bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reactivity of N‐1‐(2,2‐dichloroalkylidene) amides
Authors: Kimpe Norbert De , Verhé Roland , Buyck Laurent De , Dejonghe Walter , Schamp Niceas 
Published: September 2010

AbstractA general synthetic route to N‐1‐(2,2‐dichloroalkylidene) amides is described, starting from aliphatic 2,2‐dichloroaldehydes and an appropriate N‐unsubstituted amide. The adducts thus formed were converted into N‐(1,2,2‐trichloroalkyl) amides with thionylchloride and subsequently dehydrohalogenated with triethylamine. These N‐acyl α,α‐dichloroaldimines were found to be very apt to nucleophilic addition at the activated carbon‐nitrogen double bond, producing stable adducts. The configuration of the adducts in solution was determined by NMR‐spectroscopy. Treatment of the title compounds with lithium aluminium hydride in diethylether afforded 1,2‐dialkylaziridines. The reactivity of these N‐acyl α,α‐dichloroaldimines was compared with the reactivity of the N‐alkyl analogues and the corresponding oxygen analogues, i.e. α,α‐dihalogenated aldehydes.
Synthèse de dérivés de benzoxazepines. I. 5‐aryl‐2,3‐dihydrobenzo [f] 1,4‐oxazepines
Authors: Waefelaer A. D. , Pecher J. , Dubois A. , Poultier P. 
Published: September 2010

AbstractSeveral new 5‐aryl‐2,3‐dihydrobenzo [f] 1,4‐oxazepine derivatives (10) to 25) were obtained in high yields by cyclodehydration of N‐phenoxyalkylbenzamides derivatives (26 to 41).
Systèmes aromatiques à 10 électrons π dérivés de l'aza‐1 pentalene. III. Recherches dans la série du pyrazolo [3,4‐c] pyrazole
Authors: Gonzalez E. , Sarlin R. , Elguero J. 
Published: September 2010

AbstractThe annular tautomerism of 3,4‐dimethyl‐6‐phenyl‐pyrazolo [3,4‐c]pyrazole is discussed on the basis of its 13C NMR spectrum and the spectra of two of its methylated and acetylated derivatives.
Isotope selective chemical activation of ethylene by high power I.R. laser pulses
Authors: Bastiaens J. , De Keuster D. , De Hemptinne X. 
Published: September 2010

AbstractChemical processes in C2H4 irradiated with CO2‐laser pulses are investigated. In the higher pressure domain (>5 torr) a focused laser beam initiates a plasma, while C2H4 dehydrogenises to C2H2. If the beam is not focused, there is no dehydrogenation but C2H4 is capable to react with HCl. In the very low pressure domain a new chemical reaction is observed which is interpreted as being a consequence of multiple photon absorption. Isotope selectivity is investigated.
1H‐NMR spectral parameters of some 1,4‐dihydroxy‐2,3‐dialkylcyclopentanes: The configurational dependent magnitude of some 1H‐NMR spectral parameters
Authors: De Clercq P. , Samson M. 
Published: September 2010

AbstractThe configuration of some 1,4‐dihydroxy‐2,3‐dialkylcyclopentanes is assigned on the base of their 1H‐NMR spectral parameters. The interaction of the hydroxyl group with some side chains is discussed. It is shown that the magnitude of the 1H‐NMR spectral parameters of specific hydrogen atoms in some side chains is dependent on the configuration.
Cationic polar cycloaddition with ynamines, formation of a ten‐membered nitrogen ring by twofold ynamine insertion into a 3,4‐dihydroisoquinolinium salt: A dihydrobenzo(d)azecine derivative and its rearrangement to a substituted tetrahydrobenzo(g)quinoline via 1,7‐sigmatropic hydrogen shift
Authors: Fuks R. , Merenyi R. , Viehe H. G. 
Published: September 2010

AbstractThe reaction of 3,4‐dihydroisoquinolinium salt 11 with phenyl‐N,N‐dimethylaminoacetylene 12 affords the (1:2)‐adduct, the dihydrobenzo(d)azecinium salt derivative 13. The structure assignment is based on a preliminary X‐ray analysis as well as on analytical and spectral data. It is assumed that 11 forms with the ynamine a 1,4‐cationic polar system 14 which reacts with a second mole of ynamine 12 (now as polarophile) in a 42 cycloaddition to give compound 16. which rearranges to 13. Heating 13 in vacuo at 230‐265° leads to a dealkylation product having the tetrahydrobenzo(g)quinoline structure 19. Its formation can be explained by a 1,7‐hydrogen shift followed by an electrocyclisation of 17.
Contribution des Calculs Quantiques à L'Elucidation de la Structure en Solution de L'Acide Ribonucléique de Transfert par les Techniques de La RMN
Authors: Pullman B. 
Published: September 2010

AbstractLes spectres RMN de haute résolution des acides ribonucléiques de transfert (tARN) présentent dans l'eau une série de résonances comprises entre −11 et −15 p.p.m. qui sont attribués aux protons U‐N3H et G‐N1H impliqués dans les liaisons hydrogéne entre les paires de bases. Les positions des résonances sont les résultantes des valeurs “intrinsèques” caractéristiques des paires A‐U et G‐C isolées et de leur perturbation sous l'effet d'empilement due essentiellement aux courants π de bases. Les calculs quantiques de ces effets ont permis l'assignation des résonances observées aux paires de bases spécifiques et ont ainsi contribué d'une façon décisive à l'élucidation de la structure secondaire et tertiaire des tARN en solution.
Problèmes méthodologiques en chimie quantique
Authors: Berthier G. 
Published: September 2010

AbstractL'analyse des diverses difficultés qui se présentent lors de l'application des méthodes issues de la mécanique ondulatoire (comme la méthode des orbitales moléculaires) à l'étude des structures atomiques et moléculaires fait apparaître les points suivants: les problémes liés à l'évaluation des intégrales atomiques de base et à la détermination de fonctions d'onde monoélectroniques à partir de celles‐ci peuvent être considérées actuellement comme résolus, mais la détermination de fonctions d'onde totales précises reste encore délicate. Sur l'exemple de la barrière de rotation de l'éthane, on montre l'influence de tels calculs en physico‐chimie.
Les fonctions de Hartree‐Fock‐Slater Comme Base Pour des Calculs de Perturbation À un Électron Pour Molécules. II. L'Advantage de la Formulation Dipôle Vitesse‐Dipôle Longeur Pour la Polarisabilité de L'état Fondamental
Authors: Trsic M. , Laidlaw W. G. , Ziegler T. 
Published: September 2010

AbstractOn montre que pour le calcul par perturbation de la polarisabilité dipolaire électrique avec une base de fonctions Hartree‐Fock‐Slater, il est particulièrement avantageux de utiliser la formulation mixte dipǒle vitesse‐dipôle longeur. A l'origine de ce résultat est le fait que la formule mixte est moins sensible aux erreurs par manque de corrélation que les formules dipole longueur ou dipǒle vitesse pures.
Les Sulfates Basiques Mixtes de Cuivre et de Zinc
Authors: Glibert J. 
Published: September 2010

AbstractThe pure basic sulphates of copper and zinc obtained at 20°C by addition of soda to CuSO4and ZnSO4. solutions have the respective compositions Cu4(OH)6SO4(monoclinic symmetry) and 3 Zn(OH)2·ZnSO4·4 H2O (hexagonal symmetry with double layers). In mixed solutions (10 g Me++/l), the solid solution Cu4‐xZnx(OH)6SO4precipitates at the low zinc concentrations. The distribution curve shows a change of slope at 25% Zn at. (x = I). A transition zone caracterized by a continue modification of the structure and the hydration of the precipitate separates this compound from the tribasic sulphate of zinc saturated by copper (33% Cu at.). For this solid solution the substitution occurs in the hydroxide layers only. The distribution factor indicates a continue selectivity for copper in the different phases.
Chemical Studies of Marine Invertebrates. XXII. (1) Two Novel Sesquiterpenes from Soft Corals of the Genera Lemnalia and Paralemnalia (Coelenterata, Octocorallia, Alcyonacea)
Authors: Daloze D. , Braekman J. C. , Georget P. , Tursch B. 
Published: September 2010

AbstractThe structure and absolute configuration of 2‐desoxylemnacarnol (IV) and 2‐desoxy‐12‐oxolemnacarnol (V), two novel sesquiterpenes isolated from soft corals of the genera Lemnalia and Paralemnalia were established by chemical correlation with lemnacarnol [II].
Analyse Conformationnelle des Dérivés Arylacétiques et Propioniques à Activité Antiinflammatoire
Authors: Dive G. , Lapière C. L. , Leroy G. 
Published: September 2010

AbstractBy conformational analysis using the CNDO method we have attempted to outline the common molecular fragments for different arylacetic acids with anti inflammatory activity. The calculated energies for the different conformations give evidence for a conformation common to all these products.
Enethiols IX Alkylation of 2‐Mercapto‐Cinnamic Acids by Ion Pair Extraction Technique
Authors: Jensen L. , Thomsen I. , Lawesson S.‐O. 
Published: September 2010

AbstractOn Alkylation of tetrabutylammonium salts of 2‐mercapto‐cinnamic acids the corresponding S‐alkylated acids are produced. Subsequent alkylation then gives the corresponding esters.
Solution Conformation of the Antibiotic 3823A (Monensin A)‐Sodium Salt
Authors: Anteunis Marc J. O. 
Published: September 2010

AbstractExtensive double irradiation experiments allowed the almost complete unraveling and extraction of the parameters in the 1H‐nmr spectrum of Na+‐Monensin (1). From this it is concluded that the solution conformation is in its details highly similar to the crystal state of the Ag+ salt. Thus rings A and E are in a somewhat distorted chair, both rings B and D are in an envelope (with the flap at respectively C‐10 and C‐18) while ring C is in a 1514T(wist). An unusual high screening and consequently low rate of proton exchange was observed for some hydroxyl protons, especially in C6D6. The small couplings observed where OH‐protons are involved allow a further deeper insight in their spatial arrangement and in their participation as ligand and hydrogen bonding. Some differences with the solid state are noted here.
Pulse Polarographic Determination of Ytterbium in Minerals
Authors: Steeman E. , Temmerman E. , Verbeek F. 
Published: September 2010

AbstractDifferential pulse polarography was used for the quantitative determination of ytterbium(III) in minerals and oxides of other lanthanides. As the reduction occurs at fairly negative potentials and the reduction of hydrogen ions interferes at low pH the number of suitable supporting electrolytes is limited. At pH > 6 hydrolysis effects cause the reduction peak current to decrease as a function of time. Down to 5.10−‐8 M ytterbium(III) can be determined in the supporting electrolyte LiCl (0.1 – 1 M) at pH 5. The analysis of ytterbium(III) in commercial samples showed average relative standard deviations which do not exceed 7%.
Potentiometric Determination of the Thermodynamic Solubility Product of Calcium Fluoride
Authors: Verbeeck Ronald M. H. , Khan Rizwan A. , Thun Harry P. 
Published: September 2010

AbstractThe ion activity product of calcium fluoride is determined with calcium‐and fluoride selective electrodes using the cell F‐ISE/Ca2+, F−,H2O/Ca‐ISEA reproducibility of 0.01 pI units is obtained.From these measurements a thermodynamic solubility product of 10−10.45 mol3 1−3 is obtained.
Molecular Constants of Some XY4 Tetrahedral Ions
Authors: Mohan S. 
Published: September 2010

AbstractThe kinetic constants method developed in relation to tetrahedral XY4 molecules(1, 2) resulted in fresh results with respect to force constants and mean amplitudes of vibration of some molecules. Extending this procedure to eighteen ions in this paper, it is found that the kinetic constants method leads to interesting results in these oases as well. The generalized mean square amplitudes and the Bastiansen‐Morino shrinkage effects are also reported in the present investigation.
Molecular Force Field Study of Some XY5Z Type Molecules by Kinetic Constants Method
Authors: Mohan S. 
Published: September 2010

AbstractAll the quadratic potential energy constants of five XY5Z type molecules have been evaluated using Wilson's F–G matrix method, on the basis of a revised set of symmetry coordinates. The kinetic constants, the redundancy constraints and certain simplifying considerations are employed in solving the problem. The values of molecular potential constants, obtained on the basis of kinetic constants are found to be reasonable.
Solution Conformations of Dianemycin, its Sodium Salt and of Lenoremycin‐Na+ (Ro 21‐6150 or A‐130‐A)
Authors: Anteunis Marc J. O. , Rodios Nestor A. , Verhegge Georges 
Published: September 2010

AbstractExtensive nmdr experiments in the 300 MHz 1H‐nmr spectra of the title compounds in different solvents allows the conformational description of these pseudocyclic ionophores. There is a striking similarity between the present results and the solid state data for the salts. The free acid form of dianemycin possesses in solution the cyclic form wherein the cation is ultimately held in the salt. Stereoscopic views are presented (Figures 9 ‐ 11). The possible role of the sugar‐like moieties is discussed and a mechanism for trapping is tentatively proposed. Both membrane‐active complexones seem rather primitive representatives of the nigericin family, but lenoremycin offers a more sophisticated topography, the extra side‐ring possessing probably a multiple function.
Die Bildung Von 2,2,4‐Tribenzoyl‐5‐Phenyl‐ 1,3‐Oxathiol Aus Dibenzoylmethan Und Thionylchlorid
Authors: Senning Alexander 
Published: September 2010

AbstractThe reaction of dibenzoylmethane with thionyl chloride yields 2,2,4‐tribenzoyl‐5‐phenyl‐1,3‐oxathiole 3 the structure of which was rigorously proven by means of 13C NMR.
Studies on Organophosphorus Compounds XVIII. Oxidation of Tertiary Alicyclic Amines With Elemental Sulfur in Hexamethylphosphoric Triamide (HMPA). Oxidative Rearrangements of Hexahydroazepines and Octahydroazocines to Bis(3‐Pyrrolyl)Polysulfides
Authors: Perregaard J. , Scheibye S. , Meyer H. J. , Thomsen I. , Lawesson S.‐O. 
Published: September 2010

AbstractBy heating (100‐160 °C) N‐alkylsubstituted alicyclic amines, R‐N(CH2) (n = 4, 5, 6), with elemental sulfur in HMPA, oxidation of the amine ring afforded the corresponding thiolactams, 2. Thus N‐benzylthiopyrrolidone, 2a (67%), N‐(2‐phenylethyl)‐2‐thiopyrrolidone, 2b (71%), N‐benzyl‐2‐thiopiperidone, 2c (27%), N‐(2‐phenylethyl)‐2‐thiopiperidone, 2d (63%), N‐methyl‐e‐thiocaprolactame, 2e (45%), and N‐(2‐phenylethyl)‐e‐thiocaprolactame, 2f (10%) were prepared. From oxidation of N‐alkylhexahydroazepines and N‐alkyloctahydroazocines were produced as the main products bis (1‐alkyl‐2‐ethyl‐3‐pyrrolyl) polysulfides, 3, and bis (1‐alkyl‐2‐(n‐propyl)‐3‐pyrrolyl) polysulfides, 4, respectively. Reduction of these with Zn, HCl or LiAlH4 followed by methylation (MeI) gave the corresponding 3‐(methylthio)‐pyrroles, 8 in 20‐49% overall yields. 1‐(2‐Phenylethyl)‐2‐ethyl‐3‐mercaptopyrrole, 7, was isolated in 48% yield from reduction (Zn, HCl) of the corresponding dipyrrolyl polysulfide. 3, 4‐Dithiolated pyrroles were recognized in most reactions and isolated in some cases. The structures of the pyrroles were established by 1H NMR, 13C NMR, and MS.
Symétrie Moléculaire Dans La Série Des Dibenzyles
Authors: Arte E. , Feneau‐Dupont J. , van Meerssche M. , Gouverneur P. , Mulangala J. Mukinayi 
Published: September 2010

AbstractSpace group and unit cell parameters determinations on seven examples have proved that the crystalline compounds obtained in the formation of C6H5‐CRR'‐CRR'‐C6H5 derivatives from C6H5‐CHRR', are the “meso” centro‐symmetric isomers.
Redétermination De La Structure Du Diphényl‐2, 3 Butane, Forme Meso
Authors: Arte E. , Feneau‐Dupont J. , Declercq J. P. , Germain G. , van Meerssche M. 
Published: September 2010

AbstractThe interpretation of tridimensional diffraction data shows definitely that the investigated structure belongs to the meso form. The molecular centrosymmetry predicted by space group determination is not a statistical effect despite of the orientational disorder observed in the crystal.
Sur La Localisation Des Orbitales Moléculaires En Couches Ouvertes
Authors: Peeters D. , Leroy G. 
Published: September 2010

AbstractThe use of localized molecular orbitals for open shell systems is examined. Preliminary computations on carbon, nitrogen oxygen and fluorine atoms, and on the molecules of CH, NO and O2 are performed. The results obtained are described in terms of hybrids for atoms and lone pairs and bonds for molecules.
Mossbauer Spectroscopy as a Tool for the Investigation of Industrial Iron Ore Sinters
Authors: De Sitter J. , Govaert A. , De Grave E. , Chambaere D. 
Published: September 2010

AbstractMössbauer spectroscopy has been used to study the mineralogical composition of an industrial iron ore sinter. Besides a structural study of the different phases, quantitative information on the distribution of iron among the different phases is obtained.
Reactions of N‐l‐(2, 2, 2‐Trichloroethylidene)t. Butylamine With Nucleophilic Reagents
Authors: Verhé R. , De Kimpe N. , De Buyck L. , Tilley M. , Schamp N. 
Published: September 2010

AbstractReaction of N‐l‐(2, 2, 2‐trichloroethylidene) t. butylamine with sodium alkoxides and phenoxide in methanol mainly gave the corresponding dichloroimidates, while reaction with potassium cyanide afforded a dichlorocyanoenamine. The reaction mechanisms are discussed.
Determination of Rotational Temperatures in a Transitional Type Hollow Cathode Glow Discharge
Authors: Broekaert J. A. C. 
Published: September 2010

AbstractRotational temperatures were measured in a transitional type hollow cathode, operating at 60 ‐ 150 mA discharge current under 260 ‐ 1060 Pa helium or argon pressure. A method using rotational lines in the 2Σ ‐ 2Σ (0, 0) CN 3883 Å band and the 2Σ ‐ 2Σ (0, 0) N+2 3914 Å band, is described. The dependence of measured rotational temperatures (800 ‐ 1700°K) on gas pressure, discharge current and cathode temperature is discussed.
Tautomérie D'Imidazoline‐5‐Thiones
Authors: Maquestiau A. , van Haverbeke Y. , Vanovervelt J.‐C. , Lambert M. , Ravach A. 
Published: September 2010

AbstractThe tautomeric behaviour of various imidazolin‐5‐thiones is examined. In the 2,2,4‐trisubstituted series, the thiocarbonyl NH form constitutes the lone tautomer observed in all types of solvents.For the 2,4,4‐trisubstituted compounds, the predominant isomer exists in the 1‐NH form and is accompagnied in most cases by a minor percentage of the 3‐NH protomer.It seems that the composition of the prototropic equilibrium CS ⇋C‐SH in five membered heterocycles depends highly on the nature of neighbouring atoms or groups.
Le désétamage du fer‐blanc par les halogénures organiques
Authors: Mahieu B. , Delplanque P. , Apers D. 
Published: September 2010

AbstractA new route has been investigated to convert used tinplate into valuable derivatives. Detinning of tin cans by organic halides may provide attractive organometallic compounds in addition to high grade steel scrap. In this work, benzyl chloride is used as reagent in a variety of solvents.
Ring Conformational Aspects of Proline and Hydroxyproline. High Conformational Purity of Pro in DKP's and Hydantoïns.
Authors: Anteunis Marc J.O. , Callens Roland , Asher Vikram , Sleeckx Jozef 
Published: September 2010

Abstract1H‐nmr literature data for Pro and trans‐Hyp peptides (acyclic and cyclic) are reviewed and complemented with data including some new compounds (diketopiperazines and hydantoins). In both acyclic and cyclic derivatives, the hydroxy proline ring possesses a unique and highly homogenous conformation λ−or λEform) which is gradually changed into a‐form when ø‐values become for L‐residues more negative than ‐40°. Correspondingly, the Pro ring possesses more flexibility especially in the acyclic derivatives where an admixture of different forms is present. The situation becomes biased in cyclic derivatives, although the intrinsically higher mobility of the ring prevails somewhat when compared to Hyp. Also the nature of the major populations in the pseudorotational path of the five‐membered ring is somewhat more sensitive in Pro towards changes in ø. Thus, for ø ∼O° mainly a libration in theßE‐γEregion is present, while theγE form becomes the major one when ø ∼ −40° (L‐residues). For still lower values of ø the pseudorotational phase angle is displaced resulting in aαE form for ø ∼ −100° as the extreme limit. Relative shifts in the1H nmr spectra for the methylene ring protons may serve as a qualitative estimation of the buckle of DKP‐rings and therefore also for cis‐trans assignments. The shift anisotropy caused by the unique orientation of the aromatic side chain in c/D‐Phe‐L‐Pro/ corroborates the findings for the ring conformations of both the flattened DKP‐boat and of the γ−‐form of Pro.
Molecular vibrational analysis of tetramethyl compounds of fourth group elements
Authors: Kalia (Miss) Rama , Dixit Lalji , Gupta P. L. 
Published: September 2010

AbstractThe nature of molecular vibrations has been analysed for (CH3)4 M compounds, MC, Si, Ge, Sn and Pb, using recent Raman/IR data and group theoretical approach. The forms of F2‐vibrations have been discussed using the properties of L− matrices and experimental Coriolis coupling constant data. The overall force field available so far, has been critically analysed following Isotoni's criterion. The results have also been discussed in the light of kinematic coupling (T = G3 4/√det/G/), vibrational constants of tetrahedral molecules, (M‐C) bonding and compliance constants. It has been observed that for tetramethyl compounds with lighter central mass (M), any approximation method would give less satisfactory results due to excessive kinematic coupling and hence for neo‐pentane the “point‐mass model” is less valid.
1H‐NMR of pimaricin at 300 MHZ.
Authors: De Bruyn André , Anteunis Marc J. O. , Verhegge Georges 
Published: September 2010

AbstractThe1H‐nmr spectrum of pimaricin has been obtained in trideuterotrifluoroethanol at 300 MHz. Moderate resolution did not allow to extract all of the spin coupling values however. The glycoside mycosamine occurs in a4C1conformation. The oxirane moiety at C‐4′/C‐5′ is trans substituted.
1H‐NMR spectral study of chlorinated derivatives of the norbornane system. Rotameric Preference of an Endo CH2X Group.
Authors: van Bree Jan , Anteunis Marc J.O. 
Published: September 2010

AbstractThe 1H‐NMR spectra of a series of chlorinated norbornene and derived norbornanone and norbornane systems have been recorded and analysed. Several characteristics of the observed spectral parameters can be explained by considering the rotameric behaviour of the endo‐CH2X group that shows a preference for a conformation with the C‐X bond synclinal to the methine proton of the carbon it is attached to.
Rearrangement of chlorinated β‐diketone monomethyl enol ethers with sodium methoxide
Authors: Verhé Roland , De Buyck Laurent , De Kimpe Norbert , De Rooze Antoine , Schamp Niceas 
Published: September 2010

AbstractReaction of the monomethyl enol ethers of 3‐chloro‐2,4‐pentanedione and 2‐chloro‐1‐phenyl‐1,3‐butanedione with sodium methoxide in methanol gave hydroxy enol ethers, respectively 3‐hydroxy‐2,4,4‐trimethoxy‐1‐pentene and 3‐hydroxy‐2,4,4‐trimethoxy‐4‐phenyl‐1‐butene. The reaction mechanism involving the formation and opening of an oxirane predominates the Favorskii‐rearrangement.
Calcul théorique des constantes diélectriques de benzoates de 1H, 1H, perfluoroalkyle
Authors: Leroy G. , Mengoni H. , Raviart A. , Wilante C. 
Published: September 2010

AbstractIn this work, we have calculated dipole moments of a series of fluoroesters by means of the CNDO method.Onsager's relation allowed us to evaluate the corresponding dielectric constants. The correlation between experimental and theoretical results is rather good.
Conformational study on 2‐oxa‐bicyclo[3.3.0]octan‐3‐ones. configurational assignments in carbocyclic five‐membered rings by1H‐NMR.
Authors: De Bruyn André , van Audenhove Martine , Anteunis Marc J.O. 
Published: September 2010

AbstractIt has been possible to extract at 300 MHz all the1H‐nmr parameters of a series of 2‐oxabicyclo[3.3.0]octan‐3‐ones. Consideration of all the vicinal coupling constants allows to assess their conformation and shows the utility of annelation for five‐membered rings to affect the spectral pecularities in a way to give access to configurational and conformational details.