Enthalpie de dissolution a 298 K des fluorures de potassium et de cesium dans l'acide fluorhydrique et le fluorure d'hydrogene

A calorimetric cell designed for studies of reaction in anhydrous hydrogen fluoride has been constructed. Enthalpies of solution of KF and CsF in aqueous solution of HF (from 0 to 100 % HF) have been measured.     

Polymerisation cationique de l'indene amorcee par le tetrachlorure de titane-I Influence des impuretes du solvant,le chlorure de methylene,et effets cocatalytiques de l'eau et de l'acide chlorhydrique

The polymerization of the system indene-titanium tetrachloride-methylene chloride gave irreproducible kinetics which have been attributed to variable concentrations of impurities in the solvent. Incomplete yields sometimes observed at ?70° are also caused by impurities, but introduction of water and hydrochloric acid then gives complete yields. A new method of solvent purification has been used giving reproducible yields and rates. In such cases, monomer consumption at ?70° follows the rate law log [M]_o/[M] = kt.     

Dosage de l'hydrogene,de l'azote et de l'oxygene dans le monocarbure d'uranium

A method is described for the determination of hydrogen, oxygen and nitrogen in uranium monocarbide. Hydrogen and oxygen are determined by the classical or modified “Platinum flux” method at 2000° with a coefficient of variation of 10%. Nitrogen is determined at 2000° by the modification of the “Platinum flux” technique. The results obtained are in agreement with those found by Kjeldahl analysis. The coefficient of variation is about 10%. A procedure for the simultaneous determination of the 3 gases is given.     

Voltammétrie de l'argent par redissolution anodique sur electrode de carbone vitreux et application au dosage de l'argent dans l'uranium et le pluton

Anodic stripping voltammetry of silver on a glassy carbon electrode, and application to the determination of silver in uranium and plutonium.The use of a glassy carbon electrode for the anodic stripping voltammetry of silver, without deposition of a preliminary mercury film is described. The deposition time, scan rate, rotation speed and molarity of the sulfuric solution have been studied; the method is applied to the determination of silver in uranium and plutonium.     

Heterocyclisation intramoleculaire d'alcools possedant un squelette cedranique. Oxydation par le tetraacetate de plomb et par l'oxyde de mercure et le brome

Oxidation with lead tetra-acetate of neoisocedranol yields the corresponding ether in good yield. Under the same conditions, cedrol remains unchanged; however, when cedrol is reacted with mercuric oxide and bromine, the corresponding ether is obtained as major product. The structure of the substrates is linked with the mechanism of the two reactions and with the nature of the intermediates in the heterocyclisation reaction. The difference in behaviour between the two substrates towards the two oxidising agents is rationalized.     

Influence de la solvatation par le tert-butanol sur la structure et la reactivite de l'enolate de potassium de l'acetylacetate d'ethyle en presence de couronne ou de cryptand. etude par spectrometrie infra-rouge et cinetique

The structure and the nucleophilic reactivity of crowned (18-crown-6) or cryptated {cryptand (2.2.2)} potassium ethyl acetoacetate enolate have been compared in tert-butanol and in DME (or THF). In the protic solvent tert-butanol, the crowned and the cryptated potassium enolate species both exist as loose ion pairs in which the enolate anion, strongly hydrogen-bonded to the solvent, is in a “transoid” (non chelating) conformation. Both species show similar reactivities towards alkylating agents but completely different reactivities are observed in aprotic weakly dissociating media (THF, DME). In contrast to what is observed in tert-butanol, the cryptated species and the crowned species have very different nucleophilic reactivities in THF or DME; in those solvents only the cryptated species retains a loose ion pair structure; the crowned species is a contact ion pair in which the enolate anion chelates the potassium cation. The solvation of this crowned chelate species by tert-butanol has been demonstrated in binary mixtures of solvents (C₆D₆-t-BuOH, THF-t-BuOH). The oxygen basicity of the enolate anion is very different in the crowned chelated ion pair compared with the cryptand separated ion pair.     

Dosage amperometrique rapide et directe de calcium et de magnesium dans l'eau,les ciments et le sol

An amperometric method for thé successive titration of calcium and magnesium with EGTA and EDTA respectively is proposed. The method is direct and rapid. Calcium and magnesium can be determined in waters (41.5 mg/l and 4.6 mg/l with a precision of ±1.15% and ±6.70%), in cements (66.7% CaO and 1.70% MgO with a precision of ±2% and ±8%), and in soils (16.5% CaCO₃ and 1.8% MgCO₃ with a precision of ±2.6% and ±5.5%). The results obtained are compared with those obtained by gravimetric or titrimctric methods.     

Polymerisation radiochimique de l'acide acrylique en solution dans l'alcool isopropylique et le dimethylformamide

The radiation-induced polymerization of acrylic acid in isopropyl alcohol and dimethylformamide solutions was investigated between?196°and40°. Mixtures which form glasses at low temperatures exhibit a maximum in the rate of polymerization at 30° and 50° above the glass transition temperature (T_g). The difference between the most favourable temperature for polymerization and T_g is larger than in systems studied previously. This fact could be due to the presence of H-bonded aggregates.The study of the polymerization of acrylic acid in dimethylformamide solution at 20° led to a correlation between this reaction and the presence of plurimolecular aggregates. The very high polymerization rate and the syndiotacticity of the resulting poly(acrylic acid) confirm the earlier assumption of a favourable orientation for propagation of the molecules of acrylic acid in these aggregates.     

Comparaison entre le role de l'eau et celui d'un ether couronne dans le cadre de la reaction de wittig realisee en milieu heterogene : liquide-solide

The similar results issued from the use of water and the 18-crown 6 ether for the Wittig reaction (in liquid-solid two-phase systems) allowed us to obtain very high yields in olefin starting from aromatic as well as aliphatic aldehydes.     

Synthese et etude de l'agregation moleculaire d'amines derivees de l'adamantane

Adamantanealkanamines were prepared by a new method: the wittig reaction of aminophosphonium ylides with 2-adamantanone. Conductance measurements have been employed to examine and compare the aggregation behaviour of these compounds.     

Essais d'analyse conformationnelle de cyclopentanols et de germacyclopentanols

The NMR spectra of cyclopentanols and germacyclopentanols have been recorded in the presence of Pr(DPM)₃ and analyzed. Using the induced chemical shifts and the coupling constants, preferred conformations are proposed for the cyclanols.     

L'isopolyalthenol et le neopolyalthenol,nouveaux indolosesquiterpenes isoles de Polyalthia suaveolens, annonacees

The novel indolosesquiterpenes isopolyalthenol 3 and neopolyalthenol 4 have been obtained from Polyalthia suaveolens (Annonaceae). A pathway for the biogenesis of indolosesquiterpenes is considered.     

Alcoylation des enolates de l'acetylacetate d'ethyle dans le dimethoxyethane. Reactivite des formes associee et dissociee

The alkylation of alkali metal and N⁺Bu₄ ethylacetoacetate énolates by means of ethyl iodide, bromide and tosylate has been studied in diméthoxyéthane, in order to measure the reactivity of the associated forms. C/O alkylation ratios, structures of O-alkylated products and rates of alkylation, have been determined. With ethyl tosylate, the amount of O-alkylated products does not increase in the generally observed order Li⁺ < Na⁺ < K⁺ < Cs⁺ but in the order Na⁺ < K⁺ < Li⁺ ≈ Cs⁺. Some aspects of the alkali ethylacetoacetate énolates reactivity in weakly polar medium such as DME are discussed.     

Etude de l'hydrogenation de l'α-terpinene et du dihyro-2,3 anisole catalysee par le phenanthrene chrome tricarbonyle

The hydrogenation of α-terpinene and 2,3-dihydroanisole catalysed by phenanthrenechromium tricarbonyl in cyclohexane is described. The catalytic reaction is accelerated when small amounts of ketone are added to the solution. Attempts to induce asymmetric synthesis by adding (+)-3-menthylcyclohexanone or l-carvone to the reaction mixture are discussed. Isomerization of cis-Δ²-methene and α-phellandrene is also presented.     

Synthese et configuration de l'alnincanone

Alnincanone 1, and its three diastereoisomers at C-20 and C-24, have been synthesized from dipterocarpol. The configuration of the four isomers has been defined by several independent methods; the naturally occurring alnincanone is 20S,24R.     

Syntheses d'oxazolidines substituees par l'adamantane et de nitroxydes oxazolidines stables derives de l'adamantane

Adamantane oxazolidine derivatives have been prepared. The corresponding mono and biradicals have molecular shapes well suited to the study of the motion anisotropy in solution.