Effet du dimethyl-sulfoxyde sur les differentes etapes de l'hydrolyse alcaline d'acetanilides a groupe acyle active par des substituants electro-attracteurs

DMSO affects the alkaline hydrolysis of acyl-activated anilides through a rate decrease of direct decomposition of the tetrahedral intermediate, a rate increase or decrease, according to basicity of the leaving group, of hydroxide catalysed decomposition of the tetrahedral intermediate, and a preferential orientation toward this step.     

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.     

Action des sulfonyloxaziridines sur une imine. Obtention d'une nitrone par transfert regioselectif de l'oxygene sur l'azote

A pyrrolinic imine has been found to react concurrently with the nitrogen or the oxygen of a $\text{N}$-sulfonyl oxaziridine leading to a N-sulfonyl diaziridine and a nitrone respectively. By contrast an oxaziridine is obtained with a peracid. A possible relation between the regioselectivity of the oxygen transfer and the nature of the reagent is outlined.     

Separation des alcalino-terreux par l'edta sur resine echangeuse d'ions

The quantitative separation of a few mg of strontium and barium from several g of calcium is described. The alkaline earth carbonates are dissolved in 0.1 M EDTA, fixed at pH 4.8 on an ammoniacal Dowex column, and eluted, also with 0.1 M EDTA, calcium at pH 5.25, strontium at pH 6.0, barium at pH 9.0. The end of the calcium elution can be followed accurately by a sudden pH increase in the eluate(from 4.8 upto 5.25).     

Etude du mecanisme de l'hydrolyse alcaline des N-methyl acetanilides au moyen des effets de milieu

N-methyl acetanilides alkaline hydrolysis mechanism has been studied by means of solvent effect (DMSO and ²H₂O) and of structure-reactivity correlation (log k_obs = f(pK_{B aniline})). Our results are consistent with HO^? rate determining attack only for p-nitro anilide and with a rate determining water assisted decomposition of the tetrahedral intermediate for X  p-CH₃O, H, p-Cl, m-Cl.     

Effets de sel sur les mecanismes competitifs de coupure alkyle-oxygene et acyleoxygene lors de l'hydrolyse des esters phenylallyliques en milieu neutre

Salt effects on neutral hydrolysis of α-phenylallyl esters were determined in ethanol-water mixtures. Our results suggest weakening of alkyl-oxygen bond induced by complexation of carbonyl oxygen with the cation and with competition between ester-cation and ester-solvent association. The rate coefficient for hydrolysis of O-alkyl and O-acyl fission depends on water concentration and on cation. When ester-cation association is strong (Ba²⁺ and Li⁺) salt effect is positive; when it is weak, (Na⁺), salt effect is sometimes positive, sometimes negative and changes with the nature of the anion for alkyl-oxygen fission.     

Transposition des oxirannes-ethanols par l'intermediaire d'alcoxyetains. Influence de la configuration de l'oxiranne

The transposition of oxirane-ethanols, through alkoxytin compounds, into oxetane-2-methanols and/or oxolan-3-ols (tetrahydrofuran-3-ols) is dependent upon the oxirane configuration. Cis configuration is more suitable for the formation of the smallest ring. Steric hindrance is not sufficient enough to explain the results.     

Forme des cristallites d'oxyde de cadmium produits par decomposition de l'hydroxyde

The structural transformation that occurs in the cadmium hydroxide decomposition reaction has the morphological and crystallographic character of a martensitic transformation. The authors predict the shape of the oxide crystallites produced during the reaction, viz., small platelets developed parallel to the (111) oxide planes. The difficulty in assessing their shape by analysis of X-ray diffraction line profiles is discussed. Electron microscope and X-ray diffraction results are presented and it is shown that the oxide crystallite shape is dependent on whether the precursor is hydroxide or carbonate.     

Decomposition d'hypobromites prepares par action de l'oxyde de mercure et du brome sur des alcools bicycliques pontes

Hydrobromites of bridged bicyclic alcohols have been decomposed to yield tetrahydrofuran-type ethers as well as fragmentation products. The latter results from the cleavage of the carbon-carbon bond α, β to the hydroxyl group. In the case of 3-hydroxy-3-methyl bicyclo[3.2.1]octane, conjugated ketones and brominated olefins are formed, whereas tetrahydrofuran-type ethers are formed only under different experimental conditions different from those applicable to general cases. The reaction mechanisms have been established. The influence of the various reaction parameters has been studied in order to obtain selectively either tetrahydrofuran-type ethers or a mixture of conjugated ketones and brominated olefins.     

Influence des substituants sur l'activite catalytique des composes arene-chrome tricarbonyle,mise en evidence de l'imfortance d'un α-heteroatome (O,N)

Substituents bearing a heteroatom in α position to an Cr(CO)₃-complexed arene group induce a strong perturbation in the six-electron ligand—metal bond allowing an increased catalytic effiency of these derivatives under mild conditions.     

Sur la reactivite des organomagnesiens derivant de l'addition d'organomagnesiens allyliques sur l'isoprene

Contrary to a recent report, it is shown that allylic Grignard reagents prepared by treating allylic Grignard reagents with isoprene and a catalytic amount of Cp₂TiCl₂ react normally with carbon dioxide and carbonyl compounds: a complete allylic rearrangement is observed.     

Transposition des oxirannes-ethanols par l'intermediaire d'alcoxyetains

Oxiraneethoxytributyltins prepared from the corresponding oxiraneethanols, on heating at ～ 200° gave, after demetalation with isophthallic acid, 2-oxetanemethanols and/or 3-oxolanols. As appears from about thirty rearrangements the choice between oxetane and oxolane formation is dependent on: (1) the relative degree of substitution of the oxirane ring; cyclization occuring predominantly at the more substituted carbon; and (2) the configuration of the oxirane ring, when both its ends are equally substituted; cis form being more suitable for generation of the smaller ring. The reaction is shown to proceed with inversion of configuration at the site of oxygen attack. The results of attempts to perform the rearrangement in dilute-phase or through alkaline metal alkoxides in various media support the conclusion that there is a large contribution by electrophilic assistance to the oxirane opening. Such assistance can be efficiently provided by a tin atom in a push-pull mechanism which accomodates all the facts. The present method of oxiraneethanol rearrangement may offer a convenient route to functional oxetanes.