Cinetique complexe de l'halogenation de cetones en milieu acide—II : Controle par la diffusion des vitesses d'halogenation des enols-consequences

The kinetics of the bromination and chlorination of acetone, diethylketone and di-isopropylketone (bromination only) have been studied at [X₂]_a^o ≈ 10^?7 to 10^?5 M; the apparent rate constants k_II^X₂ = K_Ek₂^X₂ (where K_E is the keto-enol equilibrium constant) for iodination, bromination and chlorination are approximately equal. This result is attributed to diffusion-controlled kinetics. The order of magnitude of such a limiting rate constant, 10⁹ M^?1s^?1 calculated from Smoluchowski's equation, leads to new values for K_E in solution (1·5 x 10^?8 for acetone) much smaller than those in the literature. The rate constants derived for enol ketonisation are then in good agreement with those from proton addition to the corresponding enol ethers.     

Étude de l'erreur acide de l'électrode de verre en milieu aqueux: Tome II. Solutions d'acides purs

The acid error of glass electrode is studied in pure acid solutions of different natures by direct comparison with hydrogen electrode. This deviation from the hydrogen function is depending on the nature of both the acid involved and the glass electrode used. The potential of this electrode can be expressed by an empirical formula where two parameters appear: one of them is inversely proportional to molar weight of acid, while the other one is also dependent on the glass electrode used.     

Etude de l'effet stérique en chimie organique au moyen du volume d'activation. : Etude de l'influence de la pression dans les copolymérisations de l'anhydride maléique avec des éthylèniques substitués

The concept of activation volume derived from high pressure kinetics is shown to be an interesting parameter for the investigation of crowded transition states. In the free radical copolymerisation of maleic anhydride with mono- and poly-substituted olefins, increasing substitution of the comonomer involves greater pressure acceleration and hence more negative activation volumes and later transition states. This result may be of substantial synthetic importance. The concept of steric activation volume is introduced and a linear relationship between ΔV^≠_σ and the size of the substituent is developed.     

Étude d'équilibres en solution à l'aide des échangeurs d'ions : I Dissociation du perchlorate d'argent et de l'acide nitrique dans les mélanges eau—acide acétique—acide perchlorique ou acide nitrique

A theoretical relationship postulated between the distribution coefficient of a monovalent element and the parameters upon which it depends (acid concentration in solution, dissociation constants of the acid and the salt, selectivity coefficient of exchanged ions) has been verified for the dissociation of silver perchlorate in water—acetic acid—perchloric acid mixtures. The dissociation constants found have been compared with the experimental values obtained by potentiometric measurements. The relationship established has been employed for the determination of nitric acid dissociation constants in water—acetic acid-nitric acid mixtures containing less than 25 % by weight of water. From the results the pK value for nitric acid in pure acetic acid has been evaluated by extrapolation. The theoretical relationship might be used to determine an acid dissociation constant when the dissociation constant of a salt is known and vice versa.     

Analyse conformationnelle a l'aide de la notation des angles de torsion—II: Controle conformationnel de l'ouverture de monoepoxydes de dienes cisoides et transoides s'effectuant avec deplacement allylique de l'olefine

Taking advantage of the torsion angle notation and using only the assumption of the maintenance of orbital overlap during the reaction it is possible to analyse and interpret the steric course of the 1,4-opening of cisoïd and transoïd diene monooxide incorporated in mono or polycyclic structures. The stereochemistry of the reverse reaction, corresponding to diene monoepoxide formation from a γ-bromo-α,β-unsaturated-cyclohexanol can also be predicted.     

Étude de l'erreur acide de l'électrode de verre en milieu aqueux: Tome III. Solutions mixtes d'acide et de sel alcalin

The acid error of the glass electrode is studied in mixed solutions of acid and alkaline salt with common anion. Measurements have been made by direct comparison with the hydrogen electrode. The experimental results confirm the view that the acid error arises from anion penetration into the glass. An empirical equation is proposed in which this error is expressed in terms of cation concentration in mixed solution.     

Synthese et etude de celluloses echangeuses d'ions. Leur emploi dans l'epuration des eaux residuaires de l'industrie textile-III: Traitement des eaux residuaires de l'industrie textile par une cellulose greffee par des chaines d'acide polyacrylique et par une cellulose renfermant des fonctions ammonium quaternaire

Modified celluloses previously described have been studied for ability to remove colour from the effluents of textile industry. The lowest dye concentration for which the celluloses are efficient are far below the lowest concentrations in effluents. It appears that the modified celluloses are more efficient than carbon black and are well adapted for the purification of pretreated or rinsing waters. Their abilities to extract surfactants from effluents and so to break emulsions of water with solvents have been examined and appear to be large. The treated waters can be recycled.     

Rearrangements des halohydrines en presence de carbonate d'argent sur celite-II: Halohydrines cyclohexaniques substituees

Silver carbonate on Celite reacts with trans-diaxial halohydrins of the cyclohexane series, giving epoxides. cis-Bromohydrins, where the bromine atom is axial, lead to ketones.     

Stereochimie de la des benzoates d'argent sur des diesters iododesoxy ns: I- Action des benzoates d'argent sur des di-o-aroyl-1,2 iododesoxy-3 ns-glycerols

The stereochemistry of the reaction of silver benzoates on chiral di-O-aroyl-1,2 iododeoxy-3-sn-glycerols has been reinvestigated. The reaction proceeds either with or without neighbouring group participation, depending on : - possible electrophilic assistance by the silver ion to the ionisation of the substrate (occuring only with dissociated silver salts), - ability of substituants R¹ and R² on the substrates to stabilize a positive charge. Rearrangements are at minimum with R¹ and R² electronreleasing groups in the substrate, silver salts un-or weakly dissociated and bearing a good nucleophile. For one case, a regio- and stereo specific reaction is observed.     

Cinetique complexe de l'halogenation de cetones en milieu acide—I : Iodation des enols

The kinetics of the iodination of acetone, diethylketone and di-isopropylketone in aqueous media ([H₂SO₄] = 0·1 to 1·0 N; [I₂]_a^o = 10^?7 to 10^?5M) have been studied by couloamperometry under irreversible conditions. At these concentrations the rates of formation of the enol and of its iodination are similar. The general equation, which assumes the steady state approximation for the enol, is applicable, and is used to separate the rate constants of enolisation (k₁) and the apparent enol iodination rate constant (k_II^I₂ = K_Ek₂^I₂). For acetone, the value given by Schwarzenbach for the enol equilibrium constant (K_E = 2·5 x 10^?6) leads to an elementary rate constant for the addition of iodine to the enol (k₂^I₂ = 6·5 x 10⁶ M^?1s^?1). This value is not, however, consistent with k_I2 = 1·5 x 10⁸ M^?1s^?1, the rate constant for the iodination of the corresponding ether 2-ethoxypropene.     

Étude thermodynamique de la complexation des lanthanides trivalents avec l'acide hydroxyethyl-ethylenediaminetriacetique et d'autres acides aminoacetiques: III. Détermination des Constantes de Formation des Complexes Mixtes par Titrage Potentiométrique

A thermodyrmmic study of the complex formation of trivaient lanthanides with hydroxyethylethyienediaminetriacetic acid and other aminoacetic acids. Part III. The determination of the formation constants of mixed complexes by potentiometric titration.The partial stability constants of the mixed and 1:2 complexes Ln—HEDTA—L (where Ln = La, Ce,... and L = glycine, IMDA, NTA, HEDTA and EDTA) have been determined by potentiometric titration at 25°C and at a constant ionic strength of 1 (KCl). The changes in stability of the complexes studied (1:1, 1:2, mixed, protonated and unprotonated) vs. atomic number of the lanthanide are discussed. The changes observed in the trends of the partial and overall stability constants across the lanthanide series are attributed to the decrease in the number of water molecules in the 1:1 LnHEDTA ·xH₂O from x = 3 for light lanthanides to x = 2 for heavy ones. However, in this 1:1 complex, HEDTA seems to be a hexadeutate ligand in the La—Sm range of the series and a pentadentate ligand in the Gd—Lu range. Significant differences have been found between the complexes containing four nitrogen atoms, i.e. L = HEDTA, EDTA, and those with three nitrogen atoms i.e. L = glycine, IMDA, NTA.     

Catalyse micellaire—I: Etude de la réactivite en milieu micellaire a l'aide de reactions compétitives

The limitations of macroscopic models of micellar solutions are revealed by thermodynamic and kinetic studies of micellar catalysis and in fact the properties of such media are essentially dependent on the microscopic organization. The micellar effects of CTAB [C₁₆H₃₃N⁺(CH₃)₃Br^?] and SDS (C₁₂H₂₅SO₄^?Na⁺) on the competitive reactions (S_N1, S_N2 and E2) of 1-bromo-2-phenyl propane in basic medium and on the alkaline and neutral hydrolysis of α-phénylallylic esters has been studied. The specific effect of the micellar microenvironment is shown. The results are interpreted in terms of an enhancement of the nucleophilicity of the hydroxide ion and a diminution of the nucleophilic and electrophilic properties of water. The variation of the catalytic effect of cationic micelles with the concentration of the nucleophilic reagent is discussed.     

Utilisation de l'effet overhauser,des mesures de relaxation en RMN 1H et des deplacements chimiques en RMN 13C dans l'etude de la conformation des amides—II: Application a l'etude conformationnelle d'amides alicycliques: acyl-prolines

¹H and ¹³C chemical shifts in the two decoalesced rotamers of the deuteromethyl ester of N-acetyl-l-proline are established by use of NOE and relaxation measurements. This requires the previous determination of the rotational barrier ΔG_c^≠ and the measurement of the relaxation times T₁ of the α-proton in the two conformers. The observed results reinforce the previous structural conclusions inferred from ¹³C studies on several acyl l-prolines and hydroxy l-prolines. The introduction of an acyl group in the prolines does not affect the different carbon atoms of the cycle in the two rotamers in the same way. These results can be interpreted in terms of electric field effects by the examination of X-Pro dipeptides with the N-terminal amino group shifted from α (COCH₂NH₂) to δ position (CO(CH₂)₄NH₂).     

Synthese et etude de celluloses echangeuses d'ions. Leur emploi dans l'epuration des eaux residuaires de l'industrie textile—1: Synthese d'une cellulose greffee par des chaines poly (acide acrylique) et d'une cellulose renfermant des fonctions ammonium quaternaire

For use as ion exchangers and particularly as purification agents for textile industrial effluents, cellulose grafted with polyacrylic acid and cellulose substituted by quaternary ammonium functions have been prepared. For both syntheses, the influences of experimental parameters have been studied in detail and the optimum conditions for large-scale preparation have been determined. Large amounts of modified cellulose have been obtained and tested in industry (cf. part III). The grafting by acrylic acid has been carried out by the ceric-ion method; the quaternary ammonium cellulose has been obtained by condensation of cellulose with epoxy propyl triethyl ammonium chloride. Synthesis of this salt in the presence of cellulose has been achieved so that the quaternary ammonium cellulose can be obtained from cellulose and epichlorhydrin in one step.