Etude de la reaction de lactonisation de l'acide ethylenedioxy-1,1 methyl-2 oxo-3 cyclopentane-2- propionique

The lactonisation of ethylene 1,1-dioxy 2-methyl 3-oxo cyclopentane-2 propionic acid has been affected by a new method whose mechanism is discussed. The formation of a β-diketone and other products by isomerisation of the enol lactone has been avoided. The enol lactone is an important intermediate in the total synthesis of steroids and has been prepared with a good yield by the new method.     

Fluoration de telomeres polyhalogenes par le fluorure de potassium (2ème partie). Synthese d'olefines perfluorees de hauts poids moleculaires

Fluorination of chlorofluorinated telomers of general formula Cl(CFClCF₂)_nCCl₃ (n ? 7) was studied using potassium fluoride in dimethylsulfoxide as fluorinating agent. The reaction leads to a mixture of perfluorinated linear olefins having 15 to 30 carbon atoms : CF₃(CF₂)_pCFCF(CF₂)_mCF₃ (p + m = 2n?3).We perfected a method to determine molecular weights of the telomers by gel permeation chromatography (G.P.C.). The olefins obtained by fluorination are analyzed both by vapor phase chromatography (V.P.C.) and by ¹⁹F nuclear magnetic resonance (N.M.R.).     

TELOMERISATION PAR CATALYSE REDOX IX ADDITION DE TELOGENES PHOSPHORES SUR DES COMPOSES POSSEDANT DEUX DOUBLES LIAISONS NON CONJUGUEES

Abstract

The synthesis of telechelic oligomers with phosphorated end groups was realized by redox catalysis telomerization reaction by addition of phosphorated telogens containing a trichloromethyl group on monomers with two non-conjugated double bonds.

Nous effectuons la synthèse d'oligoméres téléchéliques à extrémités phosphorées en additionnant au moyen de la réaction de télomerisation par catalyse Redox des télogènes phosphorés renfernant le groupement trichlorométhyle, sur des monomères à deux doubles liaisons non conjuguées.     

Telomerization kinetics by redox catalysis: A study of reactions leading to telomers with low degrees of polymerization

An adaptation of the David and Gosselain formula for redox catalyzed telomerization was made. An equation was developed for transfer reactions between oligomer radicals and metallic ions. This equation was applied to data obtained in chlorotrifluoroethylene (CTFE)—carbon tetrachloride telomerizations catalyzed by a ferric chloride—benzoin mixture. It was found that the metal ion transfer constants (C_Meⁱ) were the predominant parameters influencing the distribution of products obtained. These were found constant for degrees of polymerization greater than 2.     

Reactions de transcetalisation—I: Mise en evidence du caractere thermodynamique des reactions de transcetalisation et applications a la chimie de synthese

Evidence for the thermodynamic character of the transketalisation reaction allows the calculation of relative energies based upon ethyl methyl ketone. A scale of stability of the different types of ketones has thus been established and one can predict the selectivity of transketalisation reactions in polyketone molecules and hence choose the most suitable reagent. In the case of cyclic ketones, the variation of the transketalisation energies according to ring size has been related to changes in hybridation states.     

Telomerisation par catalyse redox—II. Telomerisation du styrene,de l'acrylonitrile,et du monochlorotrifluoroethylene par des telogenes chlores

A study has been made, under conditions for telomerization catalysed by a redox system, of the reactivities of styrene, acrylonitrile and monochlorotrifluoroethylene with respect to some telogens viz various chloroethanes, methyl trichloroacetate, CCl₂F.CClF₂ and CClF₂.CClF1. Generally, the selected catalyst system led only to products of monoaddition; these products were isolated and identified.     

Proton and calcium-gated ionic mesochannels: phosphate-bearing polymer brushes hosted in mesoporous thin films as biomimetic interfacial architectures

Rational construction of interfaces based on multicomponent responsive systems in which molecular transport is mediated by structures of nanoscale dimensions has become a very fertile research area in biomimetic supramolecular chemistry. Herein, we describe the creation of hybrid mesostructured interfaces with reversible gate-like transport properties that can be controlled by chemical inputs, such as protons or calcium ions. This was accomplished by taking advantage of the surface-initiated polymerization of 2-(methacryloyloxy)ethyl phosphate (MEP) monomer units into and onto mesoporous silica thin films. In this way, phosphate-bearing polymer brushes were used as "gatekeepers" located not only on the outer surface of mesoporous thin films but also in the inner environment of the porous scaffold. Pore-confined PMEP brushes respond to the external triggering chemical signals not only by altering their physicochemical properties but also by switching the transport properties of the mesoporous film. The ion-gate response/operation was based on the protonation and/or chelation of phosphate monomer units in which the polymer brush works as an off-on switch in response to the presence of protons or Ca(2+) ions. The hybrid meso-architectured interface and their functional features were studied by a combination of experimental techniques including ellipso-porosimetry, cyclic voltammetry, X-ray reflectivity, grazing incidence small-angle X-ray scattering, X-ray photoelectron spectroscopy, and in situ atomic force microscopy. In this context, we believe that the integration of stimuli-responsive polymer brushes into nanoscopic supramolecular architectures would provide new routes toward multifunctional biomimetic nanosystems displaying transport properties similar to those encountered in biological ligand-gated ion channels.