bluuebunny/crossref_metadata_2025_split huggingface dataset:
Physical and Chemical Relaxations in Ethylene Following CO2‐Laser Irradiation Time of Flight Observations
Authors: De Keuster D. , De Hemptinne X. 
Published: September 2010

AbstractPhenomena induced in ethylene subsequent to low intensity c. w. irradiation with several lines of the CO2‐laser emission are investigated by means of a time‐of‐flight technique and mass spectroscopic analysis on‐line. Variety of behaviours of the different lines is confirmed: some excite preferentially 1ν7, others excite probably a higher vibrational level (2ν7). Vibrationally hot ethylene is converted into a new substance, which may be an excimer stabilized excited state. This substance is shown to react with oxygen.
Anharmonicity Correction and Molecular Constants of Some Linear Triatomic Molecules
Authors: Sengodan V. , Srinivasacharya K. G. 
Published: September 2010

AbstractThe anharmonicity correction factors for some linear triatomic molecules are estimated by the method of Dennison (1). The potential constants are calculated by means of three different methods — Wilson's F‐G matrix method, Kinetic constants method and L‐approximation method — using the presently evaluated harmonic frequencies. The potential constants thus obtained are utilised in calculating the other molecular constants such as mean amplitudes of vibration, shrinkage effect, compliance constants, Coriolis coupling constants and centrifugal distortion constants for the first time. The results are discussed briefly.
Variation De La Sensibilité Des Ions Lors De l'analyse D'Une Série D'Alliages Cuivre‐Aluminium Par Spectrométrie De Masse À Étincelles
Authors: Mathieu G. , Lamberts L. 
Published: September 2010

AbstractAn average relative sensitivity factor kAl/Cu is determined in a series of copper‐aluminium alloys, whereas Cu+ and Al+ normalized ionic abundances are shown to increase with Cu atomic concentration in the alloys. This is explained by a broadening of the ionic beam with increasing Al atomic concentration which modifies the fraction of the beam intercepted by the monitor plate.
Dissociations Induites par Collisions et Réactions D'Acquisition de Charge de Cations [C2H5N]+,(1)
Authors: Maquestiau A. , van Haverbeke Y. , Flammang R. , Menu A. 
Published: September 2010

AbstractCollision induced dissociations have been used to characterize the isomeric stable structures of [C2H5N]+. radical cations and the results are in good agreement with previous studies concerning the reactive ions. The competitive fragmentations of [C2H5N]++ cations formed by charge stripping processes have also been observed. The reproducibility of the abundance ratios confirms the usefulness of these metastable fragmentations for the structural investigation of monocharged positive ions via their doubly charged analogs.
Reactions of Halocyclopropanes. IV. N‐Alkylation in the Presence of Silver Perchlorate
Authors: Arct J. , Prawda A. , Kozyriew W. 
Published: September 2010

AbstractSilver perchlorate catalyzed reactions of certain gem‐dibromocyclopropanes with nitriles were carried out in the presence of pyridine. Depending on the type of cyclopropane derivative, N‐(β‐haloallyl) amides or β‐haloallylpyridinium perchlorates were obtained.
Chemical Studies of Marine Invertebrates. XXXIX. Three Novel Diterpenoids from the Soft Coral Xenia Novae‐Britanniae
Authors: Braekman J. C. , Daloze D. , Tursch B. , Declercq J. P. , Germain G. , van Meerssche M. 
Published: September 2010

Abstract13‐epi‐9‐desacetylxenicin (2), isoxeniolide‐A (3) and 7, 8‐oxido‐isoxeniolide‐A (4), three novel nine‐membered diterpenoids have been isolated from the alcyonarian Xenia novae‐britanniae. Their structures have been established on the basis of their spectral properties. Structure 2 has been confirmed by X‐ray diffraction analysis.
Analytical Fractionation of Homogenates from Ehrlich Ascites Tumor Cells
Authors: Londos‐Gagliardi D. , Zenebergh A. , Aubel‐Sadron G. 
Published: September 2010

AbstractHomogenates of Ehrlich Ascites tumor cells have been assayed for cytochrome c oxidase, β‐N‐acetylglucosaminidase, acid deoxyribonuclease, α‐L‐fucosidase, inosine diphosphatase, NADH and NADPH cytochrome c reductase, phosphoglucomutase, RNA and UNA. The optimal conditions for each enzyme assay have been established. The subcellular fractions have been obtained by differential centrifugation and identified by their specific enzyme markers.
Comportement de 1‐(3,4‐Diméthyl‐5‐Isoxazolyl)‐3‐Aryltriazenes et de Diaryl‐1,3Triazenes Sous L'Impact Electronique
Authors: Maquestiau A. , van Haverbeke Y. , Flammang R. , Willame M. , Vernin G. , Siv C. , Metzger J. 
Published: September 2010

AbstractThe mass spectra of 1‐(3,4‐dimethyl‐5‐isoxazolyl)‐3‐aryltriazenes may be interpreted on the predominance, in the vapor phase, of the structure A in which the azo group is conjugated with the heterocyclic moiety. This tautomer generates an isoxazolyl diazonium ion b wich rearranged before the loss of nitrogen. Para substituents on the aromatic ring have a weak influence on the displacement of this tautomeric equilibrium.Similarly, the mass spectra of 3‐aryl‐1‐p‐tolyl‐triazenes show that the equilibrium is only weakly influenced by the position and the nature of the substituent on the aromatic ring.
Synthesis and NMR Spectra of Substituted 1,4,5,8‐Tetraazaphenanthrenes(TAP)
Authors: Maetens D. , Vandendijk D. , Nasielski‐Hinkens R. 
Published: September 2010

AbstractThe synthesis of ring A substituted TAP'S starts from 5,6‐diaminoquinoxaline (II), which is condensed with n‐butylglyoxylate to give a mixture of 2‐ and 3‐hydroxy‐TAP, which reacted with POCl3/PCl5 to afford the corresponding monochlorocompound. Similarly, the condensation of II and ethyl oxalate produces 2,3‐dihydroxy‐TAP; this gives 2,3‐dichloro‐TAP with the same chlorinating agents. Nucleophilic substitution of the chlorine atom(s) (sodium methoxide, piperidine, hydrazine) occurs with high yields. The monohydrazino‐TAP's were oxidized into the corresponding monodeuterated derivatives, which allow an unambiguous assignment of the 1H NMR spectrum of TAP itself.
Conformational Aspects of the CIS‐Trans Isomers of N‐Methyl‐L‐Thiazolidine‐4‐Carboxylic Acid Hydantoin Oxide
Authors: Anteunis Marc J. O. , Nachtergaele Willy A. , Budêšínský Miloś 
Published: September 2010

AbstractThe isomeric assignments and respective conformations in solution of the oxidation products of N‐Me‐L‐Thiazolidine‐4‐carboxylic acid hydantoin are described. The cis‐sulfoxide isomer occurs mainly in an envelope with Cδ as the flap down (δ−). The trans‐isomer is somewhat more deformed with a conformation close to the α−. Comparison of shifts with the parent sulfide allows a collation with tendencies observed in hexacyclic sulfoxides.
1H NMR Spectrum and Solution Conformation of Alborixin Free Acid
Authors: Rodios Nestor A. , Anteunis Marc J. O. 
Published: September 2010

Abstract1H NMR spectra in chloroform and benzene of Alborixin (Fig. 1) and the data extracted thereof (Tables 1 and 2) are presented. They agree with the conformation of Alborixin reported from x‐ray studies revealing its resemblance with the ionophore X‐206 previously studied in solution. Some differences in the spectra of Alborixin and X‐206 are commented.
Étude Theorique de la Prototropie des Imidazolide‐5 (4)‐Ones
Authors: Sayarh Abderrahim , Gelize‐Duvigneau Michel , Arriau Jean , Maquestiau André 
Published: September 2010

AbstractThe theoretical study of the tautomeric equilibrium of imidazoline‐5 (4)‐ones carried out by two different routes, eg:
‐energetic analysis of the molecular entities with consideration of the solvation term.
‐examination of the protonation sites of the common anion shows that, in agreement with the experimental results, the preponderant tautomeric form, as well in the vapor as in solution, is the non conjugated carbonyl form.
Studies On Organophosphorus Compounds XXIX Thiation of Ethyl 2‐Acylaminobenzoates
Authors: Clausen K. , Lawesson S.‐O. 
Published: September 2010

AbstractBy heating ethyl 2‐acylaminobenzoates, 2, with the dimer of p‐methoxy‐phenylthionophosphine sulfide, 1, at 80°C a mixture of ethyl 2‐thioacylamino‐benzoates,3, 2‐substituted 3, 1‐benzothiazin‐4‐ones, 4, and 2‐substituted 3, 1‐benzothiazine‐4‐thiones, 5, is obtained. By raising the reaction temperature to 140°C 5 is obtained as the only product. In all reactions between 2 and 1 three phosphorus‐containing compounds, 6‐8 are isolated. 2‐Substituted 3, 1 ‐benzoxazin‐4‐ones, 9, when reacted with 1 give mixtures of 4 and 5 due to a rearrangement reaction. Carbon‐13 NMR data are tabulated for the carbonyl‐, thiocarbonyl‐ and iminocarbons.
The influence of space group symmetry, pseudosymmetry and atomic scattering power on the path of the residual
Authors: Lenstra A. T. H. 
Published: September 2010

AbstractThe residual (<Iobs ‐ Icalc2>/ <I2 obs > is a very useful function in structure evaluation procedures. Using simple properties of the Patterson function algebraic expressions for the residual are derived. It is shown that the numerical value depends on various factors such as the presence of heavy atoms or pseudosymmetry in the structure. It appears that coincidence of interatomic vectors increases the value of the residual.The Influence of the origin peak in the Patterson function on the residual is described.
Ionisation chimique De Structures Hydroxypyridines
Authors: Maquestiau A. , van Haverbeke Y. , Flammang R. , Mispreuve H. , Katritzky A. R. , Ellison J. , Frank J. , Meszaros Z. 
Published: September 2010

Abstract“Collision Induced Dissociation/Mass analyzed Ion Kinetic Energy” (CID/MIKE ) spectrometry is applied to study the structure of cations generated by the chemical ionisation of hydroxypyridines and related compounds.The method described allow, in many cases, the determination of tautomeric structures in the gas phase.
Isomerization modes for idealized and distorted skeleta (II). Polytopal isomerization reactions
Authors: Brocas Jean , Willem Rudolph , Buschen Jacques , Fastenakel Daniel 
Published: September 2010

AbstractWe establish a theoretical description of Isomerization reactions whose polytopal character is only due to the presence of different ligands on the molecular skeleton. The present approach provides a relation between isomerizations occurring for different ligand partition of a given molecular skeleton. The usefulness of the present description is discussed on several examples of chemical interest.
Structure effects in the interaction of hydrogen with benzene, cyclopropane and carbon monoxide over silica supported nickel catalysts
Authors: Coenen J. W. E. , Schats W.M. T. M. , van Meerten R. Z. C. 
Published: September 2010

AbstractStudies on the catalytic interaction of hydrogen with three substrates on a series of silica supported nickel catalysts with average crystallite sizes ranging from 5 to 50 A are reported. On benzene the specific activity is almost constant down to about 12 A crystallite size. For smaller crystallite sizes the activity drops sharply. For hydrogenation and hydrogenolysis of cyclopropane a similar drop in activity is observed for very small crystallites and these also tend to have lower selectivity towards hydrogenolysis. These findings are discussed In terms of the required ensemble size, inspired by work on alloys elsewhere. For methanation of carbon monoxide an almost linear increase of specific activity with crystallite size over the entire range has been found, which implies almost constant activity per unit mass of nickel metal for all catalysts. In the course of many hours methanation heavy carbon deposition and growth of average nickel crystallite size occur, without significant change in activity. Interpretation of these findings in terms of required ensemble size does not appear very satisfactory. Much further work is needed to arrive at a satisfactory explanation
Skeletal rearrangements of hydrocarbons on metals
Authors: Gault F. G. , Amir‐Ebrahimi V. , Garin F. , Parayre P. , Weisang F. 
Published: September 2010

AbstractThis paper is a report of some new investigations in the field of skeletal rearrangements on metals.The kinetics of isomerization are considered first. While in the case of pentanes and hexanes the orders vs hydrogen of the various elementary steps are negative, they are positive in the case of heptanes. However it is shown by using 13C‐labeled molecules that no scrambling of the label occurs during the isomerization process. The rate‐determining step then is in all cases the skeletal rearrangement of a highly dehydrogenated species. In order to account for the change of orders vs hydrogen, the multisite model proposed by Frennet and coworkers (J. Catal 53, 150, 1978) is adapted to skeletal isomerization.The particle size effects in isomerization of 2‐methylpentane to 3‐methylpentane and in methylcyclopentane hydrogenolysis are considered next. It is shown that both bond‐shift and cyclic‐type isomerizations take place one the same sites, presumably the edge atoms of the crystallites. Two limiting sizes are defined: one at 10 Å below which bond‐shift isomerization is converted into non‐selective cyclic type isomerization. The second one at 25 Å, below which the hydrogenolysis of methylcyclopentane changes from selective to nonselective. Possible crystallographic models are discussed, which could explain the results. None of them is satisfactory and it is suggested that the changes of mechanisms are due to changes in the electronic structure of the metal particles. This view is corroborated by a comparative study of the isomerization of 13C‐labeled hexanes on various group VIII metals.In the last section, one of the bond‐shift mechanisms and the two cyclic mechanisms, selective and non selective, are described in details. The bond‐shift isomerization is best described as a reversible dismutation of metallo‐cyclobutane into metallocarbene of internal CC bonds in isopentane and n‐pentane. On the other hand, the non‐selective and selective cyclic mechanisms for isomerization are represented as dicarbene and dicarbyne recombinations respectively. The importance of metallocarbenes and metallocarbynes for other types of skeletal rearrangement such as hydrogenolysis is also emphasized and a classification is given for the contact reactions of hydrocarbons on metal surfaces.
Catalytic reactions of ethane and n‐Butane as a tool for characterization metallic surfaces
Authors: Guczi L. , Matusek K. , Sàrkàny A. , Tétényi P. 
Published: September 2010

AbstractIn the present paper the final goal is to use the hydrogenolysis of hydrocarbons as a diagnostic tool for characterizing the metallic surface, i.e. to give a technique for drawing conclusions about the character of a metallic surface itself from the observed kinetic parameters. The main features are as follows:Surface properties of a transition metal are essentially determined by the electron structure and geometry of the bulk, members of the group VIII metals possess, therefore, apriori activity in the hydrogenolysis of a given hydrocarbon. Vulcano shaped curves observed in the hydrogenolysis of ethane, n‐pentane, may, therefore, be an indication that neither too strong, nor too weak interaction between the catalyst surface and the substrate is good for the optimum catalyst performance.In addition to the ability of a metal in the “weak” to “strong” type of interconvension conceptualized earlier, the kinetic parameters may be influenced by some additional factors e.g. temperature, hydrogen pressure and the aging of the catalyst. A systematic change in the catalyst structure of platinum and ruthenium results in a characteristic variation in the activity of ethane and n‐butane hydrogenolysis as well as in selectivity. By carefully analysing the limiting factors mentioned the effect of different supports, metallic dispersion, impregnating substrate, alloying with iron and rhenium and adsorbed sulphide on the activity and selectivity was determined.
Dehydrogenation and dehydrocyclization over bimetallic catalysts: Problems solved and problems generated by basic research
Authors: Biloen P. , Helle J. N. , Sachtler W. M. H. 
Published: September 2010

AbstractThe discussion is devoted to some controversial points related to the aromatization of paraffins at high temperature (around 500°C), and low hydrogen pressure (1–8 bar) over non‐acidic catalysts, in particular platinum plus a second component on a neutral(ized) support.Special attention is paid to those points which relate to the question why the second component enhances the stability of the dehydrocyclization (DHC) activity of supported platinum.We first consider the valence state of the second component. On the basis of, among other factors, the total hydrogen uptake we argue that at least part of the second component is present in the reduced state, while TPR points to alloy formation.A comparison of the catalytic and chemisorptive behaviour of bulk alloys with that of supported bimetallics indicates that modification (alloying) of the gas phase‐exposed platinum surface is an essential action of the second component. This, in turn, suggests that the superior stability of bimetallic DHC catalysts is related to the catalytic properties of the alloys.Considering the changes in selectivity observed upon alloying we will argue that the most important one is the enhanced selectivity towards dehydrogenation of paraffins (olefins) to the corresponding olefins (poly‐olefins), which leads to the question: “Are bimetallics under DHC conditions merely selective dehydrogenation catalysts?”From the invariance in TON for dehydrogenation per surface‐exposed platinum atom up to very high dilution of platinum in gold (< 1% at Pt in Au), we infer that only one platinum atom is involved in the rate‐determining step.We will extrapolate the aforementioned results to actual DHC catalysts and consider the proposition that the active site in PtSn, PtRe (S), Pt (S) and deactivated Pt (i.e. Pt (C)) DHC catalysts consists of one platinum atom embedded in an “inactive” matrix.Finally we will list some points deserving further study, amongst them the interpretation of the results of techniques such as TPR, the relative importance of different DHC pathways, the chemisorptive properties of alloys and the causes underlying the low hydrogen uptake of “overreduced” supported platinum catalysts.
Kinetics, energetics and structure of hydrogen adsorbed on transition metal single crystal surfaces
Authors: Christmann K. 
Published: September 2010

AbstractSome recent results on the interaction of hydrogen with low‐index planes of Ni, Ru, Pd and Pt are reported abs compared in order to gain more general and sight into elementary processes involved in heterogeneously catalyzed reactions with hydrogen or hydrocarbon as reactants. Starting off from a consideration of factors which govern the rate of the adsorption/desorption steps the energetics of the hydrogen chemisorption is discussed. The energy of the hydrogen‐metal bond as derived from both isosteric heat or thermal desorption measurements is discussed in terms of its absolute value and analysed with respect to its coverage dependence, thus reflecting both the strength of the metal‐adsorbate and the adsorbate‐adsorbate interaction. It is shown with the aid of some selected examples that ordering phenomena within hydrogen adsorbate layers may occur and can be readily detected by low‐energy electron diffraction. As a consequence, important information about the nature of the H‐H interaction on transition metal surfaces is obtained.
Reaction of methane with nickel single crystal surfaces and the stability of surface nickel carbides
Authors: Schouten F. C. , Gijzeman O. L. J. , Bootsma G. A. 
Published: September 2010

AbstractThe decomposition of methane on several low index faces of nickel has been studied by Auger electron spectroscopy. Differences between the (111), (110) and (100) plane are found, both in sticking probability and decomposition kinetics. Carbon deposited on the (110) and (100) plane diffuses into the bulk at higher temperatures (600‐700 K). A model for this process is proposed from which the binding energies of several kinds of surface carbides may be derived.
Adsorption of hydrocarbons on nickel catalysts as studied by magnetic methods, and application to the study of hydrogenolysis and D2 ‐ hydrocarbon exchange reactions
Authors: Martin G. A. , Dalmon J. A. , Mirodatos C. 
Published: September 2010

AbstractThe decrease of saturation magnetization of nickel upon hydrocarbon adsorption gives information on the nature of chemisorbed species. It is shown that a low coverages and moderate temperature (300K), hydrocarbon molecules undergo a substantial dehydrogenation; for higher temperature (400K) molecules are completely dehydrogenated and cracked according tomagnified imageThe adsorbed species involve a large number of Ni atoms. Hydrocarbon adsorptions are inhibited by addition of Cu atoms (alloying) or by preadsorbed hydrogen, and this is interpreted in both cases in terms of dilution effect of the active phase (Ni) by Cu or H atoms.Consequences on hydrogenolysis and exchange reactions are examined, and comparison between predicted characteristics and experimental data are presented in the case of ethane, propane, butane hydrogenolysis over Ni and Ni ‐ Cu catalysts, and deuterium‐methane and ethane exchange over Ni catalysts.
Compensation effect associated with multisite adsorption and competition for adsorption
Authors: Degols L. , Frennet A. , Crucq A. , Lienard G. 
Published: September 2010

AbstractAccording to a model of “landing site” for chemisorption of alkanes on metal in presence of H2, previously published, the hydrocarbon adsorption rate is proportional to a function G of the H coverage (ΘH). The observed variations with H2 pressure and temperature range of the temperature factor affecting the adsorption rate of CH4 and C2H6 may be accounted by the variation of the temperature factor affecting this function G when its temperature dependency is expressed by the Arrhenius equation.A compensation effect (C. E.) then appears between the kinetic factors of this function G when the experimental parameters (pressure, temperature) are varied. In the particular case of rhodium, the variations of the temperature factor may be as large as a few tens of Kcal/mole.When working at constant ΘH, the slope of the compensation curve is equal to (RT)−1 while the slope deviates from this value if the two practical parameters ‐pressure and temperature‐ are maintained constant. The question arises if C. E., in heterogeneous catalysis, is not principally due to the way used to calculate the kinetic factors the adsorption rate assuming an Arrhenius‐like dependency.
On the application of ‘restoring force balance’ condition for the evaluation of force fields of some polyatomic molecules
Authors: Palaniappan PL. RM. , Karunanithi S. 
Published: September 2010

AbstractA method is suggested to utilise the ‘Restoring force balance’ criterion of Redington and Aljlbury along with one set of isotopic frequencies for the evaluation of molecular force fields by Parametric Representation method. Fluoroform and formaldehyde molecules are taken as illustrations. In order to check the validity of the method other molecular constants such Coriolis coupling constants, mean amplitudes of vibration and rotational distortion constants are calculated and compared with those of earlier workers.
Synthèse de 7,8‐Dihydroquinoleinones
Authors: Maquestiau A. , van Haverbeke Y. , Vanden Eynde J. J. , De Pauw N. 
Published: September 2010

AbstractA number of 7,8‐dihydroquinolinones are prepared by cyclocondensation of aminocyclohexenone with β‐dicarbonyl precursors.The structure of the bicyclic derivatives so obtained is determinated and a reactive scheme is proposed to explain how these compounds are formed.