bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination Voltamperometrique D'Iodures A L'Aide D'Une Electrode Tournante a Renouvellement Constant De La Surface
Authors: Stoytcheva Margarita , Noninski Christo 
Published: September 2010

AbstractDes études ont été effectuées sur 1′emploi d'une électrode tournante à renouvellement constant de la surface pour des analyses dans le domaine de potentiels positifs. La reproductibilité des résultats et 1′influence de différents facteurs‐vitesse de renouvellement de la surface de l'electrode, concentration du dépolarisant, nature de l'électrolyte indifférent, sur le courant de diffusion et le potentiel de demi‐vague lors de l'oxydation des iodures, ont été déterminées. On a trouvé que les courbes voltammétriques, sans oscillations et d'une parfaite reproductibilité, rendent la méthode propre pour la détermination qualitative et quantitative des iodures.
Synthesis of Two New Metal Ion Sequestering Agents: 1,4‐Diaza‐7‐Thiacyclononane‐N,N′‐Diacetic Acid and of 1,5‐Diaza‐8‐Thiacyclodecane‐N,N′‐Diacetic Acid
Authors: Wambeke D. M. , Lippens W. , Herman G. G. , Goeminne A. M. 
Published: September 2010

AbstractThe synthesis of two new multidentate metal ion sequestering agents, 1,4‐diaza‐7‐thiacyclononane‐N,N′‐diacetic acid (III) and 1,5‐diaza‐8‐thiacyclodecane‐N,N′‐diacetic acid (VI), using the Richman‐Atkins procedure and subsequent derivatisation with ethyl bromoacetate is described.
Podands Based on 1,4,5,8‐Tetra‐Azaphenanthrene and Their Complexation With Ru2+
Authors: Nasielski J. , Chao S.‐H. , Nasielski‐Hinkens R. 
Published: September 2010

AbstractSummary. New podands, based on 1,4,5,8‐tetra‐azaphenanthrene, have been synthesized from 2‐chloro‐1,4,5,8‐tetra‐azaphenanthrene 3; when the anchoring group is a nitrogen atom, the corresponding podands are, however, unstable. When reacted with Ru2+in an ionizing solvent, podands tris(2‐(2‐(1,4,5,8‐tetra‐azaphenanthryloxy))ethyl)methane 4c and tri(2‐(2‐(1,4,5,8‐tetra‐azaphenanthryloxy))ethyl)trimesoate 9 give only polymeric complexes; in chloroform, complexation stops at bis‐chelation, giving two types of structures. The most intriguing is the twisted type (12, 13) where one of the chelating group has been inverted, giving rise to an unprecedented flattened Ru2+octahedron.
Réduction Asymétrique D'Allylamines Et Dérivés a L'aide De Complexés Du Rhodium
Authors: Fahrang Roya , Sinou Denis 
Published: September 2010

AbstractProchiral allylic amines are reduced as their chlorhydrates using rhodium complexes of various 1.2‐, 1.3‐ and 1.4‐diphosphinocompounds with enantiomeric excess (e.e.) up to 60%. The N‐acetyl derivatives of the allylic amines are reduced with low e.e.
A Novel Rearranged Abietane Diterpene From Coleus barbatus
Authors: Kelecom Alphonse , Medeiros Walter L.B. 
Published: September 2010

AbstractThe new diterpene 9(10→20)‐abeo‐abieta‐8,11,13‐trien‐10β,11,12‐triol (1), has been isolated from the stems of Coleus barbatus Bentham and its structure determined from spectral data and hemisynthesis.
The Application of DSC in the Physico‐Chemical Characterization of Transparent Oil‐Water Gels
Authors: Christine Provost 
Published: September 2010

AbstractTransparent oil‐water gels formed in a four‐componentsystem composed of two nonionic emulsifying agents, Cetiol(R) HE and Eumulgin(R) B3, of an oily liquid, isopropyl palmitate, and of water were investigated by differential scanning calorimetry. A comparison was made with the thermal behaviour of their separate components and of some of their binary and ternary mixtures. The results show that DSC can supply information concerning some elements controlling the formation of transparent oil‐water gels. These elements include the hydration of the emulsifiers, various intercomponent interactions, and the nature of the binding forces in the gel structure. DSC thus contributes to clarifying the mechanisms behind this gelformation.
A Search For Phenolic Protection in Virginiamycin S
Authors: Sharma N. K. , Anteunis M. J. O. 
Published: September 2010

AbstractIn order to be able to mask the hydroxyl grouping of the pipecolic acid residue in Virginiamycin during alkaline (NaOH) and acidic (Tfa) break‐down procedures and to use peptidic fragments coming thereof for further reconstitution by classical peptide synthesis procedures, we have investigated several candidates for protection/deprotection. Thus the phenacyl derivatives (4 & 5), the allyloxycarbonyl derivative (6), the trichloroethyloxycarbonyl derivatives (8 & 9) and the 2,4‐dinitrophenyl derivative (10) have been prepared. Among these none were stable in aqueous basic conditions. The Alloc‐ (6) the Troc (8) and Dnp‐derivative (10) may have some applications under acidic conditions.
Behaviour of Cyclopropanes Bearing Capto‐Dative Substitution Upon Electron‐Impact and Flash‐Vacuum Pyrolysis Conditions
Authors: Chen Lin‐Zhi , Flammang Robert , Maquestiau André , Masamba Wayiza , Merényi Robert , Pommelet Jean‐Claude , Viehe Heinz‐G. 
Published: September 2010

AbstractTandem mass spectrometry has been applied to investigate the behaviour of bis‐captodative (cd) substituted cyclopropanes NC(SR)CCH2C(SR)CN [1, R=CH3; 2, R=tBu and 3, R=C6H5] upon electron impact (EI) and flash‐vacuum pyrolysis (FVP) conditions. Ring‐opening of the molecular ions of 1 followed by a 1,2‐hydrogen shift preceedes the fragmentation consisting mainly in the competitive losses of CH3S and CH2S. The least energy demanding reaction is however a methyl loss requiring also ring cleavage. The m/z 70 base peak is ascribed to cyanothioacylium ions (N=C‐=S) as indicated by the characteristic fragmentations induced by collision. Upon FVP conditions 1decays to the cd olefin 8 and the carbene 9 in competition with the extrusion of CH3S. and CH3. radicals at the highest temperatures. The behaviour of 2 upon both conditions is dominated by the chemistry of the t‐butyl substituents.Ring cleavage of the molecular ions of 3 preceedes also the fragmentation and induces rearrangement reactions yielding unexpected cyclohexadiene thione ions and C7H7+ ions. Upon FVP, C‐S bond homolysis readily occurs in competition with an elimination of a carbene molecule.
Recherche Des Sites D'Association Privilégiés Dans Des Molécules Polyfonctionnelles Par Rmn Du Carbone‐13
Authors: Seguin J. P. , Goethals G. , Moreau‐Descoing M. C. , Sarazin C. , Doucet J. P. 
Published: September 2010

AbstractThe carbon chemical shifts induced by hydrogen bonding have been measured for complexes between acetophenone and various alcohols. Linear relationships are obtained between corrected induced chemical shifts and the IR frequency shifts Δν. For carbonyl and C‐4 carbons, positive slopes are observed but a reverse effect results for C‐1 carbon. The hydrogen bond effects on carbon shifts of γ‐acetylpyridine are compared with those obtained for pyridine and acetophenone and we can conclude that the preferential association site for this polyfunctional compound is the nitrogen atom.
Polymères Thermostables: Thermoplastiques Et Thermodurcissables, Nouvelles Tendances
Authors: Sillion Bernard 
Published: September 2010

AbstractThis paper deals with the recent developments and the trends in the field of the heat resistant linear and thermosetting polymers.Two driving forces can explain the recent important efforts of research and development. The first target is the improvement of the processability for these materials and the second one is the strong demand for heat resistant macromolecules with specific properties such as low thermal expansion coefficient, low loss factor, low permittivity, improved toughness…Three types of material will be discussed in this paper: the linear polymers, the thermosetting resins and the semi‐interpenetrated networks (semi IPN's).The heat resistant linear polymers are generally amorphous, their high viscosities above the glass transition (Tg) limits the processability and the rather low Tg does not allow the high temperature application. In order to solve these problems, three main approaches have been studied. First the crystalline polyimides were prepared by introducing ether ketone sequences in the main chain so the high temperature properties are governed by the crystalline transitions. The second approach is the development of amorphous fully cyclized polymers exhibiting high Tg. These polymers were obtained with bulky or fluorinated group in the backbone. Finally a new concept is now developed, it is based on an intramolecular thermal rearrangement occuring in a flexible main chain and leading to a rigid one.Concerning the heat resistant thermosetting resins, the following problems have to be solved: the low solubility of this type of telechelic oligomers, their high melting point and, as a consequence, the very narrow processability window and the brittle character of the final network. For these purposes, the bis‐maleimide were crosslinked with allylic resins, a new soluble precyclized nadimide resin was developed and a new concept of redox reaction for the formation of phthalocyanine network was discovered.Very promising seems the semi IPN's networks in the field of the heat resistant polymers. Starting from the same diamine for the preparation of linear and thermosetting resins (bis‐maleimides and end‐capped acetylenic resins) allows a good miscibility of the mixture of linear and thermoset before curing.After crosslinking a phase segregation occurs. Good mechanical properties are observed above the Tg of the linear polyimide. The thermal stability of the semi‐IPN is strongly dependent on the nature of the thermosetting resins, so the semi‐IPN's with acetylenic are more thermostable than the semi IPN's with bis‐maleimide.
Relations Entre Structure Chimique Et Propriétés Mécaniques Dans Les Réseaux Époxydes
Authors: Halary Jean‐Louis , Cukierman Serge , Monnerie Lucien 
Published: September 2010

AbstractRelationships existing between chemical structure and the dynamic mechanical properties of epoxide networks are reviewed. This paper is focused on different model networks, prepared by the reaction between amines and DGEBA or DGEBD diepoxide monomers in stoichiometric proportions. The limit glass transition temperature, Tg∞, is shown to depend mainly on molecular flexibility of network chains and on crosslink density. Frequency dependence of Tg∞ obeys the time‐temperature superposition principle and can be described by a WLF‐type equation. However, the coefficients C1 and C2 in this equation depend on the molecular characteristics of the network, in agreement with free volume concepts. Values of elastic modulus well above Tg reflect mostly the influence of crosslink density. Surprisingly to some extent, application of rubber elasticity theory to these densely crosslinked systems yields very reasonable average network chain molecular weights Mc. In the glassy region, the mechanical relaxations β and γ are shown to originate from motions of ‐CH2‐CHOH‐CH2‐O‐ epoxide groups and of ‐(CH2)4‐ groups, respectively. Motions responsible for the β‐relaxation appear at the same temperature, whatever the network characteristics may be. On the other hand, both amplitude and broadening of the β‐relaxation loss peak are functions of crosslink density. From a practical viewpoint, these two characteristics influence markedly the plastic behavior of the networks and their elastic modulus at room temperature as well.
Polydichlorophosphazenes: Synthèse à Partir De Cl3Pnp(O)Cl2
Authors: D'Halluin G. , De Jaeger R. , Potin PH. 
Published: September 2010

AbstractThe polychlorophosphazenes of the general formulaThis alternate synthetic method is detailed. The course of this polycondensation has been investigated by 31P NMR spectroscopy (400 MHz).The assignments of all the 31P NMR signals of digomers have been performed. Knowledge of these 31P NMR properties leads to the understanding of the detailed mechanism of the polycondensation through the quantitative analysis of several intermediate species involved in the reaction.The major impurities formed during the synthesis of Cl3PHP(O)Cl2 have been identified. Their catalytic or inhibitant effect has been studied.The results obtained lead the prediction of an industrial exploitation of this process.
Solvent‐Extraction Behaviour of Nickel (II) With Lauric Acid
Authors: Hurtado Selva N. 
Published: September 2010

AbstractThe extraction of Ni(II) using lauric acid dissolved in toluene was carried out in the pH 5‐7 range. The influence of the acetate ions on extraction percentage and stoichiometry of the extracted species was studied and it was shown that they do not affect the range of concentrations examined, namely, from 0.1 M to 1 M. The extraction percentages of Ni (II) were considerably upgraded by the addition of 1–10 phenanthroline hydrochlorate. The optimum concentration of 1‐10 phenanthroline hydrochlorate/nickel (II) was found to be equal to 1.5.Finally, a description is given of the stripping processes for Ni (II) with sulphuric acid from organic phases obtained by extraction with lauric acid in aqueous solutions of Ni (II) either free or forming complexes with the 1‐10 phenanthroline hydrochlorate.
The Configuration of Palustrol and Related Compounds
Authors: Braekman Jean‐Claude , Daloze Désiré , Stoller Catherine , Declercq Jean‐Paul 
Published: September 2010

AbstractThe structure of diol 5, an autoxidation product of (+)‐palustrol, has been determined by X‐ray diffraction analysis. From these data, the relative and absolute configurations of (+)‐palustrol and of several related aromadendrane derivatives could be established.
Synthesis of 2′,3′‐Disubstituted 3′‐Deoxythymidine Derivatives
Authors: Herdewijn P. , van Aerschot A. 
Published: September 2010

AbstractReaction of 2 with DAST followed by detritylation and monomethoxytritylation afforded 34% of the fluorinated nucleoside 3. This intermediate was used to prepare the 3′‐azido‐2′‐fluoro‐and 2′,3′‐difluoro substituted 5‐methyluridine analogues 7 and 11, respectively.
Le Diethylacetal Du Cyano‐3 Propene‐2 Al Comme Equivalent Synthetique D'Heterocumulenes Fonctionnels
Authors: Lassalle Gilbert , Grée René 
Published: September 2010

AbstractThe easy transformation of pyrrolidine 4 in 5 and then into 7 shows that the diethylacetal of 3‐cyano 2‐propenal can be considered as a useful synthetic equivalent of the functionnalized heterocumulenes 2 and 3.
The Synthesis, Vibrational Spectra and Thermal Analysis of Different PD(II) Polymers with Planar Dithiooxamides
Authors: Bellaihou M. , Weyten H. , Desseyn H. O. 
Published: September 2010

AbstractDifferent polymeric complexes of Pd(II) with planar dithiooxamides have been synthesized. The infrared spectra and the thermal analysis of these new compounds are discussed.
Solvent ‐ Extraction of Ag(I) and CD(II) with Rosin
Authors: Selva N. Hurtado 
Published: September 2010

AbstractThe extraction of Ag(I) and Cd(II) cations from their respective aqueous solutions with rosin dissolved in toluene has been studied. In both cases yields close to 100% were obtained in one single stage. At the same time, the influence on the process of pH, ionic force and concentration of the extractant was analysed.The stripping of each one of the cations in the rosin‐in‐toluene solutions was also carried out, yields of almost 100% being obtained in a single stage in both cases. Stripping of Ag(I) requires very important excesses of sulfuric acid and it was only possible to use stoichiometric amounts of this acid from Ag(I) concentrations of 7 g/l. In the case of Cd(II) concentrations equal or higher than 4.5 g/l of cation are required.Finally, a separation method for both cations, Ag(I) and Cd(II) was developed on an experimental scale which also makes it possible to obtain stripped aqueous phases wherein the Ag(I) in one of them and the Cd(II) in the other are 25 times more concentrated.
Complexes of Salicylaldehyde Ferrocenylcarbonylhydrazone with Some Metal(II) Ions
Authors: Yong‐Xiang Ma , Zheng‐Zhi Zeng , Hong‐Sui Sun , Guo‐Sheng Huang 
Published: September 2010

AbstractThe complexes of salicylaldehyde ferrocenylcarbonylhydrazone with some metal(II) ions have been prepared. Their elemental analyses and IR spectra show that the hydrazone coordinates to the central ions in the enol form with a 1:1 stoichiometry. The complexes manifest subnormal magnetic moments and the electronic spectra correspond to the square‐planar configuration.
Synthesis and Characterization of New Rhenium (V) Complexes of Tetradentate Schiff Base Ligands
Authors: Amer S. A. 
Published: September 2010

AbstractReaction of trichloro‐oxo‐bis (triphenylphosphine) rhenium (V) and Schiff bases derived from some aliphatic diamines and 2‐hydroxy‐1‐naphthaldehyde in the presence of triethylamine gives as anionic complex (ReOLCl2)−, where L is a tetradentate Schiff base ligand. On the basis of various physical properties, the complexes are assigned seven coordinate. The structure of the complex depends on the length of the methylene chain of the ligand. The ReO−3+ complexes form monomeric or polymeric complexes by ligand bridging.
Stéréochimie de (2S, 4S, 5R;2S, 4S, 5S)‐ et (2R, 4S, 5R;2R, 4S, 5S)‐2‐alkyl‐1,3,4‐triméthyl‐5‐phénylimidazolidines déterminée par RMN‐−1H et ‐−13C
Authors: Tytgat D. , Gelbcke M. 
Published: September 2010

AbstractThe condensation of (1R,2S) or (1S, 2S)‐N,N′‐dimethyl‐1‐phenylpropane‐1,2‐diamines with aldehydes gives respectively two diastereomeric 2‐alkyl‐1,3,4‐trimethyl‐5‐phenylimidazolidines. At thermodynamical equilibrium the major isomer in the erythro series is this one where the substituents at position 2 and 4 are ”cis“. In the threo series, the major isomer has the substituents at position 2 and 4 ”trans“.
Synthesis and 2‐D NMR Characterization of New Precursors of Electronically Conducting Polymeric Films: 1‐ and 2‐[2‐(1‐adamantyl)2‐oxo‐ethoxy]‐naphthalenes
Authors: Moustafid T. El , Hedayatullah M. , Seba H. B. , Pigenet C. , Ancian B. 
Published: September 2010

AbstractThe synthesis and 2D NMR (J resolved −13C, −1H and −13C, −1H correlation) characterization of new adamantylated electronically conducting polymer precursors are described.
Nouvelles méthodes de synthèses des dérivés du pyrazole et de l'isoxazole a partir de la phényl‐7 diazépine‐1,4 thione‐5
Authors: Chammache M. , Essassi E. M. , Salem M. , Zniber R. 
Published: September 2010

AbstractIn this work, two new pyrazole and isoxazole derivative have been synthetized from 7‐phenyl‐1,4‐diazepine‐5‐thione. These products have been characterized by −1HNMR, IR, MS and microanalysis.
The N‐Amidinoethylation of 2‐Aminoethanol by Michael Reaction with a N,N′‐Disubstituted Propenamidine
Authors: Fuks Robert , Trémerie Bernadette , Khamlichi Samir , Muller Daniel , Josefonvicz Jacqueline 
Published: September 2010

AbstractThe addition of 2‐aminoethanol 1 to the propenamidine 2 under neutral conditions lead to 1:1‐ and 1:2‐ adducts 3 and 4 by the Michael addition of the amino end‐ group to the C = C double bond of 2.
”In situ“ Silylation with Trimethylsilyl Cyanide an Outstanding Protocol for Fast Peptide Synthesis a Synopsis
Authors: Anteunis M. J. O. , Becu Chr. , Becu Fr. 
Published: September 2010

AbstractThe use of trimethylsilyl cyanide as a potent ”in situ“ silylating agent and its compatibility with most classical functionalities employed during solution phase peptide syntheses allows repetitive peptide chain elongations (including linear Head‐to‐Tail) with a minimum of chemical steps and manipulations. The outstanding features are: the upscaling facilities, the simplicity and the high purity of the final peptides exempt of stereomutation.
A Kinetic study of C3O2/H‐Systems: Rate Constant of the Reactions C3O2 + H, HCCO + H and HCCO + O2 at T = 285 ‐ 566 K
Authors: van De Ven P. , Peeters J. 
Published: September 2010

AbstractThe reaction of C3O2 with H was studied under first order conditions at excess H‐atoms in the temperature region 285‐566K and at a pressure of 2 Torr. The experiments were carried out by means of a discharge‐flow technique combined with molecular‐beam mass spectrometry. The rate constant forC3O2 + H → HCCO + COwas found to beK1 = (1.3±0.2) 10−11 exp 〈(−1320±80)K/T〉 cm3 molec−1s−1The kinetic coefficients of the subsequent reactions of HCCO with H and O2 were derived using deductive modelling techniques. The experiments were carried out at room temperature. The resulting rate constants obtained (with 95% confidence region) were:HCCP + H → productsk = 2.0 (1.0−4.0) 10−10 cm3molec−1s−1HCCO + O2 → productsk = 1.4 (1.0−2.0) 10−12 cm3molec−1s−1
Model Studies Directed Towards Microalga Polyether Toxins
Authors: Alvarez Eleuterio , Díaz Maria Teresa , Zurita Dácil , Zárraga Miguel , Martín Julio D. 
Published: September 2010

AbstractIn view of the described results in acid‐induced polyepoxide cyclizations, the biosynthesis of fused polyether toxins may be better explained by a stepwise mechanism through oxonium ion intermediates acting on the enzyme‐bonded polyepoxide precursor. A new synthetic strategy for the regio‐ and stereospecific synthesis of heterosubstituted oxolane and oxane rings involving intramolecular iodoetherification of 2,3‐epoxy‐cycloalken‐1‐ols was studied. Cyclization/solvolysis of 2,3‐epoxy‐cycloalk‐5‐en‐1‐ols proceed with complete regio‐ and stereoselectivity to yield cis‐2,6‐dialkyl‐3,5‐oxygenated oxane rings and thus assemble in two steps the key structural units present in marine syn‐trans fused polyether toxins. A highly efficient cyclization reaction of 2,3‐epoxycyclonon‐6‐en‐1‐one leading to the oxepane system is described. The silver(I)‐induced solvolysis occurs in high yield under mild conditions and the resulting cyclic system may be manipulated via oxidative carbon‐carbon bond cleavage leading to a functionalized α, α′‐dialkyl β,β′‐oxygenated oxepane ring with defined cis‐syn‐cis stereochemistry.
Enantioselective Catalysis with Metal Complexes Containing Heterocyclic Ligands
Authors: Pfaltz Andreas 
Published: September 2010

AbstractChiral C2‐symmetric semicorrins, a class of bidentate nitrogen ligands, are readily prepared in enantiomerically pure form starting either from D‐ or L‐pyroglutamic acid. They possess a number of features that make them attractive ligands for enantioselective control of metal‐catalyzed reactions. (Semicorrinato)copper complexes have been used as efficient catalysts for the enantioselective cyclopropanation of olefins with diazo compounds. Using (semicorrinato)cobalt complexes as catalysts, α,β‐unsaturated carboxylic esters and amides can be enantioselectively reduced with sodium borohydride, giving the corresponding saturated esters and amides with enantiomeric excesses up to 98%.
The Reaction of Quinoxaline‐ and Phenazine‐N‐Oxides with Thionyl Chloride and Paratoluenesulfonyl Chloride
Authors: Nasielski J. , Heilporn S. , Chauveheid E. , Poppe K. , Nasielski‐Hinkens R. 
Published: September 2010

Abstract2,3‐Diphenylquinoxaline‐N‐oxide 1 with thionyl chloride gives only 5‐chloro‐ and 6‐chloro‐quinoxaline and very little deoxygenation. Phenazine‐N5‐oxide 2, in the same conditions, gives mainly 2‐chlorophenazine and minor amounts of 1‐chlorophenazine, but here deoxygenation is an important pathway. Freshly recrystallized para‐toluenesulfonyl chloride gives a high chlorination‐to‐tosyloxylation ratio. All these results point to a variable ability of acid chlorides to yield homocycle chlorination or acyloxylation; this is confirmed by the observation that phenazine‐N5‐oxide and phosphoryl chloride give fair amounts of aryl phosphate.