bluuebunny/crossref_metadata_2025 huggingface dataset:
Simultaneous determination of yttrium and several rare earths in monasite and bastnaesite by hollow cathode excitation coupled to vidicon detection ‐ A progress report
Authors: Broekaert J. A. C.
Published: September 2010

The detection limits for rare earths (R.E.) obtained when exciting samples in a hot hollow cathode (H.C.) and applying vidicon spectrum registration are compared to previously published photographic results. A hot H.C. coupled to vidicon is applied to the simultaneous determination of yttrium and several R.E. in dissolved monasite and bastnaesite samples.
Synthetic studies on rosane diterpene. Synthesis of (±)‐2β‐hydroxy‐4aβ, 8a‐dimethyl‐8‐methylene‐trans, anti, trans‐perhydrophenanthrene
Authors: Banerjee Ajoy Kumar
Published: September 2010

2β‐Benzoyloxy‐4aβ‐methyl‐8‐keto‐trans, anti, trans‐perhydrophenanthrene (Va) has been synthesised which has been subjected to angular methylation followed by Wittig reaction to synthesise the titled compound (II).
Molecular constants of some tetrahedral XY4 molecules
Authors: Mohan S.
Published: September 2010

All the five independent G.Q.V.F.F force constants in nine molecules of the tetrahedral type have been evaluated on the basis of kinetic constants of these molecules. The results appear to show the basic importance of kinetic constants in molecular dynamics. The mean amplitudes of vibration of these molecules have been calculated using the present set of force constants. The kinetic constants, force constants and the mean amplitudes evaluated here, are interesting showing the significance of the new procedure.
Analyse Aux Rayons X de la Structure D'un T. Butyl‐2 Méthyl‐3 Cyclopentane‐Diol‐1,4
Authors: Germain G. , Declercq J. P. , van Meerssche M.
Published: September 2010

Molecular configuration determined by direct methods on monoclinic crystals. P1/c. Z=4.
Structures de Deux Dimères Formés a Partir de la 1,2,4‐Triméthylimidazoline‐5‐One
Authors: van Meerssche M. , Germain G. , Declercq J. P. , Bodart‐Gilmont J.
Published: September 2010

Crystal and molecular structures are described for meso and dl dimers C12H16N4O2 isolated during the synthesis of the title imidazoline derivative. Crystal data are as follow. dl form: trigonal, R3c; a=16,815 Å, α=116,93°; Z=6. Meso form: monoclinic, P21/c; a‐14,584, b=7,992, c=13,495 Å, β=117, 28°; Z=4.
Alcaloides de Lycopodium Gnidioides et de Lycopodium Verticillatum
Authors: Nyembo L. , Kahindo N. , Braekman J. C. , Hootele C.
Published: September 2010

Besides the already known alkaloids lucidioline (I), anhydrolycodoline (II), lycoclavine (III) and selagine (IV), two new compounds have been isolated from Lycopodium gnidioides L.f.: gnidioidine (V) and lycognidine (VI). From L. verticillatum L. anhydroaposerratinine (VII) and lycoverticine (VIII) were obtained. The structures of the compounds (V) to (VIII) have been determined.
N‐Acylamino acids and peptides IV The Synthesis of N‐cinnamyl‐, N‐p.coumaryl‐ and n‐caffeyl‐glycine and ‐glycyl‐l‐phenylalanine
Authors: De Pooter H. , van Rompaey L. , van Sumere C. F.
Published: September 2010

Condensation of cinnamyl‐, O‐ethoxycarbonyl‐p. coumaryl‐ or O,O‐diethoxycarbonylcaffeyl chloride with glycine ethyl ester (or t‐butyl ester), and with A‐glycyl‐L‐phenylalanine t‐butyl ester gave acceptable yields of the completely protected intermediate N‐acyl‐esters. The latter substances were then transformed into the title compounds by removal of the blocking functions, the elimination of the O‐ethoxycarbonyl‐group being frequently more easily performed with hydrazine hydrate than with alkali.
The rotameric distribution of 5‐halomethyl groups in 1,3‐dioxanes
Authors: Borremans Frans , Anteunis Marc J.O.
Published: September 2010

The rotameric distribution in the axial and equatorial halomethyl group in the 2‐methyl‐5‐halomethyl substituted 1,3‐dioxanes is determined qualitatively and a rationale is proposed. The data indicate an attractive 1,3‐synaxial interaction between the halogen and the hydrogen atoms in α‐position to an oxygen atom.
Acide mercapto‐3 pyridine carboxylique‐2
Authors: Dereppe J. H. , Schanck A. , Declercq J. P. , Germain G. , van Meerssche M.
Published: September 2010

C6H5NO2S. Monoclinic, P21, Unit Cell: a=10.502, b=7.120, c=4.317 Å, β=96,16°, Z=2. Structure solved by direct methods shows quite planar molecules with internal S — H hydrogen bond.
Application of the floating spherical gaussian orbital (F.S.G.O.) model to the determination of photoelectron spectra of alkanes
Authors: André J. M. , Lambert‐Gérard M. E. , Lamotte C. H.
Published: September 2010

The application of the Floating Spherical Gaussian Orbital (FSGO) method to the determination of molecular photoelectron spectra of alkanes is described. Despite of its computational simplicity, the method is proved to give results in surprisingly good agreement with experiment.
Application of hollow cathode excitation coupled to vidicon detection to the simultaneous multielement determination of toxic elements in airborne dust.‐ A Unique sampling‐analysis procedure for lead and cadmium ‐
Authors: Broekaert J. A. C.
Published: September 2010

A unique method for the simultaneous determination of lead and cadmium in airborne dust samples is described. Samples are collected by drawing air through porous cup graphite electrodes and analysed by excitation in a demountable hollow cathode lamp (H.C.L.) coupled to a vidicon detector. Detection limits for lead and cadmium are determined. Some analytical results for field collected samples are communicated.
Chemical studies of marine invertebrates. XXV1. Flexibilene, an unprecedented fifteen‐membered ring diterpene hydrocarbon from the soft coral Sinularia flexibilis (Coelenterata, Octocorallia, Alcyonacea)
Authors: Hérin M. , Colin M. , Tursch B.
Published: September 2010

Flexibilene is a novel monocyclic diterpene hydrocarbon isolated from the soft coral Sinularia flexibilis. Spectroscopic analyses established its structure as 1,1',5,9,13‐pentamethyl‐Δ2,5,9,13‐cyclopentadecatetraene (II). Flexibilene is the first 15‐membered ring diterpene to be found in nature.
Stevens rearrangement and Hofmann elimination reactions of quaternary hexahydroindolium salts
Authors: Madsen J.Ø. , Lawesson S.‐O.
Published: September 2010

Treatment of N,N‐dialkylhexahydroindolium salts, 1, with t‐BuOK leads to 4,5,6,7‐tetrahydroindoles, 7, 8, and 11, via competitive Stevens rearrangement and Hofmann elimination reactions.
Synthèse de Dérivés de Benzoxazepines. II. 5‐Aryl‐2,3,4,5‐Tetrahydrobenzo[f] 1,4‐Oxazepines
Authors: Waefelaer A. D. , Pecher J. , Dubois A. , Poultier P.
Published: September 2010

Several new 5‐aryl‐2,3,4,5‐tetrahydrobenzo[f]1,4‐oxazepine derivatives (1 to 18) were prepared by reduction of the 2,3‐dihydro compounds. Adams platinium was a suitable catalyst for hydrogenation. With other catalysts, reduction of a nitro group or debenzylation may occur before the alteration of the imine function of the heterocycle. NaBH4 was suitable only in a few cases.
Une Méthode de Dérivation Directe des Équations Hartree‐Fock Non‐Restreinte
Authors: Smeyers Y. G. , Brucea A. M.
Published: September 2010

On présente une méthode d'obtention directe des équations Hartree‐Fock non‐restreinte (UHF), basée sur la minimisation de l'expression de l'énergie moyenne, sans recourir à la technique habituelle des multiplicateurs de La‐grange. La méthode fournit une expression pour les dits “multiplicateurs de Lagrange”, expression qui permet d'envisager d'autres procédés que 1'habituel pour résoudre les équations UHF.
Pulse Polarographic Determination of Trinitroglycerin in Explosives
Authors: Steeman E.
Published: September 2010

The application of pulse polarography for the qualitative and quantitative detection of the major constituent compound trinitroglycerin (TNG) and minor compounds such as trinitrotoluene (TNT), dinitrotoluene (DNT), diethylphtalate and 2‐nitrodiphenylamine in explosives has been described. Results are reproducible within 0.5 % in absolute value and 2.3 % relatively. Most of the results agree with the specifications of the manufacturer. Deviations may occur due to the interference of decomposition products or the presence of interfering minor compounds. A modification of a colorimetric method for the determination of TNG is also described.
Utilisation de la Résine de “Merrifield” en Synthèse Organique. I. Mono et Dialkylation de Dérivés D'Acides Amines
Authors: Szabo L. , Coppens E. , Clauder O. , Pecher J.
Published: September 2010

The primary amino group of two amino acids bound to the Merrifield resin was alkylated and the substrate was subsequently transesterified in acid or alkaline medium. Either an alkylamino ester or a dialkylamino ester was obtained in high yield according to the selected experimental conditions, the control of which is straightforward. The results are discussed in considering the controversy concerning the rigidity of the swollen polymeric matrix.
Synthesis of an Optically Active Triorganostannyl Ketone
Authors: Gielen Marcel , Simon Serge
Published: September 2010

Racemic p‐(cyclohexylmethyl‐l‐naphthylstannyl) acetophenone (I) is transformed into its menthydrazone which is, after four recrystallizations, reconverted to optically active (I), [α]20°436 +0.25° ± 0.05°. Several methods have been used to determine the optical purity of optically active (I) without success.
Volatile Air Oxidation Products of Hop Bitter Acids
Authors: Blot J. M. , Verzele M.
Published: September 2010

Air oxidation of hop bitter acids produces complex mixtures of volatile products, containing appreciable amounts of 2‐methyl‐3‐buten‐2‐ol (10 of table 1) and the lactone 5,5‐dimethyl‐(5H)‐2‐furanone (37 of table 1). Both have been identified in beer and have been attributed hoppy flavour. Separation and synthesis of these materials prove they have however no hoppy aroma characteristics.

Air oxidation of humulone produces C9 hydrocarbons (8 and 11 of table 1). These have been reported in hop essential oil and were then thought to be “abnormal” terpenes. Other bitter acids do not give these hydrocarbons.
Nucleophilic Substitution Reactions of Brominated Dimethyl Alkylidene Malonates
Authors: Verhé R. , De Kimpe N. , De Buyck L. , Courtheyn D. , Schamp N.
Published: September 2010

Reaction of dimethyl 2‐bromo‐2‐methylpropylidene malonate with various nucleophiles mainly afforded dimethyl cyclopropane 1,1‐dicarboxylates while treatment with amines gave substitution products.
Voies Nouvelles en Synthèse de Prostaglandins (1)
Authors: Crabbé P. , Barreiro E. , Sook Choi H. , Cruz A. , Deprès J. P. , Gagnaire G. , Greene A. E. , Meana M. C. , Padilla A. , Williams L.
Published: September 2010

The preparation of novel prostaglandin analogues from PGA2, isolated from marine corals, is outlined.

The synthesis of prostaglandins that contain a cyclobutane instead of the cyclopentane ring is described.

In addition, a detailed account of the total synthesis of prostaglandins by the tropolone route is given.
Étude De La Séparabilité De Quelques Fonctions D'Onde De L'Atome De Berylium
Authors: Constanciel R.
Published: September 2010

The method of pair density analysis is applied to very elaborate ab initio functions for the berylium atom. It is shown that these functions are separable to a high approximation even though they account for a large part of the correlation.
Glycyl Methylene Chemical Shift Non‐Equivalence in Small Peptides. Diasteriomers of Leu‐Gly‐Phe
Authors: Anteunis Marc J. , Becu Christian , Lala Anil K. , Verhegge Georges , Narayan‐Lala Krishma
Published: September 2010

Main possibilities for the origin of glycyl methylene chemical shift non‐equivalence in Gly‐containing small peptides are reviewed together with new data obtained at 300 and 360 MHz 1H‐nmr spectroscopy. An unexpected behaviour, both in glycyl methylene chemical shift non‐equivalence as in the similarity of mean shift values of these protons in the diasteriomeric tripeptides Leu‐Gly‐Phe rules out the electric field gradient contributions being of major importance. Changes in conformational features, both of the back‐bone as of the side chain rotation in function of pH are revealed, as follows from a study of coupling constants.
Solution Conformation of Lysocellin‐Na +; More Than a Simple Structural Analog of Lasalocid‐Na+
Authors: Anteunis Marc J. O.
Published: September 2010

Although the covalent structure of Lysocellin (1) differs from Lasalocid (2) at both ends of the molecule, nevertheless the atomic coordinates are such that common ligands [0θ ‐1, OH‐5, C=0‐6 and OH‐10 in 1] lie in a square planar arrangement around the trapped central metal cation. Water of crystallization was present and may serve as an additional ligand. The complete structural architecture of 1 in solution has been unraveled by 2H‐nmr spectroscopy and allows a precise description (Figure 4) and comparison with 2 as previously reported2. A hydrophilic zone at one side of the flat molecule, which could be more or less accessible for polar interactions, is formed by 0‐2, OH‐3, 0‐7, OH‐8 and OH‐10. The outside periphery is screened by a crown consisting predominently of alkyl side chains attached to the back‐bone.
Hétérocycles Organiques De L'Arsenic:V Synthése, Structure Et Stéréochimie D'Arsatranes Tetracoordinés
Authors: Maroni P. , Holeman M. , Wolf J. G.
Published: September 2010

A series of compounds (Ia to Id) derived from diethanolamines and bis(N,N dimethylamino) methyl arsane were synthetised. The coordinative bond N→ As in these molecules makes them “arsatranes”. The physicochemical results all suggest a trigonal bipyramid structure with nitrogen in the apex position. A stereochemical study of two of these compounds (Ic and Id) was carried out with static and dynamic NMR.
Preparation and Structure of Predione (1,2,3,4,5a,6,7,8,9,10a‐Decahydro‐4a, 9a‐Epoxidibenzo‐|1,4|‐Dioxin‐5a, 10a‐Diol)
Authors: Tavernier D. , Benijts F. , Verzele M.
Published: September 2010

A large scale (2 mole) preparation of the title compound by nitric acid oxidation of cyclohexanol is described (47% yield). In chloroform, an equilibrium is established between predione and a tricyclic compound, shown to be cis‐3a, 4, 5, 6, 7, 7a‐hexahydro‐spiro|1,3‐benzodioxole‐2, 1′‐cyclohexane|−2′‐keto, −3a, 7a‐diol (4). The stereochemistry of predione is discussed.
Observation De Fragmentations De Seconde Région Libre De Champ D'Un Spectromètre De Masse à Géometrie Inversée Lors Du Balayage De La Tension D'Accélération
Authors: Maquestiau A. , van Haverbeke Y. , Flammang R. , De Meyer C.
Published: September 2010

In a reversed geometry mass spectrometer first field free region fragmentations are usually detected by scanning the accelerating voltage. In some favourable instances, artifacts corresponding to second field free region processes are observed; the influence of a collision gas on their relative intensities is discussed.
Synthesis and X‐Ray Analysis of a New Representative of the Class of 3,4‐Diaza‐Trithiapentalenes
Authors: Stelander B. , Viehe H. G. , van Meerssche M. , Germain G. , Declercq J. P.
Published: September 2010

A new synthesis of 1, 3, 5‐trichloro‐2, 4‐diazapentamethinium chloride (5) results from condensation of two equivalents of phosgene iminium salt (1) and cyanamide. The same product is also obtained from three equivalents of (1) and urea. Thiolysis of (5) leads to 2, 5‐bis(dimethylamino)‐3,4 diaza‐trithiapentalene (7).
A Comparative Oxidation Study of Some Thiane Derivatives.
Authors: van Acker Lucien , Anteunis Marc J. O.
Published: September 2010

Three thianes substituted with a cis‐α', γ'‐diMe holding group and with in the ß‐ringposition of sulfur a C‐, O‐ and S‐atom respectively have been oxidized with a variety of oxidants and the isomeric distributions of the resulting mono‐sulfoxides have been analyzed by gaschromatography. The stereochemistry of these oxidations appears to be sensitive to steric constraints from ring substituents and to the electronic features of the substrate molecules.
Enamine Chemistry XVI Reactions Between Enamines and Chloral
Authors: Nolde C. , Lawesson S. ‐O.
Published: September 2010

Enamines, derived from cyclic ketones, react with chloral stereo‐selectively to give high yields of only one of the possible isomers. The reaction between the same enamines and two moles of chloral leads to formation of 1:2‐adducts (mixture of isomers) having a 1,3‐dioxane structure. Factors controlling the steric course of these reactions are discussed.
Transformation Hydrothermale De Gels Appartenant Aux Systèmes MgO‐SiO2 ‐H2O‐F ET MgO‐Al2O3–SiO2‐H2O‐F
Authors: De Vynck I.
Published: September 2010

The influence of different fluoride concentrations on the cristallisation of MgO‐SiO2‐H2O and MgO‐Al2O3‐SiO2‐H2O gels, under hydrothermal conditions was studied.

The fluoride changes the proportion Mg/Si available for reaction and has in that way a marked influence on the cristallisation of the gel observed after a definite hydrothermal treatment.
Studies in Oxadiazoles: Part VII. Synthesis And Fungicidal Activity of Some 2‐Sulfanilamido‐I,3,4‐Oxadiazoles and Their N4‐(o‐Carboxy‐Benzoyl)/Carboxyethylcarbonyl Derivatives
Authors: Singh H. , Yadav L. D. S.
Published: September 2010

Some 2‐amino‐5‐aryl‐I,3,4‐oxadiazoles have been condensed with acetylsulfanilyl chloride, and 2‐(N4‐acetylsulfanilamido)‐5‐aryl‐I,3,4‐oxadiazoles thus obtained have been hydrolysed to provide the corresponding 2‐sulfanilamido‐I,3,4‐oxadiazoles. The latter have been condensed with phthalic and succinic anhydrides to yield 2‐[N4‐(o‐carboxybenzoyl])‐ and 2‐[N4‐(carboxyethylcarbonyl) sulfanilamido]‐I,3,4‐oxadiazoles, respectively. Three of these compounds were found to possess significant fungicidal activity against A. niger and A. flavus.
Comparaison Des Valeurs Du Potentiel Normal Du Couple Cu(II)/Cu(I) Dans Les Chlorures Alcalins Fondus, Obtenus Par Spectrophotométrie D'Absorption Et Par Polarographie
Authors: Mbuyi M. B. , Duyckaerts G.
Published: September 2010

The standard oxidation potentials of Cu(II)/Cu(I) in three alkali chloride melts at 450°C have been determined by absorption spectrophotometry and by pulse polarography; the values obtained are discussed and compared with those found in the literature.
Pulse Polarographic Determination of Europium in Minerals
Authors: Steeman E. , Temmerman E. , Verbeek F.
Published: September 2010

Differential pulse polarography was used for the quantitative determination of europium in minerals and oxides of lanthanides. The reduction of europium (III) to the divalent state shows suitable polarographic characteristics in several supporting electrolytes, for which differences in sensitivity have been tabulated. Procedures have been described for the direct determination of europium (III) in lanthanide‐oxides down to 0.2 ppm using 0.5 g samples. Europium was also determined in the mineral bastnaesite after a previous separation of the lanthanides by oxalate precipitation.
Coefficient De Diffusion De Cu(I) Déterminé Par Différentes Méthodes Dans Les Chlorures Alcalins Fondus a 450°C
Authors: Mbuyi M. B. , Duyckaerts G.
Published: September 2010

The interdiffusion coefficient of Cu(I) in three melts, LiCl‐KCl (58–42% mol.) LiCl‐CsCl (55–45% mol.), LiCl‐KCl (70–30% mol.) at 450°C for the two first and 457%dGC for the last one has been measured by different electrochemical methods: chronopotentiometry, cyclic voltammetry, pulse polarography and chronoamperometry, Chronopotentiometry gives systematically lower values for the diffusion coefficient. No significant influence of the nature of the solvent on the diffusion coefficient was observed.
Complexes of Tertiary Thioamides: Part III: Complexes of Dimethyl‐Thioacetamide with Co(II), Pd(II), Zn(II), Cd(II) and Hg(II)
Authors: Aarts A. J. , Desseyn H. O. , Herman M. A.
Published: September 2010

Complexes of dimethyl‐thioacetamide (DMTA or L) with Co(II), Pd(II), Zn(II), Cd(II) and Hq(II) have been prepared and investigated by conductivity measurements, and by electronic, infrared and Raman spectroscopy. mL2Cl2 (M=Co, Zn, Hg), ML2I2 (M=Co, Zn, Cd, Hg) and [ML4] (ClO4)2 (M=Co, Zn, Cd) complexes are shown to be tetrahedral. CdLcl2 is polymeric, but a definite structure could not be assigned. Pd(II) forms planar cis‐PdL2Cl2, trans‐PdL2I2 and [PdL4] (ClO4)2. DMTA acts in all cases as a monodentate sulphur donor ligand.
On the Classification of Pairwise Relations Between Isomeric Structures
Authors: Mislow Kurt
Published: September 2010

The conventional classification of pairwise relations between structures of equal atomic composition gives primacy to the notion of constitution. It is asserted that a complete and edge‐weighted molecular graph is a more faithful representation of bonding relationships than a constitutional graph. A scheme is proposed, rooted in geometric rather than topological qualities of the model, which is well attuned to the distinguishing characteristics of isomeric pairs, and in which pairwise relations are classified as isometric (homomers, enantiomers) and anisometric (diastereomers, constitutional isomers). This classification is extended to topic relationships.
Kinetic study of the oxidation of 1,4‐dihydropyridines with chloranil
Authors: Dommisse R. A. , Lepoivre J. A. , Alderweireldt F. C.
Published: September 2010

The reaction kinetics of the redox system chloranil‐1, 4‐dihydropyridine (of the Hantzsch‐ester type) is monitored by U. V.‐spectroscopy. A possible reaction mechanism is discussed. Evidence for an ion‐pair formation in a purely second‐order reaction is given. Some catalytic effects are described. From the thermodynamic parameters it is clearly demonstrated that the electronic effects of the substituents are of an utmost importance. All reactions have large negative ΔS≠‐values.

The reduction of several functional groups with 1, 4‐dihydropyridines have recently been intensively studied especially as test‐case reactions for the coenzymes NADH and NADPH. Up to now only a limited amount of data on reaction velocities has been published (1). In the present paper the oxidation of several Hantzsch‐esters (see table 1) is described with emphasis on reaction kinetics and structural effects. Chloranil is choosen as a suitable oxidans for practical purposes. A reaction mechanism is given for the well known reaction (fig. 1).
Photobromination of Halogenobenzenes: Ipso‐Attack or Not?
Authors: Gouverneur P. , Soumillion J. P.
Published: September 2010

In a preliminary communication (2) we reported the results obtained in the photo‐ and ionic brominations of halogeno‐ and dihalogenobenzenes. A recent paper(3) suggested that our results “are suggestive of ipso‐attack, a mechanism that has not previously been advocated for free‐radical reactions”. The purpose of this communication is to point out that the proofs of such a mechanism are not borne out by our data. This does not imply that ipso‐attack has to be rejected but it needs other data to be proved and remains only a simple although attractive hypothesis.
Potentiometric Study of Hydrogen Chloride in 2‐Methoxyethanol Water Mixtures
Authors: Merken G. V. , Thun Harry P. , Verbeek F.
Published: September 2010

The standard emf of the cell Pt;H2/HCl(solvent)/AgCl, Ag |1| is reported for the mixtures 80, 90, 95 and 98 wt‐% 2‐methoxyethanol and respectively 20, 10, May and February wt‐% water. The correlation of the present and previous results enables to present a structure for solutions of hydrogen chloride in mixtures of 2‐methoxyethanol and water.
Rearrangement of α‐Chloro‐Isobutyraldimines: Synthesis of 2‐Imidazolidinones
Authors: De Kimpe Norbert , Verhe Roland , De Buyck Laurent , Schamp Niceas
Published: September 2010

Treatment of N‐1‐(2‐chloro‐2‐methylpropylidene) amines with potassium cyanate in methanol afforded 1‐substituted‐4‐methoxy‐5,5‐dimethyl‐2‐imidazolidinones, which were easily converted into the non‐methoxylated derivatives, i.e. 1‐substituted‐5,5‐dimethyl‐2‐imidazolidinones, by reaction with lithium aluminium hydride in diethyl ether. The structure was confirmed by independent synthesis of the latter heterocycles and their isomeric structure (4,4‐dimethyl derivative). The formation of the 2‐imidazolidinones, starting from α‐chloroaldimines and potassium cyanate, involved a rearrangement of the imino‐nitrogen atom, which was explained by an aziridine intermediate.
Réactions De Deshydrodimérisation Radicalaire. 4. Action Du Peroxyde De Di‐t.Butyle Sur Les Alkylbenzenes: Diastéréomerie Des Dérivés Bibenzyles (
Authors: Gouverneur P. J. L. , Mulangala J. Mukinayi
Published: September 2010

Meso and racemic bibenzyles are formed by action of di‐t.butyl‐peroxide on alkylbenzenes (ethyl‐, n.propyl‐, n.butyl‐, n.pentyl‐, n.hexyl‐, isobutyl‐, sec.butyl‐, isopentylbenzene) and on para‐X substituted ethylbenzenes (X = F, Cl, Br, CH3, CH3O). The nature of the products is confirmed by decomposition of the corresponding azo compounds and their configuration is determined unambiguously by X‐rays analysis. The differences between meso and racemic dimers are analyzed with regard to their melting temperatures, chromatographic retention times, IR,1H‐NMR and13C‐NMR spectroscopies. The diastereoisomerism of the azo‐bis‐alpha phenylalkanes is also discussed.
Self‐Association of Pyridine in Water
Authors: Huyskens Pierre L. , Smets Roger S. , Mas Dany H.
Published: September 2010

The distribution coefficient P ≡ Fo/Fw of pyridine between cyclohexane and water decreases when the formal concentration Fw in the aqueous phase increases. This can be explained by the self‐association of the pyridine molecules in water. The data are consistent with a Mecke‐Kempter model of self‐association, the constant kMw for the successive additions being of the order of 0.38 ± 0.05 l mole−1. The forces responsible for this self‐association seem to be mainly π … π interactions between the π‐electrons of the aromatic rings of two neighbouring molecules.
Acid Dissociation Constants of Some Thiooxamides and Dithiooxamides
Authors: Aarts A. J. , Herman M. A.
Published: September 2010

The acid dissociation constants of dithiooxamide, methyl‐ and N, N‐dimethyl‐dithiooxamide, No‐methyl‐ and No, No‐dimethylthiooxamide were determined spectrophotometrically. The pKa values (at I = 1) of thioacetamide, thiobenzamide, potassium thiooxamidate and N, N′ ‐dimethyldithiooxamide were determined for comparison. Also H‐D exchange rates were measured for some compounds. The results are discussed taking into account inductive effects, conjugation and hydrogen bonding.
Influence De La Concentration Sur Le Déclin Des Penta‐1, 3‐Dienes Photoexcités à 228.8 nm: Mise En Évidence D'Un Excimère
Authors: Vanderlinden P. , Boué S.
Published: September 2010

In contrast to the results obtained at 253.7 nm, the photolysis of penta‐1,3‐dienes at 228.8 nm in solution displays a strong remarkable concentration dependence.

Hence ϕcis → trans increases and ϕtrans → cis decreases with an increasing diene concentration and both figures reach a plateau at ∼1M. A kinetic treatment is presented, which involves dynamic and static quenching (according to Perrin's law) and accounts for experimental data; the scheme consistently suggests that an excimer comes into play in this system.
Stereochemical Studies on Medicinal Agents. 24 Correlation of the Solid‐State Conformations of 4‐Phenylpiperidine Analgetic With the Torsional Relationship Between the Phenyl Group and Piperidine Ring in Solution, a Circular Dichroism Study
Authors: Poupaert Jacques H. , Portoghese Philip S.
Published: September 2010

A CD study of 8 representatives of 4‐phenylpiperidine analgetics is presented to correlate their solid‐state conformations with their chiroptical properties in solution. In addition to the benzenoid 1Lb fingerprint, the studied compounds exhibit two waves: the former band around 230‐223 nm is assigned to a 1La transition; the origin of the latter band is not determined. A quadrant rule is tentatively proposed to explain the sign of the 1La Cotton effect.
Nouveaux Derivés De L‚Aryl‐1 Pyridothiazine Et De L‚Arylamino‐8 Pyridothiazolium
Authors: Jamoulle J. C. , Lapière C. L.
Published: September 2010

The synthesis of new derivatives of pyridothiazine and pyridothiazolium is reported. The study of these compounds by RM1H spectrometry has made possible their identification and differentiation.
Synthèse Et Isomérie De Thiométhylpyrazoles
Authors: Maquestiau A. , van Haverbeke Y. , Vanovervelt J.‐C.
Published: September 2010

The shortly performed thermal conversion of 1, 2‐dimethylpyrazolin‐5‐thiones leads to 1‐methyl‐3‐methylthiopyrazoles. The isomerization of these compounds into mixtures of 3‐methylthio and 5‐methylthiopyrazoles is observed after several months at room temperature or more rapidly after prolonged heating. 1‐methyl‐3‐methylthio‐ and 5‐methylthiopyrazoles appear thus respectively as the kinetic and thermodynamic products of the reaction which proceeds at least mainly via an intermolecular mechanism.

The thermal intermolecular conversion of 1‐phenyl‐2‐methylpyrazolin‐5‐thiones leads exclusively to 1‐phenyl‐5‐methylthiopyrazoles as described in the literature.
Use of Meldrum's Acids in the Semi‐Synthesis of α‐Carboxylated Penicillins and Cephalosporins
Authors: Crooy P. , De Neys R. , Eliaers J. , Liveyns R. , Simonet G. , Vandevelde J.
Published: September 2010

α‐Carboxylated penicillins (i.e. Carbenicillin, Ticarcillin) and cephalosporins are obtained in two steps from the appropriate Meldrum's acid.
Étude structurale de cations générés par ionisation chimique de C‐aminotriazoles.
Authors: Maquestiau A. , van Haverbeke Y. , Flammang R. , De Meyer C.
Published: September 2010

Mass‐analyzed ion kinetic energy spectra of chemically ionized aminotriazoles were used to obtain structural features of protonated molecular ions, differenciation of isomers giving nearly identical c.i. mass spectra and relative basicities of tautomers in the gas phase. Unimolecular fragmentations suggest that the “ethylated dimers” are formed by ethylation with [C2H5]+ followed by solvation of this collision complex with a second molecule.
Chemical studies of marine invertebrates. XXXI(1). Crassolide, a highly oxygenated diterpene from the soft coral lobophytum crassum. (Coelenterata, Octocorallia, Alcyonacea).
Authors: Tursch B. , Braekman J. C. , Daloze D. , Dedeurwaerder H. , Karlsson R.
Published: September 2010

The complete structure determination of crassolide, a new cembranolide diterpene isolated from the soft coral Lobophytum crassum, is described.
Potentiometric studies of some bivalent metal ion complexes of N‐p‐tolyl‐p‐methoxybenzohydroxamic acid (p‐T‐p‐MBHA)
Authors: Agrawal Y. K.
Published: September 2010

The complexes of N‐p‐tolyl‐p‐methoxybenzo hydroxamic acid with Cu(II), Zn(II), Ni(II) and Mn(II) are studied by potentiometric titration in the mixtures 50, 60 and 70 vol % dioxane and respectively 50, 40 and 30 vol % water at 25 and 35°C · 0.1°C. The thermodynamic ionisation constants of p‐T‐p‐MBHA are reported in the mixtures 10, 20, 30, 40, 45, 50, 60 and 70 vol % dioxane and respectively 90, 80, 70, 60, 55, 50, 40 and 30 vol % water. The order of stability of the complexes and the effect of solvent on the formation constant are discussed.
Complexes of tertiary thioamides. part IV. complexes of N‐dimethylcyanothioformamide, N‐dimethylethylthiooxamidate and NS, NS‐dimethylthiooxamide with pd(II) and Hg(II).
Authors: Aarts A. J. , Desseyn H. O. , Herman M. A.
Published: September 2010

Complexes of N‐dimethylcyanothioformamide (DMCTF), N‐dimethylethylthiooxamidate (DMETO) and NS, NS‐dimethylthiooxamide (SDMTO) with Pd(II) and Hg(II) have been prepared, characterized by metal analyses and conductivity measurements, and investigated by vibrational and electronic spectroscopy. The ligands all act as monodentate sulphur donors. With Pd(II) square planar compounds are formed: cis‐Pd(DMCTF)2Cl2, trans‐Pd(DMETO)2Cl2, (LSDMTO), and PdL4(C104)2 (LDMCTF, DMETO, DSMTO). DMCTF and SDMTO form mononuclear tetrahedral compounds (HgL2Cl2) with Hg(II), while DMETO forms a polynuclear compound ([HgL2Cl2]n) with an indefinite structure.
Étude de la conformation et de la tautomérie des azidoazoles par dipolemétrie
Authors: Fayet J. P. , Vertut M. C. , Mauret P. , Claramunt R. M. , Elguero J. , Alcalde E.
Published: September 2010

The experimental and vectorially calculated electric dipole moments of six azidoazoles (imidazole, benzimidazole, pyrazole, indazole, s‐triazole and v‐triazole) have been compared and one preferred conformation of the azido group with respect to the heterocyclic ring has been proposed.
Deoxypolynucleotides‐purification of trinucleotide blocks by solvent extraction
Authors: Kohli Vipin , Kumar Ashok
Published: September 2010

Two protected trinucleotide blocks MMTr‐TpTpT and d‐MMTr‐ABzpTpGi‐Bu were synthesized using phosphodiester approach. The purification of these blocks was achieved in satisfactory yields simply by extraction into a binary organic solvent.
Thermal lactonization of brominated alkylidenemalonates: Synthesis of 2‐buten‐4‐olides
Authors: Verhé Roland , De Kimpe Norbert , De Buyck Laurent , Courtheyn Dirk , Schamp Niceas
Published: September 2010

Heating of dialkyl 2‐bromoalkylidenemalonates in boiling xylene resulted in lactonization with formation of 2‐alkoxycarbonyl‐2‐buten‐4‐olides. Bromination of dimethyl 2‐phenylpropylidenemalonate with NBS in CCI4 gave the corresponding butenolide. However, heating of the 2‐bromocyclohexylidenemalonate only afforded the dehydrobromination product.
Electrocatalytic reduction of butanone I. oscillating accumulation of intermediates
Authors: Feyaerts K. , De Hemptinne X.
Published: September 2010

Butanone is reduced to butane and butanol‐2 on Pt in H2SO4 electrolyte. Oscillating accumulation of intermediates in the butane reaction is observed. Their chemical nature is discussed: a chemisorbed butyl radical and interstitial hydrogen atoms.
Nitrogen‐14 indor spectra of some 2‐substituted pyrimidines
Authors: McFarlane William , Turner Christopher J.
Published: September 2010

14N chemical shifts have been measured for eleven 2‐substituted pyrimidines using a 1H ‐ {14N} double resonance technique in conjunction with spectral accumulation. Correlations are noted between the 14N chemical shifts and calculated π‐electron densities at nitrogen.
Trapping of thiaziridinimines with N‐sulfinylamines
Authors: L'abbé Gerrit , van Asch Alex , Declercq Jean Paul , Germain Gabriel , van Meerssche Maurice
Published: September 2010

The reactions of 4‐alkyl‐5‐arylsulfonylimino‐1,2,3,4‐thiatriazolines with N‐sulfinylamines at 60‐70° yield 3‐oxo‐5‐arylsulfonylimino‐1,34,2,4‐dithiadiazolidines 4 which are smoothly converted by hydrolysis into S‐aminoisothio‐ureas 5. In contrast, the acetyl derivative 4g hydrolyzes into thiadiazoline 7. Structure assignment of the products was based on spectral and combustion analyses, chemical reactions, and, in the case of 4e, on an X‐ray structure determination.
Cyclopentanones Stereochemistry of the Lithium‐Liquid Ammonia Reduction of 2, 3‐Dialkyl‐5‐Hydroxy‐2‐Cyclopentenones
Authors: Hanselaer René , Samson Marc , Vandewalle Maurits
Published: September 2010

The stereochemistry of the lithium‐liquid ammonia reduction of 2, 3‐dimethyl‐5‐hydroxy‐2‐cyclopentenone (1) and 3‐t.butyl‐2‐methyl‐5‐hydroxy‐2‐cyclopentenone (2) is studied in function of a set of proton donors. A high degree of stereoselectivity is observed as practically only two (predominantly one isomer) out of the eight diastereoisomeric 3, 4‐dialkyl‐1, 2‐cyclopentane diols 3 or 4 are formed.
The Crystal Structure of Monoclinic Copper(II)‐hydrogen‐(1)‐Malate Dihydrate
Authors: van Havere W. , Lenstra A. T. H.
Published: September 2010

Copper(II)‐hydrogen‐(1)‐malate crystallises in the monoclinic space group P1. Characteristics of the unit cell are: a=7.589 Å, b=8.158 Å, c=10.210 Å, γ=87.28° and Z=2, with chemical composition Cu(C4O5H5)2.2H2O.

The Cu2+ ion is coordinated by six oxygen atoms, all originating from the hydrogen malate ions. Two Cu‐O distances are elongated due to the Jahn‐Teller effect.

The two crystallographically independent malate ions have significantly different geometries.
Solution Conformation of Lonomycin Free Acid and Lonomycin Sodium Salt. An 1H‐NMR Study
Authors: Rodios Nestor A. , Anteunis Marc J. O.
Published: September 2010

The conformations and relative configurations of the antibiotic Lonomycin free acid and its sodium salt have been revealed in a high resolution 1H‐nmr study in non polar solvents. The basic chair forms of the three pyranoïd rings have been confirmed although deformations are noted for ring B, heavily substituted and possessing syndiaxial strain. The fixed rotarmeric states around the acyclic fragments do not change by passing from the free to the complexed form. The extracted data suggest that the molecule possesses a rigid frame work forming a pseudocyclic backbone with a haid‐to‐tail buttoning shut by a hydrogen bond.
Métallation Des Halogènures D'Aryle Par le Tributylstannyllithium Dans le HMPT
Authors: Quintard Jean‐Paul , Hauvette‐Frey Sabine , Pereyre Michel
Published: September 2010

Tributylstannyllithium was prepared in the absence of metallic lithium by cleavage of hexabutylditin with butyllithium in HMPA. It reacts with bromotoluenes in a completely regiospecific way. However parachloro and fluorotoluenes give mixtures of tin substituted compounds whose compositions strongly depend on the experimental conditions and on the nature of the halogen. All data are in agreement with a competition between anionic and radical mechanisms. Product analysis was realised by means of gas chromatography, NMR Spectroscopy (13C and 119Sn) and mass‐spectrometry.
Studies on organophosphorus compounds XXVI. Synthesis and 13C NMR spectra of N,N‐dialkyl thioamides
Authors: Fritz H. , Hug P. , Sauter H. , Winkler T. , Lawesson S. ‐O. , Pedersen B. S. , Scheibye S. , Logemann E.
Published: September 2010

By a new thiation reagent,1, 4, 11 the dimer of p‐methoxyphenylthionophosphine sulfide, 3, a series of thioamides have been prepared in almost quantitative yields from the corresponding amides, Carbon‐13 NMR spectra of tertiary thioamides of formic, acetic, trifluoroacetic, propionic and butyric acids have been completely assigned with the aid of extensive double resonance and shift reagent experiments and the data obtained have been compared with those of the analogous amides.8 Also a linear relation between the 13C chemical shifts of CS of the thioamides and CO of the corresponding amides has been found by a least square linear regression analysis: δ(CS) = 1.60° (CO)−72.3.
Imine chemistry I. A new route to pyrroles and related compounds from imines and 2‐chloroacrylonitrile
Authors: Olesen S. O. , Madsen J. Ø. , Lawesson S. ‐O.
Published: September 2010

The Michael addition of 2‐chloroacrylonitrile to imines (potential enamines) and the subsequent elimination of HCN produced pyrroles and condensed pyrroles.
The raman spectrum of pyridines in charge transfer complexes with bromine
Authors: Maes G.
Published: September 2010

Raman spectra of several pyridine derivatives (substituent = CH3‐, tC4H9‐, Cl‐, Br‐, I‐) complexed with bromine are studied in CH2Cl2 and in CH3CN. Marked changes in frequency, intensity and degree of depolarization of the Raman bands of pyridines are observed. These spectral perturbations seem to depend on the position of the substituent and are further discussed in terms of the charge transfer theory.
AN 1H‐NMR study of the polyether antibiotic etheromycin‐Na+ (CP‐38 295‐Na+).
Authors: Anteunis Marc J. O. , Rodios Nestor A.
Published: September 2010

The structure and the solute conformation in nonpolar solvents of the title compound have been revealed by high resolution 1H‐nmr spectroscopy. The ionophore possesses the typical pseudocyclic conformation of the polyether antibiotics by which the head and tail is held together through H‐bond binding, sequestering the cation from the lipophilic surrounding. The extra sugar like moiety (ring G,) seems not to participate in cation coordination.
N‐Acylamino acids and peptides VI. A Simple synthesis of N‐acylglycines of the benzoyl‐ and cinnamyl type
Authors: Brussel W. Van , van Sumere C. F.
Published: September 2010

A very simple and fast method for the synthesis of N‐acylamino acids and peptides from the benzoyl‐ and cinnamyl type is described. The method is based on the use of N‐hydroxysuccinimide as reagent (active ester method).

The characteristics and chromatographic parameters of some new benzoylglycines are given.
The Determination of the Rare Earth Elements in Rocks by Spark Source Mass Spectrometry
Authors: van Puymbroeck J. , Gijbels R.
Published: September 2010

The determination of the rare earth elements in rocks by high frequency spark source mass spectrometry, using photoplate detection, was investigated.

Several standard rocks (BCR‐1, JB‐1, JG‐1, NIM‐G, NIM‐N) were analysed by the “direct” method, and after three different selected enrichment procedures: peroxide fusion and successive hydroxide and fluoride precipitations; acid digestion and cation exchange chromatography; acid digestion and mixed‐solvent anion exchange chromatography. These preconcentration methods are discussed and the results obtained are compared with each other.

A mixed‐solvent anion exchange procedure permits to determine all rare earth elements with a precision of 10%.
Ionisation Constants of N‐Arylhydroxamic Acids
Authors: Agrawal Yadvendra K.
Published: September 2010

The ionisation constants of N‐0‐tolyl‐p‐substituted benzohydroxamic acids have been determined in 10‐70% v/v dioxane‐water media at 25 and 35±0.1°C. The pKa's in aqueous media (at 10% dioxane) have been obtained using the method of extrapolation and least squares. The pKa values vary linearly with the mole fraction of dioxane. These constants are tested for the applicability of the Hammett equation.
A Potentiometric Determination of the Self‐Association Constants of Some L‐Amino Acids in Aqueous Solution
Authors: Vliegen J. , van Poucke L. C.
Published: September 2010

Because of its biochemical interest the self‐association behaviour of six natural occuring L‐amino acids was studied by potentiometry in aqueous solutions of 3M KCl.

The investigated amino acids were glycine, L‐alanine, L‐proline, L‐hydroxyproline, L‐serine and L‐threonine.

The experimental results are obtained in two different ways: in a first treatment of the experimental data only association, in a second treatment association and variation of the Eo of the cell are taken into account.

The following conclusions can be made: in both treatments only dimeric species are found of which those of L‐serine are the most stable, for all amino‐acids H3L2+ is detected and seems to be more stable than the other dimeric species.
Contribution to the Complex‐Formation of Diphenylcarbazone with cations. Complexes of Zinc, Nickel, and Cobalt
Authors: Peeters O. M. , Blaton N. M. , Willems G. J. , De Ranter C. J.
Published: September 2010

The complexes of diphenylcarbazone with zinc, nickel and cobalt are studied spectrophotometrically in a 50 volume percent aqueous acetone medium. The wavelength of maximal absorbance is situated between 520‐525 nm. The three complexes show a 1:2 stoichiometry as derived independently from the method of continuous variation and the slope‐ratio method. The molar absorptivities amount to 70000‐77500 1 mo1−1 cm−1 and the conditional constants have an order of magnitude of 107.
Photogalvanic Cells. 5. Oxidation Photocurrents of Triphenylmethane Dyes at the SnO2 Bubbling Gas Electrode
Authors: Kirsch‐De Mesmaeker A. , Kanicki J. , Leempoel P. , Nasielski J.
Published: September 2010

The photoelectrochemistry of Crystal Violet, Methyl Violet and Malachite Green in the presence of hydroquinone is examined at the SnO2 bubbling gas electrode. For the first two dyes, the Stern‐Volmer constants of the process responsible for the supersensitization, determined by the previously described (1) electrochemical method, could correspond to the quenching either of the oxidized dye or of the excited triplet state.

An interesting new feature emerges from the study of the Malachite Green‐hydroquinone system: two species seem to be involved in the supersensitization process having rather different lifetimes, and thus quenched in different hydroquinone concentration ranges.
Synthesis and Nuclear Magnetic Resonance Spectra of Mixed and Asymmetric Benzyltin Compounds
Authors: De Poorter Bertha , Gielen Marcel
Published: September 2010

The synthesis of a series of mixed and asymmetric benzyltin compounds is described. The nuclear magnetic resonance spectra are discussed.
Studies for an Alternative Synthesis of 11‐Desoxy‐10‐Hydroxy Prostaglandin Analogs
Authors: Bracke Pieter‐Paul , Verzele Frank , Wyffels Wilfried , Vandewalle Maurits
Published: September 2010

3‐(Carboxymethyl)‐1,2,4‐cyclopentanetrione prepared from laevulinic acid and diethyl oxalate is an excellent starting material for a high yield and stereo‐selective synthesis of 11‐desoxy‐10‐hydroxy‐prostaglandin F2α. On the other hand 3‐(2'‐benzyloxyethyl)‐1,2,4‐cyclopentanetrione a precursor, also in theory suitable for 12‐methyl substituted analogs, gives less satisfactory results because of lack of stereochemical control.
Physical and Chemical Relaxations in Ethylene Following CO2‐Laser Irradiation Time of Flight Observations
Authors: De Keuster D. , De Hemptinne X.
Published: September 2010

Phenomena 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

The 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

An 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

Collision 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

Silver 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.