Determination of Aromatic Amines in Textile After Bromination, by Gas Chromatography Coupled with Electron Capture Detection

A new analytical method is developed for the improved determination of banned aromatic amines in textiles based on the bromination of the aromatic ring system to yield the corresponding bromo derivatives. The derivatization method is very easy to perform and the derivatives can easily extract and separate with gas chromatography. Due to the introduction of the electron withdrawing bromo substituents sensitive detection with very low limits of detection using an electron capture detector is possible. The method was optimized and used for the analysis of textile with quantitative recoveries from spiked samples.     

Sterically hindered active centres in cationic polymerization: Tertiary aromatic amines in the polymerization of 1,3-pentadiene initiated by aluminum trichloride in non-polar solvent

Previous work on the polymerization of 1,3-pentadiene initiated by aluminum trichloride (AlCl₃) in non-polar solvent at 20 °C in the presence of triphenylamine (NPh₃) has highlighted a stabilization of the active centres and a solubilization of AlCl₃ induced by NPh₃ [Delfour M, Bennevault-Celton V, Anh Nguyen H, Cheradame H, Macedo A. Macromol Chem Phys 2004;205:2312-26]. This paper reports the effect of 9-phenylcarbazole, the structure of which is close to that of NPh₃. The results showed a strong decrease of the insoluble fraction (IF), however this electron donor (ED) was a transfer agent alike NPh₃ (alkylation of aromatic rings by the growing polymer chains). To reduce transfer reaction, the influence of two para-substituted triphenylamines—tribromophenylamine (N(PhBr)₃) and tri-p-tolylamine (N(PhCH₃)₃)—on the polymerization of 1,3-pentadiene was studied in the same conditions. Although the presence of Br substituents has no effect on IF, it induced a decrease in the termination reactions with the counter-ion and the transfer reactions. Concerning methyl groups, it has been shown a strong decrease of IF and a negligible amount of alkylation reaction. Moreover the quantity of grafted molecules was reduced and tri-p-tolylamine reduced both the reactions of cyclization and isomerization. Thanks to the stabilization of the active centres by N(PhCH₃)₃ and probably the solubilization of aluminum trichloride, it was possible to obtain a more precisely defined polypentadiene than ever by cationic polymerization in a non-polar medium.     

Stationary perturbation theory

Summary After a short recapitulation of the basic concepts of stationary perturbation theory, this is applied to a many-electron Hamiltonian, with or without an external field, given in a Fock space formulation in terms of a finite basis, the exact eigenfunctions of which are the full-CI wave functions. The Lie algebra _c ⁿ of the variational group corresponding to this problem is presented. It has an important subalgebra _c ⁽¹⁾ of one-particle transformations. Hartree-Fock and coupled Hartree-Fock (also uncoupled Hartree-Fock) as well as MC-SCF and coupled MC-SCF are outlined in this framework. Many-body perturbation theory and Møller-Plesset perturbation theory are derived from the same kind of stationarity condition and a new non-perturbative iteration construction of the full-CI wave function is proposed, the first Newton-Raphson iteration cycle of which is CEPA-0. For the treatment of electron correlation for properties two variants of Møller-Plesset theory referred to as coupled (CMP) and uncoupled (UCMP) are defined, neither of which is fully satisfactory. While CMP satisfies a Brillouin condition, which implies that first order correlation corrections to first- and second-order properties vanish, it does not satisfy a Hellmann-Feynman theorem, i.e. a first order property isnot the expectation value of the operator associated with the property. Conversely UCMP satisfies a Hellmann-Feynman theorem but no Brillouin theorem. The incompatibility of the two theorems is related to an unbalanced treatment of one-particle- and higher excitations in MP theory. CMP, which is based on coupled Hartree-Fock as uncorrelated reference, appears to have slight advantages over UCMP, but neither variant looks very promising for the evaluation of 2nd order correlation corrections to 2nd-order properties. Then four variants of the perturbation theory of properties with a nonperturbative treatment of electron correlation on CEPA-0 level (but extendable to a higher level) are discussed. While those variants which are the direct counterpart of UCMP and CMP must be discarded, the perturbative CEPA-0 derived from a perturbative treatment on full-CI level appears to satisfy all important criteria, in particular it satisfies a Brillouin-Brueckner condition and a Hellmann-Feynman theorem. A simplified version, the coupled Brillouin-Brueckner CEPA-0 appears to have essentially the same qualities. It is important to replace the Brillouin condition of MP theory by the Brillouin-Brueckner condition in non-perturbative approaches, especially if one is interested in properties.     

Calculations of the isotropic hyperfine coupling constants in free radicals

For a number of free radicals the results of non-empirical (ab initio) and semi-empirical (INDO, DEPAC, CNDO/SP) calculations of the isotropic hyperfine coupling constants are compared.     

Surface composition of alloys

The practical importance of alloy surfaces in catalysis, corrosion andother aspects of materials performance is widely recognized. What is needed now is sufficient knowledge of the relationship between externally controllable factors — alloy composition, temperature, environment — and surface properties — composition, structure, chemical activity — to control materials performance in these applications. Our purpose here is to review progress in determining and predicting the relationship between one surface property, composition, and certain externally controllable variables: overall composition, temperature, environment and physical form.We find that theoretical treatments of metal alloy surface composition now include essentially all significant physical effects and can predict values for most parameters of interest. Though improvements are still possible, the accuracy of predictions is more often limited by uncertainties or absence of the basic data for the calculations (e.g., thermochemical values) than by the models themselves.Alloy surface composition can now be measured well. The first monolayercomposition of large alloy slabs can be determined quantitatively over a wide temperature range in ultra-high vacuum. Difficulties with specimens of practical interest still challenge experimentalists. Among these are supported catalysts, surfaces under chemisorbed layers and composition of layers below the first. Significant progress is being made and we expect the next few years will see success.     

Real time measurement of the electron density of a laser generated plasma using a RC circuit

A Nd:YAG laser pulse was focused, in air or on a Cu target, between the plates of a planar charged capacitor. The plasma generates a transient redistribution of the electrical charges on the plates that can be easily measured as a voltage drop across a resistor connected to the ground plate. At the same time, the Stark broadening of the H_α spectral line (656.3 nm) obtained from the optical emission spectrum of the plasma was measured. In this work, we show that the peak of electrical signal measured on the resistor is, in the energy range of our laser (30 mJ to 220 mJ) and at time delays typical of Laser-Induced Breakdown Spectroscopy applications (500–5000 ns), univocally related to the temporal evolution of the Stark broadening of the H_α line. Therefore, after a proper calibration depending on the material and the experimental geometry, the peak of the electrical signal can be used to predict the temporal evolution of the electron density of the generated plasma.     

A novel electron-transfer mediated reaction leading to lepidopterene

(Anthracen-9-yl)methanamines were found to undergo single electron-transfer mediated C-N bond cleavage in the presence of excess dimethyl acetylenedicarboxylate (DMAD) in non-polar solvents leading to the formation of lepidopterene (4) and 1,2-bis(9-anthracenyl)ethane (3). The structure of lepidopterene was confirmed on the basis of NMR data and by X-ray crystallography.     

X-ray powder diffraction and electron diffraction studies of the Ni1±yGe1−xPx system

The wide-range of non-stoichiometric NiAs-type solid solution Ni_1±yGe_1−xP_x has been studied by means of X-ray powder and electron diffraction. The incommensurately modulated structure of Ni(Ge, P) has been found to exist over a wide compositional range which is limited by the end points ≈NiGe_0.8P_0.2 and NiGe_0.3P_0.7 so that the general stoichiometry might be referred to as NiGe_1−xP_x with 0.2?x?0.7. The modulation wave vector is of the type and its modulus is strongly composition dependent. A possible interpretation is given as a “soft transition”, via an incommensurately modulated structure, between the MnP and the NiP structure types, based on the almost purely displacive origin of the distortion. Further, the crystal structures of Ni₅Ge₂P₃ and Ni₂GeP seem to be commensurate approximations of the incommensurate modulated structure of Ni(Ge, P).     

Synthesis and characterization of NiSn colloids and active solids prepared in organic solvents by CLD

Bimetallic colloidal dispersions were obtained by simultaneous cocondensation of nickel and tin atoms with organic solvents at 77 K using the chemical liquid deposition (CLD) method. The atoms in a 1:1 ratio were produced by resistive heating and were reacted with 2-propanol, 2-methoxyethanol, and acetone to produce colloids.The kinetic stability of the colloid dispersions was related to the solvation effect of organic molecules, e.g., low stability for acetone, higher for 2-propanol, and the highest for 2-methoxyethanol. The colloidal particles were characterized by UV-Vis measurements showing absorption bands at 204 and 270 nm. A 3-day study in which samples were taken every hour showed that the absorption bands decrease probably due to clustering. Electrophoretic measurements revealed that the particles are weakly positively charged. Transmission electron microscopy studies revealed an average particle size distribution ranging from 6 to 10 nm depending on the solvent. Most of the colloids exhibit a spherical shape with some degree of agglomeration.After solvent evaporation several active solids were obtained. The FTIR spectra show the presence of the solvent incorporated in the active solids/films, e.g., for acetone the carbonyl stretching is observed at 1723 cm^–1. The thermal stability of these bimetal powders/films was studied by TGA up to 550 °C. Their maximum decomposition temperatures are 350, 415, and 429 °C for NiSn–2-methoxyethanol, –2-propanol, and –acetone, respectively.     

The Kinetics of Heterogeneous Electron Transfer Reaction in Polar Solvents

Data for heterogeneous electron transfer reactions obtained in the last ten years have been examined within the context of contemporary theory. Special attention is focused on systems for which rate constants and activation parameters are available as functions of solvents and of temperataure. The role of reactant structure in deteriming the kinetic parameters is also considered. Double layer effects both at unmodified and modified electrodes are discussed in detail. Experimental techniques, especially those suited to measuring fast reactions, are also outlined.