bluuebunny/crossref_metadata_2025_split huggingface dataset:
Collective Cohesion Forces in Polymers
Authors: Huyskens P. , Vandevyvere P. , Colemonts‐Vandevyvere Ch. 
Published: September 2010

AbstractCollective cohesion forces are a set of normal cohesion forces the origins of which exhibit a regularity in their spatial distribution. Atoms, molecules or segments that undergo their action display collective coupled motions where the neighbours do not change or identity. Such particular kind of motion can be called “rigidity”. The repetitive character of the polymeric chain renders the segments particularly susceptible to generate collective cohesion forces but this tendency is not the same for each of them. Rigid segments have a lower chemical potential than fluid segments. This is the case for the crystalline parts of the semi‐crystalline polymers. The tendency of some sequences to generate collective cohesion forces is so great that in most cases rigid domains are spontaneously formed where the spatial regularity does not extend to the three dimensions, what makes them less detectable by diffraction methods. But these rigid domains being connected with other zones deprive the last ones from macroscopic mobility and no crystallization can take place. Moreover, as evidenced by dipolar measurements, even in true solutions given sequences of segments are regularly involved in ephemeric rigid domains, and have therefore a lower chemical potential. Phase separation occurs when, as a consequence of the change of solvent or temperature, some rigid domains become permanent. As a consequence of this inherent inequality between the segments, the criterion of phase separation in polymer solutions is the existence of two states α and β in which the lowest chemical potential or the segments is the same. This fundamentally differs from the liquid‐liquid treatment of Flory.
Synthèse De Peroxydes Allyliques Dissymétriques
Authors: Chiron‐Charrier Muriel , Campagnole Monique , Bourgeois Marie‐Josèphe , Montaudon Evelyne 
Published: September 2010

AbstractUne synthèse de peroxydes allyliques dissymétriques est décrite à partier des mésylates convenables. La nature du solvant est un facteur déterminant de la régiosélectivité de la réaction.
Photolyse De HI Dans Une Matrice Hydrocarbonée Vitreuse à 77 K
Authors: De Laet M. , Tilquin B. 
Published: September 2010

AbstractStable products from the photolysis of HI in methyl‐3 pentane (3 MP) or dimethyl‐2,3 butane (23 DMB) quenched solid at 77 K are analyzed by capillary gas chromatography. Selective formation of a tertiary radical is proposed for the 23 DMB/HI system; in 3 MP/HI, C‐H bond rupture is also localized at the weakest tertiary bond, however the scission is not selective.
Détermination Bioélectrocatalytique Du Glucose Dans Le Sérum Sanguin
Authors: Nankov Nanko , Stoytcheva Margarita , Mladenova Emilia , Zlatev Rumen 
Published: September 2010

AbstractA bioelectrocatalytical method with a chronoamperometric registration for glucose determination in blood serum was proposed. It satisfies the criterions for evaluation of the results' quality of the quantitative analyses. It presents certain advantages in comparison with the actually adopted clinical methods and in comparison with some other bioelectrocatalytical methods.
Polyoxadiazoles and Polytriazoles as New Heat and Solvent Resistant Membrane Materials
Authors: Hensema E. R. , Gebben B. , Mulder M. H. V. , Smolders C. A. 
Published: September 2010

AbstractPolyoxadiazoles and polytriazoles belong to the class of thermally stable and chemically resistant polymers. Both polymers are prepared out of a processable polyhydrazide. The kinetics of the cyclo dehydration reaction which converts a polyhydrazide into a polyoxadiazole was studied and the gas separation properties of a polytriazole and its thermal behaviour were investigated.
Synthèse Et Étude De La Dégradation Photochimique De Tensio‐Actifs Cationiques Photoclivables
Authors: Strub‐Leconte M. P. , Riess G. 
Published: September 2010

AbstractA homologous series of photocleavable cationic surfactants was prepared. These aryl‐alkyl‐ketone type surfactants have the following structure chemical structure imageTheir critical micelle concentration in water was determined. The photodegradation study has shown that the cleavage occurs with a high quantum yield by a Norrish II mechanism with formation of alkene, substituted acetophenone and cyclobutanols. The photochemical yield of cleavage reaches 75% with formation of a hydrophilic (substituted acetophenone) and a hydrophobic derivative (alkene).
Linear Dispiro Decanes and Tetrazolines from Organic Azides and Heavy Diamino Carbene Analogues R2M, M = Ge, Sn
Authors: Neumann Wilhelm P. , Obloh Ronald C. 
Published: September 2010

AbstractAzides R‐N3 (R = aryl, acyl, cyclohexyl), react at ‐30°C spontaneously with the diaminostannylene 1 to give the distannadispiro[3.1.3.1]decanes 2 and 3, or with the diaminogermylene 4 to give the digerma analogues 5. The dispiro[3.1.3.1]decane systems, with an unusual linear combination of three four‐membered rings, were fully characterized by X‐ray and other spectroscopic methods. 4 gives, with 2 mol phenyl azide, the germatetrazoline 6, whose structure is also evidenced by X‐ray spectroscopy.
Synthese Chiraler Phosphinoxide Und Phosphine Durch Michaelis‐Arbuzov‐Umlagerung
Authors: Brunner H. , Zettlmeier W. 
Published: September 2010

AbstractSeveral phosphinites and phosphites, derived from chiral alcohols, were synthesized. The phosphinites were subjected to a I2‐catalyzed Michaelis‐Arbuzov rearrangement. Phosphinites derived from primary alcohols give satisfactory yields of the corresponding phosphineoxides. Phosphinites synthesized from secondary alcohols also undergo the rearrangement but numerous byproducts appear in the reaction mixtures. Optical resolutions of chiral phosphineoxides by crystallization with optically active acids were not successful. The corresponding phosphines can easily be prepared by reduction of the oxides with trichlorosilane.
Enantioselektive Katalyse, 63 [1] Optisch Aktive Phosphine Aus Dicarbonsäuren Und Ihr Einsatz in Der Enantioselektiven Hydrierung
Authors: Brunner H. , Zettlmeier W. 
Published: September 2010

AbstractTwo optically active bident phosphine ligands were synthesized from derivatives of succinic acid as starting materials. The optical resolution of the acids was carried out with cinchonidine and (S)‐α‐phenylethylamine. In the Rh‐catalyzed enantioselective hydrogenation of α‐acetamidocinnamic acid, the bisphosphine with a phenyl substituent in the 2‐position of the four‐carbon chain gave an enantiomeric excess of 17%. The enantiomeric excess was twice as high with the corresponding thienyl substituted bisphosphine.
Structures of Two Planar Flavones: 4′‐Methoxyflavone and 3′,4′‐Dimethoxyflavone
Authors: Wallet J. C. , Gaydou E. M. , Tinant B. , Declercq J. P. , Baldy A. 
Published: September 2010

Abstract(I): C16H12O3, Mr=252.27, monoclinic, P21/n, a=16.446(3), b=3.887(1), c=19.565(4)Å, ß=106.59(l)°, V=1198.5(4)Å3, Z=4, Dx=1.40g·cm−3, MoKα, λ=0.71069Å, μ=1.04cm−1, F(000)=528, T=291K, R=0.046 for 1904 observed reflections. (II): C17H14O4, Mr=282.30, monoclinic, C2/c, a=30.844(7), b=4.073(2), c=26.119(4)Å, ß=124.25(1)°, V=2713(1)Å3, Z=8, Dx=1.38g·cm−3, MoKα, λ=0.71069Å, μ=1.06 cm−1, F(000)=1184, T=291K, R=0.043 for 1515 observed reflections. Both molecules are essentially planar with dihedral angles between the benzopyran and the aromatic ring least squares mean planes of 2.1(5)° for (I) and 6.2(5)° for (II).
Synthesis, Spectroscopic Characterization and Antitumour Activity of Diorganotin(IV) Derivatives of N‐Substituted Ortho‐Aminobenzoic Acid
Authors: Meriem Abdelkader , Biesemans Monique , Willem Rudolph , Mahieu Bernard , de Vos Dick , Lelieveld Peter , Gielen Marcel 
Published: September 2010

AbstractFour compounds of the type [(o‐RNH‐C6H4COO)(CH3CH2CH2CH2)2Sn]2O and [(o‐CH3NH‐C6H4COO)(CH3)2Sn]2O have been prepared, characterized by 1H, 13C, 119Sn NMR, and by Mössbauer and mass spectrometry. They have been tested in vitro against two human tumour cell lines, nl. MCF‐7 (mammary tumour) and WiDr (colon carcinoma), and found to score slightly better than cis‐platin but markedly less than other cytostatic agents.
Reduction of Acetals with CpTiCl3‐LiAIH4
Authors: Shaozu Wu , Yin Chen , Yulan Zhang 
Published: September 2010

AbstractThe reduction of cyclic acetals and ketals derived from aromatic or aliphatic aldehydes and ketones with CpTiCl3‐LiAlH4 system in diethyl ether at 30°C affords the corresponding hydroxyethyl ethers and the corresponding alkyl benzene or aliphatic hydrocarbons.
Étude Théorique de Réactions de Couplage de Radicaux Libres
Authors: Leroy G. , Sana M. , Espinosa‐Garcia J. 
Published: September 2010

AbstractAb initio quantum mechanical methods are used to calculate the thermodynamic and kinetic parameters for the reactions of NH2O with NH2 and NHOH. It is found that these dissymetrical coupling involving a highly stabilized radical are both characterized by a non‐negligible activation energy.
Reactivity of YBa2Cu3O7‐x Towards Water and Humid Air
Authors: Vlaeminck H. , Hoste S. 
Published: September 2010

AbstractDetailed XPS studies with emphasis on special characteristics of the Ols and Cu2p3/2 core‐levels, thermogravimetry, X‐ray diffraction, infrared spectroscopy and scanning electron microscopy have been used to study the degradation of the superconducting phase YBa2Cu3O7‐x in contact with water under various conditions.It is shown that the superconducting YBa2Cu3O7‐x phase in contact with water or humid air decomposes into CuO, Ba(OH)2, Y2BaCuO5 and oxygen and also yields BaCO3 by reaction with atmospheric CO2. A Br2‐EtOH etching solution removes surfacial BaCO3. Furthermore, this treatment may yield a passivation layer inhibiting further decomposition.
Hydrogénation du Monoxyde de Carbone II ‐ Influence du support et du cesium sur les propriétés du Nickel‐Molybdène
Authors: Ghazi M. , Barrault J. 
Published: September 2010

AbstractThe selectivity for alcohols formation in the carbon monoxide hydrogenation reaction on nickel molybdenum catalysts increased when zinc oxide was used as a support, where it reached 50%. The same trend was observed when an alkaline metal such as cesium was added to the catalyst. Moreover when the surface area of the zinc support was increased from 10 to 80 m2·g−1 the selectivity was multiplied by 20 with a selectivity for alcohol formation still greater than 70% after 20 hours time on stream.
A Reexamination of the Retro‐fries Rearrangement of Some o‐Hydroxyketones
Authors: Martin Robert , Lafrance Jean Ronald , Demerseman Pierre 
Published: September 2010

AbstractThe retro‐Fries rearrangement, catalyzed by protic and Lewis acids, was studied for some o‐hydroxyketones. The results are consistent with the mechanism of an heterolytic cleavage and rearrangement. It appears that, in general, Lewis acids do not induce the retro‐Fries rearrangement of o‐hydroxyketones. However, in certain cases, it may be brought about by the presence of a protic acid generated in situ, from a solvent‐catalyst interaction.
Destruction du Paraoxon par une Nouvelle Série de Sels de N‐Alkyl Hydroximinomethylpyridinium
Authors: Lion Claude , Despagne Bruno , Delmas Gérard , Fosset Laurent 
Published: September 2010

AbstractThe facile hydrolysis of toxic organophosphorus compounds is of interest since these compounds have been used as insecticides or potent chemical warfare agents. The high reactivity of oximate ions associated with micelle forming molecules against Paraoxon (O,O‐diethyl O‐paranitrophenylphosphate) is tested with new N‐alkyl hydroximinomethylpyridinium salts. The position of the hydroximinomethyl function (ortho, meta or para), the length of the alkyl chain and the nature of the anion are discussed.
Poly‐(2,5‐furanylene Vinylene) Prepared from a Precursor Polymer Soluble in organic Solvents
Authors: Dierick T. , De Schrijver D. , Eevers W. , Geise H. J. 
Published: September 2010

AbstractPoly‐(2,5‐furanylene vinylene), (PFV) is prepared by thermal treatment of films cast from THF or CHCl3 solutions of a methoxy precursor polymer. The sequence of reactions is described starting from 2,5‐dimethylfuran. The new methoxy precursor is characterised by its IR and 13C‐NMR spectra, while GPC (polystyrene calibration) gives MD = 4300, MW = 11800, degree of polymerisation, n = 35, degree of polydispersion, dp = 2.8.UV spectra suggest isolated furan units, in accordance with the proposed structure. Some premature elimination is also observed. Maximum conductivity p = 20 Ω−1 cm−1 is reached after doping the PFV film for 4 min in iodine vapour.
Unique 1′‐O‐boc protection of Virginiamycin S and Resulting Resistance Against Sodium Hydroxide
Authors: Moerman Marc C. , Anteunis Marc J.O. 
Published: September 2010

AbstractThe picolinic hydroxyl in Virginiamycin S1 (VS1; 1a) can be protected with di‐tert‐butyloxycarbonate affording the tert‐butyloxycarbonyl derivative thus yielding VS1 −1′ ‐O‐Boc (1b) in a fast and quantitative conversion without concomitant betaine (1c) formation. Once protected however, the lactone bond in 1b can no longer be cleaved under mild alkaline conditions. A possible explanation is given.
Synthesis of Pyrylium Salts with Various Anions
Authors: Dinculescu A. , Balaban T. S. , Popescu Cristina , Toader D. , Balaban A. T. 
Published: September 2010

AbstractFour methods are described for obtaining pyrylium salts with various anions which influence strongly their solubility, their reactivity and ease of purification; (i) direct synthesis; (ii) conversion of a pyrylium salt into its pseudobase (1,5‐enedione) which is recyclised with the acid corresponding to the desired anion; (iii) anion metathesis and (iv) reductive stripping of the anion with sodium borohydride in carboxylic acid media which also provides a carboxylate anion. Method (iv) is new and is complementary to the direct metathesis (iii) because it allows the replacement of anions stemming from strong acids which confer insolubility to pyrylium salts with anions derived from much weaker acids and which give more soluble salts. The present paper also describes some new pyrylium salts obtained by all methods (i‐iv). One may mention among these 2,4,6‐trimethylpyrylium hydrogen isobutenedisulfonate which results directly from sulfuric acid, acetic anhydride and isobutene or t‐butanol at temperatures below 30°C.
Synthesis and Spectrokinetic Properties of Photochromic Spiropyrans
Authors: Samat A. , De Keukeleire D. , Guglielmetti R. 
Published: September 2010

AbstractThe synthesis and spectrokinetic properties of photochromic spiropyrans in solution are reported. The most important results obtained during the last two decades, including the synthetic access to azaheterocyclic and non‐azaheterocyclic spiropyrans are described, as each series confers its own particularities to the photocoloration. The influence of the structure (skeleton, heteroatoms, substituents) on the stability of the photomerocyanines is discussed in terms of electronic (correlation of Hammett type) and steric effects. The role of structural parameters and of solvent effects on the electronic distribution of the colored form is also emphasized.
Study of Higher Order Electrochemical Reactions Involving an Insoluble Product with Several Chronopotentiometric Techniques
Authors: Molina A. , López‐Tenés M. , Serna C. , Albaladejo J. 
Published: September 2010

AbstractThe general theory for higher order electrochemical reactions involving an insoluble product at the DME, by using different chronopotentiometric techniques, is presented. The expressions corresponding to a null blank period, to an expanding plane electrode and to spherical and plane stationary electrodes, can be deduced as particular cases of the equations obtained in this work. The particular features of the potential‐time curves are discussed and methods for determining kinetic parameters and the conditional (formal) potential are proposed.
Heptacoordination in Diorganotin Pyridine‐2,6‐Dicarboxylates in DMSO Solution
Authors: Gielen Marcel , Acheddad Mohamed , Bouâlam Mohamed , Biesemans Monique , Willem Rudolph 
Published: September 2010

AbstractThe 1H NMR spectra in the pyridine proton region of six 2,6‐pyridinedicarboxylato‐(phenyl) (organo)tin(IV) compounds in DMSO‐d6 solutions exhibit a pattern that, together with 13C coupling data and 119Sn chemical shifts, can be interpreted by a heptacoordinated pentagonal bipyramidal structure in which the tin atom is likely to be surrounded by two DMSO ligands in equatorial positions.
Quaternary Salts of 1,2‐Bisazolyl‐ and 1,2‐Bisbenzazolylethanes
Authors: Torres Jesús , Lavandera José Luís , Cabildo P. , Claramunt R. M. , Elguero José 
Published: September 2010

AbstractEleven new heterocyclic mono‐and diquaternary salts have been prepared by reaction of 1,2‐bisazolyl‐ and 1,2‐bisbenzazolyl‐ethanes with methyl sulfate or methyl fluorosulfonate. Their structure has been established by means of 1H and 13C NMR spectroscopy. Homonuclear COSY and NOESY experiments and 2D‐heteronuclear correlations have been performed when necessary to assign all NMR signals.
Functionalized Chloroenamines in Aminocyclopropane Synthesis ‐ VII. A Diastereocomplementary Approach to Amino‐Bicyclo[n.1.0]Alkanenitriles on the Basis of Chlorinated Enamines
Authors: Vilsmaier Elmar , Stamm Thomas , Dauth Werner , Tetzlaff Claus , Barth Stefan 
Published: September 2010

AbstractReductive dechlorination of amino‐chlorobicycloalkanenitriles 5a‐c was achieved by sodium in tert.butyl alkohol/THF to give the bicyclic nitriles 6a‐c. LiAIH4 as dechlorination reagent caused a ring opening reaction with 5b,c producing diamines 7b,c. The bicyclic chloro compounds 5b,c could by obtained from enamines 1 via dichloroenamines 4. Monochlorination of 1b,c and subsequent cyclopropanation with cyanide yielded endo‐bicycloalkanenitriles 3b.c. Compounds 3 and 6 thus generally can be synthesized in a diastereocomplementary way starting from enamines 1.
Industrial Implications of the Thermal Behaviour of Pseudoboehmite
Authors: Decleer Jos G. M. 
Published: September 2010

AbstractPseudoboehmite powder is widely used as a precursor material for the manufacturing of shaped catalyst carriers. After processing, it provides unique properties as high surface area, porosity and strength. The conversion of pseudoboehmite to gamma alumina is determined to a large extent by the manufacturing route of the powder. Physical properties like particle size and shape, crystallinity, porosity, etc. have a distinct influence on the thermal behaviour. This thermal and physical characterization has allowed to translate basic powder properties into the industrial practice of catalyst carrier manufacturing. Unit operations as mix‐mulling, extrusion, drying and calcination are clearly affected by powder characteristics.
Influence of the Incorporation of 1‐(2,3‐Dideoxy‐β‐D‐Erythro‐Hexopyranosyl)‐Thymine on the Enzymatic Stability and Base‐Pairing Properties of Oligodeoxynucleotides
Authors: Augustyns Koen , van Aerschot Arthur , Urbanke Claus , Herdewijn Piet 
Published: September 2010

Abstract1‐ (2,3‐dideoxy‐β‐D‐erythro‐hexopyranosyl) thymine was used at several positions as nucleoside substitute in the synthesis of oligonucleotides using the H‐phosphonate chemistry. A 13‐mer with one hexose nucleoside substitution at each end had equivalent hybridization properties as compared to the non‐modified 13‐mer. However, addition of a second analogue at each end or modification in the middle of a 13‐mer caused a sharp decrease in melting temperature. Substitution at the 3′‐end with two nucleoside analogues was necessary to withstand the action of snake venom phosphodiesterase.
Ft‐Ir Study of the Interaction Between 1‐Dimethylamino‐2‐Propanone and Phenols
Authors: Parmentier J. , Zeegers‐Huyskens TH. 
Published: September 2010

AbstractThe hydrogen bonds between 1‐dimethylamino‐2‐propanone and phenols are investigated by FT‐IR spectroscopy. The thermodynamic parameters are determined in carbontetra‐chloride and in 1,2‐dichloroethane. The infrared spectra show that the oxygen and nitrogen atoms are involved in hydrogen bond formation. The occupation of the two sites depends on the solvent and the difference is discussed in terms of different conformational equilibria.
Mecanisme De Decarbonylation De Pyrazolides Ionises Par Impact Electronique
Authors: Flammang Robert , Abdelouahab Fouad Bachir Ben , Munkengeshayi Kadiebwe , Boulanger Pierre 
Published: September 2010

AbstractElectron impact ionization of 1‐acryloylpyrazole [1] induces a unimolecular loss of CO forming ionized 1‐vinylpyrazole [2] as shown by metastable ion characteristics and neutralization‐reionization data. This CO loss implies a rate‐determining isomerization process into a pyrazolylmethyl ketene structure 1a+. These ketene ions have been synthetized in the ion source by dissociative ionization of pyrazolylpropionylpyrazoles. Flash‐vacuum pyrolysis of these compounds also affords the expected neutral ketenes in the gas phase, which are however readily converted into the acryloyl isomers by an intramolecular nucleophilic process.
Structure Du Principal Saponoside De Alternanthera sessilis
Authors: Penders André , Kapundu Mpuza , Delaude Clément 
Published: September 2010

AbstractSaponin from leaves of Alternanthera sessilis (L.) DC. contains a major component which has been isolated as a peracetylated and methylated derivative. Its structure has been established by NMR spectroscopy and shown to be: 3β‐O‐(β‐D‐glucopyranosyluronic acid). 28‐O‐β‐D‐glucopyranosyl oleanolic acid. Two dimensional NMR spectral data were used.
A Facile Method for the α‐Monochlorination of Aldimines and Aldehydes
Authors: De Kimpe Norbert , Coppens Wim , Krauze Aivars , De Corte Bart , Stevens Christian , Welch John 
Published: September 2010

AbstractAldimines were selectively α‐monochlorinated without any interference of α,α‐dichlorinated derivatives, by a sequence of reactions involving α‐trimethylsilylation of preformed 1‐azaenolates, α‐chlorination using N‐chlorosuccinimide and desilylation in methanol. Upon acidic hydrolysis, these α‐monochloroimines provide an easy access to α‐monochloroaldehydes.
Diethyl‐ and Di‐n‐Butyltin(IV) 3‐Amino‐4‐Methylbenzoates: Synthesis, Spectroscopic Characterization and in Vitro Antitumor Activity
Authors: Gielen Marcel , Khloufi Abdelaziz El , Biesemans Monique , Mahieu Bernard , Willem Rudolph 
Published: September 2010

AbstractDiethyl‐ and di‐n‐butyltin(IV) oxides react with 3‐amino‐4‐methylbenzoic acid in a 1:2 (a) and 1:1 (b) molar ratio to yield dialkyltin compounds of the types R2Sn[O2C‐C6H3‐3‐NH2‐4‐CH3]2 (a) and {[R2Sn(O2C‐C6H3‐3‐NH2‐4‐CH3)]2O}2 (b). The compounds obtained were characterized by 1H, 13C, 119Sn NMR and by Mössbauer spectroscopy. Compound 1a was tested in vitro against two human tumor cell lines, MCF‐7, a mammary tumor, and WiDr, a colon carcinoma.
Synthesis of Some Benzofuro Benzopyrones
Authors: Joshi S. C. , Trivedi K. N. 
Published: September 2010

Abstract7‐Hydroxy‐3‐phenyl‐[4H]‐1‐benzopyran‐4‐one 1a was condensed with 2‐bromocyclohexanone to yield the corresponding ether 2a which on alkaline hydrolysis gave tetrahydrodibenzofuran derivative 3a the pyran ring being opened up during this reaction. Compound 3a was dehydrogenated with DDQ and the benzopyrone ring was constructed on dibenzofuran nucleus with sodium and ethyl formate to provide 3‐phenyl‐[4H]‐benzofuro (3,2‐g)‐1‐benzopyran‐4‐one 5a. Compound 5a was also synthesized by first converting 3a into corresponding [4H]‐1‐benzopyran‐4‐one 6a and then subjecting it to dehydrogenation. A similar series of reactions were employed for 7‐hydroxy‐8‐methyl‐3‐phenyl‐[4H]‐1‐benzopyran‐4‐one 1b and 7‐hydroxy‐2‐methyl‐3‐phenyl‐[4H]‐1‐benzopyran‐4‐one 1c to obtain 2‐hydroxy‐1‐methyl‐3‐phenylacetyl dibenzofuran 4b and 2‐methyl‐3‐phenyl‐[4H]‐benzofuro (3,2‐g)‐1‐benzopyran‐4‐one 5c respectively.