bluuebunny/crossref_metadata_2025_split huggingface dataset:
The phase angle in second harmonic alternating current polarography
Authors: Kooijman D. J. , Sluyters J. H. 
Published: September 2010

AbstractSecond harmonic polarograms in which, as predicted by theory, every reversible redox system gives rise to two peaks have been described in the literature1, 2, 3. In this paper the π radians phase difference between these two peaks is demonstrated, making use of the second harmonic content of the output of the oscillator driving the polarographic circuit. Anomalies in the case of the Tl(Hg)/Tl⊕‐ and the In(Hg)/In⊕⊕⊕‐electrode are discussed.
The condensation of 2,6‐dimethylphenol with glyoxal and with benzil
Authors: Mcgowan J. C. , Anderson Janet M. , Walker Nancy C. 
Published: September 2010

Abstract1,1,2,2‐Tetrakis(4‐hydroxy‐3,5‐dimethylphenyl)ethane has been prepared by the condensation of 2,6‐dimethylphenol with glyoxal. The tetraacetate has been isolated, after acetylation, from the product of the reaction between 2,6‐dimethylphenol and α,β‐dichlorovinyl phenyl ether and the tetramethyl ether has been obtained directly from 2,6‐dimethylanisole and glyoxal sulfate.Benzil and 2,6‐dimethylphenol can be condensed to give benzoyl‐4,4′‐dihydroxy‐3,3′,5,5′‐tetramethyltritane and there is evidence that the dimethyl ether of this compound is formed when 4‐methoxy‐3,5‐dimethylbenzophenone is reduced with zinc dust in acetic acid.
Studies on polypeptides II: Synthesis of the heptapeptides (des‐Asp1) ‐Lys2‐Ile5‐angiotensin II, (des‐Asp1) ‐D‐Lys2‐Ile5‐angiotensin II, (des‐Asp1) ‐Orn2‐Ile5‐angiotensin II, (des‐Asp1)‐Cit2‐Ile5‐angiotensin II and the hexapeptide Val‐Tyr‐Ile‐His‐Pro‐Phe
Authors: Schattenkerk Cecile , Visser G. Heymens , Kerling K. E. T. , Havinga E. 
Published: September 2010

AbstractExperimental data are reported on the syntheses of the angiotensin II hexapeptide Val‐Tyr‐Ile‐His‐Pro‐Phe and of the heptapeptides obtained by coupling the hexapeptide benzyl ester with the p‐nitrophenyl esters of benzyloxycarbonyl L‐lysine, D‐lysine, L‐ornithine and L‐citrulline and subsequent hydrogenolysis of the protecting groups.
Niobium and tantalum diselenides
Authors: Kadijk F. , Huisman R. , Jellinek F. 
Published: September 2010

AbstractNiobium and tantalum diselenides have been found to exist in the following polymorphous forms: 2s‐NbSe2, 3s‐NbSe2, 4s‐NbSe2, 2s‐TaSe2, 3s‐TaSe2, 4s‐TaSe2, and 6s‐TaSe2. Unit‐cell dimensions are collected in Table I and the crystal structures of the various forms are schematically shown in Fig. 1. All the polymorphs have hexagonal or rhombohedral layer structures. In the 2s‐, 3s‐ and 4s‐ phases the metal atoms have a trigonal‐prismatic environment, but in 6s‐TaSe2 half of the metal atoms have octahedral and half have trigonal‐prismatic coordination. The conditions of preparation of the various forms are discussed. Excess of selenium over the composition MSe2 leads to mixtures of the MSe3 and MSe2 phases. Excess of metal results in the formation of phases of the type M1+xSe2, where the additional metal atoms are accommodated in the octahedral interstices between the MSe2 slabs.
The enthalpy of solution of caesium fluoride in water at 25.00°C
Authors: Somsen G. , Weeda L. 
Published: September 2010

AbstractThe enthalpy of solution of CsF in water at 25.00°C has been carefully measured with an adiabatic calorimeter. The value at infinite dilution is: ΔH°sol = −36.08 ± 0.17 kj/mole.
The influence of steric and electronic factors on acidity. III. Cinnamic Acids, substituted in α‐, β‐ or Ortho‐Positions
Authors: Hogeveen H. 
Published: September 2010

AbstractThe apparent acidity constants of a series of ortho‐, α‐ and/or β‐substituted cinnamic acids (cis‐ and trans‐), with substituents CH3, Br and Cl, have been measured in 50% (by vol.) aqueous ethanol at 25°.The data on α‐ and/or β‐substitution by Br and Cl are discussed on the basis of electronic substituent effects. Similar substitution by CH3 invokes the enhanced secondary steric effect of this group and a large departure from additivity of substituent effects is observed in α,β‐dimethyl‐trans‐cinnamic acid.The acidity constants of β‐substituted cis‐cinnamic acids follow the Hammett equation with satisfactory fit.Ortho‐substitution by Cl in cis‐cinnamic acid probably implies a direct field effect between substituent and carboxylic anion.
Studies in IVth group organometallic chemistry. XVI: Synthesis of organogermanium compounds containing the p‐phenylene group. Some infrared characteristics of p‐phenylene derivatives of silicon, germanium, tin and lead
Authors: Leusink A. J. , Noltes J. G. , Budding H. A. , van der Kerk G. J. M. 
Published: September 2010

AbstractA few oligomeric and polymeric p‐phenylenegermanes have been prepared by Wurtz‐type condensation reactions from p‐chlorophenyl‐ and chlorogermanes. The oligomeric and polymeric products obtained have been characterized by infrared spectroscopy, elementary analysis and molecular weight determinations.Infrared spectra in the rocksalt region of phenyl and p‐phenylene derivatives of silicon, germanium, tin and lead are discussed. The spectra of the p‐phenylene compounds show some characteristic absorption bands shifting to lower frequencies as the weight of the metal atoms in the molecule increases.
Studies in the zinc reduction series: Relationship of zinc and acid to zinc and alkali reductions of aldehydes and ketones
Authors: Risinger G. E. , Garrett J. M. , Winkler J. A. 
Published: September 2010

AbstractThe zinc and alkali reductions of benzaldehyde, acetophenone, and derivatives of these compounds are discussed. Further evidence is presented to support the bimolecular nature of the reductions. It is also concluded that the major differences between acid and alkali reductions reside in secondary effects of the reaction conditions rather than in the reductive portion of the reaction.
Acetate pyrolysis in the gas phase; a proposed reaction mechanism
Authors: Rummens F. H. A. 
Published: September 2010

AbstractThe pyrolysis of some acetates has been studied in the gas phase, at low concentrations, normal total pressure and in the temperature range 450‐650°K. Reaction rates, activation data and reaction products indicate that, for allyl‐acetate derivatives, the activated complex consists of an anti‐bonding electronical state involving a homolytic cleavage of the R‐OCOCH3 bond. Linalyl acetate, neryl acetate and geranyl acetate particularly, are shown to have a common activated complex. As a consequence, the tertiary linalyl acetate will, upon heating, isomerise partly to the primary neryl and geranyl acetates in a 1,3 rearrangement reaction.
The synthesis of certain furyl‐substituted polyheterocyclic six‐membered rings
Authors: Holland Dewey G. , Amstutz E. D. 
Published: September 2010

AbstractInterest in the antibacterial drug, 5‐nitrofurfural semicarbazone has led to the synthesis of a number of heterocyclic systems in which ring‐closure has been carried out on the semicarbazone (or similar) structure.
Aromatic sulfonation XI: Sulfonation of benzene and toluene with sulfur trioxide; sulfone formation and sulfonic acid isomer distribution.
Authors: Cerfontain H. , Telder A. , Vollbracht L. 
Published: September 2010

AbstractThe sulfonation of benzene and toluene with sulfur trioxide without solvent has been studied extensively.With benzene at low conversion benzenesulfonic acid and diphenylsulfone are the only products. At 25° the sulfone: sulfonic acid ratio changes from 0.2 to 0.6 on varying the SO3 : C6H6 ratio from 0.13 to 1.3. At a SO3 : C6H6 ratio > 1.3 benzene‐1,3‐disulfonic acid and diphenylsulfonesulfonic acid are found among the reaction products as well. With toluene the sulfone formation is less than with benzene.The isomer distribution of the monosulfonic acids formed in the sulfonation of toluene has been determined at various temperatures between −44 and 65°. Under all conditions the degree of meta‐substitution is low (1‐5%) whereas that of para‐substitution is high (∼ 80%). The difference in activation enthalpy between para‐ and meta‐substitution is −2.7 ± 0.4 kcal · mole −1, that between para‐ and ortho‐substitution 1.3 kcal · mole −1. The latter enthalpy difference is explainable by an intramolecular hyperconjugative proximity effect in the transition state leading to ortho‐substitution. The entropy of activation is greater for para‐ than for ortho‐substitution, indicating steric hindrance for ortho‐substitution.The formation of sulfonic acid and sulfone is discussed in terms of the mechanism:magnified image
Trityl derivatives of amines: IIIreplacement of an N‐alkyl group of aromatic secondary amines by the trityl group
Authors: Verkade P. E. , Tollenaar F. D. , van Rij J. H. , van der Goot H. 
Published: September 2010

AbstractTritylation of N‐methyl‐para‐toluidine, N‐ethyl‐para‐toluidine, and N‐methyl‐para‐chloroaniline resulted in the N‐trityl derivatives of the corresponding aromatic primary amines. The tritylation thus was accompanied by a dealkylation. N‐trityl‐N‐methyl‐para‐toluidine could be prepared.
Diuretics I: 8‐Sulfamoyltheophylline and 7‐substituted derivatives
Authors: Dolman H. , van der Goot J. , Mos G. H. , Moed H. D. 
Published: September 2010

Abstract8‐Sulfamoyltheophylline (V) was prepared by oxidative chlorination of 7‐benzyl‐8‐mercaptotheophylline, followed by amidation and debenzylation.This compound, built up from two diuretic principles, appeared to have no diuretic properties. On the other hand the intermediate 7‐benzyl‐8‐sulfamoyl‐theophylline exhibited an appreciable diuretic activity, while lacking the other pharmacological properties of theophylline. In addition this compound inhibited carbonic anhydrase. On the basis of these findings the synthesis was undertaken of a number of other 7‐substituted 8‐sulfamoyltheophyllines.The present report deals with the preparation of these heterocyclic sulfonamides, derived from V by the introduction of alkyl, aralkyl and aryl groups at the 7‐position.
pH dependence of the synthesis of isopelletierine from Δ1‐piperideine
Authors: Wisse J. H. , de Klonia H. , Visser B. J. 
Published: September 2010

AbstractThe synthesis of isopelletierine from Δ1‐piperideine and acetoacetic acid was investigated in the pH region 1 to 12. Paper chromatography was used to analyze the reaction mixtures. Depending on reaction time fair to good yields were obtained over the pH range 2 to 12. The experimental data are discussed in the light of two mechanisms proposed by Schöpf et al.
Transport in charged membranes
Authors: Dorst W. , Staverman A. J. , Caramazza R. 
Published: September 2010

AbstractUsing the formalism of irreversible thermodynamics, general conditions are derived for osmotic salt and solvent permeation. It is found that in many types of low charged membranes abnormal osmosis may occur; for the more selective ion exchangers, however, solvent flow is usually directed towards the concentrated phase, whereas electrolyte flux may be parallel or opposed to the activity gradient, regardless of the nature of the membrane. Application of the theoretical results in a particular system requires membrane composition data and leads to a set of “friction coefficients” rik. Determination of all rik values even in a simple system like sodium chloride, water and membrane requires an extensive set of experimental data. Though the complete set has not yet been obtained, rik values could be estimated from data on osmosis, transference, conductivity and diffusion. The friction between co‐ion and membrane appears to have a predominant effect on dialysis efficiency.
Titration of molybdenum (V) with ceric sulfate, using methyl orange and methyl red as indicators
Authors: Rao K. Bhaskara 
Published: September 2010

AbstractThe suitability of Methyl Orange and Methyl Red as indicators in the titration of molybdenum (V) with ceric sulfate has been investigated. It has been found that molybdenum (V) can be titrated with ceric sulfate at room temperature (1) in hydrochloric acid medium with 2‐3 drops of 0.2% Methyl Orange as indicator; and (2) in sulfuric acid medium with 2‐3 drops of 0.2% Methyl Orange or Methyl Red as indicator.
Diuretics III: Derivatives of 7‐benzyl‐8‐sulfamoyltheophylline
Authors: Dolman H. , van Der Goot J. , Moed H. D. 
Published: September 2010

AbstractThe synthesis of a number of derivatives of the diuretic compound 7‐benzyl‐8‐sulfamoyltheophylline (1) is described. These new compounds were obtained by introducing substituents in the benzyl group and by altering the sulfamoyl function; they also include two isomers of I.
Reaction of steroidal alcohols with isobutene. Usefulness of t‐butyl as a hydroxyl‐protecting group in a synthesis of testosterone
Authors: Beyerman H. C. , Heiszwolf G. J. 
Published: September 2010

AbstractAcid‐catalysed addition of isobutene to steroidal alcohols gives the t‐butyl ethers in high yields. These ethers are acid‐labile, but alkali‐resistant.The t‐butyl group is readily split off with trifluoroacetic acid.The usefulness of the method is demonstrated by a simple synthesis of testosterone benzoate from dehydroepiandrosterone.
Resolution of isopelletierine: A second synthesis of pelletierine
Authors: Beyerman H. C. , Maat L. 
Published: September 2010

AbstractThe resolution of 1‐(2‐piperidyl)propan‐2‐one (isopelletierine) with the enantiomeric 6,6′‐dinitrobiphenyl‐2,2′‐dicarboxylic acids, as described by Galinovsky, Bianchetti, and Vogl, was modified and extended. We thus obtained pelletierine picrate and pelletierine sulfate with melting points and optical rotations in agreement with the values recorded in the literature for these derivatives of the natural product.
The dehydrobromination of 1,2‐dibromo‐1,2,3,4‐tetrahydronaphthalene
Authors: Willems A. G. M. , Pandit U. K. , Huisman H. O. 
Published: September 2010

AbstractDehydrobromination of 1,2‐dibromo‐1,2,3,4‐tetrahydronaphthalene with piperidine has been shown to give 1‐bromo‐3,4‐dihydronaphthalene.
On the titanium‐carbon bond in CH3TiCl3
Authors: la Lau C. 
Published: September 2010

AbstractAvailable spectral data on CH3TiCl3 — although far from complete ‐ suffice to estimate the Ti‐C and Ti‐Cl stretching force constants. The former is of particular interest.The assignment of the skeletal vibrations is briefly discussed in view of conflicting conclusions in literature.Although a refined force field (Urey‐Bradley Field) might be preferred in principle, arguments are given for the use of the valence‐force‐field approximation in the present case. The calculations are based on the pseudo five‐mass system XTiCl3, of point group C3v.Assuming valence forces, the most appropriate two of the three frequency equations for the totally symmetric (a1) vibrations of this system have been used.The same procedure was applied to the related molecules CH3SiCl3 and CH3SnCl3; the combined results indicate the soundness of this approach.The force constant thus found for this Ti‐C bond has the rather low value 1.85 ± 0.2 × 104 dyn/cm.
The reaction of 2‐picolyllithium with schiff bases
Authors: Shuman Richard F. , Amstutz E. D. 
Published: September 2010

AbstractThe reaction of 2‐picolyllithium with Schiff bases produced N,1‐disubstituted 2‐(2′‐pyridyl)ethylamines in fair to good yields with a few exceptions. Schiff bases derived from N‐methylpyrrole‐2‐carbaldehyde and aniline or 4‐chloroaniline undergo addition with 2‐picolyllithium followed by spontaneous deamination producing 2‐{2′‐[2″‐(N″‐methylpyrryl)]vinyl}pyridine. A similar addition‐deamination sequence occurred using 2‐quinaldyllithium and N‐[4′‐(2″‐diethylaminoethoxy)benzylidene]‐4‐chloroaniline. Benzylmagnesium chloride was also reacted with Schiff bases to produce N,1‐disubstituted phenethylamines.
Studies in group IV organometallic chemistry. XVIII: The reaction of trialkyltin hydrides with alkyl propiolates
Authors: Leusink A. J. , Marsman J. W. , Budding H. A. , Noltes J. G. , van der Kerk G. J. M. 
Published: September 2010

AbstractThe reaction of trialkyltin hydrides with alkyl propiolates results in the formation of at least six products. The structure of five compounds has been established by gas chromatography, infrared and nuclear magnetic resonance spectroscopy, and elementary analysis.The main products are shown to be α‐trialkylstannyl‐ and cis‐ and trans‐β‐trialkylstannyl‐acrylates. With decreasing size of the substituents on tin nonterminal addition of the trialkylstannyl group, resulting in the formation of α‐trialkylstannylacrylate, becomes the predominant reaction.
The molecular structure of two isomers of S6(NH)2
Authors: van de Grampel J. C. , Vos Aafje 
Published: September 2010

AbstractPreliminary results of the X‐ray investigation of the crystal structure of the S6(NH)2 isomer with m.p. 130°C are reported. The NH‐groups in the eight‐membered ring of the S6(NH)2 molecules are in 1‐4 position.
Alkali metal hyperfine splitting and oscillation of the alkali ion in the alkali‐radical ion complex of pyracene
Authors: de Boer E. 
Published: September 2010

AbstractThe ESR spectra of the ion pairs consisting of the anion of pyracene and the potassium or sodium cation, in 2‐methyltetrahydrofuran, at low temperatures exhibit a line width alternation which is caused by the oscillation of the cation in the potential well. The behaviour of the metal hyperfine interaction in rubidium‐and cesium‐pyracene complexes in relation to temperature has led us to the conclusion that the spin density at the alkali nucleus is composed of negative and positive contributions. The difference in temperature dependence between the two results in a reversal of the sign of the spin density at the alkali nucleus at a very specific temperature, depending on the solvent used.
Ring closure with incorporation of hydrazine during Wolff‐Kishner reduction
Authors: Egmond G. J. N. , van Gorkom M. , van Dorp D. A. 
Published: September 2010

AbstractTwo cyclopentapyridazinones, 6,7‐dihydro‐5H‐4‐hydroxy‐7‐pentylcyclopenta‐[c]3(2H)‐pyridazinone and 4a,5,6,7‐tetrahydro‐4H‐7‐pentylcyclopenta[c]3(2H)‐pyridazinone, have been obtained as reaction products of the attempted Wolff‐Kishner reduction of ethyl (2‐oxo‐3‐pentylcyclopentyl)glyoxylate.
On the impedance of galvanic cells: XIII. Characteristics of streaming mercury electrodes
Authors: Ijzermans A. B. , Sluyters J. H. 
Published: September 2010

AbstractMethods for evaluating the effective length of the streaming mercury electrodes according to Heyrovsky1 and Schwabe2 have been indicated. At open circuit the charging of the double layer causes changes of concentration at the electrode surface. Only at the former type of electrode do these give rise to a shift of the electrode potential.
On the impedance of galvanic cells: XIV. The impedance and admittance of streaming mercury electrodes; experimental verification
Authors: Ijzermans A. B. , Sluyters J. H. 
Published: September 2010

AbstractThe views developed in part XII1 and part XIII2 of this series are verified by experiment. Measurements at the streaming mercury electrodes according to Heyrovsky3 and Schwabe4 are found to agree perfectly. From the results the reaction rate constants of the system Zn++/Zn(Hg) both in 1 M KCl and in 0.88 M NaClO4 + 10−3 N HClO4 are calculated. The diffusion constant of the Hg2++ ion in 1 N HClO4 and the thickness δ of the diffusion layer are reported.
On the impedance of galvanic cells: XV. Evidence for the occurrence of Zn+ ions from d.c. and complex plane polarograms at the streaming zinc amalgam electrode
Authors: Ijzermans A. B. , Sluyters‐Rehbach M. , Sluyters J. H. 
Published: September 2010

AbstractFrom d.c. and a.c. polarographic data of the reaction Zn++/Zn, especially from those obtained at a streaming amalgam electrode, it is concluded that this reaction may possibly be described as a one‐electron transfer step and a subsequent dismutation of the occurring univalent zinc ion. As regards the elucidation of mechanisms of electrode reactions, this method seems more informative in comparison with other methods.
The system CoSO4‐H2O; vapour pressure measurements from 0° TO 150°
Authors: Broers P. M. A. , van Welie G. S. A. 
Published: September 2010

AbstractA systematic investigation has been carried out on the vapour pressure curves with the following result:the quadruple‐point H7H6LG* lies at 44.7° ± 0.1 and 63.7 ± 0.3 mm Hgthe quadruple‐point H6H1LG lies at 64° ± 1 and 158 ± 5 mm HgThe following three phase equilibria were defined as completely as possible between 3° and 150°: H7LG, H6LG, H1LG, H7H6G and H6H1G.The following equations hold:for the H6LG equilibrium: log pmm = ‐ 2173 ± 25/T + 8.646 ± 0.003for the H7H6G equilibrium: log pmm = ‐ 2681 ± 25/T + 10.233 ± 0.008for the H6H1G equilibrium: log pmm = ‐ 2679 ± 15/T + 10.148 ± 0.004The following heats of hydration were calculated:H6 + H2OL → H7 (25°): ‐ 1750 ± 110 cal/mol. H6H1 + 5 H2OL → H6 (25°): ‐ 8680 ± 350 cal/mol. H1
Studies in group IV organometallic chemistry. XIX: The reaction of trialkyltin alkoxides with (thio)acylamides and (thio)carbamates
Authors: Noltes J. G. 
Published: September 2010

AbstractThe preparation and in particular the structure of nitrogen‐containing organotin compounds obtained by the reaction of triethyltin methoxide with a number of (thio)acylamides and (thio)carbamates are discussed.
Investigations on sterols XXVII: Synthesis of some stereoisomeric steroids and determination of the additional chemical shifts of the 18‐ and 19‐methyl protons
Authors: Halkes S. J. , Havinga E. 
Published: September 2010

AbstractAdditional chemical shifts of the 18‐ and 19‐methyl protons in four 9,10‐stereoisomeric steroid series are determined. Differences between the values derived for steroids with the 8β,9β,10α‐, the 8β,9β,10β‐, the 8α,9α,10α‐ and those with the natural configuration are discussed. The synthesis of some 9β‐steroid hormone analogues and of pregnanes and androstanes, isomeric at C‐8, C‐9 and C‐10, is described.
Studies on vitamin D and related compounds XIX: Optical rotatory dispersion of some 9,10,13‐stereoisomeric steroid 5,7‐dienes
Authors: Jacobs H. J. C. , Havinga E. 
Published: September 2010

AbstractThe rotatory dispersion curves of ergosterol and its three 9,10‐isomers (9β;10α;9β,10α) have been measured throughout the absorption band. The compounds show multiple Cotton effect curves in which the fine structure of the corresponding ultraviolet absorption band is reflected.The identity of sign (positive) of the Cotton effects of 9β‐ and 10α‐ergosterol is ascribed to the presence of a boat conformation in ring C of the 9β‐isomer. The analogous 9β‐compound with 13α‐configuration, in which ring C can exist in the chair conformation, shows a Cotton effect of opposite sign in agreement with this hypothesis.
Oligomers of diphenylketene
Authors: Das H. , Kooyman E. C. 
Published: September 2010

AbstractDiphenylketene (I) may be dimerized to form a. a cyclobutadione (IIa)1; b, a β‐lactone (IIb)2. Evidence is presented to suggest that a third dimer has the structure 1,3‐dioxo‐2,2,4‐triphenyltetralin (IIc). This compound reacts with (I) to produce a trimer (III), presumably the diphenylacetic ester of the enol form of IIc. Two compounds reported in the literature as diphenylketene dimers have been demonstrated to be 2,3‐diphenylindole and the ester, 2,3,4‐triphenylnaphthyl diphenylacetate.
Enthalpies of solvation of alkali halides in formamide. I: The enthalpies of solution of alkali halides in formamide
Authors: Somsen G. , Coops J. 
Published: September 2010

AbstractThe heats of solution of 18 alkali halides in anhydrous formamide at concentrations of about 0.01 molal and at 25° have been measured with an adiabatic calorimeter. Some physical properties of formamide have been determined. By applying the extended Debije‐Hückel theory the enthalpies of solution at infinite dilution were calculated. The difference in enthalpies of solution of the fluorides, chlorides, bromides and iodides, respectively, in water and in formamide appeared to be a constant, independent of the cation. An explanation in terms of van Eck's theory of ionic solvation is given.