Telomeres photoreticulables—1. Synthese de telomeres photoreticulables a partir du cinnamate et de l'acetate de vinyle

Photocrosslinkable telomers containing cinnamoyl groups can be prepared by two methods, viz, (i) direct telomerisation of vinyl cinnamate using either redox initiation (FeCl₃ benzoin-CuCl₂) or conventional radical initiation (benzoyl peroxide), and (ii) esterification of polyvinylalcohol telomers with cinnamoyl chloride. The former method gives products which are extensively cyclised, as indicated by i.r. and NMR spectra, whereas the latter method gives materials in which all the cinnamoyl groups are available for crosslinking.     

Determination de configuration de sulfoxydes cycliques par RMN discussion des differents criteres

The NMR spectra of various sulfoxides derived from thiophane or 4-tert-butyl thiacyclohexane are discussed. The different empirical rules commonly used to establish sulfoxides configuration (J_gem and Δν for an α-methylene group, syn-axial effect, benzene solvent shifts and Eu (dpm)₃ induced shifts) are critically examined, at the light of these experimental data. The conclusions of the NMR study agree with the structures obtained by X-ray analysis and chemical correlation.     

Synthese et etude par resonance magnetique nucleaire du carbone 13 et de l'etain 119 d'une serie de triorganostannyl-2 butanes

Optically active triorgano-2-stannylbutanes have been synthetized by different methods, one being the direct substitution of optically active s-butyl halides with triorganostannyl alkali metals. This route involves a complete or partial inversion of configuration at the chiral carbon atom. Carbon-13 and tin-119 NMR data are reported as support for the identification of eight triorgano-2-stannylbutanes. The special case of tetra(2-butyl)tin, with four identical chiral centres has been examined.     

Composés d'addition des halogénures de niobium(V) et de tantale(V) IV. Stabilité relative des composés de chlorures avec quelques nitriles

The relative stability constants of the adducts of MCl₅ (M ? Nb, Ta) with acetonitrile, halogenoacetonitriles, pivalonitrile, acrylonitrile and benzonitriles are determined in dilute solutions by NMR. methods. The stability of the adducts is controlled by inductive factors. Chemical shifts and analysis of the new compounds are reported.     

Constantes de couplage de vinylallènes

In order to define the influence of an allenic type conjugation, the NMR spectra of vinylallene and of some of its methyl derivatives are analysed The signs of the coupling constants are also determined. These compounds are characterised by a planar s-trans structure of the two noncumulated double bonds. A discussion of the parameters, and especially of the methyl replacement effects, evidences the importance of the π type contributions. The theoretical calculations of the coupling constants by the methods of finite perturbation CNDO and INDO corroborate this interpretation.     

Etudes configurationnelles et conformationnelles de quelques chlorures de désoxy-6 β-L-héxopyrannosyle chlorosulfonyles et de leurs glycosides de méthyle

A total analysis of the NMR spectra of 6-deoxy-L -hexopyranoses in the α-configuration and of the corresponding β-anomers was carried out. The parameters obtained are characteristic of a 1C (L ) chair conformation, having the anomeric substituent in an axial orientation for the methyl α-fuco-, α-rhamno- and α-chinovopyranosides and for the α-fuco- and α-rhamnopyranosyl chlorides. The structure is also of a 1C (L ) chair type for the methyl β-fuco- and β-chinovopyranosides; the geometry is the same for the β-fuco- and β-rhamnopyranosyl chlorides despite the anomeric effect of a chlorine atom. However, the NMR parameters of the β-chinovopyranosyl chloride are not explicable on the basis of a chair conformation with an equatorial chlorine or a boat structure.     

Composés d'addition des halogénures de niobium (V) et de tantale(V): III. Détermination de constantes de stabilité par résonance magnétique nucléaire

In view of a systematic study of the Lewis acidity of niobium (V) and tantalum (V) halides, NMR. methods for the determination of stability constants are discussed. In the case of rapid exchange chemical shifts are used to determine the relative amounts of adduct(s) and free base(s) in equilibrium. In the case of slow exchange the relative concentrations of the species are given by the peak areas.     

Application des relation de Mislow et Raban a la determination de configuration (mesothreo) par resonance magnetique nucleaire

The meso or threo configuration of diastereoisomeric molecules is elucidated on the basis of respective NMR spectra of either isomers. The symmetry relationship (according to Raban and Mislow) between protons or groups are not identical in each isomer, and the consequent differences in chemical shifts and spin-coupling constants permit assignment of configurations.     

Interactions Intramolécularies—XVII Calcul des constantes de couplage en RMN du cyclohexane et de cyclohexanes substitués. Comparaison des méthodes de Pople et Santry et des perturbations finies

Proton–proton ³J, ⁴J and ⁵J NMR coupling constants have been calculated for cyclohexane and monosubstituted cyclohexane conformers (substitiuents: Li, CH₃, OH, F) by the two methods mentioned. Comparing the two methods on the basis of group theory, we show the necessity to use the second. The results from this method are compared with those of the literature.     

Etude par RMN. de polyaminocarboxylates de terres rares,III. Hydroxyéthyliminodiacétates de praséodyme

¹H—NMR. has been used to study the chemistry of the hydroxyethyliminodiacetate complexes of praseodymium in aqueous solution. The ligand exchanges by spontaneous dissociation of the metal-bis-hydroxyethyliminodiacetate (1:2 complex) and of the metal-bis-hydroxyethyliminodiacetate hydroxocomplex, by acid catalysed dissociation of the 1:2 complex, and by a bimolecular process involving the free ligand and the 1:2 complex or the ternary hydroxo-complex. The ligand exchange rate constants are given and the mechanisms discussed.     

Etude par RMN d'une inversion de cycle de quelques benzodiazépinones

The NMR spectra of five benzodiazepinones are determined over a range of temperature. They indicate that the seven ring has a twist-boat shape, which inverts more or less rapidly according to the nature of substituents. The activation parameters and the rates of inversion are determined and the substituent effects are discussed.     

Etude par Résonance Magnétique Nucléaire de dioxaphosphorinanes-1,3,2 à liaison P?N extracyclique. Exemple de changement d'orientation de la liaison P?N

The ¹H NMR spectra of several 1,3,2-dioxaphosphorinanes bearing an extracyclic P? N bond have been analysed. The ³J(POCH) couplings are strongly dependent upon the orientation of the bond around the phosphorus atom. Depending upon the nature of the bonds attached to the nitrogen atom, the dioxaphosphorinane ring may adopt either a fixed chair conformation with the P? N bond in the axial or equatorial orientation, or it may be in equilibrium between two chair conformations where the P? N bond is alternately axial or equatorial. The equilibrium is fast on the NMR time scale.     

Essais d'analyse conformationnelle de cyclopentanols et de germacyclopentanols

The NMR spectra of cyclopentanols and germacyclopentanols have been recorded in the presence of Pr(DPM)₃ and analyzed. Using the induced chemical shifts and the coupling constants, preferred conformations are proposed for the cyclanols.     

Interpretation du Spectre RMN de l'Octaacetate de Cellobiose a 250 MHz. Application au Triacetate de Cellulose

Using a 250 MHz NMR spectrometer and double resonance experiments the full identification of the 14 cyclic protons of α octaacetate cellobiose has been performed. The results obtained here are of particular interest as affording an answer to the problem of the existence of particular signals in the NMR spectra of cellulose triacetate. These signals are both due to the anomeric extremity of the polymer.     

Synthese et etude de poly (esters insatures-seq-ethers)—I. Preparation de poly (esters insatures-seq-ethers) par polycondensation en solution

The preparation of ωω′ bisfunctional oligoesters (unsaturated or not) is described. The oligoesters are characterised by NMR, end-group titration and tonometry. Their modification by transformation of acid to acid chloride end-group is reported. Their solution polycondensation with ωω′ dihydroxy polyethers is described. A statistical method has been used to optimize the reaction conditions. The properties of the poly (unsaturated esters-b-ethers) are studied. Examination by thermal differential analysis shows that the two blocks are compatible.     

Chimie des complexes de metaux de transition avec des hydrocarbures cyanes : III. Quelques observations sur la conformation et la reactivite de complexes dicyclopentadienyles du molybdene et du tungstene

A new class of cyclic telluronium salts has been prepared. All the salts are stable in solution in CHCl₃ or dimethylsulphoxide (DMSO). Conductivity measurements in DMSO and dimethylformamide (DMF) have shown that considerable ion pairing occurs in solution. Infrared, ¹H, ¹³C, ¹²⁵Te NMR, and mass spectra are reported and discussed.     

Etude de la réactivité de la fonction carbonyle avec le cétène en présence d'un alcoxyde de titane. 2e communication. A propos de l'interprétation de quelques spectres RMN de β-hydroxyesters formés

The NMR. spectra of a serie of β-hydroxyesters have been studied. It has been found that the methylene protons are magnetically nonequivalent only when the substituents on the center of asymmetry of I or II are very different. The magnetically non-equivalence of the isopropylmethylprotons arise when the β-hydroxyesters contain an aromatic or aromatic conjugated group directly bonded to the asymmetric carbon. The interpretation of this finding is proposed.     

Synthese et etude par resonance magnetique nucleaire de complexes olefiniques de l''iridium et du rhodium avec quelques bases de schiff derivees de l''aldehyde salicylique

[M(bds)(cod)] compounds (M = Ir or Rh, cod = 1,5-cyclooctadiene, bds = Schiff's base) have been studied by ¹H and ¹³C NMR.

Signals corresponding to the atoms of the double bond trans to the oxygen atom appear at higher field than those of the trans nitrogen side. ¹ and ¹³C attributions have been related by selective decoupling. Some structural data have been also obtained.     

Structures de modeles de polyesters—I. Separation et etude par RMN [13C]des dihydroxy-2,3 butane, 2,4 pentane et 2,5 hexane et de leurs benzoates

[¹³C]NMR spectra have been obtained for a series of diols and benzoates, models of 2,3-dihydroxybutane, 2,4-dihydroxypentane and 2,5 dihydroxyhexane terephthalates after separation of diastereoisomers by gas and liquid-liquid chromatography. Chemical shifts for the meso and racemic derivatives have been interpreted in terms of rotational isomers. The results indicate that [¹³C]NMR is more sensitive than [¹H]NMR for the differentiation of diastereoisomers. Carbonyl and aromatic quaternary carbon chemical shifts are sensitive to the stereochemistry of the chain (long range effects) but relaxation times and nuclear Overhauser enhancements are identical in the two diastereoisomers.