Selective homogeneous liquid-liquid extraction and preconcentration of copper(II) into a micro droplet using a benzo-substituted macrocyclic diamide, and its determination by electrothermal atomic absorption spectrometry

A fast and reliable method was developed for the selective separation and preconcentration of Cu²⁺ ions using homogeneous liquid-liquid extraction using a novel benzo-substituted macrocyclic diamide, 5,6,7,8,9,10-hexahydro-2H-1,13,4,7,10-benzodioatriazacyclo-pentadecine-3,11(4 H,12 H)-dione, as a selective complexing agent. An aqueous solution of Zonyl FSA (FSA) was used as a phase-separation agent at pH 4.5. Electrothermal atomic absorption spectrometry was used for Cu²⁺ determination after preconcentration. The influences of pH, type and volume of the water-miscible organic solvent, concentration of FSA, concentration of the ligand and the effect of diverse ions were investigated. Factorial design and response surface methods were used for the optimization purposes. Under the optimum experimental conditions, 50 ng of Cu²⁺ in 5 mL aqueous sample could be extracted quantitatively into 76 µL of the sediment phase. The maximum preconcentration factor was 65. The calibration curve was linear in the concentration range 0.2 to 4.0 µg L^?1. The detection limit and relative standard deviation were 4 ng L^?1 and 4.6%, respectively. The method was successfully applied to the extraction and determination of Cu²⁺ in natural water samples.     

Spectrophotometric determination of aqueous acidity constants of three azo dyes

The two successive steps acidity constants of three azo dye derivatives D1–D3, were determined by a spectrophotometric method using 0.10 M KNO₃ as supporting electrolyte in water solvent. The electronic spectra of the compounds were recorded in the course of their pH-metric titration with a standard base solution. The protolytic equilibrium constants can be solved very satisfactorily from absorbance data, by combining the data obtained in the spectrometric determinations with graphic methods as the absorbance diagrams. An A-diagram shows the relative absorbance changes at two wavelengths as a function of the pH. For a one-step system, the absorbance at any wavelength must be proportional to the absorbance at any other wavelength, so an A-diagram for all wavelength combinations for such a system must be linear (rank, s=1). However, if a system is governed by two or more equilibria, the A-diagrams corresponding to multi-step titrations will change direction every time a new equilibrium becomes dominant in the system. Analysis of the each uniform sub-region can then be used in evaluating of the corresponding equilibrium. A-diagrams for all wavelength combinations suggest that these systems have the rank two(s=2). The results revealed that the K_a(1) and K_a(2) values of different azo dyes follow the order D3>D2>D1.      

A practical and versatile approach toward a one-pot synthesis of 2,3-disubstituted 4(3H)-quinazolinones

Abstract  

An effective one-pot three-component route to 4(3H)-quinazolinones from commercially available starting materials is reported. Thus, isatoic anhydride reacted with ammonium acetate or primary amines and aldehydes in the presence of iodine to produce the corresponding quinazolinone derivatives in moderate to good yields.     

The odd log-logistic Topp–Leone G family of distributions: heteroscedastic regression models and applications

We introduce a new class of distributions and provide a comprehensive treatment of its mathematical properties. The maximum likelihood method is discussed to estimate the parameters of the new model by means of Monte-Carlo simulation study. The heteroscedastic regression models with long-term survival are introduced to model data sets with the non homogeneity of the error variances in the presence of cured individuals. The potentiality of the proposed models is illustrated by means of four real data sets.     

One-pot and stereoselective synthesis of 2,3-dihydro-1,5-benzodiazepin-2-one with a phosphanylidene or phosphono-succinate substituent

The one-pot synthesis of 2,3-dihydro-1,5-benzodiazepins-2-one bearing phosphanylidene (ylide) or phosphono-succinate substituent is described. In this four-component reaction, benzodiazepine derived from condensation of o-phenylenediamine and diketene is trapped with the trialkyl phosphite-dialkyl acetylenedicarboxylate zwitterion. In the presence of H₂O, the ylide functional group is hydrolyzed to the corresponding phosphonate. The configuration of the products is selective and only one of the two possible rotamers or diastereomers is formed exclusively in high yield.     

Extension of primal-dual interior point algorithms to symmetric cones

 In this paper we show that the so-called commutative class of primal-dual interior point algorithms which were designed by Monteiro and Zhang for semidefinite programming extends word-for-word to optimization problems over all symmetric cones. The machinery of Euclidean Jordan algebras is used to carry out this extension. Unlike some non-commutative algorithms such as the XS+SX method, this class of extensions does not use concepts outside of the Euclidean Jordan algebras. In particular no assumption is made about representability of the underlying Jordan algebra. As a special case, we prove polynomial iteration complexities for variants of the short-, semi-long-, and long-step path-following algorithms using the Nesterov-Todd, XS, or SX directions. Received: April 2000 / Accepted: May 2002 Published online: March 28, 2003 RID="⋆" ID="⋆" Part of this research was conducted when the first author was a postdoctoral associate at Center for Computational Optimization at Columbia University. RID="⋆⋆" ID="⋆⋆" Research supported in part by the U.S. National Science Foundation grant CCR-9901991 and Office of Naval Research contract number N00014-96-1-0704.     

Catalytic effect of zinc oxide on the reduction of barium sulfate by methane

Reduction of barium sulfate by methane was investigated in this work. The thermogravimetric method was used to obtain kinetic parameters of the reaction in the temperature range of 900–975 °C at atmospheric pressure. The kinetics of the reaction has been studied both in the absence and presence of zinc oxide as a catalyst. The conversion–time data have been interpreted by using the grain model, and the effect of catalyst on the kinetic parameters has been elucidated. It was found that zinc oxide acted as fairly strong catalyst for the reaction, especially at higher temperatures. At about 975 °C the reaction rate constant was increased more than 7 times by using 2% of zinc oxide. This enhancement in the rate constant is valuable for industries.     

One‐Pot Synthesis of 4‐(Alkylamino)‐1‐(arylsulfonyl)‐3‐benzoyl‐1,5‐ dihydro‐5‐hydroxy‐5‐phenyl‐2H‐pyrrol‐2‐ones via a Multicomponent Reaction

An effective route to novel 4‐(alkylamino)‐1‐(arylsulfonyl)‐3‐benzoyl‐1,5‐dihydro‐5‐hydroxy‐5‐phenyl‐2H‐pyrrol‐2‐ones 10 is described (Scheme 2). This involves the reaction of an enamine, derived from the addition of a primary amine 5 to 1,4‐diphenylbut‐2‐yne‐1,4‐dione, with an arenesulfonyl isocyanate 7 . Some of these pyrrolones 10 exhibit a dynamic NMR behavior in solution because of restricted rotation around the C? N bond resulting from conjugation of the side‐chain N‐atom with the adjacent α,β‐unsaturated ketone group, and two rotamers are in equilibrium with each other in solution ( 10 ? 11 ; Scheme 3). The structures of the highly functionalized compounds 10 were corroborated spectroscopically (IR, ¹H‐ and ¹³C‐NMR, and EI‐MS), by elemental analyses, and, in the case of 10a , by X‐ray crystallography. A plausible mechanism for the reaction is proposed (Scheme 4).     

Acetylation of Alcohols Catalyzed by Dodeca-tungsto(molybdo)phosphoric acid

Summary. Acetylation of primary, secondary, and tertiary alcohols was carried out in some refluxing alkyl acetates and in two carboxylic acids with the participation of catalytic amounts of H₃PW₁₂O₄₀, H₃PMo₁₂O₄₀, and H₁₄P₅W₃₀O₁₁₀ with good yields and high stereo(regio)specificity under mild reaction condition. H₃PW₁₂O₄₀ and H₃PMo₁₂O₄₀ have also shown excellent reactivity in the formylation of 1-butanol with ethyl formate at room temperature and in short reaction times. Heteropolyacid catalysts could be separated after a simple work up and reused for several times.