bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure and physical properties of aluminium alkoxides: 1. Mass spectra of aluminium isopropoxides
Authors: Fieggen W. , Gerding H. , Nibbering N. M. M. 
Published: September 2010

AbstractThe mass spectrum of aluminium isopropoxide has been investigated using an AEI‐MS 9 mass spectrometer.The results indicate that the vapour of the solid consists largely of tetramer species; dimer and trimer are possibly present also in minor quantities.Probable fragmentation schemes are deduced from comparison of mass spectra of unlabelled and deuterated samples (deuterated at the secondary carbon atom of the isopropyl group). The tetramer molecular ion loses an isopropoxy radical or, successively, a methyl radical and a molecule of acetaldehyde, followed by the elimination of di‐isopropyl ether. A mechanism for this reaction is proposed. The further fragmentation may involve the loss of propene, di‐isopropyl ether and/or aluminiumoxide isopropoxide.
Palladium‐Catalysed reactions of unsaturated compounds in non‐aqueous solvents: The PdII‐catalysed halogen displacement in vinyl chloride by carboxylate and alcoholate
Authors: Kohll C. F. , van Helden R. 
Published: September 2010

AbstractIn the presence of catalytic amounts of divalent palladium salts vinyl chloride reacts with acetate ions in acetic acid or dimethylformamide solution to produce vinyl acetate in high yield. The reaction was found to be first‐order both in catalyst and in acetate concentration. Chloride anions inhibit the reaction by reducing the effective catalyst concentration by formation of the tetrachloropalladium complex.The mechanism of the reaction is discussed in terms of a displacement of chloride by acetate via a π‐olefin‐PdII complex. The vinylation reaction is considerably accelerated by addition of catalytic amounts of ferric acetate/lithium chloride (molar ratio 1).Also discussed is the influence on the reaction of the solvent and of various transition metal salts. The palladium‐chloride‐catalysed halogen displacement in 2‐chloropropylene by acetate ions in acetic acid was found to produce isopropenyl acetate and acetone + acetic anhydride, which indicates that attack of acetate occurs at the carbon atom carrying the chlorine. Reaction of alcohols with vinyl chloride in the presence of a base (alcoholate or tert‐amine), using palladium chloride as catalyst yields acetaldehyde dialkylacetales. Halogen exchange in vinyl bromide by chloride in dimethylformamide solution using palladium chloride as catalyst proved to be possible.
Mechanistic aspects of the palladium (II)‐catalysed synthesis of vinyl acetate from vinyl chloride
Authors: Volger H. C. 
Published: September 2010

AbstractLabelling with deuterium has shown that in the conversion of vinyl chloride into vinyl acetate by sodium acetate in glacial acetic acid at 60‐70°C in the presence of catalytic amounts of palladium chloride, (i) the acetate enters at the chlorine‐carrying carbon atom and(ii) the geometric configuration of the vinyl chloride is lost in the vinyl acetate produced. An addition‐elimination mechanism is proposed.
The determination of the solubilities of some n‐alkanes in water at different temperatures, by means of gas chromatography
Authors: Nelson H. D. , de Ligny C. L. 
Published: September 2010

AbstractGas chromatography has been used to determine the solubility in water of pentane, hexane, heptane and octane at different temperatures. From the results the standard free enthalpy, enthalpy and entropy of solution have been calculated.
Complexes with ligands containing nitrile groups: Part VI: Some methyl cyanide adducts of metal chlorides
Authors: Reedijk J. , Groeneveld W. L. 
Published: September 2010

AbstractSeven new metal chloride adducts with methyl cyanide, viz. MgCl2(CH3CN)2, NiCl2(CH3CN), CdCl2(CH3CN), GaCl3(CH3CN)2, InCl3(CH3CN)2, TlCl3(CH3CN)2 and SnCl4(CH3CN)3, are described.Methyl cyanide coordinated via the nitrogen in these compounds was demonstrated with the aid of infrared spectra. Further characterization and identification of the adducts was obtained from X‐ray powder diagrams, ligand‐field spectra, Raman spectra, far‐infrared spectra and conductivity data.
Polynuclear heterocyclic systems. Part VI: Synthesis of perhydropyridazo[1,2‐a]cinnoline
Authors: de Waard E. R. , Neeter R. , Pandit U. K. , Huisman H. O. 
Published: September 2010

AbstractIn a model study directed towards the synthesis of 5,10‐diazasteroids, piperidazine was condensed with 2‐methoxycarbonylmethylcyclohexanone (2) to give decahydro‐Δ7a(11a)‐6‐oxopyridazo[1,2‐a]cinnoline (4). Reduction of 4 with lithium aluminium hydride yielded decahydro‐Δ7a(11a)‐pyridazo[1,2‐a]cinnoline (5). Subsequent reduction of 5, either catalytically or with sodium borohydride, proceeded stereospecifically to the perhydropyridazo[1,2‐a]cinnoline (8), with B/C cis ring fusion.
Byproducts in the cyclization of ψ‐ionone to β‐ionone; structural determination of two new ionone isomers
Authors: Kruk C. , de Boer Th. J. , Haring H. G. , Ter Heide R. , Boelens H. 
Published: September 2010

AbstractIt is shown that the well known acid‐catalysed cyclization of ψ‐ionone leads to the formation of small amounts of the spiro‐dihydrofuran XV, the cyclohexadienylic ketone XVI, and the unsaturated ketones XVIIa and b. These are all isomers of ionone; the first two have hitherto not been described in the literature, whereas XVII has been obtained by a different route as a mixture of cis‐trans isomers.The structural proof of these products is based mainly on spectroscopic data.
Phase transitions in the nickel selenide Ni3Se2 and related phases
Authors: Stevels A. L. N. , Bouwma J. , Wiegers G. A. , Jellinek F. 
Published: September 2010

AbstractThe thermal behaviour of Ni3Se2 has been studied by differential thermal analysis and by high‐temperature X‐ray diffraction. Ni3Se2 is rhombohedral at low temperature and face‐centred cubic at high temperatures. The transition between the two forms shows a strong thermal hysteresis. When heating, the transition occurs at about 600° C. On cooling the face‐centred cubic form is transformed to a metastable body‐centred tetragonal form at about 560°; this form converts itself to the stable rhombohedral form at a temperature between 550° and 510° (depending on the cooling rate). The metastable form is stabilized if the metal is partly substituted by Co or Fe, or if part of Se is substituted by Te. A corresponding metastable form of Ni3S2 could not be detected. The various modifications observed for Ni3S2,Ni3Se2 Ni3(Se1.6,Te0.4) and Ni3Te2 are compared.
Determination and interpretation of the differential titration curves of proteins: The differential curves of bovine methemoglobin, CO‐hemoglobin and serum albumin
Authors: de Bruin S. H. , van Os G. A. J. 
Published: September 2010

AbstractIn this paper a refinement of the usual experimental titration procedure of proteins is described, by means of which the differential titration curve can be obtained with good accuracy. From this curve the positions of the inflection points of the normal titration curve can be localised with better precision, and, as is shown, the analysis of the differential curve has certain advantages above that of the normal curve. The capabilities of experimental and analysing procedure are illustrated by results, obtained with the proteins bovine methemoglobin (MetHb), bovine CO‐hemoglobin (HbCO) and bovine serum albumin (BSA).
The conformation of non‐aromatic ring compounds. XLVIII: The crystal structure of trans‐syn‐trans‐2,3,5,6‐tetrachloro‐1,4‐dioxane
Authors: Rutten Elisabeth W. M. , Nibbering N. , Macgillavry Caroline H. , Romers C. 
Published: September 2010

AbstractCrystals of trans‐syn‐trans‐2,3,5,6‐tetrachloro‐1,4‐dioxane are monoclinic prismatic. The space group is P21/n, a = 6.724, b = 7.552, c = 7.626 Å, β = 93.13° and Z = 2. The structure has been solved by Patterson methods and refined by use of integrated photographic copper data measured with a microdensitometer.The molecule has a chair conformation with all chlorine atoms in axial positions and with symmetry ī. Due to steric repulsions by the halogen atoms the chair is rather flat. The mean endocyclic torsional angle is 40°. In agreement with similar observations in other dioxane compounds the C‐Cl bond lengths (average value 1.823 Å) are rather long.
Semi‐empirical prediction of bond lengths and conformations
Authors: Dallinga G. , Ros P. 
Published: September 2010

AbstractFor a number of cyclic hydrocarbons we compared overlap populations, obtained by applying a Mulliken population analysis to the results of an extended Hückel calculation, with experimental bond lengths. We analysed the effect of a refinement, viz. the introduction of non‐bonded interactions. Further, we discuss the use of orbital energies in predicting relative stabilities of isomers and conformers.
Palladium‐catalysed reactions of unsaturated compounds in non‐aqueous solvents: Synthesis of vinyl acetate via palladium salt/ethylene complexes
Authors: van Helden R. , Kohll C. F. , Medema D. , Verberg G. , Jonkhoff T. 
Published: September 2010

AbstractThe reaction of ethylene with palladium acetate in acetic acid solvent produces vinyl acetate. The rate of this reaction increases considerably upon addition of small amounts of sodium acetate, lithium chloride or lithium chloride/ferric acetate to the system. The reaction is first‐order with respect to both the palladium acetate and the catalyst (NaOAc, LiCl, LiCl·Fe(OAc)3) concentration. In reactions starting from PdCl2 and NaOAc the rate was found to be proportional to the PdCl2 and NaOAc concentrations. In addition, in one case (LiCl· Fe(OAc)3) the rate was shown to be proportional to the ethylene concentration.A mechanism is proposed according to which the reaction proceeds via species of the type C2H4· PdOAcX2− ; vinyl acetate is formed through displacement of a hydrogen atom in the olefin molecule by coordinated acetate.The overall rate was found to be strongly influenced by the ligands bound to the metal; it increases in the order:

The effect of ferric acetate on the rate is tentatively explained on the basis of an increased transfer of charge in the intermediate C2H4· PdOAcX2− complex. The fact that in the displacement of Cl− by acetate in the corresponding vinyl chloride complex (C2H3Cl. PdOAcCl2−) the overall rate is lower is attributed to the formation of vinyl chloride/PdOAcCl2− complexes proceeding less readily than that of ethylene complexes.In the LiCl‐catalysed reaction the formation of vinyl acetate was found to be completely inhibited at high concentrations of chloride ions with respect to palladium acetate; under these conditions ethylene is dimerized to butylenes.Depending on the conditions of the reaction various by‐products are formed: acetaldehyde, ethylidene diacetate, ethyleneglycol acetates, butenes. The formation of these products is discussed in relation with other studies.Finally, the results are presented of some studies on the oxidation with oxygen ‐ of palladium metal in acetic acid to palladium acetate.
α‐Diazosulfones as proton donors in hydrogen bonding
Authors: Engberts J. B. F. N. 
Published: September 2010

AbstractThe PMR spectra of three aryl‐ and two alkyl‐sulfonyldiazomethanes in aliphatic and aromatic solvents have been studied. Solvent effects on the chemical shift of the methine proton indicate that this proton participates in rather strong hydrogen bonding. Relative to an inert solvent like carbon tetrachloride, the observed solvent shifts are mainly dependent on acceptor ability and magnetic anisotropy effect of the solvent molecules. In solvents of weak acceptor ability, intermolecular association between α‐diazosulfone molecules results in concentration dependent chemical shifts of the methine proton.
Ring transformations in reactions of heterocyclic compounds with nucleophiles (III): Conversion of pyrimidine and some of its methyl derivatives by hydrazine and by methylhydrazine sulfate into pyrazoles and methylpyrazoles
Authors: van der Plas H. C. , Jongejan H. 
Published: September 2010

AbstractInvestigations on ring contraction of pyrimidine and some of its homologues into pyrazoles have been extended.When pyrimidine, 4‐methyl‐ and 4,6‐dimethylpyrimidine are allowed to react with hydrazine, pyrazole, 3(=5)‐methylpyrazole and 3,5‐dimethyl‐pyrazole, respectively are formed in excellent yields. The same compounds, when treated with methylhydrazine sulfate yield 1 ‐methylpyrazole, an isomeric mixture of 1,3‐ and 1,5‐dimethylpyrazole and 1,3,5‐trimethylpyrazole, respectively. The quaternary salts 1‐methylpyrimidinium iodide and 1,4,6‐trimethylpyrimidinium methyl sulfate are converted by hydrazine into pyrazole and 3,5‐dimethylpyrazole.A mechanism of this ring transformation, involving an open‐chain intermediate, is proposed.
Ring transformation in reactions of heterocyclic halogeno compounds with nucleophiles (XIII): Conversion of some 5‐substituted 4‐chloro‐2‐phenylpyrimidines into 4(5)‐substituted 2‐phenylimidazoles
Authors: van Meeteren H. W. , van der Plas H. C. 
Published: September 2010

Abstract5‐Amino‐4‐chloro‐2‐phenylpyrimidine and 4‐chloro‐5‐methyl‐2‐phenylpyrimidine are converted into 4(5)‐cyano‐2‐phenylimidazole and 4(5)‐ethynyl‐2‐phenyl‐imidazole, respectively, by reaction with potassium amide in liquid ammonia at ‐ 33°.
Fragmentation of molecular ions of fatty acid methyl esters into methoxycarbonylalkyl ions by electron impact
Authors: Sonneveld W. , van der Steen D. , Pabon H. J. J. 
Published: September 2010

AbstractThe fragmentation of the molecular ions of methyl octadecanoates into methoxycarbonylalkyl ions with m/e = 143 and 199 has been investigated. The contributions of three reaction types are determined with esters labelled with13C at the 8 and 14 positions. The required methyl 8‐ and 14‐13C‐octadecanoates have been synthesized by coupling a methoxycarbonylalkanoyl chloride with thiophene, followed by Wolf‐Kishner reduction, esterification, introduction of the isotopic carbon atom by acylation, again reduction and desulfurization.
Structure analysis by nmr spectroscopy of a quinone methide trimer formed by oxidation of 4‐methoxy‐2,6‐dimethylphenol
Authors: Westra J. G. , Huysmans W. G. B. , Mijs W. J. , Gaur H. Angad , Vriend J. , Smidt J. 
Published: September 2010

AbstractA detailed structure analysis by proton magnetic resonance spectroscopy has been made of the main oxidation product of 4‐methoxy‐2,6‐dimethylphenol, ano‐quinone methide trimer. Several long range spin‐spin interactions of aromatic or vinylic protons with methoxy or aliphatic protons were clearly demonstrated by multiple resonance techniques.
A new swelling pressure osmometer
Authors: van de Kraats E. J. 
Published: September 2010

AbstractA swelling pressure osmometer has been constructed in which gels can swell isotropically in interchangeable swelling chambers having accurately fixed dimensions. The gels are in contact with the pure diluent via a porous steel disc. The swelling pressure is balanced and measured directly by a mercury column which is servocontrolled by a displacement transducer attached to a thin platinum foil forming one side of the swelling chamber. The mercury column exerts a counter‐pressure on the platinum foil. If the mercury column is replaced by another counter‐pressure device, swelling pressures as high as one hundred atmospheres or as low as one hundredth of an atmosphere can be measured with an accuracy of about 1 ‰.This method of pressure detection is in principle also applicable to the determination of pressure changes at constant volume, such as occur, for example, in the study of the kinetics of phase transitions and equilibria.
Synthesis of 2‐chloro‐[2‐14C] naphthalene and [2‐14C] naphthalene
Authors: van der Jagt P. J. , den Hollander W. , van Zanten B. 
Published: September 2010

AbstractThe reaction of indene with [14C]dichlorocarbene, generated from [14C]chloroform with the aid of potassium t‐butoxide, leads to the dichlorocarbene adduct. Without isolation from the reaction mixture this adduct has been converted to 2‐chloro‐[2‐14C]naphthalene with an overall yield of 60‐67%. Catalytic dehalogenation of 2‐chloro‐[2‐14C]naphthalene yields almost quantitatively [2‐14C]naphthalene. The chemical and radiochemical purity of this compound was proved to be better than 99%.
The metabolism of hydroxyanthranilic acids. Part II: The partial purification of 3‐hydroxyanthranilate oxygenase and its action on some aminocresotic acids
Authors: Cox M. C. L. , Diamond E. M. , Levy P. R. 
Published: September 2010

AbstractA simple thirty‐fold purification of 3‐hydroxyanthranilate oxygenase from an acetone powder of rat liver is described. 2‐Amino‐3,4‐cresotic acid (III) resembles 3‐hydroxyanthranilic acid (I) when incubated with the enzyme; 2‐amino‐3,5‐cresotic acid (IV) is a competitive inhibitor; 2‐amino‐3,6‐cresotic acid (V) is inert.
Investigation into the conformation of a series of 2‐alkyl‐1‐(o‐alkylphenyl)cyclohexanols. Part 2: Synthesis and NMR spectra of some o‐alkylbenzyl alcohols
Authors: Timmerman H. , Zaagsma J. , Th. Nauta W. 
Published: September 2010

AbstractA series of o‐alkylbenzyl alcohols was synthesised; the NMR spectra were compared with those of correspondingly substituted o‐alkylphenyl cyclohexanols in order to ascertain how the o‐alkyl substituents in the cyclohexanols investigated affect the shift of the hydroxyl proton.
Thermolytic reactions of esters. Part IV. The methyl esters of cyanoacetic, acetoacetic and malonic acid
Authors: den Tonkelaar W. A. M. , Louw R. , Kooyman E. C. 
Published: September 2010

AbstractThe compounds on the title proved to be more stable than their ethyl analogues, 1,2‐acid elimination being impossible. Acetic acid causes a pronounced rate enhancement. Kinetic as well as product data ‐ including the effect of added water and/or alcohols ‐ are interpreted on the basis of acetic acid catalysed enolisation as the primary step, followed by elimination of alcohol to form a ketene derivative. In the case of dimethyl malonate, this methoxycarbonyl ketene may loose a second molecule of methanol to produce carbon suboxide.
Photoreactions of aromatic compounds. Part XV: Photosolvolysis of some 5‐substituted 3‐nitrophenyl phosphates and of 3‐nitrophenyl sulfate
Authors: de Jongh R. O. , Havinga E. 
Published: September 2010

AbstractQuantum yields have been determined for the photosolvolysis of 5‐chloro‐, 5‐bromo‐ and 5‐methyl‐3‐nitrophenyl phosphate in alkaline solutions of different pH and ionic strength. Quantum yields are found to be the same for light of 313 mμ and 265 mμ. The 5‐bromo‐ and 5‐methyl‐compounds show a behaviour comparable to that of 3‐nitrophenyl phosphate itself, be it with lower quantum yields under the same reaction conditions; the data suggest a shortening of the lifetime of the reacting excited species. 5‐Chloro‐3‐nitrophenyl phosphate reacts with water in the pH range studied with a relatively high quantum yield (0.15), probably due to the favourable electronic effect of the chlorine substituent. There is no indication of a photoreaction with OH−, not even in 0.1 molar NaOH and ionic strength ∼ 1; for this compound the reaction with the solvent (H2O) may be so fast that reactions with solutes (OH−) cannot compete. Another compound for which only a reaction with water and not with OH was observed, is m‐nitrophenyl sulfate. Here again, the quantum yield of photohydrolysis is high (0.5) and practically constant over the range pH2‐13. This makes it unlikely that protonation or deprotonation is one of the essential steps of the reaction. Cl−‐ and especially Br−‐ions only when present in high concentration (∼ 1 mole) quench the photosolvolysis of m‐nitroanisole (by OH−), and probably also the reaction of m‐nitrophenyl sulfate with water. This suggests that the reacting excited species is in the first singlet rather than in a triplet state.
Photolysis of alkyl aralkyl sulfides
Authors: Laarhoven W. H. , Cuppen Th. J. H. M. , Nivard R. J. F. 
Published: September 2010

AbstractReactions analogous to the photolytic formation of dibenzyl, stilbene and phenanthrene from dibenzyl sulfide have been observed on irradiation of various alkyl aralkyl sulfides. Exceptions were found in alkyl α‐alkylbenzyl sulfides containing a hydrogen atom at the β‐carbon relative to the aromatic ring. From these a dibenzyl derivative is obtained, but instead of stilbenes and phenanthrenes styrenes are formed. A possible explanation for the results is given.
Complexes with ligands containing nitrile groups. Part IX . Magnetic measurements on solid methyl‐cyanide solvates
Authors: Reedijk J. 
Published: September 2010

AbstractMagnetic susceptibilities and paramagnetic resonance spectra for a number of complex solvates M(CH3CN)n2+(anion), in which M = Mn, Fe, Co, Ni, Cu, Zn, n = 4 or 6 and the anion is SbCl6−, SnCl62–, TlCl4−, FeCl4−, GaCl4−, ClO4−, have been determined.The octahedral shape of the ions M(CH3CN)62+, with M = Mn, Fe, Co and Ni, has been confirmed. The ion Cu(CH3CN)62+ has been found to be distorted octrahedral. In Cu(CH3CN)4SnCl6 no copper‐copper interaction is found.The spin‐orbit coupling constants for the solvated metal ions are shown to be reduced 15‐50% compared with the free metal ions.
Electron diffraction by gases: The molecular structure of bicyclo[3.1.1]heptane
Authors: Dallinga G. , Toneman L. H. 
Published: September 2010

AbstractThe molecular structure of bicyclo[3.1.1]heptane has been investigated by means of electron diffraction of the vapour. The molecule has one plane of symmetry and an average carbon‐carbon bond length of 1.537 Å. Details of the structure are compared with those in similar molecules and differences between the carbon‐carbon bond lengths are discussed with reference to semi‐empirical predictions based on the results of MO calculations.
Chemistry and spectroscopy in strongly acidic solutions. Part XXII: Protonation of hexamethyldewarbenzene. Interconversion of exo‐ and endo‐1,2,3,4,5,6‐hexamethylbicyclo[2.1.1]hexenyl cations
Authors: Hogeveen H. , Volger H. C. 
Published: September 2010

AbstractProtonation of hexamethyldewarbenzene at low temperatures leads to formation of exo‐ and endo‐1,2,3,4,5,6‐hexamethylbicyclo[2.1.1]hexenyl cations (ratio 1:3). These ions interconvert rapidly and intramolecularly, the added proton remaining attached to the same carbon atom. The mechanism proposed for this isomerization involves tricyclic ions as intermediates. Values for the rate constant at various temperatures were obtained by comparison of the experimental NMR spectra with the computer‐simulated ones. Quenching of the ions with methanol‐sodium methoxide at low temperature afforded a number of products.
The nitration of 2‐nitro‐1,4‐di‐t‐butylbenzene: Synthesis of the three dinitro‐1,4‐di‐t‐butylbenzenes and some related compounds
Authors: Hoefnagel A. J. , Nunnink J. H. A. J. , van Veen A. , Verkade P. E. , Wepster B. M. 
Published: September 2010

AbstractNitration of 2‐nitro‐1,4‐di‐t‐butylbenzene provides a mixture from which, in addition to 2,4‐dinitro‐ and 3,4‐dinitro‐t‐butylbenzene, all three possible dinitro‐1,4‐di‐t‐butylbenzenes could be isolated. Pure 2,3‐dinitro‐ and 2,6‐dinitro‐1,4‐di‐t‐butylbenzene have been isolated for the first time. The difficult separation of a mixture of 2,6‐dinitro‐ and 2,5‐dinitro‐1,4‐di‐t‐butylbenzene was effected by using molecular sieve 10X.The 2,6‐dinitro isomer has also been prepared starting from 2,5‐dinitro‐1,4‐di‐t‐butylbenzene.Dipole moments and ultraviolet, infrared, and NMR data of the isomers are given and certain aspects are discussed.
Stereoselectivity in the complex formation of histidine with cobalt(II) and nickel(II)
Authors: Ritsma J. H. , van de Grampel J. C. , Jellinek F. 
Published: September 2010

AbstractThe stability constants of Co(II)‐ and Ni(II) complexes of L‐histidine and racemic histidine in aqueous solution have been measured. The observed difference between the stability of MDL and ML2 complexes shows a preference for the formation of the MDL molecule. The excess Gibbs energy of ½(MD2 + ML2) relative to MDL is found as 0.31 kcal/mole fir the Co(II) complex and as 0.49 kcal/mole for the Ni(II) complex.