bluuebunny/crossref_metadata_2025 huggingface dataset:
On‐stream determination of ammonia in boiler feed‐water with an ammonium ion selective electrode and an ammonia probe.
Authors: Mertens John , Winkel Pierre Van Den , Massart D. L.
Published: September 2010

The development of methods for on‐stream determination of ammonia in boiler feed‐water by means of an ammonia probe and an ammonium selective membrane electrode is described. A pilot‐plant simulating a boiler feed‐water circuit was used. The two electrode systems were connected in parallel to the circuit so that their behaviour could be checked simultaneously. The accuracy and the reproducibility were very satisfactory. The response of the two electrode systems is fast enough for on‐stream measurement. They are practically free from interferences which could be present in boiler feed‐water, except the probe which is subject to interferences from volatile amines.
Studies in organic mass spectrometry. XVII The fragmentation of methyl enol ethers of 1,3‐cyclohexanediones and 1,3‐cyclopentanediones
Authors: Cant E. , Maenhaut‐Claeys M. , Francque M. , Vandewalle M.
Published: September 2010

The influence of alkyl substituents on the mass spectral behaviour of methyl enol ethers of 1,3‐cyclohexanediones and 1,3‐cyclopentanediones is studied. Six membered ring compounds behave quite straithforwardly and in accordance with the fragmentation suggested for 1,3‐cyclohexanediones in the enol form. Some fragmentations are supported by deuterium labelling.

In the case of enol ethers of 1,3‐cyclopentanediones the 4‐ or 5‐substituted isomers display identical spectra. This isomerisation is studied by metastable transitions, low energy spectra and deuterium labelling; a possible mechanism is advanced.
Degradation Thermique D'Imidazole‐N‐Oxydes dans la Source D'Un Spectrometre de Masse
Authors: Maquestiau A. , van Haverbeke Y. , Flammang R. , Chua S. O. , Cook M. J. , Katritzky A. R.
Published: September 2010

The mass spectral characteristics of the products described previously as triphenylimidazole‐N‐oxide and N‐hydroxytriphenylimidazole can be interpreted on the basis of polymorphic forms of the same tautomer ( probably the N‐oxide structure ). Intense thermal degradation is observed in the source of the mass spectrometer.
Structure Electronique des Bandes de Valence du Polyethylene et de Ses Derives Fluores
Authors: Delhalle J. , Delhalle S. , Andre J. M.
Published: September 2010

Les bandes de valence des dérivés fluorés du polyéthylène ont été calculées par la méthode de Hückel généralisée. Les modifications dues à la substitution chimique sont examinées.
Application de la Spectrométrie de Masse en Serie Hétérocyclique. Système N‐Phényl‐3,6‐Dihydro‐2H‐1,2‐Oxazine. Mise en Évidence D'Une Réaction de Substitution Intramoléculaire au Niveau des Cations Radicalaires Phényl et Pyridylbutadiényles
Authors: Maquestiau A. , van Haverbeke Y. , De Meyer C.
Published: September 2010

The mass spectra of α−γ− and β‐pyridylbutadienes contain[M‐l]+ peaks which are probably formed via an intramolecular substitution reaction leading respectively to azonianaphtalene, quinolinium and isoquinolinium ions. These structures can also be formed, by ring expansion from suitable alkylated heterocyclic systems like 2‐methylindolizine and methylindoles. Abundance ratios including metastable and normal ions are in agreement with the proposed mechanism. The same type of reaction, observed in the case of chlorophenylbutadienes is discussed.
Étude par RPE de la Structure Électronique et Moléculaire de Complexes du Cuivre(II) Dans des Zéolites de Type Y
Authors: Derouane Eric G. , Vedrine Jacques C. , Taarit Younès Ben
Published: September 2010

L'analyse du spectre RPE de complexes du cuivre(II) avec l'ammoniac et la pyridine, piégés dans des zéolites de type Y, permet d'obtenir certains renseignements sur la structure électronique et géométrique de tels complexes, à savoir le degré de covalence relatif de la liaison Cu‐N, le nombre de ligands coordinés, et leur disposition autour de l'ion central.

Une étude en fonction de la température de la constante de couplage hyperfin de l'ion Cu2+ dans ces complexes montre que celle‐ci diminue pour des températures croissantes. Ce comportement s'explique en admettant une modulation de ce couplage hyperfin par une vibration bien définie, celle des liaisons Cu‐N. Il est possible, à partir des variations observées en RPE, de déterminer pour les divers types de complexes les fréquences de vibration Cu‐N. Celles‐ci sont en accord parfait avec celles mesurées par spectroscopie IR dans l'infrarouge lointain. Ces fréquences, très sensibles à l'interaction des complexes avec leur environnement, permettent d'obtenir certaines informations sur leur localisation dans la structure zéolitique.
Contribution à L'Étude des Tellurures de Cobalt et de Nickel
Authors: De Meester P. , Naud J.
Published: September 2010

The tellurides Co1‐xTe (0.1< x<0.43) and Ni1‐xTe (0.04< x <0.42) precipitated by hydrogen telluride have a composition which is a function of the pH of the precipitation medium. This variation of composition is due to the interaction of the two redox systems Te−/Te− on one hand and H+/H2 on other hand.
Mise en Évidence D'Un Composé BiBo3 et de Son Polymorphisme par Spectroscopie Vibrationnelle
Authors: Pottier M. J.
Published: September 2010

Bismuth orthoborate BiBO3, a non‐existent compound after the Bi2O‐B2O3 phase diagram, has been obtained by melting a mixture of H3BO3 and Bi2O3 corresponding to the BiBO3 composition and subsequent cooling.

Two different phases are obtained, depending on the cooling conditions. Infrared and Raman spectroscopy, together with X‐ray powder diffractometry, lead to good combined evidence that both phases are polymorphs of bismuth orthoborate BiBO3. At 600°C, this compound is rapidly decomposed into a mixture of the stable phases predicted by the phase diagram, namely 2 Bi2O3.B2O3 and 3 Bi2O3. 5 B2O3.

The metastable character of BiBO3 near its melting point is thus clearly established.

The structures of these phases, and their stabilization by various cation substitutions are still under investigation.
Equilibre Prototropique des Aryl‐ et Alkylisoxazoline‐5‐Ones. Influence de la Basicité des Milieux Aprotiques
Authors: Maquestiau A. , van Haverbeke Y. , Muller R. N.
Published: September 2010

Alkyl‐ and arylisoxazolin‐5‐ones can exist as three prototropic forms. Percentage of ketonic CH structure decreases as hydrogen bond accepting power of the solvent raises. The equilibrium shifts then toward NH tautomer; nevertheless it seems necessary to consider participation of a 5‐hydroxyisoxazolic species in highly basic media; this is particularly evident for 3‐monosubstituted compounds.
NMR experiments on acetals. 51. On the origin of the conformational behaviour of the trimethylammonium substituent: ‐N+Me3substituted 1,3‐dioxanes and ‐CH2N+Me3substituted 1,3‐dioxolanes and 1,3‐dioxanes
Authors: van Cauwenberghe R. , Anteunis M. , Valckx L.
Published: September 2010

By a systematic investigation of ‐CH2N+Me3‐substituted 1,3‐dioxolanes and 1,3‐dioxanes, together with other conformational peculiarities (axial preference of a 5‐N+Me3grouping in 1,3‐dioxane) it is concluded that a C‐N+bond prefers to become parallel with (the) p‐lobe(s) of a β‐heteroatom.
NMR experiments on acetals. Part 52. Chair chair inversion in some symmetrically substituted gem‐dimethoxy‐cyclohexanes
Authors: De Beule H. , Anteunis M.
Published: September 2010

Barriers for ring inversion in 4,4‐diø, 4,4‐di c.propyl‐, and 4,4‐pentamethylene‐1,1‐dimethoxycyclohexane have been evaluated using different methods (Table 1). The close parallelism of the observed effect on ΔG≠ caused by gem. substitution in the present compounds as compared with correspondingly substituted 1,3‐dioxanes let to suppose that strain in rotations along C‐C bonds neighbouring the substitution site may contribute to the observed trends.
Stereochemistry of the mercurideboronation at a saturated primary carbon atom: Inversion of configuration
Authors: Gielen M. , Fosty R.
Published: September 2010

The mercurideboronation of tris‐erythro‐1,2‐dideuterio‐3,3‐dimethylbutylborane occurs with inversion of configuration in THF. The bromodemercuration of threo‐1,2‐dideuterio‐3,3‐dimethylbutylmercury chloride occurs with retention of the configuration in pyridine.
Composés oléfiniques et acétyléniques. III. Synthèse et stéréochimie de dérivés polybromés hexadieniques; obtention du 1,5‐hexadiyne‐3‐ene.
Authors: Figeys H. P. , Gelbcke M.
Published: September 2010

The bromination of 1,5‐hexadiyne at ‐40° in chloroformic solution gives 1,2,5,6‐tetrabromo‐1,5‐hexadiene (5) with a yield of 948; at higher temperatures (e. g. ‐15°), bromination of the double bonds occurs. The stereochemistry of (5) has been studied by N. M. R. ‐spectroscopy; the ratio of cis to trans double bonds (defined with respect to the two bromine atoms) is shown to be 1/9. When (5) is treated repeatedly with N‐bromo‐succinimide (NBS) in CCl4 solution, 1,1, 2,5, 6,6‐hexabromo‐2,4‐hexadiene (7) (trans, trans or cis, cis) is formed, implying a double allylic bromine migration; this structure is assigned on the basis of U. V.‐ and N. M. R.‐ evidence, in comparison with the spectroscopic properties of 1,2,3‐tribromopropene. Treatment of (7) with zinc powder in ethanol produces mainly trans‐1,5‐hexadiyne‐3‐ene (yield 57%), together with a small amount (2,8%) of the cis‐derivative.
Composés Oléfiniques et Acétyléniques. IV. Nouvelles Synthèses du 1,3,5‐Hexatriene; Électrodimérisation de L'Acroléine sur un Couple Zinc‐Cuivre
Authors: Figeys H. P. , Gelbcke M.
Published: September 2010

The electrodimerisation of acroleine on a zinc‐copper couple in the presence of acetic acid gives 1,5‐hexadiene‐3,4‐diol 5 in 76% yield, the ratio meso/dl being 60/40. Gas chromatographic analysis of the reaction mixture reveals the presence of threo‐ and erythro‐1‐hexene‐3,4‐diol and of the mono‐ and di‐acetates (meso/dl) of 4, especially when large quantities of acetic acid are used. Optimum conditions are described in order to minimize these side‐reactions. Starting from 4, two new routes to 1,3,5‐hexatriene 1 has been developped, namely by treating the bistosylate derivative of 4 with sodium iodide in 2‐(2‐ethoxy‐ethoxy) ethanol (adaptation of Linstead's reaction) and by a modification of Corey's method, where 4 is treated with N′, N′‐thiocarbonyl‐diimidazole and the resulting cyclic thiocarbonate decomposed in triphenylphosphite. Hexatriene is obtained respectively in 52 and 47% overall yield, the cis/trans ratios being 10/90 and 20/80. Although these reaction schemes appear to be non‐stereospecific, they constitute two new valuable methods to cis‐1,3,5‐hexatriene.
New Routes to Some New Partially Reduced Myrcenes
Authors: Anteunis M. , De Smet A.
Published: September 2010

We have tested out some preparations of regio‐selectively reduced myrcenes. New routes to the preparation of seq. trans‐2,6‐diMe‐2,6‐octadiene (Wilputte‐Steinert's method3 with Cr(CO)6 as the catalyst) and 2,6‐diMe‐2‐octane (Ru/C in MeOH:H2O) are reported. The Cr (CO)6 procedure needs only such mild conditions that epoxide rings are not cleaved. The preparation in moderate yields but unique fashion of a new dihydromyrcene (3‐Methylidene‐7‐methyl‐l‐octene) is also described.
German II ‐ Décomposition Thermique De L'hydroperoxy‐2 Méthyl‐2 Propionate De T. Butyle Dans Les Solvants Possédant Des Hydrogènes Labiles ‐ Cas Des Alcools Primaires et Secondaires
Authors: Rafii E. , Lena L. , Metzger J.
Published: September 2010

La décomposition thermique en phase liquide de l'hydroperoxy‐2 méthyl‐2 propionate de t.butyle 1, dans une série d'alcools secondaires et primaires a été étudiée. Dans ces solvants, la décomposition est plus rapide que dans les solvants ne possédant pas d'hydrogène labile. L'etude cinétique montre que lors de la décomposition thermique de l'hydroperoxyde l. dans les alcools secondaires et primaires linéaires, l'ordre par rapport à l'hydroperoxyde est respectivement 1 et 1/2. L'énergie d'activation est voisine de 20 kcal.mole−1

L'influence des inhibiteurs, les résultats de R. P. E., l'analyse qualitative et quantitative des produits des réactions, nous permettent de proposer trois réactions en chaîne de décomposition de l'hydroperoxyde 1. Le mécanisme “MH, YH” appliqué généralement lors de la pyrolyse des alcanes pour expliquer l'influence accélératrice de certains corps hydrogénés (YH), peut être applique à la décomposition en phase liquide de cet hydroperoxyde.
Fluorescence Quenching of Anthracene by Dimethyl‐ and Diphenylmercury
Authors: Donckt E. Vander , Lootens M. , Swinnen D. , Haquin C.
Published: September 2010

The fluorescence quenching of anthracene by dimethyl‐(DMM) and diphenylmercury (DPM) has been examined and compared in toluene and 95% ethanol as solvent. The rates of quenching by DMM and DPM are similar at room temperature. The application of the Arrhenius relationship shows that this is due to a fortuitous compensation of pre‐exponential and activation energy terms.

It is shown that the fluorescence quenching by DPM results only from an increased rate of intersystem crossing induced by the heavy‐atom molecule.
Chemical Studies of Marine Invertebrates. XII(1). Lemnacarnol, a Novel Sesquiterpene From the Soft Coral Lemnalia Carnosa
Authors: Tursch B. , Colin M. , Daldze D. , Losman D. , Karlsson R.
Published: September 2010

A novel, non isoprenic sesquiterpene alcohol, lemnacarnol, has been isolated from the Indo‐Pacific soft coral Lemnalia carnosa. Its structure and absolute configuration have been determined by single‐crystal X‐ray diffraction.
German Irradiation De L'Hexane et Du Decane Par Des Électrons Acceleres Effet De La Température Sur Les Produits Légers
Authors: Fontaine R. , Tilquin B. , Claes P.
Published: September 2010

The influence of the temperature on the yields of light radiolysis products of n‐hexane (‐70 to 60°C) and n‐decane (38° to 150°C) irradiated oy electrons at high dose rates has been investigated. Relative yields of unsaturates reach a maximum at a temperature which is a function of the irradiated alkane and of the gaseous products in the irradiated hydrocaroon. These temperature effects may be explained by a lowering of the solubility and by a competition between organic radicals recombination and hydrogen abstraction from the solvent molecule by these radicals as the temperature is raised.
Étude Par Spectrométrie Infrarouge De L'Interaction Entre Le Bromure De Tetrabutylammonium Et Quelques Dérivés Phenoliques
Authors: Bulinda J. B. , Zeegers‐Huyskens Th.
Published: September 2010

The hydrogen bonded complexes formed between tetrabutylammonium bromide and phenol derivatives are studied by infrared spectrometry in CCl4. The logarithm of the stability constants of complexes of 1:1 and 2:1 stoechiometry, and the frequency shifts of the stretching vibration IVOH are linearly related to the sum of the Hammett substitution constants. The influence of the proton donor concentration on the infrared spectrum and the structure of the complexes are discussed.
CNDO/2 Study of Polar Interactions in Acetonitrile
Authors: Paoloni L. , Hauser S.
Published: September 2010

The interaction of two acetonitrile molecules has been studied by the CNDO/2 approximation of the MO method. The antiparallel dipoles model obtains a 4.5 kcal/mole energy gain at a contact distance of 2.35 A. The skewed‐T interaction configuration gives an energy gain about ten times larger at a much shorter contact distance, 1.6 A. This latter model seems however much more affected than the other by the shortcomings of the CNDO/2 approximation.

The reported calculations indicate the skewed‐T interaction to be stronger than that of two antiparallel molecules, and suggest the possible presence of polymeric clusters in the liquid. Both interaction models evolve towards the formation of a (CN)2 unsaturated ring, which in turn might go into a more stable nearly‐tetrahedral cage structure.
Secondary Structures in Protected Homo‐Oligo‐L‐Norvalines. Comparison with Isomeric Oligo‐L‐Valines
Authors: Toniolo C. , Bonora G. M. , Fontana A.
Published: September 2010

The secondary structures of a homologous series of chemically and optically pure protected L‐norvaline homo‐oligomers, the synthesis and characterization of which is described in the preceding paper, were examined in a number of solvent systems using essentially CD*, and the results compared with those obtained in the isomeric L‐valine series. All protected norvaline and valine oligopeptides exist as statistical coil conformations in HFIP and HFA. In TFE, however, BOC‐(‐L‐Val‐)7‐OMe exists in a β‐associated structure in contrast to BOC(‐L‐Nva)7‐OMe. This finding points to the influence of β‐branching in directing peptide conformations. The addition of water to solutions of the protected norvaline and valine peptides in TPE forces the higher oligomers to assume intermolecular β‐type conformations. The aggregated structures could be disrupted by dilution or heating.
H Bonding Properties of Hydroxyl Held on the Surface of Silica
Authors: Sempels R. E. , Rouxhet P. G.
Published: September 2010

The H bonding properties of silica gel surface hydroxyl have been studied by adsorbing series of organic compounds which are weak H bond acceptors and by observing the OH stretching band. While the data are consistent with the charge transfer model of H bond, a critical examination shows that their support to this theory, as well as the support of similar data reported for solutions, is not really significant. All the results, and particularly relationships found between absorption coefficients, show a complete similarity between the characteristics of H bonds formed on the solid surface and in solutions.
Synthesis of Brominated Isophorone Derivatives
Authors: Verhé R. , Schamp N. , De Buyck L. , Vanloocke R.
Published: September 2010

Bromination of isophorone with excess of bromine in carbon tetrachloride at 0° gave 2,4,6‐tribromo‐3‐bromomethyl‐5, 5‐dimethyl‐2‐cyclohexenone which on further treatment with bromine afforded 2,4,6, 6‐tetrabromo‐3‐bromomethyl‐5, 5‐dimethyl‐2‐cyclohexenone. Bromination of isophorone and 4‐bromoisophorone at 25° gave rasp. 2,6,6‐tribromo‐ and 2,4,6‐tribromo‐3‐dibromomethyl‐5,5‐dimethyl‐2‐cyclohexenone.

The possible rearrangement in dimethylformamide and the catalytic hydrogenation of the bromo compounds were investigated. The reaction of isophorone oxide with hydrogen bromide did not give brominated products.
Reactivity of α,α‐Dihalogeno‐Imino Compounds Part VII: Reactivity of N‐1‐(2,2‐dichloroalkylidene)t. Butylamines
Authors: De Kimpe Norbert , Verhé Roland , De Buyck Laurent , Schamp Niceas
Published: September 2010

Treatment of N‐1‐(2, 2‐dichloroalkylidene)t.butylamines 1a‐c with excess methanolic sodium methoxide under reflux afforded mainly a mixture of α‐methoxy‐α,β‐unsaturated aldimines 2a‐c and the rearrangement products 3, besides small amounts of N‐t.butyl 2‐chloroamides 4 and N‐t.butyl 2‐chloro imidates 6. On the other hand, N‐1‐(2, 2‐dichlorobutylidene)t.butylamines 1d‐e gave α‐chlo‐ro‐α, β‐unsaturated aldimines, while α, α‐dichloropropylidene t.butylamine 9 provided mainly the α‐methoxy‐α,β‐unsaturated aldimine 11 next to the α‐me‐thoxyamide 12, α, α‐dimethoxyaldimine 10 and the rearrangement product 13. The reaction mechanisms are discussed.
Constituents of Peppers Part VII. Spectroscopic Structure Elucidation of Piperine and its Isomers
Authors: De Cleyn R. , Verzele M.
Published: September 2010

Piperine and its cis‐trans isomers isopiperine, chavicine and isochavicine are separated on preparative scale. Their spectral data are recorded and the structures are derived mainly from NMR data obtained at 300 MHz.
Etude des Metabolites De l'aspergillus Versicolor (Vuillemin) Tiraboschi
Authors: Berger Yves , Jadot Joseph
Published: September 2010

The modified “Prins reaction” between 4‐hydroxy‐l‐butene and 1,3,6,8‐tetramethoxyanthraquinone‐2‐carboxaldehyde gives mainly 1,3,6,8‐tetramethoxy‐2,2′e‐(4′e‐acetoxy‐tetrahydropyran) anthraquinone. The conformation of the reaction product was established by 1H‐NMR spectroscopy. There is non‐identity between this product and tetramethylversicorufin.
On the Relation Between Isomerization Modes for Idealized and Distorted Skeleta
Authors: Brocas J. , Willem R. , Fastenakel D. , Buschen J.
Published: September 2010

Permutational isomerization reactions[1][2] may occur in two extreme situations. If the n ligands do not distort the symmetry of the skeleton, then the permutations of the full permutation group Sn have to be classified [1,3] according to the symmetry group G of the idealized skeleton. If the ligands are sufficiently different, they will be blocked and will distort the skeletal framework. In this case, the allowed permutations belong to S′n, a subgroup of Sn and have to be classified [2] according to G′, the symmetry group of the distorted skeleton. In this paper, the relation between these two descriptions is analysed and illustrated on examples of chemical interest.
Surface analysis by secondary ion emission
Authors: Blaise G.
Published: September 2010

In a first part, the applicability of secondary ion emission to surface analysis is discussed by considering the ejection and ionization processes of atoms and taking into account the progressive erosion of the sample.

In a second part, the general features of the secondary ion emission induced by the adsorption of a gas are presented.

The effect of oxygen adsorption on M+ metal ion production is studied as a function of oxygen coverage for pure metals, alloys and single crystals. In particular, an incorporation process which takes place at a critical coverage is described on a nickel single crystal (100).
Electroanalytical Applications of Pulse Polarography and Voltammetry
Authors: Osteryoung Janet G. , Christie Joseph H. , Osteryoung Robert A.
Published: September 2010

Some resent developments in the applications of pulse polarography and pulse voltammetry are discussed, with emphasis on techniques which avoid problems associated with the capacitative background current in pulse polarography.
Standard Free Energy of Formation of CmCl3 in (Li‐K)Cl Eutectic
Authors: Martinot L. , Reul J. , Duyckaerts G. , Muller W.
Published: September 2010

From e.m.f. measurements in dilute solutions, we have calculated the standard free energy of formation of CmCl3 in (Li‐K)Cl eutectic between 400 and 600°C: ΔG°f = (‐ 753 000 + 315 T) J. mol−1.
Dosage d'Elements A l'etat de Traces dans les Eaux Souterraines au Moyen de l' Analyse par Activation Neutronique. I. Preconcentration au Moyen de la Resine Echangeuse d'Ions Dowex A1
Authors: Bury F. , Levert J. M.
Published: September 2010

L'article présente une méthode de préconcentration de traces d'éleménts lourds (Zn, Hg, Cr, Cd, Cu) dans les eaux en vue de leur dosage par activation neutronique. Le choix s'est porté sur la résine complexante Dowex Al. Les rendements de fixation ont été déterminés pour les éléments cités. L'influence du pH et de la force ionique a été étudiée et les conditions optima de fixation ont été établies. Cette étude montre que la résine Dowex A1 s'avère satisfaisante.
The Determination of Trace Oxygen in Aluminium and Aluminium‐Silicon Alloy by Helium‐3 Activation Analysis
Authors: Vandecasteele C. , Goethals P. , Kieffer P. , Hosted J.
Published: September 2010

The determination of oxygen in aluminium and aluminium‐silicon alloy by helium‐3 activation is studied. The 18 F formed from oxygen is separated by distillation followed by precipitation of leadfluorochloride. The chemical yield is determined by activation in an isotopic neutron source. Concentrations of resp. 27 and 64 ng. g−1 with a precision for a single determination of resp, 30 and 13% are found in 99. 5% aluminium and in aluminium‐silicon (3%) alloy.
Conformation et Stabilite des Differents Cycles Lactames Formes A Partir de l'acide 2(S), 5(S)‐Diamino 3(R)‐Carboxyadipique
Authors: Welter A.
Published: September 2010

The hydrolysis of a new naturally occuring γ lactam aminoacid has been studied.

Information is reported about the conformation and the stability of the 5 and 6 membered lactam rings which are present in the equilibrium during the hydrolysis.
Studies on Organophosphorus Compounds XIV. HMPA‐Induced rearrangements of N‐Benzyl‐carboxamides into 3‐phenylpropionitriles
Authors: Meyer H. J. , Goldman J. , Pedersen E. B. , Lawesson S.‐O.
Published: September 2010

N‐benzylacetamides, when refluxed in HMPA, undergo a rearrangement reaction by which 3‐phenylpropionitriles are produced.
Molecular Geometry of Trans, Trans‐1,2‐Dimethyl‐ and of Trans, cis‐1,2‐Dimethyl‐Ethylenesulfite; a Gas Diffraction Study
Authors: Geise H. J. , van Laere E.
Published: September 2010

The configuration of trans, trans‐1,2‐dimethyl and of trans, cis‐1, 2‐dimethylethylene‐sulfite, as suggested by NMR, is in agreement with electrondiffraction results in the gas phase. The best fit to the observed diffraction intensities was obtained with a non‐planar sulfite ring, ϕmax = 42.6°. In the trans, cis derivative the methyl groups are pseudo‐equatorial, whereas in the trans, trans compound one methyl is pseudo‐axial, the other pseudo‐equatorial. Although these are the best, static representations of the molecules, mixtures containing several conformations cannot be excluded.
Etude Structurale de 2‐Phenyl‐4‐[1′‐Heteroalkylidene]Oxazoline‐5‐Ones
Authors: van Haverbeke Y. , Maquestiau A. , Muller R. N. , Vanden Eynde J. J. , Zeegers‐Huyskens Th. , Rulinda J. B. , Leroy G. , Louterman‐Leloup G.
Published: September 2010

Fifteen 2‐pheny1‐4‐[1‐heteroalkylidene]oxazolin‐5‐ones are examined by IR and NMR spectroscopy. The only tautomeric form observed is the one exhibiting an exocyclic double bond. The XH exo E structure is confirmed by CNDO/2 calculations.
The Conductivity of Alkali Chlorides in the Mixture 96 wt % 2‐Methoxyethanol and 4 wt‐% Water
Authors: Vercruysse N. , Merken G. V. , Thun H. P.
Published: September 2010

Conductivity measurements in lithium, sodium and potassium chloride solutions have been carried out in a mixture of 96 wt % 2‐methoxyethanol and 4 wt % water. The value of the limiting molar conductivity for these alkali chlorides was of the same magnitude as for hydrogen chloride in this solvent mixture. It is shown that the conductance of the proton is governed by migration of the hydronium ion alone and that no proton‐jump mechanism is involved.
Structure Cristalline de la Phtalylphenylalanine
Authors: Michel A. G. , Durant F.
Published: September 2010

Phtalylphenylalanine (C17H13O4N) crystallizes in the monoclinic system, space groupe P21 with unit cell: a = 13.002; b = 5.819; c = 9.510 Å; β = 92.65°; z = 2. The structure has been determined by X‐ray diffraction, using direct methods and refined by Fourier synthesis and full‐matrix least‐squares techniques, to an R standard index of 0.045 (omitting unobserved reflections).

In order to put forward the change of conformation when substituting the benzoyl by the phtalyl group, the molecular structure is compared with that of benzoyl tyrosine ethyl ester.
Amino Steroids ‐ Preparation of 12‐Oxygenated Conanine Derivatives (Partial Synthesis of Dihydroholarrhenine)
Authors: van De Woude G. , van Hove L.
Published: September 2010

The title amino steroids have been synthesized from hecogenine acetate 10. The known convenient route for the synthesis of conanine derivatives involving as the key step a Hofmann‐Loeffler cyclization in a 20a‐methylaminopregnane structure revealed successful in the present case where the starting steroid system beared an oxygen function in the neighbourhood of the reaction sites.
Configurational Stability of Triorganostannylamines, ‐Phosphines and ‐Arsines
Authors: Gielen Marcel , Tondeur Yves
Published: September 2010

Stannylamines, ‐phosphines and ‐arsines are shown to be configurationally stable within the NMR time‐scale, even in the presence of a strong nucleophile. The configurational stability of triorganotin hydrides and the configurational unstability of triorganotin halide has been checked.
Homoconjugation of the Ions in Ternary Mixtures Iodine‐Pyridines‐Dichlorobenzene and Iodine‐Pyridines‐Nttrobenzene
Authors: Huyskens Pierre L. , Poskin Guy A.
Published: September 2010

The conductivities of ternary mixtures of equimolar solutions of iodine and various pyridines were determined at 298 K in ortho‐dichlorobenzene and in nitrobenzene. The concentrations of the binary solutions were of the order of 10−2 mole 1−1, In dichlorobenzene a maximum of conductivity appears when the volume fraction YA of the iodine solution lies near 0.67. In nitrobenzene this maximum occurs at YA 0.57 but the latter value increases when the concentrations of the binary mixtures become greater. Taking into account the predominant formation of 1/1 complexes, these results indicate that near the vicinity of the maximal conductivity there is a predominancy of the homoconjugated ions py2I+ and T5− with, in nitrobenzene, a non negligible contribution of the I3−, ions. These deductions are corroborated by the quantitative comparison of the conductivities with the real concentrations of the complexes and of the non‐complexed molecules computed from the experimental complexation constant. From these data the addition constant k2− of I2 to the I3− ion is also deduced. The order of magnitude of k2− is 850 l mole in ortho‐dichlorobenzene but it falls to 225 1 mole−1 in nitrobenzene, as a consequence of the higher electron acceptor character of this solvent which competes with iodine.
Synthese et Analyse Cristallographique par Diffraction de Rayons X d'un sel de Triazolium Forme a Partir de Nouveaux Reactifs Bis‐Electrophiles 1,4 derivant de la Condensation des sels de Phosgene Iminium et des Hydrazines Monosubstituees
Authors: Germain G. , Declercq J. P. , van Meerssche M. , Hervens F. , Viehe H. G. , Michel A.
Published: September 2010

Phosgeniminium salts condense with monosubstituted hydrazines to biselectrophilic reagents from which in particular the cyclisation with o‐aminophenol gives the triazolium salt (C13H20N5O)+Cl− described.

The structure of this salt has been determined by X‐ray diffraction. There are in the crystal 2 molecules in a P1 triclinic cell with dimensions a = 7.188, b = 9.007, c = 12.889 Å, α = 88.47, β = 75.20, γ = 74.79°.
Dosage du Fluor III. Extension du Domaine d'Utilisation de la Methode au PbCLF au Dosage de Poids de Fluor de l'ordre du Milligramme. Application A La Cryolithe et la Fluorine
Authors: Winkler Paul Edouard
Published: September 2010

After a thorough study in view to permit the choice of the best values of all the parameters in cause, the method of PbCLF has been adapted to weights of about one mg. of fluorine, the erros being then generally below 2%.

The procedure has been applied to cryolithe and fluorspar, after a selective dissolution of these minerals in a solution of Al(ClO4)3.

A correction based on the knowledge of the weights of chlorine contained in the precipitate of PbCLF, have provided the mean of improving the accuracy of the method.
The Enhanced Optical Stability of Sterically Hindered Triorganotin Halides
Authors: Gielen Marcel , Mokhtar‐Jamai Hassan
Published: September 2010

The optical stability of methylneophyltrityltin halides is greater than that of less sterically hindered triorganotin halides.
Charge‐Transfer Complexes in Organic Chemistry. Part XVI. Electron Affinity Values of Cyclic Anhydrides from Polarographic Measurements
Authors: Nagy O. B. , Lion H. , Nagy J. B.
Published: September 2010

Electron affinities of cyclic anhydrides are determined by polarographic technique. The results are in excellent agreement with those obtained from charge‐transfer spectra.
Étude de l'influence des Bases sur le Calcul de Grandeurs Moléculaires
Authors: Leroy G. , Reckinger G. , Ruelle J. L.
Published: September 2010

Within the framework of the Hartree‐Fock model, the efficiency of several atomic gaussian basis sets with respect to the computation of some molecular properties has been investigated in some simple compounds as well as in two charge transfer complexes.

Although, in general, each considered system or property requires the choice of a peculiar basis set (the more extended the larger the required accuracy), it is found here that the STO‐3G basis set gives uniform enough performance as to justify its use for the qualitative calculation of energetic and structural properties of chemical compounds.
The Use of a Vidicon Tube as Multichannel Detector in Emission Spectroscopy
Authors: Broekaert J. A. C.
Published: September 2010

The applicability of a vidicon tube for the recording of the intensities of spectral lines in atomic emission spectroscopy is investigated. The spectrometer, which consists of an Optical Multichannel Analyser (Princeton Applied Research) with a detector placed in the focal plane of a PGS‐2 spectrograph, is described. The possibilities of the system are illustrated with some preliminary results for the emission spectral determination of rubidium.
Benzo‐ and indoloquinolizine derivatives ‐ VIII: A Two‐step carbostyril preparation in the synthesis of dibenzo[a, f]‐and benz[f]indolo[2,3‐a]quinolizines
Authors: Tourwé D. , van Binst G.
Published: September 2010

The condensation between 2‐(2‐oxocyclohexyl)propionic acid and β‐arylethylamines, followed by dehydrogenation leads to 1‐β‐arylethylcarbostyrils in high yields, thus facilitating the Bishler‐Napieralski pathway to dibenzo[a,f]quinolizines. An illustration is presented with the synthesis of 6,7,12,13‐tetrahydro‐9,10‐dimethoxy‐11bH‐dibenz[a, f]quinolizine and 6,7,12,12b,13,14‐hexahydrobenz[f]indolo[2,3‐a]quinolizine. The octahydro‐2‐quinolone derivatives could not be reduced to the perhydro compounds, but resulted in a cyclised compound.
Contribution à l'étude theorique de la liaison hydrogène II. Les dimères de l'acide sulfhydrique
Authors: Leroy G. , Louterman‐Leloup G. , Ruelle P.
Published: September 2010

Pour poursuivre notre étude théorique de la liaison hydrogéne, nous avons calculé les propriétés des trois structures possibles du dimére de l'acide sulfhydrique. A nouveau, nous avons utilisé le programme ab initio GAUSSIAN‐7C (STO‐3G). Les principaux résultats sont les suivants: l'enchaînement S…H‐S le plus stable est quasi linéaire; la distance intermoléculaire S…H correspondante est de 2.766 Å avec une chaleur de formation de −0.6497 kcal m−1. En outre, l'approche de la seconde molécule d'H2S se fait, en première approximation dans l'axe d'un des centroïdes de l'atome de soufre accepteur de proton; c'est également sur cet axe que se situe le minimum de potentiel électrostatique.
Regiospecific singlet oxygen oxidation of (‐)R‐tetrahydrohumulone and hexahydrocolupulone
Authors: De Keukeleire D. , Siaens E. , Verzele M.
Published: September 2010

Hexahydrocolupulone (4) and (‐)R‐tetrahydrohumulone (5) are regiospecifically oxidized by singlet oxygen at ring carbon atom 4. The reaction proceeds by addition of singlet oxygen to the δ4‐5 enolic function with formation of a perepoxide intermediate. Rearrangement affords the 4‐hydroperoxy‐derivative, which is relatively stable only in the case of 4. Peroxide bond splitting and consequent radical reactions produce stable secundary products: 4‐hydroxy‐hexahydrocolupulone (7) in the oxidation of 4; tetrahydrohumulinone (9) in the oxidation of 5. The reactivity at the C4 enolic centre is comparable to that of trisubstituted alkenes. In contradiction with what has been found in the usual oxidation conditions, the hop bitter α‐acids are more sensitive towards singlet oxygen than the corresponding β‐acids.
On the stability of 4‐hydroxyhexahydrocolupulone
Authors: Siaens E. , De Keukeleire D. , Verzele M.
Published: September 2010

4‐Hydroxyhexahydrocolupulone (3) is transformed into (3‐methylbutyl) dihydrocohumulinic acid (6) in alkaline methanol‐water, while on heating (3‐methyl‐butyl) tetrahydroisocohumulone (5) is produced.
Estérification des Stéroïdes par l'Anhydride Heptafluorobutanoique
Authors: Dehennin L. , Levisalles Et J.
Published: September 2010

The formation of heptafluorobutanoic esters of some steroidal alcohols, phenol and conjugated ketone was described. The kinetic study of these reactions in presence of acid showed a hyperbolic relationship between kexp and the acid concentration for the alcoholic and phenolic functional groups. Under the same conditions, a bell‐shaped curve was obtained for the conjugated ketone.
Contribution a l'étude theorique de la liaison hydrogène IV. Les complexes (H2O)2, (HF)2, HF‐H2O, H2O‐HF
Authors: Leroy G. , Louterman‐Leloup G. , Ruelle P.
Published: September 2010

L'étude ab initio des complexes (H2O)2, (HF)2, HF‐H2O et H2O‐HF est effectuée en base double 4‐31G, grâce au programme Gaussian‐70. Les résultats obtenus confirment ceux des bases minimales. La géométrie des complexes semble déterminée par le potentiel électrostatique du partenaire accepteur de proton. L'optimisation des paramétres intramoléculaires ne s'avère pas indispensable.
Fragmentation d'Azoles Sous l'Impact Electronique. XII1. Isomérisation de l'Indole Avant Dégradation
Authors: Maquestiau A. , van Haverbeke Y. , Flammang R. , Menu A.
Published: September 2010

Indole and 2‐ethynylaniline behave similarly upon electron impact. Isomerization into a common structure before fragmentation is postulated on the basis of deuterium labeling experiments.
Aminoketenethioacetals from α‐chloronitriles.
Authors: Poupaert J. , Bruylants A.
Published: September 2010

A one‐step preparation of an aminoketenethioacetal from α‐chloronitrile is described: under the conditions of the Pinner reaction and subsequent thiohydrolysis, an aminoketenethioacetal is recovered as the main product. The structures of the by‐products are also discussed and a reaction mechanism is proposed.
Metal clusters in catalysis VIII Reduction of triple bonds
Authors: Muetterties E. L. , Olin Spencer T.
Published: September 2010

Reduction of triple bonds in simple molecules remains a relatively difficult, yet very important, type of transformation. The scientific challenge is a catalytic demonstration of this reaction paradigm with molecules like N2, CO, RCN, RNC, RN2+, and RCCR. Presented in a structural and electronic rationale is a potential solution to the challenge with metal cluster catalysts. Relationships of the rationale to metal surface and metalloenzyme reactions are discussed. Basic structural forms considered in the context of bond order reduction and resultant ease of reduction (hydrogenation) are: magnified image.
Contribution a l'étude du Cycle Pyrazolinique: Synthèse et Détermination de la Structure de Quelques Pyrazolines‐2
Authors: Ait Ouyahia A. , Leroy G. , Weiler J. , Touillaux R.
Published: September 2010

Dans ce travail, nous avons synthétisé plusieurs pyrazolines‐2 par isomérisation, en milieu acide, des pyrazolines‐1 correspondantes. L'étude radiocristallographique et spectroscopique des pyrazolines‐2 considérées démontre la non planéité du cycle. L'épimérisation de ces composés, en milieu acide, fournit en majorité l'épimère trans.
Imidazoline‐4‐Ones: Synthèse et Tautomérie
Authors: Maquestiau A. , van Haverbeke Y. , Flammang‐Barbieux M. , Willame M.
Published: September 2010

Some new imidazolin‐4‐ones are described. The carbonyl tautomers predominate in solution when the substituents are alkylgroups. A slow dimerization process is observed. Phenylated compounds offer a mixture of hydroxyl and carbonyl tautomers in different proportions depending on the nature of the solvents.
D‐Ribose, D‐xylose and some of their glycosylamine derivatives. A 300‐MHz 1H‐NMR study
Authors: De Bruyn André , Anteunis Marc , Claeyssens Marc , Saman Eric
Published: September 2010

The 1H‐n.m.r. parameters of the major tautomers of D‐xylose and D‐ribose have been determined, and the conformational features are discussed. α‐ And β‐D‐ribopyranose dissolve in D2O to give a conformational mixture of 4C1 and 1C4 forms; the 4C1 form accounts for 40% of the former and for 70% of the latter. β‐D‐Ribo‐, and β‐D‐xylopyranosylamines have been synthesized and their 1H‐n.m.r. parameters suggest 4C1 to be the unique conformation in D2O. Some N‐aryl‐D‐glycopyranopyramines derived from these pentoses were also prepared and, at variance with literature proposals, the chair form having an equatorial anomeric substituent is the preferred conformer throughout the series.
Role of specific interactions in the formation of ions
Authors: Huyskens Pierre L.
Published: September 2010

A specific interaction between an electron acceptor A and an electron donor D can be at the origin of the formation of ions. In most cases however the ions are not A− and D+ but their formation results from the weakening of a chemical bond in the electron acceptor molecule as a consequence of the formation of the specific bond and the subsequent breaking of this bond leaving the entities A'− and p+ ‐D, p+ being a positive ion. The transfer of p+ from A'− to D causes an increase of the dipole moment of the complex and an important decrease of its volume which is not restricted to the region of the specific bond itself. This transfer is influenced by changes in the dielectric constant of the medium but also even to a greater extent by further specific interactions between the partners and the surrounding molecules. These two factors also play a role in the dissociation of the ion‐pairs. However, it is shown that in many cases the possibility of formation of supplementary specific bonds rather disfavours the dissociation because they stabilize more the ion‐pairs than the free ions.
Specific role of the two nitrogen sites of azoles in their interactions with ions
Authors: Cl. Haulait‐Pirson M.
Published: September 2010

From conductimetric measurements, the dissociation constant Kd of triethylammonium picrate in nitrobenzene was determined in the presence of various concentrations of pyrazole and of benzimidazole. The equilibrium constants for the association of pyrazole with triethylammonium cation (Et3NH+) and of benzimidazole with Et3NH+ and with the picrate anion have been calculated. From these results and those obtained previously, it appears that the order of decreasing affinity of the tertiary nitrogen of the azoles for Et3NH+ is imidazole‐1‐methylimidazole benzimidazole pyrazole, whereas the proton donor character of the imino group is greater for benzimidazole than for imidazole. The basic strength of the azoles is compared with that of pyridine and discussed.
On the origin of the axial behaviour of 5‐halomethyl groups in 1,3‐dioxane. Evidence for non‐bonded electrostatic attraction
Authors: Borremans Frans , Anteunis Marc J.O.
Published: September 2010

The conformational behaviour of the halomethyl group in 5‐position in 1,3‐dioxanes is determined quantitatively by low temperature nuclear magnetic resonance, and the origin of the axial preference of ca. 1 kcal.mole−1 relative to the 5‐methyl group is disclosed and discussed in terms of a local electrostatic attraction in XC‐C‐C(H)Y fragments, having a double gauche conformation (X, Y electronegative elements).
Stéréoisomérie de sulfures insaturés en série pyrazoline‐, isoxazoline‐ et oxazoline‐5‐ones
Authors: Maquestiau A. , van Haverbeke Y. , Vanovervelt J. C. , Postiaux R.
Published: September 2010

The stereoisomerism of 39 4,1'‐alkyl(aryl)thioalkyl(aryl)idenepyrazolin‐, isoxazolin‐ and oxazolin‐5‐ones in various solvents has been investigated by NMR spectroscopy. The exocyclic sulfur atom induces the interconversion of the two stereoisomers exo Z and exo E. The part played by the solvent and the steric interactions in the equilibrium composition is discussed.
Chemical studies of marine invertebrates. XXIV. Minor cembrane diterpenes from the soft coral sinularia flexibilis (coelenterata, octocorallia)
Authors: Herin M. , Tursch B.
Published: September 2010

6ϵ‐hydroxysinulariolide (3), 11‐dehydrosinulariolide (4), R(‐)‐cembrene A (10) and 3,4,11,12‐diepoxycembrene A (13) have been isolated from the soft coral Sinularia flexibilis.
Procedure and computer programmes for the determination of the structure of gaseous molecules from electron diffraction data
Authors: Van Enden L. Den , van Laere E. , Geise H. J. , Mijlhoff F. C , Spelbos A.
Published: September 2010

An outline is given of the procedure and computer programmes used by the electron diffraction groups of the universities of Leiden and Antwerp for the determination of the structure of molecules in the gaseous phase.
Fragmentation des 4‐ et 5‐hydroxy‐1,2,3‐triazoles sous l'impact électronique
Authors: Maquestiau A. , van Haverbeke Y. , Willame M. , Begtrup M.
Published: September 2010

The tautomeric composition of 4‐ and 5‐hydroxy‐1,2,3‐triazoles in the gas phase has been investigated by comparison with the fragmentation of their fixed forms.
Enamine chemistry – XV. The reaction of enamines with α‐halogeno electrophilic olefins
Authors: Madsen J.Ø. , Lawesson S.‐O.
Published: September 2010

Reaction of cyclohexanone enamines with α‐chloroacrylonitrile and methyl α‐chloroacrylate in polar solvents leads to hexahydroindolium salts of type 3. In ether solution at low temperature cyclobutanes, 9, are produced.
Analyses in turbulent hydrodynamic voltammetric cells
Authors: Punqor E. , Varadi M.
Published: September 2010

Authors describe the main parameters of the turbulent flow hydrodynamic voltammetry and some analytical applications are given.
Complexes of tertiary thioamides part I: Complexes of dimethylthioformamide with Co(II), Ni(II) and Pd(II)
Authors: Aarts A. J. , Desseyn H. O. , Herman M. A.
Published: September 2010

Some complexes of dimethylthioformamide (DMTF) and CO(II), Ni(II) and Pd(II) are investigated by electronic, infrared and when possible, Raman spectroscopy. Ni(II) forms octahedral complexes: trans NiL4Cl2 and (NiL6) (Clo4)2; Pd(II) forms square planar complexes: trans PdL2X2 (X=Cl, I) and (PdL4) (Clo4)2; Co(II) forms tetrahedral complexes: CoL2X2 (X=CI, I). DMTF coordinates in all cases through sulphur as a monodentate.
Synthetic studies on rosane diterpenes. Synthesis of (±) 2ß‐Benzoyloxy‐1,2,3,4,4a,4bα,5,6,7,8,10,10aα‐dodecahydro‐4aβ, 8‐dimethyl‐8β‐carboxy‐phenanthrene
Authors: Banerjee A. K. , Narvaez M. , Bolivar E. H.
Published: September 2010

The title compound (IIIa) has been synthesised from α,β‐unsaturated ketone (VIIa). The structure and stereochemistry of some of the products obtained during this synthetic study have been determined.
Dynamique des Réactions Chimiques: Isomèrisations du Cyclopropane et Réaction de Diels‐Alder. (Conférence présentée dans le cadre du Congrès des Chimistes Théoriciens d'Expression Latine, à Wépion‐Belgique le 24 août 1976)
Authors: Chapuisat X.
Published: September 2010

Une étude dynamique théorique des isomérisations optique et géométrique du cyclopropane et de ses dérivés lourdement substitués est présentée. Elle conduit aux conclusions suivantes:−l 'énergie de vibration des groupes méthylènes terminaux de la molécule énergisée requise pour que les isomérisations se produisent est plus grande que prévue sur la base de calculs de Chimie Quantique “statiques”;

‐quelle que soit l'énergie totale, il existe des domaines d'énergie de vibration où la réaction a lieu, qui alternent avec des domaines non réactifs (structure en bandes);

‐dans la majorité des trajectoires réactives les groupes méthylènes ne tournent qu'une seule fois dans le diradical intermédiaire;

‐lorsque le cyclopropane est substitué, la position angulaire de l'état de transition est un facteur dynamiques plus important que sa hauteur (à 2 kcal/mole près).

Des résultats dynamiques préliminaires sont présentés pour la réaction de Diels‐Alder. Ils permettent d'élucider en partie les divergences expérimentales selon que l'on se place du point de vue de l'énergie d'activation (thermochimie) ou de celui de l'entropie d'activation (stéréochimie et cinétique chimique).
Progrès recents dans L'étude de la Solvatation et de la Fixation de Cations des Groupes I et II par L'approche supermoléculaire ab initio
Authors: Pullman Alberte
Published: September 2010

L'état actuel de l'approche supermoléculaire microscopique utilisée pour l'étude de l'hydratation des constituants des molécules biologiques fondamentales et de leur interaction avec les cations alcalins et alcalino‐terreux, est brièvement résumé.