bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Conformational Analysis of 2‐(X), 4‐(Y)‐Substituted Pentanes (X, Y = OH, SH), Using Chiroptical Properties and1H NMR Spectroscopy
Authors: Spiessens L. I. , Becu C. , Hosten N. , Anteunis‐De Ketelaere F. , Anteunis M. J. O. , Tavernier D. 
Published: September 2010

AbstractOptically active threo‐(2S,4S)‐4‐mercapto‐2‐pentanol, erythro‐(2R,4S)‐4‐mercapto‐2‐pentanol and threo‐(2S,4S)‐pentanedithiol, were prepared from threo‐(2R,4R)‐pentanediol. The mechanism of their formation is discussed. The molecular optical rotation [M]Dof these compounds, of trans‐(4S,6S)‐, cis‐(4S,6S)‐dimethyl‐1,3‐oxathiane and of trans‐(4S,6S)‐dimethyl‐1,3‐dithiane, was determined and was related to the composition of the conformational mixture using Brewster's conformational rotatory power model.A complete conformational analysis of the six 2‐(X)‐4‐(Y)‐substituted pentanes (X,Y = OH, SH) was obtained from their1H NMR spectra in combination with their chiroptical properties. The threo compounds favour the aa conformation, whereas the ag−/g+a forms are prefered in the erythro isomers, except for the 2,4‐diols where the intramolecular hydrogen bonded form is predominant.
Procédé de Fabrication D'Acide Phosphorique par Voie Humide a L'Hémihydrate Préparation de Diverses Formes D'Hémihydrates Utilises Comme Plâtre
Authors: Hambersin J. M. 
Published: September 2010

AbstractWe have summarized the different procedures described in the literature for the production of phosphoric acid of which the solid phase is either the dihydrate, the alphahemihydrate or the anhydrite.In order to establish the operational parameters for the attack of the phosphate by sulfuric acid, it was necessary to examine the transition speed and the duration of the stability of the alpha‐hemihydrate in the system calcium sulfate‐phosphoric acid ‐ water in function of the temperature and the phosphoric acid concentration and to establish the equilibrium diagram basis for those results. The objective of our study was to examine the characteristics of the alpha‐hemihydrate which is used as plaster and which is formed by the attack of phosphate with sulfuric acid.Thus, we have:
‐ examined the factors affecting the crystal dimensions and their mechanical properties
‐ compared the properties of the alpha‐hemihydrate “plaster” produced by the attack of phosphate by

) Beta‐hemihydrate “plaster” which is formed by dehydration of dihydrated sulfate by baking.
) Alpha‐hemihydrate “plaster” which is yielded by the dehydratation of calcium sulfate dihydrate in salt solution with or without the addition of auxiliaries.

In the workshop, one could, after filtration and washing, transform the alphahemihydrate into plaster plates or dry it preferably by a flashing procedure (by ascension tube) (40).
Trans‐ and CIS‐Effects in Cobaloximes. Part II The Crystal Structure of Trans‐(Chloro)BIS (Dimethyl‐Glyoximato‐N, N′)‐(Morpholine‐N) Cobalt(III)
Authors: Lenstra A. I. H. , van Loock J. F. J. , Tyrlik S. K. , Stapowska H. 
Published: September 2010

AbstractThe title compound, (CI) Co(dmgH)2(morpholine), crystallizes in the monoclinic system, space group P21/c with a = 9.031 (3), b □ 16.181 (5), c = 12.571 (4)Å, β = 93.33 (3)° and Z = 4. The structure was solved to R □ 0.074 for 2411 reflections. A comparison with (benzyl) Co(dmgH)2(morpholine) shows a marked trans‐influence on the Co‐N(morpholine) bond length, Co‐N being 2.022Å in the chloro and 2.11 Å in the benzyl complex.
Photoreactivite Acétalique en Serie Hétérocyclique et Osidique
Authors: Descotes G. 
Published: September 2010

AbstractThe acetalic photoreactivity of cyclic acetals was studied by some intramolecular acetalic hydrogen abstraction using photochemical ways (NORRISH. II type and BARTON ‐ like reactions).The regioselectivities and stereoselectivities of these reactions were deduced from photochemical transformations of different tetrahydropyrannic cyclic ketoacetals, oxoalkglglycosides and hydroxyalkylglycosides.The abstraction of γ‐acetalic hydrogen is not stereoselective by excited carbonyl groups but regiospecific to give lactones in good yields. With hydroxyalkyl hypoiodites, this γ‐H abstraction is stereoselective to yield anomeric orthoesters with predominant retention of configuration.By δ‐acetalic hydrogen abstraction, the photocyclization of oxoalkylglycosides leads to hydroxy spiro ketals with retention of configuration. The influence of differents substrates, of carbonyl substituents and temperature effects were described. In osidic series (gluco, manno, 2‐deoxy), β‐anomers are more photoreactive than α‐ones.All these results can be interpreted using stereoelectronic effects at the acetalic center for the photocyclization reactions.
Synthesis of some zinc(II), cadmium(II) and mercury(II) complexes with dibasic quadridentate schiff bases
Authors: Erinoso E. O. , Ghose B. N. 
Published: September 2010

AbstractSix new complexes of Zn2+, Cd2+ and Hg2+ of the Schiff bases derived from biacetyl and ethanolamine, benzil and ethanolamine have been isolated. Their characterization is based on their analytical and spectral data.
Etude de la Texture des Nodules Oceaniques Par L'Analyse des Isothermes D'Adsorption‐Desorption D'Azote
Authors: Dodet Claude , Noville Francis , Crine Michel , Pirard Jean‐Paul 
Published: September 2010

AbstractThe porous texture of oceanic manganese nodules was studied by analysis of adsorption‐desorption nitrogen isotherms. The influence of calcination temperature on texture under nitrogen and hydrogen flows was determined.The nodules are characterized by a very high specific area and could be a good catalyst for several reactions as hydrotreatment of heavy residues.
Synthese et Reactivite du [3, 2‐b] Pyridino [4, 5] Benzo‐1, 3a, 6, 6a‐Tetraazapentalene
Authors: Maquestiau A. , Flammang‐Barbieux M. , Vilain E. , Pfister‐Guillouzo G. 
Published: September 2010

AbstractA new heteroaromatic pentalene, [3,2‐b] pyridino [4,5] benzo‐1,3a, 6, 6a‐tétraazapentalene [3] has been prepared by direct condensation of 2‐chloro‐3‐nitropyridine with benzotriazole followed by reductive cyclisation of the 1‐(3′nitro‐2′‐pyridyl) benzotriazole intermediate with triethylphosphite. The spectral and chemical properties of this new compound are described and the positions of the introduced substituents are determined as well by 1H NMR spectroscopy as by EHT calculations.
Spectres RMN‐1H de β‐Aminothiols, Disulfures et Thiazolidines Derivés de la Thioephedrine
Authors: Kone B. , Gelbcke M. 
Published: September 2010

AbstractA series of β‐aminothiols and disulfides related to northioephedrine (N‐CH3; N‐C2H5; N‐iC3H7 and N‐t C4H9) and the series of the corresponding thiazolidine from paraformaldehyde have been synthesized. The study of their 1H‐NMR spectra allowed the differentiation of the diastereomers in these three series.
Digallic Acid
Authors: Verzele M. , Delahaye P. , van Dijck J. 
Published: September 2010

AbstractDigallic acid was prepared by partial acid hydrolysis of tannic acid and purified by Counter Current Distribution. In water and methanol solution digallic acid is present in two isomeric equilibrium forms which were named meta and para digallic acid. Meta digallic acid, the main component, is stable in ether and acetone solution. The above was proved by HPLC, GC‐MS and NMR experiments on digallic acid and on its permethylation product.
Structure de la Preatroxigenine, Triterpenoïde Nouveau Isolé de Atroxima Afzeliana Oliv. (Ex Chod) Stapf
Authors: Babady‐Bila  , Warin R. , Delaude C. , Huls R. 
Published: September 2010

AbstractA combination of oxidative and hydrolytic cleavage of atroximin, saponin isolated from the roots bark of Atroxima afzeliana, yields preatroxigenin (the postulated precursor of atroxigenin, atroxigenic acid and atroxigenic acid lactone(1)), p‐methoxycinnamic acid and 3,4‐dimethoxy cinnamic acid. The structures of these compounds are deduced from their physical, chemical and spectroscopic data. The sugars of the glucidic moiety of atroximin are identified from the perchloric acid hydrolysate.
Reactivity of Electrophilic Allyl Halides
Authors: Verhé R. , De Kimpe N. , De Buyck L. , Courtheyn D. , van Caenegem L. , Schamp N. 
Published: September 2010

AbstractReactions of allylic halides bearing two electron‐withdrawing groups in γ‐position with various nucleophiles (alkoxides, phenoxide, thiolates and cyanide) gave rise to substituted electrophilic cyclopropanes or ring‐opening products, depending upon the reaction conditions, the nature of the nucleophiles and the activating groups and the substitution pattern of the allyl halides. A kinetic study revealed that the reaction involved a nucleophilic addition as the rate determining step followed by a fast ringclosure.
The Preparation of Pure 2‐Thio‐Thiazolidine‐4‐Carboxylic‐Acid (TTCA) as a Reference Standard for Carbon Disulfide Exposure Tests
Authors: Rosier J. , Simonds R. , van Peteghem C. , Vanhoorne M. 
Published: September 2010

Abstract2‐Thio‐thiozalidine‐4‐carboxylic‐acid is synthesized and subsequently purified by high‐pressure liquid chromatography. The spectral properties of the title compound are described and commented upon.
Structure and electronic spectra of small free radicals by quantummechanical methods
Authors: Bruna Pablo J. , Peyerimhoff Sigrid 
Published: September 2010

AbstractLarge‐scale multi‐reference configuration interaction calculations are carried out for the prediction of potential energy curves of several small radicals in their ground and excited valence‐shell and Rydberg states. The Gaussian AO basis employed therein is of double‐zeta plus polarization quality and includes up to f functions and semi‐diffuse p and d functions for proper description of charge‐transfer and correlation effects. Special emphasis is placed on AH and AH2 systems and their positive and negative ions with A=Si, P and S from the second‐row and on the distinctions relative to their first‐row analogues. Various properties such as spin‐orbit splittings and radiative lifetimes are also calculated. The importance of configuration interaction treatments for the correct prediction of the ordering of states in the transition metal hydrides ScH, ScH+, TiH and TiH+ is also pointed out. The relative stability of states in a large number of AB systems with A and B from the first and/or second‐row is discussed in light of their importance for larger systems with an AB center and with respect to their photoelectron spectrum which oftentimes does not allow the direct intercombination between ground states of neutral systems and their corresponding ions. The work should demonstrate the capability of today's theoretical ab initio methods for obtaining reliable information for small systems parallel or complementary to experimental studies.
Ionic Aromaticity as a Unifying Concept in Aromatic Reactivity
Authors: van Hooydonk Guido , De Keukeleire Denis 
Published: September 2010

AbstractIonic pi‐electron structures are used as a rationale for discussing aromatic electrophilic and nucleophilic substitution reactions. It is shown that an ionic representation of aromaticity is superior to the hitherto adopted system of resonating Kekulé structures. The observed orientation effects in aromatic substitution reactions are consistent with a general ionic reactivity scheme.
Empirical Relations for Coriolis Coupling Constants of XY3 Type of Molecules
Authors: Sengodan V. , Ramalingam P. 
Published: September 2010

AbstractNew empirical relations for computing the Coriolis coupling constants of some XY3 type of molecules have been proposed in terms of reduced mass and principal quantum number. The method of least squares is applied. The proposed relations yield very reasonable values and are comparable to the values obtained by the previous workers. Also the calculated values agree well with the experimental values.
Étude Vibrationnelle Des Trichlorures Organiques: (n‐C4H9)4NCl3, ϕ4AsCl3, C5H6NCl3, ϕ4PCl3
Authors: De Meyer M. , Levert J. M. , Vanclef A. 
Published: September 2010

AbstractIn this issue, we describe the synthesis and analysis of new trichloride compounds: tetraphenylphosphonium trichloride, (C6H5)4PCl3, and pyridinium trichloride, C5H6NCl3. Those are vibrationally studied and compared with tetrabutylammonium trichloride ((n‐C4H9)4NCl3) and tetraphenylarsonium trichloride. Raman spectroscopy shows an intense stretching band ν1 and 270 cm−1. Its straightforward intensity is explained by the preresonance spectra of the Cl3− ion.Stretching constants of trichlorides and other trihalide ions (Br3−, I3−, BrCl3−, I2Br−, ICl2−) are compared each other.
Regioselectivity in the glutathione‐phenylglycidyl ether reaction: 1H NMR characterization of the adduct
Authors: De Bruyn André , De Keukeleire Denis , van Den Eeckhout Elfride , Baeyens Willy 
Published: September 2010

AbstractA detailed 360 MHz 1H NMR analysis leads to the unambiguous structural identification of the compound, which is regioselectively formed in the chemical and enzymatical reactions between glutathione and phenylglycidyl ether. The thiol group attacks preferentially the least substituted oxirane carbon atom.
Structures Des Ions [M‐CH3]+ Provenant de la Fragmentation de la 2‐Heptanone Ionisée
Authors: Maquestiau A. , Flammang R. , Meyrant P. , Audier H. E. , Milliet A. 
Published: September 2010

AbstractCollision‐induced dissociations‐mass analyzed ion kinetic energy (CID‐MIKE) spectrometry has been used to characterize [M‐CH3]+ ions from ionized 2‐heptanone. Acylium [CH3(CH2)5 C=0] ions are produced at short times (within the source), while protonated cyclohexanone is formed exclusively in the field‐free regions.
Novel Donor‐Acceptor Substituted Heteroaromatic Compounds
Authors: Gompper Rudolf 
Published: September 2010

AbstractVinamidinium salt can be converted via 1,5‐dipolar cyclization into electronrich thiophenes, pyrroles, thiazoles and imidazoles. Diazaquinoneiminium salts react with nucleophiles to methylenepiperazines and dihydropyrazines. Donor‐substituted 1,3,5,7‐tetrazocines, cyclopentadienylium and aza(diaza)cyclopentadienylium salts, though formally antiaromatic, are stable compounds.
Functionally Substituted Vinyl Carbanions Versatile Intermediates in Heterocyclic Synthesis
Authors: Schmidt Richard R. 
Published: September 2010

AbstractDirect C‐lithiation of functionally substituted acrylates yields versatile intermediates for syntheses of butenolides, tetronates, α‐hydroxytetronates, pyrrolenines, cyclopentenones, oxalacetates and maleic acid derivatives. A wide variety of substituents are compatible with this lithiation: alkyl, aryl, electron‐donating and electron‐withdrawing substituents in α‐ or β‐position conducting to interesting regio‐and stereoselectivities. The compounds obtained are portions of many natural products. Approaches to the synthesis of aspertetronins, gregatins, ascorbic acids, chlorotricolide, and KDO will be outlined.
AlPO4‐Supported nickel catalysts. IV.‐Substituent effects in competitive hydrogenation of styrene and its α‐methyl derivative
Authors: Campelo J. M. , Garcia A. , Luna D. , Marinas J. M. 
Published: September 2010

AbstractStyrene (S) and its α‐methyl derivative (MS) were competitively hydrogenated over a series of nickel catalysts supported on the AlPO4, AlPO4‐Al2O3 and AlPO4‐SiO2 systems, using methanol as solvent, under initial hydrogen pressure in the range 0.4‐0.6 MPa and temperatures between 288 and 323 K, obtaining the relative reactivities RMS,S and the relative adsorption constants KMS,S. The RMS,S and KMS,S values were less than unity in the range 0.04‐0.08 indicating that S was adsorbed more strongly and less hindered on these catalysts than MS.With respect to the influence of temperature and pressure on competitive hydrogenation, the relative reactivity RMS,S was found to be independent of the initial hydrogen pressure while the changes of RMS,S with temperature followed and Arrhenius‐type law below a temperature limit. This limit, as well as the slopes and intercepts of the representation log RMS,S vs. T−1, depended on the supports.
Rotating Ring‐Disk Study of the Cu(II)/Cu(O) System on a Gold Electrode in Sulphuric Acid Solution
Authors: Vandenbruwaene J. , Kiekens P. , Temmerman E. 
Published: September 2010

AbstractThe reduction and oxidation reactions of the Cu(II)/Cu(O) system have been studied with a rotating gold ring‐disk electrode in 0.2 M sulphuric acid solutions.Two reduction waves R1 and R2 are obtained. R1 is mainly attributed to the underpotential deposition of copper while R2 is associated with the convective‐diffusional formation of bulk copper metal.Three oxidation (stripping) peaks O1, O2 and O3 are observed. O1 at most positive potentials, is thought to result from the oxidation of underpotential copper. The second stripping peak O2 may originate from the dissolution of copper atoms in direct contact with the underpotential copper, having slightly different properties with respect to the bulk copper atoms. Bulk copper is supposed to be oxidized in the third stripping peak, O3.
Iridoids: The Total Synthesis of the Aglucones of (±)‐8‐Epiloganin and (±)‐Mussaenoside Via Bicyclo |3.3.0| Octenes
Authors: Storme P. , Callant P. , Vandewalle M. 
Published: September 2010

AbstractThe nitrone‐olefin cycloaddition reaction has been used to construct cis‐fused bicyclo|3.3.0| octanes or diquinanes as potential intermediates for C‐11 functionalized iridoids. The isoxazolidine 7 was obtained in four steps from the commercially available 2‐cyclopentene‐1‐acetic acid 4. Different functionalized diquinanes 8 to 19 and 22 to 24 have been prepared. As illustrative examples of iridoid synthesis, compounds 21 and 26, the O‐methyl protected aglucones of (±)‐8‐epiloganin (2) and (±)‐mussaenoside (3) have been synthesized starting from the common key‐intermediate 11.
D.C., A.C. and Complex Plane Polarographic Behaviour of Copper (II) in Monoethanolamine, Sodium Perchlorate/Monoethanolammonium Perchlorate Solutions
Authors: Sridhar P. , Subrahmanya R. S. 
Published: September 2010

AbstractA detailed investigation of d.c., a.c. and complex plane polarographic behaviour of copper (II) in mixtures of monoethanolamine and sodium perchlorate and monoethanolamine and monoethanolammonium perchlorate is made. In solutions containing monoethanolamine and sodium perchlorate, the reduction is found to be two‐electron addition process, the extended d.c. wave being due to more than one complex species in sluggish equilibrium. The a.c. and complex plane polarographic techniques show reduction due to only one of the species. The formula of the species is given on the basis of a.c. summit potential shift with change in ligand concentration. In solutions containing monoethanolamine and monoethanolammonium perchlorate, two 1:1 waves are obtained in d.c. polarography, the separation increasing with increase in monoethanolammonium perchlorate concentration. Corresponding to the two d.c. polarographic waves, the a.c. and complex plane polarograms also indicate two peaks. On the basis of complex plane polarography, the rate constants of the various processes have been determined. Based on the d.c. polarography, the formulae and stability constants of copper (II) and copper (I) complexes have been determined. The composition of the two complex species are given as CuM3OH+ and CuM+2.
Termination of CE(IV)‐Diacetone Alcohol Redox System Initiated Polymerization of Acrylonitrile by V(V): A Kinetic Study
Authors: Srinivas P. , Nageswar Rao K. , Sethuram B. , Navaneeth Rao T. 
Published: September 2010

AbstractPolymerization of acrylonitrile (AN) initiated by Ce (IV)‐diacetone alcohol (DAA) redox system was studied in the presence of V(V). Rate of polymerization was decreased considerably by the addition of small amounts of V(V). Polymerization was not observed either by V(V) alone or by V(V)‐DAA redox system. Under the experimental conditions orders with respect to [Ce(IV)], [DAA] and [AN] were found to be 0.5, 0.5 and 1.5 in the absence of V(V) and these changed to 1.0, 1.0 and 2.0 respectively in the presence of V(V). Mutual termination of polymeric radicals in the absence of V(V) becomes linear termination with V(V) in the presence of V(V). A probable mechanism is proposed to explain the results.
Rates of Peptide Formation Involving Imino Acid Residues
Authors: Wante Dirk P. M. , Anteunis Marc J. O. 
Published: September 2010

AbstractThe determination of the rates for peptide coupling in tetrahydrofuran between Z‐Aaa‐OPcp (Aaa = Ala, (NMe)Ala, Pro, Thz, Pip and (S)Pip) and H‐Bbb‐OMe (Bbb = (NMe)Ala, Pro, Thz, Pip and (S)Pip) allowed us to evaluate the relative reactivities between these members, either as active components or as amino components. The reactivity of Pro (either as the active species or the amino component) equals that of (NMe)Ala. The reactivity of Pip and (S)Pip as imino components is low while the activation energy is raised by an amount that roughly equals the energy increment needed for bringing the carboxylate grouping from the equatorial to the axial position. The reactivities of these six‐membered residues are also appreciably low when being the active components during peptide coupling. The presence of a ring‐sulfur atom at γ‐position of nitrogen additionally decreases the rate for peptidation, especially if (S)Pip is the imino component.
Solubility Behaviour of Ionic Solid Solutions and Their Precipitation from Aqueous Solution
Authors: Driessens F. C. M. , Verbeeck R. M. H. 
Published: September 2010

AbstractIt is shown that the distribution of ions over the solid phase and an aqueous solution can be interpreted in terms of Roozeboom's classification in the case of ideal ionic solid solutions and regular ionic solid solutions with and without ordering or substitutional disorder. A general relation is derived between the distribution coefficient D of the system and the solubility products of the components of the solid phase. In this way D can be determined experimentally in an independent way. It appears that in practice type II and type III systems are indistinguishable from type I systems, when the distribution coefficient D differs about one order of magnitude or more from unity even in the case of good recryatallization. In those cases distribution diagrams are not suitable to derive the nature of the series of solid solutions involved.
Heats of Crystallization of CaSO4.2H2O
Authors: Deckers Jacques M. , Lash John E. , Burns Georges 
Published: September 2010

AbstractThe heat of crystallisation of Gypsus (CaSO4.2H2O) has been measured. At room temperature (23°C), from solutions whose initial concentration is greater than 0.4 sole 1−1 in CaSO4), an exothermic precipitation occurs with an enthalpy of crystallisation of −20.2 ± 0.5 KJ mol−1. From solutions whose initial CaSO4 concentration is less than 0.25 mole 1−1 the crystallisation process is endothermic, the enthalpy of crystallisation being +2.4 ± 0.2KJ mol−1.Under microscopic examination the exothermically produced crystals appear as very thin needles, while the endothermic crystals are platelet like. The latter are identical to the crystals of gypsum found in nature. Analysis of all precipitates formed below 70°C, corresponded to the formula CaSO4.2H2O.All precipitates have the same X‐ray powder spectra (Debye ‐ Scherrer). However, Differential Scanning Calorimetry produces distinct scans for the two types of precipitates obtained. The logical interpretation of these results is that there exists two distinct phases of CaSO4.2H2O. The existence of two phases of gypsum would explain why in some (but not all) tombs in the Valley of the Queens and the Valley of the Kings in Upper Egypt, the gypsum, serving as a base layer for mural paintings, has become dehydrated.