarbon by PS particles and second polymer domains and the distribution of the hydrocarbon between them. Moreover, the experimental results showed that almond shell-like PS particles can be prepared under certain conditions.     

Synthesis and Structural Characterization and Thermal Properties of a Novel Aza‐aromatic Base Adduct of Cadmium Thenoyltrifluoroacetonate: A precursor for Pure Phase Nano‐sized Cadmium(II) Oxide

A novel aza‐aromatic base adduct of cadmium(II) thenoyltrifluoroacetonate, [Cd(phen)(ttfa)₂] ( 1 ), (phen = 1, 10‐phenanthroline; ttfa = thenoyltrifluoroacetonate) was synthesized and characterized by elemental analysis, IR, ¹H NMR, and ¹³C NMR spectroscopy, thermal analysis as well as X‐ray crystallography. The single‐crystal structure of this complex shows that the coordination number of the Cd²⁺ ions are six with two nitrogen donor atoms from aza‐aromatic base ligands and four oxygen donors from two thenoyltrifluoroacetonate ligands. The supramolecular features in these complexes are directed by weak directional intermolecular interactions. The structure of the title complex was optimized by density functional theory calculations. Calculated structural parameters and IR spectra for the title complex are in agreement with the crystal structure. The CdO nanoparticles were obtained by thermolysis of 1 at 180 °C with oleic acid as a surfactant. The average size of the nanoparticles was estimated by the Scherrer equation with the diameter about 45 nm. The morphology and size of the prepared CdO samples were further observed using SEM.     

Theoretical study on the mechanism and kinetics of atmospheric reactions NH2OH + OOH and NH2CH3 + OOH

Mechanism and kinetics of NH₂OH + OOH and NH₂CH₃ + OOH reactions were studied at the B3LYP and M062X levels of theory using the 6-311++G(3df, 3pd) basis set. The NH₂OH + OOH and NH₂CH₃ + OOH reactions proceed through different paths which lead to different products. Transition state structure and activation energy of each path were calculated. The calculated activation energies of hydrogen abstraction reactions were smaller than 25 kcal/mol and of substitution reactions are in the range of 50–70 kcal/mol. The rate constants were calculated using transition state theory (TST) modified for tunneling effect at 273–2000 K.