bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of 4‐hydroxy‐5‐methyl‐2,3‐dihydrofuran‐3‐one from D‐ribose 5‐phosphate
Authors: Peer H. G. , van den Ouweland G. A. M. 
Published: September 2010

Abstract4‐Hydroxy‐5‐methyl‐2,3‐dihydrofuran‐3‐one (I) is prepared in reasonable yield by β‐elimination of phosphoric acid from D‐ribose 5‐phosphate. The reaction mechanism is discussed and supported by tracer experiments.
The unit cell dimensions of some alkali lead and alkali strontium halides
Authors: Jansen P. W. J. 
Published: September 2010

AbstractThe unit‐cell dimensions of the compounds AB2X5 with A = K, Rb or NH4; B = Pb or Sr and X = Cl or Br have been determined. The alkali strontium chlorides are isostructural with the alkali lead chlorides and bromides.
Configuration and conformation of all four cocaines from nmr spectra
Authors: Sinnema A. , Maat L. , van der Gugten A. J. , Beyerman H. C. 
Published: September 2010

AbstractThe configurations of (±)‐allococaine and (±)‐allopseudococaine have been determined, for the first time in an unambiguous way, by means of NMR spectroscopy. The known configurations of (±)‐cocaine and (±)‐pseudococaine receive independent confirmation.The preferential conformation of the piperidine ring of the tropane nucleus is found to be the chair form in all four isomers, and also in the methyl esters of the four corresponding isomers of ecgonine.The preparation of (±)‐allococaine and (±)‐allopseudococaine has been improved.
Chemistry and spectroscopy in strongly acidic solutions. Part XVI: Evaluation of 13C‐H coupling constants in protonated formic acid
Authors: Hogeveen H. , Mackor E. L. , Ros P. , Schachtschneider J. H. 
Published: September 2010

AbstractThe values of 13C‐ Ha,13C‐ Hβ,13C‐ Hγ coupling constants in the isomeric protonated formic acid species (I) and (II) were measured at low temperatures. Double‐resonance measurements showed the signs of the13C‐Ha and13C‐Hβ coupling constants to be opposite to that of the positive13C ‐Hγ coupling constant.Quantum‐mechanical calculations of the Iterative Extended Hückel type were performed for several isomers of protonated formic acid in order to obtain expressions for the molecular orbitals and values for the one‐electron energies of these systems. The results of these calculations were used to obtain approximate theoretical values for the spin‐spin coupling constants. Theoretical and experimental values agree only qualitatively.
The UV absorption of substituted benzhydrols and of the corresponding 2‐(dimethylamino)ethyl ethers
Authors: Rekker R. F. , Nauta W. Th. 
Published: September 2010

AbstractThe present paper gives UV measurements on a number of substituted benzhydrols and the corresponding 2‐(dimethylamino)ethyl ethers. As far as investigated, all spectra clearly demonstrate the existence of interaction between the component chromophoric parts, despite the presence of a saturated carbon atom as the connecting link. In its absorption, every asymmetrically substituted compound shows additivity with respect to its symmetrically substituted analogues.
Synthesis of some derivatives of cephalosporamine: On the synthesis of cephalosporin antibiotics II
Authors: Reinhoudt D. N. , Tan H. S. , Beyerman H. C. 
Published: September 2010

AbstractErlenmeyer condensations of 1,3‐dihydroxyacetones (9 and 12) with 2‐phenyl‐1,3‐oxazolin‐5‐one gave α‐benzamido‐β‐hydroxymethylbutenolide (15). Starting from the latter, via α‐benzamido‐β‐chloromethylbutenolide (18) α‐benzamido‐β‐acetylthiomethylbutenolide (19, N‐benzoyl‐S‐acetylcephalosporamine) was obtained. Compound 19 could be converted by an acid‐catalysed alcoholysis into α‐benzamido‐β‐mercaptomethylbutenolide (22, N‐benzoyl‐cephalosporamine), which showed unexpected stability.The structure proof of the α‐benzamidobutenolides obtained (15 to 22) was furnished by correlation of α‐benzamido‐β‐triphenyl‐methylthiomethylbutenolide (20) with the reaction product of the known α‐amino‐β‐triphenyl‐methylthiomethylbutenolide (8) with benzoyl chloride. Spectroscopic evidence agreed with this.Preparation of butenolides in this way is of potential interest for a synthesis of Cephalosporin C.
Aromatic halogen displacement by cyclohexyl radicals
Authors: Shelton J. Reid , Uzelmeier Christopher W. 
Published: September 2010

AbstractCyclohexyl radicals displace either halogen or hydrogen from dihalobenzenes to give mono‐ and di‐halogenated cyclohexylbenzenes. The unusual reactivity of fluorine in the sequence, F > I > Br > Cl, shows that breaking of the carbon‐halogen bond is not involved in the rate‐determining step. Halogens ortho to each other are consistently more reactive toward displacement than hydrogen in the same molecule. This higher reactivity is explained by a combination of electronic and steric effects plus the ability of halogen ortho to the reaction site to stabilize a cyclohexadienyl radical, while the preference for fluorine displacement is attributed to the nucleophilic nature of the cyclohexyl radical which reacts more readily at a position of low electron density.
Anion polarization and lattice energy of some metal halides MX2 and MX3 with layer and chain structure
Authors: Arlman E. J. 
Published: September 2010

AbstractThe contribution of anion polarization to the lattice energy of inorganic compounds with layer‐ and chain‐lattice structure is calculated using an extension of the simple ionic model. This consists of assigning to the anions ideal dipoles, the direction of which is deduced from the structure. With the aid of a theorem due to de Wette the polarization energy per anion is expressed in terms of the form

containing the polarizability and diameter of the anion and two geometric constants representative of the ionic and the dipole field at the anion site. I and D depend on the crystal structure in an analogous way to the Madelung constant. By combination of polarization energy, Coulomb energy and Born repulsion energy, formulae for the lattice energy are obtained. They allow a quantitative representation of some trends in crystal chemistry and a rather close approximation to the thermodynamic lattice energy of real compounds.
NMR Spectra of some secondary substituted adamantanes. Part II: 2,4‐Dihalo‐substituted adamantanes
Authors: van Deursen F. W. , Udding A. C. 
Published: September 2010

AbstractThe NMR spectra of 2e,4e‐ and 2a,4e‐dihalo‐substituted adamantanes are analysed with the INDOR technique and the configurations are evaluated.The observed chemical shifts are in agreement with the calculated ones using the substituent shifts from the 2‐monosubstituted adamantanes. Only a remarkable deviation exists for the protons geminal to the substituents, which is very deceptive for the evaluation of the configurations of 2,4‐disubstituted adamantanes.
Investigation into the conformation of a series of 2‐alkyl‐1‐(o‐alkylphenyl)cyclohexanols. Part 3: Synthesis and conformation of some trans‐1‐(o‐alkylphenyl)decahydro‐1‐naphthols
Authors: Timmerman H. , Th. Nauta W. 
Published: September 2010

AbstractSeveral trans‐1‐(o‐alkylphenyl)decahydro‐1‐naphthols were synthesised from trans‐octahydro‐1(2H)‐naphthalenone with aryl‐lithium. Their conformations were assigned on the ground of the chemical shift of the hydroxyl proton. A comparison was made with the corresponding cyclohexanols.
The system zirconium‐selenium: Structures of the phases Zr3Se4 and Zr2Se3
Authors: Salomons W. , Wiegers G. A. 
Published: September 2010

AbstractThe system zirconium‐selenium has been investigated in the composition range ZrSe2ZrSe. In samples prepared from the elements at 800°C only the phases Zr1+xSe2 (with a Cd(OH)2 type structure) and Zr3Se4 were observed, in agreement with previous studies. The phase Zr3Se4 was found to have a rhombohedral structure intermediate between the CdCl2 and NaCl types; a 3.753 Å, c  18.703 Å. In samples prepared at 950° or 1200° a new hexagonal phase (a  3.744 Å, c  12.51 Å) of approximate composition Zr2Se3 was found; this phase was found to be isotypic with Ti2S3.
Substituent effects of pyrrolidino and piperidino groups in benzoic acids and nitrobenzenes
Authors: Weringa W. D. , Janssen Matthijs J. 
Published: September 2010

AbstractBenzoic acids and nitrobenzenes, substituted in the para position with a pyrrolidino or a piperidino group are compared with dialkylaminobenzoic acids and dialkylaminonitrobenzenes.The acidities of the substituted benzoic acids, the polarographic halfwave potentials of the nitrobenzenes and the rate of reduction of the nitrobenzenes with disodium disulfide, give the following order of electron releasing effect of the substituents:piperidino < dimethylamino < pyrrolidino < diethylamino < di‐isopropylamino.No steric inhibition or promotion of resonance is found with the pyrrolidino group, but steric inhibition of resonance seems important in the piperidinobenzenes. The basicities of the dialkylaminobenzoic acids show a greatly different sequence which is attributed to the changing configuration around the basic site.
HF‐SbF5 catalysed isomerization of n‐butane‐1‐13C
Authors: Brouwer D. M. 
Published: September 2010

Abstractn‐Butane‐1‐13C is isomerized by “HF‐SbF5” to n‐butane‐2‐13C without intermediate or concurrent isomerization to isobutane. The rate of the13C‐scrambling reaction is only slightly lower than that of the isomerization of n‐pentane to isopentane. This result strongly supports the hypothesis that alkylcarboniumion rearrangements that involve a change in the degree of chain branching proceed via a protonated cyclopropane ring. That no isobutane is formed can be explained by the ring opening of protonated methylcyclopropane to the isobutyl structure being “slow” because it involves the formation of an (incipient) primary ion. This is not contradictory to the fact that t‐butyl ions are formed in strong acids from n‐butyl precursors under different conditions. The difference between HF‐SbF5 catalysed and aluminium halide‐hydrogen halide catalysed isomerizations of butane is discussed.
Conformation of open‐chain compounds. Part 4. Carbon‐halogen stretching frequencies, dipole moments, and conformation of some 1‐halogeno‐1‐halogenomethylcyclohexanes and related compounds
Authors: Altona C. , Hageman H.J. , Havinga E. 
Published: September 2010

AbstractCarbon‐halogen stretching frequencies of 1‐chloro‐l‐chloromethyl — (1), 1‐bromomethyl‐1‐chloro‐ (2), 1‐bromo‐1‐bromomethyl‐ (3), 1‐chloromethyl‐1‐hydroxy‐ (4), 1‐bromomethyl‐1‐hydroxy‐ (5) and 1‐bromomethyl‐1‐methoxycyclohexane (6) are reported. The frequencies were assigned to specific conformations by comparing the observed values with those predicted from the known “stretching parameters” of the several possible chemical/geometrical arrangements in the vicinity of the C‐Hal bond (P. T, S calssification).The dipole moments of1, 3and5in carbon tetrachloride and benzene were measured to obtain quantitive information on the conformational properties of this class of compounds.The dihalides exist as mixtures ofantiandgaucheconformations (tertiary halogen axial) with theantiform predominating on account of its lower energy content. A normal “benzene effect) is found.
The cause of the medium effect upon the rate of the electron‐exchange reaction between thallium(I) and thallium(III)
Authors: Gelsema W.J. , de Ligny C.L. , Blijleven H.A. , Hendriks E.J. 
Published: September 2010

AbstractThe thallium(I)‐thallium(III) electron‐exchange rate has been measured at 25° in aqueous perchloric acid‐lithium perchlorate mixtures of varying acid concentration, at three values of the ionic strength.In these mixtures no detectable medium effect exists, i.e., the specific rate constant is independent of the acid concentration at each value of the ionic strength studied.The medium effect that has been found in aqueous perchloric acid‐sodium perchlorate mixtures must therefore be explained as the result of a variation of the activity coefficients of the reacting species and not, as has been done by the majority of authors, as a result of displacement of hydrolysis equilibria.
Synthesis of some aliphatic dienals
Authors: Ward J. P. , van Dorp D. A. 
Published: September 2010

Abstract4,7‐Decadienal, 4,7‐tridecadienal, 5,8‐tetradecadienal and 6,9‐dodecadienal (all‐cis) have been synthesized by coupling 1‐bromo‐2‐pentyne and 1‐bromo‐2‐octyne with the diethyl acetals of 4‐pentynal, 5‐hexynal and 6‐heptynal, followed by partial hydrogenation and hydrolysis. The formation of 1,1,4‐triethoxy‐2,5‐hexadiyne from 1,1‐diethoxy‐2‐propyne is also described.
A new method for handling volatile and hygroscopic substances in bomb calorimetry. Enthalpy of formation of liquid butanol‐1
Authors: Mosselman C. , Dekker H. 
Published: September 2010

AbstractA new method has been developed for handling volatile and hygroscopic substances in bomb calorimetry. A platinum crucible, covered with a platinum lid and sealed with vaseline, is used. The lid is opened by a counterweight when the vaseline is ignited. The enthalpy of formation of liquid butanol‐1 was measured and compared with literature values.
The chemistry of cycloheptatriene. Part XVI . Sigmatropic shifts of hydrogen in methylcycloheptatriene
Authors: Ter Borg A. P. , Kloosterziel H. 
Published: September 2010

AbstractUpon heating 7‐methylcycloheptatriene the 3‐, 1‐ and 2‐isomers are successively formed by 1‐5 shifts of hydrogen. The rate constants at 140° have been determined. Photochemical 1‐7 shifts of hydrogen are also reported: the 1‐isomer yields preferentially the 7‐isomer and little of the 2‐isomer, whilst the 2‐isomer yields mainly the 3‐isomer and little of the alternative 1‐isomer.
1,3‐oxathioles as intermediates in nucleophilic additions to 1‐acylthio‐1‐alkynes
Authors: Drenth W. , Nieuwdorp G. H. E. 
Published: September 2010

AbstractIn methanol, 1‐acetylthio‐1‐alkynes are converted into 1,3‐oxathiolesmagnified imageIn aqueous solution a similar intermediate is formed with a rate independent of the acidity and with a negligible solvent deuterium isotope effect. This intermediate rearranges to the end‐product at a rate that decreases with the acidity:magnified image
Poisoning effects of hydrogen sulfide on noble metal electrodes. Part I. Rest potentials and stationary current density ‐ potential measurements on Pt and Au electrodes in H2SO4 solutions containing H2S
Authors: Ijzermans A. B. 
Published: September 2010

AbstractThe influence of H2S upon electrochemical reactions on Pt, platinized Pt, Au and Au/Pt electrodes in H2SO4 solutions has been investigated by means of rest potential measurements and stationary current vs. potential measurements under potentiostatic control.In 0.5 M H2S04 saturated with H2S these electrodes reached a rest potential of 165 ± 10 mV (nhe), which was found to depend linearly on pH with ‐ 59 ± 2 mV/pH and on P with ‐40 ± 15 mV/log P.Current density vs. potential curves showed an increase of hydrogen over‐potential under the influence of H2S and also a change of reactions at potentials > 0 mV. In this region the potential determining reaction may be an exchange of H+ ions with H atoms absorbed in the noble metal, proceeding along adsorbed HS− ions. Additional evidence supporting this view was obtained by studying the effect of scraping on rest potentials.
Polymer network characterization by means of swelling pressure and unilateral compression data
Authors: van de Kraats E. J. , Potters J. J. M. , Winkeler M. A. M. , Prins W. 
Published: September 2010

AbstractThe characterization of a polymer network entails at least the determination of three parameters, viz. the number of elastically effective chains v, the polymer diluent interaction parameter χ and the reference degree of swelling qo, at which the chains do not exert elastic forces on the crosslinks. In this study networks are described which are prepared by crosslinking poly‐(p‐nitrophenyl methacrylate) in solution with hexamethylene diamine. This yields gels of accurately known content of chemical crosslinks. Swelling pressure measurements (0–3 atm) coupled with unilateral compression data have been performed in order to determine the network parameters and to check the various forms of the theory of swollen rubber elastic networks. It is found that the functional relationships prescribed by the theory are indeed obeyed over a wide range of swelling from volume ratios of 5 to 20. The parameter v is constant over the whole range. If the number of chemically crosslinked chains is assumed to be equal to the number of elastically effective chains in the network, the data support the Flory‐Wall theory, although a modified form of the Hermans theory is also applicable. The reference degree of swelling qo is very large in these gels because they are formed by crosslinking in dimethylformamide in which the molecular chains are aggregated, while the swelling is measured in nitrobenzene in which the aggregates dissociate. This feature is also responsible for the interesting fact that it is the elastic free energy rather than the free energy of dilution which is negative and thus promotes the swelling of these gels.
The crystal structure of a monoclinic modification of 4‐cyano‐N‐[2‐(p‐methoxyphenyl)‐ethyl]pyridinium iodide, C15H18IN2O
Authors: Dik‐Edixhoven Lotty , Stam C. H. 
Published: September 2010

AbstractThe modification of 4‐cyano‐N‐[2‐(p‐methoxyphenyl)ethyl]pyridinium iodide investigated is monoclinic, space group Cc, Z = 4, cell dimensions a = 11.853, b = 12.485, c = 11.281 Å, β = 114.21°.The conformation of the molecule is gauche about the central CC bond with a dihedral angle of 68°. The crystal structure does not explain the intramolecular charge transfer bands observed in the UV absorption spectrum.
Chemistry and spectroscopy in strongly acidic solutions. Part XXIII: Reversible reaction between carbonium ions and hydrogen
Authors: Hogeveen H. , Gaasbeek C.J. , Bickel A.F. 
Published: September 2010

AbstractThe reduction of aliphatic carbonium ions to alkanes with molecular hydrogen is reported. A kinetic study of this reaction has been made in the two‐phase solvent system HFFreon 113. The following parameters were investigated: temperature, hydrogen pressure, deuterium isotope effect and structure of the carbonium ion.The kinetics of the reverse reaction ‐ formation of carbonium ions from alkanes and protons in the system HF‐SbF5 ‐ were studied for the case of trimethylcarbonium ion. From the equilibrium constant an upper limit for the basicity of isobutene has been calculated.
Studies on polypeptides. Part VII, : Synthesis of DL‐, L‐ and D‐2‐amino‐6‐dimethylamino‐4‐hexynoic acid
Authors: Jansen A. C. A. , Weustink R. J. M. , Kerling K. E. T. , Havinga E. 
Published: September 2010

Abstractl‐ and D‐2‐amino‐6‐dimethylamino‐4‐hexynoic acid were synthesized, starting from L‐ and D‐propargylglycine obtained by enzymatic resolution of DL‐N‐ace‐tylpropargylglycine with acylase I. The dimethylaminomethylene group was introduced through a Mannich reaction of the N‐acetylpropargylglycine ethyl esters with formaldehyde and dimethylamine (Scheme A). By reaction of L‐ and D‐2‐amino‐6‐chloro‐4‐hexynoic acid, prepared by enzymatic resolution of the DL‐N‐acetyl compound, with dimethylamine identical end products were obtained, but in much lower yields (Scheme B).
Reaction between chlorodiphenylacetic acid and thiourea
Authors: Rahman Aziz Ur , Gatica Hector S. E. 
Published: September 2010

AbstractThe reaction between chlorodiphenylacetic acid and thiourea has been studied, using the former as such, as ethyl ester and the acid chloride, with or without the use of ethanol as solvent. The experimental conditions for the preparation of 5,5‐diphenylpseudothiohydantoin and the formation of 2‐(diphenylmethyl)imino‐4‐oxo‐5,5‐diphenylthiazolidine and/or bis(diphenyl‐methyl) disulfide as secondary products involving decarboxylation of chlorodiphenylacetic acid have been discussed.
Transannular interactions and reactions in a seven‐membered heterocyclic ring‐system
Authors: de Groot Ae. , Boerma J. A. , Wynberg Hans 
Published: September 2010

AbstractInfrared spectroscopic studies have shown that transannular interactions occur in 4‐t‐butyl‐3,3,6,6‐tetramethyl‐1‐thiacycloheptan‐4‐ol (VI). These interactions do not occur in 3,3,6,6‐tetramethyl‐1‐thiacycloheptan‐4‐ol (III) and only to a minor extend in 3,3,4,6,6‐pentamethyl‐1‐thiacycloheptan‐4‐ol (IV) and in 3,3,6,6‐tetramethyl‐4‐isopropyl‐1‐thiacycloheptan‐4‐ol (V).Treatment of 3,3,6,6‐tetramethyl‐1‐thiacycloheptane‐4,5‐diol (XVI) with acid gave a transannular rearrangement involving participation of the sulfur atom to 3,3,6,6‐tetramethyl‐1‐oxa‐4‐thiabicyclo[3.3.0]octane (XVII). Treatment of 5‐hydroxy‐3,3,6,6‐tetramethyl‐1‐thiacycloheptan‐4‐one with triphenyl‐phosphine dibromide gave a transannular rearrangement to 2‐isobutylidene‐4,4‐dimethyl‐3‐oxotetrahydrothiophene (XXVII).
Synthesis of 1,4‐, 1,5‐, 2,6‐ and 2,7‐di‐t‐butylnaphthalene and of 1,4‐, 1,5‐, 2,6‐ and 1,8‐diisopropylnaphthalene
Authors: van Bekkum H. , Nieuwstad Th. J. , van Barneveld J. , Klapwijk P. , Wepster B. M. 
Published: September 2010

AbstractMixtures of 2,6‐ and 2,7‐di‐t‐butylnaphthalene, obtained by the t‐butylation of naphthalene, can be conveniently separated making use of the fact that only the 2,6‐isomer gives an inclusion compound with thiourea.1,4‐ and 1,5‐di‐t‐butylnaphthalene as well as 1,4‐ and 1,5‐diisopropylnaphthalene have been prepared starting from 1,4‐ and 1,5‐naphthalene‐dicarboxylic acid, respectively. The NMR spectra of these compounds reveal downfield shifts for the peri protons.1,8‐Diisopropylnaphthalene was synthesized by an eight step synthesis starting from 1,8‐naphthalenedicarboxylic anhydride.
Diacetamide as a chelating anion
Authors: Hinze A. G. , Groeneveld W. L. 
Published: September 2010

AbstractThe preparation of diacetamide as chelating anion (DA) with the cations Na, Mg, Zn, Ni and Al is reported. The infrared spectra of Na(DA), Mg(DA)2·2NH3, Zn(DA)2, Ni(DA)2·2NH3 and A1(DA)3 are discussed. There is strong evidence for coordination occurring through oxygen.
The compound AsCl5·SbCl5 and the non‐existence of AsCl5
Authors: Brinkmann F. J. , Gerding H. , Olie K. 
Published: September 2010

AbstractWe have tried to prepare AsCl5 at low temperature by interaction of AsCl3 and Cl2 in a sealed tube. The Raman spectrum of the solid is a superposition of the vibrational spectra of AsCl3 and Cl2.Also the compound AsCl5 · SbCl5 has been studied and from its Raman spectrum the structure is AsCl4+SbCl6−.
NMR spectra and configuration of some methylallylic anions
Authors: Heiszwolf G. J. , van Drunen J. A. A. , Kloosterziel H. 
Published: September 2010

AbstractThe NMR spectra of trans‐ (A) and cis‐3‐methyl‐trans‐l‐phenylallyl anion (B), of cis‐l‐methylpentadienyl anion and of cis‐l‐methyl‐5‐oxapentadienyl anion are described. A is obtained by abstraction of a proton from l‐phenyl‐trans‐2‐butene at low temperature. At 0° it largely isomerizes to B. Several aspects of the configuration of these anions are discussed.
Substituent effects in the dehydration of 2‐aryl‐3‐methyl‐2‐butanols and in the subsequent isomerization of 2‐aryl‐3‐methyl‐1‐butenes in sulfuric acid‐acetic acid and in dimethyl sulfoxide
Authors: Kieboom A. P. G. , van Bekkum H. 
Published: September 2010

AbstractThe dehydration of a series of 2‐aryl‐3‐methyl‐2‐butanols and the subsequent isomerization of the 2‐aryl‐3‐methyl‐l‐butenes primarily formed to the corresponding 2‐butenes have been studied in sulfuric acid‐acetic acid and in dimethyl sulfoxide.The selective formation of the 2‐aryl‐3‐methyl‐l‐butenes during the dehydration is explained in terms of steric repulsion in the transition state.For the isomerization of 2‐aryl‐3‐methyl‐l‐butenes Hammett rho values of ‐ 3.8 and ‐ 2.0 apply in sulfuric acid‐acetic acid and in dimethyl sulfoxide, respectively. The kinetic isotope effects support a mechanism in which the rate determining step is the loss of the methine proton to give the 2‐aryl‐3‐methyl‐2‐butene.