JOURNAL of the Tunisian Chemical Society

serving the Research, the Education and the Industry

Reaction of trimethylamine hydrofluoride on α-functional oxiranes derived from bicyclo [3.1.1.] heptane and cyclohexane

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The trimethylamine hydrofluoride [(CH3)3N, 2HF] action on epoxyalcohols 2c, 2d and epoxyacetate 2e derived from bicyclo [3.1.1.] heptane does not give exclusively substitued fluorocyclohexenes. The action of the same reagent on epoxyalcohols 4c, 4d and epoxyacetate 4e derived from cyclohexane leads to fluoride derivatives. Epoxycarbonyl compounds 2a, 4a and 2b do not give any reaction under the same conditions excepting the epoxyketone 4b which leads to fluoroalcoholketones 4'b and 4"b.

M.M. El Gaied, A. Selmi

Pages 3-7

N.M.R. of monosubstitued benzenes (C6H5X) in a nematic phase (X = SeCl, SnCl3, PCl2, POCl2 or PSC12)

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The proton NMR spectra of monosubstitued benzenes C6H5X (X = SeCl, SnCl3, PCl2, POCl2, PSCl2) oriented in the Merck IV nematic phase were analysed. Effect of the substituant X on the geometry was discussed. The determined structures are in good agreement with those found by electron diffraction for phosphorous dichloride phenyl and phosphonic dichloride phenyl.

T. Turki, E. Haloui

Pages 9-13

Monoalkylphosphates as cathodic and anodic inhibitors of steel corrosion in a 3% wt NaCl aqueous solution

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Monoalkyl disodium phosphates salts RPO4Na2, when used at 10-2 and 5.10-2 molar concentration, act as efficient cathodic and anodic inhibitors of corrosion of steal in a 3% wt NaCl aqueous solution. Inhibition mechanism involves fixation of hydrophilic groups on the metal sites and so hydrophobic groups block oxygen diffusion towards the metal.

Y. Derbali, A. Shriri

Pages 15-20

Electrochemical behavior of uranium in sodium fluoride/sodium fluoroborate eutectic melt at 420°C

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The current-voltage curves were obtained at different electrodes in the eutectic NaF-NaBF4 melt. Various compounds of uranium were dissolved in the molten salt and then studied electrochemically. The oxidized form U(VI) and the reduced form U(IV) can be simultaneously stable and make up the forms of an electrochemical system. Oxidization of U(IV) occurs according to the following scheme :
UF62- → [UFn]6-n + 2é + (6-n) F-
[UFn]6-n + 2O2- → UO2F42- + (n-4)F-

A. Gadri, M. Brigaudeau

Pages 21-27

Structural, magnetic and IR studies of a nickel (II) tetraammonium bis (cyclotriphosphate) tetralydrate: Ni (NH4)4 (P3O4)2. 4H2O

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The main crystallographic features for a new cyclotriphosphoric compound: Ni (NH4)4 (P3O9)2. 4H2O are the following: a = 8.645 (2), b = 14.698 (3), c = 8.774 (2) Å and β = 95.89 (2)°. Crystal structure solved with heavy atom method shows a pseudo m symmetry of P3O9 ring. Nickel atoms are octahedrally coordinated by two oxygen atoms belonging to two P3O9 rings, and four water molecules form a complex anion: [Ni (H2O)4 (P3O9)2]4- Magnetic study of this compound leads to magnetic moment µeff. , spectroscopic splitting factor geff, and 10Dq of the octahedral ligandfield. Detailed I.R. studies and analysis with group theory are reported. Vibration frequencies are attributed to the valence P3O9 ring bands and local symmetry Cs of the ring is confirmed.

A. Jouini, M. Dabbabi

Pages 29-34

Elaboration and characterization of Na5 Y Si4 O12 type compounds

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Two methods of elaborating Na5 Y Si4, O12 type ceramics are described: a solid state reaction between SiO2, Y2O3, Na2CO3 and NH4H2PO4 at 1020°C and a "sol-gel" preparation process at room temperature. Characterization of the prepared materials was carried out using various techniques: XR, IR TG and DTA. Ceramic samples Na5-x Y Si4-X Px O12 have been synthetised. The rate of a secondary phase (Na3 Y Si3 Y Si3O9) increases with x. Addition of 1 to 2% of NaF or LiF decreases the amount of the later phase. Ignittion of the gel at different temperature leads to Na, Y Si3O9 at 500 °C, whereas Na5 Y Si4 O12 becomes visible at 700 °C and preponderant near 900 °C.

N. Fakhar-Bourguiba, L. Smiti-Dogguy, N. Gharbi

Pages 35-39

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