JOURNAL of the Tunisian Chemical Society

serving the Research, the Education and the Industry

Stereospecific synthesis of spiro-cyclopropanes

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The addition of 2-diazopropane (DAP) 1 with 2-arylidenindan-1-ones 2a-c has led exclusively to spiro-pyrazolines 6a-c. When the two faces of dipolarophile are not equivalent (case of 2d-f) the addition gave two spiro-pyrazolines 7d-f and 8d-f diastereoisomers. Pyrazoline 7d-f resulting from DAP approach on the less bulky face of enone is unstable and evolves spontaneously to the ethylenic derivatives 9d-f. Photolysis of 6a-c and 8d-f has led to spirocyclopropanes 10a-c and 11d-f with stereospesific manner.

R. Gharbi, J. Lachheb, M. T. Martin, Z. Mighri, A. Khemiss

Pages 245-255

Interactions study of polypeptides-water-methylene blue

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The interaction of Methylene blue (M.B) dye with three different polypeptids [Polyasparagine (PAg), Polyaspartic acid (PAsp) and polyalanine (PAl was studied by UV- spectophotometry. The results show that different types of interactions are possible depending on concentration and polypeptids natures and the formation of complex whose constants are determined. The role of water was pointed out.

H. Ghabi, M. Dhahbi

Interaction, polypeptids, Methylene blue

Pages 267-273

Deposit inhibition of calcium carbonate in geotherma water’s scale at El Mansoura area

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The chemical inhibition of calcium carbonate precipitation was found to be an effective method to fight against scaling in the Tunisian geothermal water. A semi pilot test was effected in EL MANSOURA area using the sodium tripolyphosphate Na5P3O10 (STPP), confirm the efficacity of this inhibitor.

K. Walha, M. Ben Amor, R. Rosset

Scaling tendency determination, chronoelectrogravimetry, antiscale inhibitor: sodium tripolyphosphate

Pages 275-287

Applying solubility diagrams for recovering sodium sulfate from natural brine. Example of Sebkha El Adhibate

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The transformation of double salts recovered by solar evaporation of natural brine into commercial salts, is frequently a delicate operation. It depends on many parameters: the temperature, the quality of process water, and the composition of raw material. For studying these parameters, a pilot unit is designed and built. The salts to transform are astrakanite [Na2Mg(SO4)2.4H2O] and epsomite [MgSO4.7H2O]. The aim of this study is to design a flow sheet for producing sodium sulfate from a raw material recovered by solar evaporation of Sebkha El Adhibate natural brine.

A. M’nif, L. Zayani, R. Rokbani

transformation of double salts, natural brine, astrakanite, epsomite

Pages 289-299

Sol-gel elaboration of mixed chromium and aluminum oxides: I. Chemical preparation

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Gels of mixed chromium and aluminium oxides were prepared by hydrolysis and polycondensation of organic precursors of metals. In this work, we try to understand the chemistry involved in the preparation, to better control the formation of final material. Evolution of UV-vis, ESR and IR spectra with stirring time, shows a modification of the environment of Cr3+ ions assigned to the formation of Cr[(acac)Al(O-Bu)3]3 complex. The rise of chromium amount or acetic acid reduces the gelation rate, whereas an extent of aging time favors the gelation.

L. Barakat, A. Ghorbel

sol-gel, chromium, UV-Visible, ESR, IR

Pages 301-308

Sol-gel elaboration of mixed chromium and aluminum oxides: II. Relation: Preparation parameters, structure and reactivity of Cr2O3-Al2O3

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Gels of chromium and aluminium oxides have been obtained from Al(O-Bus)3 and Cr(acac)3 in sec-Butanol after acetic acid addition. The rise of chromium amount affects the dispersion and the chromium oxidation state at the support surface. The activity of the catalysts in partial oxidation of paraxylen enhances when the chromium amount increases from 5 to 10% but decreases markedly for an amount equal to 18% for which ESR study shows the presence of chromium oxid clusters Cr2O3. The amount of acetic acid added influences the solid texture. Thus, when the molar ratio K rises, the specific surface increases and the solids became more porous. The stirring time (Ta) of organic precursors governs the distribution of chromium between the surface and the support. Thus, when (Ta) increases, the chromium is more incorporated in the alumina support.

L. Barakat, A. Ghorbel

sol-gel, chromium, oxidation, paraxylen

Pages 309-318

Elaboration of semiconducting thin layers of CuInSe2 by electrodeposition in citrate medium

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The preparation of semiconducting thin layers of CuInSe2, have been realized at different potentials : -1,1 V/ESM, -1,2 V/ESM, -1,3 V/ESM, on SnO2 / glass substrate covered with conductive and transparent tin oxyde. We have investigated the annealing treatment effect at air and selenium atmospheres on the structural and optical proprieties of these layers. X-Ray diffraction has shown a better cristallinity after annealing. The chemical analysies of metallic precursors In and Cu, present in solid phase after synthesis, has shown an excess of Copper at -1,1 V/ESM and an excess of Indium at -1,3 V/ESM. It is only at the last potential that the layers acquire a convenient proportion of Selenium. The study of the optical properties of this material allowed us to determine its Eg which reaches 0,95 eV.

E. Selmane Bel Hadj Hmida, M. Dachraoui

Thin solid films, Electrodeposition, CuInSe2 (CIS), Gap Eg, Citrate solution

Pages 319-335

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