bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stereochemical Behavior of Silicon Five‐Membered Rings: A Comparison of the Nucleophilic Displacements of Intracyclic Si‐o and Si‐S Bonds
Authors: Corriu R. J. P. , Fernandez J. M. , Guearin C. , Kpoton A. 
Published: September 2010

AbstractA synthetic route to the new optically active 2‐(1‐naphthyl)‐2‐phenyl‐1‐thia‐2‐silacyclopentane is described.A comparison of the optically active oxa‐ and thiasilacyclopentanes shows that the most electronegative leaving group, i.e., the oxygen atom, leads preferentially to retention. The less electronegative leaving group, i.e., the sulfur atom, reacts mainly with inversion.The results are in disagreement with a mechanism governed by the apicophilicity of the substituents attached at silicon. In contrast, they are consistent which a mechanism controlled by two factors, i.e., the ability of the leaving group to be displaced by a nucleophile and the electronic character of the attacking reagent.
1H and 13C NMR investigations on alkyllead (iv) compounds
Authors: De Vos D. , van Beelen D. C. , Wolters J. 
Published: September 2010

AbstractWithin the theoretical framework of the Fermi contact interaction trends in the magnitude 207Pb−1H and 207Pb−13C coupling constants are explained on the basis of s‐electron density at the nucleus and hybridization in the Pb‐C bond. The influence of the introduction of polar or bulky substituents is discussed. The importance of the values of exchange integrals with respect to the observed orders |1J207 Pb‐13C| >|3J207 Pb‐13C| >|2J207 Pb‐13C| and |3J207 Pb‐1H| >|2J207 Pb‐1H| is accentuated.
Ir spectroscopy of aryllead tris (trifluoroacetates)
Authors: De Vos D. , Wolters J. 
Published: September 2010

AbstractIR data of the trifluoroacetate group in p‐ClC6H4Pb (OOCCF3)3 are presented and compared with those of the compounds C6H5HgOOCCF3 and C6H5Tl (OOCCF3)2
Insertion and cooxidation of nickel‐bonded methallyl and norbornene ligands
Authors: Chiusoli G. P. , Dradi E. , Salerno G. , Campari G. 
Published: September 2010

AbstractTreatment of a methallylnickel complex, containing norbornene as ligand, with oxygen leads to one or two double bond insertions, followed by oxidation to alcohols and ketone.
Mechanistic aspects of the nickel‐catalyzed addition reaction of alkenyl‐zirconium reagents to cyclopropyl ketones
Authors: Loots Melanie J. , Dayrit Fabian M. , Schwartz Jeffrey 
Published: September 2010

AbstractNickel‐catalyzed addition of alkenylzirconium species to cyclopropyl ketones proceeds by an electron transfer mechanism. One‐electron reduction of the substrate leads to a ketyl which may either couple to give the 1, 2‐addition product or undergo a second one‐electron reduction, followed by rearrangement and coupling to give a β‐methyl, β‐alkenyl ketone. This rearrangement is postulated to occur via β‐hydride elimination and reinsertion in an organonickel intermediate. The ratio of 1, 2‐adduct to ring‐opened product formed is dependent on the concentration of nickel(I) catalyst present and suggests that two Ni(I) species, used successively, are required to open the three‐membered ring.
Détermination par diffraction de rayons x de la structure de: I ‐ bis (ethoxycarbonyl‐1 oxocyclopéntyl‐2)‐1, 2 éthane C18H26O6 II ‐ bis(ethoxycarbonyl‐1 oxocyclopéntyl‐2)‐1, 3 propane C19H28O6 III ‐ bis (ethoxycarbonyl‐1 oxocyclopéntyl‐2)‐1, 6 hexane C22H34O6
Authors: Tinant B. , Arte E. , Feneau‐Dupont J. , Declercq J. P. , Germain G. , van Meerssche M. 
Published: September 2010

AbstractThe crystal and molecular structure of the title compounds have been established from X‐ray diffractometer data. All possess molecular symmetry: I and III with centrosymmetrical molecules are in the meso configuration; II exhibits non crystallographic twofold axial symmetry. Molecular dimensions and conformations are very similar in the three compounds.
Étude théorique de l'isomérisation Z‐E des oximes C‐substituées1
Authors: Leroy Georges , Nguyen Minh‐Tho , Sana Michel , Villaveces José‐Luis 
Published: September 2010

AbstractDans ce travail, nous avons étudié les isomérisations s cis‐ strans et Z‐E de l'hydroxy‐formaldoxime et de l'azido‐formaldoxime. Tous nos calculs ont été effectués en utilisant la méthode LCAO‐SCF‐MO de Roothaan. La base minimale STO‐3G, avec ou sans interaction de configurations, et la base étendue 4‐31G du groupe de Pople ont été employées.Au total, nous avons montré que le mécanisme d'isomérisation dépend fortement de l'effet de substituants et les calculs nous permettent de rationaliser certains faits expérimentaux.
Synthesis and reactivity of polychlorocyclopentanones
Authors: De Buyck L. , De Kimpe N. , Verhé R. , Courtheyn D. , Schamp N. 
Published: September 2010

AbstractSelective chlorination methods were elaborated for the conversion of cyclopentanone into 2, 2, 5, 5‐tetrachloro‐, 2, 2, 3, 5, 5‐pentachloro‐ and 2, 2, 3, 3, 5, 5‐hexachlorocyclopentanone. Dimethylformamide‐hydrogen chloride mixtures served as catalysts for enolization and for dehydrochlorination to chlorinated cyclopentenones.The reactivity of the polychlorocyclopentanones was tested towards zinc (in acetic acid, methanol or acetone) and towards bases in protic solvents. A number of chlorinated cyclopentenones, substitution products and open chain compounds (Grob elimination) were obtained in good yields.
Diterpenes acycliques de cystoseiracées (phéophycées) de la côte méditerranéenne
Authors: Combaut Georges , Francisco Christian , Piovetti Louis , Gonzales Emmanuel , Teste Jean , Codomier Louis 
Published: September 2010

AbstractA set of mediterranean brown algae belonging to Cystoseira family is analysed by a G. L. C. and I. R. method. Easy determination of diterpenic compounds is presented. Among all the samples analysed, the only one Cystoseira elegans contains eleganolone, epoxy eleganolone and elegandiol as the atlantic Bifurcaria bifurcata.
Novel metabolites from some predator‐prey pairs1
Authors: Cimino G. , De Stefano S. , De Rosa S. , Sodano G. , Villani G. 
Published: September 2010

AbstractThe isolation of known and novel metabolites from several predator‐prey pairs is reported. The usefulness of secondary metabolites as tracers to detect predation is also discussed.Many species of nudibranchs are closely associated with their food species, which include sponges, bryozoans and coelenterates, and are often so closely associated that they easily fit the criteria for a symbiotic association.The nudibranch associations have a high potential2 as models for the study of basic biological problems such as the chemorecognition and chemotaxis, the settling and metamorphosis of veligers, the defence mechanisms. The chemistry of these biological problems is poorly understood, with the exception of few reports3 related to the third point, namely the isolation of toxic or antifeedant substances from both preys and predators.We have undertaken a study of several predator‐prey pairs with the intention, at the present time, of the isolation and structural elucidation of the organic natural products accumulated by the predators during the diet because some of these compounds may have a number of the biological properties listed above.In addition we investigated the use of the secondary metabolites as a tracer to detect predator‐prey pairs.
Mycosporine aminoacids and related compounds from the eggs of fishes
Authors: Chioccara F. , Delia Gala A. , De Rosa M. , Novellino E. , Prota G. 
Published: September 2010

AbstractA survey of the distribution of mycosporines in marine organisms has shown that these compounds, previously found only in a few species, are almost ubiquitary among invertebrates and occur also in fishes, mainly in ripe eggs. These were found to contain, in addition to known members of the series, two related metabolites which were isolated and formulated as the enolised β‐diketones 4 and 5, the latter corresponding to the postulated precursor of the mycosporine chromophoric system.
Dissociation Constants of Acetic Acid and Protonated Tris(Hydroxymethyl)‐Aminomethane in 80 mass% 2‐Methoxyethanol/20 Mass % Water in the Range 10 to 50°
Authors: Shanbhag P. M. , Bates Roger C. 
Published: September 2010

AbstractElectromotive‐force measurements of cells without transference have been used to determine the thermodynamic dissociation constants of acetic acid and protonated Tris (hydroxymethyl)aminomethane (Tris.H+) in the mixed solvent 80 mass% 2‐methoxyethanol/20 mass% water from 10 to 50°. Hydrogen gas electrodes and silver‐silver chloride electrodes were used. Thermodynamic constants for the dissociation process were derived. The enthalpy of dissociation of Tris.H+ was also determined by titration calorimetry and found to be in acceptable agreement with the value obtained from the emf measurements. Allowance for association of the ions of the salts used altered the calculated pK values by about 0.03 unit (acetic acid) and 0.06 unit (Tris.H+).
Rapid Extraction and Spectrophotometric Determination of Tantalum With N‐P‐Chlorophenylbenzohydroxamic Acid
Authors: Agrawal Y. K. , Patel S. A. 
Published: September 2010

AbstractA rapid and sensitive method for the extraction and spectrophotometric determination of tantalum in presence of niobium with N‐p‐chlorophenylbenzohydroxamic acid has been described. The tantalum‐N‐p‐chlorophenylbenzohydroxamic acid (Ta‐p‐Cl‐BHA) complex is extractable into toluene or benzene in HCl media. The addition of ammonium thiocyanate and malachite green (MG) increases the molar absorption coefficients of the complexes 7.8 × 103 and 4.0 × 1041 mol−1 cm−1 respectively.
Tautomerism of Some Aminomethylphenols in Aqueous Solution
Authors: Martinek H. , Wolschann P. 
Published: September 2010

AbstractThe tautomerism of several aminomethyl‐phenols and‐naphthols in aqueous solution is studied, using electron absorption spectroscopy. From the UV‐VIS‐spectra at different pH‐values both pK‐values can be calculated, together with the proton transfer equilibrium constant KPT, At neutral pH the aminomethyl‐phenols and‐naphthols exist mainly as zwitter ions without intramolecular hydrogen bond. Log KPT follows a linear relation to ApKa.
Synthesis, 1H‐and 13C‐NMR Spectra of 2‐Tropanone Derivatives. The “6‐Endo” or “6‐Exo”‐8‐Methyl or Phenyl‐2‐Oxo‐8‐Azabicyclo of 3,2,1]‐Oct‐3‐Ene‐6‐Carbonitrile and 3,4‐Dihydrogenated Analogues
Authors: Lepoivre J. A. , Dommisse R. A. , Esmans E. L. , van Luppen J. J. , Merckx E. M. , Alderweireldt F. C. 
Published: September 2010

AbstractThe 1,3‐dipolar addition reaction of acrylonitrile to the betaine 1‐phenyl or methyl‐3‐oxidopyridinium is not so highly regioselective as generally assumed. New regioisomers are isolated. Their structures are proven by mass spectroscopy and proton‐and carbon‐NMR spectroscopy. Some 3,4dihydroderivatives are also prepared.
Reactions of 2‐(Tert‐Butylimino)‐3‐Methyl‐4‐Tosylimino‐1,3‐Thiazetidine
Authors: L'abbé Gerrit , Sorgeloos Dominique , Toppet Suzanne , King Geoffrey S. D. , Meervelt Luc Van 
Published: September 2010

AbstractThis paper describes the reactivity of the title bis(imino)thiazetidine in terms of three reactivity centers of the molecule; C2, C4 and C=NTs. Reactions have been carried out with nucleophilic reagents (NaOMe, NaSEt, KCN and malonic ester/DMSO/NaH), hydrazoic acid and electron‐rich olefins (enamines and ynamines), giving rise to products 2‐10. The two products, 9‐and 10, obtained in equal amounts from 1 and N,N‐diethylaminopropyne have been subjected to a detailed analysis by spectral methods and the structure of one of them (10) has been confirmed by the determination of its crystal structure.
Enamine Chemistry, Part XXI. N‐and/or C‐substitution (alkylation, acylation) of ethyl 3‐amino‐2‐butenoate. the preparation of 2‐substituted 4‐methyl‐1,3‐thiazine‐6‐thiones
Authors: Shabana R. , Rasmussen J. B. , Lawesson S.‐O. 
Published: September 2010

AbstractAlkylation of ethyl 3‐amino‐2‐butenoate, 1, with methyl iodide, ethyl iodide, and benzyl bromide gave both C‐ and N‐alkylated products (contrary to earlier findings) the ratio of which was determined by GLC. Methylation of 1 was studied under different conditions (solvent, reaction time, and temperature). Also the sodium salt of 1 was reacted with methyl iodide and gave both C‐ and N‐methylated products. Compound 1 reacted with acyl chlorides RCOC1 (RCH3 (a), CH(CH3) (b), C(CH3)3 (c), C6H6 (d), ClCH2 (e)) giving both N‐acylated products 6 (Z) and 7 (E), and C‐acylated products 8 and 8'. Compounds 6 and/or 7 reacted with 2, 4‐bis (4‐methoxyphenyl)‐1,3,2,4‐dithiadiphosphetane‐2,4‐disulfide, 5, giving N‐thioacylated ethyl 3‐amino‐2‐butenoate, 9, and 2‐substituted 1,3‐thiazine‐6‐thiones, 11 (main product). A similar reaction of 8a with 5 gave ethyl 3‐amino‐2‐thioacetyl‐2‐butenoate, 13. The 13C NMR data for the compounds 6, 7, 8, 11, 13, and to some extent 9 are presented.
Synthesis of symmetrical 1,6‐dihetero‐6aλ4‐thia‐3,4‐diazapentalenes from 5‐amino‐1,2,3,4‐thiatriazole
Authors: L'abbé Gerrit , Vermeulen Guido 
Published: September 2010

Abstract1,6‐Dioxa‐6aλ4‐thia‐3,4‐diazapentalenes 7 and 1,3,4,6‐tetraaza‐6aλ4‐thiapentalenes 15, two new classes of compounds with single bond‐no bond resonance, have been prepared by reaction of 5‐amino‐1,2,3,4‐thiatriazole 4 with acyl chlorides and imidoyl chlorides. In the latter case, the salts of 5‐imino‐Δ3‐1,2,4‐thiadiazolines 12 were first isolated and subsequently reacted with a second equivalent of imidoyl chloride. This also led to the synthesis of unsymmetrically substituted 1,3,4,6‐tetraaza‐6aλ4‐thiapentalenes. In the presence of bases, the salts 12 decompose via the isolable free bases 13 into N‐cyanoamidines 14 and sulfur. Treatment of the dioxathiapentalenes 7 with P4S10, or direct thiobenzoylation of 4 gave the 3,4‐diaza‐1,6aλ4‐trithiapentalenes 9.
Configurational Stability of Methylneophylphenyltin 1‐(R)‐Phenyl‐2‐(5)‐Dimethylaminopropoxide
Authors: Gielen Marcel , Eynde Ivan Vanden 
Published: September 2010

AbstractThe title compound, (PhMe2CCH2)PhMeSn‐O‐CHPhCHMeNMe2 is configurationally stable within the NMR time scale and does not undergo any fast intermolecular exchange of alkoxy groups.
Surface Tension of Freshly Formed Surfaces of Surfactant Solutions
Authors: Rillaerts E. , van Havenbergh J. , Joos P. 
Published: September 2010

AbstractA method is described to obtain the dynamic surface tension at an expanding interface. This method consists by receeding a meniscus inside a capillary, the surface at the meniscus is continuously renewed. A simple approximation is given for the dilatation. Experimental results are considered by applying the theory of Van Voorst‐vader. Good agreement between theory and experiment is achieved.
Problèmes relatifs a la détermination de la constante d'acidité de l'acide hypochloreux dans les saumures de NaCl
Authors: De Meyer M. , Levert J. M. 
Published: September 2010

AbstractThis paper studies the equilibrium HOCl
equation image
in NaCl brines and the variation of the apparent constant (ka) with ionic strength and temperature. Several reactions (decomposition, chloride formation and loss of Cl(I)) that remove the equilibrium are also examined. The brine acidity is experimentally determined and compared to the concept of pH.
The Correlation Between the Polarographic and Structural Parameters of Alizarin and its Substituents
Authors: Qureshi G. Ali 
Published: September 2010

AbstractThe correlation between the half‐wave potentials and Hammett substitution constants of 8 substituents of 1,2 dihyroxy anthraquinone (Alizarin) are worked out. These substituents are reduced in one step on the DME showing the similar degree of reversibility fulfilling the Hammett substitution relationship.The nonlinearity obtained by the 5‐sulphonated substituents of Alizarin and Alizarinfluorine blue is attributed to their adsorption nature on ME at the measured pH.
Radioimmunoassay of 11α, 15‐Dihydroxy‐9‐Keto‐Prosta‐5, 13‐Dienoic Acid (Prostaglandin e2) and 9α, 11α, 15‐Trihydroxyprosta‐5, 13‐dienoic acid (prostaglandin f2α) in human plasma
Authors: Lijnen P. J. , Verschueren L. J. , Amery A. K. 
Published: September 2010

AbstractA radioimmunoassay of prostagland in E2, (11α, 15‐dihydroxy‐9‐keto‐prosta‐5, 13‐dienoic acid; PGE2) and prostagland in F2α (9α, 11α, 15‐trihydroxy‐prosta‐5, 13‐dienoic acid; PGF2α) is described after an extraction‐chromatographic separation procedure of the plasma samples. The recovery of the extraction procedure averaged respectively 98 and 97.5% while the mean recovery after extraction and chromatography was 69.8% and 80.8%.The intra‐assay variation, checked by multiple analysis of a plasma pool, averaged 7.65% for PGE2 and 5.50% for PGF2α. The inter‐assay variation investigated by measuring the PGE2 and PGF2α concentration in different plasma samples on two occasions, averaged 7.3% for PGE2 and 6.9% for PGF2α.The prostagland in E2 and F2α concentration increased gradually by delaying the centrifugation of the blood samples after withdrawal, probably due to release by blood platelets. Addition of a prostagland in synthesis inhibitor such as indomethacin prevented the in vitro prostaglandin synthesis as reflected by the lower (p<0.001) plasma values for PGE2 and PGF2α compared to the values obtained without indomethacin.
Coordinative Role of Alkali Cations in Organic Reactions. VI. Molecular Transformation of Benzil to Benzilic Acid
Authors: Poonia Narinder S. , Porwal Prafulla K. , Sen Swagata 
Published: September 2010

AbstractStudies on the rearrangement of benzil (1) to benzilic acid (2) in the presence of caustic alkalis (M+OH−) reveal that the transformation is triggered by 1‐M+ coordination and is propagated by a nucleophilic attack of OH− on the M+‐complexed 1. Solid 1‐M+OH− complexes can be isolated from CHCl3‐EtOH (1:1) medium which can be transformed to M+‐benzilate on refluxing. Conductometric studies reveal 1‐M+ coordination in EtOH‐water (transformation medium) while UV spectrophotometric studies reveal that the presence of a Lewis acid is a prerequisite for the 1 to 2 transformation to take place. A modified mechanism for the transformation is proposed.
A short and stereoselective entry into the 2‐substituted eudesmane series
Authors: Audenhove Martine Van , Keukeleire Denis De , Vandewalle Maurits 
Published: September 2010

AbstractThe photocycloaddition reaction of (‐)‐piperitone(2') and 1, 2‐bis (trimethylsiloxy) cyclobutene (1) occurs with complete stereoselectivity. Face subsequent transformation leads to the cis‐2, 5‐decalanedione, which is a suitable intermediate for the 2‐substituted eudesmane skeleton.
The Classification of Iron Meteorites. A Reappraisal of Existing Classification
Authors: Massart D. L. , Kaufman L. , Coomans D. , Eabensen K. H. 
Published: September 2010

AbstractA new non hierarchical clustering procedure is used to evaluate an existing classification of iron meteorites. It is shown that the classification obtained resembles the existing classification to a large degree. This confirms the consistency of both the clustering method and the existing classification. The principal disagreement between the existing classification and the clustering concerns the so‐called anomalous meteorites. The reason for this disagreement is discussed.
Neutron Activation Analysis of the Trace Element Molybdenum in Urine of Healthy Persons
Authors: Cornelis R. , Versieck J. , Desmet A. , Mees L. , Vanballenberghe L. , Gent Rijksuniversiteit 
Published: September 2010

AbstractNeutron activation of Mo in urine was performed by radiochemical separation, both via the 101Mo (T1/2 14.6 min) and via the 99Mo (T1/2 66.2 h)‐99mTc (6.02 h). The urinary excretion of Mo of 9 healthy individuals ranged from 11.1 up to 88.0 μg. day−1. The variation of the Mo‐excretion in the course of the day was studied as well.
The Determination of Boron, Carbon and Nitrogen in Zircaloy by Charged Particle Activation Analysis
Authors: Mortier R. , Strijckmans K. , Vandecasteele C. 
Published: September 2010

AbstractCharged particle activation analysis is used for the determination of boron, carbon and nitrogen in zircaloy. Carbon can be determined instrumentally using the 12C (d,n) 13N reaction. For the determination of boron and nitrogen the 10B (d, n) 11C and the 14N (α, αn) 13N reactions are used. 11C is separated as 11Co2 formed by dissolution of the sample in an oxidizing solution. Carbondioxide is trapped in sodiumhydroxyde. 13N is separated as 13NH3 which is trapped in 10 ml of 0.2 M hydrochloric acid. The yield of the chemical separations is determined experimentally. Concentrations of 0.163, 113.4 and 36.8 μg g−1 are obtained for boron, carbon and nitrogen respectively.
Influence of Photoplate Evaluation Parameters in Spark‐Source mass Spectrometric Analysis
Authors: Verbueken A. , van Grieken R. 
Published: September 2010

AbstractIn view of optimising the multi‐element spark‐source mass spectrometric analysis of biological material by photoplate detection, the effect of changing some important parameters in the densitometry, linearisation procedure and further data evaluation has been investigated. In the used procedure, the relative exposure values for the different stages on the photoplate are derived from the overall experimental relative blackening data rather than from coulometer readings. This approach is especially attractive when the simple Seidel linearization method is applied.The influence of changing the maximum transmittance setting for continuous background correction appeared not to be critically important in practice. The setting of boundaries of a linear working range of the photoplate characteristic curve and its influence on the final concentration value was studied in detail. A significant difference was found, especially in trace element analysis, between the results obtained by presuming intuitively a routine dynamic range and by using a carefully established range. A comparison was also made with the more laborious Hull linearization procedure. The importance of the assumed linear range on the analytical data quality has to be emphasized.
Determination of the Main, Minor and Trace Elements in Lead/Tin‐Based Solder by Atomic Absorption Spectrophotometry
Authors: Carleer R. , François J.‐P. , van Poucke L. C. 
Published: September 2010

AbstractA procedure is described for the determination of tin, lead, bismuth, copper, iron, silver, cadmium and zinc in Sn‐Pb alloy, composed of ca. 50% Sn, 47% Pb, and 3% Bi, by means of atomic absorption spectrophotometry. The sample is dissolved in aqua regia. Tin and lead are determined against standard solutions in which the Sn/Pb ratio is approximately the same as in the alloy. The relative precision, with respect to gravimetric determinations, is ca. 1.5%. For the bismuth, copper, iron, silver, cadmium and zinc determinations the standard addition method has been used.
Contribution a L'étude électrochimique de dérivés de L'acide mercapto‐2 pyridine carboxylique‐5
Authors: Lejeune R. , Vandenbalck J. L. , Patriarche G. J. , Lapière C. L. 
Published: September 2010

Abstract5‐methoxycarbonyl‐1‐methyl‐2‐methylthio‐pyridinium iodide and 5‐carboxyl‐methyl‐2‐methylthio‐pyridinium iodide have been studied by recent polarographic and voltammetric technics.The results obtained with a continous and an alternative polarographic current were compared to those obtained by cyclic voltammetry. These former experiments and a study as a function of pH lead to proposing a reduction mechanism of the thioether function with is the reactive site of these molecules.A complementary study as a function of concentration permetted to establish the optimal conditions for quantitation and the detection limit reached with classical and differential pulse polarographies.