bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation of D‐[1‐14C,1‐2H]Glucose and D‐[U‐14C,1‐2H]Glucose
Authors: Malaisse‐Lagae F. , Zähner D. , Sener A. , Malaisse W. J. 
Published: September 2010

AbstractAn enzymic method is presented for the preparation of 14C‐labelled and C1‐deuterated D‐glucose, to be used as a radioactive tracer in metabolic studies dealing with the fate of D‐[1‐2H]glucose. The procedure takes advantage of the deuteration of 14C‐labelled D‐fructose 6‐phosphate during exposure to phosphomannoisomerase in D2O. It further includes the conversion of the deuterated hexose monophosphates to D‐fructose 1,6‐bisphosphate, its isolation and hydrolysis to D‐fructose 6‐phosphate and the partial conversion of the latter ester to D‐glucose 6‐phosphate, which is then isolated by ion exchange chromatography and hydrolyzed to unesterified D‐glucose. The extent of deuteration on the C1 of D‐glucose was judged, after conversion to D‐glucose 6‐phosphate, from the isotopic discrimination in reaction velocity exerted towards the C1‐deuterated ester by glucose‐6‐phosphate dehydrogenase. The degree of isotopic discrimination was virtually identical to that found with D‐glucose 6‐phosphate prepared from pure D‐[1‐2H]glucose.
Phase Transitions in Oxides Studied by Thermal Expansion Measurements
Authors: Brabers V. A. M. 
Published: September 2010

AbstractIn this paper, thermal expansion measurements on AgNbO3, YBa2Cu3O7‐δ, Bi2Sr2Ca2Cu3O10+δ, MnxFe3‐xO4, MgFe2O4 and Co3O4 are reported, from which the advantages of thermal mechanical analysis (TMA) in the study of phase transitions is demonstrated. Especially, the quantitative analysis of the cation disordering in MgFe2O4 and the LS‐HS spin transition in Co3O4 shows the possibilities of TMA. For the disordering reactions in MgFe2O4, activation energies of 125 and 145 kJ/mol are found, for the LS‐HS transition in Co3O4 a reaction energy of 30 kJ/mol.
Nucleophilic Displacement Reactions on Sterically Hindered Chloro‐Pyridines: Some Optimisation Studies
Authors: Pascual A. 
Published: September 2010

AbstractA Factorial Design has been used to optimise the reaction conditions for the nucleophilic displacement of chlorine in 2‐chloro‐4,6‐diisopropyl‐5‐nitropyridine (1B) by 4‐chlorophenol. The results obtained have been successfully applied to a large variety of phenols and thiophenol.
Syntheses of New 4‐Trifluoromethylated 1,3‐Oxazin‐6‐Ones from the Enamine of Ethyl Trifluoroacetoacetate
Authors: Decock‐Plancquaert Marie‐Aimée , Evariste François , Guillot Nadine , Janousek Zdenek , Maliverney Christian , Merényi Robert , Viehe Heinz G. 
Published: September 2010

AbstractNew 4‐trifluoromethyl‐1,3‐oxazin‐6‐ones have been prepared in excellent yields from ethyl 3‐amino‐4,4,4‐trifluorocrotonate (ATFC) by two original procedures: reaction of ATFC with phosgeniminium chlorides to give 2‐dialkylamino‐4‐trifluoromethyl‐1,3‐oxazin‐6‐ones, or action of chlorinating agents on N‐acyl ATFC. The reactivity of ATFC in these reactions is compared with non‐fluorinated analogs.
ω‐Substituted α,α‐Dichloroaldehydes and Derivatives Via Formolysis or Acetolysis of 2,3,3‐Trichlorotetrahydrofuran and 2,3,3‐Trichlorotetrahydropyran
Authors: De Buyck Laurent , Vanhulle Peter 
Published: September 2010

AbstractPreferable routes to the 2‐hydroxyderivatives 7 resp. 8 of 2,3,3‐trichloro THP (1) or 2,3,3‐trichloro THP (2) involve the uncatalyzed methanolysis of the corresponding 2‐formates or 2‐acetates. These activated esters were rapidly formed from 1 or 2 in a hot slurry of sodium carboxylate and carboxylic acid. They suffered partial isomerization to ω‐acyloxy‐α,α‐dichloroaldehydes in the presence of strong acid. A useful ring opening to ω,1,1‐triacetates 13 resp. 14 occurred with H2SO4in a mixture of acetic acid and acetic anhydride (2–4 d at 135 °C). To prepare the pure aldehydes 10 and 12 acetic anhydride was split off from the triacetates (NaOAc, 150‐190°C in vacuo). The ester function of 10 and 12 is sensitive to uncatalyzed methanolysis, apparently because of intramolecular assistance in the hemiacetal forms. The behavior of 7 and 8 as hidden α, α‐dichloro‐ω‐hydroxyaldehydes is further demonstrated by their reduction (NaBH4, EtOH) to the 2,2‐dichloro‐1,ω‐diols 19 resp. 24.
Lanthanide Complexes of Di(4‐Hydroxycoumarinyl‐3)‐Acetic Acid and Their Anticoagulant Action
Authors: Deng Ru Wen , Wu Ji Gui , Long La Sheng 
Published: September 2010

AbstractThe lanthanide complexes of di(4‐hydroxycoumarinyl‐3)—acetic acid (M2L3 · 10H2O) have been synthesized and characterized by IR, HNMR, electronic spectra, thermoanalysis and molar conductance. The metallic ions substituted two hydrogen atoms of carboxyl and hydroxy groups and are also bonded to the oxygen atom of the carbonyl group of the benzopyranyl ring. Electronic spectra showed that the lanthanide—ligand bond had some covalent character and the involvement of 4f orbital was very small. The light lanthanide complexes revealed the nice anticoagulant action especially the lanthanum coordination compound.
Solvent Parameters and the Thermodynamics of Mobile Disorder in Liquids
Authors: Huyskens Pierre L. , Vael‐Pauwels Christine , Seghers Katarine 
Published: September 2010

AbstractAccording to the basis ideas of Gutmann, specific cohesion forces are in many cases more important for solvent effects than non‐specific interactions. In this work the fundamental differences between H‐bonds or n‐σ EDA bonds and non‐specific dipole‐dipole interactions are outlined: stechiometry, directionality, and especially the essential difference between the two active sites. As a consequence the capacity of a solvent to form specific bonds with the solute cannot be described by a single parameter. As pointed out by Gutmann, two different capacities of the solvent have to be considered. The solvents can be classed according to the presence in their molecule of active sites of one or another kind. The theoretical ground for the use of solvent parameters is studied in the frame of the thermodynamics of the Mobile Disorder in liquids developed by Huyskens and Siegel. A new solvent parameter based on the ratio of the molar volumes of solute and solvent PVB/VS is introduced which is equal to (0.5 — rS)(vB/vS) + 0.5 ln(VB/VS) ‐ 0.5. rS takes the value of one for amphiphilic solvents with one proton donor site, of two for the solvents with two hydroxylic protons and of zero for the others. For amphiphilic solutes (with one OH group) rS has to be added to the former expression. This purely entropic parameter is independent of all the others. A positive value of PVB/VS corresponds to a decrease of μB/RT and a stabilization of the solute in the solution. At high dilution the solute‐solvent specific forces decrease μB/RT by an amount ln(1 + K/VS) where K is the stability constant of the bond. The latter depends on both the solvent and the solute. The values ln(1 + Kref/VS) of various solvents can be compared for some reference solute. This constitutes the thermodynamical basis for the use of solvent parameters. The acceptor and the donor parameters AN and DN of Gutmann are discussed from this point of view.
An Explorative Investigation into the Reaction of Ammonia with Ketones. Mediated by Low‐Valent Titanium
Authors: Volckaerts E. , Geise H. J. , Daelemans F. 
Published: September 2010

AbstractMediated by low‐valent titanium, generated from TiCl3/LiAl4. ammonia is incorporated into benzophenone to give N‐(diphenylmethylene)‐N‐(diphenylmethyl) amine in a synthetically useful reaction. A good yield (65 %) requires that the temperatures of the reaction stages are well controled and that ammonia and ketone are simultaneously introduced keeping their molar ration 1:1. The possible sequence of reactions is discussed.
‘Stilbene to Phenanthrene’ Type Photocyclization of a Bis‐(4‐Anthryl) Ethylene. A New Access to the Dibenzopicene Skeleton
Authors: Segura C. , Parella T. , Sanchez‐Ferrando F. , Bouas‐Laurent H. , Desvergne J.‐P. 
Published: September 2010

Abstract1,8‐Didecyloxyanthracene is a starting material for a new synthesis through a photochemical step of a derivative of dibenzo [b,l] picene, soluble in organic solvents.
Heterocyclic π‐Donors, Macrocycles and Cage Molecules
Authors: Becher Jan , Hansen Thomas K. , Jørgensen Tine , Stein Paul 
Published: September 2010

AbstractReaction of dmit‐salts 2 and bis‐alkylating agents leads to macrocycles annelated to a 1,3‐dithiole‐2‐thione ring. Intermolecular coupling of monomers MC[n,1] leads to TTF‐crowns of type A whereas intramolecular coupling of dimers MC[n,2] gives TTF‐cages of type B. The complex formation of type A and B host molecules with alkali metal ions is discussed.
New Fused as‐Triazines with Bridgehead Nitrogen Synthesis and Reactivity
Authors: Hajós György , Messmer András , Bátori Sándor , Riedl Zsuzsanna 
Published: September 2010

AbstractTwo synthetic pathways have been elaborated for the synthesis of pyrido[1,2‐b]‐as‐triazinium salts and were also extended to the linearly fused as‐triazino[2,3‐b]isoquinolinium and the angularly fused as‐triazino[3,2‐a]isoquinolinium systems. The ring closures were found to proceed in regioselective manner which was rationalized by assumption of the different charge distribution in acidic and basic conditions.Preparative route has also been worked out for the synthesis of pyrido[2,1‐f]‐as‐triazinium salts and its differently (linearly and angularly) fused benzologues. The new heteroaromatic ring systems easily formed covalent hydrate salts under acidic conditions and pseudo bases with nucleophiles under basic conditions.
Synthesis and Reactions of Oxazolones from L‐Tryptophan and α‐Haloacetic Anhydrides
Authors: Bergman Jan , Lidgren Göran , Gogoll Adolf 
Published: September 2010

AbstractOptically active 5(4H)‐oxazolones have been synthesized from L‐tryptophan and an excess of trifluoro‐, trichloro‐, and dichloroacetic anhydrides. Some of the 5(4H)‐oxazolones have been further transformed to the isomeric 5(2H)‐oxazolones as well as oxazolones with exocyclic double bonds. Treatment of the various oxazolones under hydrolytic, acidic and Friedel‐Crafts acylation conditions gave indole‐3‐pyruvic acid, α,β‐dehydrotryptophans, β‐carbolines as well as the functionalized cyclopentanoindole 32. Treatment of the 4‐(3‐indolylmethyl)‐2‐trifluoromethyl‐5(2H)‐oxazolone (17) with trifluoroacetic acid gave the 3,4‐bridged azepinoindole 35.
Rotating Ring‐Disk Study of the Influence of PH on The Cu(II)/Cu(I)/Cu(0) Electrode Reactions at Gold in Aqueous 0.5 M Sulphate Solution
Authors: Vandenbruwaene J. , Temmerman E. 
Published: September 2010

AbstractDepending on pH and copper(II) concentration up to three reduction and four oxidation waves may be observed by cyclic voltammetry at a rotating polycrystalline gold ring‐disk electrode in sulphate solution. These are related to the reduction of copper(II) (oxidation of deposited copper metal), to underpotential deposition (dissolution), the deposition (dissolution) of a copper layer adjacent to the underpotential layer and of bulk copper. Analysis of the dependence of the ring currents on electrode rotation rate and copper(II) concentration shows the importance of the dismutation of copper(I). The observed pH effects can be explained by the presence of different hydrated copper(II) species, hydrolysis of copper(I) and the formation of Cu2O on the disk electrode surface.
Synthesis of Dipeptide Esters of Metronidazole and Evaluation of Their Hydrolytic Stability
Authors: Permentier Dirk , Vansteenkiste Stefan , Schacht Etienne , Vermeersch Hans , Remon Jean Paul 
Published: September 2010

AbstractAmino acid and dipeptide esters of metronidazole were synthesized and evaluated on their hydrolytic stability in various buffers and culture media. The hydrolytic susceptibility of the different esters was minimal in the pH range 3 ‐ 5. In the alkaline region, pH 6.5 ‐ 8, the half‐lifes were of the order of 1 ‐ 6.6 hrs. At alkaline pH the dipeptide esters were more susceptible towards hydrolysis. At pH 8.8 the observed half‐life for the gly‐gly and the gly‐phe esters was 0.2 h, whereas for the gly and the phe ester it was 1.1 h, respectively 2.7 h. It was demonstrated that the increased rate of hydrolysis for the dipeptide esters was due to an intramolecular aminolysis with the formation of a diketopiperazine accompanied by the release of free metronidazole.
Kinetic Study of the Electrophilic Reaction Between iPRI and ICI
Authors: Verbiest P. , Verdonck L. , Van Kelen G. P. Der 
Published: September 2010

AbstractThe kinetics of the electrophilic reaction between iPrI and ICI are presented. A rate equation first order in iPrI and second order in ICI is found. A mechanism is proposed involving Charge‐Transfer as the driving force for reaction.
Photooxidations of Organic Substrates in Presence of Copper Complexes: The Validity of The Geminate‐Pair Scavenging Mechanism
Authors: Sýkora J. , Molčan M. 
Published: September 2010

AbstractThe validity of the Noyes geminate‐pair scavenging mechanism for the photoredox reactivity of chlorocopper (II) complexes in acetonitrile in presence of methanol, isopropanol, acetone and benzene as scavengers for chloride radicals has been tested. Experimentally obtained linear dependence of Cu(l) quantum yield formation on the square root of scavenger concentration within the range where scavenging reaction competes with the secondary recombination justifies that the Noyes mechanism is operative. The estimated values for scavenging rate constants are in good agreement with those previously reported using another experimental method. It has been found that the photoredox reactivity of the lowest spin‐allowed doublet LMCT excited state of the tetrachlorocuprate (II) complex at 460 nm is higher than that of LMCT lying at 313 nm.
Extraction Spectrophotometric Determination of Vanadium in Steels with Thiosalicylic Acid (TSA)
Authors: Salinas F. , Martínez‐Vidal J. L. , Martínez‐Galera M. 
Published: September 2010

AbstractIn this paper thiosalicylic acid (TSA) is proposed for a simple, rapid and selective method for the spectrophotometric determination of vanadium based upon the formation of the TSA‐vanadium complex and its extraction into Adogen 464‐toluene solution.Under optimum operating conditions, a green colour is formed when the complex is extracted, from weak acidic 40% ethanolic solution, In the organic solvent (apparent molar absorptivity 1,700 L.mol−1·cm−1 at wavelength of 600 nm). The relative error is 2.3%, in the determination of 16 μg.mL−1 of vanadium, and its limit of detection is 3 μg·mL−1. The method has been applied to the determination of vanadium in steels.
Etude De La Conformation D'oximes Thiopheniques
Authors: Oussaid Boualem , Fayet Jean‐Pierre , Pelletier Gilles , Garrigues Bernard 
Published: September 2010

AbstractThe condensation of 2,5‐diformylthiophene with hydroxylamine hydrochloride leads to the formation of three isomers. Two isomers 1′ and 1” present a second order axis of symmetry; compound 1′ is present with the configuration ZZ and exists in the conformation a and compound 1” is present with the configuration EE and exists in the conformation b. The last isomer 1”′ presents the e (Z,E) conformation.
Bioelectrocatalytical Method for Glucose Determination in Foodstuffs
Authors: Stoytcheva Margarita 
Published: September 2010

AbstractA bioelectrocatalytical method for the glucose contents in foodstuffs is proposed. Conserving the advantages of the photometrical enzymic methods, it is rapid, simple and economizing, too. It is also much better than certain bioelectrocatalytical methods with which the glucose is determined indirectly ‐ by O2 or H2O2 concentration change during the reaction: Glucose + O2 → Gluconolactone + H2O2.
Étude de La Réactivite de La 7‐Phényl‐1,4‐Diazepine‐5‐One
Authors: Chammache M. , Essassi E. M. , Salem M. , Zniber R. 
Published: September 2010

AbstractThe reactivity of 7‐phenyl‐1,4‐diazepin ‐5‐ one have been described. The new compounds obtained have been characterized by 1H NMR, IR, MS and microanalysis.
An Electrochemical Study of Thiamine Disulphide on Mercury
Authors: López Fonseca J. M. , Lois B. , García Monteagudo J. C. , Sastre De Vicente M. E. 
Published: September 2010

AbstractThe electroreduction of thiamine disulphide was studied by using dc, dp, np and rp polarography in aqueous buffered media. Depending on thiamine disulphide concentration, pH, temperature and drop time, up to four waves (peaks), I‐IV, were obtained. Waves II and III are characterized as adsorption post‐waves and wave I corresponds to the “main wave”, the latter being the only wave previously described in the literature. Involvement of the product of the charge transfer reaction (thiolic form of thiamine) in an irreversible chemical reaction was detected. Taking into account additional recent kinetic studies on the structural transformations of thiamine, a mechanism for the electroreduction of thiamine disulphide that explains the observed dependence of E1/2 of I on pH is proposed.
Transformations of N‐Methyl‐4,5‐Dihydroisoxazolium Methylsulphates
Authors: Kwiatkowski Stefan , Ostrowski Stanisław 
Published: September 2010

AbstractReactions of N‐methyl‐4,5‐dihydroisoxazolium methylsulphates with: H2O, H2O2 or KMnO4, NaNO2, NEt3, NaCN, NaN3 yielded respectively: β‐methylaminoxyketones, β‐hydroxyketones, β‐(N‐nitroso)methylaminoxyketones, a mixture of N‐methyl‐2,5‐dihydroisoxazole and N‐methyl‐3‐methylenetetrahydroisoxazole, 3‐cyano‐N‐methyltetrahydroisoxazoles and 3‐azido‐N‐methyltetrahydroisoxazoles.
Selective Cleavage of Asymmetric Acetals to Hemiacetal Acetates. Ring Opening of Chlorinated 2‐Alkoxytetrahydrofuran and ‐Tetrahydropyran Derivatives
Authors: De Buyck Laurent , Verhue Ann 
Published: September 2010

AbstractAsymmetric acetals of α‐chloro and α,α‐dichloroaldehydes in acetic anhydride containing sulfuric acid afforded hemiacetal acetates at convenient rates at room temperature resp. at 127°C. The main product involved cleavage to the better stabilized α‐alkoxycarbenium ion intermediate, with a typical ratio 87:13 for ethyl:methyl and 94:6 for propyl:2‐chloroethyl. For 2‐alkoxytetrahydrofuran and ‐tetrahydropyran substrates (alkyl = methyl, ethyl, 2‐chloroethyl) ring cleavage was predominant (89‐98%).The kinetics were affected by several factors: the concentration of strong acid and of acetic anhydride (ionizing power of the medium), the ring size, nature and conformation of the 2‐alkoxygroup and by a minor side‐reaction that consumes acid by alkylation of its anion (OMe > OEt; eq. OMe > ax. OMe).
Caractéristiques Électrochimiques Et Énergétiques D'Électrodes Composites a La Chloranile Contenant de La Tourbe
Authors: Kone A. , Dieng M. M. , Fall M. , Aaron J. J. 
Published: September 2010

AbstractThe effect of peat on several electrochemical and energetic properties of new solid composite electrodes, constituted of chloranil, peat and acetylene black has been evaluated. Optimal electrodes have been found to include 60% of chloranil, 19% of acetylene black 19% of peak and 2% of teflon. The influence of the proportion of chloranil and of the acidity of the electrolytic medium (sulfuric acid) on the capacity of the redox system has been also studied.
Molecular Interaction in Aqueous Sugar Solutions ‐ a Nuclear Magnetic Relaxation Study
Authors: Sattiacoumar S. , Arulmozhi V. 
Published: September 2010

AbstractProton Magnetic Resonance (PMR) spin‐lattice relaxation times (T1) were measured in aqueous solutions of maltose and galactose in the concentration range 0‐2 molar and at a temperature of 37° C. The spin‐lattice relaxation time (T1) is found to decrease with the increase of sugar concentration. On the otherhand, the relaxation time is found to be lower for maltose solutions as compared to galactose solutions. These results were discussed on the basis of molecular association between sugar and water molecules through hydrogen bonding and the two‐state fast exchange model of water molecules.
Coordination Compounds of S‐Benzyl‐(Ferrocenyl)Ethylidene‐Dithiocarbazate with Rare Earth Metals
Authors: Gang Zhao , Zhi‐Quan Jiang 
Published: September 2010

AbstractA new ligand. S‐benzyl‐(ferrocenyl)ethylidenedithiocarbazate FcC(CH3) = NNHCSSCH2C6H5 (Ftsbh) (Fc = η5‐C5H5FeC5H4) and its complexes with lanthanide, Ln(Ftsb)3 (Ln = lanthanide) have been prepared and characterized. The data of elemental analyses, IR, UV, NMR, molar conductance. TG and DTA show that the ligand coordinates with Ln(III) in thiol form with a molar ratio of 3:1. The complexes are non‐electrolytes in DMF and the C‐N bonds in complexes became very strong and much more thermostable than that in the ligand due to forming the chelate rings.
Effet du Spin Électronique Sur La Conduction De Semiconducteurs Impliques Dans des Jonctions de Type Semiconducteur‐Métal
Authors: Gire A. , Lomaglio Mme G. , Théobald J. G. 
Published: September 2010

AbstractThe spin of the electrons has an incidence on the electrical transport properties, especially on the recombination of charge carriers. The minority carriers are usually considered to have a negligible effect on the behaviour of semiconductor‐metal junctions. We describe an experience which shows, that their role is evident. The experience consists in studying the efficiency of a junction while producing E.S.R., which modifies the recombination rate of minority carriers.
Étude de La Synthèse de Tétrachalcogenofulvalenes Dissymétriquement Substitués Par Réaction de Type Wittig‐Horner
Authors: Fabre J. M. , Serhani D. , Saoud K. , Gouasmia A. K. 
Published: September 2010

AbstractThe synthesis of functionalized unsymmetrically substituted tetrathiafulvalenes 1, 2 and 3, 4 (see scheme in the introduction) was described. Two routes were used. A cross‐coupling preparation from appropriate 1,3‐dithiolium salts which offered poor yields and a WITTIG‐HORNER type reaction which was studied in details. A solvent modification in the later reaction, allowed us to improve the yield of 1 and 2 obtained selectively.
Vinylogous transamination of enamines with ene‐1,1‐diamines to diene‐1,1‐diamines
Authors: Leurs Stefan , Vandenbulcke‐Coyette Brigitte , Viehe Heinz G. 
Published: September 2010

AbstractWe report the chain extension of enamines by two carbon atoms through acid catalyzed nucleophilic substitution of the amine function by ene‐1,1‐diamines 2. By this vinylogous transamination we have prepared a series of diene‐1,1‐diamines 10a‐h, 12a‐e and diene‐1,1,4‐triamines 14a‐e.
Simple and efficient preparation of dihydropyrans and spiroketals using the intramolecular silyl modified Sakurai (ISMS) reaction
Authors: Markó István E , Bayston Daniel J. , Mekhalfia Abdelaziz , Adams Harry 
Published: September 2010

AbstractSubstituted tetrahydropyrans, spiroethers and spiroketals can be prepared in a single step using the ISMS reaction between the bis‐silylated reagent 7b and aldehydes (acetals), ketones (ketals) and ortholactones respectively. This simple methodology was applied to the rapid synthesis of a pheromone containing a [4,5]‐spiroketal unit.
Synthesis and characterization study on some metal complexes of a schiff base derived from ninhydrin with s‐methylhydrazine‐carbodithioate
Authors: Hassaan Aly M. A. 
Published: September 2010

AbstractSynthesis and characterization of a Schiff base ligand of ninhydrin with S‐methylhydrazinecarbodithioate and its chromium (III), manganese (II), iron (III), cobalt (II), nickel (II), copper (II), zinc (II), and cadmium (II) complexes are reported. Elemental analysis molar conductivity, magnetic moment, spectral 1H NMR, UV/Visible and IR data have been used to characterize these complexes. It has been found that ligand behaves as a mononegative ONS tridentate towards divalent metal ions forming 1:2 (metal:ligand) stoichiometry and as a mononegative NS bidentate towards trivalent metal ions forming 1:3 (metal:ligand) stoichiometry. For all complexes, a non‐electrolytic nature is observed. Some available spectral parameters are calculated. Octahedral and distorted octahedral geometries have been proposed for the complexes on the basis of magnetic and spectral measurements.