A series of dicarbamates have been synthesized by addition of diols to isocyanates. These products were characterized by NMR, IR, and HRMS analyses. Substituent effects on the barrier to rotation around N-CO bond were investigated using variable temperature 1H NMR spectroscopy.
H. Maouati, I. Chniti, M.A.K. Sanhoury, D. Merlet, I. Chehidi
Dicarbamates, diols, isocyanates, barrier to rotation, variable temperature 1H NMR
Pages 13-19
Kinetic studies for the reactions of N1-methyl-4-nitrobenzofurazanium tetrafluoroborate 1a with a series of 4-X-substituted anilines 2a-d (X = OH, OMe, Me and H) have been carried out in MeCN at 20 °C. The derived second-order rate constants (k1) have been combined with the pKa values of the conjugate acids of the anilines 2a-d to calculate the Brönsted parameters βnuc according to the linear free-energy relationship log k1 vs. pKa. The large Brönsted βnuc of 1.40 obtained suggest that the reactions proceed trough a single electron transfer (SET) mechanism. On the other hand, the finding of satisfactory correlation between the log k1 of the reactions and the oxidation potentials (Eo ) of anilines 2a-d supports this mechanism.
S. Ben Salah, R. Goumont, T. Boubaker
Kinetics, Linear Free Energy Relationships, Substituent Effects, SET Mechanism
Pages 20-25
In this work, the effect of Co substitution in the structural and magnetic properties has been investigated in Ni-Cu-Zn ferrites Ni0.4-xCu0.2Zn0.4CoxFe2O4, Ni0.4Cu0.2Zn0.4-xCoxFe2O4 (x=0, 0.2, 0.4) and Ni0.4Cu0.2-xZn0.4CoxFe2O4 (x=0, 0.1, 0.2). Nanoparticles of ferrites were obtained by hydrothermal method with stirring. A single phase from Ni-Cu-Zn ferrites with cubic spinel structure was formed for all the powders. The lattice parameter has been found to decrease with increasing Co content for all the samples, and this variation in the spinel unit cell is attributed to the difference in the ionic radius of Ni2+, Cu2+, Zn2+ and Co2+ ions. The results show an improvement in magnetic properties by substitution with cobalt, especially for the samples Ni0.4Cu0.2-xZn0.4CoxFe2O4 and Ni0.4-xCu0.2Zn0.4CoxFe2O4 with x=0.2. The saturation magnetization (Ms) of samples increases with the increase of crystallite size after sintering to reach the value of 81.68 Am2 kg-1 . However, the Curie temperature decreased with increasing Co content for the spinel ferrite Ni0.4-xCu0.2Zn0.4CoxFe2O4 and does not change for Ni0.4Cu0.2-xZn0.4CoxFe2O4.
F. Saida, H. Harzali, A. Marzouki, A. Mgaidi, A. Megriche
Spinel Ni-Cu-Zn ferrites, hydrothermal method, cobalt substitution, magnetic properties.
Pages 26-31
In the present study, Anodic oxidation (AO) as an Advanced Oxidation Process (AOP), was applied to degrade and mineralize a synthetic solution of a textile dye, Bromothymol Blue (BTB) on a Boron Doped Diamond (BDD) anode. An industrial discharge, sampled from a Tunisian textile industry containing BTB, was then treated, at the same operating conditions by AO. The effect of key parameters such as current density, reaction medium pH, treatment time, bubbling and cathode nature was investigated for the synthetic BTB solution. Discoloration yield was optimal and it reached 99% after 60 min of BTB treatment at pH 3, using a carbon felt as a cathode, operating at 60 mA cm-2 as current density and maintaining bubbling during the electrolysis. BTB mineralization was investigated under these optimal conditions by monitoring the discoloration, the Chemical Oxygen Demand (COD) and the Total Organic Carbon TOC) during 360 min of treatment, recording 100% of discoloration, 67% of COD abatement and 59% of TOC abatement. Thereupon the optimization of BTB synthetic dye solution, AO method was applied to oxidize an industrial textile effluent. Results found after 360 min of treatment at the same optimal conditions showed almost 94% of discoloration, 59% and 52% of COD and TOC removal respectively. The energy consumption per unit COD mass (ECCOD) of the AO was also calculated for the treatment of both BTB synthetic solution and the Tunisian textile effluent. 0.7 kWh (g COD)-1 and 0.91 kWh (g COD)-1 were found respectively after 360 min of treatment.
M. Maamar, N. Bellakhal
Bromothymol Blue, Advanced Oxidation Process, Anodic Oxidation, Boren Doped Diamond anode, Textile Effluent
Pages 32-42
We investigated the electrochemical behavior of S235JR steel in chloride media. The results of studying the effect of chloride concentration were reported and compared to those obtained for ordinary carbon steel (OS). Potentiodynamic polarization and cyclic voltammetry techniques were employed. For S235JR steel, it was revealed that the corrosion rate increased at higher chloride concentration and a first order kinetics was obtained. The pitting potential varied linearly with the logarithm of chloride concentration and the slope value was 110.9 mV/decade. In comparison with the ordinary carbon steel corrosion behavior, S235JR steel showed generally a better general corrosion resistance in chloride media. This was reflected by a lower value of corrosion current density equal to 8.6 mA cm-2 compared to OS (28.3 mA cm-2). The pitting potential determined for S235JR steel (-336 mV/SCE) was more positive than the one of OS (-365 mV/SCE) highlighting that S235JR steel is less subjected to pitting corrosion.
K. Nasr, M. Fedel, F. Deflorian, N. Bellakhal, N. Souissi
S235JR steel, chloride, pitting, polarization, voltammetry
Pages 43-51
This work presents some results of a characterization by X-ray diffraction (XRD), infrared spectroscopy (IR), Scanning Electronic Microscopy (SEM), Thermo gravimetric analysis (TGA) and differential thermic analysis (DTA) of two samples of clay minerals collected from Téra and Boubon in the valley of the Niger River. The results reveal that these samples contain a significant amount of kaolinite ranging from 60.99 to 61.61 %. We note also, the presence of Illite at low quantities.
M.A. Maman, A. Rabani, F. Habbachi, F. Menai, A. Abdoulaye, A. M’nif
clay minerals, kaolinite, XRD, IR, SEM
Pages 52-58
Mg1.8Al0.2Ni alloys were synthesized by mechanical alloying (MA) with different ball-milling duration. The structure and thermal behavior were determined by X-ray diffraction and differential scanning calorimetry. The lattice parameters as well as the lattice volumes, the weight contents and the crystallite sizes of the existing phases were determined by XRD patterns refinement based on the Rietveld method. The results show that Mg2Ni phase was obtained after 8 h of milling. The variation of the ball-milling duration from 8 to 48 h leads to the formation of nanomaterials with an average grain size of 9 nm. Thermal stability study revealed three exothermic peaks for the alloys obtained after 6 and 7 h of milling and four exothermic peaks for higher duration of milling. The first, second and third crystallization reactions for Mg1.8Al0.2Ni obtained after 6 and 7 h of milling take place at 100-200°C, 200-300°C and 400-500°C for heating rate of 20°C.min-1. So, by optimizing the milling and annealing conditions, we were able to obtain the Mg1.8Al0.2Ni nanocrystalline phase after 8 h of mechanical alloying at 250 rpm, 6 h of mechanical alloying at 250 rpm and annealing at 500°C or 7 h of mechanical alloying at 250 rpm and annealing at 225°C.
S. Ben Aissa, M. Abdellaoui
Pages 70-75
An efficient metalation-functionalization of diethylmethylphosphonate quinolines, at low-temperature, with suitable electrophiles in the presence of n-BuLi in THF, is described herein. It constitutes a general method for the synthesis of halogenophosphonoquinolines and vinylquinolines.
N. Jelaiel, T. Saïed, M.L. Efrit
methylphosphonate, quinoline, halogenophosphonoquinoline, vinylquinoline
Pages 121-126
Rss feed of the articles