JOURNAL of the Tunisian Chemical Society

serving the Research, the Education and the Industry

Propriétés chimiques des hydrazonates: Action des organomagnésiens sur les hydrazonates simple, N-1-acylés et N-1-éthoxycarbonylés

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The organomagnesian react with hydrazonates to give hydrazone. Contrary to imines and substituted imidates, we haven't observed an additional reaction on the imidic double bond.

F. Zribi, F. Chabchoub, M. Kossentini, M. Trabelsi, Y. Le Bigot, M. Salem


Pages 971-976

Etude cinétique et mécanisme de dégradation hydrolytique du carbaryl par HPLC à polarité de phases inversée et par spectrophotométrie UV

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The present paper reports on the investigation of hydrolysis kinetic of carbaryl or 1-naphtyl-N-methylcarbamate in aqueous media. The determination of α-naphtol by liquid phase chromatography and spectrophotometric UV titrations, as the main product of carbamate hydrolysis gives evidence for the significant reactivity of this insecticide. The obtained positive activation entropy ΔS# = + 60,33 J mole-1K-1, indicates an E1cB hydrolytic mechanism involving unimolecular decomposition of carbaryl via a methylisocyanate intermediate. This elimination process is confirmed by the position of the coordinate (pK = 9,39; logkOH = 2,31) corresponding to the carbaryl point on the Brönsted line, determined by Williams for a series of substituted N-methylcarbamate whose decomposition in aqueous media has been established to follow the E1cB mechanism. 

L. Latrous, N. Ben Hamida, S. Sabbah

carbaryl, kinetic, hydrolysis, spectrophotometric U.V.

Pages 977-986

Structures de l’iodure de propargyle et de l’iodoallène par RMN en phase nématique

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NMR spectra of partially oriented propargyl iodide and iodoallene yield the complete structures of these molecules. Temperature and solvent effects on these structures are analysed and discussed. Obtained geometries are in good agreement with expected values and microwave results for homologous molecules, except for the ≡C–H bond length in propargyl iodide.

Y. Arfaoui, E. Haloui

propargyl iodide, iodoallene, structure, NMR, nematic liquid crystal

Pages 987-995

Accumulation du chrome par Juncus fontanesii

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We have used Juncus fontanesii, helophytic plant, to accumulate the chromium, with its two oxydation degrees III and VI, from aqueous solutions containing this metal at 50, 100, 150 and 300 mg/L as initial concentrations using two surfacic densities of the fresh biomass : 2,8 and 5,6 kg/m2. This study, without adding nutritive elements, shows that the more important quantity of the metal was fixed by the roots : 70 to 80 % of Cr(III) and 85 to 95 % for Cr(VI). When the concentration is higher than 50 mg/L, plant releases part of the chromium to the medium. During the experiences, plants displays visual signs of physiologic perturbation.

M. A. Oueslati, M. Haddad

chromium, toxic metals, Juncus fontanesii, aquatic plants

Pages 997-1006

Electroréduction des imidates N-(2 nitrophényl): Application à la synthèse des benzimidazoles

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The electroreduction of some imidates N-(2-nitrophenyl) derivatives (I) was investigated by cyclic voltammetry and controlled potential electrolysis on mercury electrode. In aprotic organic media, the reduction of (I) was believed to interest preferencially to the nitro groupement and leads to hydroxylamine derivatives which involve, in situ, to the formation of heterocyclic nitrogen compound.

H. Medini, R. Abderrahim, R. Kossai, K. Boujlel

Pages 1007-1013

Neutralisation des huiles acides de grignons d’olive par la chaux

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The neutralization of acid olive oil cabe by means of lime takes place at room temperature, without using a solvent, in a slightly hydrated area when the acidity of the treated oils is relatively low. Whereas when the acidity is high, the addition of hexan in the reaction leads to a diminution of the viscosity of the mixture and then to the end of the reaction. The physicochemical features of lime-neutralized and centrifugation-separated oils correspond to those of a very fine oil.

K. Essid, F. Ladhar, M.H. Frikha

Pages 1015-1028

Oxydation électrochimique de l’acide vanillique sur des oxydes d’or et de plomb

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The electrochemical oxidation of vanillic acid is studied at gold oxides disk by cyclic voltammetry. Vanillic acid is in solutions of 0.5 mol.L-1H2SO4 in acetone-water mixtures formed with 0-80 vol% acetone. The cyclic voltammogram shows one irreversible anodic peak and a post-peak. The effect of experimental data on the ratio of these two peaks is examined. The mechanism proposed by assuming a two electron oxidation, involves the intermediary of the three phenoxonium cation mesomers which relative importance is governed by their relative stability. Hydrolysis of these phenoxonium cations would lead to protocatechoïc acid, methoxyhydroquinone and 3,4-dihydroxy-5-niethoxybenzoic acid respectively. The two formers are identified by the means of their authentic voltammograms. The preliminary results show that vanillic acid is quantitatively oxide by electrolysis at dioxide lead to produce by the intermediary of protocatechoïc acid and methoxyhydroquinone, the formic, oxalic, glyoxalic and maleic acids which degradation leads to carbon dioxide.

S. Chaabane Elaoud, R. Abdelhedi, A. Savall

vanillic acid, olive oil waste water, oxidation, electrochemistry, lead dioxide anode, gold oxides anode

Pages 1029-1042

Préparation et structure cristalline du composé Na((HOCH2CH2)3NH)2PW12O40-H2O

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The compound Na((HOCH2CH2)3NH)2PW12O40.H2O crystallizes in the triclinic system, space group P-1 The cell parameters are: a = 14.235(2)Å, b = 17.619(2)Å, c = 10.262(2)Å, α = 102.76(2)°, β = 104.58(1)°, γ = 75.60(2)°, V = 2378(1)Å3 with Z = 2. The structure of the anion [PW12O40]3- (4 3 m pseudo-symmetry) is essentially that of Keggin. The structure of the compound consists of a lamellar organization formed by inorganic layers parallel to the (110) plane, alterned with planes containing the cationic groups.

H. Chebbi, A. A Hajem, A. Driss

phospho-tungstate, heteropoly-oxometallate

Pages 1043-1051

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