bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Friedel‐crafts acylation reaction. II. A study of the Hammett relationship in the Friedel‐crafts benzoylation of toluene with substituted benzoyl chlorides.
Authors: Slootmaekers P. J. , Rasschaert A. , Janssens W. 
Published: September 2010

AbstractDans l'étude de l'effet de substituant dans la réaction d'acylation du toluène par des chlorures de benzoyle substitués en méta ou en para, on constate que les réactivités de ces derniers, relatives au chlorure de benzoyle non substitué, ne sont pas corrélées par l'équation de Hammett.Il est montré que la distribution des isomères dans le produit de réaction de chaque membre de la série de réactions est pratiquement constante, et que la série de réactions est caractérisée par une relation isocinétique. Par ailleurs, pour expliquer la déviation à l'équation de Hammett, on ne peut invoquer ni une différence dans la polarité du milieu réactionnel pour chaque membre de la série de réactions, ni une dépendance de la valeur de la constante des substituants de Hammett de la nature du solvant employé (le chlorobenzène).Les résultats sont alors discutés en termes d'une interaction mésomère entre substituant en para et le centre réactionnel. Quoique cette explication semble justifiée, il est montré que ces faits peuvent tout aussi bien provenir d'un léger changement dans le mécanisme de la réaction pour les différents termes de la série de réactions.La constante de Hammett du groupement para‐cyclohexyl a été déterminée par titration potentiométrique, et est égale à –0,18 ± 0,03 unités sigma.
Moments Dipolaires D'Alcools Aliphatiques Normaux dans le Cyclohexane
Authors: Clerbaux Th. , Zeegers‐Huyskens Th. 
Published: September 2010

AbstractOne measures the square of the dipole moment of different aliphatic alcohols in cyclohexane solution. The fraction of cyclic molecules presents a maximum which increases with the length of the aliphatic chain. For a given alcohol this maximum is situated at about the same formal concentration than in carbon‐tetrachloride, but is more pronounced; this indicates that this last solvent prevents the cyclisation.The comparison with the results of infrared spectrometry, nuclear magnetic resonance and partition coefficients enable us to show that the average number of cyclic molecules in a chain is greater than three for butylalcohol, at 25°C, at formal concentrations situated between 0, 5 and 2 moles/liter.
NMR experiments on ketals VI. PMR spectra of alkyl substituted 1, 3‐dioxanes with rigid or anancomeric structures
Authors: Anteunis M. , Tavernier D. , Borremans F. 
Published: September 2010

AbstractPMR coupling values and shifts of twenty three 1, 3‐dioxanes with rigid structure have been determined. The coupling data are in accordance with a chair conformation which is less buckled than that of cyclohexane derivatives. It is necessary to take into account the recently recognized influence of free electron pair orbitals on gem and vicinal coupling phenomena (11). An exceptional situation for the equatorial proton on C5is found, not only for the couplings of this proton, but also for its shift. An influence caused by the shielding of the oxygen atoms (O1and O3), their (equatorial)p‐orbitals overlapping with the C‐H orbital, has been shown to be responsible for coupling value variations.
Isosélénochromannone et Cation Séléna‐2 Naphtalénium
Authors: Renson M. , Pirson P. 
Published: September 2010

AbstractNous décrivons la préparation de l'isosélénochromannone et du perchlorate de séléna‐2 naphtalénium. Le spectre ultra‐violet et le pK de ce cation ont été déterminés et comparés à ceux de son isologue sulfuré, et de l'isomère sélénie en position 1.
Alcaloïdes Indoliques XI. Configuration absolue de la voacarpine
Authors: Braekman J. C. , Kaisin M. , Pecher J. , Martin R. H. 
Published: September 2010

AbstractA correlation between voacarpine (I) and 16‐épivobasine (II) establishes the absolute configuration at C5and C15and the geometry of the ethylidene side chain in voacarpine and in Nβ‐methylvoacarpine (VI). This last base is shown to be identical with Le Men's vincadiffine.
The humulinic acids VI. Dihydro‐, dihydrodeoxo‐ and further hydrogenated derivatives
Authors: Lepoivre A. , Alderweireldt F. , Anteunis M. , Verzele M. 
Published: September 2010

AbstractThe hydrogenation products of humulinic acids A and B are described and mechanisms for the reactions are advanced. The isolated 2, 4‐diisopentylcyclo‐pentane‐1, 3‐dione (X), trans‐ 1, 3‐diisopentyl cyclopentane (XV) and 2, 5‐diiso‐pentyl‐2‐cyclopenten‐1‐one (XII) have probably not been isolated before.
An infrared study of ‐conco‐ structures
Authors: Seth Paul Willem A. , Demoen Paul J. A. 
Published: September 2010

AbstractThe infrared carbonyl frequencies of a variety of hydantoins were collected. It was found that the high frequency band can be attributed to the CO group in the 2‐position. Acylation of the 1‐N or 3‐N atom probably effects a rehybridization of the N atom by which the s character of the adjacent CO bonds is increased.
Mean amplitudes of vibration and bastiansen‐morino shrinkage effects in some linear symmetrical four atomic molecules
Authors: Nagarajan G. , Lippincott E. R. 
Published: September 2010

AbstractFor linear symmetrical four atomic molecule possessing a D∞h symmetry, analytical expressions for the mean‐square amplitude matrices, generalized mean‐square amplitudes (mean‐square parallel amplitudes, mean‐square perpendicular amplitudes and mean cross products) and normal frequencies are given. A brief outline of the Bastiansen‐Morino shrinkage effects has been given. The computed numerical values of the mean‐square amplitudes of vibration, generalized mean‐square amplitudes, mean amplitudes of vibration and Bastiansen‐Morino shrinkage effects at the temperature T = 0, T = 298°K and T = 500°K are reported and discussed for the 10B2O2, Al2C2, Al2C2, Al2O2, Ga2C2 and Ge4 molecules.
Étude du Mécanisme de la Réaction de Formation de Semicarbazones en Solution Méthanolique Mise en Évidence D'Une Réaction parasite et Origine du pH Optimum de Réactivité
Authors: Figeys H. P. , Nasielski J. 
Published: September 2010

AbstractThe rate of formation of 2‐naphtaldehyde semicarbazone in methanol solution is dependent on the pH and passes through a maximum. It is shown that in acidic media (pH < pHopt), the reaction undergoes specific and general acid catalysis, and that an important side reaction occurs (formation of the corresponding acetal). The rate's maximum is quantitatively accounted for by the rate equation found for acid media and its validity apparently extends beyond this optimum pH. For more strongly alcaline solution, it is necessary to assume a change of mechanism (or rate determining step); the position of the optimum pH might be influenced to a variable degree by this modification, depending on the structure of the aldehyde.
Étude du Comportement D'Isomères Géométriques Sous L'Impact Électronique. VII. Sur la Stabilité Relative des Liaisons Axiales et Équatoriales dans des Hydrocarbures Cyclohexaniques Substitués
Authors: Natalis P. 
Published: September 2010

AbstractMass spectrometric data on eighteen pairs of geometrical isomers of hydrocarbons containing a cylcohexane ring have been examined. It is shown that in all cases the fragment ion (P‐X)+, corresponding to the loss of an alkyl group X from the molecular ion P+, is more abundant in isomers where the C(ring)–C(X) bond is equatorial than in those where the same C–C bond is axial. As a result, an equatorial C(ring)–C(X) bond appears to be less stable under electron impact than an axial C(ring)–C(X) bond in all the compounds examined.
Étude Spectroscopique de Molécules Halogénées. VI. Analyse Conformationnelle en Série Cyclodécanique
Authors: Maes M. , Ottinger R. , Reisse J. , Chiurdoglu G. 
Published: September 2010

AbstractThe infra‐red solvent‐shift method has been used in order to determine the carbon halogen stretching vibrations v(C‐Hal) in the I.R. spectra of cyclode‐cane chloride, bromide and iodide.This procedure leads to the attribution of a number of bands in agreement with the previsions based on the geometry of cyclodecane ring obtained from X rays data.
Essais de Chloration Dirigée. VII. Photochloration de Composés Aliphatiques en Présence de Solvants
Authors: Rouchaud J. , Bruylants A. 
Published: September 2010

AbstractLes acides aliphatiques et leurs dérivés fonctionnels donnent, par chloration photochimique, un mélange d'isomères monochlorés. Les répartitions obtenues jusqu'ici par attaque du chlore libre sur la molécule organique ont été coordonnées par une équation qui tient compte des effets inducteurs et de résonance agissant sur le centre réactionnel. Les répartitions relatives aux nitriles valérique et isovalérique, qui n'étaient pas ou mal connues, ont été déterminées dans ce travail par chromatographie en phase gazeuse; elles confirment la validité de la relation précédente.La sélectivité de l'attaque du chlore sur la molécule organique augments considérablement en présence de solvants tels que le benzène, le chloroberizène, le nitrobenzène et le sulfure de carbone. Ainsi, dans le cas de l'isovaléronitrile, dissous dans le benzène 8 m.l−1à 30°C, 76,5% d'isomère β‐chloré sont formés, contre 49% seulement en l'absence de solvant «actif».En photochlorant une série de nitriles et de dérivés, à différentes concentrations en benzène, nous avons constaté que, des deux constantes de réaction relatives aux effets inducteurs (ρ*) et de résonance (h), c'est le dernier qui varie le plus. Il semble done que c'est la stabilisation par résonance des radicaux qui est accentuée par le solvant.
Essais De Chloration Dirigée IX. Photochloration des composés aliphatiques par agents chlorants
Authors: Rouchaud J. , Bruylants A. 
Published: September 2010

AbstractQuatre agents chlorants, moins réactionnels que le chlore libre, ont été expérimentés sur l'isovaléronitrile (IVN).Le chlorure de trichlorométhane‐sulfonyle (CSO2Cl4), agissant à 30°C, donne 92% d'isomère β‐chloré, 7% de γ‐chloré et 1% seulement d'α‐chloré. En faisant la réaction à trois températures (30, 60 et 90°C), on peut mesurer la différence d'énergie d'activation apparente dans la substitution des hydrogènes β et γ: cette valeur atteint 5.100 cal.m−1.Le chlorure de trichlorométhane‐sulfényle (CSCl4) conduit à 71% d'isomère β‐chloré, 27% d'isomère Y‐chloré et 2% d'α‐chloré (35°C): la différence d'énergie d'activation apparente, mesurée entre 0 et 70°C, entre hydrogène β et γ n'est que de 1.600 cal.m−1. Tandis que la dilution du milieu par CCl4 ne modifie pas la répartition, la dilution par le benzène fait passer la répartition en β à 95%.Le dichlorure de soufre (SCl2) chlore l'IVN, sous irradiation U. V.; 86% de β‐chloré, 13% de γ‐chloré et 1% de α‐chloré sont formés à 30°C: la différence d'énergie d'activation apparente entre hydrogène β et γ atteint 6.500 cal.L'emploi de benzène, comme solvant, provoque la formation de 100% l';isomère β‐chloré (20°C).Un essai avec le monochlorure de soufre révèle 84% de β‐Cl, 15% de γ‐Cl et 1% de α‐Cl.Des photochlorations avec les deux chlorures précédents ont été également réalisées en irradiant le système IVN‐agent chlorant à différentes longueurs d'onde: c'est ainsi que 100% d'isomère β‐chlorés ont été également obtenus par illumination par la raie D du sodium (5.880 A°) au lieu des 3.000 à 4.500 A° habituels.
Nouvelle Synthèse D'Oxadiazoles‐1, 2, 4 Par Condensation D'Amidoximes Et D'Amides
Authors: Moussebois C. 
Published: September 2010

AbstractThis communication reports a new synthesis for unsubstituted, mono or disubstituted 1, 2, 4‐oxadiazoles. These substances are obtained in one step by heating the salt of an amidoxime with an amide.By means of this reaction, it is possible to obtain directly 1, 2, 4‐oxadiazoles substituted by groups such as ‐OH or ‐CONH2.
Halogen Substituted 1, 3‐Cyclohexanediones IV. Reaction OF 2, 2‐Dichloro‐1, 3‐Cyclohexanediones With Sodium Methylate
Authors: Schamp N. 
Published: September 2010

AbstractBy treatment with sodium methylate 2, 2‐dichlorodimedone is methanolysed to give methyl 4‐dichloroacetyl‐3, 3‐dimethylbutyrate, which further undergoes a Favorskii rearrangement, leading to a normal Favorskii rearrangement product, dimethyl cis‐4, 4‐dimethyl‐α‐hydromuconate and an abnormal one, dimethyl 3, 3‐dimethyl‐2‐chloromethylglutarate. 5‐monosubstituted 2, 2‐dichloro‐1, 3‐cyclohexanediones give the same methanolyses, but only the normal Favorskii rearrangement is observed.
Reaction in Liquids at Critical Conditions Decomposition of Benzoyl Peroxide
Authors: Touzard B. , van Tiggelen A. 
Published: September 2010

AbstractThe critical conditions for explosivity, which have been derived theoretically by Adler and Enig, are tested in the case of a liquid reacting system (decomposition of benzoyl peroxide in cyclohexanol solutions). A good agreement is observed between experimental data and theory.
Long Range Phenomena. IV (1): The PMR‐spectra of 2‐halo‐3, 3, 5, 5‐tetramethyl‐cyclohexanone. Long range couplings not following “M” patterns
Authors: Anteunis M. , Schamp N. , De Pooter H. 
Published: September 2010

AbstractDouble irradiation experiments and solvent dependence studies prove that “non‐classical” long range phenomena occur, i.e. 4J2e. 6a, 4J2e, 4a, 4J4a, 6a (Ia and IIa); 4J2a, 6e, 4J4a, 6a (Ib and IIb).The criterion of the “Meinwald” disposition in assigning the nature of protons involved in long range coupling must be used with extreme care.In DMSO‐d6 4J4a, 6a for Ib is more than twice the “classical” 4J4e, 6e coupling value, the former coupling not occurring across an sp2 hybridized atom.Even small solvent changes influence long range couplings. Thus for Ia no 4J2e, 4a is observed in chloroform, but it is 0.7 cps in carbon tetrachloride.
Étude Théorique Des Dérivés Azotés Des Hydrocarbures Conjugués Alternants I. L'évaluation semi‐empirique des paramètres
Authors: Leroy G. , Aussems C. , van Remoortere F. 
Published: September 2010

AbstractSome characteristic parameters of the nitrogen atom are evaluated semi‐empirically in the expressions of the LCAO‐MO method, using the first singlet‐singlet transition energy of pyridine and results previously obtained in a study of conjugated hydrocarbons.
Substitution électrophile aromatique. VII. Étude de l'étape déterminants de l'iododéstannylation par effet de solvant
Authors: Nasielski J. , Buchman O. , Grosjean M. , Hannecart E. 
Published: September 2010

AbstractThe reaction of phenyltrimethyltin with iodine is faster than that of phenyltriisopropyltin, but the ratio of the second order rate constants for both compounds is however the same in methanol and in isopropanol. Since isopropanol is less nucleophilic towards tin than methanol, it is concluded that the rate‐determining step in this electrophilic aromatic substitution is the attack by the reagent, and that the breaking of the carbon‐tin bond is a fast, kinetically non significant step.
The mechanism of heterogeneous electron transfer
Authors: de Hemptinne X. 
Published: September 2010

AbstractThe theories of R. Marcus and of Levich for electron transfer reactions are criticised. Electron exchange current is calculated on the basis of a time dependent perturbation theory, by using a simple model. Distortions introduced in the theory by oversimplification of the model are discussed. In the resulting equation for the exchange current, the exponential term is identical to the one of the two mentioned authors. The preexponential term is different. A class of electrode reactions is discussed for which the kinetics are completely different. In all cases, no distinction may be done between adiabatic and non‐adiabatic reactions.
Burning velocities in mixtures of methyl alcohol, formaldehyde or formic acid with oxygen
Authors: de Wilde E. , van Tiggelen A. 
Published: September 2010

AbstractA comparative experimental study of flames propagating in mixtures of oxygen with methyl alcohol, formaldehyde or formic acid has been made. The results have been compared with those obtained in a previous work on methane‐oxygen flames and show a remarkable similarity. A kinetic interpretation is proposed.
Étude Théorique Des Dérivés Azotés Des Hydrocarbures Conjugués Alternants III. Les Dérivés Polyazotés Des Hydrocarbures Alternants
Authors: Leroy G. , van Remoortere F. , Aussems C. 
Published: September 2010

AbstractThe method described in the two previous papers of this series is further extended to poly‐aza‐derivatives of the conjugated hydrocarbons by fitting the integral (N+:N N) to the first singlet‐singlet transition of pyridazine. Results are in satisfactory agreement with experiment.
Sur La Microsynthèse Quantitative Du Polyphényle
Authors: Peters J.M. , Guillaume M. , Del Fiore G. 
Published: September 2010

AbstractUne technique de microsynthèse de polyphényle a été mise au point. L'étude systématique des conditions de synthèse a permis d'obtenir un rendement de 100% (calculé à partir du benzène de départ).Ces travaux constituent la première étape de la recherche et de la préparation d'un matériau organique thermiquement stable, de très haute activité spécifique en tritium, susceptible de constituer une cible tritiée en vue de la production de neutrons de 14 MeV, selon la réaction nucléaire 3H (d, n)4He.
Application of the Taft Equation to the Ionisation Constants of Negatively Substituted Monoalkylhydrazines
Authors: Pollet R. , Vanden Eynde H. 
Published: September 2010

AbstractThe ionisation constants of perfluorinated and other negatively substituted monoalkylhydrazines have been determined in water, and plotted against the Taft polar substituent constants. A reaction constant of ‐ 2.36 is obtained, providing evidence that, contrary to not negatively substituted monoalkylhydrazines, protonation takes place at the terminal amino group. Perfluoroalkylsubstitution lowers the basicity of hydrazine in such a way that the basicity order of phenyl‐hydrazine is reached. The obtained results allow a discussion about the effectiveness of transmission of electronic effects through an interposed ‐NH‐ unit.
A Spectrophotometric Study of the Palladium (II) Complexes of N, N′ ‐Bis (2‐Sulphoethyl) Dithio‐Oxamide)
Authors: Goeminne A. , Herman M. , Eeckhaut Z. 
Published: September 2010

AbstractIt has been proved that N, N′‐bis(2‐sulphoethyl)dithio‐oxamide forms with palladium different complexes, dependent upon the pH of solutions and the excess of metal ion.In strong perchloric acid the following complexes are formed: Pd(H2L)22+, (Pd.H2L)p2p+and (Pd2.H2L)4+.In strong hydrochloric acid complex formation takes place by replacement of chloride ions from the saturated complex PdCl42−. In this way the following complexes are formed: PdCl2.H2L and Pd(H2L)22+.With increasing pH all these complexes expel protons: so in the pH range 0–3 the mononuclear complex can be represented as PdHL.H2L+and in the pH range 3–10 as Pd(HL)2pwhereas the polynuclear complex in the latter medium can be represented as (PdL)p. An estimation of the stability constants of the mononuclear complexes has been made.
Halogen Substituted 1,3‐Cyclohexanediones V. Brominated Cycloalkanones From the Reaction of 2,2‐Dibromodimedone With Sodium Acetate [1]
Authors: De Pooter H. , Schamp N. 
Published: September 2010

AbstractBy reaction with sodium acetate in hot glacial acetic acid, 2,2‐dibromodimedone (VII) is transformed into a mixture of 2‐bromo‐4,4‐dimethyl‐2‐cyclopentenone (IX), 2,3‐dibromo‐4,4‐dimethyl‐2‐cyclopentenone (X), 3‐acetoxy‐2‐bromo‐5,5‐dimethyl‐2‐cyclohexenone (XI), 2‐bromodimedone (VIII), 2,4‐dibromodimedone (XIII) and 3‐bromo‐6,6‐dimethyl‐l,2,4‐cyclohexanetrione (XII).A mechanism is proposed, based on this “acetate reaction” with possible intermediates such as VIII, XIII, 2,2,4‐tribromodimedone (XIV) and 2,4,4‐tribromo‐dimedone (XV). XIV and XV were prepared in high yield from the easily accessible 2,4‐dibromodimedone (XIII) and 2,2,4,4‐tetrabromodimedone (XXII).Methods for the specific synthesis of cyclopentenones IX and X, cyclohexanetrione XII and new halogenated dimedones are described.
Dielectric Constant of Carbon Tetrachloride and Tertio‐Butanol Mixtures
Authors: van Loon R. , Dauchot J. P. , Bellemans A. 
Published: September 2010

AbstractThe static dielectric constant of CCl4, (CH3)3COH and their mixtures has been measured in the liquid region between 0 and 50°C. Applying the Onsager‐Kirkwood‐Fröhlich theory and extrapolating to infinite dilution, we found 1.74±0.04 debye for the permanent dipole moment of the (CH3)3COH molecule. At intermediate concentrations there is clear tendency to the formation of complexes of alcohol molecules with their dipoles antiparallel. At high concentrations complexes with a parallel dipolar alignment predominate.
NMR Experiments on Ketals. XIV Conformation of 1,3‐Thioxane and 1,3‐Dithiane. Equilibrium of 4,6‐Dimethyl‐1,3‐Thioxane
Authors: Gelan J. , Anteunis M. 
Published: September 2010

AbstractThe “aliphatic” region (C4‐C5‐C6) of the heterocyclic ring systems of 1,3‐thioxanes and 1,3‐dithianes is less flattened than in 1,3‐dioxanes. However, thioxanes and dithianes are more readily deformed by substitution than 1,3‐dioxanes, resulting in a greater spread of “typical” vicinal coupling constants.The 1,3‐thioxane system is furthermore asymmetrically distorted (cfr. X) and as a consequence the axial bonds on C4 and C6 are not parallel to each other. Therefore an axial methyl group next to the sulphur atom (Me‐6; thioether side) is sterically less compressed than the one at the ether side (Me‐4) and thus the amount of IVa in the equilibrium IVA ↽ VA (4,6‐trans dimethyl‐1,3‐thioxane) is found to be ca. 85%.
The Aroma of Hops III. The Occurrence of Diterpenes in Hop Oil
Authors: Lammens H. , Verzele M. 
Published: September 2010

AbstractTwo diterpene hydrocarbons have been isolated from hop oil. One is camphorene, the other is a hitherto unknown camphorene isomer. These terpene hydrocarbons, now called para and meta camphorene were not signalled before in hop oil.
Activité Catalytique En Oxydation Des Zéolithes D'Éléments De transition
Authors: Rouchaud J. , Sondengam L. , Fripiat J. J. 
Published: September 2010

Abstractn‐Hexane has been oxidised batchwise in the liquid phase by molecular oxygen at 160 °C and under a total pressure of 25 atm. High yield in carboxylic acids, and especially acetic acid are obtained. The ion‐exchange zeolithes 13 × 60–120 mesh of manganese, nickel and cobalt (about 0.65 gr% of the transition element in the reaction medium, and about 8 gr% of heavy metal on the 35 gr% water containing zeolithe) increase the rate of consumption and the conversion of n‐hexane. The zeolithes of nickel and manganese present, relatively to the zeolithe of cobalt, higher selectivities toward the formation of acetic acid. The intensity and the specificity of the catalytic activity of the zeolithes of transition elements has been related to the strong electronic inductive effects produced by the zeolithic cristalline cavities on the transition cation.
Oxydation Du Para‐Xylène Liquide Catalysée Par Les Zéolithes Chargés D'Éléments De Transition
Authors: Rouchaud J. , Mulkay P. , Fripiat J. 
Published: September 2010

AbstractPara‐xylene dissolved in acetic acid (acetic acid/para‐xylene = 4.4 g/g) has been oxidised by oxygen at 165°C., under a total pressure of 32 atm and a partial pressure of oxygen of 25 atm. The main products are the para‐toluic and terephtalic acids. Catalytic amounts of cobalt and manganese ion‐exchange zeolithes 13 X lead to high conversions of para‐xylene and selectivities in terephtalic acid. The best results are obtained with a mixture of the manganese and cobalt zeolithes. The catalytic activities and the magnetic susceptibilities of the zeolithes of transition elements have been related. The results show the strong activation exerted by the zeolithic ligand field on the catalytic activities of the transition cations.