bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quelques Aspects de la Chimie Theorique Contemporaine
Authors: Leroy Georges 
Published: September 2010

AbstractIn this paper we make a survey of various aspects of theoretical chemistry to which we have made some contribution. Our Localized Molecular Orbital (LHO) approach to the electronic structure and reactivity of chemical species allowed us not only to generalize the Lewis and Linnett theories of valence but also to determine the mechanism of a wide variety of organic reactions. We have also proposed a general definition of the concept of stabilization energy applying to any compound. Using this concept, we have been able to elaborate a table of standard bond energy terms, to unify various notions such as hyperconjugation, resonance, ring strain and steric repulsion energy and to carry out a critical analysis of former definitions of the stabilization energy of olefines and free radicals. Furthermore, we have shown that the enthalpy changes and, eventually, the rate constants of any physical or chemical process involving paramagnetic or charged species could be rationalized in terms of their stabilization energies. In this prospect, we have proposed an original interpretation of the persistence of some free radicals and we have made interesting predictions concerning the thermochemistry and the kinetics of various reactions involving neutral or charged reactive intermediates. Moreover we have devised a semi‐empirical method for estimating the barrier heights of atom transfer reactions. So, we have been able to systematically determine the kinetic parameters of these processes using the transition state theory with an Eckart tunnelling correction. Finally, our barrier height modelling allowed us to interpret the effect of substituents on the activation barriers of hydrogen transfer reactions leading to carbon centred free radicals. On the whole, we have tried to demonstrate the promising role theory is presumably led to play in the development of modern chemistry, owing to the joint utilization of its own tools ‐ concepts, models and formalism ‐ and the information provided as much by experimental techniques as by the ab initio methods of quantum chemistry.
The Substrate Specificity of Phospholipase A2: The Reaction of the Enzyme with 3‐Octanoyloxy‐4‐Nitrobenzoic Acid
Authors: Markowitz Michael A. , Seykora John T. , Kézdy F. J. 
Published: September 2010

Abstract3‐Octanoyloxy‐4‐nitrobenzoic acid is hydrolyzed by the phospholipase A2 (D‐49) from the venom of Agkistrodon piscivorus. The hydrolytic reaction is truly catalytic, requiring the presence of calcium ion (Kd=3.3 ± 0.7mM). At pH=7.0 the value of the enzymatic rate constant is (Kcat/Km)max=175 ± 14 M−1 sec−1, comparable to that of the enzymatic hydrolysis of 3‐sn‐dibutyryl lecithin.
Regiochemistry of the Alkylation of Selenium Stabilized Allylic Anions
Authors: Hevesi L. , Nsunda K. M. , Renard M. 
Published: September 2010

AbstractSelenium substituted allyl lithiums react with alkyl halides or benzaldehyde to produce alkylation products in good yield. The regiochemistry of this reaction is found to bear similarities with that of the thio‐analogs in that it depends largely on the nature of the alkylating agent and on the reaction conditions; it is further complicated by the occurrence of the allyl selenide rearrangement discovered recently.
Electron Impact Fragmentation of Mixed and Asymmetric Benzyltin Compounds
Authors: Gielen Marcel 
Published: September 2010

AbstractThe mass spectra of seventeen mixed and of five asymmetric benzyltin compounds are described and analysed. The proposed fragmentation pattern is in agreement with the hypothesis of preferred Sn(IV) and Sn(II) valence states in the tin‐containing fragments, which are reached by a loss of a radical from the molecular ion, or by the loss of an alkene or alkane from a favourable valence state.
The Vibrational Analysis of the Copper Complexes with Planar Oxamides and Oxamic Acid
Authors: Desseyn Herman , Schoeters Georges 
Published: September 2010

AbstractThe preparation of different complexes of planar oxamides and oxamic acid with Cu(II) and Cu(III) are reported. Isotopic shifts in the i.r. spectra let us assign the most fundamental vibrations.
Conductometric Study of Ion‐Pair Equilibria of Silver Benzoate in Methanol‐Water Mixtures: A Comparison of Conductance Equations and Ion‐Pair Constants
Authors: Maniah V. , Sethuram B. , Navaneeth Rao T. 
Published: September 2010

AbstractConductivities of silver benzoate in 0–60% (w/w) methanol‐water mixtures were measured at 25°C and analysed using Fuoss‐Hsia equation in the form of Fernandez‐Prini coefficients, Shedlovsky and Fuoss‐Kraus extrapolation techniques for calculating the association parameters (ΛO and KA). A comparison of these parameters revealed that all the methods of analysis yield essentially the same ΛO values but differed in KA values. The Shedlovsky method turned out to be superior and predicted better association constants than the Fuoss‐Kraus technique.The log KA vs 1/D plot was linear with finite intercept in accordance with the modified Denison‐Ramsey theory i.e. KA=2.934 exp (161.08/D) of ion‐pair equilibria. The association constants and ionsize parameter (a) values required by Bjerrum, Fuoss, Denison‐Ramsey and Ebeling‐Kraeft, Yokoyama Yamatera theories were also estimated and their soundness to explain the behaviour of silver benzoate in all the solvent mixtures studied, was discussed.
Neutral Chelate Lanthanide Complexes of 3‐Hydroxy Pyridine‐1‐Oxide and Nicotinic Acid‐1‐Oxide
Authors: Navaneetham N. S. , Kalyanasundaram R. , Soundararajan S. 
Published: September 2010

AbstractNew lanthanide neutral complexes of Nicotinic acid‐l‐oxide and 3‐hydroxy pyridine‐l‐oxide were synthesized by a novel method consisting of refluxing the mixture of the ligand (L) and lanthanide trichloroacetate in methanol. Solid complexes of the formula LnL3.2H2O where Ln=La‐Yb and Y, were isolated. Proton NMR and IR spectra for the complexes reveal the bidentate binding of both the ligands to the lanthanide ion. Electronic spectra along with the conductance data, for the complexes, indicate a coordination number of six for the lanthanide ion in the complexes of both the N‐oxide derived ligands.
Réactivité des Dihydro‐3, 4‐2H‐Benzoxazines‐1, 3 Avec les Amines Mise en Évidence D'Un Equilibre Impliquant L'Ouverture de L'Hétérocycle
Authors: Tzschoppe D. , Vebrel J. , Schwob J. M. , Roche M. , Riess G. 
Published: September 2010

AbstractIn the presence of primary or secondary amines 2H‐3, 4‐dihydro‐1, 3‐benzoxazines equilibrate with a ring‐opened coupling product and the corresponding Mannich base. The equilibrium conditions and the mechanism of the reaction have been verified.
Action des Organométalliques sur les Iminoéthers: Nouvelle Voie D'Accès Aux Oxazolines
Authors: Bellassoued M. , Gaudemar M. , Hajjem B. , Baccar B. 
Published: September 2010

AbstractIminoethers of type 1 have been shown to react with organometallic reagents to give oxazolines in good yield. The process of the reaction is discussed.
Étude par Resonance Magnétique Nucléaire du Proton A Haut Champ des Méthyl‐4 Pyrazolines‐2
Authors: Elguero José , Fruchier Alain 
Published: September 2010

AbstractFor the first time the ABCM3X and ABCM3 systems of proton nmr spectra of two 4‐methyl‐2‐pyrazolines were analyzed. The studied compounds were 1–(2′, 4′‐dinitrophenyl)−4‐methyl‐2‐pyrazoline and 1‐(2′,4′‐dinitrophenyl)−3‐bromo‐4‐methyl‐2‐pyrazoline. The difficulty to analyze the spectra of 4‐substituted pyrazolines, compared with the analysis of 5‐substituted ones, is discussed.
Spectrophotometric Determination of Ti(IV) With 2‐Benzylideniminobenzohydroxamic Acid
Authors: Salinas F. , Mahedero M. C. , García‐Martín J. P. 
Published: September 2010

AbstractA new method for the photometric determination of Ti(IV) with 2‐benzylideniminobenzohydroxamic acid is described with 50% ethanol and 0.5 M HCl medium, the complex shows an absorption maximum at 392 nm. The molar absorptivity value is 5.110 1.mol−1 cm−1 an it is possible determine between 2.0 and 6.0 ppm of Ti(IV). The method is applied to determination of Ti(IV) in a pharmaceutical drug.
Molecular Structure Analysis of Monoamine Oxidase Inhibitors: Moclobemide, p‐Chloro‐n‐(2 Ethylmorpholinium)‐Benzamide Chloride Monohydrate, C13H17N2O2Cl.HCl.H2O
Authors: Durant F. , van Der Brempt C. , Bufkens F. , Evrard G. 
Published: September 2010

AbstractMr=232.1, monoclinic, P21/c, a=13.504(1), b=15.805(1), c=7.369(1) Å, β=95.81(1)°, V=1564.7 Å3, Z=4, Dc=1.37 g.cm−3, Cu Kα, λ=1.54178 Å, μ=36.71 cm−1 F(0,0,0)=680.0, T=293 K, final Rw=0.059 for 2446 observed reflections (I≥2.5σ(I)). Crystal cohesion is assumed by intermolecular H‐bonds constraining a particular conformation of the title compound. The morpholinic nitrogen atom is protonated by an hydrochlorid acid molecule.
Nouvelles Méthodes de Déshalogènation et de Formation D'Éthers D'Enol Triméthylsilyliques Par Action de iPr2NLi Sur Quelques α‐Monobromo‐Et α, α'‐Dibromocétones
Authors: Lion Claude , Dubois Jacques‐Emile , Lebbar Khadija 
Published: September 2010

AbstractAttemps to prepare 2‐bromo‐2, 4‐dimethyl, 3‐trimethylsiloxy 3‐pentene reacting lithium diisopropylamide (LDA) with 2‐bromo‐2, 4‐dimethyl‐3 pentanone have revealed two new reactions. After a few minutes quantitative yields are obtained of either the dehalogenated ketone (after hydrolysis) or the trimethylsilyl enol ether (after addition of trimethylsilyl chloride). These reactions are general and have been extended to other α‐monobromoketones and α,α'‐dibromoketones. In the latter case, the reaction is more complex and leads generally to dehalogenation or reduction products.
New Preparations of P‐Nitrophenylcyclopropane
Authors: Broos R. , Anteunis M. J. O. 
Published: September 2010

AbstractThe preparation of p‐nitrocyclopropylbenzene by reaction of dimethyloxosulfonium methylide with p‐nitrostyrene or p‐nitrobenzyl iodide (bromide) in 67 and 37 % yield respectively is reported.
Synthesis of Dibenzo[d,g] [1,2,4] Triazolo[4, 3‐a] [1,3] Diazocine‐8‐one and Dibenzo [d,g] [1,2,4] Triazolo [4,3‐a] [1,3] Oxazocine‐8‐One
Authors: Rahman Loay K. A. 
Published: September 2010

AbstractCompounds (1)‐representatives of a new heterocyclic system were obtained by reaction of 3‐hydroxy‐,3‐chloro‐ and 3‐amino‐4‐phenyl‐1,2,4‐triazoles with iodobenzoic acid and N‐methylanthranilic acid followed by ring closure to give the parent compounds in good overall yield.
The Adsorption of Sulfur‐Compounds on Cu(II)Y Zeolite
Authors: Demertzis Mavroudis , Kovala‐Demertzi Dimitra , Vansant Etienne F. , Peeters Guido J. , Vanderheyden Els 
Published: September 2010

AbstractThe adsorption of H2S, CH3SH and CS2 on Cu(II)Y zeolite reveals an affinity sequence CH3SH » CS2 > H2S. Very strong displacement effects of CS2 and H2S by SH were observed when binary mixtures of CS2/CH3SH and CS2/H2S were contacted with Cu(II)Y. In ternary mixtures H2S is displaced by both, CS2 and CH3SH while CS2 is displaced by CH3SH. The interaction between the Cu(II)Y and the different S‐compounds is studied by infrared spectroscopy. A strong dissociative adsorption, creating new hydroxyl groups, is only observed for the CH3SH adsorption in the Cu(II)Y zeolite and reflects the high selectivity of Cu(II)Y for CH3SH compared to H2S and CS2.
Polarographic Behaviour of 2‐Pyrilideniminobenzohydroxamic Acid
Authors: Misiego A. Sánchez , Salinas F. , Guiberteau Cabanillas A. , Durán Merás I. 
Published: September 2010

AbstractThe polarographic DPP and DC techniques have been utilized to study the behaviour of 2‐pyrilideniminobenzohydroxamic acid (PIBHA). This reagent gives rise to two cathodic waves, the Ep of the first wave is‐1.07 V vs Ag/AgCl at pH 3.38 and the Ep of the second wave appeared at‐1.45 V at the same pH. The principal characteristics of these waves have been studied and the corresponding possible mechanisms of the electrode process for both waves have been proposed.
Contribution À L'Étude des Réactions de Combinaison des Radicaux Alcoyle Tertiaires en Phase Solide
Authors: Gourdin‐Servenière C. , Fontaine L. M. , Tilquin B. 
Published: September 2010

AbstractDisproportionation/combination ratios of self‐reacting t‐alkyl radicals are estimated in solid phase at low temperature. The low temperature solid state limit was estimated to be 7–25, this value is considerably lower than ratios of the literature (100 to 500) and is compatible with the FISCHER limit in liquid state. In the present work, the ratios are determined by product analysis from the gamma radiolysis of isobutane.
Note on the Preparation of Very Active N,N‐Bis (2‐OXO‐3‐Oxazolidinyl)‐Phosphorodiamidic Chloride (Bop‐Cl), an extremely Effective Reagent for Peptide Formation
Authors: van Der Auwera C. , Anteunis M. J. O. 
Published: September 2010

AbstractA preparation of high‐quality coupling reagent Bop‐Cl is reported. It fulfills the expectations of reproducibility in efficient peptide coupling reactions that are characterized by the formation of little side products and by a clean work‐up.
A Stereoselective Synthesis of Cis‐1‐Methyl‐3‐(3,4‐Dimethoxyphenyl)‐5‐Bromo‐7‐methoxy‐8‐hydroxy‐1,2,3,4‐tetrahydroisoquinoline
Authors: Badía D. , Domínguez E. , Iriondo C. 
Published: September 2010

AbstractThe title compound (7a) was stereoselectively synthesized from the brominated 1,2‐diaryl‐ethylamine (6c) and its configuration was unambiguously established on the basis of spectroscopic data.
Spectrophotometric Study of 2‐Oximinodimedone Dithiosemicarbazone‐ni(II) complex. Determination of ni(II)
Authors: Salinas F. , Jiménez Sánchez J. C. , Lemus J. L. 
Published: September 2010

AbstractThe spectrophotometric study of the orange 2‐oximinodimedone dithiosemicarbazone‐Ni(II) complex was made in dimethylformamide‐water solution (ϵ 440 nm=7200 l. mol−1. cm−1; stoichiometry 2:1 reagent to Ni(II) and apparent stability constant 1.0x106). A new method for the spectrophotometric determination of Ni(II) is proposed for concentrations between 0.36 and 6 μg ml−1.
The Role of Bone Mineral in Calcium and Phosphate Homeostasis
Authors: Driessens F. C. M. , van Dijk J. W. E. , Verbeeck R. M. H. 
Published: September 2010

AbstractOn the basis of the composition of the mineral in bone and the saturation level of blood plasma with respect to the slightly soluble calcium phosphates it is shown that normal tissue fluids are not supersaturated with whole bone but with the minerals of dead bone. The solubility controlling phase in living bone is octocalcium phosphate and the presence of this phase regulates the calcium and phosphate concentrations of the body fluids by simple physicochemical equilibrium.
The Importance of the Input Parameters in the Determination and Evaluation of 2200 M.S−1 (n,γ) Cross Sections
Authors: De Corte F. , Simonits A. , De Wispelaere A. 
Published: September 2010

AbstractThe activation method is applied to the determination of the 2200 m.s.−1 (n,γ) cross sections (0) for the reactions 184Os(n,γ) 185Sm(n,γ)155 Sm and 153Eu(n,γ) 154Eu. The results of these experiments, together with a critical literature survey, demonstrate the importance of reporting the input parameter data for (isotopic abundance), γ (absolute gamma intensity) and T (half life), which are strictly associated with the σ0‐output.
Analytical Aspects of the Determination of Chromium by Graphite Furnace A.A.S.
Authors: van Schoor O. , Deelstra H. 
Published: September 2010

AbstractAshing‐and atomisation curves of chromium and lifetime of uncoated and pyrocoated graphite tubes were determined. Interferences such as background absorption and the influence of acids, cations and chlorides on the atomisation of chromium were studied. Acids, recipients and homogenisation can be major sources of contamination; contamination by dust particles in the laboratory was found to be neglegible.
Determination of Magnesium and Calcium in Stabilized Zirconium Dioxide by Atomic Absorption Spectrometry
Authors: Carleer R. , van Poucke L. C. , François J.‐P. 
Published: September 2010

AbstractA procedure is described which permits the determination of magnesium (< 4% (w/w)) and calcium (< 1% (w/w)) in zirconium dioxide by atomic absorption spectrometry. Two different dissolution methods are used and evaluated. In the first method the ZrO2 is dissolved in a mixture of concentrated HF, HCl and HNO3 acids in a teflon bomb, while in the second method the ZrO2 matrix is brought into solution with a (NH4)2SO4, concentrated H2SO4 mixture. The optimalization of the analytical parameters is studied. For both elements the method of standard addition is employed. Powders of ZrO2, partially sintered (600‐1000°C) and completely sintered (1650°C) ZrO2 tubes are analyzed with both optimized methods for magnesium and with the first method for calcium.
The Ph4AsPh4B Assumption for Single Ion‐Thermodynamics and its Asymmetric Partition to Cation and Anion
Authors: Kim J. I. 
Published: September 2010

AbstractThe partitioning of thermodynamic quantities of the reference electrolyte (Ph4AsPh4B) is discussed by comparing its standard free energies of transfer from water to organic solvents (ΔWSG°) with those for Ph4AsPh4B. From experiment in 14 different dipolar‐aprotic organic solvents, it is found that an asymmetric partition with the ratio: ΔWSG° (Ph4As+)/ΔWSG° (Ph4B−)=1.08 ± 0.02 is better justified than the equal partition practised in the literature. This asymmetry is mainly ascribed to the size difference between the reference cation and anion. The electrostatic contribution (ΔWSG°A(el)), primarily from iondipole interaction, does not appear as a cause for the asymmetry.
Nitric Acid Interaction with Marine Aerosols Sampled by Impaction
Authors: Otten Ph. , Bruynseels F. , van Grieken R. 
Published: September 2010

AbstractObserved enrichments of NaNO3 in marine aerosols have been attributed to NaNO3‐formation during the sampling procedure in the case of filter sampling. This artifact was investigated for cascade impactor sampling. Experiments were carried out in which an air stream containing 1 μg HNO3 per m3 was led over 1‐2 μm NaCl‐particles deposited in an impactor. The morphology of the particles and the chemical composition of their core and surface layer was then investigated using laser microprobe mass analysis (LAMMA) and electron microprobe measurements. A definite NaNO3 formation was observed. It can, however, be avoided completely by placing a suitable denuder or pre‐stage in front of the impactor. Even with such a precaution, NaNO3 was still found in ambient marine aerosols over the North Sea. This can thus be attributed now with certainty to a previous atmospheric interaction of NaCl with HNO3.
The Determination of the Stability Constants of Mononuclear and Polynuclear Species of Mono‐ and Dicarboxylic Acids via Potentiometric Titrations
Authors: Bouserie Frank L. G. , Thun Harry P. 
Published: September 2010

AbstractThe potentiometric determination of the stoechiometric dissociation constants of mono‐ and dicarboxylic acids is certainly not hampered by unsophisticated calculation methods or experimental inaccuracies. The reliability of these constants is unsettled by a poor control of the activity coefficients during these experiments. In this paper, the variation of the activity coefficients as well as the effect on the dissociation constants and their determination is discussed.
Analysis of silicate rocks for Rb, Sr, Y, Zr and Nb by Energy‐Dispersive X‐Ray Fluorescence
Authors: Vanlerberghe L. , Hertogen J. 
Published: September 2010

AbstractA procedure is described for accurate and precise routine analysis for the trace elements Rb, Sr, Y, Zr and Nb in silicate rocks by Energy‐Dispersive X‐Ray Fluorescence analysis with Ag secondary target excitation. The trace elements are analyzed on pressed powder pellets. Primary standardization is relative to international reference rocks and matrix absorption corrections are based on the Compton scatter method. The computer program for spectrum analysis incorporates advanced non‐linear least squares peak fitting techniques. Overall precision for a single measurement can be as good as 2% relative. Analysis of established U.S.G.S. reference samples AGV‐1, GSP‐1 and G‐2 shows that accuracies of better than 5% relative are obtained. Supplementary data for Zn, Ga, Pb and Th show poorer precision.
Synthesis and Characterization of n‐Alkylanilinium Octamolybdates. Identification of Some Products of Their Thermogravimetric Decomposition
Authors: Arnaiz A. R. , Santiago C. , Martinez M. 
Published: September 2010

AbstractThe compounds (BH)4Mo8O26 being B: anilinium, N‐methylanilinium, N,N‐dimethylanilinium and N,N‐diethylanilinium have been synthetized and characterized for the first time.Thermogravimetric decomposition in isothermal and non‐isothermal regime have been studied. At temperatures between 480–560 K a great number of organic compounds, different from the initial organic bases have been identified, with molecular weight between 117–254 g mol−1.
Étude Théorique des Propriétés Électroniques et Électrochimiques de la Polyaniline
Authors: Brédas J. L. , Thémans B. , André J. M. , Silbey R. , Boudreaux D. S. , Chance R. R. 
Published: September 2010

AbstractThe electronic band structures of various neutral and charged forms of polyaniline are discussed. The MNDO semiempirical technique is used to determine the polyaniline chain geometries. Band‐structure calculations, based on those geometries, are then performed with the VEH method. We obtain theoretical estimates of ionization potentials, bandgaps, electron affinities and redox potentials which are in good agreement with experiment. We discuss in detail the electrochemical properties of polyaniline in aqueous media and the structural evolution of the polymeric chains upon oxydation and reduction. We propose a model for the electrochemical properties of polyaniline which is in excellent agreement with experimental data and theoretical predictions.
Synthèses et Synthèses Enantiosélectives D'Epoxydes Derivant du (E)‐Stilbène et de L'α‐Méthylstyrène Par la Méthode de Payne
Authors: Ben Hassine B. , Gorsane M. , Pecher J. , Martin R. H. 
Published: September 2010

AbstractEpoxidation of (E)‐stilbene and α‐methylstyrene has been carried out using the (dl) nitriles 1, 2 and 3 in the presence of 98% H2O2. Chemical yields are collected in tables I and II (75–87%). The enantioselective epoxidation of the same substrates has been carried out using optically active 2‐cyano‐heptahelicene 4. Good chemical yields [(E)‐stilbene 92% and α‐methylstyrene 84%] and enantiomeric excesses [(E)‐stilbene 99.8%±2 and α‐methylstyrene 97.6%±2] have been obtained.
The ESR Spectrum Near G=2 of Carbonated Calciumapatites Synthesized at High Temperature
Authors: Callens F. J. , Verbeeck R. M. H. , Matthys P. F. A. , Martens L. C. , Boesman E. R. , Driessens F. C. M. 
Published: September 2010

AbstractThe ESR spectrum near g=2 of several carbonated calciumapatites synthesized at high temperatures, is studied as a function of incident microwave power. It is shown that the ESR signal observed is the composition of several powder spectrum contributions, arising from different paramagnetic centres. At low microwave power, the spectrum essentially reduces to be superposition of two very related spectra, probably to be ascribed to two CO33− radicals. The major component is assigned to CO33− at a phosphate site, while the other can be due either to a CO33− at a hydroxyl site or a surface CO33−.
The Dissociation of Monoprotic Acids. Influence of Composition Changes in the Solution on the Potentiometric Determination at Constant Ionic Strength
Authors: Rogiers Rony , Vantomme Paul , Bouserie Frank L. G. , Thun Harry P. 
Published: September 2010

AbstractBy use of a glasselectrode or a sodium ISE the authors try to determine secondary effects influencing the emf values when studying the dissociation of α‐OH‐isobutyric acid at I=1 and 25°C.