JOURNAL of the Tunisian Chemical Society

serving the Research, the Education and the Industry

Ultrasonic activation of Nozaki-Hiyama-Kichi reaction in the presence of phase transfer catalysis

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The addition of compounds organochromium with aldehydes originally described by Nozaki-Hiyama-Kishi has evolved to become a very powerful method leads to the formation of C-C bonds. We present a process that allows the coupling of aldehydes with organic halides under Ultrasonic irradiation and in the presence of phase transfer catalysis in a medium consisting of anhydrous CrCl2 and an amount of Mn in combination with trimethylsilane chloride (Me)3SiCl to finally produce secondary alcohols. Yields are increased through the ultrasonic irradiation in the presence of the phase transfer catalyst at ambient temperature and for a very short duration. The isolated product has a high purity.

L. Mhamdi, K. Said, G. Rigane, R. Ben Salem, Y. Moussaoui

Nozaki-Hiyama-Kishi, organochromium, Ultrasonic irradiation, phase transfer catalysis, C-C bond formation

Pages 61-67

1,3-dipolar cycloaddition of arylnitrile oxides to imidates: Synthesis of novel 1,2,4-oxadiazole derivatives

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A series of 1,2,4-oxadiazole derivatives were prepared via a 1,3-dipolar cycloaddition reaction of various oximes with imidates. The structures of all the new synthesized compounds have been established by 1H, 13C-NMR and IR spectroscopy, as well as by MS spectral data.

M. Hachicha, M. Balti, I. Jalloul, M.L. Efrit

1,3-dipolar cycloaddition, 1,2,4-oxadiazole, imidates, arylnitrile oxides

Pages 68-72

Synthesis and proton conductive properties of novel sulfonated (sulfone-triazoles) copolymers

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A new bisphenol containing 1,2,3-triazole ring (BPT) was synthetized using the click reaction and copolymerized with diammonium salt of 4,4'-difluorodiphenylsulfone-3,3'-disulfonic acid (DFPSS) and 4,4'- difluorodiphenylsulfone (DFPS) to prepare new copper free sulfonated sulfone-(1,2,3-triazole) copolymers (SSTP) for use as a proton exchange membrane fuel cells. Four copolymers with different ion exchange capacity (IEC) in the range of 1 to 1.6 meqH+/g were obtained by varying the molar ratio of the 3 monomers. The structure of SSTP was confirmed by NMR. They are soluble in polar aprotic solvents such as NMP, DMF and DMSO and show good thermal properties. Membranes from three of these SSTPs were prepared using the solution casting method and characterized in order to determine their water uptake (WU) and their ionic conductivity at 80°C.

F. Sebai, I. Abdelhedi Miladi, C. Marestin, R. Mercier, H. Ben Romdhane

Proton exchange membrane fuel cells, sulfonated polytriazoles, click reaction

Pages 73-79

Antioxidant and gastroprotective activities of polysaccharides from the Tunisian brown algae (Cystoseira sedoides)

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Fucoidan and sodium alginate were extracted from the Tunisian brown seaweed Cystoseira sedoides, with good yields. The samples were characterized by colorimetric, spectroscopic (FTIR) and chromatographic (SEC/ MALS/VD/DRI) methods. The quantitative estimation of the mannuronic acid/guluronic acid ratio (M/G ratio) of alginate was performed by FT-IR spectroscopy. It has been found that sodium alginate from C. sedoides contain more mannuronic acid (63%) than guluronic acid (37%). The isolated fucoidan was examined for in vitro antioxidant properties using various antioxidant assays. The sulfated polysaccharide exhibited important DPPH radical-scavenging activity (77% inhibition at a concentration of 5 mg/mL) and a considerable ferric reducing potential. An effective chelating activity was also recorded for the extracted fucoidan. Furthermore, the gastroprotective activity was determined for sodium alginate using HCl/EtOH induced gastric ulcers in rats. With a dose of 50 mg/kg, sodium alginate from C. sedoides showed a significant decrease (87%) in the intensity of gastric mucosal damages compared to a control group.

H. Hadj Ammar, J. Hafsa, D. Le Cerf, A. Bouraoui, H. Majdoub

Cystoseira sedoides, Polysaccharides, SEC/MALS/VD/DRI, Antioxidant activity, Gastroprotective activity

Pages 80-88

Rheological study of polyaniline dispersions

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In this work, polymer/polymer and polymer/solvent interactions of different PANi systems were investigated by rheometer, viscosimeter and scanning electron micrograph (SEM) techniques. Aggregation can be observed in the DMAc/DMF mixtures, through mixing a fixed amount of PANi at molecular weight =100 000. On application of steady shear micellar entanglements are ruptured and the system exhibits yield properties followed by shear thinning. From the frequency dependence of storage and loss modulus (G' and G'') it seems that the system behaves more like a viscous fluid rather than an elastic liquid. Physical network structures can also be formed by aggregation process with certain solvents.

Z. Barhoumi, N. Amdouni, J.F. Stumbé, S. Bistac

Polymer, chemical synthesis, chemical techniques, elastic properties

Pages 96-105

Modeling and optimization of phosphogypsum transformation into calcium fluoride using experimental design methodology

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In this work, the experimental design methodology has been used for the modeling and optimization of phosphogypsum transformation into calcium fluoride and sodium sulfate. For this reason a four factors box behnken design has been chosen to be used. The studied factors were reaction time (X1), NaF/phosphogypsum ratio (X2), mass of phosphogypsum (X3) and stirring speed (X4) while Y1 (the calcium yield) and Y2 (the purity of the formed precipitate) are selected as the responses variables. A compromise between the studied responses has been determined and the optimum conditions for this reaction have been fixed at a reaction time of 97.80 min, a NaF/phosphogypsum ratio equal to 2.06, with 8.13 g of phosphogypsum mass and a stirring speed of 506.39 rpm. At these experimental conditions the calcium yield is 95.61% and the purity of the formed precipitate is 98.86%.

H. Douahem, H. Hammi, A.H. Hamzaoui, A. M’nif

phosphogypsum, box behnken design, Response surface methodology, optimization

Pages 106-113

Optimization of magnesium oxychloride cement formation using experimental design methodology

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In this work, the experimental design methodology is applied to optimize the condition of formation of Magnesium chloride cement. A four factors factorial design to model and to optimize the operating parameters that govern the formation was used. The studied factors were mass ratio of MgCl2.6H2O/MgO, mixing time and stirring speed. Considered responses are compressive strength and setting time. The optimum operating conditions were quite efficient to have a good compressive strength and suitable setting time. The phases compositions of magnesium oxy- chloride cement were evaluated by X-ray diffraction, the morphological properties were examined by SEM and their thermal behaviour was analyzed by DTA/TGA. The presence of phase 5 confirms the good compressive strength of magnesium oxychloride cement.

A. Brichni, H. Hammi, S. Aggoun, A. Mnif

Magnesium oxychloride cement, Experimental design methodology, Optimization

Pages 114-120

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