bluuebunny/crossref_metadata_2025_split huggingface dataset:
Halogenated 1,3‐Cyclohexanediones VI. Synthesis of Substituted 4,4‐Dimethyl‐1,3‐Cyclopentanediones
Authors: De Pooter H. , Schamp N. 
Published: September 2010

Abstract2,2,4,4,6,6‐Hexabromo‐5,5‐dimethyl‐l,3‐cyclohexanedione (III) is transformed in high yield into 2,3,5,5‐tetrabromo‐4,4‐dimethyl‐2‐cyclopentenone (IV) by reaction with sodium acetate in hot glacial acetic acid. After debromination and hydrolysis, IV is converted into 5‐bromo‐2‐isovaleryl‐4,4‐dimethyl‐l,3‐cyclopentanedione (XI).
Contribution a l'étude de l'action des Bases Sur les Sels d'Ammonium Quaternaires. VI. Réactions de Transposition, D'élimination et de Dimérisation Obtenues A Partir de Sels Quaternaires Dérivés de la 1,2,3,4‐Tétrahydroisoquinoléine
Authors: Wilputte‐Steinert L. , Fery L. P. A. , Nasielski J. 
Published: September 2010

AbstractReaction of 2‐methyl‐2‐benzyl‐1,2,3,4‐tetrahydroisoquinolinium iodide with sodium amide in liquid ammonia yields 76% 1‐orthotolyl‐2‐methyl‐1,2,3,4‐tetrahydroisoquinoline resulting from a Sommelet‐Hauser rearrangement. In the same conditions, 2,2‐dimethyl‐1,2,3,4‐tetrahydroisoquinolinium iodide yields 4% N,N‐dimethyl‐2‐vinylbenzylamine resulting from an elimination reaction and 70% 1‐(2‐dimethylaminomethy Iphenyl)‐2‐[2‐(β‐dimethylaminoethylphenyl)]‐cyclo‐propane, probably trans, (IX) resulting from dimerization followed by γ‐elimination.
Ag(I) Complexes of Some ω′‐Aminoalkylpyridinium Compounds
Authors: van Poucke L. C. , De Brabander H. F. , Eeckhaut Z. 
Published: September 2010

AbstractThe stability constants of the Ag(I) complexes of some ω'‐aminoalkylpyridinium compounds are determined by a pH‐metrical method, at 25 deg;C and in 0.5 M KNO3. The results are compared with those obtained in a similar investigation of the Ag(I) complexes of ω‐aminocarboxylic acids. In both cases complexes of the same type are formed and only quantitative differences can be observed.
Shock Tube Study of the Induction Lag in Nitrous Oxide‐Hydrogen System
Authors: Soloukhin R. I. , Tiggelen P. J. Van 
Published: September 2010

AbstractInduction lags behind incident shock waves have been measured in nitrous oxidehydrogen mixtures diluted with 90 or 95% of argon. The physical magnitudes detected in order to characterize the induction lags are either the OH‐emission at 3075 Å or the interferometric density measurements.No significant difference appears between both measurements. According to the observations in a low temperature range, the overall activation energy corresponds to 22 Kcal/mole, while at higher temperatures the apparent activation energy is about 60 Kcal/mole.The results are discussed in terms of a branched mechanism, the chain branching reactions being rate determining below 2500 °K, while the initiation process takes over above this temperature.The low temperature mechanism confirms the interpretation given to flames burning in the same mixtures.
A New Synthesis of Oxytocin Using S‐Carbobenzoxy‐Cysteines and N‐p‐Methoxybenzyloxycarbonyl‐Amino Acids as Intermediates
Authors: Vandesande F. 
Published: September 2010

AbstractA new synthesis of oxytocin is described. For the protection of the α‐amino functions the p‐methoxybenzyloxycarbonyl‐group was used. The phenolic hydroxyl of tyrosine was protected by the usual benzyl group. The free thiol functions of the cysteine moieties were protected by the carbobenzoxy group. For building up the peptide chain the step wise p‐nitrophenylester method was used. At the end of the synthesis, a fully protected nonapeptide amide was obtained, namely S–Z–N–pMZ–L–Cys–L–Tyr–L–lle–L–Glu(NH2)–L–Asp(NH2)–S–Z–L–Cys–L–Pro–L–Leu–Gly(NH2).All the protecting groups from this protected nonapeptide‐amide were removed by a reduction with sodium in liquid ammonia. After oxydation by aeration, oxytocin was obtained in a good yield.
Essais de Chloration Dirigée. XII. Photochloration d'Acétates d'Alkyles Par Agents Chlorants [1]
Authors: Ph. Soumillion J. , Bruylants A. 
Published: September 2010

AbstractPhotochemical chlorination of several alkylacetates. CH3–CO–O–R (with R = n.C3H7, n.C4H9, i.C4H9, n.C5H11), was performed, using trichloromethane‐sulfenyl chloride (TCSE) as chlorinating agent, both with and without benzene as solvent.As in our previous works, chlorination was limited in order to get a mixture of monochlorinated isomers. Experimental results, expressed in terms of relative reactivity, r.r. (alb), of two hydrogen atoms, were correlated by the equation: magnified image.The reaction constants ρ*(−1,28) and h (0,112), compared with analogous values obtained in direct chlorination (ρ* = − 084, h = 0,034) show an important increase selectivity.Reactions were also performed at different temperatures and results are discussed. Some experiments were also made with amyl acetate and trichloromethane‐sulfonyl chloride (TCSO) as chlorinating agent.
NMR‐Experiments on Acetals. XVII. Conformational Equilibria In Trans‐4‐Alkyl‐6‐Methyl‐1,3‐Dithianes
Authors: Gelan J. , Anteunis M. 
Published: September 2010

AbstractThe conformational equilibrium I ⇌ II in the trans‐4‐alkyl‐6‐methyl‐1,3‐dithianes has been computed from the study of the H‐2 proton shifts at different temperatures in pyridine‐chloroform‐carbondisulfide mixed solvent. Thermodynamic data are found in the table. A method to predict shift parameters, above the coalescence temperature, of the individual conformers has been developed and used in the calculations of equilibrium constants.Furthermore the results show that in general the nature of the alkyl group has only a small influence on the thermodynamic parameters ΔΔH° and ΔΔS°. For R = i.Pr we accept a significant amount of flexible conformation.Otherwise higher alkyl groups in 4 position prefer the axial position in comparison with methyl.
Nouvelles Voies D'Accès Aux Acides Cinnamiques. Application à la Synthèse des Acides O‐Méthylthio et O‐Méthylsélénocinnamiques Simples et Substitués
Authors: Ruwet A. , Renson M. 
Published: September 2010

Abstract1‐thio‐ and 1‐seleno‐coumarins are synthesized by cyclization of o‐methylthio and o‐methylselenocinnamic acids. The Reformatsky reaction provides a route to cinnamic acids from o‐methylthio and o‐methylselenobenzaldehydes, acetophenones and benzophenones but ethyl bromacetate behaves abnormally owing to SCH3 or SeCH3; a solution is found by preparing first the organozincic. The Perkin synthesis is also used for benzaldehydes. New methods were investigated from acetophenones and benzophenones: condensation of ethyl cyanacetate and malononitrile with benzylamine as catalyst and condensation with acetonitrile or ethyl acetate and LiNH2. Application is given for several o‐methylthio and o‐methylselenocinnamic acids.
Spiro‐isohumulones: Isohumulones with a 3‐Keto Tetrahydrofurane Moiety
Authors: Maes L. , Anteunis M. , Verzele M. 
Published: September 2010

AbstractSince 1951 it is known that methanolic alkaline isomerization of humulone produces a mixture of crystalline isomers. This paper shows that the mixture contains the four diastereoisomers with structures 12, 13, 14 and 15 of chart III. It is proposed to name these substances trans‐spiro‐isohumulone I and II and cis‐spiro‐isohumulone I and II respectively.
Une Méthode pour Déterminer la Participation des Chai̊nes Aliphatiques à la Réactivité d'un Centre Fonctionnel
Authors: Vidal B. 
Published: September 2010

AbstractNous exposons une méthode qui permet d'étudier, à partir de données cinétiques, l'influence des chaînes aliphatiques sur la réactivité d'un centre fonctionnel qui leur est adjacent.
Electrochemical Growth of NpO2 Single Crystals
Authors: Martinot L. , Machiels A. , Fuger J. , Duyckaerts G. 
Published: September 2010

AbstractWe have prepared NpO2 single crystals by electrochemical reduction of neptunyl chloride in LiCl—KCl between 700 and 870°C, both on pyrolytic graphite and platinum cathodes. The lattice parameter is a = (5.433±0.001) Å.
Synthèses dans la Série du Benzo(b)Sélénophène
Authors: Christiaens L. , Dufour R. , Renson M. 
Published: September 2010

AbstractNous étudions la réactivité des méthyl‐2 et méthyl‐3 benzo(b)sélénophènes vis‐à‐vis d'agents électrophiles (réactions de bromuration, de Friedel et Crafts). Nous décrivons également une série de synthèses réalisées sur les positions 2 et 3 de l'hétérocycle de base.
Essais de Chloration Dirigée: XIII. La Photochloration Directe des Hydrocarbures Arylaliphatiques [1]
Authors: Corbiau J. L. , Bruylants A. 
Published: September 2010

AbstractPhotochlorination in liquid phase was performed at various temperatures (from 22 to 98°C) in order to determine the ratio of the various monochlorinated isomers generated during the reaction. The different compounds studied are of general formula C6H5R, where R is equal to: C2H5, n.C3H7, i.C3H7, n.C4H9, sec. C4H9, n.C5H11.Substitution only takes place in the side chain and preferentially in the α position: for instance, ethylbenzene gave 90% of the α and 10% of the β‐chloroethylbenzene. Differences between activation energy of the two chlorinations of the same hydrocarbon are relatively high. In the case of C2H5C6H5 the value (Eα ‐ Eβ) amounts 3.130 cal. m−1.
Nouvelle Synthèse de Benzo(b)Furannes, Thiophènes et Sélénophènes Alcoyles ou Aryles en Position 2
Authors: Christiaens L. , Renson M. 
Published: September 2010

AbstractNous décrivons une nouvelle synthèse de benzo(b)furannes, thiophènes et sélénophènes substitués en position 2 par un groupement alcoyle ou aryle. Cette voie d'accès originale à de tels hétérocycles est basée sur la cyclisation d'éthers (O, S, Se) portant en position ortho un groupement acétonyle ou phénacyle. Nous examinons également les possibilités de généralisation d'une telle réaction.
Mechanism of Bromine Oxidations: II. Kinetics of Oxidation of Isobutyraldehyde by Bromine in Aqueous Solution
Authors: Kudesia V. P. 
Published: September 2010

AbstractThe Kinetics of Oxidation of Isobutyraldehyde by bromine in Aqueous solution has been studied. The reaction is found to be of the first order with respect to isobutyraldehyde and first order with respect to moleculer bromine. The various activation parameters have been calculated. A hydride abstraction mechanism based on the results of deuterium isotope effect has been suggested.
NMR‐experiments on Acetals: XXII [1]. Conformational Equilibria in Trans‐4,6‐Disubstituted‐1,3‐Thioxanes
Authors: Gelan J. , Anteunis M. 
Published: September 2010

AbstractWith the use of a previously developed method [1] based on (temperature dependent) shift parameters of AB spin systems, the thermodynamic quantities controlling conformational equilibria in trans‐4‐Me‐6‐alkyl‐1,3‐thioxanes have been computed (table 1). The conformations with axial substitution next to the sulphur atom are always in excess. The total energy differences are the result of each time a constant enthalpy, but a variable entropy contribution, the latter in disadvantage of the conformation with the (hindered) axial substituent at the oxygen side. These results are discussed in the light of the previously reported special ring shape of thioxanes [6].
Effet de Solvant sur L'équilibre Prototropique de la 3,4‐Diméthyl‐Isoxazoline‐5‐one
Authors: Maquestiau A. , van Haverbeke Y. , Muller R. N. 
Published: September 2010

AbstractIn the present work, the solvent effect on the equilibrium between the three potential CH, NH and OH forms of the 3,4‐diméthyl‐isoxazolin‐5‐one has been studied quantitatively by N. M. R, I. R. and U. V. spectroscopy. The aromatic OH form being absent, an equilibrium takes place between an associated NH form and free NH and CH forms. The CH structure is the most stable but hydroxylic and basic aprotic solvents favour the NH form.The dielectric constant of the solvent seems to have but a negligible effect.
Étude par Diffraction de Rayons X de Complexes D'Halogénures Alcalins et de Molécules Organiques: VIII. Structure de Lil.2(NH2)2CO
Authors: Verbist J. , Meulemans R. , Piret P. , van Meerssche M. 
Published: September 2010

AbstractThe structure of Lil.2(NH2)2CO has been determined by three‐dimensional X‐ray analysis. Space group C2/c; a = 11.40, b = 14.38, c = 5.23 Å, β = 101.5° Z = 4.Li+ is surrounded by four O each urea being linked to two Li+. The chains (Li+.2 urea)n so formed are held together by means of N‐H…I− bonds.
NMR Experiments on Acetalsl XXVI. Influence of β‐Substitution on Geminal Coupling Values in 1,3‐Dioxanes
Authors: Swaelens G. , Anteunis M. , Tavernier D. 
Published: September 2010

AbstractThe influences of β‐substituents–either in equatorial or in axial positions–on the numerical value of 2J(H‐2) (the geminal coupling J(OCH2O)) in 1,3‐dioxanes, have been scrutinized. Influences on 2J(H‐2) by the nature and electronegativity of the substituents seem to depend on the orientation of these substituents. Equatorial substituents cause composite influences, alkyl groups leading to an almost independent constant value for 2J(H‐2) = −6.2 cps.Suitable equatorial ρ‐substituted phenyl derivatives show a numerical decrease with increasing electrodonating capacity (range 6.2‐6.5 cps) however. The same, but more pronounced trend is found for the axial substituents.
Spectroscopie Ultraviolette D'Une Série D'Aldéhydes Dérivés D'Hydrocarbures Polycycliques Aromatiques: I. Étude Théorique de la Fréquence de la Transition 1La et de la Position Des Bandes De Transfert de Charge Avec le Tétracyanoéthylène
Authors: Figeys H. P. , Wilmet‐Devos B. 
Published: September 2010

AbstractThe frequencies of the 1La transitions of polycyclic aromatic aldehydes are related linearly to the energy gap between the highest bonding and the lowest anti‐bonding orbitals in these molecules calculated by an iterative Hückel‐L. C. A. O.‐method. Solutions of the same derivatives and tetracyanoethylene in chloroform show a new absorption band which may be attributed to a charge‐transfer complex. A linear relation is found between the energies of these bands and the highest occupied molecular orbital of the aldehydes.
Nouvelle Voie D'Obtention Rentable du Nitro‐5 Benzo(b)Sélénophène Comparée a D'Autres Méthodes
Authors: Marechal G. , Ruwet A. , Renson M. , Buu‐Hoi N. P. 
Published: September 2010

AbstractThe previously known synthesis of 5‐nitro benzo(b) selenophene is only convenient for the preparation of small quantities. In order to obtain this compound in great quantity for heterocyclic chemistry, new ways have been investigated. They are limited by the present difficulty to reach 2‐methylseleno‐5‐nitro‐benzaldehyde. However the Knoevenagel's reaction applied to 2‐bromoseleno‐5‐nitro‐benzaldehyde itself prepared in two steps from 2‐chloro‐5‐nitrobenzaldehyde is shown to be a new efficient procedure for the synthesis of 5‐nitro‐benzo(b)selenophene. The latter provides 5‐animo‐benzo(b)selenophene and other derivatives.
Organometallic Compounds. XXIV. () Determination of all the possible isomerization reactions of coordination complexes by the use of permutations
Authors: Gielen M. , Vanlautem N. 
Published: September 2010

AbstractPermutations may be used to describe the transformations of a given complex MLn into one of the n!/hr, possible isomers.The determination of the n! possible permutations gives all the isomerization paths of this complex occuring by nonbond‐rupture mechanisms.This is applied to the case of four; five‐ and six‐ coordinate structures and might be applied as well to higher coordination numbers.
Indole Alkaloids: XXIV Unusual behaviour of voachalotine and derivatives in the von braun degradation
Authors: Lampe‐Tirions M. , Kaisin M. , Pecher J. 
Published: September 2010

AbstractThe cyanamides obtained by the von Braun degradation of voachalotine (VIII) and derivatives are all bromine free compounds, formed by a “benzylic” cleavage of the C3N4 bond. The alternatively conceivable allylic cleavage of the C21N4 bond was not observed.The derivatives I, III and VI (not containing an OH group) yielded cyanamides comprising a Δ 3,14 double bond conjugated to the indole system. This was not observed in the degradation of voachalotine (VIII): the corresponding cyanamide IX contained a cyclic ether, formed by an intramolecular attack of the alcohol group on C3. The cleavage of the C3‐N4 bond can also be assisted by an inter‐molecular process involving alcohols added to the solvent (chloroform). In the latter conditions indeed good yields of the 3‐alkoxycyanamides XII, XIII, XIV and XV were obtained.
Some Constituents of Lycopodium Inundatum L
Authors: Braekman J. C. , Hootele C. , Ayer W. A. 
Published: September 2010

AbstractThree new alkaloids—inundatine [V], isoinundatine [VI] and dehydrolycopecurine [VII]—have been isolated from Lycopodium inundatum L. together with methyl p‐coumarate [I], α‐onocerine [II], lycopodine [III] and lycodoline [IV].
Structure Moléculaire et Cristalline du Bromo‐5 Tetraphényl‐1,2,3,4 Cyclopentadiène
Authors: Evrard Guy , Piret Paul , van Meerssche Maurice 
Published: September 2010

AbstractThe structure of bromo‐5 tetraphenyl‐1,2,3,4 cyclopentadiene has been determined by X‐ray analysis. Space group: P212121, Z = 4; a = 8.51, b = 41.99, c = 6.17 Å. The molecule has nearly mirror‐symmetry. The angles between the mean planes of the phenyls and that of the central ring are ϕ(1) = 30.5°, ϕ(2) = 66.5°, ϕ (3) = −69.0° and ϕ (4) = −33.9°.
A Convenient Synthesis of Chloronitrobenzonitrile Isomers and Homologs
Authors: Grivsky E. M. 
Published: September 2010

AbstractA new, direct method for the synthesis of 10 position isomers of chloronitro‐benzonitrile and some homologs from the corresponding benzoic acids and methane‐sulfonamide in the presence of phosphorus pentachloride has been developed and exploited. This modification has proved to be more generally applicable than the previously available procedure usingp‐toluenesulfonamide, and the products were obtained in amounts approaching the theoretical yields. A cyclic mechanism for a transformation leading to the formation of these aromatic nitriles is postulated.
Heterogeneous Photosensitization. Part II. Kinetics of the Gas‐Phase cis‐trans isomerization of 1,3‐pentadiene sensitized by 1,3‐cyclohexadiene photopolymer[1]
Authors: de Maré G. R. , Fontaine M‐C. , Goldfinger P. , Huybrechts G. , Sapir M. 
Published: September 2010

AbstractThe gas‐phase cis‐trans isomerization of 1,3‐pentadiene, photosensitized by a thin polymeric film, has been studied at λ ≥ 300 mμ and 50°C in the pressure range 5 to 200 torr. The observed photostationary state and the influence of substrate pressure on the rate of isomerization suggest a reaction mechanism similar to that proposed for triplet photosensitized isomerizations in solutions[2].
Effect of the pH on the Collapse Pressure of Fatty Acid Monolayers Evaluation of the Surface Dissociation Constant
Authors: Joos P. 
Published: September 2010

AbstractThe collapse pressures of stearic and cholanic acid monolayers were measured as a function of pH. The surface phase was treated as a mixture containing acid and soap, and our previously outlined theory concerning the collapse of a mixed monolayer was applied to it. From this results, a surface dissociation constant, different from the bulk value, can be obtained. The experimental data are in good agreement with the outlined theory.
Mesure du Potentiel Standard du couple Pu(III)/Pu(O) Dans L'Eutectique LiCl‐KCl Entre 400 et 600°C
Authors: Not L. Marti , Duyckaerts G. 
Published: September 2010

AbstractWe have measured the standard potential of the system Pu(III)/Pu(0).vs. a Ag/AgCl reference electrode in a LiCl‐KCl eutectic.The values of the standard potential are reported between 400 and 600°C and compared with the previous determinations carried out with U(III) and Np(III). The Nernst equation is also plotted at several temperatures.
Étude RPE des Radicaux Cyclopentyles Piégés dans un Mélange de Cyclopentane et de Néohexane
Authors: Fauquenoit C. , Dodelet J. P. , Claes P. 
Published: September 2010

AbstractNous avons étudié par RPE le radical cyclopentyle formé par irradiation à 77°K de mélanges vitreux de cyclopentane et de néohexane. Le spectre du radical cyclopentyle est mieux résolu que celui provenant de l'Irradiation du cyclopentane pur. Deux configurations différentes du radical cyclopentyle ont été invoquées pour interpréter le spectre RPE observé.
The Thermodynamics of Ionization in Ethanol‐Water Mixtures. II. Ortho Substituted Anilinium Ions
Authors: van De Poel W. 
Published: September 2010

AbstractThermodynamic parameters of ionization, δHi0 and δG, i0 were measured at 25°C for a number of ortho substituted anilinium ions in water and in highly aqueous ethanol (X = 0.9).Larger endothermic maxima were found for δHi0 and δSi0 on going from water to ethanol‐water as solvent than for the corresponding 3‐ and 4‐substituted isomers. The results are treated in terms of the structure influencing effect of ions and neutral molecules in aqueous solutions, and in terms of Heplers “internal”; and “external”; contributions to ionization parameters.A value of β, the proportionality constant between δHext and δSext, was calculated with the aid of the experimental results. This β value is not significantly different from the one found previously for 3‐ and 4‐substituted anilinium ions.
Kinetics of Bromination of p‐Toluidine
Authors: Kudesia V. P. 
Published: September 2010

AbstractThe kinetics of oxidation of p‐toluidine with aqueous bromine has been investigated at 25°C. Evidences have been provided to establish that the molecular bromine is the principal oxidising agent. There is an isotope effect k2(H2O)/k2(D2O) = 1.36 which is found to be secondary exhibiting that the mechanism does not represent slow proton loss in rate determining step.
The Electrical Resistivity of Rhombohedral NiS
Authors: Pauwels L. J. , Maervoet G. 
Published: September 2010

AbstractElectrical resistivity measurements are carried out from 4,2 K to 800°K on rhombohedral NiS powder compacts, sintered at different temperatures. The effect of sintering is exposed. NiS γ appears to be a metallic conductor with a room temperature resistivity of 9.2 × 10−5 ωcm and a temperature coefficient of 3.6 × 10−3 deg−1. In the high‐temperature range ρ is proportional to T; in the low‐temperature range (30‐45°K) a T3.84‐law is followed. It is possible to derive a value of about 300°K for the characteristic temperature Θ. At 388°C a discontinuity in the resistivity is found, caused by the γ → β phase transformation.
Les Sulfates Basiques Mixtes de Cobalt et de Zinc
Authors: Lecocq R. , Glibert J. , Breckpot R. 
Published: September 2010

AbstractThe stable basic sulfates of Co and Zn, as obtainable by NaOH at 20°C, are respectively tetra‐ and tribasic.The mixed basic salts in equilibrium with mixed solutions of the sulfates show a considerable potential retention for Zn corresponding with a depletion of this element in the solution.Up to 25 at. %, Zn can be held in the hydroxyl sites of the tetrabasic Co structure with a partial bonding energy per atom 1000 times greater than in the pure tribasic salt of Zn.With larger amounts of Zn, the basicity is lowered and with 40 at. % of Zn the tribasic lattice appears. In this, Co is preferentially held in the sulfate sites.
Calorimetric Determination of ΔH and ΔS Involved in the Complex Formation of Some Metals with 2‐Substituted Pyridine Derivatives
Authors: Goeminne A. M. , Eeckhaut Z. 
Published: September 2010

AbstractThe enthalpy changes involved in the complex formation of Cu(II), Ni(II), Co(II), Zn(II), Cd(II) with several 2‐substituted pyridine derivatives have been determined by direct calorimetric measurements at 25°C, in 0,5 M KNO3 solution. From these and the stability constants of the complexes, δS has been calculated. Changes in δH and δS are discussed in terms of hydrational, inductive and steric effects.