Alcoylation par l'iodure de butyle,de l'enolate de tetrabutylammonium de l'acetylacetone; nature de l'entite reagissante

The alkylation of tetrabutylammonium acetylacetonate with butyl iodide was studied in order to specify the nature of the reactive anionic species during the nucleophilic reaction of an ambident anion, under similar conditions to those of phase transfer catalysis. The C/O alkylation ratio changes with neither the solvents nor the enolate concentration; however k_obs, varies with the solvent but does not depend on the énolate concentration. The results and spectrophotometric UV data show that only one reactive species, the ion-pair, is involved.     

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.     

Etude de l'action de l'ion fluor sur la laquethorium-spadns

The reaction of fluoride with thorium—SPADNS lake was studied in detail with particular reference to the effects of pH and media. Two methods for the determination of microgram amounts of fluoride based on the reaction are described. The spectrophotometric method developed is more suitable for routine use, but the colorimetric titration method is less sensitive to the effect of large amounts of electrolyte.     

Etude theorique de la cycloaddition de l'ozone sur l'ethylene

A theoretical study of the cycloaddition of ozone on ethylene has been carried out by the LCAO-SCF-MO method. The potential energy hypersurface for the reaction has been investigated and the electronic and energetic properties of the transition state have been determined.     

Isolement de l'acide 3-amino 12-methyl tetradecanoique et de l'acide 3-amino 12-methyl tridecanoique a partir de l'iturine,antibiotique de Bacillus subtilis

lturin, a peptide antibiotic from Bacillus subtilis, was separated into three iturins: A, B, C by thin-layer chromatography. Iturin A, which has an antifungal activity, contains Asp, Glu, Tyr, Ser, Pro in a molar ratio 3:1:1:1:1 and a lipid moiety AL. The latter was shown to be a mixture of C₁₄ (40%) and C₁₅, (60%) amino-acids. The structure of these was determined by combined gas chromatography-mass spectrometry of the N-acetylmethyl esters. Strong peaks at m/e = 144 and m/e = 102 indicate a β-amino group. Identification of acetone and methylethylketone after chromic acid oxidation indicates an iso and anteiso structure. After comparison of the natural amino-acids with synthetic 3-amino pentadecanoic acid it is concluded that the lipid AL is a mixture of 3-amino 12- methyltetradecanoic acid and 3-amino 12-methyltridecanoic acid.     

Sinthese de copolymeres sequences de l'acetate de vinyle et de l'acrylate d'ethyle par telomerisation

A new two-step procedure for the synthesis of ethyl acrylate - vinyl acetate block copolymers is described : the first stage is the telomerisation of ethyl acrylate with carbon tetrachloride by redox catalysis, the second being another telomerisation of vinyl acetate, using the trichloromethyl end group of the first block as the telogen agent, with peroxydic initiation.     

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.     

Effet α. influence de la substitution sur l'exaltation de reactivite d'oximes vis-a-vis de l'acetate de p-nitrophenyle

Kinetic measurements show the relation between the magnitude of the “α effect” exhibited by trifluoromethyloximate anions RR'C=N-O^? and the electron attracting properties of the substituents. Indeed, the reactivity enhancement which is observed for α-trifluoromethyloximes is similar to that found in earlier studies of α-hydroxyiminoketones. This characteristic behaviour is no longer observed for oximes bearing an electron releasing substituent at the α-position of the hydroxyimino group. On the basis of sodium oximate molecular orbital energies the “α effect” induced by electron attracting substituents appears to depend on both the interactions of nitrogen and oxygen lone pairs of electrons and the lowering of the π^* vacant orbital thus favouring a secondary interaction between the π^* anion orbital and the π orbital of p-nitrophenylacetate carbonyl group.     

Dosage colorimetrique de traces de zinc dans la bauxite,l'alumine et l'aluminium raffine

A method for the colorimetric determination of traces of zinc in bauxite, alumina, and refined aluminium by means of dithizone is proposed. Ga, Fe, Si, Ti, Ni, Pb, Ca, Mg, Na, etc. do not interfere; Co interferes but can be masked with cyanide. The limit of sensitivity of the method is 2 p.p.m. for bauxite and alumina and 0.4 p.p.m. for aluminium.     

Oxydation chromique de l'adamantanone : preparation de l'acetoxy-5 adamantanone-2

chromic oxidation of adamantanone gives adamantane-2,6-dione (20%), 5-hydroxy adamantan-2-one (6%) and 5-acetoxy adamantan-2-one (36%).     

Effets de complexation de l'ester lors de la catalyse par l'eau ou les sels de l'hydrolyse alcaline des esters maloniques: etude cinetique,spectroscop

When water or salts are added, catalytic effects on alkaline hydrolysis of malonic esters in methanol are observed; they are definitely greater than those observed with monoesters. Kinetic data in the presence of salts suggest that ester-M⁺ complexation phenomena is predominant and prevails over HO^-, M⁺ ionic association. Infrared and Raman spectra of esters in water-alcohol mixtures, with or without added salts, indicate the formation of 1:1 and 1:2 complexes with each carbonyl of the diester and one proton donor molecule as well as with Li⁺.Ab initio calculations of these diesters and of their complexes allow the estimation of the positive charge density at the carbonyl group carbon as well as the LUMO energy levels; they lead to an interpretation of these entities reactivities according to perturbation theory. Only orbital control of alkaline hydrolysis of esters gives an account of the relative reactivities of mono- and diesters with or without added salts. The only consideration of charges at the carbonyl carbon is, on the other hand, inadequate for justifying all the observed phenomena.     

Structure de l'iturine C de Bacillus subtilis

The hydrolysate of iturin C contains α-aminoacids and liposoluble β-aminoacids in the same molar ratios as in iturin A. Electrophoretic migration and alkaline titration indicate the presence of one carboxyl group in iturin C. The reduction of iturin C with diborane shows that this carboxyl group in in an aspartyl residue. The sequence was determined by mass spectrometry of permethylated iturin C in comparison with mass spectrometry of permethylated iturin A. The aspartyl residue is linked to the carboxyl group of the β-aminoacid. In addition, a liposoluble compound seryl→β-aminoacid was isolated from partial hydrolysis which confirmed the cyclic structure of iturin C. In contrast to iturin A, iturin C has no antibiotic activity.     

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.     

Etude de l'equilibre entre l'oxyde de nickel et l'oxygene. Essai d'interpretation des lois de variation de la conductivite electrique en fonction de la temperature

In a previous paper we have shown that at 740°C and under an oxygen pressure less than 1,3 torr the electrical conductance G of a NiO powder reaches rapidly an apparently stabilized signal G_i which sharply decreases after a sufficiently long time to a G₀ value independent of P_O2.From this observation we have studied the influence of the temperature successively on the electrical conductance G_i and G₀. The Arrhenius law is only verified for the G₀ = f(T) curve. G₀ appears as the representative value of the gas-solid equilibrium.     

Structure de l'echitamidine,d'un stereoisomere et de deux regioisomeres

The relative configuration of echitamidine is established by spectral and X-ray crystallographic techniques. Three other isomers are described and a structure is proposed for them.