O. Carboxyphenylhydrazoethylacetoacetate as an Analytical Reagent for the Determination of Cu(II) and Co(II) in Complex Materials

An extraction‐spectrophotometric method for the determination of trace amounts of copper and cobalt based on their extraction into n‐pentanol with 0. carboxyphenylhydrazoethylacetoacetate (O.CPHEAA) was per formed. Copper was extracted from pH 6.0 – 8.0 and ionic strength 0.5 M – KCl. The maximum absorption of the extracted Cu(II) ‐ O.CPHEAA complex (1:1 & 1:2 species) occurs at 415 nm. The proposed method succeeded in as saying a concentration of 3–63 μg per 10 mL of n‐pentanol (? = 1.25 × 10⁴L mol^?1 cm^?1). The method failed to ex tract cobalt ion into various organic sol vents over a pH range of 2–11. The suggested method is highly selective and sensitive according to a wide scheme of interference studied. Copper in some plant samples was accurately estimated using the suggested method. The obtained results and the results of the AAS method were consistent. The reproducibility test shows a relative standard deviation of 1%. Sandell sensitivity for A = 0.001 is 5 × 10^?3 μg cm^?2.     

Titanocene-catalyzed cascade cyclization of epoxypolyprenes: straightforward synthesis of terpenoids by free-radical chemistry

The titanocene-catalyzed cascade cyclization of epoxypolyenes, which are easily prepared from commercially available polyprenoids, has proven to be a useful procedure for the synthesis of C(10), C(15), C(20), and C(30) terpenoids, including monocyclic, bicyclic, and tricyclic natural products. Both theoretical and experimental evidence suggests that this cyclization takes place in a nonconcerted fashion via discrete carbon-centered radicals. Nevertheless, the termination step of the process seems to be subjected to a kind of water-dependent control, which is unusual in free-radical chemistry. The catalytic cycle is based on the use of the novel combination Me(3)SiCl/2,4,6-collidine to regenerate the titanocene catalyst. In practice this procedure has several advantages: it takes place at room temperature under mild conditions compatible with different functional groups, uses inexpensive reagents, and its end step can easily be controlled to give exocyclic double bonds by simply excluding water from the medium.     

Optimization of the extraction of paclitaxel from Taxus baccata L. by the use of microwave energy

A simple and rapid microwave-assisted extraction (MAE) procedure was developed and optimized for the extraction of paclitaxel (Taxol) from the needles of yew trees Taxus baccata L. grown in Iranian habitats. The samples, immersed in a methanol-water mixture, were irradiated with microwaves in a closed-vessel system. The method was evaluated using a factorial design approach based on parameters such as extraction time, temperature, methanol concentration in water (v/v), and the ratio of grams of sample to 10 mL of solvent. Statistical treatment of the results revealed that the selected parameters were all significant except the extraction time. Optimum conditions would be 1.5 g samples in 10 mL solvent (90% methanol), an extraction temperature of 95 degrees C, and an extraction time of 7 min. The extracts has been analyzed by reverse-phase high-performance liquid chromatography with UV detection (LC/UV) at 227 nm for quantification. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used for confirmation. The main advantage of the proposed MAE method versus conventional solvent extraction (CSE) are the considerable reductions in time (7 min versus 16 h) and in solvent consumption (20 mL versus 150 mL). The MAE procedure yielded extracts that could be analyzed directly without any preliminary clean-up or solvent exchange steps. Both extraction methods show RSDs lower than 10% and lead to comparable recoveries of paclitaxel (87-92%).     

Heteropolynuclear Sodium(I) Lead(II) Complex: Crystal and Molecular Structure of a Novel 3‐D Polymer, [(en)Pb(μ3‐ONO)2Na(μ3‐ONO)2Na(μ‐O2ClO2)Na]n

A novel 3D polymeric heteropolynuclear sodium(I) lead(II) complex containing different ligands, [NaPb(ClO₄)(en)(NO₂)₂] was synthesized and characterized by elemental analysis and IR, and ¹H‐, ¹³C‐, and ²⁰⁷Pb‐NMR spectroscopy. The single‐crystal X‐ray data of [NaPb(ClO₄)(en)(NO₂)₂]_n established that the complex is a three‐dimensional polymer, [(en)Pb(μ₃‐ONO)₂Na(μ₃‐ONO)₂Na(μ‐O₂ClO₂)Na]_n. The Pb and Na atoms have four‐ and eight‐coordinate geometry, respectively. The lone pair of electrons at the Pb^II atom is ‘stereochemically active’.     

Treated Rice Bran for Scavenging Cr(III) and Hg(II) from Acidic Solution

The purpose of this study was to examine the efficiency with which rice bran (treated or untreated) removes heavy metals, especially Cr(III) and Hg(II), from acidic solution. Sorption assays were done in shaken flasks in the presence of rice bran. Different experimental conditions such as pH, volume of solution, bran weight, particle size, exchange time and stirring time were improved. The efficiency of bran was studied before and after treatments. For treatment, solutions of acid, alkali and salt were used. The results show that after treating with 4 M sodium chloride solution, its efficiency in removal of Cr(III) and Hg(II) was improved. Kinetic measurements of chromium and mercury removal by bran have revealed that sorption equilibrium was obtained after 10 min of contact. Sorption experiments done with various granulometric fractions of rice bran have shown that this sorbent has the same efficiencies in meshes higher than 20. Further research is necessary in order to determine a mechanism for cations removal by the bran. It is mentioned that the process of making polished rice from brown rice discharges rice bran; therefore, it is very inexpensive, with a cost of 1/50 ? 1/40 of that of synthetic sorbent, and thus its use would significantly lower the cost of wastewater treatment.     

“Living” radical graft polymerization of styrene to styrene butadiene rubber (SBR) with 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO)

Well‐defined graft copolymers with styrene butadiene rubber (SBR) backbones and polystyrene branches were synthesized by living free radical polymerization (LFRP) techniques. Thus 1‐ benzoyl‐2‐phenyl‐2‐(2′,2′,6′,6′‐tetramethyl‐piperidinyl‐1′‐oxy)ethane (BZ‐TEMPO) was synthesized and hydrolyzed to the corresponding 1‐hydroxyl derivative. This functional nitroxyl compound was coupled with brominated SBR (SBR‐Br). The resulting macroinitiator (SBR‐TEMPO) for “living” free radical polymerization was then heated in the presence of styrene for the formation of the controlled graft copolymer. ¹H‐NMR and IR spectroscopy were used to investigate the structure of the polymers. Copyright © 2004 John Wiley & Sons, Ltd.     

Determination of percolation threshold electroactivity and phase behavior study on conducting blends of thermotropic polyesters and polyaniline

The new thermotropic polyester/polyaniline (PIn/PAni) blends have been prepared by solution blend of synthesized liquid crystalline poly[4,4′‐bis (ω‐alkoxy) biphenylisophthalate]s having four and six methylene units in spacer (PI4 and PI6) with PAni doped with camphorsolfonic acid (CSA). The percolation threshold electroactivity of prepared blend films has been determined by cyclic voltammetry. The effect of the PAni concentration, solvent nature and polyester structure on the electroactivity of the blends has been investigated. The extremely low percolation threshold of prepared PIn/PAni‐CSA blends from dimethylformamide (DMF) and m‐cresol solution was 3% weight of PAni‐CSA. The amount of conducting polymer necessary to retard the formation of the liquid crystalline (LC) phase is up to 45% by weight. Phase behavior studies by differential scanning calorimetry and polarizing microscopy show that blends with 45% of conducting polymer are both liquid crystal and conductive. The morphology of the blends has been investigated by scanning electron microscopy. Copyright © 2004 John Wiley & Sons, Ltd.     

Synthesis of New Dibenzosulfide and Dibenzosulfoxide Macrocyclic Compounds

Some new dibenzosulfo, dibenzosulfoxo macrocyclic diamides are synthesized.     

Trichloroisocyanuric acid as a novel oxidizing agent for the oxidation of 1,3,5-trisubstituted pyrazolines under both heterogeneous and solvent free conditions

Trichloroisocyanuric acid is used as an effective oxidizing agent for the oxidation of 1,3,5-trisubstituted pyrazolines to their corresponding pyrazoles under both heterogeneous and also solvent free conditions with good yields at room temperature.     

Conducting graft copolymers of poly(3‐methylthienyl methacrylate) with pyrrole and thiophene

A thiophene‐functionalized methacrylate monomer (3‐methylthienyl methacrylate) was synthesized via the esterification of 3‐thiophene methanol with methacryloyl chloride. The methacrylate monomer was polymerized by free‐radical polymerization in the presence of azobisisobutyronitrile as the initiator. Graft copolymers of poly(3‐methylthienyl methacrylate) (PMTM2) and polypyrrole and of PMTM2 and polythiophene were synthesized by constant‐potential electrolyses. p‐Toluene sulfonic acid, sodium dodecyl sulfate, and tetrabutylammonium tetrafluoroborate were used as the supporting electrolytes. PMTM2‐coated platinum electrodes were used as anodes in the polymerization of pyrrole and thiophene. Moreover, the oxidative polymerization of poly(3‐methylthienyl methacrylate) (PMTM1) was studied with FeCl₃ as the oxidant. The self‐polymerization of PMTM1 was also investigated by galvanostatic electrolysis both in dichloromethane and in propylene carbonate. The structures of PMTM1 and PMTM2 were investigated by several spectroscopic and thermal methods. The grafting process was elucidated with conductivity measurements, Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and scanning electron microscopy studies. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4131–4140, 2002