bluuebunny/crossref_metadata_2025_split huggingface dataset:
NMR experiments on acetals. Part 48 the prins‐reaction on cyclic (poly) olefins and the characterization of resulting 1, 3‐dioxanes
Authors: Coryn M. , Anteunis Marc 
Published: September 2010

AbstractWe have investigated the Prins‐reaction of formaldehyde on several cyclic (poly) olefins. The nature (100 and 300 MHz NMR studies; table II) and yields of the resulting 1,3‐dioxanic compounds have been carefully assessed (Table I). The results indicate that most previous claims are to be taken only as general rules, with many exceptions however. Thus, a wide variety in stereospecificity of the primary reaction must be accepted, leading to syn and anti (diaxial) and even trans (diequatorial) addition routes. It seems acceptable that only protonated polymeric formaldehyde oligomers may rationalize such a broad spectrum of possibilities.
Application de la Spectrométrie de Masse en Serie Hétérocyclique. Système N‐Phenyl‐3,6‐Dihydro‐2H‐1,2‐Oxazine
Authors: Maquestiau A. , van Haverbeke Y. , Flammang R. , De Meyer C. 
Published: September 2010

AbstractThe behaviour of some N‐pheny 1‐3, 6‐dihydro‐2H‐ 1, 2‐oxazines is examined under electron impact. These compounds undergo essentially two competitive reactions : 1) a thermal elimination of water which leads to the corresponding N‐phenylpyrrole, as it is proved by the comparison of the metastable ratios evaluated on the oxazine‐H2O⌉·+fragment ions and on the N‐phenylpyrrole itself; 2) a retro Diels Alder fragmentation giving the nitrosobenzene and the butadienyl system.
The Separation and purification of ribofuranose derivates by countercurrent distribution
Authors: Vanbroeckhoven J. H. , Dierckens J. J. , Alderweireldt F. C. 
Published: September 2010

AbstractThis paper reports the purification and separation of several tri‐O‐benzoyl‐D‐ribofuranose derivates (2,3,4,5) by counter current distribution. A new product 1‐O‐Ethyl‐2,3,5‐tri‐benzoyl‐β‐D‐ribofuranose (5) has been isolated. The purity of all these products was tested by T. L. C. The N. M. R. spectra are discussed.
The anodic behaviour of lead in acid sulphate solutions. Influence of copper and cobalt ions
Authors: Ravindran Kanechamkandy , Heerman L. , van Simaeys L. 
Published: September 2010

AbstractThe anodic behaviour of lead has been studied at Pb/PbSO4 and PbSO4/PbO2 potentials in sulphuric acid solutions in presence of copper and cobalt ions by galvanostatic and potentiokinetic methods. The presence of cobalt ions has been observed to exert a beneficial effect in reducing the anodic dissolution of lead. Anodic corrosion products, in function of cations in solution, have been analyzed by X‐ ray diffraction technique. A schematic model of passivated lead anode in presence of cobalt ions has been proposed.
Réactions Chimiques de Composes de Neptunium Dans L'Eutectique LiCl‐KCl Fondu
Authors: Lysy R. , Landresse G. , Duyckaerts G. 
Published: September 2010

AbstractVisible and near IR absorption spectrophotometry provides a good method for the study of chemical reactions in fused salts. It has been applied in the case of neptunium, whose chemical properties in a LiCl‐KCl eutectic between 400° and 600°C have been investigated.
Oxidation products of hop bitter acids. Part VIII. Six‐membered ring products from the oxidation of colupulone.
Authors: van Den Bossche R. , Anteunis M. , Borremans F. , Verzele M. 
Published: September 2010

AbstractAir oxidation of colupulone in iso‐octane solution produces a complex mixture, separation of which by counter‐current distribution with the two phase system iso‐octane/buffer pH 6.40 gives the cyclohexa‐2,4,6‐trione epoxide (III).
Calcul De La Densité Des États Électroniques Des Polymères Stéréoréguliers. I. Procédé Par Échantillonnage
Authors: Delhalle J. 
Published: September 2010

AbstractOn décrit un programme de calcul de la densité des états électroniques des polymères stéréoréguliers par une technique d'échantillonnage. La somme équidistante est plus efficace que le procédé de Monte Carlo. Le programme est appliqué à l'étude du polyène régulier infini.
Conformation De L'Acide 3‐(Aminocarboxymethyl) 2‐Pyrrolidone 5‐Carboxylique
Authors: Welter A. , Marlier M. , Dardenne G. 
Published: September 2010

AbstractA new naturally occuring amino acid, isolated from the seeds of Pentaclethra Macrophylle was found to be l the 3‐(Aminocarboxymethyl) 2‐Pyrrolidone 5‐Carboxylic acid.The conformation of this amino acid in solution is determined from N. M. R. spectra and compared with the conformation in solid state.The absolute configuration is established through a comparative study of the results obtained by O. R. D., C.D. spectroscopy and X‐ray diffraction.
Spectroscopic Intensity and Dipole Moment Study on Malononitriles
Authors: van Haverbeke L. , Herman M. A. 
Published: September 2010

AbstractThe Infrared and Raman intensities of the 2250 cm−1 band in malononitrile and some of its derivatives has been determined.The dipole moments of these compounds have been measured in benzene solutions. The results are compared mutually and are discussed in terms of the inductive and electron delocalisation effects of the substituents.
Hydrolyse de l'acide 3(R)‐ [1′ (S) ‐ Aminocarboxymethyl] 2‐Pyrrolidone 5(S)‐Carboxylique
Authors: Welter A. , Jaddt J. , Dardenne G. , Marlier M. , Casimir J. 
Published: September 2010

AbstractDuring the acid hydrolysis of the lactam linkage of the 3(R) ‐ [1′ (S)‐aminocarboxymethyl] 2‐pyrrolidone 5(S)‐carboxylic acid, three aminoacids were isolated. Their structure and absolute configuration are determinated.Tha acid hydrolysis is found to proceed to an equilibrium between an open chain tricarboxylic di‐α aminoacid, a lactam aminoacid and two γ lactam amino acids as shown in fig. 3.
Mise en Evidence des Tautomeres Enethioliques des Mercaptopyridines en Spectrometrie de Masse
Authors: Maquestiau A. , van Haverbeke Y. , De Meyer C. , Katritzky A. R. , Frank J. 
Published: September 2010

AbstractEquimolar mixtures of HS‐Py (Py=pyridine) and DS‐Py show primary isotope effects upon metastable ions for the CS loss. This is valid for the 3‐ and 4‐ isomers and this observation implies that thiol forms exist in the gaz phase. This result is also confirmed by the analogy in isotope effects between molecular ions of H(D)S‐Py and the daughter ones, generated by a four centered elimination of C2H4 and C2D4 respectively from Py‐S‐C2H5 and Py‐S‐C2D5. The insensibility of the CS loss following deuteriation of the 2‐isomer does not exclude the presence of the thiol tautomer: this phenomenon is explained by and ortho effect exerted by the pyridinic nitrogen.
Stereospecific Synthesis of Z and E C16ω‐Iodo Δ9 Fatty Acids from Natural Aleuritic Acid
Authors: Hevesi L. , Hontoy J. , Krief A. , Lubochinsky J. , Lubochinsky B. 
Published: September 2010

AbstractLong chain fatty acids containing iodine were found to be convenient label compounds for the studies of membrane incorporation. We describe the stereospecific synthesis of Z and E C16ω‐iodo Δ9 fatty acids and esters starting from commercially available aleuritic acid. Chemical and spectroscopic proofs of stereospecificity are given for one of the compounds.
1H‐NMR Study of the Di‐Glucopyranoses in D2O
Authors: De Bruyn A. , Anteunis M. , Verhegge G. 
Published: September 2010

AbstractWe report the analysis at 300 MHz of the 1H‐n.m.r. spectra of all the α‐D‐, and β‐D‐glucopyranosyl‐ (1 → x) ‐D‐glucopyranoses (x = 1, 2, 3, 4 and 6) in D2O (CHART 1, 1‐9). Chemical shifts were compared with those of α‐D‐, and β‐D‐glucopyranose. Using homo‐INDOR experiments and applying increment rules it was possible to identify all the resonances of the individual protons and to assess the position of the glycosidic linkage. All protons situated on, or vicinal to carbons involved in this linkage, are shifted downfield. Exceptions occur for the glycosidic proton belonging to the non‐reducing parts.
A New Synthetic Approach to 4‐Hydroxybenzofuran and 5‐Hydroxychroman Derivatives
Authors: Verhé R. , Schamp N. , De Buyck L. , De Kimpe N. , Sadones M. 
Published: September 2010

Abstract4‐Hydroxybenzofuran and 5‐hydroxychroman compounds have been synthesized by heating 2‐chloro‐2‐alkenyl‐1,3‐cyclohexanediones, prepared by chlorination of 2‐alkenyl‐1,3‐cyclohexanediones with N‐chlorosuccinimide, in dimethylformamide ‐25% hydrogen chloride at 140°C.
Revised Synthesis of 3‐O‐Cinnamyl‐, 3‐O‐p.Coumaryl‐and 3‐O‐Isoferulyl‐D‐(‐)‐Quinic Acid
Authors: De Pooter H. , De Brucker J. , van Sumere C. F. 
Published: September 2010

AbstractThe experimental circumstances for the synthesis of 3‐O‐acyl‐D‐(‐)‐quinic acids by the procedure of Haslam et al are improved, and applied to the preparation of the title compounds. The substances are obtained in overall yields of respectively 36%, 25% and 20%, comparing favourably with the reported results of respectively 8%, 7% and 6.5%.
The Variation of Lattice Parameters with Composition in Solid Solutions of Hydroxylapatite and Fluorapatite
Authors: Schaeken H. G. , Verbeeck R. M. H. , Driessens F. C. M. , Thun H. P. 
Published: September 2010

AbstractSolid solutions of hydroxylapatite (OHA) and fluorapatite (FA) were prepared from CaCO3, CaHPO4.2H2O and CaF2 by solid‐state reaction at 1000°C in a stream of nitrogen which was saturated with water vapor at 0°C. Determinations of the lattice parameters were carried out by step scanning of certain X‐ray reflections. It was found that the value of the lattice parameter a varied linearly with the fluoride content. No segregation into two apatite phases was observed, when solid solutions were heated at 250°C for 300 hours. The consequences of this study for the behaviour of these solid solutions in contact with aqueous solutions are discussed. Thereby, attention is focussed on the caries‐preventive action of fluoride ions.
Metal Clusters in Catalysis III. — Clusters as Models for Chemisorption Processes and Heterogeneous Catalysis
Authors: Muetterties E. L. 
Published: September 2010

AbstractAn analysis of the intrinsic structural, stereochemical and thermodynamic features of metal surfaces vis a vis those of discrete metal clusters suggests that the clusters are attractive models of metal surfaces for chemisorption and heterogeneous catalysis. Chemical and catalytic properties of the two classes are compared.
Prototropie des oxadiazoline‐1,2,4 ones‐5 et thiones‐5
Authors: van Haverbeke Y. , Maquestiau A. , Muller R. N. , Stamanne M. L. 
Published: September 2010

Abstract3‐phenyl‐1,2,4‐oxadiazolin‐5‐one and 3‐p‐chlorophenyl‐1,2,4‐oxadiazolin‐5‐one exist in the N2‐H conjugated form as evidenced by analysis of spectroscopic results (NMR, UV and IR). In the same manner, the data lead to assign the “thione” form to 3‐phenyl‐1,2,4‐oxadiazolin‐5‐thione.
Ionic association and dielectric relaxation of alkylammonium salts in non polar solvents
Authors: Cachet H. , Lestrade J. C. 
Published: September 2010

AbstractComplex dielectric permittivity measurements of tri and tetra‐alkylammonium salts in C6H6 and CCl4 solutions have been performed in the 8 ‐ 35000 MHz frequency range. Relaxation spectra, corrected for conductivity losses, are nearly half‐circles in the case of tri‐n‐butylammonium picrate while they exhibit a much more complex shape in the case of tetra‐n‐butylammonium salts. For the incompletely substituted salt, the hydrogen bond favours the formation of molecule‐like ion‐pairs and the main relaxation process is the diffusional rotation of such ion‐pairs. For concentrated solutions of tetra‐butylammonium salts, the state of the solute can be pictured as large, non‐rigid aggregates without a permanent dipole moment. The polarization arises from an instantaneous asymmetrical distribution in the positions of the ions under an applied electric field. The complicated shape of the spectra is accounted for by assuming this asymmetry to vanish through the diffusional translation of the ions.
1H‐NMR spectra of pyrazino [2,3‐f] quinoxalines and 5,6‐diaminoquinoxalines
Authors: Nasielski‐Hinkens R. , Benedek‐Vamos M. , Hautain Y. , Nasielski J. 
Published: September 2010

AbstractThe NMR spectra of 2,3‐ and 2,3,8,9‐substituted pyrazino [2,3‐f] quinoxalines are described. Unambiguous deuteriation of 5,6‐diaminoquinoxalines allowed the assignment of the 7‐ and β‐protons; changes in solvent induce inversions in the peak positions.
Étude Par RMN du 13C Du Benzothiazole et de Ses Dérivés Nitrés
Authors: Elguero J. , Faure R. , Vincent E.‐J. , Lazaro R. 
Published: September 2010

AbstractThe C13 assignement of the six carbon atoms of benzothiazol was obtained by comparison with the results for thiazol and from the effect of the nitro‐group in positions 4, 5, 6 and 7 and the effect of deuterium in position 6.
Optical Stability of Organometallic Compounds With a Tin‐Germanium Bond
Authors: Gielen Marcel , Simon Serge 
Published: September 2010

Abstract(Dimethylphenylstannyl)methyl‐1‐naphthyl‐phenylgermanium (I) and methylneophylphenyl (triphenylgermyl)tin (II) are configurationally stable even in the presence of strong nucleophiles. Optically active isopropylmethylphenyl (triphenylgermyl)tin (III) has been synthesized by asymmetric induction and shows that hexaorganodimetal compounds with a tin‐germanium bond are optically stable.The synthesis of functionally substituted organometallic compounds with a Sn‐Ge bond, like 5‐[(phenyldimethylstannyl) diphenylgermyl]‐2‐pentanone (VI), is described. An attempted resolution of a cyclohexylmethylphenyl (triorganogermyl)tin compound is also given.
The Influence of White Radiation on Diffraction Data in X‐Ray Analysis. A Comparative Study of Monochromator Versus Filter Data
Authors: Petit G. , Lenstra A. T. H. 
Published: September 2010

AbstractUsing a Mo‐tube two data sets were collected from an ammonium hydrogen malate crystal. The first set was collected using the traditional Zr‐filter. The second one was obtained using a graphite monochromator.The differences in the corresponding intensities are due to the presence of white radiation in the set of filter data. The refined temperature parameters from both data sets are not exactly comparable. As far as hydrogen positions are concerned differences up to 0.1 Å were found changing from the first to the second data set.In addition an empirical correction is proposed, which enables one to eliminate the white radiation from the usual filter data.
Infrared Spectra and Structure Of Carbanions ‐ XIV. Isomeric Carbanionic Adducts of Some Substituted Cyano‐Polyenes
Authors: Juchnovski I. N. , Binev I. G. 
Published: September 2010

AbstractIt was found on the basis of IR spectroscopic data, that the nucleophilic CH3O− attack to substituted cyano‐butadienes PhCHCHCHC (X = CN, COOEt, C6H4NO2‐p) and 1‐cyano‐1‐ethoxycarbonyl‐6‐phenyl‐hexatriene takes place at the β‐carbon atom. The 1,2‐carbanionic adducts, thus formed, isomerise spontaneously into the thermodynamically more stable 1, 4‐adducts of the butadiene derivatives and 1,6‐adduct of the studied hexatriene.
Preparation of Cyclopropanes by Reduction With an Alkaline Metal in Liquid Ammonia and Long Range Phenomena in the 1H‐Nmr Spectra of 1, 3‐Dioxane‐Spirocyclopropanic Derivatives
Authors: Breugelmans Micheline , Anteunis Marc J. O. 
Published: September 2010

AbstractA newly proposed2 modification of an intra Würtz‐coupling procedure has been tested for its preparative value. The 1H‐nmr spectral data of two 1, 3‐dioxane‐spirocyclopropane derivatives (1 and 2) are discussed and the characteristic long range couplings are revealed.
13C NMR Spectra of Electrically Neutral Organic Lewis Acids
Authors: Haslinger E. , Wolschann P. 
Published: September 2010

AbstractThe13C NMR spectra of a number of derivatives of the cyclic acylal of malonic acid and of dimethylbarbituric acid are reported. These compounds contain an electron poor polarized carbon ‐ carbon double bond and act therefore, as Lewis acids.
Solution Conformation of Nigericin Free Acid and Nigericin‐Sodium Salt
Authors: Rodios Nestor A. , Anteunis Marc J. O. 
Published: September 2010

AbstractHigh resolution 1H‐nmr spectral data enable us to confirm the close resemblance between the three‐dimensional structure of nigericin free acid and its Na+‐complex. The circular form with a buttoning shut by hydrogen bonding between the head carboxylate and the tertiary alcohol function of the last six‐membered ring is a further typical example how the folded quasi cyclic backbone thus formed enables in these polyetherin ionophores the sequestering of a cation. Further details allow the description of some departure of the ideal chair form in rings A and B. No extra water molecule seems to be present in the free acid state. Whereas the secondary alcohol OH‐10 in the free acid form may participate to the head‐to‐tail connection, this seems not to be the case in the salt. A comparative discussion of the head‐to‐tail buttoning shut pattern in monensin, dianemycin and nigericin is given.
Photoisomerization in α, β‐Unsaturated Carboxylic Acids
Authors: Biot Jean‐Marie , De Keukeleire Denis , Verzele Maurice 
Published: September 2010

Abstract4‐Methyl‐2‐(E)‐pentenoic acid and 5‐methyl‐2‐(E)‐hexenoic acid are quantitatively transformed into the corresponding β,γ‐unsaturated isomers by irradiation at 254 nm.The synthesis of 5,5‐dimethyl‐2(5H)‐furanone via photochemically induced lactonization of 4‐hydroxy‐4‐methyl‐2‐(E)‐pentenoic acid is described.
Conformations Privilégiées de Dérivés des Bithiophenes: Étude par Spectroscopie d'Absorption Électronique
Authors: Meunier P. , Coustale M. , Arriau J. 
Published: September 2010

AbstractAn experimental and theoretical study of the UV absorption spectra of bithiophens indicates that non planar conformations are predominant in vapour phase and non polar solutions. The existence of steric strain within dibramobithiophens induces an increase of the twist angle. An evaluation of this angle is carried out for each compound.
Studies on organophosphorus compounds XXI. the dimer of p‐methoxyphenylthionophosphine sulfide as thiation reagent. a new route to thiocarboxamides
Authors: Scheibye S. , Pedersen B. S. , Lawesson S.‐O. 
Published: September 2010

AbstractThe thiation properties of the dimer of p‐methoxyphenylthionophosphine sulfide, 1, has been investigated by performing reactions with a representative series of aliphatic and aromatic primary, secondary, and tertiary carboxamides in the temperature range 80‐100 °C using HMPA as solvent. This new method seems to be superior to all others as in most cases quantitative yields are found. Salicylanilide, when reacted with 1, in HMPA, yields salicylthioanilide and a new type of phosphorus heterocycle, 3, whose structure has been determined by NMR‐and X‐ray analyses. 13C NMR data are tabulated for a series of thioamide carbons.
Studies on organophosphorus compounds XXIV. the formation of disulfides from sulfoxides
Authors: Rasmussen J. B. , Jørgensen K. A. , Lawesson S.‐O. 
Published: September 2010

AbstractThe reaction of DMSO with the dimer of p‐methoxyphenylthionophosphine sulfide, 1, produces dimethyl disulfide and causes partly deoxygenation of DMSO to give dimethyl sulfide. P4S10 and DMSO give dimethyl disulfide in lower yield, a result not observed in recent reports. 5, 6 The cyclic sulfoxide, tetrahydrothiophene sulfoxide, 2, also reacted with 1 to give the cyclic disulfide, 1,2‐dithiane, 3.
Synthesis of Alkylidenetriazenes (1,2,3‐Triazabutadienes). X‐Ray Crystal Structure of 1‐Methylthio‐3‐(α‐Morpholino) Benzylidenetriazene
Authors: L'abbé Gerrit , Willocx André , Declercq Jean‐Paul , Germain Gabriel , van Meerssche Maurice 
Published: September 2010

AbstractThe clean and high yield reactions of sodium azide with quaternary salts of N, N‐disubstituted thioamides furnish alkylidenetriazenes 3 (1, 2, 3‐triazabutadienes) instead of the previously reported2) dihydrothia(SIV) triazoles 2.
Study of Inorganic Salts by Static and Dynamic Secondary Ion Mass Spectrometry
Authors: Marien J. , De Pauw E. 
Published: September 2010

AbstractSecondary ion mass spectrometry (SIMS) has been applied to the study of superficial layers of solid inorganic salts such as sulfate and sulfite of sodium. The positive and negative SIMS spectra of sulfate and sulfite show qualitatively no difference. Nevertheless, the relative heights of the peaks m/e ▪ 149 and m/e = 165 which are present in both spectra enable a distinction between Na2SO3 and Na2SO4. According as the solid is sulfite or sulfate, the intensity of the (Na3SO3)+ is higher or lower than the intensity of (Na3SO4)+. The positive SIMS spectra can be interpreted according to a model where ejected neighbouring atoms or clusters recombine depending upon their chemical affinity and where molecular species (Na2SO3), (Na2SO4), are cationized by sodium. Reduction of the salts into metallic sodium has also been observed.In this work, we also demonstrate that the superficial oxidation of sulfite into sulfate can be monitored by SIMS.
The Molecular Structure of 3,5‐Diethoxycarbonyl‐2, 6‐Dimethyl‐1,4‐Dihydropyridine. An X‐Ray Study
Authors: Lenstra A. T. H. , Petit G. H. , Dommisse R. A. , Alderweireldt F. C. 
Published: September 2010

AbstractThe title compound crystallizes in P1, with a = 6.999 Å, b = 7.491 Å, c = 12.711 Å, α = 91.1 °, β = 106.5 °, y = 90.1 ° and Z = 2. The structure was solved by rotation and translation search procedures and refined to a final R‐value of 0.053. Excluding the hydrogen atoms, the molecule is planar. The compound is crystallized in such a way that a close packed layer structure is achieved.The influence of the packing of the molecules on the reduction of chloranil by 3,5‐diethoxycarbonyl‐2,6‐dimethyl‐1,4‐dihydropyridine in solid state solutions is discussed.
Studies of Australian Soft Corals. XVII . The Isolation and Properties of Lemnalactone, 7‐EPI‐Lemnalactone and their Derivatives. A Correction of Several Literature Assignments, Supported by X‐Ray Diffraction
Authors: Ahond A. , Chiaroni A. , Coll J. C. , Fourneron J. D. , Riche C. , Braekman J. C. , Daloze D. , Tursch B. , Dunstan P. J. 
Published: September 2010

AbstractThe isolation and full evidence for the structure of lemnalactone (1) and 7‐epi‐lemnalactone (2) are reported. Spectroscopic evidence which led to this reinvestigation is presented, and the structural conclusions therefrom are confirmed by a single crystal X‐ray study of a derivative of 2. The previous structure for lemnalactone (as 2) has led to several erroneous stereochemical assignments in the literature and these are here corrected.