bluuebunny/crossref_metadata_2025_split huggingface dataset:
NMR Experiments on Acetals: XVIII [I]. Cis‐Trans Equilibria in Some 2,4‐Disubstituted 1,3‐Dioxolanes
Authors: Rommelaere Y. , Anteunis M. 
Published: September 2010

AbstractThermodynamic parameters for the cis‐trans equilibrium of 2, 4‐disubstituted 1, 3‐dioxolanes were evaluated using gaschromatographic data. The equilibrium is always close to 60:40 (cis:trans), and only very slightly dependent on the nature of the substituents. The t. butyl group substituted in dioxolanes has no anancomeric (biasing) effect.
Les Variables D'État en Thermodynamique
Authors: Steinchen A. 
Published: September 2010

AbstractIn the present paper, we discuss the fundamental problem of the choice of the thermodynamic variables.In the systems consisting in uniform phases, the Gibbs‐phase rule permits one to define the number of variables at equilibrium.In non uniform systems, the problem is more complicated. A multilayer model allows to describe the orientation effects in systems by means of new variables as the dipole moments.The charged and polarized double layers may be usefully treated by the local thermodynamics method. The balance equations show that an electric variable as the polarization is to be taken into account. In the layers where there is specific adsorption, the usual local variables are unnable to describe the local state of the matter. The thermodynamic quantities of each volume element of the layer are functionals of the concentrations.
Temperature Dependence of The Solubility and Complex Formation of Silver Chloride in Dimethyl Sulfoxide
Authors: Rumbaut N. A. , Peeters H. L. 
Published: September 2010

AbstractThe temperature dependence of the solubility product of AgCl in pure dimethyl sulfoxide in the range 25 to 70°C has been investigated. Thermodynamic values at zero ionic strength are estimated. Formation constants for the AgCl2− complex, existing in excess chloride are also tabulated as a function of temperature. The entropy and enthalpy data thus obtained are discussed in terms of ionic solvation.
Synthèse de Sélénoéthers Orthocarbonyles et de Benzo(b)Sélénophènes Dérivés
Authors: Christiaens L. , Renson M. 
Published: September 2010

AbstractNous décrivons une nouvelle voie d'accès au cycle benzo(b)sélénophène. Cette méthode est basée sur la réaction d'acétals halogénés avec le sélénium via les organo‐métalliques.Nous examinons ensuite diverses voies de synthèse qui ne donnent pas de résultats satisfaisants.Enfin, nous généralisons d'avantage la méthode de quaternisation décrite précédemment.
Spectrophotometric Study of N,N′‐bis(m‐Sulphobenzyl) Dithio‐Oxamide as a Reagent for Cobalt (II)
Authors: Janssens A. A. , Herman M. A. 
Published: September 2010

AbstractThe complex formed between N, N′‐bis(m‐sulphobenzyl)dithio‐oxamide and cobalt (II) can be used for the spectrophotometric determination of traces of this metal in aqueous solution.The absorbance measurements are carried out at 400 mμ in a buffered solution of pH 10. Beer's law is obeyed over the range 0,3 to 5 μg of Co per ml and the sensitivity is 0,0042 μg of Co per sq. cm., Cd2+, Cr3+, Cu2+, Hg2+, Mn2+, Ni2+, Pb2+, Pd2+, Rh3+, and Zn2+ interfere strongly.
Photochimie de Dérivés Aromatiques: III [1] Propriétés Acido‐Basiques de Dérivés Aromatiques non Substitués dans les États Électroniques Excités Singulet et Triplet
Authors: Vander Donckt E. , Lietaer D. , Nasielski J. 
Published: September 2010

AbstractThe acidity constants of protonated naphthalene, anthracene, phenanthrene, chrysene, triphenylene and 1,2,5,6‐dibenzanthracene in their lowest singlet and triplet excited states have been estimated by application of the Förster cycle to the electronic spectra of the neutral and protonated species prepared in 96% sulfuric acid or in trifluoroactic‐boron trifluoride mixtures.With the exception of 1,2,5,6‐dibenzanthracene, the basicity of these hydrocarbons is increased in the S1 state compared to the ground state. Except chrysene and 1,2,5,6‐dibenzanthracene, a similar trend is observed for the lowest triplet state although the ΔpK(T1‐So) values are smaller than the ΔpK(S1‐So) values. Solutions of naphtalene, anthracene and phenanthrene in CH3COOD were irradiated. It is shown that the positions of H/D exchange are the same for naphthalene in the ground state and in the excited state (position 1 or equivalent). Phenanthrene is photodeuterated essentially on positions 4,5, although in dark condition, deuteration occurs on positions 9, 10.
Binary Diffusion Coefficients of Lower Alkanes in Nitrogen and Argon
Authors: Jacobs T. , Peeters L. , Vermant J. 
Published: September 2010

AbstractA recently described technique for determining diffusion coefficients in binary gas mixtures was improved and the diffusion of methane, ethane, propane and n‐butane in nitrogen and argon studied.The experimental D12 values, most of which unpublished untill now, were compared with theoretical values derived from classical kinetic theory (to a first approximation), and from a more advanced treatment describing the interaction between non‐polar molecules in terms of a Lennard‐Jones potential function.
Synthèses de Ditellurures Aromatiques et de Telluroéthers Arylaliphatiques
Authors: Piette J. L. , Renson M. 
Published: September 2010

AbstractLa réaction de condensation entre les organolithiques aromatiques et le tellure commercial permet de préparer des ditellurures aromatiques (Ar‐Te‐Te‐Ar) et des telluroéthers arylaliphatiques (Ar‐Te‐C4H9) suivant que l'organolithique est préparé par réaction directe du lithium métallique ou par réaction d'interconversion au moyen du butyllithium sur un dérivé halogéné aromatique. À partir des telluroéthers du type butylique il est possible de préparer les ditellurures aromatiques correspondants par réaction de déquaternisation dans la pyridine des sels de telluronium Ar‐TeX2‐C4H9.La réduction des ditellurures aromatiques en tellurophénolates de sodium correspondants et la condensation de ces derniers avec un dérivé halogéné R‐X constituent une méthode particulièrement souple pour la préparation de substances du type Ar‐Te‐R dans lesquelles la nature du groupement R peut être choisie en fonction de la destination finale de la molécule.
Synthèses de tellurolesters
Authors: Piette J. L. , Renson M. 
Published: September 2010

AbstractNous décrivons une méthode de préparation des tellurolbenzoates d'aryle et des tellurolbenzoates d'alcoyle différemment substitués en vue d'étudier en spectrographie infrarouge la position du carbonyle de ce groupement fonctionnel. La synthèse mentionnée est basée sur la condensation de tellurophénolates soit avec des chlorures d'acides aromatiques soit avec des anhydrides d'acides aliphatiques. La transposition du principe de la méthode à des telluroalcoolates n'a pu être réalisée avec succès.
Determination of the Dissociation Constant of Monothiooxamide and Some of its Derivatives
Authors: van de Cappelle G. L. , Herman M. A. , Eeckhaut Z. 
Published: September 2010

AbstractThe dissociation constant of monothiooxamide and four of its derivatives has been determined by a spectrophotometric method at various wavelengths and ionic strengths. Values of the thermodynamic dissociation constant were obtained by graphical extrapolation and by the Debye‐Hückel equation.
The Stereochemical Requirements for Long Range Coupling Between Protons in α‐Halocyclohexanones
Authors: Jefford C. W. , Waegell B. 
Published: September 2010

AbstractThe pitfalls of assigning a stereospecific arrangement to protons coupled through four sigma bonds have been assessed for some α‐bromocyclohexanones, in particular, 2‐bromo‐3,3,5,5‐tetramethylcyclohexanone. Despite apparent exceptions, it is seen that the arrangement of four sigma bonds, which satisfactorily accounts for the observed couplings, is that of a W.
Étude de Complexes Accepteur‐Donneur par Spectrométrie Infrarouge: II. Influence de la Nature du Solvant sur les Complexes Formés Entre L'Acétophénone et SbCl3
Authors: Lecl Nedden G. Ère‐Zur , Duyckaerts G. 
Published: September 2010

AbstractInfrared intensity measurements of the free CO band have been used to investigate the complex formation between antimony trichloride and a cetophenone in various solvents. The dissociation constants of the acceptor‐donor complexes with a 1:1 stoichiometry are compared with different parameters of the solvents.
NMR Experiments on Acetals: XXIX. The Ease of Acetonide Formation of Some Glycols
Authors: Anteunis M. , Rommelaere Y. 
Published: September 2010

AbstractThe ease of acetonide formation for some 1,2‐ and 1,3‐glycols is measured and in the discussion of the equilibrium data (tables I and II), obtained by quantitative evaluation as a function of temperature, emphasis is placed upon the pronounced entropy decrease, and its consequence in the interpretation. All cyclizations are found to be favoured by enthalpy decreases but are governed by entropy changes.
Chlorination of Olefins in Dimethylformamide with Intermediate Formation of Immonium Chlorides
Authors: de Roocker A. , de Radzitzky P. 
Published: September 2010

AbstractWell defined intermediate immonium chlorides were isolated during the chlorination of olefines in N, N‐dimethylformamide. These immonium chlorides of general formula (CH3)2 [X‐CH(CHYCl)‐O‐CH=] N+.Cl− react to 1,2‐dichloroalkane derivatives by thermal decomposition, to l‐chloro‐2‐alkyl formate deriatives by hydrolysis and to chlorohydrins by alcoholysis.The 1‐chloro‐2‐alkyl formate derivatives are easily transformed into epoxy compounds.The chlorination of styrene into 1,2‐dichloro‐l‐phenylethane gives a higher yield and a better selectivity in N, N‐dimethylformamide than in other solvents.When bromine is used instead of chlorine, corresponding intermediate immonium bromides can also be isolated but with lower yields.
Contribution à L'Étude Stéréochimique de la Décomposition des Pyrazolines‐1
Authors: Bourmanne J. C. , Deleux J. P. , Leroy G. , Weiler J. 
Published: September 2010

AbstractOn décrit la synthèse et la décomposition de pyrazolines‐1 obtenues par addition de diazoalcanes sur les isomères cis et trans de l'acide p‐nitro α‐phénylcinnamique et de l'α,α′‐dicyanostilbène.On constate que les facteurs stéréochimiques (configuration et conformation) influencent considérablement le schéma de décomposition des pyrazolines‐1 considérées dans ce travail.
The Vibrational Spectra of Difluorophenylphosphine
Authors: Green J. H. S. , Harrison D. J. , Lauwers H. A. 
Published: September 2010

AbstractThe infrared (3650‐50 cm−1) and Raman spectra of difluorophenylphosphine are reported and interpreted, and the fundamental frequencies are correlated with those proposed for phenylphosphine, dichloro‐ and dibromophenylphosphine.
Méthode Nouvelle et Générale de Synthèse des Cycles Benzo(b) Thiophène et Benzo(b) Sélénophene
Authors: Ruwet A. , Renson M. 
Published: September 2010

AbstractBromine addition to o‐methylselenocinnamic acid, followed by pyridine action, leads to the heterocyclic compound: benzo(b) selenophene 2‐carboxylic acid. This new way is a very general one. Every styrene, when having selenoether in ortho position and H, COOH, or COOAlk in β, reacts in the same conditions to give benzo(b) selenophene and derivatives with good yields. Benzo(b) thiophene and derivatives are also easily available by this procedure when using sulfuryl chloride instead of bromine. The reaction is discussed.
Action de Dérivés Maloniques sur les Thio et Sélénophénols
Authors: Ruwet A. , Pourveur A. , Renson M. 
Published: September 2010

AbstractMalonic esters and other derivatives, with thio or selenophenol in polyphosphoric acid, lead to unexpected Simonis reaction. Instead of 4‐hydroxy 1‐thio or 1‐selenocoumarines they give 2‐phenylthio‐1‐thio chromones or 2‐phenylseleno 1‐seleno chromones. Several intermediates are considered. The most probable one seems to be an acrylic compound formed via the thiophenyl or selenophenyl ethyl malonate (or malonic acid). «Mixed» chromones are indeed obtained from these thiolesters or thiolacids and selenophenols and reciprocally.
Tautomérie Dans la Série des Pyrazolinones: I. Influence du Solvant Sur L'Équilibre Prototropique de la 1,3‐Diméthylpyrazoline‐5‐one
Authors: Maquestiau A. , van Haverbeke Y. , Jacquerye R. 
Published: September 2010

AbstractThe tautomerism between CH, NH and OH forms of 1,3‐dimethylpyrazoline‐5‐one has been investigated by use of I.R., N.M.R. and U.V. spectroscopy. In non polar solvents only the CH form is observed. In aprotic solvents, a linear relationship is obtained between the percent of the CH form and the basicity of the solvents, the decrease of CH form being in favor of the OH structure.In protic solvents it is difficult to discern the effect of acidity and dielectric constant in the appearance of the NH form.
The Isomeric Sulfo‐2‐Methylbenzothiazoles and their Use in the Synthesis of Sensitising Polymethine Dyes
Authors: Libeer J. , Depoorter H. , Nys J. 
Published: September 2010

AbstractLes 4‐, 5‐, 6‐ et 7‐amino‐2‐méthylbenzothiazoles (1) furent transformés en sulfo‐chlorures correspondants 2. Par hydrolyse ceux‐ci fournissent les acides sulfoniques 3 et par ammonolyse les sulfonamides 4 (Schéma I). Un mode de préparation du 2‐méthyl‐7‐nitrobenzothiazole ne laissant plus aucun doute quant à la structure du produit obtenu fut élaboré (Schéma VI). Enfin, les auteurs décrivent la synthése de colorants polyméthiniques en partant des bases mentionnées et de plusieurs de leurs dérivés et étudient l'effet des substituants sur les propriétés optiques.
Kinetics of the Oxidation of n‐Butyl Alcohol with Aqueous Bromine
Authors: Kudesia V. P. 
Published: September 2010

AbstractA kinetic study of the oxidation of n‐butyl alcohol with aq. bromine has been made. The order of reaction with respect to molecular bromine, n‐butyl alcohol and [H+] ion is found to be first, first and half at all hydrogen ion concentrations. The various activation parameters have been determined between 25° to 55°C. Effect of salts on the oxidation rates have been studied. A possible mechanism involving a rate determining proton transfer is suggested.
Stability of Alkaline‐Earth Citrate Complexes
Authors: Rumbaut N. A. 
Published: September 2010

AbstractThe stability constants of the Ca, Sr and Ba complexes with citrate ion have been determined as a function of the temperature, in the presence of 0.2 M NH4Cl. There is also evidence for 1: 2 complexes, the constants of which are reported. The stability constants for the Sr and Ba monocomplexes show a minimum at 30°C. Above this temperature, there exists a linear relationship between the enthalpy and the entropy of complex formation, the isokinetic temperature being 104°C.
Structure Cristalline de Dérives D'Acides Aminés: III. LiBr. Glylcyglycine et CaCl2. 2 Glycylclycine
Authors: Meulemans Réginald , Piret Paul , van Meerssche Maurice 
Published: September 2010

AbstractThe crystal structures of LiBr. glycylglycine and CaCl2. 2glycylglycine have been determined by X‐ray diffraction. Unit cells are triclinic P1, with a = 5.068, b = 7.620, c = 10.380 Å, a = 101.48°, β = 88.99°, γ = 95.10° for LiBr. GG (Z = 2) and a = 7.216, b = 11.325, c = 4.487 Å, α = 90.05°, β = 103.96°, γ = 97.25° for CaCl2. 2GG (Z = 1).Atomic positions, bond lengths and coordinations are given.
Effect of Thiocompounds on the Electrodeposition of Copper
Authors: Lahousse G. , Heerman L. 
Published: September 2010

AbstractThe effect of different thiocompounds in the concentration range 4.10–7–2,5.10–4 M on the electrodeposition of copper from 0,63 M CuSO4/2,04 M H2SO4 solution at 50°C was investigated.Almost no influence was observed with thiazol. Thiourea, N,N'diethylthiourea, cystine and methionine strongly influence the current/overvoltage characteristics and the structure and surface roughness of copper electrodeposits. With these compounds a depolarisation was found at low concentrations while at higher concentrations an increase of the overvoltage is observed. Addition of thiocompounds decreases the surface roughness of deposits obtained at 50 mA/cm2 with respect to those deposited from the pure solution and generally results in a grain size refinement of the crystallites. Results are discussed in terms of the strong interaction of the thiocompounds with the electrode.It is proposed that at low concentrations thiourea and N,N'‐diethylthiourea are desulfurated in preferred sites on the surface while at higher concentrations more uniform adsorption over the whole surface is predominant.
Determination of Nitrate Ion in Marine Biotopes with High Nitrate Content by Ultraviolet Spectrophotometry
Authors: Mertens J. , Massart D. L. 
Published: September 2010

AbstractA simple and rapid method for the determination of nitrate in seawater of high nitrate content (> 1 ppm) is proposed.The absorption of the nitrate ion is measured at 210 and 220 mμ. The sample is treated with a measured quantity of hydrochloric acid to eliminate the carbonate and bicarbonate interferences and measured against a nitrate free blank prepared by reduction of the nitrate to ammonia with Raney nickel. The addition of HCl permits also storage of the sample without special precautions and the use of the blank eliminates the most serious of the interferences (bromide) expected in sea‐water. The interference of organic matter limits however the applicability of the method to concentrations higher than 1 ppm.
Organometallic Compounds: 26. Halogen cleavage of group IV B Hexaalkyldimetals: A Kinetic Study
Authors: Gielen M. , Nasielski J. , Vandendunghen G. 
Published: September 2010

AbstractIodine cleavage of the metal‐metal bond in hexasubstituted dimetals of the fourth group has been studied kinetically. The reactivities of disiliciums, digermaniums, ditins and mixed dimetals are discussed in function of the substituents and of the metals involved in the metal‐metal bond.
Organometallic Compounds: 28 NMR and mass spectra of benzyltin derivatives
Authors: Gielen M. , Barthels M. R. , de Clercq M. , Nasielski J. 
Published: September 2010

AbstractThe J(Sn‐CH2) coupling constants in a series of benzyltin derivatives are examined as a function of the substituents. A J vs Σσ* graph shows three equidistant and parallel lines.The mass spectra of these compounds confirm the fragmentation rules described before.
Essais De Chloration Dirigée: XVI. Effet Mésomère et Réactivité Dans Les Réactions De Chloration Radicalaire
Authors: Soumillion Ph. J. , Gouverneur P. , Burton T. , Bruylants A. 
Published: September 2010

AbstractFrom their results concerning mainly radical chlorinations of substituted alkanes and from other literature data dealing with this subject, the authors discuss about mesomeric effects of substituents in relation with medium and reactants modifications.With the aid of a properly modified structure‐reactivity correlation, it can be demonstrated that changes in reactivity of chlorinating agents or in structure of aliphatic substrates result in quantitative variation in the importance of mesomeric effects of substituents.
Organophosphorus Chemistry. Part II. The Electric Dipole Moments of Some Tertiary Arylphosphines
Authors: de Ketelaere R. F. , Claeys E. G. , van der Kelen G. P. 
Published: September 2010

AbstractThe dipole moments of a series of tertiary arylphosphines were measured: R3P, R2PC6H5, RP(C6H5)2 (R = 4‐FC6H4, 4‐ClC6H4, 3‐FC6H4, 3‐ClC6H4), 2‐ClC6H4P(C6H5)2, 3‐FC6H4P(4‐FC6H4)2 and 4‐FC6H4P(3‐FC6H4)2.The preparation of these phosphines, some of which are reported for the first time, is briefly outlined. The identity and the purity of these substances were certified by molecular weight measurements and for some by C–H analysis.
Évaluation des Potentiels D'Ionisation et des Grandeurs Connexes au Moyen Du modèle de L'Électron Libre (F.E.M.). II. Dérivés Substitués des Hydrocarbures Conjugués et Hétérocycles Correspondants
Authors: Puttemans J. P. 
Published: September 2010

AbstractNous utilisons dans le cadre du modèle de l'électron libre, à la fois une méthode de perturbation limitée au premier ordre, un modèle inductif et le théorème de Koopmans. Nous évaluons les potentiels d'ionisation et les grandeurs connexes des dérivés substitués des oléfines conjuguées, des hydrocarbures aromatiques et des hétérocycles correspondants. Nous comparons principalement les résultats du calcul et les valeurs expérimentales dans la série du benzène.
Radiolyse a 77°K de Verres Composés de Cyclopentane et de Diméthyl‐2,3‐Butane
Authors: Tilquin B. , Claes P. 
Published: September 2010

AbstractDes mélanges vitreux de cyclopentane et de diméthyl‐2,3‐butane ont été irradiés aux rayons gamma à 77°K, à des doses de 2,06 à 2,08 Mrads.Les rendements des principaux produits de la radiolyse ont été déterminés en fonction de la composition du mélange.Le rendement en pentène‐1 est insensible à la présence d'oxygène et varie linéairement en fonction de la fraction électronique du cyclopentane. Les rendements de tous les autres produits de radiolyse étudiés sont réduits de 40 à 60% en présence d'oxygène et se caractérisent par une dépendance plus complexe vis‐à‐vis de la composition du mélange.Cette dépendance peut être expliquée par un transfert de l'activation chimique du diméthyl‐2,3‐butane vers le cyclopentane. Aux faibles concentrations en diméthyl‐2,3‐butane, le sens du transfert serait inversé.
Propriétés et Caractéristiques Des Complexes de Chélation Formes Entre les Lanthanides Trivalents et L'Acide Hydroxyéthyléthylénediaminetriacetique
Authors: Merciny E. , Duyckaerts G. 
Published: September 2010

AbstractDifferent properties of the complexes Me Y formed between the trivalent lanthanides and HEDTA have been studied: the solubilities at 20°C and 100°C, the degree of hydration and the temperature of dehydration.Extremely high solubility of certain complexes and other unexpected properties at high temperature are interpreted by the formation of aggregates in concentrated aqueous solutions.
Activités Catalytiques Simultanées D'Un Porteur D'Oxygène Dans L'époxydation Directe
Authors: Rouchaud J. , Mawaka J. 
Published: September 2010

AbstractPropylene dissolved in benzene has been oxidised by molecular oxygen at 150°C under a total pressure of 45 atm. The oxidation is eventually catalised by a soluble chelate of the MoO2+2 cation. The relationships existing between the selectivity in epoxypropane, the conversion of propylene and the concentration of the catalyst show that the chelate has a double catalytic activity: 1° it carries and activates molecular oxygen; the oxygenated catalyst epoxidises selectively the olefinic bond. 2° It catalises the consecutive oxidation of the produced epoxypropane. The relative intensities of the two simultaneous catalysis are measured for the different experimental conditions.
On the Hydroxyl Group—PMR Signals in 2‐ and 4‐Acylresorcinols and the Structure of Humulone
Authors: De Keukeleire D. , Vanheertum R. , Verzele M. 
Published: September 2010

AbstractAt room temperature the intramolecular hydrogen bridge in 2‐acyl resorcinols flip‐flops rapidly back and forth between the two possible positions. N.M.R. experiments prove that this is a “coalesced state “which can be “frozen out”.
Alternant Molecular Orbitals In Butadiene
Authors: LASKOWSKI B. , VAN Leuven P. 
Published: September 2010

AbstractThe ground state energy of butadiene is studied by means of the alternant molecular orbital method. Two possible ways for coupling molecular orbitals to form alternant molecular orbitals are investigated. It is found that when the molecular orbitals are taken from a SCF calculation the traditional coupling scheme gives lowest energy. Another choice of molecular orbitals is presented for which the alternative pairing scheme yields the lowest energy.