Influence de la Température et de la Présence des Ions Etrangers sur la Cinétique et le Mécanisme de Formation de la Goethite en Milieu Aqueux

Effect of Temperature and Presence of Foreign Ions on the Kinetics and Mechanism of the Goethite Formation in Liquid Phase We studied the influence of temperature and addition of some foreign ions on the kinetics of transformation of the goethite in sulfate medium by slow air bubbling. The temperature up to 70°C does not influence the kinetics of oxidation; this proves that the transfer of oxygen taken place through the liquid phase. Manganese and colbalt cations impede the formation and the growth of αFeOOH crystallites. Citrate and phosphate anions both hinder this transformation.     

Recherches sur la formation et la transformation des esters LXXVIII. Sur la réaction de l'isothiocyanate d'o-méthoxycarbonyl-phényle avec des diamines et l'hydrazine,et sur la cyclisation de quelques N-phényl-N′-hydroxyalcoyl-thio-urées

1-Amino-2-dimethylamino-ethane and 1-amino-3-dimethylamino-propane react with o-methoxycarbonylphenyl isothiocyanate (I) to yield the corresponding 3-(ω-dimethylaminoalkyl)-2-thiono-1,2,3,4-tetrahydroquinazolin-4-ones (V). The tertiary amino group of V is quaternized to the corresponding ammonio derivative VI when treated with methyl iodide in methanol.     

Etude des pKa et de la protodéboronation des acides furanneboroniques

The pK_a s of the furanboronic acids and their formyl, acetyl and methyl derivatives were determined in order to investigate the influence of electronic and steric effects on the acidity of the boronic group. On the other hand, the protodeboronation kinetic studies of these different acids in perchloric acid may suggest a new mechanism for the electrophilic reaction, in agreement with isotopic effects, substituant effects and the strongly negative activation entropy. Comparison of the reaction rates between the benzene, thiophene and furan series allows one to calculate the specific reaction rate ρ of the protodeboronation.     

Extension de la méthode du «logarithme limite» [1] pour la détermination de la composition et de la constante de stabilité des complexes

A study of the conditions of applicability to weak complexes of the relation log x = v log V + log (β_v,cC^c) = f(logV), where V and C are variable and constant total concentrations of the constituants of the complexe, shows that for conditions other than C ? V, another function φ(log V) accounts better for the formation equilibrium of the complexe. From f(log V) and φ (log V) a relation t(log V) is derived whose simple analysis permits the determination of the composition and the stability constant of weak complexes. Applications are given to 1:1, 1:2, 2:2 composition.     

Etude du mécanisme de la réaction de hantzsch des thiazoles. I. Mise en évidence et détermination des produits intermédiaires et de dégradation

The Hantzsch thiazole synthesis from α-haloketones and thioamides, proceeds via intermediates that can be isolated under certain conditions. These have been identified, mainly by nmr spectroscopy, as thioimidate derivatives. The chain or cyclic structures of these compounds depend upon the nature of the substituents. Their dehydration gives together with the expected thiazole, secondary products which have also been isolated and identified as α-mercaptoketones and α-ketothiolesters.     

Etude par spectrométrie de masse de la fragmentation des cyclopentane-triols-1,2,3, des cyclopentane-tétrols et des cyclopentane-pentols

The mass spectra of the three cyclopentane-1,2,3-triols, six cyclopentane-tetrols and four cyclopentane-pentols stereoisomers have been studied. Complex processes, especially regarding the H₂O eliminations, were detected by extensive deuterium labelling.     

Recherches dans la série des cyclitols,XL. Préparation de cyclopentane-triols et de cyclopentène-triols et -diols

Two as yet unknown cyclopentene-triols have been prepared. The replacement of the halogen of cyclopentene derivatives brominated in the allylic position has been investigated. In the presence of dimethyl sulfoxide and sodium hydrogen carbonate, the bromine of some of the above mentioned allylic derivatives or the tosyloxy group of a dibenzoyloxy-monotosyloxy-cyclopentane derivative is replaced by a hydroxyl group without formation of any keto compound. The mechanism of action of the substitution agents is discussed.     

Synthèse partielle et propriétés oncostatiques des pseudo-tubulosines,analogues de l'émétine et de la tubulosine

Partial Synthesis and Oncostatic Properties of Pseudotubulosines, Analogues of Emetine and Tubulosine Pseudotubulosines, structural analogues of emetine and tubulosine, have been synthesized by either Pictet-Spengler or Bischler-Napieralski condensation from dihydrocorynantheal or corynantheidal. Spectral data, cytotoxic and oncostatic properties of these new alkaloids are described.     

Analyse en spectroscopie infrarouge, de la structure des complexes BF3 du méthanol, des méthanols deutériés et de l'acide acétique Comparaison de la liaison hydrogène et de la liaison donneur-accepteur

A study of the infrared spectra led to the conclusion that the 2-1 complexes formed from two molecules of methyl alcohol or acetic acid and one molecule of BF₃ have an open structure. One methyl alcohol molecule is linked by hydrogen bonding to a second molecule which is attached to BF₃. The consequences of the addition of BF₃ to the OH (OD) vibrators are similar to those of the formation of a hydrogen bond: elevation of the wave number of the in-plane bending vibration and lowering of the wave number of the stretching vibration compared with the monomer.     

Sur l'orientation de la nitration des nitriles et amides coumariliques Bz-méthoxylés

Direct nitrations of 2-carboxamido- and 2-cyano-Bz-methoxybenzofurans by nitric acid in acetic anhydride always yiels two derivatives nitrated on the homocyclic ring at the ortho or, possibly, the para position to the methoxyl group. The proportions vary with the case in question. The methoxylated nitrocarboxamides and nitronitrilies obtained can be demethylated nitrocarboxamides and nitronitriles obtained can demethylated by pridinium chloride. Their hydrokysis into the corresponding acids is performed without demethylation by diluted sulfuric acid and, except in one case, with simulatenous demethylation by dilued soda.     

Synthèse de nouvelles amidines bicycliques . Dérivés de la pyrimidine,de la quinazoline et de la diazépine-1,3

The synthesis of pyrrolo[1,2-α] pyrimidines is described. Several homologous compounds contain pyridine or azepine instead of pyrrole ring. They are obtained by cyclization of iminolactams with β-ketoesters, αβ-unsaturated esters, aldehydes or ketones, or diketene. The possibility of obtaining isomers is discussed.     

Synthèse et réactivité des bromhydrines dérivées de la chromone

Bromohydroxylated derivatives of chromone are obtained by addition of N-bromosuccinimide in dimethylsulfoxide. The configuration and conformation of these compounds are confirmed by NMR spectroscopy. Alkaline alcoholates react with these bromohydrins to give a ring contraction into 2-formyl-3-benzofuranone.     

Sur la réaction de reformatsky : I. Préparation et réactivité des organozinciques issus de divers crotonates d''alcoyles

Lithiation of (Me₃Si)₃CH by methyllithium (ether-THF) yields (Me₃Si)₃CLi and by t-butyllithium (C₅H₁₂-TMEDA) yields (Me₃Si)₂CHSiMe₂CH₂Li. Only starting material is recovered when (Me₃Si)₃CH is allowed to react with n-butyl- lithium (ether-THF and C₅H₁₂-TMEDA) and t-butyllithium (C₅H₁₂ and C₅H₁₂- THF). (Me₃Si)₄C is lithiated by t-butyllithium (C₅H₁₂-TMEDA) to give (Me₃Si)₃- CSiMe₂CH₂Li, but not by methyllithium (ether-THF and ether-THF-TMEDA). The structures of the lithiated compounds are based on the carbonation products. The above results are explained in terms of carbanion stability and steric effects. Spectral data are reported on the α-silylacetic acids.     

L'action de l'ammoniac sur l'hydroxyde de cadmium et la stabilité des complexes en milieu aqueux

The solubility of precipitated Cd(OH)₂ was determined at 25°C in 1 M NaClO₄, as a function of pH and of the ammonia content of the solutions. Formation constants were obtained for the following hydroxo, ammine and hydroxo-ammine complexes: CdOH⁺, Cd(OH)₂, Cd(OH), CdNH, Cd(NH₃), Cd(NH₃), Cd(NH₃) and Cd(OH)₂NH₃. The solubility product of the hydroxide was also calculated. The presence of polynuclear species was investigated by titrimetric determinations of the hydrogen ion concentration at constant metal concentration.     

Stereochimie de la deprotonation et de la reaction d'aldolisation des dithioesters

Cis lithium thioenolates are preferentially formed by deprotonation of dithiopropanoates with lithium diisopropylamide in tetrahydro-furan at -78°C. The cis selectivity observed, is unproved by increasing the alkylthio group size or by the ability of this group to chelate the lithium cation. When more bulkier bases such as lithium 2,2,6,6-tetramethylpiperi-dide or lithium hexamethyldisilazane are used, the selectivity is lowered. This lowering of selectivity is suppressed when the deprotonation is performed in presence of 12-crown-4. Addition of hexamethyl phosphoramide to the base does not invert the selectivity as it uas reported for the deprotonation of esters ; a rather better cis selectivity is reached in the case of methoxymethyl dithiopropanoate. These original results are well understood in terms of an open transition state model. Preformed lithium thioenolates are reacted uith a variety of aldehydes and afford stereo-specifically syn aldols. The influence of hexamethylphosphoramide and reaction time is also examined.     

Recherches dans la série des cyclitols XXXIX RMN. de protons d'hydroxyles de cyclopentane- et de cyclopentène-polyols

Several mono-, di-, and tri-hydroxy derivatives of cyclopentane and cyclopentene have been studied by NMR. spectroscopy. The chemical shifts and the coupling constants of the OH groups have been correlated with their position, with their configuration and, in some cases, with their conformation.     

Recherches dans la série des cyclitols XLVI. Actions de diazoalcanes sur la pentahydroxy-2,4,6/3,5-cyclohexanone et sur son dérivé penta-O-acétylé II. Etude de pentahydroxy-alkyl-C-cycloheptanones

On treatment with higher diazoalkanes, 2,4,6/3,5-penta-acetoxy-cyclohexanone (penta-O-acetyl-myo-inosose-2 or -scyllo-inosose) afforded by ring expansion all-trans-penta-acetoxy-C-alkyl-cycloheptanones, which by deacylation were converted to hemiacetals. The reactions with diazoalkanes of the penta-acetoxy-inosose in the presence of aluminium chloride and of the free inosose in water solution have also been studied. The structure, the configuration, and, in some cases, the conformation of the new compounds have been established and some of their reactions have been investigated. The mechanisms of formation of the ring expansion products and of the concomitant spiro-epoxides have been discussed.