Influence du cuivre sur la substitution des énolates stables par divers halogénures allyliques

The allylic substitution, by a variety of allylic halides, of stable enolates derived from diethyl malonate, ethyl cyanoacetate, ethyl acetoacetate and acetylacetone has been investigated. The yields and regioselectivity of these reactions are strongly influenced by cuprous ions (and their ligands).     

Étude des propriétés des mélanges pebd régénéré / pebd vierge

This study is a contribution to the valorization of recycled low-density polyéthyléne (LDPE). First the characterization of five recycled LDPE produced from wastes coming from different sources was performed. The physical properties (density, melt flow index), chemical structure (Fourier transform infra-red spectroscopy) and mechanical properties (tensile strength and hardness) were investigated. The effect of the ratio of virgin LDPE on these physical and mechanical properties was studied in the case of the blends of recycled LDPE / virgin LDPE.     

Étude des spectres vibrationnels des cyclotétraphosphates

The analysis of the infrared and Raman spectra of a number of cyclotetraphosphates shows that it is possible to characterize the cyclic anion P₄O⁴⁻₁₂. The number, positions and shapes of the infrared absorption bands observed in the symmetric stretching region provide an indication of the symmetry of the P₄O⁴⁻₁₂ ring in each compound.     

Microdosage rapide des halogènes dans les composés organiques

Résumé Une méthode des plus simples et des plus rapides de minéralisation des composés organiques en vue du dosage des halogènes est sans aucun doute l'attaque de ces substances par le peroxyde de sodium dans la microbombe deParr. Il convenait de lui associer une méthode ayant des qualités comparables pour le dosage ultérieur des halogènes ainsi minéralisés.La gravimétrie des précipités d'halogénures d'argent est longue et délicate et les facteurs de calcul deviennent défavorables pour le brome et surtout pour l'iode.Les méthodes volumétriques argentométriques sont rendues difficiles ou impossibles du fait de la haute concentration en sels des solutions d'ions halogènes.L'argentométrie potentiométrique a permis de doser à l'échelle semimicroanalytique les ions chlore et brome avec une solution de nitrate d'argent 0,02 N mesurée dans une macroburette. La haute concentration en sels ne permet pas, lorsqu'on utilise la méthode potentiométrique habituelle, de faire des dosages à l'échelle microanalytique; en outre cette méthode est encore de durée relativement longue.La méthode des potentiels d'équivalence repérés utilisée par l'auteur permet les dosages à l'échelle microanalytique de l'ion chlore avec une solution de nitrate d'argent 0,01 N, et des ions brome et iode avec une solution de nitrate d'argent 0,002 N, ces solutions étant mesurées dans une semi-microburette. Le faible titre de la solution de nitrate d'argent employée permet à cette méthode de concurrencer, pour l'iode, la méthode iodométrique au thiosulfate de sodium 0,01 N où l'on dose 6 équivalents d'iode pour un seul à déterminer. Cette méthode est, en outre, beaucoup plus rapide que les autres méthodes volumétriques y compris la méthode potentiométrique habituelle, et se prête, comme la minéralisation à la microbombe, aux dosages en grande série.

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Summary One of the most simple and most rapid methods of mineralizing organic compounds for the purpose of determining halogens is doubtless the attack of these materials by sodium peroxyde in theParr microbomb.A method having comparable qualities for the subsequent determination of the halogens thus mineralized is described here.The gravimetric determination of silver halide precipitates is long and delicate, and the factors become unfavorable for bromine and especially for iodine. The argentometric volumetric methods are made difficult or impossible because of the high concentration of salts in the halide solutions.Potentiometric argentometry provides a method of determining chloride and bromide on a semi-microanalytical scale by means of 0,02 N silver nitrate solution added from a macroburette. When the usual potentiometric method is employed, the high concentration of salts does not permit determinations on the microanalytical scale; furthermore this method still requires a considerable expenditure of time.The method of equivalence potentiale, used by the author, permits the determination, on the microanalytical scale, of chloride with 0,01 N silver nitrate solution, and of bromide and iodide with 0,002 N silver nitrate. These solutions are measured in a semi-microburette. The low titre of the silver nitrate solution used allows this method to compete for iodide, with the iodometric method (when 0,01 N sodium thiosulfate is used) where six equivalents are titrated for each equivalent being determined. Moreover, the present method is faster then the other volumetric methods including the ordinary potentiometric method, and lends itself, like the mineralization in the microbomb, to series determinations.

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Zusammenfassung Eine der einfachsten und raschesten Methoden der Veraschung organischer Substanzen für die Bestimmung der Halogene ist ohne Zweifel die mit Natriumperoxyd in derParr-Bombe. Es scheint zweckmäßig, sie mit einem ebenso zufriedenstellenden Verfahren für die eigentliche Halogenbestimmung zu kombinieren. Die Gravimetrie der Silberhalogenide ist langwierig und mißlich und deren Umrechnungsfaktoren insbesondere für Brom und Jod recht ungünstig. Die argentometrische Maßanalyse ist entweder schwierig oder gar nicht durchführbar in Gegenwart hoher Salzkonzentrationen. Im Halbmikromaßstab lassen sich Chlor und Brom mittels 0,02-n-Silbernitratlösung und Verwendung einer Makrobürette potentiometrisch titrieren. Hohe Salzkonzentration verhindert jedoch nach dem üblichen Verfahren den Übergang zum Mikromaßstab; im übrigen ist auch dieses Verfahren relativ langwierig. Die vom Verfasser angewendete Methode der gekennzeichneten Gleichgewichtspotentiale ermöglicht die maßanalytische Bestimmung der Chlorionen mittels 0,01-n-Silbernitrat, der Brom- und Jodionen mittels 0,002-n-Silbernitrat, wobei für diese Lösungen Halbmikrobüretten verwendet werden. Der niedere Titer der angewendeten Silberlösung läßt diese Methode der Jodbestimmung dem Multiplikationsverfahren mit 0,01-n-Thiosulfat gleichwertig erscheinen. Sie ist im übrigen viel rascher ausführbar als sonst übliche volumetrische und auch potentiometrische Methoden und läßt sich, kombiniert mit demParr-Verfahren, zur Serienbestimmung verwenden.

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Avec 4 figures.     

Étude critique des réactions des cations : Rhénium

For the reactions proposed for rhenium, the author is in agreement with the conclusions of the “Second Report” (wenger AND duckErt) with one exception, the microchemical test with pyridine seems preferable to that using acridine.     

Étude expérimentale des auto-oscillations d'un jet plan confiné au sein d'une cavité contenant un obstacle

We investigate the oscillation phenomena occurring when a two-dimensional plane jet emerges from a rectangular nozzle into a cavity with a body inside. It is shown that far from the lower oscillation limit, the frequencies of self-sustained oscillations are only governed by geometrical parameters. The evolutions of the Strouhal versus Reynolds number show that the effect of the geometry downstream the bluff-body is important for the control of the oscillation mechanism.     

Étude critique des réactions des cations : Nickel

The authors have tried out the spot tests suggested for the cation nickel between 1937 and 1947. After a critical examination they recommend following the details of the second Report as drawn up by WENGER AND DUCKERT, in particular the use of the dioxime of 1:2-cyclohexanedione, known commercially under the name nioxime.     

Étude critique des réactions des cations : Cobalt

The authors have critically examined the reactions proposed for cobalt between 1937 and 1947. Their findings are in agreement with the conclusions, of the second Report (wenger and duckert). However, the reaction with potassium cyanate can be replaced by the closely similar test, using sodium thosulpliate, a more accessible reagent, there is no interference; from copper, iron and nickel.     

Étude critique des réactions des cations : Uranium

A critical examination has been made of all drop reactions proposed for uranium during the period 1937–1917. In view of the preparation of the fourth Report, it is proposed to retain only the micro-chemical reaction given by an alkaline thiocyanate and sparteine, even in presence of a large excess of iron.     

Semi-micro determination de derives halogénés

The semi-micro estimation of halide derivatives using a method previou'ly described, is reported.The procedure is based on the hydrolysis with normal solution of potassium hydroxyde in diethylene glycol at 150--160° C. The hydrolysis is carried out in tubes scaled either with a flame or simply with a rubber stopper, according to the case, and is followed by the estimation of the halide thus formed.The method is described and the results obtained with several compounds are given.Application of the method to the qualitative distinction between aliphatic and aromatic halide derivatives is indicated.     

Échelles caractéristiques des domaines tourbillonnaires apparaissant près des irrégularités des frontières

The possibility of the formation of a vortex domain of finite size near complex boundaries is analysed. For the proposed model, when such a scenario is attainable, the curve configuration delimiting the non-zero vorticity domain is found. This curve represents an approximate solution of an integral-differential equation obtained using the proposed model. It is shown that the vorticity level is a function of the characteristic dimension of the vortex domain, which depends on the size of the obstacle and is a homogeneous function of the Reynolds number.     

Introduction a l'étude des sels basiques insolubles: Étude des courbes de précipitation des sels basiques insolubles. Produits de solubilité des sels basiques et des hydroxydes

A critical study of curves of precipitation of basic salts by alkali hydroxides shows that the irregularities observed on these curves do not always permit the deduction of the constitution of the salt. They indicate nevertheless the appearance of a new phase and this observation explains, in particular, the important number of wrongly defined basic salts which have been observed.The theory of the titre curves leads to the proposal of formulas permitting the calculation of solubility products of basic salts and even those of hydroxides which were determined very accurately by other methods.     

Étude du processus photochimique impliqué dans la réaction d'ouverture du cycle benzopyrannique des spiropyrannes photochromiques

The analysis of absorption and emission spectra of different hetero-cyclic spiropyrans leads us to question the previously accepted general assumption of intramolecular energy transfer from the heterocyclic part to the chromene part, and to consider the concept of spiroconjugation.The singlet and triplet excited states responsible for the photochemical opening of spiropyrans are of the ππ^* type with an intramolecular charge-transfer character. The participation of singlet or triplet states depends essentially on the nature of the heterocyclic moiety. In the indolinic series the photochemical reaction proceeds through the triplet state, whereas in the benzodithiolic series it occurs almost completely in the singlet state.     

Étude de la réactivité des radicaux α-ester : influence des centres stéréogènes en position α’ et β’

The formation of 2-syn and 2-anti addition products, between a 1-E olefin and an acyclic radical is under kinetic control, although addition of n-Bu₃Sn^• to the 1-Z leads to 1-E olefin. Hydride capture is often independent of the nature of the radical, but the difference of behaviour between A^• and B^• radicals results from their stability, induced by the existing chiral centres present in the molecule. Capture of the intermediate radical in α of the ester by deuterium occurs with a diastereomeric excess, varying between 30 and 78%, depending on the nature of the centres situated in α’ and β’ positions.