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1.
Kinetics and Mechanism of Dehydrochlorination of 3‐Chloro‐1,5‐diarylformazans and Their Mass Spectra
In aqueous dioxane containing triethylamine the title 3‐chloroformazans 1 are converted into the corresponding 1,4‐bis(arylazo)‐3,6‐diaryl‐1,2,4,5‐tetrazines 3 via head‐to‐tail dimerization of the intitially formed 1,3‐dipolar ions 2. The kinetics of triethylamine‐catalyzed dehydrochlorination of 1 in 70% dioxane at 27°C and ionic strength of 0.1 were studied. The rate data were linearly correlated with enhanced Hammett substituent constants σx? and an overall ρ value of 0.2 was determined for the variation of the N‐aryl substituent. These results were interpreted in terms of a two‐step mechanism. Also, the mechanisms of the unimolecular fragmentation of 1 and 3 in the mass spectrometer are discussed. 相似文献
2.
Zerrouki Abdelkhalek Abrigach Farid Taleb Mustapha El Kadiri Sghir 《Research on Chemical Intermediates》2020,46(2):1453-1467
Research on Chemical Intermediates - A class of novel multi-tripodal ligands has been prepared via condensation reaction between pyrazole or triazole moieties and... 相似文献
3.
Abdeslam El Assyry Bouziane Benali Abdelkhalek Boucetta Denise Mondieig 《Research on Chemical Intermediates》2014,40(3):1043-1052
In this study, heat energy, atomic charges and dipole moments permit qualitative predictions about the substituent effects by a chlorine or methyl group on the benzodiazepine properties in the ground state. AM1 and MNDO semi-empirical methods of calculation are used to obtain information on the structural and energy properties for some benzodiazepine derivatives. 相似文献
4.
M.M. Abdelkhalek 《Communications in Nonlinear Science & Numerical Simulation》2009,14(5):2091-2102
Numerical results are presented for heat and mass transfer effect on hydromagnetic flow of a moving permeable vertical surface. An analysis is performed to study the momentum, heat and mass transfer characteristics of MHD natural convection flow over a moving permeable surface. The surface is maintained at linear temperature and concentration variations. The non-linear coupled boundary layer equations were transformed and the resulting ordinary differential equations were solved by perturbation technique [Aziz A, Na TY. Perturbation methods in heat transfer. Berlin: Springer-Verlag; 1984. p. 1–184; Kennet Cramer R, Shih-I Pai. Magneto fluid dynamics for engineers and applied physicists 1973;166–7]. The solution is found to be dependent on several governing parameter, including the magnetic field strength parameter, Prandtl number, Schmidt number, buoyancy ratio and suction/blowing parameter, a parametric study of all the governing parameters is carried out and representative results are illustrated to reveal a typical tendency of the solutions. Numerical results for the dimensionless velocity profiles, the temperature profiles, the concentration profiles, the local friction coefficient and the local Nusselt number are presented for various combinations of parameters. 相似文献
5.
Sonia Ben Abdelkhalek Nabil Kallel Sami Kallel Octavio Peña Mohamed Oumezzine 《Journal of magnetism and magnetic materials》2012
Critical behavior in the La0.6Sr0.4Mn0.8Fe0.1Cr0.1O3 ceramics was studied using magnetization methods. Results show that the paramagnetic–ferromagnetic transition is of second order. Based on the critical behavior analysis using the Banerjee criterion and the Kouvel–Fisher method, we find the critical exponents: β=0.395±0.010, γ=1.402±0.010, and δ=5.208±0.007, for which the magnetic interaction is satisfied within the three-dimensional Heisenberg model. Results indicate the presence of short-range interactions. The magnetic entropy change (−ΔSM) reached maximum values of 1.75, 1.45, 1.15, 0.8 and 0.43 J Kg−1 K−1 under a magnetic field variation of 5, 4, 3, 2 and 1 T, respectively. Nevertheless, these (−ΔSM) values are much low for any potential application at this moment. The nature of this phenomenon is discussed in relation to the characteristics of the magnetic phase transition and critical exponents. 相似文献
6.
New functionalized isoxazolines were effeciently and easily prepared from limonene. The procedure involves a peri‐ and regioselective 1,3‐dipolar cycloaddition of nitrile oxides on the monoterpene external double bond, followed by a highly chemoselective RuCl3‐NaIO4 oxidative cleavage of the internal one. All the newly prepared isoxazolyl‐ketoacids were fully characterized from their spectroscopic data. 相似文献
7.
Sonia Ben Abdelkhalek Sami Kallel Octavio Peña 《Journal of magnetism and magnetic materials》2010,322(21):3416-4067
The structural, magnetic and electrical properties of Cr and Fe simultaneously substituted in the perovskite La0.6Sr0.4Mn1−2xCrxFexO3 have been studied. The presence of Cr and Fe had no significant effect on the structural properties. Curie temperature and saturation magnetization decrease with increase in Cr and Fe contents. For x=0.20 and 0.25, a steep drop of zero field-cooled (ZFC) magnetization at low temperature signifies the formation of cluster- or spin-glass state. A weak hysteresis at low fields seems to be an indication of phase separation. All the resulting magnetization curves can be explained by a superposition of both ferromagnetic and antiferromagnetic components. All the samples are semiconducting throughout the temperature range studied. Resistivity can be described by the adiabatic small polaron hopping and the variable range hopping model. It was found that the transport mechanism is dominated by the VRH model with an increase of Mott localization energy, which explains the increase of resistivity. 相似文献
8.
Mustapha Aitali My Youssef Ait Itto Aisa Hasnaoui Abdelkhalek Riahi Abdellah Karim Santiago García‐Granda Angel Gutirrez‐Rodríguez 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(8):e315-e316
The novel title ruthenium(II) complex, [RuCl(C10H14)(C10H10N3OS)], was synthesized from the reaction of 1,2,4‐triazepine, a new class of bidentate ligands, with [Ru(p‐cymene)Cl2]2. The 1,2,4‐triazepine ligand is coordinated to the metal centre through the N‐4 and S atoms, forming a four‐membered chelate ring. This is the first structural example of a transition metal complex containing a 1,2,4‐triazepine ligand. 相似文献
9.
Hossni Ziyat My Youssef Ait Itto Mustapha Ait Ali Abdellah Karim Abdelkhalek Riahi Jean‐Claude Daran 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(2):o90-o93
The two new gem‐dihalogenocyclopropanes (1′S,3R)‐3‐(2′,2′‐dichloro‐1′‐methylcyclopropyl)‐6‐oxoheptanoic acid, C11H16Cl2O3, (2), and (1′S,3R)‐3‐(2′,2′‐dibromo‐1′‐methylcyclopropyl)‐6‐oxoheptanoic acid, C11H16Br2O3, (3), are isostructural. Both present two stereogenic centers at C1′ and C3. The absolute configuration was determined by X‐ray methods. The cyclopropyl rings are unsymmetrical, the shortest bond being distal with respect to the alkyl‐substituted C atom. 相似文献
10.
Manolis A. Fousteris Anna I. Koutsourea Sotiris S. Nikolaropoulos Abdelkhalek Riahi Jacques Muzart 《Journal of molecular catalysis. A, Chemical》2006,250(1-2):70-74
Various chromiumVI-catalyzed conditions have been tested to improve the oxidation of Δ5-steroids with t-BuOOH to their corresponding 5-en-7-ones. The use of PDC or the association of CrO3 with an amine as the catalyst and CH2Cl2 or PhCF3 as the solvent led usually to the best yields. A minor reaction pathway was the epoxidation of the double bond. 相似文献