JOURNAL of the Tunisian Chemical Society

serving the Research, the Education and the Industry

L’Ambrox® et l’ambracétal à partir du sclaréoloxyde via des radicaux alcoxy

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Ambrox® and ambraketal 5 are obtained by a new method using tertiary alkoxy radicals 6 generated "in situ" from hemiketal 3 and hydroperoxyhemiketal 2. Alkoxy radicals undergo β-fragmentation or 1,5-hydrogen abstraction gave Ambrox® and ambraketal 5 respectively. Hemiketal 3 was obtained by ozonolysis of sclareol under oxidative alkaline conditions (H2O2/NaOH). Dehydration of hemiketal 3 under vacuum distillation gives sclareoloxide 1 which reacts with H2O2/AcOH to give hydroperoxyhemiketal 2 in quantitative yields.

A. Fekih, F. Aloui, K. Gafsi

Ambrox®, ambraketal, sclareol, sclareoloxide, alkoxy radicals

Pages 265-274

Les additifs chimiques en production pétrolière: Définitions, principes, rôles et mode de sélection

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Oilfield waxes and emulsions are petroleum by-produces that increase the costs of production, transportation, and refining by causing equipment failures, plugged pipelines, and decreased throughput. This paper explains the physical and chemical problems associated with waxes and emulsions and the new technologies for treatment of these problems by chemical additives.

A. Boukadi, H. Amri

emulsions, paraffinic deposits, chemical additives

Pages 275-284

Oxydation anodique du p-xylène à l’électrode et par catalyse redox homogène

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The electrochemical oxidation of p-xylene in acetonitrile is carried out at the electrode and by homogeneous redox catalysis. The mechanistic investigation by means of cyclic voltammetry has shown that the anodic process obeys an ECE (or ECDisp) type mechanism where the first electron transfer is the rate determining step and is followed by a rapid deprotonation of the cation radical obtained in the above step. The preparative electrolysis, carried out at a constant potential located on the first wave, led to a nucleophilic substitution of a lateral methyl group. The products obtained depended on the reaction media. Thus, in the absence of a base, the main product was N-(4-methylbenzyl) acetamide. Alternatively. oxidation of p-xylene by means of homogeneous redox catalysis with organic mediators, allowed the determination of the deprotonation rate constant of p-xylene cation radical. Furthermore, it led to a selective transformation of p-xylene in N-(4-methylbenzy) acetamide with an important energetic gain.

N. Ben Salah, F. Matoussi

electron transfer, p-xylene, deprotonation, homogeneous redox catalysis

Pages 285-294

Structure cristalline et fragmentation par impact électronique du 7,8-dibromo-2,3-dihydro-2H-1,5-benzodioxépine

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The 7,8-dibromo-2,3-dihydro-2H-1,5-benzodioxepin (C9H8Br2O2) (I) was synthesized. This product was studied by electronic impact at 70 eV. Identification of different obtained ions permitted the proposal of a molecular fragmentation schema. The identification of halogenated acetylenic fragments from benzenic cycle was done. Its homologue bromonitrile (III) was synthesized and its impact electronic fragmentation was compared to that of (I). Crystal structure of (I) was determined. It crystallizes in the orthorhombic space group Pbca with a = 8.287 (2), b = 20.262 (3), c = 11.584 (3) Å, Z = 8 and V = 1944.9 (7) Å3, The molecules of (I) are in chair conformation and are connected by Vander Waals interactions.

F. Ammari, T. Ben Chaabane, F. Meganem

Heterocycle, Crystal structure, Mass spectrometry

Pages 295-303

Nouvelle élaboration de VO2(B) par voie hydrothermale

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The title compound VO2(B) was prepared as a single-phase material by a hydrothermal reaction (180°C, 96 hours, autogenous pressure) from a mixture of V2O5, 1,4-dihydroxybenzene and H2O in the molar ratios I: 1: 309. It was characterized by Scanning Electronic Microscopy (SEM), Brunauer-Emmett-Teller (BET), powder. X-Ray diffraction, Thermal Analysis (TGA-DTA) and Infrared spectroscopy. VO2(B) crystallizes in the monoclinic system with a = 12.13(4) Å; b = 3.697(6) Å, c = 6.4(2) Å, and β = 106.1(2)°.

F. Sediri, N. Etteyeb, N. Gharbi

VO2(B), hydrothermal synthesis, 1,4-dihydroxybenzene and V2O5

Pages 305-313

Détermination de la diffusivité de l’eau au sein d’un gel de gélatine

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An experimental and mathematical study of the diffusion of water was carried out in order to optimize the criteria related to quality and energy during drying of a sample of a Gelatine gel by convection and a radiating contribution of the High Frequencies (Microwaves and Infrared). The results, within the framework of this first part of research, allowed:

  • to determine a mathematical expression describing the dependence of the coefficient of diffusion versus the moisture of the product in the studied case
  • to highlight the "undeniable" effect of the vitreous transition along an isothermal axis on the dependence from material diffusivity according to the moisture of the medium
  • to calculate the coefficient of mutual diffusion of water and the constants of WLF.

F. Zagrouba

Gelatine, Diffusivity, Sorption, Vitreous Transition, Viscoelastic

Pages 327-333

Application d’un plan d’expériences mixte à l’étude de l’optimisation de la formulation d’une poudre de détergent

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This article illustrates the interest of the use of experimental design across an example of detergent powder formulation. The study of the influence of the temperature and three components (sodium perborate, sodium silicate and titanium dioxide) on the cleaning performances and on the cost of detergent were carried out by the realization of combined experimental design. The obtained models allowed the evaluation of the detergent efficiency for different types of smudges.

F. Hellal

formulation, experimental plan, detergent, combined experimental design, response surfaces

Pages 335-348

Préparation, caractérisation et étude structurale du chromate de 2-(cyclohex-1-ényl)-éthylammonium

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The title compound [C6H9(CH2)2NH3]2CrO4 has been prepared as a single crystal by slow evaporation at room temperature. It was characterized by EDX analysis, infrared spectroscopy, UV-visible and thermal analysis TG-DTA. The crystal structure was determined by single crystal X-ray diffraction. This compound crystallizes in the monoclinic system, space group P21/c. The cell parameters are: a = 6.475(5) Å, b = 8,173(2) Å, c = 37.010(1) Å. β = 92.94(5)°, V = 1956(1) Å3 with Z = 4. The asymmetric unit contains one chromate anion and two independent organic cations noted A and B, The structure consists of inorganic layers parallel to (001) plane, separated by organic double layers, The structural cohesion is established by a two-dimensional network of N-H...O hydrogen bonds.

H. Chebbi, R. Ben Smail, A. Driss

organic chromate, chemical preparation, crystal structure

Pages 349-359

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