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191.
The reaction of [R-(R,R)]-(+)589-[(η5-C5H5){1,2-C6H4(PMePh)2}Fe(NCMe)]PF6 with (±)-AsHMePh in boiling methanol yields crystalline [R-[(R)-(R,R)]-(+)589)-[(η5-C5H5){1,2-C6H4(PMePh)2}Fe(AsHMePH)PF6, optically pure, in ca. 90% yield, in a typical second-order asymmetric transformation. This complex contains the first resolved secondary arsine. Deprotonation of the secondary arsine complex with KOBut at −65°C gives the diastereomerically pure tertiary arsenido-iron complex [R-[(R),(R,R)]]-[((η5-C5H5){1,2-C6H4(PMePh)2}FeAsMePh] · thf, from which optically pure [R-[(S),(R,R)]]-(+)589-[(η5-C5H5){1,2-C6H4(PMePh)2}Fe(AsEtMePh)PF6 is obtained by reaction with iodoethane. Cyanide displaces (R)-(−)589-ethylmethylphenylarsine from the iron complex, thereby effecting the asymmetric synthesis of a tertiary arsine, chiral at arsenic, from (±)-methylphenylarsine and an optically active transition metal auxiliary. 相似文献
192.
Essam S. Zakaria Ismail M. Ali Hisham F. Aly 《Journal of colloid and interface science》2009,338(2):346-352
Magnesium titano-antimonate (MgTi5Sb2O16·12.5H2O) and cerium titano-antimonate (Ce2.7Ti5Sb2O19·15.0H2O) were synthesized as new cation exchangers using the in situ precipitation technique. Physico-chemical investigations showed different behaviors for the obtained materials. The materials have significant stability at high acid concentration and temperature. The ion exchange capacity for Cs+ in the presence of different alcoholic solvents was found to increase and generally obey the order C2H5OH > CH3OH > H2O. Diffusion coefficients (Di) and thermodynamic parameters of Cs+ exchange in both magnesium and cerium titano-antimonates in aqueous and alcoholic solutions were calculated. The swelling ratios of the materials were predicted by applying modified calculations at constant values of Di. The results showed insignificant swelling behavior in the presence of organic solvents. 相似文献
193.
Dr. Mukund G. Mali Hyun Yoon Hayong Kim Dr. Bhavana Joshi Dr. Salem S. Al‐Deyab Prof. Sam S. Yoon 《Chemphyschem》2015,16(16):3450-3457
We fabricated films of cubic indium oxide (In2O3) by chemical bath deposition (CBD) for solar water splitting. The fabricated films were characterized by X‐ray diffraction analysis, Raman scattering, X‐ray photoelectron spectroscopy, and scanning electron microscopy, and the three‐dimensional microstructure of the In2O3 cubes was elucidated. The CBD deposition time was varied, to study its effect on the growth of the In2O3 microcubes. The optimal deposition time was determined to be 24 h, and the corresponding film exhibited a photocurrent density of 0.55 mA cm?2. Finally, the film stability was tested by illuminating the films with light from an AM 1.5 filter with an intensity of 100 mW cm?2. 相似文献
194.
Feten Béji Sonia Taktouk Jihène Ben Kraïem Salem S. Al‐Deyab Hassen Amri 《Journal of heterocyclic chemistry》2015,52(5):1576-1579
We present herein an efficient and rapid method for the synthesis of N,1‐dialkyl‐4‐(2‐hydroxyethyl)‐5‐oxopyrrolidine‐3‐carboxamides based on the conversion of γ‐lactone to γ‐lactam via the conjugate addition of primary amines to an ethyl α‐functionalized acrylate followed by intramolecular cyclization. 相似文献
195.
Validated green high‐performance liquid chromatographic methods for the determination of coformulated pharmaceuticals: A comparison with reported conventional methods 下载免费PDF全文
Eman S. Elzanfaly Maha A. Hegazy Samah S. Saad Maissa Y. Salem Laila E. Abd El Fattah 《Journal of separation science》2015,38(5):757-763
The introduction of sustainable development concepts to analytical laboratories has recently gained interest, however, most conventional high‐performance liquid chromatography methods do not consider either the effect of the used chemicals or the amount of produced waste on the environment. The aim of this work was to prove that conventional methods can be replaced by greener ones with the same analytical parameters. The suggested methods were designed so that they neither use nor produce harmful chemicals and produce minimum waste to be used in routine analysis without harming the environment. This was achieved by using green mobile phases and short run times. Four mixtures were chosen as models for this study; clidinium bromide/chlordiazepoxide hydrochloride, phenobarbitone/pipenzolate bromide, mebeverine hydrochloride/sulpiride, and chlorphenoxamine hydrochloride/caffeine/8‐chlorotheophylline either in their bulk powder or in their dosage forms. The methods were validated with respect to linearity, precision, accuracy, system suitability, and robustness. The developed methods were compared to the reported conventional high‐performance liquid chromatography methods regarding their greenness profile. The suggested methods were found to be greener and more time‐ and solvent‐saving than the reported ones; hence they can be used for routine analysis of the studied mixtures without harming the environment. 相似文献
196.
Limin Zhou Yuyan Jia Juan Peng Zhirong Liu Essam Al-Zaini 《Journal of Radioanalytical and Nuclear Chemistry》2014,302(1):331-340
The triphosphate-crosslinked magnetic chitosan resins (TPP-MCR) with a diameter range of 200–350 nm were synthesized for the adsorption of U(VI) and Th(IV) ions from aqueous solutions. The adsorption experiments were conducted in both mono-component systems with pure actinide solution and bi-component systems with different U/Th mass ratios. The maximum adsorption capacities in mono-component systems determined by Langmuir model were 169.5 and 146.8 mg g?1 for U(VI) and Th(IV), respectively. In bi-component systems, U(VI) and Th(IV) adsorption capacities were reduced significantly, and the combined sorption capacities were substantially lower (almost halved) compared to those obtained by the addition of sorption capacities using mono-component solutions, indicating that U(VI) and Th(IV) compete for the same sorption sites. Adsorption–desorption experiments for five cycles illustrated the feasibility of the repeated use of TPP-MCR for the adsorption of U(VI) and Th(IV) ions. 相似文献
197.
Ammonium metavanadate is used to determine adrenaline, noradrenaline, isopropylnoradrenaline and methyldopa by titrimetric and photometric procedures. Oxidation of these catecholamines produces aminochrome derivatives which can be measured spectrophotometrically at 485 nm. Beer's law is obeyed over the ranges 0.09-0.90 mg for adrenaline, 0.07-0.65 mg for noradrenaline, 0.07-0.75 mg for isopropylnoradrenaline and 0.10-0.95 mg for methyldopa. 相似文献
198.
The geometry and electronic structure of the parent formaldehyde hydrazone and some ethylcyanoacetate phenylhydrazones (ECPHs) are studied at the semiempirical level of MO theory using the AM1 method. The effect of substitution on the geometry of the hydrazone moiety is investigated. The optimized geometry of formaldehyde hydrazone is nonplanar while in the ECPHs the planarity of the hydrazone group and its coplanarity with the phenyl ring increase in the direction of the electron-attracting ability of the para substituent. This has been attributed to an increase in the p– conjugation between the lone pair of electrons on the amine nitrogen and the phenyl ring. Variations of ionization potentials and bond orders with the Hammett constant,
p
, are examined and straight-line relationships are obtained. The results are correlated with the observed variations in the experimentally measured electrical conductivities of the studied compounds. 相似文献
199.
A comparative spectrophotometric study of the reaction of some substituted phenylazo-3-hydroxy-2-naphthoic acid derivatives with trivalent yttrium, lanthanum, praseodymium, neodymium, samarium, gadolinium, and erbium ions has shown that 1:1 and 1:2 complexes are formed at pH 7–8. Applications of these chelating agents for direct spectrophotometric determination of the lanthanons under investigation and also as indicators for spectrophotometric titration with EDTA were reported. Interference of various cations and anions in this method was also studied. Beer's law was obeyed for metal ions of up to 5–10 ppm. 相似文献
200.
Salem MY El-Zanfaly ES El-Tarras MF El-Bardicy MG 《Analytical and bioanalytical chemistry》2003,375(2):211-216
This work is concerned with the simultaneous determination of domperidone maleate (DOM) and cinnarizine (CINN) in a binary mixture form, without previous separation, by two different techniques. The first method is the application of derivative spectrophotometry where the linearity range and percentage recoveries for DOM and CINN were 2.5-30 micro g mL(-1), 5-25 micro g mL(-1) and 100.06+/-1.157, 99.93+/-1.377, respectively. The second method depends on the application of partial least squares (PLS) and principle component regression (PCR) models. A training set consisting of 10 mixtures containing 5-20 micro g mL(-1) for each component was used for the construction of the PCR and PLS models. These models were used after their validation for the prediction of the concentration of DOM and CINN in their mixtures. The proposed procedures were successfully applied for the simultaneous determination of both drugs in laboratory prepared mixtures and in commercial tablet preparations. The validity of the proposed methods was assessed by applying the standard addition technique where the percentage recovery of the added standard was found to be 99.98+/-0.297 and 99.84+/-0.700 for DOM and CINN, respectively, using the derivative spectrophotometric method and 100.29+/-0.398 and 100.11+/-0.363 for DOM and CINN, respectively, using the PLS and PCR methods.The proposed procedures are rapid, simple, require no preliminary separation steps and can be used for routine analysis of both drugs in quality control laboratories. 相似文献