bluuebunny/crossref_metadata_2025 huggingface dataset:
Representation of a chemical system of interacting species: Ions and biomolecules in solution, as an example
Authors: Clementi Enrico , Montedison Soc.
Published: September 2010

A realistic representation of an ensemble of interacting molecules (or atoms, or ions) requires a description that includes the following parameters: the electronic energy, E, the electronic density, ρ, the temperature, T, the free energy, ΔG, and the entropy, ΔS. It is, therefore, necessary to consider as minimal requirement both quantum chemistry and statistical thermodynamics.

In this work we describe how to operationally link the two fields, traditionally somewhat disconnected. An application of the method is given considering the problem of water molecules arranged around a molecule of water, ion‐pairs, single ions, amino acids, bases of DNA and other biomolecules. The importance to obtain simple transferable interaction potential, and a methodology to obtain such potentials is discussed. An energy partitioning technique is presented in order to obtain pair‐potentials from ab‐initio computations. The technique allows to propose a quantum chemical definition of atoms and molecules.
Le Mythe des Orbitales Moléculaires
Authors: Julg A.
Published: September 2010

Nées d'une approximation mathématique, totalement indéterminées, non invariantes dans une transformation unitaire qui laisse altérée la fonction d'onde totale, les orbitales moléculaires apparaissent comme des êtres abstraits sans réalité physique. Toutefois les propriétés particulières des orbitales naturelles parfaitement déterminées, pratiquement confondues d'ailleurs avec les orbitales canoniques, suggèrent l'existence d'un phénomène sous‐jacent relatif à la dynamique des électrons.
Aspects of the quantum theory of chemical reactions
Authors: Re Giuseppe Del , Lami Alessandro
Published: September 2010

The existing hierarchy of quantum theoretical models for the study of chemical reactions is briefly illustrated by a reformulation of certain key concepts connected with them: charges and perturbabilities, reaction paths, reaction probabilities and residence times in chemisorption. It is suggested that systematic use of the whole spectrum of models will lead to major advances in the theoretical study of reactions having a direct technological interest.
Étude Theorique Ab‐Initio de la Décomposition Thermique des 1‐Pyrazolines
Authors: Jean Y. , Hiberty P. C.
Published: September 2010

La décomposition thermique des 1‐pyrazolines a été étudiée à l'aide de calculs SCF ab‐initio, suivis d'une interaction de configuration 3x3, en bases minimales et étendue. Trois trajets réactionnels limites ont été étudiés. Les deux premiers impliquent la rupture simultanée des deux liaisons C‐N, et la formation d'un diradical triméthylène plan, ou “face à face”. Dans le troisième trajet, les deux liaisons sont rompues successivement et l'on forme un intermédiaire diradicalaire contenant l'azote. Les énergies d'activation calculées sont respectivement 44.1, 47.8 et 44.5 kcal/mole. Les deux mécanismes les moins énergétiques sont précisément ceux qui avaient été proposés par les expérimentateurs pour rationaliser l'inversion de stéréochimie observée lors de la décomposition des pyrazolines mono‐et bicycliques.
Interaction de Configuration Perturbative en Base D'Orbitales Localisées dans le Cadre des Approximations Indo
Authors: Douady J. , Ellinger Y. , Subra R.
Published: September 2010

Un nouveau développement de la méthode PCILO est présenté dans le cadre des approximations INDO. Le nombre de configurations prises en compte est considérablement augmenté par rapport à la version CNDO originale. L'énergie de corrélation des doublets libres est incluse dans le traitement. Les barrières d'inversion calculées sont correctes et les géométries obtenues sont en bon accord avec l'expérience. Les qualités de rapidité de la méthode et la facilité d'interprétation des résultats ont été conservées. Cet algorithme ouvre la voie au traitement des phénoménes faisant intervenir les échanges σ‐π.
Note sur L'Influence des Substituants Dans le Mécanisme de la Réaction Diels‐Alder
Authors: Oliva A. , Bertrán J. , Fernández‐Alonso J. I.
Published: September 2010

Nous avons étudié l'hypersurface de potentiel de la réaction butadiène +éthylène et de quelques réactions avec un groupe donneur sur le butadiène et un groupe accepteur sur l'éthylène. Nous avons constaté que la présence de ces substituants augmente beaucoup l'asymétrie du procès tout en abaissant la barrière de potentiel de la réaction.
Analyse de la Fonction Hartree‐Fock Semi‐Projetée. Problème des Solutions Multiples
Authors: Smeyers Yves Gabriel , Delgado‐Barrio Gerardo
Published: September 2010

On interprète l'ensemble des solutions doubles, qui ont été trouvées dans le modèle Hartree‐Fock semi‐projeté (HPHF), à différentes distances inter nucléaires pour l'état fondamental de la molécule de LiH. Dans ce but, on a re cours à l'analyse des solutions en équivalents configurationnels ainsi qu'à l'étude de la stabilité des solutions HPHF. On trouve que ces solutions peuvent se classer en deux types, qui correspondent à des descriptions physiques différentes et sont, du point de vue variationnel, des minima locaux. Cette classification ne répond pas au critère énergétique. La supériorité d'une solution sur l'autre dépend essentiellement des propriétés que l'on souhaiterait calculer ainsi que la distance internucléaire.
Some Molecular Constants of Group V Hydrides
Authors: Thirugnanasambandam P. , Gnanasekaran S.
Published: September 2010

The Coriolis coupling constants and the centrifugal distortion constants relating to the hydrides and their isotopic analogues of Group V elements have been studied with the help of kinetic constants. The values of these molecular constants are in good agreement with the observed values, showing the significance of the procedure adopted in the present study.
Activated Carbon as a Preconcentration Substrate for X‐ray Analysis of Water
Authors: Vanderborght B. , Verbeeck J. , van Grieken R.
Published: September 2010

Chelation by 8‐hydroxyquinoline and subsequent adsorption on activated carbon allows quantitative enrichment for over 40 trace metals from aqueous solutions, with a 5‐10% precision and no influence of abundant alkali or alkaline earth ions. Collection of the activated carbon by filtration results in suitable samples for X‐ray fluorescence analysis.
Réformulation du modèle à délocalisation, application à la réactivité chimique
Authors: Chalvet O. , Constanciel R. , Décoret C. , Royer J.
Published: September 2010

A new formulation is presented for the delocalisation model in which the effects of environment are considered in an explicit manner. The method permits one to find the successive inversions for the selectivity of reactional sites for the 1‐methyl‐quinoleinium ions and for toluene as a function of Mullikens electronegativity, and depending only on the nature of the reactants which are engaged.
Étude de la Synthèse et de la Structure de 2‐Aryl‐4‐Méthyl‐ et ‐4‐Phényloxazoline‐5‐Ones
Authors: Maquestiau A. , van Haverbeke Y. , Vanden Eynde J. J. , Crunelle G.
Published: September 2010

The dimerisation of 2‐aryl‐4‐methyloxazolin‐5‐ones is observed as main reaction when the synthesis occurs in pure acetic anhydride. The cyclisation of a few phenylbenzoylaminoacetic acids leads to the formation of separable tautomers. The equilibrium oxazolin‐5‐one ⇆ oxazolium‐5‐oxide is highly dependent on the substituent at position 2.
Condensation D'Aldéhydes ou de Cétones Aromatiques et de Pyrazoline‐5‐Thiones
Authors: Maquestiau A. , van Haverbeke Y. , Vanovervelt J. C.
Published: September 2010

The reactions of pyrazolin‐5‐thiones and benzaldehyde (or derivatives) lead to unstable 4‐arylidenic compounds, which undergo intermolecular cyclizations. Reactions of the pyrazolin‐5‐thiones with cinnamaldehyde and acetophenone respectively affords unstable cinnamylidenic and arylidenic products, which undergo intramolecular cyclizations.

The structures of the new heterocyclic systems so obtained are established by 1H‐ and 13C NMR techniques.
Étude Aux Rayons X de la Stéréoisomèrie de Pyrazoline‐ et Isoxazoline‐5‐Ones
Authors: van Meerssche M. , Verdoncq B. , Germain G. , Declercq J. P.
Published: September 2010

X‐ray diffraction has been applied to the structure determination of (A) 3‐phenyl‐4, 1′‐isopropylthiomethyleneisoxazoline‐5‐one and (B) 1,3‐diphenyl‐4,1′‐tertiobutylthiomethylenepyrazoline‐5‐one. Both crystals are racemic. In (A), the asymetric unit contains two different diastereoisomers of the exo Z form. In the crystals of (B) both stereoisomers, exo Z (83 Z), and exo E (17 %), coexists in a disordered structure.
Influence De L'exposant De Slater Sur La Stabilité De Structures Simples De L'oxyde De Magnesium
Authors: André J. M. , Vercauteren D. P. , De Montgolfier Ph.
Published: September 2010

Within the framework of the SCF model using a minimal basis set one examines the influence of varying the Slater exponents on simple systems used to similate a magnesium oxide surface.
The Use of First Order NMR Spectra in Determining the Permutational Character of Intramolecular Rearrangements
Authors: Brocas J. , Buschen J. , Decoster A. M. , Fastenakel D. , Willem R.
Published: September 2010

We present some properties of NMR first order spectra in relation with the permutational character of intramolecular rearrangements. We use the symmetry properties of the effective spin hamiltonian in order to analyse the Kubo‐Sack exchange matrices. In this context, we propose the experimental study of two molecules and we show that this study could give rise to new information about the permutational character of the rearrangements responsible for their non‐rigidity.
Alkylation, Protonation and Bromination of Ynamines
Authors: Fuks R. , Viehe H. G.
Published: September 2010

When ynamines 1 react with electrophiles R⊕; X ⊕, the structure of the products depends strongly on the nature of the electrophilic reagent and of the ynamine. The protonation under various conditions leads only to the cyclobutenylcyanine (D) whereas the methylation and the bromination give either (D) and/or the allenamidinium salt (F). Steric factors in the presumed intermediate enaminoketenimium salt (C) appear to decide on the course of the reaction. The keteniminium, existing in equilibrium with its α‐haloenamine tautomeric form (A ⇌ B), is most probably the initial adduct of 1 and RX.
Étude Theorique Des Liaisons Intermoléculaires Par “Transfert De Charge” V. Les Complexes NH3…Cl2, H2O…Cl2 et HF…Cl2
Authors: La Grange Joëlle , Leroy Georges , Louterman‐Leloup Geneviève
Published: September 2010

An ab initio study of the intermolecular complexes NH3…Cl2, H2O…Cl2 and HF…Cl2 has been carried out with a split valence basis set 4–31G using the computer program GAUSSIAN‐70. One finds that the geometry of the complexes may be related to the position of the minimum of the electrostatic potential of the “donor” and that the polarization of the chlorine molecules is important toward the charge transfer.
Correlation of Hammett Parameters (σ σ+) With 1H‐NMRand 13C‐NMR of Some 4‐Aryl‐1, 4‐Dihydropyridines (Hantzsch‐Esters)
Authors: Dommisse R. A. , Lepoivre J. A. , Alderweireldt F. C.
Published: September 2010

1H‐NMR and 13C‐NMR spectral data of 4‐aryl‐3, 5‐diethoxycarbonyl‐2, 6‐dimethyl‐1,4‐dihydropyridines (Hantzsch‐esters) are given. The chemical shift variations resulting from the different substituents are related to Hammett σ‐ and σ+‐constants.

The 1, 4‐dihydropyridines of the Hantzsch‐ester type have been of increasing interest for studies on their spectroscopic properties and their use as model compounds for the NAD/NADH coenzyme system. Recently a study of the U.V.‐ and I.R.‐spectra of 4‐aryl‐3, 5‐diethoxycarbonyl‐2, 6‐dimethyl‐1, 4‐dihydropyridines has been published (1). Mass spectral data of the same compounds and their N‐alkylated analogs are also available (2). Although 1H‐NMR played a very important role in the determination of the exact structure of several dihydropyridine derivatives, only a small amount of systematic investigation has been done. In this paper the influence of various aryl substituents on the 1H‐NMR and 13C‐NMR chemical shift values in the dihydropyridine moiety of the above mentioned compounds is studied.
Structure Du C‐Chloro‐1,2,4‐Triazole En Phase Gazeuse
Authors: Maquestiau A. , van Haverbeke Y. , Flammang R. , Gheleyns J. P.
Published: September 2010

Mass analysed ion kinetic energy and collision induced dissociation spectra show that C‐chloro‐1, 2, 4‐triazole can be generated in three different tautomeric forms by ethylene elimination from the N‐ethyl compounds and these ions retain their structure prior to further fragmentation.

5‐ and predominantly 3‐chlorotriazole structures are responsible for the mass spectrum of the parent heterocycle.
Studies on Organophosphorus Compounds XVI On O,O‐Dialkyl Dithiophosphoric Acids and N, N, N′, N′‐Tetramethylthiophosphoric Diamide as Thiation Agents: Conversion of Carboxamides into Thiocarboxamides, Alkyl Dithiocarboxylates, or Nitriles
Authors: Perregaard J. , Thomsen I. , Lawesson S. ‐O.
Published: September 2010

By heating carboxamides with O,O‐diethyl dithiophosphoric acid, 1, at 110‐125 °C the corresponding thiocarboxamides and/or ethyl dithiocarboxylates were formed. ortho‐Substituted N, N‐dimethylbenzamides only gave the corresponding thiocarboxamides. By using O,O‐dipropyl dithiophosphoric acid and O,O‐diisopropyl dithiophosphoric acid, thiocarboxamides were also prepared, and the corresponding propyl and isopropyl dithiocarboxylates were isolated after prolonged reaction time. Reactions of sec‐ and tert‐carboxamides with N, N, N,' N′‐tetramethylthiophosphoric diamide, 2, In HMPA at elevated temperatures produced the corresponding thiocarboxamides in high yields. Primary carboxamides were converted into the corresponding nitriles after heating with 2 in HMPA. Small amounts of primary thiocarboxamides were isolated in most of these reactions. Formanilide reacted with 2 in HMPA to give N, N‐dimethyl‐N′‐phenylformamidine in 95% yield.
Complexes of Tertiary Thioamides Part II: Complexes of dimethylthioformamide with Zn(II), Cd(II) and Hg (II)
Authors: Aarts A. J. , Desseyn H. O. , Herman M. A.
Published: September 2010

The complexes of dimethylthioformamide (DMTF) with Zn(II), Cd(II) and Hg(II) are investigated by conductivity measurements and by infrared and Raman spectroscopy. Following complexes are formed: M(DMTF)2Cl2 (M=Zn, Hg), Cd2(DMTF)2Cl4, M(DMTF)2I2(M=Zn, Cd, Hg) and (M(DMTF)4)(ClO4)2 (M=Zn, Cd). DMTF coordinates through its sulphur atom. The metals appear to have tetrahedral geometry.
Investigation on the Kinetics and Mechanism of the Reaction Between Potassium Peroxodisulphate and Tartaric Acid
Authors: Agarwal S. C. , Chandra G. , Jha S. K.
Published: September 2010

The kinetics of tartaric acid oxidation by peroxodisulphate ion has been studied to elucidate the mechanism of oxidation. Uncommon to many peroxodisulphate reactions it shows a variation in order. It is found to progress bimolecularly in the beginning and unimolecularly till completion. H+ ion and O2 gas accelerate the reaction. Some observations with change of surface revealed that area/volume ratio Influences the rate of reaction. In order to explain the observed data the chain mechanism has been proposed and rate expressions have been derived to explain the change of order from two to one.
Bis Heterocycles. Part I: Synthesis of Bis(1,2,4‐Iriazoles, 1,3,4‐Thiadiazoles) and Related Compounds
Authors: Ram Vishnu Ji , Pandey H. N.
Published: September 2010

Oxalylhydrazide, on reacting with different aryl isothiocyanates yields corresponding thiosemicarbazides which serve as the key intermediate for the synthesis of 3,3′‐bis (5‐mercapto‐4‐aryl‐1,2,4‐triazoles) and 2,2′‐bis (5‐arylamino‐1, 3, 4‐thiadiazoles). The bis‐mercaptotriazoles have been transformed into corresponding sulphides by the action of suitable alkyl halides in alkaline medium. Some of the sulphides are also converted into sulphones by oxidation with acidic potassium permanganate. A coordination compound of silver with bis‐mercaptotriazole has also been prepared and characterised. Some of the compounds are screened for their pesticidal activity and significant viruscidal activity has been found.
Enamine Chemistry ‐ XVII.The Preparation of Quaternary Ammonium Salts and Their Reactions With Potassium t‐Butoxide
Authors: Kolind‐Andersen H. , Lawesson S.‐O.
Published: September 2010

Reaction of α‐bromoacrylonitrile with enamine derived from aldehydes produces cyclobutanes while enamines from ketones primarily give quaternary ammonium salts. From 1‐morpholino‐1‐cyclohexene also a cyclobutane was isolated. Reactions of the ammonium salts with bromine give the corresponding perbromides. Treatment of the ammonium salts with potassium t‐butoxide results in Stevens rearrangement reactions and Hofmann eliminations to give condensed polycyclic systems of potential synthetic value.
Formation Constants of 3d Metal Ions With N‐m‐Tolyl‐p‐Substituted Benzohydroxamic Acids
Authors: Agrawal Y. K.
Published: September 2010

The thermodynamic metal ligand stability constants of hydroxamic acids with 3 d bivalent metal ions have been determined at 25° and 35°C in different mole fraction of dioxane. The stabilities of the complexes mostly follow the order of besicities of the ligands and also the electron affinities of the metal ions as measured by their ionisation potential. The stability constants of the 3 d transition metal complexes follow the order
L'icacine, Nouvel Alcaloide Diterpenique De Icacina gussfeldtii
Authors: On'okoko Penge , Hans M. , Colau B. , Hootelé C. , Declercq J. P. , Germain G. , van Meerssche M.
Published: September 2010

Icacine, a new heptacyclic diterpene alkaloid from Icacina gussfeldtii ASCHERS has been shown to possess structure 1 by X‐ray analysis.

Some chemical and spectroscopic properties of icacine are described.
Studies on Organophosphorus Compounds XIX. About PSClx (NMe2)3‐x Compounds as Thiation Reagents
Authors: Pedersen B. S. , Lawesson S.‐O.
Published: September 2010

The thiation properties of phosphorus compounds of type PSClx‐(NMe2)3‐x (x = 0‐3) (1‐4) have been investigated by reactions with secondary and tertiary carboxamides in the temperature range 80‐150°C. Reagents 2–4 yielded in most cases the corresponding thiocarboxamides while 1 gave no products, even at elevated temperature. The reaction of 2 with carboxamides has been thoroughly investigated: Primary carboxamides gave nitriles in quantitative yields and most secondary and tertiary carboxamides yielded quite high yields of thiocarboxamides. In some cases (acetanilide, formanilide, saccharin) the reaction products were amidines or amidine salts.
Optically Active Transition Metal Complexes, LIII . Optically Active Ni‐Complexes Obtained from the Reaction of Nickelocene With Unsymmetrically Substituted Acetylenes
Authors: Brunner H. , Pieronczyk W.
Published: September 2010

Two types of products are formed in the reaction of nickelocene I with acetylenes II: green compounds III containing a bridging acetylene between two CH5H5Ni groups and red compounds IV with the acetylene added to one of the C5H5‐rings in nickelocene. The reaction was carried out for a series of unsymmetrically substituted acetylenes R‐C≡C‐R' for which the mononuclear complexes IV are chiral. The two diastereoisomers, arising from the two different ways of adding HOOC‐C≡C‐COOmenthyl to Ni (C5H5) could be separated on the basis of their different solubilities in methanol. The configurationally stable (+)‐ and (−)‐isomers differ in their 1H nmr spectra.
A Radical Post‐Scavenging Study of Irradiated Cyclic Hydrocarbons in the Solid State
Authors: Tilquin B. , Allaert J. , Claes P.
Published: September 2010

Cycloalkanes were irradiated in the solid phase at 77 K. Post‐irradiation scavenging of radicals by dissolving the irradiated cycloalkane at low temperature (100 ‐ 165 K) in a propane‐oxygen mixture lowers the dicycloalkyl and cycloalkene G values to an extent of 35‐55%. From the Δ G decrease values, we propose that the trapped radical G values be 3.1, 2.7 and 2.7 at 77 K for cyclopentyl, cyclohexyl and cycloheptyl radicals, respectively.
A Reconsideration of the Rotameric Preference of the 4‐Oniummethyl Side Chains in Fourneau's 1,3‐Dioxolane and Related Compounds in Solution
Authors: Valckx Ludo A. , Borremans Frans A. M. , Anteunis Marc J. O.
Published: September 2010

In contrast with previous proposals it is shown from the use of new 13C‐criteria that the rotor C(4)‐CH2N⊕R3 and C(4)‐CH2P⊕R3 in 2,4‐disubstituted 1,3‐dioxolanes is characterized by a clinal orientation with respect to the O(3)‐C(4) bond.

The preparation, conformation and muscarinic activity of cis−, and trans‐2‐methyl‐4‐dimethyl‐phosphinomethyl‐1, 3‐dioxolane methiodide and of cis‐, and trans‐2‐methyl‐4‐(N‐methylpyrrolid‐2‐yl)‐l, 3‐dioxolane methiodide are reported.
Tentative De Corrélation Entre Les Fréquences De Vibration Des Modes ν(So) et ν(SS) et Les Distances Interatomiques d(SO) et d(SS) Des Groupements S2O3 Coordonnés Dans Quelques Thio‐Sulfates Inorganiques
Authors: Gabelica Zélimir
Published: September 2010

The empirical relationship between sulfur‐oxygen stretching frequency and the corresponding bond length proposed by Gillepsie and Robinson(1) has been tested in the case of S2O3 ions coordinated in various inorganic thiosulfates. It is inadvisible to use the ν(SO)‐d(SO) plot for predicting d(SO) values for different thiosulfate‐to‐metal associations as the bond length change upon coordination does not lead to a sufficiently accurate deviation from the experimental error in many of the bond length determinations. Only the precise values of the symmetric and asymmetric S‐O stretching frequencies can be fairly correlated to a given thiosulfate‐to‐metal coordination. Similar conclusions have been obtained from a tentative correlation between thiosulfate sulfur‐sulfur bond lengths and stretching frequencies.
Anomalies Observées Dans Les Spectres Infrarouges De Quelques Thiosulfates Inorganiques
Authors: Gabelica Zélimir
Published: September 2010

Difficulties may be encountered in the interpretation of infrared absorption spectra of most of the inorganic thiosulfates through the use of the alkali halide pellet technique. Four typical examples including various physical and chemical interactions between the halide matrix and the salt are discussed.

For comparison the spectra were also recorded using the mull technique. Even then exchanges between the salt and the alkali halide window can occur through the simple contact with the mineral oil medium as shown in the case of the freely soluble cadmium thiosulfate dihydrate. Anomalies can be avoided by the use of inert insoluble windows in the mull technique such as Tl2BrI or polyethylene.
Solution Conformation of the Ionophore X‐206 and its Sodium Salt
Authors: Anteunis Marc J. O.
Published: September 2010

The data (TABLES I and 2) extracted from the 1H‐nmr spectra of X‐206 (1) and its sodium salt confirm the unique conformation reported for the solid state 1a and which is found to be identical in bulk Solution (Figure 7). The backbone of the antibiotic follows the seam of a tennis ball of about 14 Å in diameter thus forming a loop closed by end‐to‐tail hydrogen bond bridging. The behaviour of the hydroxylic groups is quite unique, most being orientated towards the inner cavity. At least six oxygen atoms serve as coordination sites for the trapped cation in an irregular hexagonal fashion. A central water molecule is possibly present in the free acid form that mimics the position of the cation in the salt.
Tautomérie De Pyrazoline‐5‐Thiones N1‐Substituées
Authors: Maquestiau A. , van Haverbeke Y. , Vanovervelt J.‐C.
Published: September 2010

The tautomerism of alkyl and/or arylpyrazolin‐5‐thiones, which can exist under three prototropic forms (CH, NH, SH) is examined by N. M. R., I. R. and U. V. spectroscopy.

The equilibrium takes place between the SH and NH tautomers: in neutral solvents, the SH isomer is predominant while in aprotic basic media, the ratio [NH]/[SH] depends upon, several polarity parameters.

In protic media (alcohols),the percentage of the NH form increases with the hydrogen bond donating power of the solvent.

Some substituents (acyl‐, phenylazo‐) are able to stabilize one of the tautomers via an intramolecular bond. The differences in the tautomeric behaviour between pyrazolin‐5‐ones and 5‐thiones are discussed in terms of relative polarity and stability of the carbonyl and thiocarbonyl groups.
Synthesis and Hydrolysis of 2‐(2,6‐Dichlorophenyl)‐4,6‐Dimethyl‐1,3‐Dioxane
Authors: Schacht Etienne H. , St. Pierre Tom , Desmarets Guido E. , Goethals Eric J.
Published: September 2010

The cis and trans isomers of 2‐(2,6‐dichlorophenyl)‐4,6‐dimethyl‐1,3‐dioxane were synthesized and characterized. Acid catalysed hydrolysis in dioxane/water (29/1) at 60°C demonstrated that the trans isomer hydrolizes much faster (15x) than the cis compound. The individual rate constants for the hydrolysis of both isomers were determined and discussed.
Aggregation of Methyl Orange in Aqueous Acidic Solution
Authors: De Vylder M. , De Keukeleire D.
Published: September 2010

Deviations from the Lambert‐Beer's law of concentrated aqueous acidic solutions of methyl orange are shown to be due to the formation of aggregated species. Electrostatic attraction forces are most important in the aggregation process. As it is observed that daylight may abbreviate the induction period of the reaction, it is presumed that the aggregates are formed through the intermediary of the syn isomers of the dye.
Use of Shift Reagent with MTPA Derivatives in 19F NMR Spectroscopy: Determination of Absolute Configuration of Stereomeric 2‐ and 3‐ Substituted Cyclohexanols
Authors: Merckx E. M. , Van De Wal A. J. , Lepoivre J. A. , Alderweireldt F. C.
Published: September 2010

The relative magnitude of the lanthanide induced shift (LIS) by Eu(fod)3 for the 19F NMR spectra of the CF3 group of diastereomeric (R)‐(+)‐α‐methoxy‐α‐trifluoro methylphenylacetate esters [(R)‐(+)‐MTPA esters] of stereomeric 2‐ and 3‐ substituted cyclohexanols have been measured. The [R,R] diastereomeric esters are responsible for the largest downfield LIS value in the presence of Eu(fod)3. With a well defined Eu (fod)3/ester molar ratio, the opitcal purity can also be determined.
Cyclic voltammetric study of the system Sb(III)/Sb(Hg) IN 4 M HCl
Authors: Verplaetse H. , Donche H. , Temmerman E.
Published: September 2010

The system Sb(III)/Sb(0) has been investigated in 4 M HCl by cyclic voltammetry at a sitting mercury drop electrode. It was found that specific adsorption of the reactant Sb(III) occurs. This was confirmed by droptime measurements at a dropping mercury electrode. Other deviating features of the cyclic voltammetric curves can be explained by the convergent nature of the diffusion process within a spherical mercury electrode.
Selectivity enhancement of consecutive catalytic reactions by periodic operation
Authors: Baron G. , Larsen K. , Wajc S.
Published: September 2010

It is shown that in some cases, periodic operation can significantly improve the selectivity in catalytic consecutive reactions, but that the effect of periodic operation may also be detrimental under similar conditions.
Conductivity and photoconductivity of TCNQ salts of poly (1‐butyl‐2‐vinyl‐pyridinium)/polystyrene copolymer.
Authors: Wollast P. , Noirhomme B. , Vander Donckt E.
Published: September 2010

The dark conductivity of the tetracyanoquinodimethane (TCNQ) salt of poly (1‐butyl‐2‐vinylpyridinium)/polystyrene copolymer in the presence of various amounts of neutral TCNQ has been measured using the four‐point probe technique. The activation energy to electrical conduction is obtained between +2 and +35°C. The quantum yield of carrier collection under irradiation at 360‐370 nm is 10−2. It appears that the samples examined are not suitable for light into electricity conversion: to decrease the resistivity of the films, large quantities of neutral TCNQ have to be added to the polymer which has for effect to decrease the apparent band gap of the material to values much smaller than the ideal value (1,2‐1.5 eV).
Electronic structure of dimethyl disulfide and naphthalene 1,8‐disulfide: Ab initio and E.S.C.A. results
Authors: Riga Joseph , Verbist Jacques J. , Lamotte Christian , Andre Jean‐Marie
Published: September 2010

The electronic structure of dimethyl disulfide and naphthalene 1,8‐disulfide has been investigated by means of ab initio calculations. Theoretical results are compared with high resolution ESCA valence band spectrum of solid dimethyl disulfide. Semiconducting properties are predicted for planar aromatic disulfides.
A Proposal of a mechanism for ring inversion in all‐cis‐transoid‐perhydropolycenes, including cis‐decalin and cis‐transoid‐cis‐perhydroanthracene.
Authors: De Pessemier Fritz , Anteunis Marc , Tavernier Dirk
Published: September 2010

A mechanism for ring inversion in the title compounds is discussed. Activation enthalpies are predicted to be 13.4 kcal.mole−1 for the decalin and the perhydroanthracene, and 17.4 kcal.mole−1 for the perhydropolycenes, independent of the number of annelated rings.
Kinetics of the reaction of calcium sulfite with SO2
Authors: van Houte G. , Delmon B.
Published: September 2010

The kinetics of the reaction of CaSO3 with SO2 have been investigated in the temperature range 450–640°C. The reaction corresponds to the model of uniform attack of the reactant surface. Initial rates correspond to a control by interface chemical processes; activation energy is 30 Kcal. mol; the reaction is first order with respect to SO2. Diffusion, presumably solid state diffusion through the covering sulfate layer, progressively becomes strongly rate‐limiting, but the reaction can be conducted to completion.
Electrocatalytic reduction of butanone II. kinetics of the production of butanol 2
Authors: Feyaerts K. , De Hemptinne X.
Published: September 2010

By using a square wave modulation technique, a fast reversible step is isolated ahead of the rate determining process for the reduction of butanone to butanol‐2.

By comparison with analogous results obtained previously for the reduction of acetone to propane, it is concluded that this reversible step is situated ahead of the branching between the alcane and alcohol paths.
The structure of trocheliophorol, a cembranoid diterpene from soft corals of the genus SARCOPHYTON(1).
Authors: Groweiss A. , Kashman Y. , Vanderah D. J. , Tursch B. , Cornet P. , Braekman J. C. , Daloze D.
Published: September 2010

The structure determination of trocheliophorol (1), a new cembrans diterpene isolated from two soft corals of the genus Sarcophyton, is described.
Étude Par Spectrométrie de Vibration, de L'Interaction Entre Les Halogénures de Trialkylammonium et Quelques Dérivés Phénoliques. II. Vibration vNH+
Authors: Rulinda J. B. , Zeegers‐Huyskens T. H.
Published: September 2010

The vibrational spectrum of Et3NH+ Cl− and Et3 N H+ Br− has been examined in the v NH+ range. In the solid state, the Raman spectrum shows a well‐defined doublet while the infrared band profile is very large and shows a resonance window fixed at 2510 cm−1. The same effect is observed for both salts dissolved in 1,2 dichloroethane. The formation of hydrogen bonded complexes between the anions Cl− or Br− and some phenol derivatives brings about a frequency shift of the vNH+ band toward higher wavenumbers. This shift depends on the acidity of the phenol derivative and on its concentration. For these complexes, a window also appears at 2510 cm−1; this negative absorption probably arises from a Fermi resonance with the rocking vibration of the methyl group.
Ideal Gas Thermodynamic Functions of Some Mixed Halides of Boron
Authors: Adame I. Ernesto , Vicharelli Pablo A.
Published: September 2010

The moments of inertia of 10 BF2 Br, 11 BF2 Br, 10 BFBr2, 10 BCl2Br, 11 BCl2Br, 10BClBr2, and 11 BClBr2, and 11 BClBr2 have been revised. The present values and the available vibrational data have been utilized to reevaluate the ideal gas chemical thermodynamic functions of these molecules for the temperature range 100 to 2000 K. A rigid rotor and harmonic oscillator model has been used.
Study of the Decomposition Products Formed from Trans Ferulic Acid by Treatment with Boiling Hydrochloric Acid
Authors: van Brussel W. , Tavernier D. , van Sumere C. F.
Published: September 2010

Previous experiments showed the instability of hydroxycinnamic acids (e.g. ferulic acid) in acid media. In order to study this problem, which is of great importance for the analysis of naturally occurring hydroxycinnamic acid derivatives, more thoroughly, ferulic acid was treated on a preparative scale with boiling hydrochloric acid and the decomposition products obtained were separated and identified.
On the Structure of Tricyclodehydroisohumulone
Authors: De Taeye Leo , De Keukeleire Denis , De Bruyn André , Verzele Maurice
Published: September 2010

The structure of tricyclodehydroisohumulone was investigated by 300 MHz 1H‐NMR and other spectroscopic methods. It is either 3‐(3‐methylbutanoyl)‐10‐(1‐methylethenyl)‐4,5‐dihydroxy‐9,9‐dimethyl‐tricyclo [6.3.0.01,5]undec‐3‐ene‐2,6‐dione or 3‐(3‐methylbutanoyl)‐9‐(1‐methylethenyl)‐4,5‐dihydroxy‐11,11‐dimethyl‐tricyclo[6.2.1.01,5]undec‐3‐ene‐2,6‐dione. Other criteria lead to a preference for the first structure.
Chemical Studies of Marine Invertebrates. XXXV(1). Sarcoglaucol, a Novel Cembrane Diterpene from the Soft Coral Sarcophyton Glaucum (Coelenterata, Octocorallia)(2)
Authors: Albericci M. , Braekman J. C. , Daloze D. , Tursch B. , Declercq J. P. , Germain G. , van Meerssche M.
Published: September 2010

Sarcoglaucol (1), a novel, ichtyotoxic cembrane diterpene has been isolated from the alcyonarian Sarcophyton glaucum. Its structure and relative configuration were determined by X‐ray diffraction analysis.
Determination de la Structure de la N,N‐Diethylbenzamide‐Oxime
Authors: Arte E. , Declerq J. P. , Germain G. , van Meerssche M.
Published: September 2010

The structure of the title compound has been investigated in order to determine the configuration of the oxime group. The molecules appear to be in the E configuration and are H‐bonded to form dimers in the crystal.

From partial structural informations, p‐nitrobenzamidoxim seems to adopt the Z configuration.
Steric hindrance in N‐substituted benzyl, N‐T‐butyl nitroxides
Authors: De Pauw E. , Collin J. E.
Published: September 2010

The EPR spectra of N‐substituted benzyl N‐t‐butyl nitroxides show a significant dependence of the β‐CH2 proton hyperfine coupling constants on the position and the number of phenyl substituents. This behaviour may be explained by simple steric considerations.
The reaction of ethyl 4‐bromo‐2‐ethoxycarbonyl‐2 pentenoate with some nucleophiles
Authors: Kristensen J. , Lawesson S. ‐O.
Published: September 2010

The title compound, III, has been reacted with sodium phenylthiolate and morpholine and the substitution products IV and V respectively, have been isolated. No Michael addition was observed. Potassium cyanide and NaBH4 do react with III according to Michael and subsequent ring‐closure reactions lead to the cyclopropanes VI and VII, respectively. Sodium ethoxide and III are also suggested to undergo a Michael addition, followed by a cyclization reaction and finally an opening of the ring by the ethoxide ion to give the acetal VIII.
Preparation and some reactions of N,N‐diacetylamines
Authors: Meyer H. J. , Nolde C. , Thomsen I. , Lawesson S. ‐O.
Published: September 2010

A number of N,N‐diacetylamines has been prepared in generally high yields by acetylation of primary amines with acetic anhydride in presence of magnesium and catalytic amounts of Cu(OAc)2. The general physical and also some chemical properties of N,N‐diacetylamines are presented together with pertinent spectroscopic data.
Molecular constants of Trimethyl Antimony (V) Dihalides
Authors: Namasivayam R. , Viswanathan S.
Published: September 2010

The force field study of Me3SbX2 (X=F, Cl, Br, I) molecules of D3h symmetry has been carried out by Redington's approach treating the methyl group as point masses. The force constants, mean amplitudes of vibration, bond charge and path length parameters and rotation distortion constants have also been calculated and compared with the literature values whichever is available.
Distribution of Electrolytes Over Two Liquid Phases
Authors: Joos P. , Verburgh Y.
Published: September 2010

The partition coefficients and the distribution potentials of electrolytes for distribution over two phases (water and nitrobenzene) are examined theoretically. Measurements are presented for a homologous series and compared with theoretical predictions. Also the distribution of an ionic mixture R+, P+ (cations) and X−, Y− (anions) is considered. A relation is found between the distribution potentials of the electrolytes RX and PY at one hand and of the electrolytes RY and PX at the other hand.
Étude de L'Autoassociation de Quelques α‐Hydroxyiminocétones en Solution Par Spectroscopie Infrarouge et Mesures Diĺectriques.
Authors: Bernadou J. , Fayet J. P. , Bonnafous M. , Mauret P.
Published: September 2010

Five α‐hydroxyiminocétones R‐CO‐C(NOH)‐R' have been studied in CCl4 dilute solution. Frequency and intensity variation of infrared absorption bands (C0 and 0‐H) and dielectric permittivity variation, at several concentrations, point out formation of intra or intermolecular hydrogen bonds, involving or not the CO group; this show existence of monomer (RR'camphor ring, syn isomer) and three different associations: closed dimer (RR'camphor ring, anti isomer), open polymers (RCH3, R'H) and (RR'CH3) or (RR'C6H5).
Additional Evidence for the Existence of Only One Kind of Transition State in the NABH4 Reduction of Aliphatic Ketones
Authors: Lemière G. L. , van Osselaer T. A. , Alderweireldt F. C.
Published: September 2010

Only one isokinetic relation is found for the NaBH4 reduction of aliphatic ketones. The study includes acyclic and cyclic ketones, hindered and unhindered cyclohexanones, overall reaction rates and reaction rates of axial and equatorial attack on cyclohexanones. This strongly supports the view‐point that all these reactions proceed through only one kind of transition state. For aromatic ketones other correlations are found corresponding with other types of transition state.
Synthesis and conformational features of a series of benzyl 4‐O‐(aldopentopyranosyl)‐2,3‐anhydro‐β‐D‐ribopyranosides.
Authors: De Bruyn AndrÉ , Rijsbergen Ronan Van , Anteunis Marc J. O. , Claeyssens Marc , Deleyn FranÇOis
Published: September 2010

A series of benzyl 4‐0‐(aldopentopyranosyl)‐2,3‐anhydro‐β‐D‐ribopyranosides has been synthesized. The 1H‐nmr parameters of these compounds have been obtained at 300 MHz in pyridine‐d5 solution. Chemical shift increments of pyranoid systems in pyridine solution are advanced. The conformation of the 2,3‐anhydro‐β‐D‐ribopyranoside moiety is discussed. It occurs in a nearly equi‐energetic equilibrium of the 0H5 and 5H0 forms.
Corrosion Resistance of Pre‐oxidised Al‐Cast Iron
Authors: Defrancq J. N.
Published: September 2010

The corrosion rate in oxygen at elevated temperature, as well as the corrosion rate of pre‐oxidised Al‐cast iron in different acid solutions is discussed. It is shown that pre‐oxidation at 700°C is the optimal treatment.
Raman Intensity Study of the VC=O Band of Cyclohexanone Complexed with Phenol Derivatives
Authors: Thijs C. , Zeegers‐Huyskens T. H.
Published: September 2010

The absolute Raman intensity of the VC=O band of cyclohexanone complexed with phenol derivatives increases by complex formation. The intensification factor varies between 1.16 (3,4‐diCH3 phenol) and 1.78 (3,4,5‐triCl phenol) and is proportional to the enthalpy of complex formation. The intensity enhancement cannot be explained by the variation of bond order or distance of the C=O bond but is discussed in terms of the Orville‐Thomas pulsed cloud model.
Contribution a L'Étude Théorique Des Complexes Par Liaison Hydrogène. VI. Le CH4 Comme Donneur de Proton.
Authors: Ruelle P. , Leroy G. , Louterman‐Leloup G.
Published: September 2010

Ab initio study of molecular complexes including methane as proton donor has been carried out at the 4‐31G basis set level with the GAUSSIAN‐70 computer program. The geometry optimization as well the energy decomposition analysis and the configuration interaction calculations allow us to show the presence of weak hydrogen bonds in these systems.
Cycloaddition Reactions of Tris (IMINO) Thietanes
Authors: L'abbé Gerrit , Huybrechts Lucas , Toppet Suzanne , Declercq Jean‐Paul , Germain Gabriel , Meerssche Maurice Van
Published: September 2010

Tris (imino) thietanes undergo ring transformations with electron‐rich unsaturated systems. For instance, 1a,b react with trans‐β‐dimethylamino styrene to yield tetrasubstituted pyrroles 2a,b which can be smoothly thermolyzed into trisubstituted pyrroles 3a,b and tert‐butyl isothiocyanate. With ynamines, exemplified by N‐diethylaminopropyne, 1a‐c are transformed into thiopyrans 4a‐c, and thence into thiophenes 5a‐c by elimination of tert‐butyl isonitrile. The products were identified by spectral (IR, 1H NMR, 13C NMR, mass spectra) and analytical properties as well as by X‐ray analyses.
Pd(II) Complexes with N‐Methyl Thiobenzamide
Authors: Aarts A. J. , Desseyn H. O. , Herman M. A.
Published: September 2010

Complexes of Pd(II) with N‐methylthiobenzamide (L) are investigated by infrared spectroscopy. Compounds prepared are cis‐PdL2‐X2. (X=Cl or Br), trans‐PdL2I2. and [PdL4] X2 (X=Cl, Br or ClO4). The ν(PdX) and ν(PdS) frequencies are discussed. The high trans‐effect of L is demonstrated by its influence on the structure and on the spectroscopic properties.
Substitution of Metal Ions in Anionic Surfactants by Ion‐Exchange Reactions in Non‐Aqueous Solvents
Authors: Nelen A. A. M. , Tavernier S. M. F. , Gijbels R.
Published: September 2010

The preparation of anionic surfactants with different metal counter ions has attracted some interest in recent years. Up to now basic neutralisation of the hydrogen form of the surfactant was used. A new method is described, which is based on ion‐exchange reactions accompanied by precipitation in non‐aqueous solvents such as ethanol or diethylether. The purity of the surfactants formed is better than 98% and the yield is higher than 92%.
Stereochemical Aspects of Proton Chemical Shifts. IX. Influence of O‐Alkyl Groups on the Chemical Shift of the Glycosidic Proton in Pyranoid Systems
Authors: Bruyn André de , Hosten Noël , Anteunis Marc J. O. , Claeyssens Marc , De Bruyne Clement K.
Published: September 2010

The 1H NMR parameters of some alkyl β‐D‐xylopyranosides (alkyl = Me, Et, n.Pr, i.Pr and t.Bu) have been measured in D2O and DMSO‐d6 solution at 300 and 360 MHz. A rationale is checked to explain the influence of the 0‐alkyl groups on the chemical shift of the glycosidic proton. It is found, as reported previously for other cases1, 2, that γ‐increments in full carbon‐skeleton are very similar to those in a H‐C‐O‐C‐C skeleton.
Assignment of Fundamental Vibrations of Hydrazo Derivatives. Carbohydrazide and Diprotonated Carbohydrazide
Authors: Sathyanarayana D. N. , Raja S. V. Kasmir , Savariraj G. A.
Published: September 2010

The Infrared spectra of carbohydrazide, diprotonated carbohydrazide and their deuterated compounds have been measured in the solid state. From the results on thio‐ and selenocarbohydrazides and other related molecules and normal coordinate analyses using a Urey‐Bradley force field assignments of the fundamental vibrational frequencies and a description of the normal modes of carbohydrazide, diprotonated carbohydrazide and their deuterated species are given.
Kinetics of the Reaction of CaSO3 and CaCO3 with SO2 in the Presence of CaCl2
Authors: van Houte G. , Delmon B.
Published: September 2010

We report kinetic data on the reaction of CaCO3, and CaSO3 impregnate with 2% mol. CaCl2, at various temperatures between 450 and 640° C. The rate of reaction of CaCO3, with SO2, giving CaSO3, is greatly increased in comparison with pure CaCO3. An important increase of the surface area of the reacting solid is observed in the initial stages of the reaction. The initial rates of reaction correspond to a thermal increment of 37 kcal.mol−1. Order with respect to SO2 is 1. The rate of reaction of treated CaSO3 with SO2 is drastically reduced, in comparison to pure CaSO3, Possible mechanisms of the action of CaCl2 are discussed.
Infrared Study of the Addition Compound Between Benzamide and Tintetrabromide in Solution
Authors: Cauteren‐Thevissen Mady Van , Huyskens‐Zeegers Thérèse
Published: September 2010

The stability constants K1 and K2 of the molecular adduct between benzamide and tintetrabromide in chloroform as solvent can be determined only for very dilute solutions because, as suggested by the study of the ν(C=0) and the ν(NH2) vibrations, the formation of this adduct induces the selfassociation of the amide molecule.
Structures des Phényl‐5 et Éthyl‐5 Diméthyl‐2,2 Dioxanne‐1,3 Dione‐4,6
Authors: van Coppernolle A. , Declercq J. P. , Dereppe J. M. , Germain G. , van Meerssche M.
Published: September 2010

The crystal and molecular structures of two 5‐R derivatives of the 2,2‐dimethyl‐1,3‐dioxane‐4,6‐dione with R = C6H5 or C2H5 were determined by X‐ray diffraction and compared with a previous determination of the 5‐thienyl compound. The crystal data are as follow:

R = C6H5: 2,2‐dimethyl‐5‐phenyl‐1,3‐dioxane‐4,6‐dione; C12H12O4, monoclinic, P21/n, a = 5.255(1), b = 13.786(4), c = 15.484(7) Å, β = 94.34(3)°, V = 1118.5(7)å3, Dx = 1.31 g cm−3, Z = 4.

R = C2H5: 5‐ethyl‐2,2‐dimethyl‐1, 3‐dioxane‐4,6‐dione; C8H12O4, orthorhombic, P212121, a = 5.196(1), b = 10.908(4), c = 15.925(6)Å, V = 902.7(5)A3 Dx = 1.27 g cm−3, Z = 4.

The structures have been solved by direct methods (MULTAN) and refined by least squares. In both compounds, the dioxanedione ring is in a boat conformation and the molecules exhibit non‐crystallographic mirror symmetry.
Intramolecular Exciplex Formation in α‐N‐Dialkylamino‐ω‐Arylalkanes
Authors: Vanderauweraer M. , De Schryver F. C. , Gilbert A. , Wilson S.
Published: September 2010

The temperature and solvent dependence of the photophysical behaviour of 3‐phenyl‐1‐N‐dimethyl‐aminopropane and 4‐phenyl‐1‐N‐dimethylaminobutane are investigated. The formation of a polar excited state complex is shown to be thermodynamically controlled.
Ring‐Opening Reactions of Tris(Imino)Thietanes
Authors: L'abbé Gerrit , Huybrechts Lucas , Toppet Suzanne , Declercq Jean‐Paul , Germain Gabriel , van Meerssche Maurice
Published: September 2010

Tris(imino)thietanes (1a‐c) manifest a dual reactivity in ring‐opening reactions. Methanol, diethylamine and ethanethiol all attack the thietane ring at the electrophilic C4‐atom to yield open‐chain products of type 2‐4. On the other hand, the reactions of 1a‐c with hydrazoic acid occur with cleavage of the C2‐S bond producing tetrazoles of type 6. Sodium azide and 1a reacted to furnish the unexpected product 9. Product characterization was based on spectral (IR, 1H NMR, 13C NMR, mass spectra) and analytical properties, and also, in the cases of 6b and 9, on an X‐ray diffraction analysis.
Some Aspects of Steroid Research Based on Natural Products from Plant Origin
Authors: Crabbé Pierre
Published: September 2010

A short report on the use of diosgenin as a starting material for the preparation of a number of steroids is given. The synthesis of several steroid hormones is briefly described. Historical aspects of the chemical synthesis and clinical studies of steroidal contraceptive agents are also mentioned. Some human facets of research in the steroid field are outlined.
Détermination de la Matrice des Coordonnées de Symétrie Pour un Groupement XYn Matrices U, G, F ET Σ Pour les Molécules XY6 de Symétrie D3h
Authors: Mahmoudi Saâd , Wendling Edgar
Published: September 2010

In order to compute later all the force constants and mean‐square amplitudes of the generalized valence force field, we are proposing a method for the determination of the U‐matrix for XYn groups, and the U‐, G‐, F‐ and Σ matrices (Wilson's Method) for XY6, (D3h ) molecules.