Effets de la nature de substituants sur les constantes d'acidité et les constantes de stabilité des complexes de quelques acides nitroso-5-barbituriques

The effects of substituents on the acidity constants and stability constants of complexes of some 5-nitrosobarbituric acids). The acidity constants of some 5-nitrosobarbituric acids (violuric acids) vary according to the degree of substitution and the nature of the substituent at the 1- and 3-positions of the pyrimidine ring. The value obtained at ionic strength 0.5 mol l^?1 made it possible to calculate the stability constants of simple complexes of divalent cations (Cu²⁺, Ni²⁺, Co²⁺, Zn²⁺, Fe²⁺). Potentiometric titrations were applied.     

Determination des constantes de stabilite des complexes des lanthanides trivalents avec les macrocycles polyaza polycarboxyliques : Etude des Propriétés Complexantes de la Résine Chélatante Chelite-N vis-à-vis des Lanthanides Trivalents

(Determination of the stability constants of trivalent lanthanide complexes with polyazapolycarboxylic macrocycles. Study of the complexing properties of the chelating resin Chelite-N for trivalent lanthanides.)The complexing properties of the chelating resin Chelite-N, which is characterized by amidoxime-type functional groups, for neodymium and holmium are described. The conditioning of the resin, its chelating capacity and its acid-base properties are examined first. To evaluate the formation constants of trivalent lanthanide complexes with the chelating resin, the resin is equilibrated with the lanthanide ions and then with an aqueous solution of ethylenediaminetetraacetic acid.     

Caracterisation par analyse thermique differentielle des complexes de l'aluminium avec les acides fulviques et humiques

Résumé L'analyse thermique différentielle sous oxygène permet de caractériser divers complexes formés entre l'aluminium et les acides fulviques (ou humiques): en particulier, les complexes pseudo-solubles ne sont pas identiques aux complexes floculés. Les liaisons hydrogènes qui unissent l'alumine hydratée aux acides fulviques (ou humiques) dans la forme floculée rendent l'ensemble beaucoup moins stable thermiquement que les trois formes complexes pseudo-solubles.

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Differential thermal analysis in oxygen renders possible the investigation of various complexes of aluminium with fulvic acid (or humic acid). The pseudo-soluble complexes are not identical with the flocculated complexes. The hydrogen bonds linking hydrated aluminium with fulvic (or humic) acids in the flocculated form reduce the thermal stability of the complexes compared with the three pseudo-soluble forms.

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Zusammenfassung Die Differentialthermoanalyse in Sauerstoff ermöglicht die verschiedenen Komplexe des Aluminiums mit Fulvinsäure (oder Huminsäure) zu charakterisieren. Die pseudo-löslichen Komplexe sind nicht identisch mit den flockulierten Komplexen. Die das hydratierte Aluminium mit den Fulvinsäuren (oder Huminsäuren) in der flockulierten Form verbindenden Wasserstoffbindungen vermindern die thermische Stabilität der Verbindung gegenüber den drei pseudo-löslichen Formen.

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Catalyse asymetrique avec des complexes chiraux de rhodium-diop—V: Effets des substituants lors de la reduction d'acides N-acylamino cinnamiques

Asymmetric synthesis of phenylalanine and its derivatives can be accomplished by asymmetric reduction of N-acylamino-cinnamic acid derivatives with CIRh(+)DIOP² as catalyst. The optical yield is influenced by the stereochemistry of the double bond, the para-substituent on the N-benzoyl group and the esterification of the carboxy group. The mechanism of the reduction is discussed.     

Applications analytiques des oxocarbones-I: composition et constantes de stabilite des complexes molybdiques de l'ion bromanilate: dosage spectrophotometrique du molybdene(VI)

The bromanilate ion B(2-) is a cyclic aromatic anion related to oxocarbons. We have shown by ultraviolet-visible spectrophotometry that it forms two 1:1 complexes with molybdenum(VI) in aqueous solution at pH 6. The variation of the conditional stability constants with acidity allows the calculation of the number of protons involved in each equilibrium. The formulae of the two complexes differ by a proton. The pK is 2.30. Molybdenum(VI) can be determined with bromanilic acid, H(2)B, at 340 nm in 3 or 1.4M perchloric acid. The accuracy is better than with chloranilic acid, H(2)C, when the concentration is about 1 mg/l. The better results obtained with H(2)B at high acidities are accounted for by the difference between the pK(1) values of the two acids (0.22 for H(2)B and 0.45 for H(2)C).     

Determination des constantes de dissociation ionique du chlorure de nitrosyle et de N2O4 dans le sulfolane

Determination of the ionic dissociation constants of nitrosyl chloride and dinitrogen tetroxide in sulpholane.

A silver chloride—silver electrode is used to study electrochemical systems involving nitrosyl chloride and dinitrogen tetroxide in sulpholane: Ag↓ + NOCl AgCl↓ + NO⁺ + e^- and Ag↓ + NOCl + NO^-₃ AgCl↓ + N₂O₄ + e^- The dissociation constants of these two NO⁺ donors determined in this way are: K_(NOCl) = 10^-11.8 mol l^-1 and K_(N2O4) = 10^-7.2 mol l^-1. A titration of N₂O⁴ solutions alone or in the presence of nitric acid is described. This titration is possible in mixtures which contain up to 90% (w/w) nitric acid.     

Etude de la complexation des lanthanides trivalents par les six isomeres de l'acide diaminocyclohexanetetraacetique: Partie 1: synthèses et détermination des constantes d'acidité et des constantes de formation des complexes 1:1 avec les lanthanides trivalents de l'acide trans-1,2-diaminocyclohexane-N,N,N′,N′-tétraacétique

(Study of the complexation of trivalent lanthanides by the six isomers of diaminocyclohexanetetraacetic acid. Part 1. Syntheses, acidity constants of trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid, and formation constants of its 1:1 complexes.)The syntheses of five isomers (1,2 cis, 1,3 cis, 1,3 trans, 1,4 cis, 1,4 trans) of diaminocyclohexanetetraacetic acid which are not commercially available are described. For comparison with literature vlaues, potentiometric measurements of the acidity constants of the sixth isomer (1,2 trans) and of the stability constants of its 1:1 complexes with trivalent lanthanides are reported for an ionic strength of 1 (KCl) at 25°C. In contrast to some literature data, the stability constants found, plotted as a function of Z, display only one discontinuity at the level of gadolinium.     

Telomerisation de l'isoprene en catalyse redox avec CCl4. Determination de la structure des telomeres etude des parametres de la reaction

There has been a study of the redox telomerization of isoprene using transition metal salts, particularly the influence of reaction parameters on the nature, yield and structure of the telomers.     

Etude de la télomérisation de C2F4 avec les iodures de perfluoroalkyle Partie I. Télomérisation radicalaire

The remomerization of C₂F₄ with C₆F₁₃F by various initiators has been achieved. These results have shown the effect of the temperature on the mechanism of the reaction. With t-butylperoxide (DTBP) at 130°C, we have observed that the apparent relative reactivity of C₈F₁₇I (monoadduct) is constant versus time. On the contrary, with cyclohexyl percarbonate(CHPC) at 47°C, it decreases continuously. On the other hand the ratio of the initial rates of consumption of monomer to telogen is close to 1 at high temperature while it is near to 2 at low temperature. These results clearly demonstrate that the mechanism proceeds by monoaddition in the first case (DTBP) while it is by propagation in the second case (CHPC). Secondly, we have proposed a mathematical simulation of these two kinds of reaction and discussed the validity of these laws.

Résumé

La télomérisation du C₂F₄ avec C₅F₁₃I par divers amorceurs radicalaires a été réalisée. Cela a permis de mettre en évidence l'influence de la température sur le processus réactionnel. En effet, avec le peroxyde de tertio-butyle (DTBP) á 130°C, on observe que la réactivité relative apparente du C₈F₁₇I,(monoadduit) est constante au cours du temps alors qu 'avec le percarbonate de cyclohexyle (CHPC), ce même paramètre diminue continuellement. Par aifleurs, le rapport des vitesses initiales de consommation en monomère et en télogène est proche de 1 à température élevée alors qu'il est voisin de 2 á basse température. Cela montre clairement que dans le premier cas, on a affaire á un processus par monoadditions successives, alors que dans le second, le radical créé se propage. Une modélisation des résultats a été proposée et discutée afin d' améliorer le contrôle de ces réactions.     

Thermodynamique de la complexation des metaux de transition par les acides α-amines. I. Etude potentiometrique des systemes cuivre(II)—phenylalanine et cobalt(II)—phenylalanine

Protonation constants for phenylalanine anion (L) and formation constants for complexes ML⁺ and ML₂ (M = Cu²⁺ or Co²⁺) are reported for I = 1 M (Na)ClO₄ and I = 1 M (Na)Cl at 25°C. The results are compared with those of other workers.     

Etude de la chimioselectivite de la reaction des dichloroboranes avec les azides fonctionnels : une synthese efficace d'amines secondaires fonctionnalisees.

The reaction of cyclohexyldichloroborane, used as a model, with a wide variety of functionalized azides has been studied. It has been shown to be an efficient synthesis of secondary amines in terms of chemioselectivity, yields and wide applicability.     

Action des composes organomagnesiens sur les pyrones-2-VII : Etude de la stabilite relative des hydroxy-6 dihydro-5,6 2h-pyrannes et des cetols tautomeres correspondants

In the reaction between organomagnesium compounds and 2-pyrones, the relative stability of the 6-hydroxy 5,6-dihydro 2H-pyrans and their tautomeric forms (ketols) has no influence on the reaction pathway. When ethylenic ketols are obtained, the corresponding tautomeric dihydropyranols are prepared in a selective way by reaction of nucleophilic reagents on the 3,6-dihydro-2-pyrones. In the other hand, the exclusive formation either of the dihydropyranols or of the unsatured ketols E, during these two reactions, shows up that here is no equilibrium between these two entities in the experimental conditions.     

Hydrogenolyse des disilanes issus de la synthese industrielle des methylchlorosilanes. Obtention de MeSiHCl2 et Me2SiHCl

The chlorodisilane residue from the industrial synthesis of methylchlorosilanes is cleaved under hydrogen (25 bars) in the presence of HMPT/nickelocene mixture or nickel (resulting from the reduction of dry NiCl₂ by Et₃SiH) and leads to the formation of methyldichlorosilane (noble product), to the detriment of the methyltrichlorosilane (much less noble). This reaction also gives an appreciable amount of the rare and very useful dimethylchlorosilane.     

Etude de la reaction de (MClcod)2 (M = Ir,Rh) avec les coordinats PClxPh3-x dans CDCl3

An NMR study of the reaction of (MClcod)₂ (M = Ir, Rh; cod = 1,5-cyclo-octadiene) with the ligands PCl_xPh_3-x, has been developed. Except when x = 3 we obtained as the first step the complex MClcod(PCl_xPh_3-x). This compound reacted with an excess of phosphine if x = 1 or 2, to give the complex MCl-(PCl_xPh_3-x)₃. However if M = Ir we have shown the formation of an intermediate species IrClcod(PCl_xPh_3-x)₂. We have studied the kinetics of the reaction:

When x = 3, we obtained the complexes (IrClcod)₂(PCl₃) and (IrClcod)₂(PCl₃)₃, for which we propose the structures.     

Spectres RQN de quelques complexes d'addition molẃculaires de SbCl5 avec des coordinats oxodonneurs

NQR spectra of the SbCl₅(DMF). SbCl₅(OSCl₂), SbCl₅(OSeCl₂), and SbCl₅(OVCl₃) adducts are reported and discussed. A scale of the donor strength of the ligands based on the comparison of these spectra with those of SbCl₅(OPCl₃) and SbCl₃,(C₆H₅COCl) is proposed: VOCl₃ < SOCl₂ < C₆H₅COCl < POCl₃ < SeOCl₂. Furthermore, the data are consistent with a C₅ symmetry for the SbCl₅(OSCl₂) adduct.     

Les differentes formes cristallines de Y3ReO8: Relations avec la structure fluorine

The monoclinic Y₃ReO₈β phase is synthetized at 40 kbar and 900°C. The crystal structure is solved to an R value of 0.058 for 1341 observed reflections, by conventional methods using automated four-circle diffractometer data. This structure can be visualized as a fluorite-related superstructure, the large difference between the ionic radii of Re⁷⁺ and Y³⁺ being favorable to cation ordering. The heating to 500°C of this phase under atmospheric pressure leads to a disordered fluorite structure of the form Y₃ReO₈α. An intermediary metastable phase Y₃ReO₈α′ is obtained by heating a Y₃ReO₈β single crystal to 350°C. The structural relations between these three crystalline forms of Y₃ReO₈ and the fluorite structure are discussed.     

Chimie des complexes de metaux de transition avec des hydrocarbures cyanes : III. Quelques observations sur la conformation et la reactivite de complexes dicyclopentadienyles du molybdene et du tungstene

A new class of cyclic telluronium salts has been prepared. All the salts are stable in solution in CHCl₃ or dimethylsulphoxide (DMSO). Conductivity measurements in DMSO and dimethylformamide (DMF) have shown that considerable ion pairing occurs in solution. Infrared, ¹H, ¹³C, ¹²⁵Te NMR, and mass spectra are reported and discussed.     

Contribution a la valorisation industrielle des dechets de tanneries: cas de la cimenterie

A contribution to the industrial valorization of tannery waste: the case of cement industry. The present work addresses the possibility of valorization of tannery waste incineration ashes in the cement industry. To this end, the impact of the addition of ashes at various percentages (0, 5, 10, 15, 20, 25, 30, 35, 40, and 45 % in mass) on some mechanical and physical parameters of cement was examined: normal consistency (%), the beginning of setting (hr), the end of setting (hr), the hot expansion (mm), the resistances to compression and to bending (N/mm²) determined on normalized 4x4x16 cm samples. The impact of the treatment environment (20 °C and 100% of relative humidity RH, 30 °C and 70 % RH, 45 °C and 45% RH) was also taken into consideration. The obtained results reveal that the normal consistency, the beginning and the end of setting vary linearly with the quality of added ashes. Above an addition of ashes of 30 %, the end of setting exceeds the standards demanding a maximum of 10 hours. Additionally, the results indicate that whatever the environment treatment may be, the resistances to compression and to bending increase with the increase of the sample age; they vary inversely to the amount of ash addition. The results allow to conclude that for an ash addition of 15 % and after an ageing of 30 days, the resistance to compression is higher than 40 N/mm², thus allowing the production of CPA 400 cement. These results also allow to conclude that samples kept in a humid environment give the best resistances to compression and to bending, by comparison with those kept in a dry environment.