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131.
O. E. Sherif 《Monatshefte für Chemie / Chemical Monthly》1997,128(10):981-990
Summary The electronic absorption spectra of some substituted diarylformazans in organic solvents of varying polarities are studied. The absorption bands are assigned to the corresponding electronic transitions in the molecules. The solvent effects on the intramolecular charge transfer bands are discussed using various solvent parameters. The charge transfer nature of the bands was also confirmed by the solvent effects on the absorption spectra of some formazans. Molecular orbital calculations using MNDO-PM3 were performed and indicate atrans configuration as the favoured geometry.
Lösungsmitteleinflüsse auf die Absorptionsspektren einiger substituierter Diarylformazane
Zusammenfassung Die Absorptionsspektren einiger substituierter Diarylformazane werden in organischen Lösungsmitteln unterschiedlicher Polarität untersucht. Die Absorptionsbanden werden den entsprechenden Elekronenübergängen in den Molekülen zugeordnet. Die Lösungsmitteleffekte auf die intramolekularencharge-transfer-Banden werden unter Verwendung verschiedener Lösungsmittelparameter diskutiert. Diecharge-transfer-Natur der Banden wurde durch den Einfluß der Lösungsmittel auf die Absorptionsspektren einiger Formazane bestätigt. MO-Rechnungen (MNDO-PM3) wurden durchgeführt und bestätigen einetrans-Konfiguration als bevorzugte Geometrie.相似文献
132.
The squarate complexes of Eu3+, Tb3+ and Tm3+ in aqueous solutions of 0.05M, 0.075M and 0.1M ionic strength are studied using the solvent extraction method. Effects of
changes in the ionic strength on the stability constants of the complexes formed are discussed. 相似文献
133.
H. F. Aly S. M. Khalifa R. M. Mahfooz M. K. Sherif 《Journal of Radioanalytical and Nuclear Chemistry》1981,63(2):295-300
The effect of temperature on the extraction of Co2+, Zn2+, Cd1+ and Hg2+ by salicylaldoxime diluted with carbon tetrachloride was investigated radiometrically. It is found that the extraction constants
at 25°C increase linearly with l/r, where r is the effective coordination radius of the metal cation. The thermodynamic data
calculated from the effect of temperature on the extraction showed that, 1) the extraction process is endothermic, 2) the
dehydration of the metal cation in the extraction process is the predominating factor in determining the enthalpy variation
and 3) the entropy variation is a contribution of the degree of order caused by the hydration of the proton and the highly
ordered chelate structure of the extracted species. 相似文献
134.
M. K. Sherif R. M. Awadallah A. E. Mohamed 《Journal of Radioanalytical and Nuclear Chemistry》1979,53(1-2):145-153
Neutron activation analysis, NAA, a high resolution Ge(Li) gamma ray spectrometer was used to determine the concentration
of Al, As, Au, Br, Ca, Cd, Co, Cr, Cu, Fe, La, Mn, Mo, Sb, Se, W, and Zn in Cumin, coriander, carrots, and Daucus carrota
(Umbelliferae Family), alfalfa, Kidney bean, Phaseolus sativus, Phaseolus vulgaris, bean, lenses, and fenugreek (Legumirosae
Family). Multielement determination technique on destructive and nondestructive samples was followed. This method is simple,
precise and sensitive to 17 trace elements. 相似文献
135.
Summary Phenylsulfonylacetophenones1 react with a mixture of elemental sulfur and malononitrile to yield the corresponding 2-amino-4-aryl-5-phenylsulfonylthiophene-3-carbonitriles2. Compound2a could be annelated to the corresponding thieno[2,3-d]pyrimidine and thieno[2,3-c]-pyrazole derivatives3 and5 upon reaction with nitrogen nucleophiles (cyanamide and hydroxylamine hydrochloride), respectively. The applicability and synthetic potency of5 to develop a facile convenient route to the polyfunctionally substituted thieno[2,3:3,4]pyrazolo[1,5-a]pyrimidines8, 14, 17, 20, and21 is reported. Chemical and spectroscopic evidences for the structures of the new compounds are presented.
Synthesen mit heterocyclischen -Enaminonitrilen: Ein rascher synthetischer Zugang zu polyfunktionell substituierten 5-Phenylsulfonylthiophenen und ihren kondensierten Derivaten
Zusammenfassung Die Phenylsulfonylacetophenone1 reagieren mit einem Gemisch aus elementarem Schwefel und Malonsäurenitril zu den entsprechenden 2-Amino-4-aryl-5-phenylsulfonylthiophen-3-carbonitrilen2. Durch Umsetzung mit Stickstoffnucleophilen wie Cyanamid und Hydroxylaminhydrochlorid konnten aus Verbindung2a die entsprechenden Thieno[2,3-d]pyrimidin- und Thieno[2,3-c]pyrazolderivate erhalten werden. Das synthetische Potential und die Anwendbarkeit von5 zur Synthese polyfunktionell substituierter Thieno[2,3:3,4]pyrazolo[1,5-a]pyrimidine (8,14,17,20,21) werden beschrieben. Die Strukturen der neuen Verbindungen wurden durch chemische und spektroskopische Methoden abgesichert.相似文献
136.
Issa Yousry M. El-Ansary Aida L. Sherif Omyma E. El-Ajily Marei M. 《Transition Metal Chemistry》1997,22(5):441-446
Transition metal chelates of the title compounds have been prepared and characterized by elemental analyses, i.r., 1H-n.m.r., electronic spectra, thermogravimetric analysis, conductometric and magnetic measurements. Chelates of general formulae MLjX · nH2O for 1:1 (M:L), where X=OH– or Cl–, j=1 or 2, n=1– 4 and M=VO2+, Cr3+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+ and Zn2+ ions or ML2 for 1:2 (M:L) Ni-(1a), ML2·2H2O where M=Co2+, Ni2+ and Cu2+ or M2LjX·nH2O for 2:1 (M:L) Cr3+, Fe2+, Ni2+ and Cu2+, L=Ligand, have been prepared. I.r. and 1H-n.m.r. spectra indicate that the aldehydic group in position six and the hydroxylic group in position seven are involved in chelation in the 1:1 and 1:2 (M:L) chelates, whereas for 2:1 (M:L) chelates with (1c), the interaction of the metal ion takes place through CHO, OH, CO2H and NN groups. Tetrahedral, octahedral and square planar geometries are proposed for the chelates based on their electronic spectra and magnetic moments. 相似文献
137.
The automotive industry is one of the most important manufacturing sectors in the world due to its economic impact and technological complexities. While supply chain performance can have a dramatic impact on the automotive industry, there are multiple, often conflicting objectives that typically are used to optimize performance. We model the trade-off between cost and service level, and present a bi-criteria heuristic optimization methodology for a two-stage, integrated automotive supply chain. Our problem contains sequence-dependent setups on parallel machines and auxiliary resource assignments. We minimize the total cost of setups, inventory holding, and transportation costs, and the maximum percentage of outsourced parts per customer, simultaneously. We use our proposed method to solve a set of problem instances that are based on industrial data. Our proposed method generates approximate Pareto (efficient) solutions in a timely manner for use in practice. 相似文献
138.
Sadeek Atia Sadeek Sherif Mohamed Abd El‐Hamid Amira A. Mohamed Wael A. Zordok Hassan A. El‐Sayed 《应用有机金属化学》2019,33(5)
The mixed‐ligand Mn(II), Fe(III), Ni(II), Cu(II), Zn(II) and Zr(IV) complexes of meloxicam (H2mel) and 2,2′‐bipyridine (Bipy) were prepared and characterized. For all complexes, the analytical and spectroscopic results revealed that H2mel acts in a monobasic bidentate manner through the oxygen of the amide and nitrogen of the thiazole groups, whereas Bipy coordinates through the two nitrogen atoms with slightly distorted octahedral geometry. Thermodynamic parameters (E, ΔS*, ΔH* and ΔG*) were calculated using Coats–Redfern and Horowitz–Metzger methods. The geometries of H2mel and the complexes were carefully studied using density functional theory to predict the properties of materials performed using the hybrid density functional method B3LYP. All studied complexes are soft with respect to H2mel where η varies from 0.096 for Zn(II) complex to 0.067 for Fe(III) complex and σ varies from 10.42 to 14.93 eV, while η and σ for H2mel are 0.14 and 7.14 eV, respectively. The antibacterial activities of the ligands and metal complexes were investigated and the data show that the complexes are active against some bacterial species compared with H2mel. 相似文献
139.
In this study, we discuss the utility of bis(cyanoacetamides) as versatile precursors to the piperazine-mediated synthesis of a wide spectrum of bis(thieno[2,3-b]pyridine) derivatives, linked to aliphatic spacers via thioethers. The proposed tandem protocol involved the reaction of bis(cyanoacetamides) with two equivalents of the appropriate cinnamonitriles in dioxane in the presence of six equivalents of piperazine at reflux for 4 hours. Then, two equivalents of the appropriate halogen-containing reagents were added and the reaction was heated at reflux for further 3 hours. The bis(thieno[2,3-b]pyridines) were taken as a key intermediates to new bis(4-oxopyrido[3′,2′:4,5]thieno[3,2-d]pyrimidines). The above derivatives were reacted with the appropriate hydrazonyl chloride derivatives in dioxane in the presence of triethylamine to yield the corresponding bis([1,2,4]triazoles) with a related fused pyridothienopyrimidine moiety. The new structures were elucidated by IR, NMR spectral data, as well as elemental analyses. 相似文献
140.
Sherif J. Kaldas Eva Kran Dr. Christian Mück-Lichtenfeld Prof. Dr. Andrei K. Yudin Prof. Dr. Armido Studer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(7):1501-1505
We report the cycloaddition between vinyl aziridines and arynes. Depending on the reaction conditions and the choice of the aryne precursor, the aziridinium intermediate can be trapped through two distinct mechanistic pathways. The first one proceeds through a formal [5+2] cycloaddition to furnish valuable multi-substituted benzazepines. In the second pathway, the aziridinium is intercepted by a fluoride ion to afford allylic fluorides in good yields. Both reactions proceed stereospecifically and furnish enantiopure benzazepines and allylic fluorides. 相似文献