bluuebunny/crossref_metadata_2025 huggingface dataset:
The theoretical study of (2 + 2) cycloadditions ‐ the concerted ethylene dimerizations reaction
Authors: Burke Luke A. , Leroy Georges
Published: September 2010

The (2s + 2a) path for the dimerization of ethylene is found to be high energy valley leading into the (2s+2s) path just after this latter's transition state. A minimal basis set (STO‐3G) ab initio method is employed and supplemented by either a 15 or 55 configuration interaction. The (2s+2a) barrier is found to be 109 (107) kcal/mole with 15 (55) configurations as opposed to 82.5 (82.3) kcal/mole for the (2s+2s) barrier. This is to be compared to the two‐step barrier of 42.4 kcal/mole previously found with STO‐3G and 15 configurations.

It is found that four cis‐substituted ethylenes serving as the antarafacial partners reduce the (2s+2a) barrier as the substituents become stronger electron donors or acceptors. Conversely, the (2s+2s) barrier rises with the strength of the substituent.
Electronic structure and ensemble size effects in hydrocarbon reactions on alloys
Authors: De Jongste H. C. , Ponec V.
Published: September 2010

In this paper, introductory to the Symposium, an attempt is made to summarize and rationalize the available information on the reforming reactions of hydrocarbons on metals and alloys. It is shown that three important aspects of hydrocarbon adsorption, viz. chemisorption bond strength, reactivity towards C‐H bonds and the ability to form multiple bonds with the group VIII metals, are not dramatically changed by alloying. Therefore, various changes due to alloying observed in the selectivity of alloys are ascribed to the availability of ensembles of active sites on the alloy surface (ensemble size effects). It is shown that also on pure metals various intermediates are identified which differ in the number of C‐ atoms and metal‐atoms involved in the formation of activated complexes. By alloying a consistent shift is observed from mechanisms and intermediates requiring big ensembles to mechanisms which can also operate on small ensembles. As a rule mechanisms involving big ensembles are faster. The identity of alloy components in their chemisorption and catalytic behaviour is preserved to a high extent also in alloys and is a more important feature in catalysis than the effects caused by mutual influencing of alloy components.
Adsorption of H2, N2, C2H2 and C2H6 on iridium influence of steps on work function
Authors: Derochette J. M.
Published: September 2010

A probe hole field emission microscope has been used to study the adsorption of different gases on iridium planes and an attempt to establish the role of steps on work function has been made.

The surface potential of the adsorbed species has been shown to be different on stepped planes and on flat surfaces for all gases studied in this work.
Anharmonicity correction and molecular constants of H2Se and D2Se
Authors: Sengodan V , Srinivasacharya KG
Published: September 2010

The anharmonicity correction factors for H2Se and D2Se are estimated by the method of Dennison (1). The potential constants are calculated by means of three different methods; Wilson's F‐G matrix method (2), the kinetic constants method (3) and the L‐approximation method (4)‐using the presently evaluated harmonic frequencies. The potential constants thus obtained are utilised in evaluating the other molecular constants such as compliance constants, mean amplitudes of vibration, inertia defect, Coriolis coupling constants and centrifugal distortion constants. The values of inertia defect and centrifugal distortion constants obtained presently are in good agreement with the experimental values (5,6).
Solution Conformation by1H NMR of the diastereomeric cyclopeptides cyclo‐4‐thiapipecolic acid‐phenylalanine
Authors: Anteunis Marc J. O. , Schrooten Rik , Nachtergaele Willy , Neirinckx Ingrid
Published: September 2010

The diketopiperazines c/L‐(S) Pip, L‐Phe/ and c/L‐(S) Pip, D‐Phe/ have been studied by1H NMR spectroscopy at 360 MHz and the complete analyses have disclosed their solution conformations. Both isomers possess a pronouncedly flattened boat DKP‐ring (puckering of about 10°), and the aromatic side‐chain in both diastereomers are pronouncedly stacked over this ring. Whereas the cis‐L, L isomer is almost exclusively folded (and to a higher degree as in the Pip‐congener) this happens for the trans‐D. L‐isomer only in hydrophilic surroundings. These behaviours fit well with the expected torsions around the (S) Pip‐DKP annelations for a (S) Pip‐chair, and with the idea that next to peptide interactions, hydrophobic interresidue‐stabilisation and sulfur attractive forces may also be important features in folding.
Solubility of thermal synthesized fluorhydroxyapatites
Authors: Verbeeck Ronald M. H. , Khan Rizwan A. , Thun Harry P. , Driessens Ferdinand C. M.
Published: September 2010

Fluorhydroxyapatites were synthesized by solid state reaction at 1000°C. The solubility was determined in diluted phosphoric acid. At pH 4 and 5 a degree of substitution x of OH− by F− ions of only a few percent was sufficient to reduce the solubility by 50%, At pH 6 and 7 very high degrees of substitution were necessary to reach this effect. Addition of F ions to the diluted phosphoric acid had no effect on the solubility in the ranee x > 0.3, but it caused a reduction in solubility with up to 88% for hydroxyapatite at pH 7. Addition of Ca2+ ions to the diluted phosphoric acid had no effect on the solubility of hydroxyapatite (OHA). However, it increased the solubility of fluorapatite (FA) and of OHA ‐ FA solid solutions considerably.
Crystal structure of a double helicene, diphenanthro[4,3‐a; 3′, 4′‐o] Picene
Authors: Marsh Wayne , Dunitz Jack D.
Published: September 2010

The crystal and molecular structure of racemic diphenanthro[4,3‐a; 3′, 4′‐o] picene is described. The molecule has a non‐crystallographic twofold axis of symmetry in good approximation, and the two symmetry‐related hexahelicene‐like halves of the molecule are very similar in structure to hexahelicene itself.
A quantum mechanical study of the mechanism of the enol‐ketone tautomerism
Authors: Klopman G. , Andreozzi P.
Published: September 2010

Quantum mechanical calculations have shown the barrier to intramolecular rearrangement in the keto‐enol tautomerism to be prohibitively high. Instead, the 1‐3 proton shift is seen to proceed much more economically via intermolecular pathways, notably via acid and base catalysis. The reaction profiles for these mechanisms have been calculated. It is generally found that the introduction of only one water molecule into the calculations is not sufficient to model the actual effect of solvent on the enolization equilibria in the catalyzed pathways.

The possibility of protomeric isomerization catalyzed by protic solvents like water was also examined in competition with the formation of the acetal. Interference between the two paths, however, prevented a definitive answer to the question to be found.
Synthesis of fomecin B and flavipin trimethyl ether
Authors: Al‐Mousawi S. M. , Green R. J. S. , McOmie J. F. W.
Published: September 2010

The trimethyl ethers of fomecin B (3,4,5‐trihydroxyphthalaldehyde) and flavipin (3,4,5‐trihydroxy‐6‐methylphthalaldehyde) have been prepared by the thermal decomposition of the selenite esters of the corresponding phthalyl alcohols. Complete demethylation of fomecin B trimethyl ether gave fomecin B while partial demethylation, under various conditions, gave 3‐hydroxy‐4,5‐di‐methoxy‐, 3,4‐dihydroxy‐5‐methoxy‐, and 3,5‐dihydroxy‐4‐methoxyphthalaldehyde. Other attempts to synthesise fomecin B and flavipin are recorded briefly.
Conformational Equilibria in Trans 1,2‐Diarylethylenes Manifested In Their Emission Spectra. Part III. (1a). Pyridyl and quinolyl derivatives
Authors: Fischer Ernst
Published: September 2010

The emission spectra of four 1,2‐diarylethylenes, in which at least one aryl is 3‐pyridyl or 7 or 8‐quinolyl, vary with the wavelength of excitation, indicating the existence of two or three species of each compound with slightly‐shifted emission (and absorption) peaks, in analogy to our earlier reports (1). At temperatures below ‐70°C in solutions in aliphatic hydrocarbons the normal fluorescence is gradually replaced by a broad and almost structureless emission band in the range 400‐550 nm. The conversion takes time, it is virtually complete at ‐120°C. No similar phenomena were observed in toluene/methylcyclohexane mixtures. The results at temperatures above ‐70°C are ascribed to the existence of an equilibrium mixture of rotamers, while those below ‐70°C are suggested to reflect association phenomena.
Préparation de la D (‐) Phénylglycine: Mise au Point D'Un Dedoublement par Entraînement
Authors: Schouteeten A. , Christidis Y. , Mattioda G. , Brienne M. J. , Jacques J.
Published: September 2010

The reaction of glyoxilic acid with ethyl carbamate followed by an acid‐catalyzed condensation with benzene leads to N‐carbethoxyphenylglycine in good yields. The resolution of this racemic (conglomerate) carbamate is performed by preferential crystallization of both enantiomers, the useless one being easily racemized and recycled. The full sequence represents a convenient and economical preparation of D(‐) phenylglycine.
Some 3,4‐diazanorcaradienes
Authors: Beynon Glynis , Figeys Hubert P. , Lloyd Douglas , Mackie Raymond K.
Published: September 2010

A number of 3,4‐diazanorcaradienes has been prepared from s‐tetrazines and cyclopropenes; their n. m. r. spectra (at various temperatures), mass spectra and, where apposite, ring‐inversion and/or decomposition, have been noted.
Steric effects in the dehydrohalogenation of 7‐halo‐bicyclo [3.2.0] hept‐2‐en‐6‐ols
Authors: Huston Rima , Rey Max , Dreiding Andre S.
Published: September 2010

Experiments are presented which show that base treatment of the 7‐halobicyclo‐[3.2.0] hept‐2‐en‐6‐ols 1 to 4 produces ring contraction to the aldehydes 5 and 6, except in those cases of the isomer series 4 where the substituent on the endo‐side of C(7) is larger than a chlorine atom, in which case endo‐hydrogen migration occurs to give the ketones 7.

Further experiments show that the methyl Grignard reagent does not attack the carbonyl group of 7‐endo‐t‐butyl‐7‐exo‐chlorobicyclo[3.2.0] hept‐2‐en‐6‐one (11) but, instead, leads to the dechlorinated ketone 23 and the two methylated ketones 27 and 28.
σ‐Conjugation and σ‐Aromaticity
Authors: Dewar Michael J. S.
Published: September 2010

Resonance integrals between different hybrid AOs do not vanish, contrary to statements in current texts. Bonds in saturated molecules are therefore not localized. Indeed β(sp3, sp3) is much greater than the CC resonance integral in conjugated hydrocarbons. Paraffins are therefore σ‐conjugated analogs of π‐conjugated polyenes. Additivity of collective properties applies equally to both, for reasons explained by PMO theory. This is why the localized bond model successfully interprets collective properties. Cyclopropanes should then be isoconjugate with benzene and hence σ‐aromatic. Various anomalies concerning the chemistry of small ring compounds can be explained in this way. Delocalization in alkyl anions and radicals, due to σ‐conjugation, is discussed.
Abnormal birch reduction of dichloro derivatives of C8H10 Hydrocarbons
Authors: Jefford Charles W. , de los Heros Viktor
Published: September 2010

Birch reduction of 2, 3‐dichlorotricyclo [3.2.1] octa‐3,6‐diene is mostly normal, giving bicyclo [3.2.1] octa‐2,6‐diene as the main product. However, products (15%) arising from intramolecular cyclization are also formed. Similar reduction of 4,4‐dichlorotetracyclo‐[3.3.0.02,803,6] octane is completely abnormal, giving mainly homoquadricyclane (71%) and rearranged products (29%). Possible mechanisms for these unusual courses are discussed.
Stabilité des Complexes des Acides Adénosine‐5′ Monophosphorique et Diphosphorique avec le Cation Nickel (II)
Authors: Mélardi M. R. , Galéa J. , Ferroni G. , Belaich Mme A. , Ragot M.
Published: September 2010

The stability of the complexes of anionic species of adenosine‐5′ monophosphoric acid (AMP) and adenosine‐5′ diphosphoric acid (ADP) with the cation nickel (II) have been studied, in water‐tetramethylammonium bromide 0, 2 M medium, by potentiometry (pH variable and pH stat) and by calorimetry.
Solvent extraction and spectrophotometric determination of vanadium(V) using N‐p‐tolyl‐2,4‐dimethoxybenzohydroxamic acid (p‐TDMBHA)
Authors: Agrawal Y. K. , Patel S. A.
Published: September 2010

A rapid method for solvent extraction and spectrophotometric determination of microgram quantities of vanadium with p‐TDMBHA is described. The bluish violet coloured complex extracted from chloroform, absorbs between 565‐575 nm. Beer's law is obeyed over the range of 0.10‐9.0 ppm of vanadium(V). The molar absorptivity of vanadium(V)‐p‐TDMBHA complex is 5.99 × 103 l mol−1 cm−1. Vanadium was determined in standard steel and phosphorite samples with good precision and accuracy.
Étude du Comportement D'Oximes de 7,8‐Dihydroquinoléine‐5 (6H) ‐ Ones Lors de la Réaction de Beckmann
Authors: Maquestiau A. , van Haverbeke Y. , Vanden J.‐J. Eynde , De Pauw N.
Published: September 2010

Various catalysts (H2SO4, PCl5, PPA) are used to perform the Beckmann reaction on oximes prepared from 7, 8‐dihydroquinolin‐5 (6H)‐ones.
Synthèse de 2‐Phenylpyrazolo [3,4‐B] Pyridine‐3 (1H)‐Ones
Authors: Maquestiau A. , van Haverbeke Y. , Vanden Eynde J.‐J.
Published: September 2010

The reaction between 1‐pheny1‐3‐aminopyrazolin‐5‐one and β‐dicarbonyl compounds is studied.

The orientation of the cyclocondensation is dependent on the nature of the 3‐dicarbonyl precursor and on the nature of the solvent.
Synthesis of Nad+ analogs. Part I. 3 ‐ benzoylpyridine nucleoside
Authors: Winné Ch. R. , Lepoivre J. A. , Alderweireldt F. C.
Published: September 2010

The title compound is synthesized from 2,3‐0‐isopropylidene ribofuranosylamine and 1‐(2, 4‐dinitrophenyl)‐3‐benzoylpyridiniura chloride in a Zincke type synthesis.
Solution Stability Constants of Beryllium, Cadmium and Uranium with N‐O‐Tolylbenzohydroxamic Acids
Authors: Agrawal Yadvendra K.
Published: September 2010

The metal‐ligand stability constants of Be2+, Cd2+ and Uo with N‐o‐tolylbenzohydroxamic acids were determined in 1:1 dioxan: water at 25° and 35°C
Structure de l'acide L‐Thiazolidinecarboxylique‐4 Hydantoine C5H6N2O2S
Authors: Arte E. , Tinant B. , Declercq J. P.
Published: September 2010

The structure of L‐thiazolidine‐4‐carboxylic acid hydantoin has been investigated using X‐ray diffractometer intensities. The conformation of the thiazolidine ring is that of an envelope β+ while the hydantoin is not exactly planar. Crystal data are as follow: monoclinic, P21; a = 10.898(3), b = 5.879(2), c = 5.064(2)Å, β = 100.5(2)°; V= 319.0 Å3; Z = 2; Dx = 1.65 Mg m−3.
Structure du complexe triindenyl‐uranium
Authors: Meunier‐Piret J. , Declercq J. P.
Published: September 2010

(C9H7)3U) triclinic, space group P1; a = 15.029(3), b = 8.757(2), c = 8.659(3)A,R α = 120.07(3), β = 83.72(3), γ = 100,33(3)°; Z = 2; DC = 1.998 Mg m−3 The structure was solved by the heavy‐atom method and refined by least‐square calculations. The final R value is 0.072 for 3057 diffractometer‐observed data. The U atom is π ‐ bonded in a approximately trigonal arrangement to three indenyl ligands.
Prediction of Anti and gauche vicinal proton‐proton coupling constants for hexapyranose rings using a generalized karplus equation
Authors: Haasnoot C. A. G. , De Leeuw F. A. A. M. , Altona C.
Published: September 2010

A new coupling constant ‐ torsion angle relation for the three‐bond 1H‐1H spin‐spin coupling constants is utilized to explore the effect of endocyclic and exocyclic oxygen atoms on Jae, Jee and Jaa in hexapyranoid systems. Attention is paid to common stereochemical surroundings rather than to individual compounds. It is shown that a simplified model for the flattened six‐membered ring, incorporating a constant geometry irrespective of the location of the coupled protons, correctly reproduces all the main trends observed.
O‐Tolyl‐Substituted Benzohydroxamic Acids as Colormetric Reagents For Vanadium(V)
Authors: Agrawal Y. K.
Published: September 2010

The reactions of 10 arylhydroxamic acids with vanadium(V) have been investigated in 6‐8 M hydrochloric acid medium to find the more sensitive and selective reagents among the family of hydroxamic acids. A rapid spectrophotometric method for the determination of vanadium(V) is described, employing N‐O‐tolyl‐p‐bromo‐benzohydroxamic acid. The interference of titanium, zirconium and molybdenum is eliminated.
Rotational Side‐Chain Isomerism And Aggregation Of The Diastereomeric Cyclic Dipeptides Phenylalanine, 4‐Thiapipecolic Acid
Authors: Anteunis Marc J. O. , Schrooten Rik , Nachtergaele Willy
Published: September 2010

The dimerization constants in CDCl3 at 25 °C have been measured for the cis‐ and trans‐diketopiperazines (DKP) c/Phe,(S)Pip/ from concentration‐dependent proton shifts [K2(cis) = 4.3 1/mol; K2‐(trans) = 1.27 1/mol]. The dimer is of a C8 ‐type H‐bridge structure. Concomitantly with aggregation an increasing folding of the aromatic nucleus over the DKP ring is observed at the dependency of the extended‐to‐N form. The greater stabilization for the folded structure in the cis‐isomer than in the trans‐isomer is reflected by the dimerization capacities. The tendency for stacking can be rationalized as the interplay of two phenomena; disrupture of intramolecular NH‐π interaction by solute‐solute or solute‐solvent interaction taken over by side‐chain/backbone (DKP‐ring) and side‐chain/side‐chain attractions. For the latter, a hydrophobic Van der Waals'‐type interaction and also a specific sulphur‐π interaction seems probable.
Preparation and enol allyl rearrangement of polychlorinated dimedone and 4,4‐dimethyl‐L,3‐cyclopentanedione derivatives
Authors: De Buyck L. , Verhea R. , De Kimpe N. , Schamp N.
Published: September 2010

The 2‐position in 5,5‐dimethyl‐l,3‐cyclohexanedione (dimedone) and in 4,4‐dimethyl‐1,3‐cyclopentanedione or their derivatives is completely and exclusively chlorinated with chlorine in dichloromethane. Diraethylformamide‐hydrogen chloride mixtures, especially when hot, effect enol allylic rearrangement of such a chlorine substituent to the 4‐ (or 6‐) position in excellent yield. Enolization is catalyzed both by DMF. HCl and the very weak base DMF. In two cases the intermediate rearranging enol was observed in high concentration by NMR. A stable enol was isolated. The efficient enolizing properties of DMF and its mixtures with HCl were exploited for the direct chlorination to hexachlorodimedone. Current investigations show the technique to be successful for the obtention of a wide variety of polychlorinated carbonyl compounds.
Polarographic Behaviour of 5‐Chlorosalicylaldehyde Oxime
Authors: Tiwari M. , Malshe P. T. , Kaushal R.
Published: September 2010

The polarographic behaviour of 5‐chlorosalicylaldehyde oxime has been studied in 8% ethanolic medium using tetramethyl ammonium bromide as supporting electrolyte. In acidic medium a single wave is observed which dissapears in alkaline medium. A mechanism for the electrode reaction is proposed.
The geometrical structure of the acetylene molecule in the X̃, G̃ and Ĩ states
Authors: Herman M. , Colin R.
Published: September 2010

The ro and rs geometrical parameters of the acetylene molecule in the linear X̃, G̃ and Ĩ electronic states are determined from the Bo rotational constants of several isotopes. The comparison of the internuclear distances shows a lengthening of the C ‐ C and C ‐ H bonds in the excited states compared to the ground state.
Mass Spectrometry Used to Discriminate Between Cis‐Syn‐Cis and Cis‐Anti‐Cis Photoadducts
Authors: Audenhove Martine Van , Keukeleire Denis De , Vandewalle Maurits
Published: September 2010

Cis‐syn‐cis and cis‐anti‐cis regioisomers of tricyclo [6.2.0.02, 7] decan‐3‐ones or tricyclo [5.2.0.02, 6nonan‐3‐ones, formed by (π2 +π2) photocycloaddition reactions between 1, 2‐bis (trimethylsiloxy) cyclobutene and 2‐cyclohexenones or 2‐cyclopentenones, respectively, are unequivocally identified by analysis of the isobutane chemical ionisation mass spectra.
Chemical Studies of Marine Invertebrates. XLIV(1). Three New Spongian Diterpenes From Spongia Officinalis(2)
Authors: Capelle N. , Braekman J. C. , Daloze D. , Tursch B.
Published: September 2010

Three new diterpenes, spongia‐13[16], 14‐dien‐19‐oic acid (1), spongia‐13[16], 14‐dien‐19‐al [5] and spongia‐13(16), 14‐dien [7], have been isolated from the sponge Spongia officinalis and their structures determined by spectroscopic methods and chemical intercorrelations.
Synthèse de nouvelles propenanidines n‐substituées a partir de sels de nitrilium[1]
Authors: Bril Marc Van Den , Fuks Robert
Published: September 2010

A number of N‐t‐butylpropenamidines V have beer, prepared for the first time by amination of N‐t‐butylacrylonitrilium [IIIb] or N‐t‐butylmethacrylonitrilium tetrachloroferrate (IIIc). The salts IIIb and IIIc are easely prepared at −40°C within a few minutes from the corresponding nitrile, t‐butyl chloride and ferric chloride. The amination [with primary or secondary aliphatic or aromatic amines] should be started at −70 °C to ensure a smooth reaction and to give high yields of amidine V, because the nitrilium salts are unstable above −10 °C. This method represents an easy one‐pot synthesis of N‐t‐butyl substituted propenamidines from the corresponding nitrile I.
2,2‐dichloroaldehydes from aldehydes and alcohols by chlorination in dimethylformamide
Authors: De Buyck L. , Verhé R. , De Kimpe N. , Courtheyn D. , Schamp N.
Published: September 2010

A method is described for the synthesis of α,α‐dichloroaldehydes, free from monochloroaldehyde, by chlorination of aldehydes or alcohols in dimethylformamide at 40–90°C. Results are reported for: (yield %) propanal (90), butanal (78), pentanal (78), 3‐methylbutanal (90), propanol (64), butanol (78), 3‐methylbutanol (52), pentanol (66), 3,3‐dimethylbutanol (86), hexanol (66), 2‐phenylethanol (51), 3‐phenylpropanol (54), 1,5‐pentanediol [3,3‐dichloro‐2‐hydroxytetrahydropyran (37), 2,3,3‐trichlorotetrahydropyran (19)], 1,6‐hexanediol [2,2,5,5‐tetrachloro‐1,6‐hexanedial (63)]. Oxidative conversion (KMnO4, K2Cr2O7, H2O2‐NaHCO3) into α,α‐dichlorocarboxylic acids and methyl esters is discussed.
Solidification Behaviour and Zone‐Melting Studies of Eutectic: Pyrogallol‐m.aminophenol system
Authors: Singh O. P. , Singh Narsingh Bahadur
Published: September 2010

Phase diagram, relative undercooling, linear velocity of crystallization and microstructure of eutectic have been investigated for the pyrogallol‐m;aminophenol system. The linear velocity of crystallization, V, for pure component and eutectic depends on ΔT according to the relation V = k(ΔT)n, where k and n are constant. Zone‐melting studies were made to determine the direction of solute transference, separation efficiency and equilibrium distribution coefficient.
Photochemistry of non conjugated bichromophoric systems. Photocyclomerization of 1,3 ‐ di(α‐naphthyl)propanol
Authors: Todesco R. , Gelan J. , Martens H. , Put J. , De Schrijver B. C.
Published: September 2010

The structure of the photocyclomers of the title compound has been elucidated by 1H nmr‐and I. R. ‐spectroscopy. Only endo cyclomers are observed, as in 1,3‐di(α‐naphthyl)propane. The absence of exo cyclomers is interpreted in terms of steric interactions.
Correlation between dipole increment and complexation enthalpy in charge transfer complexes between iodine and nitrogen bases
Authors: Huyskens P. , Mahillon PH.
Published: September 2010

The dipole moments μAB and the enthalpies of formation ΔHb of adducts of iodine with substituted pyridines and with triethylamine were measured at 298.2 K in cyclohexane. Taking into account the angle between the moment μB of the base and the I…I direction, the dipole increment Δμ was computed. The values of ‐ΔHb varied from 30 to 55 kJmole−1. In this range there exists a linear relation between Δμ and ‐ΔHb, which passes through the origin, the ratio between these two quantities being 0.094±0.002 Debye kJmole−1. This ratio Δμ/ΔHb is markedly smaller than that which can be computed from the results of Giera and Sobczyck for ‐0…I‐I complexes where it reaches 0.160. The difference can be ascribed to the presence of the second lone pair of electrons on the oxygen atom.
Influence exercée par l'hydroxyde de sodium sur la cristallisation des silicates de calcium dans des conditions hydrothermales
Authors: Vynck Ivan De
Published: September 2010

The influence of various NaOH concentrations on the hydrothermal transformation of calciumhydroxide silica mixtures is studied in the temperature range between 300 and 650°C.
Radioimmunoassay of angiotensin i in human plasma ‐ comparison of two renin activity methods
Authors: Lijnen P. J. , Amery A. K. , Fagard R. H. , Fyhrquist F.
Published: September 2010

Plasma renin activity (PRA) was measured by radioimmunoassay of angiotensin I generated during 1 hour incubation at the pH‐optimum. Angiotensin I was then assayed directly in the plasma or after extraction on a Dowex resin. A significant (p < 0.001) correlation between the PRA‐values obtained with both methods was observed. PRA determined in untreated (r = 0.79, p < 0.001) or extracted (r = 0.87, p < 0.001) plasma samples, was similarly related to simultaneously measured plasma angiotensin II levels. The predictive value of PRA, determined with both methods, in the hypotensive action of saralasin (an angiotensin II antagonist) and of captopril (an orally active angiotensin converting enzyme inhibitor) was of the same magnitude.
Benzo [b] tellurophènes substitues en position 3
Authors: Talbot J‐M. , Piette J‐L. , Renson M.
Published: September 2010

3‐substituted benzo (b) tellurophenes can be obtained through Wittig or Wittig‐Horner reaction on 2 H‐benzo (b) tellurophene‐3‐one (telluroindoxyl). This reaction shows a partial isomerisation specific of the tellurium series, due to breaking of Te‐CH2 bond. The products so obtained can lead to various mono 3‐substituted derivatives (CH3, CHO, CH2OH, COOH, COOCH3, CN, CONH2).

Reaction of triphenylphosphin/TeX4 on the same substrate leads to 3‐chloro and 3‐bromo benzo (b) tellurophenes, which could not be obtained by halogenation of the basic heterocycle. Acetylation of benzo (b) tellurophene with Ac2O/CF3COOH leads to a mixture 76/24 of 2‐acetyl and 3‐acetylbenzo (b) tellurophenes, which could be separated through thin‐layer chromatography.
Thermal Decomposition Studies: Part II kinetics of dehydration of transition metal complexes of salicylic acid
Authors: Heda B. D. , Khadikar P. V. , Gogne O. K.
Published: September 2010

Various kinetic parameters of the thermal dehydration reaction of metal complexes of salicylic acid with Fe (II), Zn (II), and VO (II) have been evaluated using Horowitz and Metzger and Fuoss methods. Observed kinetic parameters indicate the first order reaction. The activation energy of the thermal dehydration decreases in the order ‐ VO > Zn > Fe.
Zerovalent metal phosphite complexes. Synthesis of RE2 [P (OCH3)3]10
Authors: Choi Henry W. , Muetterties E. L.
Published: September 2010

Reaction of rhenium pentachloride and pyridine with potassium ‐ potassium iodide followed by a heating of the nonvolatile reduction residue with trimethyl phosphite gave Re2 [P(OCH3)3]10. A minor co‐product was HRe [P (OCH3)3]5 which presumably was generated from a radical intermediate like Re [P (OCH3)3]4 or 5 by a hydrogen atom abstraction from the organic reagents. Both Re2 [P(OCH3)3]10 and HRe [P(COH3)3]5 exhibited a nearly first order AB4 31P{1H} NMR spectrum. Neither complex showed the extreme photosensitivity (photodissociation of phosphite ligand) shown by W [P(OCH3)3]6 but the dimer was easily converted to the hydride by reaction with hydrogen.
Substitution at saturated carbon. Part 25. The iododemetallation of benzyltrialkyltins in methanol
Authors: Abraham Michael H. , Andonian‐Haftvan Jenik
Published: September 2010

The action of I2/I1 in methanol on compounds PhCH2SnR3 leads only to cleavage of the benzyl group (as PHCH2I) when R=Et, Prn or Bun. With PhCH2SnMe3, both benzyl and methyl groups are removed. Rate constants are reported for the iododemetallation of all four PhCH2SnR3 compounds, R=Me, Et, Prn and Bun. The present results and previous literature data show that with a constant SnR31 leaving group, the sequence of alkyl‐tin reactivity is Ph>PhCH2>Me>Et>Prn, with the benzyl‐tin bond being broken 3–4 times as rapidly as the methyl‐tin bond and about 40 times as rapidly as the ethyl‐tin bond. The effect of added anions, C𝓁, Br−, I− and C𝓁O4− on the rate constants (and products) are reported, and it is shown that both kinetic studies and product analyses lead to the conclusion that foreign anions do not participate in the reaction mechanism. These are, however, specific kinetic salt effects in the order NaBr<NaC𝓁<NaC𝓁O4<NaI.
NQR study of tetrametric ET3 YCU(I)X (Y = P, AS; X = CI, BR, I) COMPLEXES
Authors: Valigura D. , Verdonck L. , van Der Kelen G. P.
Published: September 2010

The geometry and electronic distribution of the tetrametric (Et3YCu(I)X)4 (Y = P, As; X = CI, Br, I) complexes can be rationalized within the “bonded” interaction scheme (electronegativity effect) as well as in the non‐bonded (steric effect). Both effects operate in the same direction explaining the socalled softness of the cubane frame.

The anomalous behaviour of the 63Cu NQR frequencies is caused by small specific bonded and nonbonded interactions affecting specially the electric field gradient and the field gradient asymmetry parameter.
Synthèse directe et propriétés biocides de benzyletains substitues
Authors: Mahieu B. , Hubesch B. , Maraite H.
Published: September 2010

Direct synthesis is the most economic way to produce organometallic compounds. In tin chemistry, it is well known that benzyl chloride gives very easily benzyltin derivatives. However, these latter show poor performances regarding to the phenyl or alkyltin compounds.

In this work, some ring‐substituted benzyl chlorides were used as reagent and the antifungal activity of the obtained tribenzyltins was measured.

It is found that substitution exerts an unfavourable effect on the biological properties of the products.
Electron, Transfer from Metal Surfaces. Formation of Lithium and Grignard Reagents1
Authors: Walborsky H. M. , Banks R. Bruce
Published: September 2010

Chiral (+)‐(S)‐4‐methylcyclohexylidenebromomethane (1) has been prepared from (−)‐(R)‐4‐methylcyclohexylideneacetic acid by a stereospecific bromode‐carboxylation reaction. The reaction was shown to proceed with an overall inversion of configuration.

The reaction of the chiral vinyl bromide with lithium and magnesium metal surfaces produced the corresponding chiral vinyllithium and Grignard reagents. The mechanism of formation of these reagents will be discussed.
Mass spectrometry of organometallic compounds I. the fragmentation upon electron impact of bis (η5 ‐cyclopentadienyl) vanadium (III) derivatives of the Cp2 v(sr) type and cp2 VCl
Authors: Claude Georges S. , Tabacchi R.
Published: September 2010

The fragmentation upon electron impact of bis (η5 ‐cyclopentadienyl) complexes of Vanadium(III): Cp2V(SR) (R=CH3, isoC3H7, phenyl, benzyl) have been investigated. The first fragmentation pattern is characterised by the formation of stable ions: Cp2V1+, Cp2VH1+ and CpSR1+. Further decomposition of the metal‐containing ions can be explained in terms of valence change concept.
Optically active transition metal complexes, LXXI *). synthesis, characterization, and conformational analysis of pyridine‐imine complexes [C5H5 (CO) 2MoNC5H4CX=NCH (R1) (R2)]PF2 with X = H, CH3, and C6H5
Authors: Brunner Henri , Rastogi Devendra K.
Published: September 2010

Six new complexes of the type [C5H5Mo(CO)2NN*]PF6 have been prepared by treatment of C5H5Mo (CO)3Cl with the Schiff bases NN*, derived from 2‐acetyl pyridine or 2‐benzoyl pyridine and chiral amines H2NCH(R1) (R2) with (R1) (R2) = (CH3)‐(C6H5); (C2H5) (C2H5), and (CH3) (C2H5). The Schiff bases NN* contain a chiral amine component in its racemic form (R')/(S'). Therefore, in combination with the Mo chirality (R) and (S) a mixture of diastereoisomeric pairs of enantiomers (RS′)/(SR') and (SS')/(RR') is obtained. The diastereoisomers are separated by fractional crystallization. Diastereoisomer equilibration was achieved by heating the compounds in acetone‐d6 at 80°C for 90 h. The diastereoisomers have been differentiated on the basis of their 1H NMR spectra. A conformational analysis in terms of a) chemical shift difference for the C5H5 signals and b) ratio of diastereoisomers at equilibrium indicates how the chiral carbon substituents arrange with respect to the ligand plane for the diastereoisomers differing at the Mo configuration.
Effect of sodium on the co/γ‐al2o3 system. influence of the preparation conditions and calcination temperature
Authors: Lycourghiotis A. , Defossé C. , Delmon B.
Published: September 2010

The conditions at which sodium used as a dope can modify the state of dispersion and nature of γ‐alumina supported cobalt oxide are investigated. The order of impregnation and the temperature of calcination after Na impregnation are shown to be essential factors.
Het verband tussen parameters voor verdunde en matig geconcentreerde oplossingen van macromoleculen. Toepassing op sedimentatiecoefficienten
Authors: Peeters F. A. H. , Smits H. J. E.
Published: September 2010

Accurate determinations of the coefficient of sedimentation for fractions of polystyrene in toluene, above as well as below the critical concentration c* for molecular overlap, resulted in the following expressions for respectively the parameter for the concentration effect in dilute solutions, and the coefficient of sedimentation in moderately concentrated ones: ks=(5.9±0.3)XSo1–71±0.02 and S=(0.163±0.007)XC−(0.606±0.006) With these, we could check some relations of correspondency, suggested by Wales, with respect to S(c) at either side of c*. Because of the satisfactory result ‐ reliably calculated S(c) from the experimentally determined ks(So) ‐ Wales theory was modified and applied to the radius of gyration, the osmotic pressure and the viscosity.
Yttrium(III), lanthanium(III) and zirconium(IV) complexes of some bidentate schiff bases derived from hetero aromatic amines and salicylaldehyde
Authors: Abd El‐Hamide R. , Mahmoud M. R. , El‐Haty M. T.
Published: September 2010

Y(III), La(III), and Zr(IV) complexes with some heteroaromatic Schiff bases derived from salicylaldehyde and heteroaromatic amines, viz 2‐amino‐pyridine, 2‐amino‐4‐phenylthiazole and 2‐amino‐5‐phenyl‐1, 3, 4‐thiadiazole have been prepared, The structures of the complexes have been investigated by elemental analysis, the spectrophotometry molar ratio and continuous variation methods as well as infrared spectra. It is found that the complexes obtained are characterized by high coordination number.
Amino steroids ‐ functionalization of position 20 from position 18 in a pregnane system through a Hofmann‐Löffler process. predominant formation of 5α‐heteroconan‐3β‐ol
Authors: van De Woude G. , Biesemans M. , van Hove L.
Published: September 2010

The Hofmann‐Löffler sequence of reactions applied to 18‐methylamino‐5α‐pregnan‐3β‐ol led to Sα‐heteroconan‐3β‐ol (11, 20BF or 20R configuration) and to 5α‐conan‐3β‐ol (12, 20αF or 20S configuration, as in natural conanine derivatives) in a ratio of 8 to 1, to the exclusion of any other nitrogen containing cyclic system.
New results about the c26 sterols also concerning their possible origin
Authors: Boutry J. L. , Barbier M.
Published: September 2010

Stanols and particularly the C26 stanol 5, have been found to accumulate in an oil impregnated sediment. In connection with the possible origin of C26 sterols as deduced from this observation, model experiments using a C28 precursor (campestanol) have been performed. However, in the conditions of these experiments, the bacterial degradation of the side chain by a pool of marine bacteria does not lead to the expected steroid structures.
Dogger bank itch. 2. An allergic contact dermatitis
Authors: Carlé Jørgen S. , Christophersen Carsten
Published: September 2010

Dogger Bank Itch is an allergic contact dermatitis representing a severe occupational hazard among trawlermen of the Dogger Bank Area in the North Sea. Allergic sensitivity is acquired following exposure to the marine bryozoan Alcyonidium gelatinosum. The allergen has been identified as (2‐hydroxyethyl) dimethylsulfoxonium ion. The isolation, structure determination and synthesis of the allergen is discussed.
Electrochemical Studies on the Metal Complexes of Alizarin Fluorine Blue and Its 5‐Sulphonated Analogue
Authors: Qureshi G. Ali , Ireland N.
Published: September 2010

Polarographic, cyclic voltammetric and microcoulometric techniques have been used to study the electrochemical nature of the binary and ternary comlexes of Alizarin fluorine blue and its 5‐sulphonated analogue. The conditional constants of certain metal complexes are evaluated and effort has been made to determine the exact compositions of these complexes. The pH‐effect on the E1/2 and id are discussed.
Phenyl Group Interchange in Gaseous Protonated α‐Phenylacetophenones
Authors: Maquestiau A. , Coupez C. , Flammang R.
Published: September 2010

Fluorine and carbon 13 labeling experiments show that the phenyl group interchange in metastable protonated α‐phenylacetophenones (methane chemical ionisation conditions) occurs through protonated oxirane and diphenylacetaldehyde intermediates.
Role of the 1/e1+α Epithermal Neutron Flux Distribution in the K0‐Method α‐Mapping of Reactor Thetis
Authors: De Corte F. , Moens L. , Simonits A.
Published: September 2010

A survey is given of a recent study concerning the deviation of the 1/E1+α epithermal neutron flux distribution from the ideal 1/E‐shape.

So as to preserve the accuracy of the k0‐comparator method for standardization in (n,Y) activation analysis, it was of vital importance to work out appropriate α‐correction procedures on the resonance integrals to be used. Attention is paid to the development and the optimization of new methods for experimental α‐determination, which can be generally applied by activation analysis laboratories.

The study enabled a complete α‐mapping for the 17 irradiation positions of reactor Thetis (Gent). It is found that, to a good approximation, the epithermal flux distribution in channel 9 is following the ideal 1/E‐law, i.e. α=0.
Energy‐Dispersive XRF Analysis of Soils Using a 109cd Excitation Source and a Precision Optimization Method
Authors: Voutchkov M. , Op De Beeck J.
Published: September 2010

An energy‐dispersive XRF analysis method, using a 109Cd excitation source has been developed for routine analysis of minor constituents or trace elements of high atomic number, in a matrix of low atomic number elements, such that enhancement matrix effects are negligible. A simple linear relationship between analytical concentration and a pure experimental factor is obtained, using the double absorption‐thickness method, taking into account correctly all absorption matrix effects. The theoretical optimization of the final precision on the analytical results, as well as the practical application are discussed. As an example the method has been applied to analyse a series of soil samples, giving results in good agreement with other methods of analysis.
Preferential Solvation of Single Ions: The PH4ASPH4B Assumption for Single Ion Thermodynamics in Mixed Dimethylsulfoxide‐Water Solvents
Authors: Kim J. I. , Gomaa E. A.
Published: September 2010

The paper presents a study of the Ph4AsPh4B assumption as for verification of its plausibility for the determination of thermodynamic quantities of single ions in mixed dimethylsulfoxide (DMSO)‐water solvents. For discussion the solvation energy is considered as a composite of electrostatic and neutral components. The neutral components are replaced by experimental data of Ph4Ge and Ph4C which are proved to be equal, of their size and structure, to the reference cation and anion. The electrostatic components are obtained by calculation according to the theory in the literature. The results of the present investigation provide the conclusion that an assymmetric partition is preferred to an equal partition practiced in the literature. Based on the study, the standard free energies of transfer for single ions, Ph4As+, Ph4B, Cs+ and I−, are determined and for others, H+, Li+, Na+, K+, Rb+, Cl− and Br− evaluated from the data of salts known in the literature. Discussion is elaborated with solvation properties of individual ions.
Stability of Calcium‐Strontium Hydroxyapatite Solid Solutions in Aqueous Solutions at 25°
Authors: Verbeeck R. M. H. , Driessens F. C. M. , Thun H. P. , Verbeek F.
Published: September 2010

Phase diagrams were constructed from phase equilibrium calculations for the quaternary system Ca(OH)2‐Sr (OH)2‐H3PO4‐H2O and for the system Ca(OH)2‐Sr(OH)2‐H3PO4‐HX(BOH)‐H20 at 25°. On the basis of these diagrams the stability field of solid solutions of calcium and strontium hydroxyapatite was derived. The calculations show the borderlines of the apatite field to be determined by the activity isotherms of the sparingly soluble phosphates CaHPO4.2H2O, Ca8H2(PO4)6.5H2O, β‐SrHPO4 or Sr6H3(PO4)5.2H2O depending on the pH and the molar cSr:cCa and cCa: cP ratios in the solution. The biological implications of these results are discussed.
La Chimie des Arômes: Les Hétérocycles
Authors: Vernin Gaston , Metzger Jacques
Published: September 2010

Heterocyclic compounds are widely distributed in food flavours. They arise following two main ways:

enzymatic and fermentation reactions from primary precursors (proteins, lipids, anthocyanines, polyphenols, carotenoids, ribonucleotides…).

non‐enzymatic browning reactions between reducing sugars and α‐amino acids also called MAILLARD's reaction.

The thermal degradation of food components: sugars, amino acids, vitamins, trigonelline… constitutes another important source of heterocyclic compounds.

The various steps of the MAILLARD reaction as well as the formation of furans, pyrroles, thiophenes, oxazoles, thiazoles, imidazoles, pyridines, pyrazines, lactones in these reactions are described.

Owing to the great complexity of natural flavouring mixtures and model systems, the computer assisted synthesis and the realization of a bank of mass spectra provide a valuable help to identify heterocyclic compounds in food flavours.
Electroanalysis of Some of The Organic Substances and the Effect of Halide Ions on Their Determinations in Effluents
Authors: Ali Qureshi G.
Published: September 2010

The electroanalytical technique based on the coverage of bright platinum electrode with methanol, ethanol, butan‐1‐ol, iso‐propanol and phenol as a function of potential and bulk concentration of these compounds in 1M H2SO4 is shown. The interference due to halide ion in the determination of organic substance is reported.
The Synthesis of 1‐Phenyl‐|4,5|‐Decanes
Authors: van Parys Marc , Vandewalle Maurits
Published: September 2010

The synthesis of some substituted 1,8‐diazaspiro|4,5|decanes starting from l‐benzyl‐4‐oxo‐piperidine is described. This skeleton is isosteric to the 1,3,8‐triazaspiro|4,5|‐decane structure present in important neuroleptic agents.
Solvolysis of Cis‐ and Trans‐S‐Methyl‐Thiazolidinium Phenylalanine Cyclic Dipeptides
Authors: Anteunis Marc J. O. , Becu Chr. , Kolodziejczyk A. , Liberek Bogdan
Published: September 2010

The solvolysis of cis− and trans‐S‐methylthiazolidinium phenylalanine cyclic dipeptides (diketopiperazines) in H2O (D2O), CH3OH, CD3OD:D2O and DCOOD has been studied. Ring opening of the Thz rings occurs (i) exclusively at the δ‐position in the trans‐isomers, resulting in the corresponding cysteinyl‐phenylalanine diketopiperazine derivatives in good yields; (ii) only partly at the δ‐position in the cis‐isomers, resulting in more complex reaction mixtures. The regiospecificity of ring opening is lost when weaker nucleophiles but stronger bases are used and substantial amounts of eliminative ring‐opening by H‐α attack is noticed. Kinetic studies in the different solvent systems reveal that solvolysis bears SN2 character.
Pyridines. Partie IX‐Pluribenzylation de La S‐Collidine et de La Lutidine‐2,6
Authors: Compagnon Paul‐Louis
Published: September 2010

A literature survey of the polymetalation of 2,6‐lutidine 2 shows different results about the site(s) of deprotonation and condensation with various electrophiles. This discrepancy prompts us to examine the polylithiation (PhLi 3 equivalents, Et2O) of s‐collidine 1, 2,6‐lutidine 2 and more briefly of 2,4‐lutidine 3. Polylithiation takes place exclusively at the methyl groups of the same position vs the ring nitrogen: 2‐and/or 6‐methyl of 1. The previous regioselectivity observed in the case of the monometalation in Et2O is maintained. From 1 and 2, polylithiation gives picolyl anions which lead by reaction with PhCH2Cl, simultaneously to mono‐, di‐symmetrical, di‐non‐symmetrical α‐derivatives, and tri‐and tetra‐symmetrical α,α'‐compounds; but no product is formed from a benzylic β‐anion. In the same way, the deprotonation of 2‐methyl‐6‐(2‐phenylethyl) pyridine 17 leads to 2,6‐bis (2‐phenylethyl) pyridine 19 and 2‐methyl‐6‐dibenzylmethyl pyridine 18, to the exclusion of the β‐compound 2‐methyl‐6‐(2,3‐diphenylpropyl) pyridine 21. The latter compound is formed in low yield, besides 19 and 18, in the conditions of the Tchitchibabine reaction (NaNH2, toluene). The structure of the benzylated compounds was established mainly from the 1H‐nmr data. No product was isolated which would result from the nucleophilic attack of the generated carbanions at the pyridine carbons.
Synthesis of 5‐Alkyl‐3,3‐Dimethyl‐1,2,4‐Cyclopentanetriones, Involving Hydrogenation of 2‐Acyldimedones and Polychlorination
Authors: De Buyck L. , De Pooter H. , Verhé R. , De Kimpe N. , Schamp N.
Published: September 2010

2‐Alkyldimedones, obtained from 2‐acyldimedones, were converted into 5‐alkyl‐3,3‐dimethyl‐1,2,4‐cyclopentanetriones in 40‐70 & overall yields, calculated on dimedone (AlkylMe, Et, n‐Pr, n‐Bu and 1‐Bu). The synthesis involved ring contraction of 2‐alkyl‐4,4,6,6‐tetrachloro‐5,5‐dimethyl‐1,3‐cyclohexanediones to afford 2‐alkyl‐3,5,5‐trichloro‐4,4‐dimethyl‐2‐cyclopentenones, which were hydrolyzed to give the title products.
Contribution a L'Étude Électrochimique de Dérivés de L'Acide Mercapto‐2 Pyridine Carboxylique‐5
Authors: Lejeune R. , Vandenbalck J. L. , Patriarche G. J. , Lapière C. L.
Published: September 2010

2‐methylthiopyridine‐5‐carboxylic methylic ester and 2‐methylthiopyridine‐5‐carboxylic acid have been studied by recent polarographic and voltammetric technics (3,4). These molecules are irreversibely reduced at the thioether site. When considering the direct current, alternative and the differential pulse polarograms compared to cyclic voltammograms, the behaviour of these compounds can be elucidated. The pH influence on each basic fonction proton exchange and the adsorption impact on this protonation are described. A complementary study as a fonction of concentration establish the optimal conditions to quantify these compounds by classical and differential pulse polarography.
Studies of Brazilian Marine Invertebrates. VIII. Zoanthosterol, a New Sterol from the Zoanthid Zoanthus Sociatus (Hexacorallia, Zoanthidea)
Authors: Kelecom A.
Published: September 2010

The new marine sterol zoanthosterol, 4α‐methyl‐5α‐ergosta‐24 (28)‐en‐3β‐ol, has been isolated, together with cholesterol and chalinasterol, from the zoanthid Zoanthus sociatus. The structure of zoanthosterol was deduced from spectroscopic data.
Regioselective Cleavage of the “E” Ring in Diosgenin
Authors: Singh Anil K. , Dhar Durga N.
Published: September 2010

Diosgenin, under a variety of acidic conditions, has been found to undergo an anomalous regioselective cleavage of the “E” ring affording a 16‐keto derivative.
Desoxybenzoins from the Lithium Bromide‐Catalyzed Homologation of Aromatic Aldehydes with Phenyldiazomethane
Authors: Loeschorn Carol A. , Nakajima Masayuki , Anselme Jean‐Pierre
Published: September 2010

Desoxybenzoins are obtained in good to excellent yields from the lithium bromide‐catalyzed homologation of aromatic aldehydes with phenyldiazomethane.