Low-frequency vibrations of molecular solids: XV. Globular molecule 1,2-dichloroethane

The far infrared and Raman spectra of polycrystalline 1,2-dichloroethane and 1,2-dichloroethane-d₄ for the low temperature modification have been measured from 450 to 33 cm⁻¹ at various temperatures from −100 to −182°C. Raman spectra of the high temperature crystalline modification for both samples were also investigated. The Raman data are in conflict with those previously reported. Assignments are made for the lattice vibrations in terms of the crystallographic unit cell C_2h⁵ (P_21/c) with two molecules per unit cell. The spectra of the high temperature modification are consistent with those expected for orientationally disordered crystals.     

Phosphoramidite approach for the synthesis of cardiolipin

A phosphoramidite approach was utilized for the first time to synthesize cardiolipin. Optically active 1,2-di-O-acyl-sn-glycerol was coupled with 2-O-protected glycerols utilizing mono- and bifunctional phosphitylating agents to yield, after final removal of protecting groups, the title compound.     

Proprietes viscoelastiques de quelques polyolefines. Influence du nombre et de la taille des chaines laterales sur la relaxation β

The influence of branching in polyethylene and of the alkyl-group R in polyolefins -(CH₂-CHR)_x- has been shown. The source of the relaxation can be first attributed to restricted movements of units in branches and eventually to the adjacent moving methylene groups in the main amorphous chain, and then to a wide spread movement of amorphous chains caused by the R-groups. The vibration of R-groups of a definite length {(3 carbons)} bound to the crystalline regions but rejected in the amorphous phase is superimposed on the first type of movement.     

Etude de la compatibilite des systemes binaires constitues par le polychlorure de vinyle et polyacetate de vinyle—IV: L'influence de la masse moleculaire sur la compatibilite du systeme PVC/PV AC

Using kinetic thermogravimetry and phase-contrast microscopy, a study has been made on the influence of molecular weight upon compatibility in the solid state for the system PVC/PVAc. For the extreme mixtures 80 PVC/20 PVAc and 20 PVC/80 PVAc, completely different behaviour is shown; the thermal stability of the former is much greater and that of the latter much less than would be expected on the basis additivity. From the results for the various systems, an attempt is made to classify mixtures of solid polymers.     

Etudes sur le mecanisme de la metathese des olefines : III. Intermediaires tungstacyclopentaniques et tungstacyclobutaniques

With a view to understanding the role of the catalyst in olefin metathesis various attempts were made to synthesize possible intermediates of the reaction. No compound was formed which could account satisfactorily for a metathesis reaction under conditions favourable for the formation of tungstacyclopentane. Attempted synthesis of tungstacyclobutane also failed, but gave results which could be interpreted as mimicking metathesis. In spite of this apparent agreement, it is concluded that, if tungstacyclobutanes are actually formed, they are decomposed to tungstacarbene (alkylidenetungsten) and olefins rather than to tungstacyclopentanes, then to olefins.     

Reaction de fixation de HX sur les systemes paraquinoniques—II : Etude de l'addition de HCl sur la parabenzoquinone oxime-4 et la chloro-2 parabenzoquinone oxime-4

HCl addition to parabenzoquinone oxime-4 yields chloro aminophenols and anisols differently substituted according to the nature of solvent (ether or methanol). Semi-empirical calculations give a good interpretation of experimental results.     

Influence de la temperature et du gradient de vitesse sur la viscosite des solutions diluees de xanthane

The dependence of the relative viscosity of a dilute xanthan solution (0.4 g·l^?1) has been studied as a function of temperature (20–70°) and of the ionic strength of the solvent. When the rate of shear exceeds 100 sec^?1, the viscosity can be expressed as γ̊ the exponent (n ? 1) varies with the polymer conformation. In aqueous solution in the absence or in the presence of added salt at a temperature above the melting temperature T_M (depending on the ionic strength of the solvent), the exponent (n ? 1) is ?0.285 and corresponds to the unordered conformation; at temperatures below T_M, the local helical conformation is rigid and (n ? 1) is ～ ?0.44 almost independent of the temperature.     

Etude des réactions pericycliques sous pression—II: Contribution a l'etude du mecanisme de la reaction de Diels-Alder

The kinetics of three Diels-Alder reactions have been investigated under pressures up to 10,000 kg/cm². The determination of the activation volume shows that its value is nearly the same as the total volume change of the reaction. This enables us to elucidate the mechanism as one step concerted characterized by a “quasi-cyclic” transition state with simultaneous formation of two covalent bonds.     

Conformation of non-aromatic ring compounds: Part 77. The molecular structure of gaseous 1,1-dimethylcyclohexane; an electron diffraction study

The gas-phase molecular structure of 1,1-dimethylcyclohexane has been investigated by the electron diffraction technique. The results confirm the prediction of valence force calculations, viz., axial substitution causes a flattening (Φ_av = 51.7°) of the chair form of the cyclohexane ring.     

Etudes sur le mecanisme de la metathese des olefines : IV. Echanges d'hydrure et carbenes

The possibility of exchanging hydrogen atoms between the catalyst and the substrate in olefin metathesis was examined. Exchange was observed at a high catalyst/olefin ratio, although virtually no exchange was observed at low ratio, Alkylidenetungsten, formed from WCl₆ and dimetallic derivatives of methane (i.e. CH₂M₂), proved to be efficient catalysts for olefin metathesis. It was concluded from these experiments and from those described earlier that olefin metathesis takes place by addition of an alkylidenetungsten to an olefin followed by fission of the resulting cyclobutane. A solution was proposed to the question raised by the Chauvin mechanism, namely the initiation, which was linked to the formation of alkyltungsten by addition of alkyl- or hydrido-tungten to olefins, followed by appropriate transformation to alkylidenetungsten compounds.     

Dilactams. Synthesis of nonsymmetrical dibenzodiazocinediones

We report the first examples of nonsymmetrical dibenzodiazocinediones, mono-, di-, tri- and tetra-substituted in the aromatic rings including a benzo pyridino diazocine, by a new short method without the requirement of protection. The procedure involves conversion of an anthranilic acid to its sulfinamide lactone followed by direct heating with a different N-alkylanthranilic acid.     

Détermination du champ de force de valence de l'ion : Son apport dans l'étude de la conformation

A valence force field for α-glycine is proposed and normal modes of vibration are discussed. The study of the small isotopic shifts of ¹⁵N and ¹⁸O is shown to be fundamental in the determination of the force field. There is a quantitative relationship between the isotopic shifts observed on low frequency absorptions and molecular conformation. The perturbations of the ion force field from one crystalline form to another and from solid state to aqueous solution are also discussed.     

Gas phase characterization by photoelectron spectroscopy of unhindered α-heterosubstituted germylenes

Two unhindered α-heterosubstituted (O and S) cyclic germylenes have been generated and characterized by the combination of flash vacuum thermolysis of stable germacyclopentenes and ultraviolet photoelectron spectroscopy. This coupling associated with ab initio calculations with the hybrid functional B3LYP and the 6-311G(d) basis set allows to predict the electronic properties of the generated germylenes. The thermodynamic stabilization of these reactive molecules by electronic delocalization of the heteroatom π lone pairs within the 4π orbitals of the germanium atom is clearly shown.     

Synthese de cetoses a chaine ramifiee dans la serie du d-fructose et du d-psicose

Stereospecific synthesis of branched-chain 3-C-formyl, 3-C-hydroxymethyl and 3-C-methyl derivatives of d-psicose have been achieved via nucleophilic C-acylation by means of the 1,3-dithian carbanion of 1,2:4,5-di-O-isopropylidene-β-d-erythro-hexo-2,3-diulo-2,6-pyranose 1. Addition of nitromethane to 1 led to d-psicose and d-fructose derivatives 8 and 9.     

Carbanion cyclisation of esters. Part 2: Enantiospecific construction of the tricyclic framework of the marine sesquiterpenes, spirodysins

Enantiospecific construction of the bicyclo[4.3.0]nonan-8-one 17 employing a lithium and liquid ammonia mediated carbanion cyclisation of the δ-methyl-δ,ε-unsaturated ester 13, and its elaboration to the tricyclic framework of the marine sesquiterpenes spirodysins are described.     

Multicomponent analysis in luminescence spectroscopy

Multicomponent analysis of absorption spectra (infrared or electronic spectra) by factor analysis is a suitable method to use. The algorithm of factor analysis is now available for luminescence spectroscopy. The first possibility, as in absorption spectroscopy, is to determine pure components emission spectra for a unique set of spectra of mixtures in overdetermined conditions. On the other hand, it is also possible to extract pure components emission and excitation spectra of the only data corresponding to the 3D fluorescent spectrum of a single mixture. The results are evaluated in respect to noise level and concentrations ratio on both simulated and real spectra.     

L'application des radioisotopes a la chromatographie sur colonnes de celluloses substituees-IV L'analyse du mercure et du zinc dans le bismuth

The Chromatographic behaviour of nanogram amounts of bismuth has been studied by radioisotope techniques on cellobiose, cellulose and seven substituted celluloses. All celluloses in ethyl ether adsorb bismuth, provided that it is as nitrate, and that excess of nitric acid is avoided. Bismuth can be eluted with thiocyanate in ether-methanol or with hydrochloric acid in methanol, depending on the retention strength of the various functional groups of celluloses. A very simple method of separation of bismuth from mercury over a wide range of concentration is presented.     

Polymeres optiquement actifs—X. Mise en evidence d'une reaction secondaire au cours de la polycondensation en milieu acide du formaldehyde et de la n-tosyl l-tyrosine. Influence sur l'activite optique

The variation of the optical rotatory dispersion (ORD) of the acid-catalysed phenol-formaldehyde type polycondensate of N-tosyl l-tyrosine (I) with its degree of ionization can only be explained by a secondary reaction which modifies the monomeric unit. This reaction is initially explored using a non-polycondensable model of (I): N-tosyl l-phenylalanine (II). The formaldehyde reacts with the secondary sulphonamide function of (II) to give the tosyl derivative of 3-carboxy 1,2,3,4 tetrahydro isoquinoline (III). By comparing the ORD of (I), (II), (III) and those of polymers prepared under different conditions, it is shown that during the polycondensation of (I) in acidic medium, the formaldehyde reacts also with some of the sulphonamide functions, thus giving rise to a copolymer instead of a homopolymer. The proportions of the two units are assessed using i.r. spectra.