bluuebunny/crossref_metadata_2025_split huggingface dataset:
Proton magnetic resonance studies of specifically deuterated cyclohexane compounds. Part II. t‐Butylcyclohexane
Authors: Remijnse J. D. , van Bekkum H. , Wepster B. M. 
Published: September 2010

AbstractThe preparation and PMR investigation of some specifically deuterated t‐butylcyclohexanes is reported. The chemical shifts of the various ring protons and the vicinal axial‐equatorial coupling constants have been determined accurately. The coupling constants show that an equatorial t‐butyl group distorts the chair conformation of cyclohexane: the t‐butyl side of the ring is somewhat puckered. The chemical shifts of the ring protons of t‐butylcyclohexane differ from those of cyclohexane. In consequence the use of a t‐butyl group as a holding group in conformational analysis is not always justified.A long range coupling of 1.4 Hz is observed between 1,3‐diequatorial ring protons. This partly explains the complexity of the spectra of apparently simple spin systems of other cyclohexane derivatives.The dehydration of 3‐t‐butylperdeuterocyclohexanol using D3PO4 gives rise to a mixture of the three t‐butylperdeuterocyclohexenes. The intermediate formation of a protonated four‐membered ring is proposed in order to explain the presence of deuterium in the t‐butyl group of only 1‐t‐butylperdeuterocyclohexene.
A gas‐chromatographic investigation of the thermodynamics of solutions of some normal and branched alkanes, cyclohexane, benzene, and tetrachloromethane in apiezon M
Authors: Hammers W.E. , de Ligny C.L. 
Published: September 2010

AbstractFrom retention volumes, determined over a wide range of temperatures, solute molar volumes, and fugacities of the solute vapours, standard partial molar free enthalpies and entropies and enthalpies of mixing in infinitely dilute solution in apiezon M were calculated at a range of temperatures.The residual standard partial molar free enthalpies and entropies and the standard partial molar enthalpies of mixing of the normal and branched alkanes were interpreted with the (simplified) Prigogine solution model, those of the normal alkanes. cyclohexane. benzene, and tetrachloromethane with the solution theory of Flory, Orwoll, and Vrij.
Formation of p‐vinylguaiacol oligomers in the thermal decarboxylation of ferulic acid
Authors: Klaren‐De Wit M. , Frost D.J. , Ward J.P. 
Published: September 2010

Abstractp‐Vinylguaiacol synthesized by decarboxylation of ferulic acid [3‐(4‐hydroxy‐3‐methoxyphenyl)propenoic acid] with copper powder in refluxing quinoline was accompanied by oligomers. A dirtier and a trimer were isolated and identified as linear oligomers coupled head‐to‐tail. The trimer was a I:I mixture of (R,R + S,S) and (R,S + S,R) forms, according to its 220 MHz NMR spectrum.
Unconventional nucleotide analogues. VI. Synthesis of Purinyl‐ and Pyrimidinyl‐Peptides
Authors: de Koning H. , Pandit U.K. 
Published: September 2010

AbstractHomogeneous and heterogeneous peptides have been synthesized from pyrimidinyl‐ and purinyl‐amino acids la, b, c. Investigation of the oligopeptide derived from 1a (poly‐1a) showed no secondary structure as a result of base‐base interaction: however, the polymer was found to complex weakly with poly‐adenylic acid. Poly‐1a also exhibited a stimulation of phenylalanine incorporation in the in vitro synthesis of poly‐phenylalanine.
Cobalticenium salts. I: Reaction of cobaltocene with hydrogen halides and with triphenylphosphonium halides
Authors: van Den Akker M. , Jellinek F. 
Published: September 2010

AbstractReaction of cobaltocene with hydrogen halides HX (X = Cl, Br, I) in ethereal solution yields the ionic complexes [Cp2Co]+2[CoX4]2− in high yields. If triphenylphosphine is present in the reaction mixtures, the cobalticenium halides [Cp2Co]X are formed as the main products. Reaction of cobaltocene with hydrogen fluoride gives [Cp2Co][HF2]. The mechanisms of these reactions are discussed.
Vinyl orthoformates and vinyl acetals. Part I: Synthesis of divinyloxymethyl and diaryloxymethyl halides and carboxylates
Authors: Scheeren J.W. , van Melick J.E.W. , Nivard R.J.F. 
Published: September 2010

AbstractDiaryloxymethyl halides and divinyloxymethyl halides, formates, trichloro‐acetates, monochloroacetates, and acetates have been synthesized from corresponding vinyl orthoformates.
Deazapurine derivatives. IX: Synthesis of (7‐substituted)‐1‐, 2‐ and 3‐β‐D‐ribofuranosyl‐vic‐triazolo [4,5‐b]pyridines. 1‐Deaza‐8‐aza‐adenosine and related compounds
Authors: de Roos K. B. , Salemink C. A. 
Published: September 2010

AbstractThe direct condensation of 7‐chloro‐vic‐triazolo[4,5‐b]pyridine (I) with 2,3,5‐tri‐O‐benzoylribofuranosyl chloride (III) in nitromethane containing potassium cyanide, afforded two isomeric blocked nucleosides. Debenzoylation of these products gave the ribosides 7‐chloro‐3‐β‐D‐ribofuranosyl‐vic‐triazolo[4,5‐b]‐pyridine (VI) and its 2‐ribosylated isomer VII. From the reaction of the chloromercuri derivative ofvic‐triazolo[4.5‐b]pyridine (X) with III in boiling toluene, followed by subsequent debenzoylation of the reaction products, three isomeric ribosides were obtained: 1‐, 2‐ and 3‐β‐D‐ribofuranosyl‐vic‐triazolo[4,5‐b]‐pyridine (XVI, XV and XIV). The position of attachment of the sugar moiety to thevic‐triazolo[4.5‐b]pyridine ring system and the assignment of anomeric configuration for all nucleosides reported, are discussed. A number of 7‐substituted 3‐β‐D‐ribofuranosyl‐vic‐triazolo[4,5‐b]pyridines ‐ including 1‐deaza‐8‐aza‐adenosine (XXVI) ‐ was obtained by replacement of the chloro group of VI.
Specific tritium labelling of naphthalene and 1,2,3,4‐tetrahydronaphthalene: A comparison of the hydrogenolysis of phenyltetrazolyl ethers and halogeno compounds with different palladium catalysts
Authors: den Hollander W. , van der Jagt P. J. , van Zanten B. 
Published: September 2010

AbstractAn investigation was carried out on the specific tritium labelling of naphthalene and 1,2,3,4‐tetrahydronaphthalene (tetralin), using tritium gas as one of the reactants. It was demonstrated that specific labelling of naphthalene with deuterium or tritium was possible by catalytic hydrogenolysis of phenyltetrazolyl ethers as well as by catalytic dehalogenation of halogeno compounds, but dehalogenation gave better chemical and isotopic yields. Specific labelling of tetralin was attained only by dehalogenation with a palladium on carbon catalyst in the presence of potassium hydroxide.
Ring transformations in reactions of heterocyclic compounds with nucleophiles (V): Conversion of pyrimidine into 5‐ethyl‐2‐methylpyridine: (Preliminary communication)
Authors: van der Plas H. C. , Jongejan H. , Geurtsen G. , Vollering M. C. 
Published: September 2010

AbstractPyrimidine is converted by heating with aqueous methylamine or ammonia at 190° into 5‐ethyl‐2‐methylpyridine (5‐10%).
Purification of relatively stable compounds by partial thermolysis using a ‘tube flow’ reactor
Authors: Tinkelenberg A. , Louw R. , Kooyman E. C. 
Published: September 2010

AbstractThe practical possibilities of a tubular reactor are evaluated, aiming at the isolation of unreacted, relatively stable compounds from mixtures with more reactive contaminants. The system approaches ideal ‘tube flow’ behaviour closely enough to make the method useful on a preparative scale.
Aromatic sulfonation. Part 30: Sulfonation of anthracene with sulfur trioxide‐dioxane; slow proton transfer in the formation of 9‐anthracenesulfonic acid
Authors: Koeberg‐Telder A. , Cerfontain Hans 
Published: September 2010

AbstractSulfonation of anthracene‐9‐d with sulfur trioxide‐dioxane in dioxane as solvent at 40° leads to 31 ± 2% α‐, 8 ± 2% β‐ and 61 ± 2% meso‐substitution. The substitution at the meso‐position proceeds with a maximal substrate kinetic isotope effect of hydrogen ‐ kH/kD = 6.8 with 5.6 and 8.6 as limiting values ‐ indicating that the proton removal from the σ‐complex is rate‐limiting.From the data for anthracene‐9‐d it was calculated that the sulfonation of C14H10 leads to 21 ± 3% 1‐, 6 ± 2% 2‐ and 73 ± 5% 9‐substitution.
Alcohols as ligands. Part II: Metal(II) salts containing coordinated methanol
Authors: van Ingen Schenau A. D. , Groeneveld W. L. , Reedijk J. 
Published: September 2010

AbstractA number of complexes of the general formula M(CH30H)2+6 (Anion)−2 is reported, the anions being ClO−4, BF−4, NO−3. The cations are Mg, Mn, Co, Ni Zn and Cd, which are completely solvated by methanol in these complexes.The compounds are prepared by reaction of the metal hydrates with trimethyl orthoformate. Information about the structure of the complexes was obtained from chemical analyses, infrared spectra, ligand‐field spectra, X‐ray powder diagrams and NMR measurements.Three other compounds of the formula M(CH3OH)3SO4 are reported, with the cations Ni, Co and Zn.
The nature of the s‐s bonds in different compounds II The crystal and molecular structure of diphenyl disulfone
Authors: Kiers C. Th. , Vos Aafje 
Published: September 2010

AbstractThe crystal structure of diphenyl disulfone has been determined by X‐ray diffraction at room temperature. Observed (average) values for the bonds involving a sulfur atom are: S  S  2.193(1), SO  1.428(1), SC  1.753(1) Å. In parentheses the standard deviations for the individual bonds are given.
Synthesis of 1‐phenyl‐1,3‐propano‐2‐indanone
Authors: Fransen‐Zeilstra E. M. , Hall G. E. , Ward J. P. 
Published: September 2010

AbstractWhen benzene is refluxed with aluminium chloride one of the products formed after autoxidation is a crystalline ketone. This ketone has been identified as 1‐phenyl‐1,3‐propano‐2‐indanone by a five‐step synthesis starting from l‐phenyl‐2‐indanone. Elimination reactions from intermediate Br‐substituted cyclohexanone derivatives, and a photoelimination from a substituted 2‐indanone are described.
The coordination chemistry of phosphoryl compounds containing the ‐N(CH3)2, group. Part VI: Complexes of hexamethylphosphoramide and nonamethylimidodiphosphoramide with metal perchlorates
Authors: de Bolster M. W. G. , Groeneveld W. L. 
Published: September 2010

AbstractA number of new perchlorate complexes of the ligands hexamethylphosphoramide and nonamethylimidodiphosphoramide is reported.The compounds are characterized and identified by chemical analysis and physical measurements.A number of complexes which were reported earlier by other workers, were reprepared and their properties were studied with the aid of X‐ray powder measurements, infrared and ligand‐field spectra. In some cases this leads to quite different conclusions, which are supported by the results found for the new complexes.The raman spectrum of nonamethylimidodiphosphoramide is reported for the first time and it is shown that this facilitates the assignment of absorption bands in the complexes.It is pointed out that planarity of the six‐membered ring magnified image, which is in some way suggested by infrared and raman measurements might explain the unusual stability of complexes with the ligand nonamethylimidodiphosphoramide.
The infrared spectra of linear primary mono‐ and skipped polyacetylenic alcohols and bromides
Authors: Bus J. , Memelink A. A. 
Published: September 2010

AbstractThe infrared spectra of 2‐alkynyl, 2,5‐alkadiynyl and 2,5,8‐alkatriynyl bromides and alcohols are discussed.These types of acetylenic compounds can easily be differentiated in the 1100‐1150 cm1 region and to a lesser extent in the 2200‐2300 cm−1 region.
A convenient synthesis of L‐1‐methylhistidine and L‐1‐ethylhistidine
Authors: Beyerman H. C. , Maat L. , van Zon A. 
Published: September 2010

AbstractAlkylation of the easily accessible methyl ester of L‐Na,3‐dibenzoylhistidine with the aid of trimethyl‐ and triethyloxonium fluoroborate followed by decomposition with water and acid hydrolysis yielded L‐1 ‐methyl‐ and L‐1‐ethylhistidine respectively. Comparison with natural L‐1‐methylhistidine confirmed the structure and optical purity.
Reactions of 1‐Dodecene with a novel reaction product of formaldehyde and sulfur trioxide
Authors: Nooi J. R. , Martens R. J. , Kemper H. C. 
Published: September 2010

AbstractA 1 : 1 CH2O/SO3 product has been prepared from sulfur trioxide and trioxane or paraformaldehyde in 1,2‐dichloroethane, which was different from methylene sulfate (a 1 : 1 CH2O/SO3 compound described in the literature).In contrast to methylene sulfate, the CH2O/SO3 product reacts with 1‐dodecene in 1,2‐dichloroethane at 10°C. The main reaction leads mainly to organic sulfates. The structures of the sulfates indicate that the CH2O/SO3 compound mainly reacts similar to a formaldehyde/(Lewis) acid complex (Prins‐type reaction). The major side‐reaction leads to sulfonates. This side‐reaction is similar to the reaction of 1‐dodecene with the dioxane/SO3 complex. Other side‐reactions are acid‐catalysed isomerizations and addition of sulfonic acids and organic sulfates to 1‐dodecene to give alkyl alkanesulfonates and dialkyl sulfates.
The standard potentials of the silver/silver bromide and of the silver/silver iodide electrode in some organic solvents and their mixtures with water
Authors: Bax D. , de Ligny C. L. , Alfenaar M. , Mohr N. J. 
Published: September 2010

AbstractThe standard potentials at 25° of the Ag, AgI electrode in ethanol and ethanol‐water mixtures, of the Ag, AgBr and Ag, AgI electrodes in acetone‐water mixtures and one dioxane‐water mixture and of the Ag, AgBr electrode in 100% acetone have been determined by comparison with the known standard potentials of the Ag, AgCl electrode in these solvents.
Activation and transfer of oxygen. V. Spontaneous oxidation of 1,3,10‐trimethyl‐5,10‐dihydroalloxazine in acidic media in connection with its hydroxylating ability
Authors: Mager H. I. X. , Berends W. 
Published: September 2010

AbstractOn autoxidation several dihydroalloxazines show a strong hydroxylating ability without addition of metal compounds. The assumption in the literature that N1 ‐alkylated dihydroalloxazines (I) cannot activate oxygen was proved to be wrong. The material balance was studied both in the absence and in the presence of phenylalanine as a substrate. Both autoxidation and hydroxylation to tyrosines were in agreement with calculations based on a theory which has already been put forward.Hydroxylation of organic compounds may be inhibited by some inorganic anions. An explanation is given for the inhibition occurring in hydrochloric acid.
Deazapurine derivatives. X: Synthesis and reactions of 5,7‐disubstituted imidazo[4,5‐b]pyridines
Authors: Schelling J. E. , Salemink C. A. 
Published: September 2010

AbstractA new synthesis for 5,7‐dichloroimidazo[4,5‐b]pyridine is described. From this compound and 5‐amino‐7‐chloroimidazo[4,5‐b]pyridine a number of 5,7‐disubstituted imidazo[4,5‐b]pyridines are prepared, including 7‐aminoimidazo[4,5‐b]pyridin‐5‐one, the 1‐deaza analogue of isoguanine.
Transition points in solid antimony trichloride
Authors: Julien W. M. C. , Gerding H. 
Published: September 2010

AbstractA dilatometric investigation of solid antimony trichloride in the temperature range‐50° to +71 °C shows the presence of second order transition points at 63.5 and 70°. Raman spectra recorded at −150, −50, 0, +50, +67 and +70° show only minor changes in frequency shifts and in line intensities, except for the appearance of a 134 cm frequency shift at 67°, which is also present at 70° (solid) and in the liquid. Possible changes in intermolecular interaction, especially at the first transition point, are discussed.
Composition of polifungin, a new antifungal agent
Authors: Porowska N. , Halski L. , Płóciennik Z. , Kotiuszko D. , Morawska H. , Kowszyk‐Gindifer Z. , Bojarska‐Dahlig H. 
Published: September 2010

AbstractPolifungin is a new tetraene antibiotic complex with antifungal activity. It has been shown that four biologically active components are present in this complex, polifungin B being the main component differentiating polifungin from nystatin.
Total synthesis of modified 6‐thia‐estrogens
Authors: Könst W. M. B. , van Bruynsvoort J. , Speckamp W. N. , Huisman H. O. 
Published: September 2010

Abstract6‐Thiasteroids have been totally synthesized by reacting 2‐substituted cyclopentane‐1,3‐diones with 4‐hydroxy‐4‐vinyl thiachromanes or with the derived isothiouronium salts. Modifications of the C(13)‐substituent have also been carried out via the thallium salt of the C18‐nor‐8,14‐seco‐steroid. When using 2‐chloro‐ and 2‐acetylamino‐cyclopentane‐1,3‐diones anomalous reaction products were obtained.
Relation between structure and cholinergic activity. I. Synthesis and muscarinic activity of 5‐alkyl‐2‐methyl‐4‐trimethylammoniomethyl‐1,3‐dioxolane iodides
Authors: Elferink J. G. R. , van Noordwijk J. , Schreurs W. H. P. , Salemink C. A. 
Published: September 2010

AbstractThe preparation and muscarinic activities of a number of 5‐alkyl substituted analogues of the dioxolane of Fourneau are described. Muscarinic activity decreases rapidly when the alkyl chain lengthens, moreover a change from parasympathomimetic into parasympatholytic activity occurs. The stereochemical aspects with regard to the 5‐position are considered. The synthesis and cholinolytic effect of 2‐methyl‐c‐5‐propyl‐r‐4‐trimethylammoniomethyl‐1,3‐dioxolane iodide and the corresponding 4,5‐transcompound are described.
Substituent effects of meta and para alkyl groups on the charge transfer band in the UV spectrum of nitrobenzene
Authors: Baas J. M. A. , Wepster B. M. 
Published: September 2010

AbstractThe wavenumbers of the charge transfer band maxima in the UV spectra of a large number of 3‐, 4‐, 3,4‐, and 3,5‐alkyl‐substituted nitrobenzenes have been determined in isooctane and in ethanol. Extinction coefficients ϵmax and oscillator strengths are reported for a number of these compounds. The differences VHmax‐VRmax in isooctane reveal an order of substituent effects of alkyl groups which is not entangled with differential solvation effects. Methyl groups in the γ‐position of 4‐alkyl groups are very effective in stabilising the excitation. There is no constant ratio between the substituent effects of the alkyl groups from the 3‐ and the 4‐position. The substituent effects are approximately additive in the 3,4‐ and 3,5‐dialkyl‐substituted nitrobenzenes. Both 3‐ and 4‐alkyl groups bulkier than methyl exert a steric hindrance of the solvation in ethanol; this hindrance has been quantified for the 4‐alkyl groups.
Investigations on organogermanium compounds. XIII: Synthesis of linear peralkylpolygermanes. Mechanism of the reaction of trialkylgermyl alkali metal compounds with trialkylhalogenogermanes
Authors: Bulten E. J. , Noltes J. G. 
Published: September 2010

AbstractA full report is given of our investigations into the synthesis of a series of linear peralkylpolygermanes, both by reacting organohalogenogermanes with alkali metals and by coupling of organohalogenogermanes with trialkylgermyl alkali metal compounds2–4. The latter type of reaction always gives in addition to the asymmetric compound R3GeGeR3′, varying amounts of the symmetrical products R6Ge2 and R6′Ge2. Evidence is presented that these side‐products are formed by a nucleophilic cleavage of the GeGe bond of the primary asymmetrical coupling products, rather than by a halogen‐metal exchange reaction.
Homogeneous hydrogenation using hydrogen peroxide‐activated iridium complexes
Authors: van Rantwijk F. , Spek Th. G. , van Bekkum H. 
Published: September 2010

AbstractChlorotris (triphenylphosphine) iridium (I) and trans‐carbonylchlorobis (triphenylphosphine) iridium (I) have been treated with hydrogen peroxide to yield catalysts for homogeneous hydrogenation. Evidence is presented that the activation involves selective oxidation of one triphenylphosphine ligand.Hydrogenation of terminal or cis‐substituted olefinic double bonds, catalyzed by both complexes, is accompanied by extensive isomerization. The kinetics of the hydrogenations are rather complex and remained unexplained. Deuteration experiments revealed some details of the mechanism of hydrogen addition and exchange.
Chemistry of acetylenic ethers 98: Photochemical addition of benzophenone and 4, 4′‐dimethylbenzophenone to 1‐methoxy‐1‐propyne alkylidenecycloheptatrienes
Authors: Polman H. , Boleij J. S. M. , Bos H. J. T. 
Published: September 2010

AbstractBenzophenone and 4, 4′‐dimethylbenzophenone are added photochemically to 1‐methoxy‐1‐propyne. Besides methyl 3, 3‐diarylacrylates I, the alkylidenecycloheptatrienes II E and II Z are isolated.
Model studies for enzyme inhibition. Part V: Reactions of organophosphorus compounds with α‐cyclodextrin. A quantitative approach of model activity and stereospecificity
Authors: van Hooidonk C. 
Published: September 2010

AbstractThe bimolecular rate constants for reaction of the enantiomers of isopropyl methylphosphonofluoridate, isopropyl p‐nitrophenyl methylphosphonate and isopropyl S‐2‐dimethylaminoethyl methylphosphonothioate with α‐cyclodextrin have been calculated from the dissociation constants (Kdiss) of the prereaction 1:1 inclusion complexes and the maximal rate constants (k2max) for the ensuing nucleophilic reactions. These data are compared with the corresponding rate constants for the inhibition of acetylcholinesterase.It is concluded that the stereospecificity exhibited by α‐cyclodextrin in its reaction with enantiomeric organophosphorus compounds is reflected mainly in the nucleophilic reaction.
The interaction between polyethyleneimine and sodium dodecyl sulfate in water
Authors: van den Berg J. W. A. , Staverman A. J. 
Published: September 2010

AbstractThe amount of sodium dodecyl sulfate bound by polyethyleneimine is measured under varying concentrations of the reactants and additional ions, in particular H+ ions. The results can be interpreted consistently as the formation of uncharged complexes between the negatively charged dodecyl sulfate ions and the positively charged monomeric groups of the polyethyleneimine molecule.
A synthesis of the decapeptide sequence proposed for the LH‐ and FSH‐releasing hormone
Authors: Beyerman H. C. , Hindriks H. , Hirt J. , de Leer E. W. B. , van der Wiele A. 
Published: September 2010

AbstractThe solid‐phase synthesis is reported of the decapeptide sequence proposed for the hypothalamic hormone which releases the luteinizing hormone (LH) and the follicle‐stimulating hormone (FSH) from the pituitary, the LH‐FSH‐releasing hormone. The threshold dose of LH‐releasing activity was determined in rabbits and rats.
C‐nitroso compounds. Part XXV: Oxidation of alkenes with a photochemically generated adduct between oxygen and 2‐methyl‐2‐nitrosopropane
Authors: Maassen J. A. , de Boer Th. J. 
Published: September 2010

AbstractRed light irradiation of 2‐methyl‐2‐nitrosopropane (t‐BuNO) in benzene in the presence of oxygen with a high O2/t‐BuNO ratio leads mainly to 2‐methyl‐2‐nitropropane. In styrene part of the solvent is also attacked to give benzal‐dehyde and formaldehyde. Similar photolysis in β‐pinene and cyclohexene gives oxidation on the allylic position, leading to mixtures of α‐β unsaturated alcohols and ketones. Because no double bond shift takes place when β‐pinene is oxidized, singlet oxygen is not involved.In all cases, the reactive species seems to be an adduct of oxygen and t‐BuNO, which can add to double bonds (styrene) or abstract allylic hydrogens (β‐pinene, cyclohexene).
Synthesis, optical rotatory dispersion and absolute configuration of (+)‐N‐methylallosedridine [(+)‐(2R)‐2‐{(2S)‐2‐hydroxypropyl}‐1‐methylpiperidine] from sedum sarmentosum bunge and its isomers
Authors: Beyerman H. C. , Bordes B. S. L. , Maat L. , Warnaar F. M. 
Published: September 2010

AbstractThe four isomers of N‐methylsedridine {2‐(2‐hydroxypropyl)‐1‐methylpiperidine} were prepared in different ways. The absolute configurations were determined using both optical rotatory dispersion and chemical correlation. The alkaloid occurring in Sedum sarmentosum Bunge is (+)‐(2R)‐2‐{(2S)‐2‐hydroxypropyl)}‐1‐methylpiperidine, (+)‐N‐methylallosedridine (IIIa).