bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reactivity of α‐Halogenated Imidoyl Cyanides1
Authors: de Kimpe Norbert , Verhé Roland , de Buyck Laurent , Chys Jan , Schamp Niceas 
Published: September 2010

AbstractA series of twenty five α‐chloro‐ and α‐bromoimidoyl cyanides was prepared by halogenation of α‐cyanoenamines with N‐halogensuccinimide in carbon tetrachloride. α‐Halogenated imidoyl cyanides are a new class of easily accessible trifunctional compounds, from which the reactivity towards various nucleophiles was investigated. A variety of reaction types was encountered among others elimination, α‐substitution and addition‐elimination leading to new types of trifunctional compounds.
Contribution À L'étude Theorique de la Liaison Hydrogène VIII. les Complexes HF…HOR (R = H, CH3, NH2, F)
Authors: Ruelle Paul , Leroy Georges 
Published: September 2010

AbstractL'étude ab initio des complexes par liaison hydrogène tenant compte de l'effet de substituant sur la molécule donneur de proton est effectuée en base double 4–31G grâce au programme GAUSSIAN‐70. Les résultats obtenus ne diffèrent pas sensiblement de ceux des complexes entre hydrures. Les potentiels électrostatiques autour des différentes molécules partenaires peuvent être considérés comme indices statiques de complexation, aptes à rationaliser la tendance relative des molécules à fonctionner comme donneur ou comme accepteur de proton ou d'électrons. Les variations observées pour les distances intermoléculaires pourraient être à la base d'un modèle susceptible ďatteindre les électronégativités de groupe.
Green's function analysis of some linear asymmetrical triatomic molecules
Authors: Namasivayam R. , Sankaran V. 
Published: September 2010

AbstractAn attempt is made to apply the Green's function analysis of substituted and perturbed molecules proposed by DeWames and Wolfram to the vibrational study of some linear asymmetrical triatomic molecules. The potential energy constants, mean amplitudes of vibration, Coriolis coupling constants and rotational distortion constants are computed and compared with the reported values, whichever is available. The path length and bond charge parameters are also calculated. The Coriolis sum rule for this type of molecules is verified.
Evidence for the occurrence of an oxygen to oxygen acyl shift in 7‐acetoxybicyclo|3,2,0|heptan‐2‐ones upon chemical ionization mass spectrometry
Authors: Claeys Magda , van Audenhove Martine , Vandewalle Maurits 
Published: September 2010

AbstractAn oxygen to oxygen acyl migration has been observed in 7‐acetoxybicyclo|3,2,0|heptan‐2‐ones upon isobutane chemical ionization mass spectrometry. The mechanism of this rearrangement is discussed and is investigated by means of deuterium labelling techniques.
Structure assignment and conformations of the four diastereomeric cyclic dipeptides of phenylalanine, S‐methyl‐4‐thiazolidinium‐2‐carboxylic ACII
Authors: Anteunis Marc J. O. , Bécu Chris , Liberek Bogdan , Kołodziejczyk A. 
Published: September 2010

AbstractThe title compounds were obtained each time as a mixture of the cis‐S‐methyl and trans‐S‐methyl diastereomers by methylation of the respectively cis‐ and trans‐diketopiperazines (DKP), c/L‐Phe, L‐Thz/ and c/D‐Phe, L‐Thz/ (Thz = 4‐thiazolidine‐2‐carboxylic acid = 4‐thiaproline).Although these methylthianium compounds were unstable in protic solvents and could therefore not be separated into the single diastereomers, an 1H NMR study on the pairwise mixtures enabled the identification of the configurations and an insight upon their respective conformations was possible. In D2O, the aromatic ring is folded for about 75% over the DKP ring, as well in all four onium derivatives as in the parent sulfide‐DKP's.The two compounds having the S⊕‐Me substitution trans with respect to the thiazolidine carboxamide grouping (cis‐2F and trans‐2F, figures 1 and 2) possess a thiazolidine fragment in the envelope α−, with Cα as the flap down. The five membered ring in the trans‐2S isomer is best characterized as S+ (envelope with sulfur as the flap up), while in the cis2S isomer a pronounced admixture of the γ− and/or SγT is probably present.The DKP‐rings in the onium derivatives are rather flat (buckle <15°) except in trans‐2S where the puckering may perhaps amount to 40°.
Synthesis of new chiral phosphines for asymmetric catalysis
Authors: Kagan H. B. , Fiaud J. C. , Hoornaert C. , Meyer D. , Poulin J. C. 
Published: September 2010

AbstractA new analog 6a of diop is prepared from D‐mannitol. The synthesis of the 1,3‐diphosphine 9a and of 1,2‐aminomonophosphine 12 are described. All these phosphines behave presumably as bidentate ligands, their efficiency in asymmetric catalysis are compared in a set of reactions involving asymmetric C‐H or C‐C bond formations.
CIDNP study of quenching processes of excited xanthene dyes by aromatic amines
Authors: Muszkat K. A. , Khait I. 
Published: September 2010

AbstractStrong proton nuclear polarization is produced by the quenching of excited triplet state Rose Bengal molecules by aromatic amines. In secondary amines significant polarization (but no permanent chemical change) is observed in the ring ortho and para protons and in the N‐alkyl α methylene (or methyl) protons. In this case the operation of a highly reversible hydrogen atom transfer quenching mechanism is indicated. Tertiary aromatic amines give polarized unstable intermediates for which the perpendicular aromatic ring structure is suggested.
Reactions with phosphinealkylenes XXXVII. : Reactions of phosphinealkylenes with Cos. A method for the formation of thiolesters
Authors: Bestmann H. J. , Saalbaum H. 
Published: September 2010

AbstractPhosphinealkylenes 1 react with COS to give betaines 14. Their reaction with alkyl halides 4 generates phosphonium salts 15 which, for R2H, can be easily converted into the phosphoranes 17. The corresponding thiolesters 19 of α,β‐unsaturated carboxylic acids are obtained by means of the Wittig‐reaction. The electrolysis of 15 (R1, R2 ≠ H) gives thiolesters 16.
Infrared study of the νOH stretching vibration of hydrogen bonded complexes involving phenol derivatives and thiocarbonyl bases. Comparison with carbonyl bases
Authors: Reyntjens‐Van Damme D. , Zeegers‐Huyskens TH. 
Published: September 2010

AbstractThe formation enthalpy, the frequency shift and integrated intensity of the νOH stretching vibration have been determined for hydrogen bonded complexes formed between phenol derivatives and tetramethylthiourea or dimethylthioformamide. These data are compared with complexes involving carbonyl bases. The results suggest that, at constant ‐ΔH values, more charge is transferred to the σ (OH) bond with thiocarbonyl bases; this is in qualitative agreement with the far infrared results and the theoretical predictions.
Structure Cristalline et Moléculaire des Isomères E et Z de la Diamantanone‐3 Oxime
Authors: Declercq J. P. , Germain G. , van Meerssche M. , Hajek M. , Volka K. 
Published: September 2010

AbstractThe crystal structure of Z‐ and E‐forms of diamantane‐3‐one oxime has been determined by three dimensional X‐ray diffraction analysis. The structures were solved by direct methods (MULTAN) and refined by least squares to R‐values of 6.4 and 5.5%, respectively for 1353 (E) and 1646 (Z) independant reflections. Both crystals are monoclinic, P21/n, with cell dimensions a = 12.903, b = 11.939, c = 7.822 Å, β = 107.15° for E and a = 14.407, b = 12.083, c = 6.616 Å, β = 93.1° for Z. The unit cells contain four molecules. The structure of both isomers is formed by dimers of oximes held together by hydrogen bond. Significant intermolecular distances are: N…N′ 3.019 (E), 3.038 (Z), N…0° 2.771 (E), 2.782 Å (Z). A comparison of the obtained and literature data on oximes and adamantanoide compounds is given.
Rapid extraction and spectrophotometric determination of lead (II) with N‐p‐chlorophenylbenzohydroxamic acid
Authors: Agrawal Y. K. , Patel S. A. 
Published: September 2010

AbstractA rapid extraction and spectrophotometric determination of lead with N‐p‐chlorophenylbenzohydroxamic acid (N‐p‐Cl‐BHA) is described. The lead forms a yellow coloured complex with N‐p‐Cl‐BHA at pH 9.0 which is extracted with chloroform. The absorption spectra are registered at 388 nm. The molar absorptivity is 4.5 × 102 l mol−1 cm−1. Effect of pH, solvents, electrolytes, reagent concentration and diverse ions are described.
Rapid extraction and spectrophotometric determination of niobium with N‐P‐chlorophenyl‐benzohydroxamic acid
Authors: Agrawal Y. K. , Patel S. A. 
Published: September 2010

AbstractA rapid method has been described for the extraction and spectrophotometric determination of niobium with N‐p‐chlorophenylbenzohydroxamic acid by extraction of the complex into toluene from 8‐10 M HCl, containing stannous chloride. The complex gives the maximum absorbance at 365 nm and the molar absorptivity is being 3.0 × 104 1 mol−1 cm−1. It obeys Beer's law within the range of 0.3 ppm to 20 ppm.
Vanadium Determination in Petroleum Crude ‐ Spectrophotometric Method
Authors: Raghavan  , T. N. V.  , Agrawal  
Published: September 2010

AbstractA new spectrophotometry method for the estimation of vanadium is developed. The vanadium (V) solution oxidizes iodide ion (I) in potassium iodide(KI) releasing free iodine in acid media. The iodine released is complexed with N‐phenylbenzohydroxamic acid (PBHA) (0.1% w/v in chloroform). The complex has a maximum absorbance at 510 run. The PBHA itself and the PBHA‐KI complex have no absorption at 510 nm. The iodine complex follows Beer's law over the concentration range 0.05 to 0.35 ppm.The nature of the iodine‐complex in the PBHA, and the applicability of the method for the vanadium complexes in nature are discussed.
Solution Conformation of Cis and Trans N‐Acetyl‐L‐Thiazolidine‐4‐Carboxylic Acid
Authors: Frans  , Borremans A. M. , Nachtergaele Willy A. , Budesinsky Milos , Marc  , Anteunis J. O. , Kozodziejczyk A. , Liberek Bogdan 
Published: September 2010

AbstractFrom an extensive 1H and 13C NMR study, the conformation of cis‐ and trans‐N‐acetyl‐L‐thiazolidine‐4‐carboxylic acid in D2O is revealed to be close to an envelope with Cβ as the flap down (β−) in the entire pD range. The pucker around N‐Cα remains pronounced (θ → 83°). The cis‐trans equilibrium is in favour of the trans isomer (70%) in acidic medium, but slightly in favour of the cis isomer (54%) in basic solution.
Non‐Aqueous Titrimetric Determination Of N‐P‐Chlorophenylbenzohydroxamic Acids: Visual And Potentiometric Titration In Dimethylformamide
Authors: Agrawal Y. K. , Roshania R. D. 
Published: September 2010

AbstractN‐p‐Chlorophenylbenzohydroxamic acids are titrated visually in non‐aqueous media against 0.1 M potassium methoxide using thymol blue and crystal violet as indicators. The potentiometric titrations were also performed in non‐aqueous media with platinum and calomel electrodes. The molecular weights of hydroxamic acids are calculated.
Étude théorique de réactions de cycloaddition entre les dithiole‐1, 2 thiones‐3 et leurs analogues azotes avec divers acétyléniques
Authors: Pinel Raoul , Gelize‐Duvigneau Michel , Benabdallah Mohammed Zaher , Arriau Jean 
Published: September 2010

AbstractUne étude théorique à l'aide des modèles de calculs appliquée à la cycloaddition dipolaire‐1, 3 de divers acétyléniques sur les dithiole‐1, 2 thiones‐3 et quelques analogues azotés rend bien compte des observations expérimentales et permet une extrapolation des résultats pour le méthylène‐3 dithiole‐1, 2 et le méthylène‐3 dithiazole‐1, 2, 4.
Carbon‐13 Magnetic Resonance Spectroscopy. A Study Of Colchicine And Related Compounds
Authors: Elguero J. , Muller R. N. , Blade‐Font A. , Faure R. , Vincent E. J. 
Published: September 2010

AbstractThe carbon‐13 NMR signals of twelve cochicinic derivatives, have been assigned and some 1H‐13C coupling constants have been measured. The substituent effects, the colchicine‐isocolchicine isomerism, the prototropy of colchiceine and trimethylcolchicinic acid and the acylotropy of colchiceine acetate are discussed. There is a slight predominance of the isocolchicinic tautomer, both in the case of the prototropy and the acylotropy.
Application des Méthodes Modernes de Construction de Matrices D'Expériences Optimales. I. Examen Critique des Résultats Cinétiques Obtenus Par Pivovarov, Istomin et Collaborateurs Dans la Solvolyse de Bases de Mannich Dinitrées
Authors: Mathieu D. , Phan R. , Luu Tan , Elguero J. 
Published: September 2010

AbstractThis general methodological paper uses a concrete set of kinetic data (about 1200) concerning the solvolysis of Mannich bases of the type R1C6H4‐NH‐CH2‐C(NO2)2‐C6H4R2. The set was obtained by Pivovarov et al. and consequently submitted to a critical appraisal by Pivovarov, Istomin et al. in order to reduce the number of experiments up to 64. The utilization of the exchange algorithms allows a reduction up to 16, preserving the qualities of the experimental matrix, even when some experiments are proving impossible. The interpretation of the coefficients of mathematical models, expressed as a function of natural variables, could lead to erroneous conclusions; on the contrary, with scaled variables, it is possible to draw correct conclusions from the principal effects and from the interactions ones.
Catalytic Extended Double Bond Migration With Retention Of Configuration: A “Zip‐Reaction”
Authors: Weissberger E. 
Published: September 2010

Abstract(+) Citronellol was catalytically isomerized by Fe(CO)5 into (+)dihydrocitronellal with partial retention of configuration: the optical yield was 16 ± 1 % at 140°C. Isolation of partially isomerized intermediates and use of citronellol deuterated at various positions allowed a clear description of the reaction mechanism as a succession of 1,3 hydrogen shifts. The observed partial retention of configuration suggests that full 1,7 isomerization occurs before metal‐olefin dissociation occurs even once.
Conformations privilegiées des sulfures de dithienyles: Étude PAR spectroscopie d'absorption électronique
Authors: Meunier P. , Arriau Et J. 
Published: September 2010

AbstractThe experimental and theoretical study of electronic absorption spectra (UV) of dithienyl sulfides shows that non planar conformations are favored in vapour phase and in solution. The presence of halogen atoms in positions “ortho” to the junction of the rings induces a very important modification of preferential conformations.
Crystal Structure Of Jolkinolide A From Euphorbia Huachangana (Kl & Gke)Boiss
Authors: Hoet P. , Landa I. , Rivera M. , van Meerssche M. , Germain G. , Declercq J. P. 
Published: September 2010

AbstractThe structure of the title compound has been determined by single crystal X‐ray diffractometer. Crystal data are as follow: monoclinic, P21, a = 12.819 (25), b = 9.416 (10), c = 7.205 (11) Å, B = 103.46 (15)°, V = 846 (5)Å3, Dx = 1.23 Mg m–3 for Z = 2.
Preparation of synthetic rotenoids(1)
Authors: Verné R. , De Kimpe N. , De Buyck L. , Steurbaut W. , Sadones M. , Willaert R. , Verbeek J. ‐P. , Schamp N. 
Published: September 2010

AbstractSeveral dehydrorotenoids have been prepared by thermal condensation of 4‐ethoxycarbonyl‐3‐chromanon derivatives with 4‐hydroxybenzofurans and 2,2‐dimethyl‐5‐hydroxychroman. Hydrogenation of the dehydrorotenoids in the presence of Pd/BaSO4 afforded rotenoids.
Non‐closed forms of monensin and nigericin free‐acid in protic solvents
Authors: Rodios Nestor A. , Anteunis Marc J. O. 
Published: September 2010

Abstract1H NMR features (shifts and interproton coupling constants along acyclic structural fragments) of monensin and nigericin free‐acid reveal that these ionophores occur in methanol as open, non‐pseudocyclic conformers, presumably with structural changes in some regions of the backbone, e.g. at the acetal spiro junction and at the hemi‐acetal tail position. No conditions could be found in order to re‐establish the closed conformations originally present in non‐protic solvents.
A terpene synthesis intermediate: (±)‐5‐ethenyl‐1, 1, 4aβ‐trimethyl‐1, 2, 3, 4, 4a, 7, 8, 8aα‐octahydronaphthalene
Authors: Coisne Jean‐Marc , Pecher Jacques 
Published: September 2010

AbstractAn improved synthesis of (±) trans‐1, 1, 4aβ‐trimethyl‐decahydronaphthalen‐5‐one 2 is described. The relative configuration of chiral centers in 2 is indirectly ascertained by X‐ray diffraction. Three synthetic schemes for the preparation of (±) 5‐ethenyl‐1, 1, 4aβ‐trimethyl‐1, 2, 3, 4, 4a, 7, 8, 8aα‐octahydronaphthalene 1 have been experimented. Conjugated diene 1 is potentially useful for the synthesis of several triterpene compounds.
Non‐ideality in systems containing inverted micelles of anionic surfactants in apolar solvents. corrections for vapour pressure osmometric data ()
Authors: Tavemler S. M. F. , Gijbels R. 
Published: September 2010

AbstractSmall angle X‐ray scattering (SAXS) and vapour pressure osmometry (VPO) are interesting methods in order to obtain, respectively, the number and weight average aggregation number of the inverted micelles of surfactants in apolar solvents. Both methods are however affected by non‐ideal behaviour within the system, resulting in a difference between the observed and true aggregation numbers.Relations are proposed which allow to calculate nwtrue and nntrue from the observed values using the concept of the volume excluded by the inverted micelles. In the case of anionic surfactants in apolar solvents this quantity can experimentally be obtained from SAXS measurements as a function of concentration.The system di‐iso‐hexadecyl zinc sulfonate in isododecane is discussed. The weight and number average aggregation numbers are almost identical and equal to 17–18 after correction for non‐ideality. This confirms the idea that the large inverted micelles are characterized by a rather narrow size distribution function. The experimental value for the excluded volume agrees rather well with that predicted for a hard sphere ensemble occupying the same volume fraction.
A method of non linear regression for determining the formation constants of ion‐ligand complexes using conductimetric results
Authors: Romanetti R. , Galea J. , Ferroni G. , Ci. Haulait‐Pirson M. , Huyskens P. L. 
Published: September 2010

AbstractA method of non linear regression is used in the determination of the constants for ion‐ligand and ion‐pair‐ligand complex formation in order to test the complexation model previously proposed3–4. When a 1:1 cation‐ligand complex is the only ligand complex formed, the values of the constants obtained by both methods are in good agreement. When ion‐pair‐ligand complex formation and addition of a second ligand to the ion‐ligand‐complex occur simultaneously, the constants obtained by the non linear regression method differ somewhat from the published values.
Preparation of pure optically active (3s)‐ and (4s)‐tert‐butylcyclohexenes
Authors: Sadozai S. K. , Lepoivre J. A. , Dommisse R. A. , Alderweireldt F. C. 
Published: September 2010

Abstract(1S, 3S) ‐3‐tert‐Butylcyclohexanol, obtained from enzymatic reduction of racemic 3‐tert‐butylcyclohexanone, is dehydrated to optically active cyclohexenes. The carbon‐13 NMR spectral data and ORD‐curves are given. The optical rotation of the (3S)−(+) and (4S) − (−) −tert‐butylcyclohexene are interpreted in terms of ring dissymetry.
Annelation of 5 or 6 membered heterocycles to uracil derivatives via phosgeniminium salt(1) condensation
Authors: Kokel B. , Lespagnol C. , Viehe H. G. 
Published: September 2010

AbstractPI salts condense with 1, 3‐dimethyl barbituric acid and 1, 3‐dimethyl‐4 ‐amino uracil to give new amide chlorides 4 and 5. These synthons lead to new aminated isoxazolo‐, or pyrimido‐ and pyrido‐pyrimidines 12, 16 & 18 on cyclisation with hydroxylamine, cyanamide and malononitrile, respectively.
The mineral in bone, dentin and tooth enamel
Authors: Driessens F. C. M. 
Published: September 2010

AbstractDetailed knowledge about the constitution and the solubility behaviour of the mineral in calcified tissues is still lacking. This knowledge is important for the understanding of the behaviour of the mineral under physiological and pathological conditions. In this study literature data on the composition and particle size of the mineral are reviewed. Their predominantly apatitic nature goes back to hydroxyapatite as their prototype. However, other calcium phosphates, like whitlockite, are also important. The various analytical data on the content of Ca, P, Na, Mg and CO3 as the main components were analyzed for their consistency with a model of variable phase composition of the mineral. This analysis revealed that the probable phase composition of the mineral in dentin and bone is the same, but different from that in tooth enamel. Studies on the solubility behaviour indicate that near the physiological pH (7.4) all phases are solubility controlling simultaneously. This supports a physiological model according to which the body fluids are close to physicochemical equilibrium with bone mineral. Hence, changes in the chemical and phase composition of the mineral which occur under pathological conditions are related to changes in the activities of the relevant components in the surrounding body fluid. The latter depend mainly on cellular activity and organic transport activity. Attention is also paid to the anticariogenic effect of fluoride and the incorporation of that component in the mineral of fluorotic bone. This study is closed with some remarks about the use of synthetic analogues of biominerals as implants in dentistry and surgery.
Some aspects of the correlation problem using FSGO orbitals
Authors: Andre J. M. , Delhalle J. , Lamotte C. 
Published: September 2010

AbstractDetailed numerical studies of the four related methods: Restricted Hartree‐Fock (RHF), Unrestricted Hartree‐Fock (UHF), Projected Hartree‐Fock (PHF) and Extended Hartree‐Fock (EHF) have been made for the hydrogen molecule using the Floating Spherical Gaussian Orbital (FSGO) technique.
Ab initio studies of structural features not easily amenable to experiment: 9. molecular structure and conformational analysis of hydrazine and methyl‐hydrazine
Authors: van Alsenoy C. , Williams J. O. , Scarsdale J. N. , Geise H. J. , Smits G. , Schäfer L. 
Published: September 2010

AbstractThe geometries of three conformations of methyl hydrazine were refined without constraints by ab initio calculations on the 4–21 G level using Pulay's force method and our normal coordinate force relaxation procedure. The most stable conformation is one in which the C‐N bond can interact with the adjacent lone pair on nitrogen. A large number of the structural details calculated are in complete agreement with qualitative predictions based on the anomeric orbital interaction model for organic systems with electron lone pairs.
Ring conformational aspects of cis‐ and trans‐n‐acetyl‐4‐carbomethoxy‐1, 3‐thiazolidine‐1‐oxide
Authors: Nachtergaele Willy A. , Anteunis Marc J. O. 
Published: September 2010

AbstractOxidation of 4‐N‐Ac‐carbomethoxy‐1, 3‐thiazolidine (1) affords the two possible sulfoxide isomers (2) (cis and trans) in a ratio of 60/40. 1H NMR‐spectral characteristics allow to assign the sulfoxide configuration in both isomers, e.g. the major compound being the trans isomer occuring essentially in an envelope with Cγ as the flap down (γ−). The cis‐isomer (minor) takes the α− and/or βαT form. These favoured ring conformations depend only slightly or not at all on the cis‐trans isomerism around the amide bond.
Widerlegung von zwei angeblichen Synthesen des hypothetischen tetrabenzoylthiirans ‐ die Umlagerungstendenz von 2‐acylaziridinen, ‐oxiranen und ‐thiiranen
Authors: Senning Alexander 
Published: September 2010

AbstractTwo alleged syntheses1, 2 of tetrabenzoylthiirane 3 do in fact furnish the isomeric 2, 2, 4‐tribenzoyl‐5‐phenyl‐1, 3‐oxathiole 7.3 2‐Acyl and especially 2, 2‐diacyl substituted three‐membered heterocycles appear to possess a general tendency to isomerize to the corresponding five‐membered heterocycles.