Polymorphism and luminescence properties of CMONS organic crystals: bulk crystals and nanocrystals confined in gel-glasses

In order to compare the polymorphism of 1-cyano-1-(4-nitrophenyl)-2-(4-methoxyphenyl)ethene CMONS crystallized in solutions to that of CMONS nanocrystals grown in the pores of dense sol-gel matrices, we have first studied the CMONS polymorphism in various solvents which were then used in the nanocrystallization processes. The different polymorphs were characterized by differential scanning calorimetry, X-ray diffraction and absorption as well as luminescence spectroscopies. The differences observed between CMONS powders and CMONS nanocrystals illustrate the role played by the silicate matrices on the polymorphism of CMONS. This matrix effect would be used to stabilize a particular polymorph of an organic phase and thus to adjust the optical properties of the nanocomposite hybrid organic–inorganic material.     

(Liquid + liquid) equilibria of the quaternary system methanol + isooctane + cyclohexane + benzene at T = 303.15 K

Tie line data of the ternary system {methanol + isooctane + cyclohexane} were obtained at T = 303.15 K. A quaternary system containing these three compounds and benzene was also studied at the same temperature, while data for {methanol + benzene + cyclohexane} and {methanol + benzene + isooctane} were taken from literature. In order to obtain the binodal surface of the quaternary system, four quaternary sectional planes with several cyclohexane/isooctane ratios were studied. The distribution of benzene between both phases was also analysed. Ternary experimental results were correlated with the UNIQUAC and NRTL equations and compared with predictions using the UNIFAC group contribution method.     

The composition, charge and architecture of hydronium ions as observed in the crystalline state

The structures of hydronium ions present in single crystals have, by and large, been thought as being relatively simple and characterized by the classical formulae H₃O⁺, , and . All of them are thought to be quasi-planar, acyclic entities of charge +1, exclusively. In this review, we show that such is not the case in view of the fact that there exist documented examples of cyclic hydronium ions, that their charge can be larger than +1 and that they exist in aggregates containing more than four oxygens. Moreover, it is documented that hydronium ions exist in the form of geometrical isomers or conformers. To cite this article: I. Bernal, C. R. Chimie 9 (2006).     

Thermal oxidation of cellulose investigated by chemiluminescence. The effect of magnesium and calcium carbonates and of different pHs

Whatman cellulose impregnated with calcium and magnesium carbonates was oxidized and chemiluminescence accompanying this oxidation has been measured. It was shown that magnesium ions in deacidified cellulose pulp promote the light emission significantly. On the other hand, acid papers give the more pronounced light signals at temperatures close to ambient. The relation between chemiluminescence runs and paper degradation has been implicated, with an attempt to extrapolate half-lives of paper samples to conditions close to ambient. To cite this article: J. Rychlý et al., C. R. Chimie 9 (2006).     

Molar excess enthalpies of ethyl acetate + alkanols at T = 298.15 K, p = 10.0 MPa

A commercial flow-mixing isothermal calorimeter was tested by measuring heat of mixing curves for exothermic, endothermic, S-shaped and double minimum molar excess enthalpy mixtures at high pressure. The results show this calorimeter is able to produce good quality data. Molar excess enthalpies for ethyl acetate mixed with a series of simple alkanols were measured at T = 298.15 K and p = 10 MPa.     

Process monitoring of polymers by in-line ATR-IR, NIR and Raman spectroscopy and ultrasonic measurements

The aim of the present work is to show that spectroscopic and ultrasonic methods are powerful in situ methods for monitoring polymerization processes and for the determination of the composition of polymer blends and additives during extrusion. Quantitative analysis carried out with chemometric methods can determine the composition of multicomponent polymer mixtures and predict real world samples in real-time during extrusion. Examples are the modification of hyperbranched poly(urea-urethane)s, the polymerization of MMA, the real-time determination of flame retardants in PA, and the determination of the composition of the blend PE/PS. To cite this article: D. Fischer et al., C. R. Chimie 9 (2006).     

A stereodivergent cascade imine → azomethine ylide → 1,3-dipolar cycloadditive approach to α-chiral pyrrolidines

Stereodivergent [3+2] cycloadditions of chiral α-amino azomethine ylides leading to highly functionalized pyrrolidines are reported. The marriage of substrate conformational preferences and either an inter- or intramolecular cycloaddition manifold leads to either the l (syn) or u (anti) relationship between the pyrrolidine and α-stereocenters. The latter result may be applicable to a new approach to the bioxalomycin family of antibiotics.     

Coadsorption of carbofuran and lead at the water/silica interface. Possible impact on environment

Despite its extremely weak adsorption at the water/silica interface, carbofuran can, however, induce the coadsorption of metallic salts, like, for example, lead nitrate, and thus enhance its adsorption. We quantitatively studied this phenomenon with a depletion method and under concentration conditions close to the environmental ones. Heavy metal salt was found to positively adsorb, whereas carbofuran relative adsorption is generally slightly negative. This study provides evidence that considering these facts is of paramount importance in environmental prospects. To cite this article: G. Elmanfe et al., C. R. Chimie 9 (2006).     

Isothermal vapor-liquid equilibrium at T = 333.15 K and excess volumes and molar refractivity deviation at T = 298.15 K for the ternary mixtures {di-methyl carbonate (DMC) + ethanol + benzene} and {DMC + ethanol + toluene}

Isothermal vapor-liquid equilibrium data at 333.15 K are reported for the ternary systems {di-methyl carbonate (DMC) + ethanol + benzene} and {DMC + ethanol + toluene} as determined with headspace gas chromatography. The experimental ternary vapor-liquid equilibrium (VLE) data were correlated with different activity coefficient models. The excess volume (V^E) and deviations in molar refractivity (ΔR) data are reported for the binary systems {DMC + benzene} and {DMC + toluene} and also for the ternary systems {DMC + ethanol + benzene} and {DMC + ethanol + toluene} at 298.15 K. These V^E and ΔR data were correlated with the Redlich-Kister equation for binary systems and the Cibulka equation for ternary systems.     

Modeling of reactive systems in twin-screw extrusion: challenges and applications

Reactive extrusion processes involve the difficulties of mastering classical polymer processes, such as twin-screw extrusion for example, and the problems of controlling a chemical reaction in very specific conditions (high-viscosity medium, high temperatures, short residence times). Therefore, it is often very difficult to intuitively understand all the aspects of the process and to clarify the complex interactions between the numerous variables, and then to properly design and optimize the industrial process. Numerical modeling can be a very efficient tool to overcome these difficulties. However, it remains a real challenge, as it necessitates to couple flow simulation in complex geometry, reaction kinetics and evolutionary rheological behavior. Moreover, the information needed is sometimes difficult to obtain with the required accuracy. After a general presentation of the principles of the different reactive extrusion modeling methodologies, we will focus on the models we developed, based on continuum mechanics. Different examples of applications are presented for illustrating the interest of this method. To cite this article: B. Vergnes et al., C. R. Chimie 9 (2006).     

Synthesis and properties of copper quinonoid complexes for optical recording application

We describe the synthesis of novel quinonemonimines Cu(II) coordination complexes, of the type:

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which, in addition to their intrinsic interest, have potential application in optical recording. The following key parameters have been highlighted: (i) the presence of coordinating arms on the quinonoid core of the ligand leads to octahedral complexes with increased solubility, (ii) the presence of Cu(II) as a metal centre leads to a favourable exothermic decomposition, (iii) the presence of quinonoid moieties results in the optical absorption to be in the desired wavelength range. To cite this article: P. Braunstein et al., C. R. Chimie 9 (2006).     

Spectroscopic probes for real-time monitoring of polymer modification and degradation reactions

The processing of polymers may be accompanied by oxidation and elimination reactions that affect the quality of the final product. In reactive processing, polymerisation occurs in the extruder or autoclave and the extent of reaction becomes an important process variable. The monitoring of these chemical changes in real-time so that processing may be optimised requires the use of analytical methods such as fibre-optic Near Infrared (NIR) spectroscopy. In this paper the requirements and limitations for this and related spectroscopic probes are described and novel approaches based on infrared emission and transient infrared transmission spectroscopy (TIRTS) are discussed. To cite this article: G. George et al., C. R. Chimie 9 (2006).     

(Liquid + liquid) equilibria of (water + propionic acid + alcohol) ternary systems

(Liquid + liquid) equilibrium (LLE) data of the solubility (binodal) curves and tie-line end composition were examined for mixtures of {water (1) + propionic acid (2) + octanol or nonanol or decanol or dodecanol (3)} at T = 298.15 K and 101.3 ± 0.7 kPa. The reliability of the experimental tie-line data was confirmed by using the Othmer-Tobias correlation. The LLE data of the ternary systems were predicted by UNIFAC method. Distribution coefficients and separation factors were evaluated for the immiscibility region.     

(Liquid + liquid) equilibria of (water + propionic acid + cyclohexanone) at several temperatures

(Liquid + liquid) equilibrium (LLE) data for (water + propionic acid + cyclohexanone) were measured under atmospheric pressure and at T = (293.2, 298.2 and 303.2) K. Phase diagrams were obtained by determining solubility and tie-line data. The LLE data of the ternary systems were predicted by UNIFAC method. Distribution coefficients and separation factors were evaluated over the immiscibility regions.     

Isobaric vapor–liquid equilibria for the quaternary reactive system: Ethanol + water + ethyl lactate + lactic acid at 101.33 kPa

Isobaric vapor–liquid equilibrium (VLE) data of the reactive quaternary system ethanol (1) + water (2) + ethyl lactate (3) + lactic acid (4) have been determined experimentally. Additionally, the reaction equilibrium constant was calculated for each VLE experimental data. The experimental VLE data were correlated using the UNIQUAC equation to describe the chemical and phase equilibria simultaneously. For some of the non-reactive binary systems, UNIQUAC binary interaction parameters were obtained from the literature. The rest of the binary UNIQUAC parameters were obtained by correlating the experimental quaternary VLE data obtained in this work. A maximum pressure azeotrope at high water concentration for the binary reactive system ethyl lactate + water has been calculated.     

(Liquid + liquid) equilibria of {heptane + xylene + N-formylmorpholine} ternary system

(Liquid + liquid) equilibrium (LLE) data for ternary system {heptane (1) + m-xylene (2) + N-formylmorpholine (3)} have been determined experimentally at temperatures ranging from 298.15 K to 353.15 K. Complete phase diagrams were obtained by determining solubility and tie-line data. Tie-line compositions were correlated by Othmer-Tobias and Bachman methods. The universal quasichemical activity coefficient (UNIQUAC) and The non-random two liquids equation (NRTL) were used to correlate the phase equilibrium in the system using the interaction parameters determined from experimental data. It is found that UNIQUAC and NRTL used for LLE could provide a good correlation. Distribution coefficients, separation factors, and selectivity were evaluated for the immiscibility region.     

Excess molar enthalpies of methylformate + (1-propanol, 2-propanol, 1-butanol, 2-butanol and 1-pentanol) at T = 298.15 K, p = (5.0, 10.0) MPa, and methylformate + 1-propanol at T = 333.15 K, p = 10.0 MPa

A high pressure flow-mixing isothermal calorimeter is used to determine the excess molar enthalpies of methylformate + (1-propanol, 2-propanol, 1-butanol, 2-butanol and 1-pentanol) at T = 298.15 K and p = (5.0, 10.0) MPa, and methylformate + 1-propanol at T = 333.15 K and p = 10.0 MPa. The Redlich-Kister equation is fit to the experimental results.     

Effect of ro-vibrational excitation of HCl on the stereodynamics for the reaction of O(P) + HCl → OH + Cl

We have carried out quasi-classical trajectory calculations for the title reaction. The effect of initial ro-vibratioanl state of HCl on the stereodynamics of O(³P) + HCl → OH + Cl reaction on ³A″ potential energy surface was investigated. Integral cross sections, product ro-vibrational state distributions, differential cross sections, and three angle distribution functions about the products alignment and orientation have been presented. The results manifest that the vibrational excitation has a larger influence on the total cross section, differential cross section, angle distributions (concerning the initial/final velocity vector, and the product rotational momentum vector) compared with the rotational excitation, and the phenomena are quite different with the increase of the vibrational and rotational quantum number. Also the products are vibrationally cold and rotationally hot.