bluuebunny/crossref_metadata_2025_split huggingface dataset:
The reaction of phenol with formaldehyde. III. selective hydroxymethylation of phenols at the ortho‐position
Authors: Peer H. G. 
Published: September 2010

AbstractThe effect of chelating substances on the orientation of hydroxymethyl groups in the reaction of phenol with formaldehyde is described.It is found that when using hydroxides of the transition metals, Cu, Cr, Mn, Ni and Co, in aequous solution at pH = 4‐5, hydroxymethylation occurs mainly at the ortho‐position.Similar results were obtained with boric acid in benzene solution.Chelate formation in the transition state for ortho‐substitution is supposed to be the basic reason for the selective catalysis.
Chemistry of acetylenic ethers XLII: A simplified method for the preparation of acetylenic thioethers; a number of new reactions of these compounds
Authors: Boonstra H. J. , Arens J. F. 
Published: September 2010

AbstractCis ethenylene‐1,2‐bis‐thioethers RSCH  CHSR can easily be prepared in liquid ammonia by treating cis or trans 1,2‐dichloroethylene with sodium amide and thiol.From these compounds acetylene thioethers HC ≡ CSR can be obtained by means of sodium amide in liquid ammonia, followed by treatment with one mole of alkyl halide. If two moles of alkyl halide R′X are used, the alkyne thioethers R′C ≡ CSR are formed in satisfactory yield.(Alkylthio)ethynylcarbinols R′R″C(OH)C ≡ CSR are the products of treatment of ethenylene‐1,2‐bis‐thioethers with sodium amide and ketones R′R″C = 0 in liquid ammonia.Addition of hydrogen chloride to (ethylthio)ethyne gives 1‐ethylthio‐1‐chloroethylene.Reaction of (ethylthio)ethyne with acetone under the influence of boron fluoride produces a 50% yield of ethanethiol β,β‐dimethylacrylate; similarly 1‐ethylthio‐1‐propyne and acetone form ethanethiol α,β,β‐trimethylacrylate.The Mannich reaction of (ethylthio)ethyne with formaldehyde and diethylamine gives (C2H5)2NCH2C ≡ CSC2H5 in very high yield.Long heating of (ethylthio)ethyne at 90‐100° causes the formation of 2‐(ethylthio)thiophene with much tar.
Analyses of small samples of monazites with a gamma scintillation spectrometer
Authors: Couwenberg G. H. M. , Kooy C. L. D. , Korvezee A. E. 
Published: September 2010

AbstractThe possibility of applying gamma ray analysis to approximately 50 mg samples of monazite has been investigated. Three ranges of low energy gamma radiation, under 0.3 MeV, were counted with a Gamma Scintillation Spectrometer.This extremely simple method led to very good results with samples containing only one radioactive component. With monazites containing uranium as well as thorium, the latter component being in excess, results were also good. For uranium contents that were only a few tenths of a per cent, the results did not attain the precision of chemical analysis.In a leached mineral where the simultaneous contents of uranium, radium in excess and thorium had to be determined, the method failed, due to the smallness of the contribution of UX in the emitted radiation with respect to that of the radium family. In this case we were able to calculate an approximate value for the thorium content and make a rough estimate of the total radium content of the mineral.With this spectrometer the use of longer counting times gives only a slight improvement in the precision of the counts. The use of somewhat larger samples will however diminish the important background fraction in the low activity countings and hence it will give a corresponding increase in the reliability of the results.
The photochemical reactions of 1,3‐cyclohexadiene and α‐phellandrene
Authors: de Kock R. J. , Minnaard N. G. , Havinga E. 
Published: September 2010

AbstractData are presented in support of the view that the photochemical conversion of ergosterol into precalciferol, involving a cleavage of the cyclohexadiene‐ring, belongs to a generally occurring type of photochemical isomerisations. Under the influence of ultraviolet light 1,3‐cyclohexadiene itself is converted to trans‐1,3,5‐hexatriene. Irradiation of α‐phellandrene (1‐methyl‐4‐isopropyl‐1,5‐cyclohexadiene), results in a mixture of compounds, mainly consisting of (geometrical isomers of) 3,7‐dimethyl‐1,3,5‐octatriene. By ultraviolet‐ and infrared spectroscopy, hydrogenation, gas liquid partition chromatography and ozonolysis the identity of these irradiation products could be established. Indications were found that optically active α‐phellandrene might partly racemise during irradiation.Prolonged irradiation of cyclohexadiene and α‐phellandrene resulted in a large decrease of the extinction in the region 220‐300 mμ. On irradiation of the compounds at liquid air temperature in solid solution such a decrease was not observed. From this it was tentatively concluded that in the course of the photochemical reaction at room temperature a relatively slow di‐ or polymerisation takes place.
Synthesis of a tyrosine “homologue” of oxypressin
Authors: Beyerman H. C. , Bontekoe J. S. , Koch A. C. 
Published: September 2010

AbstractThe synthesis is described of the protected linear decapeptide: N‐benzyloxycarbonyl‐S‐benzyl‐L‐cysteinyl‐L‐tyrosyl‐L‐tyrosyl‐L‐phenylalanyl‐L‐glutaminyl‐L‐asparaginyl‐S‐benzyl‐L‐cysteinyl‐L‐prolyl‐L‐leucylglycineamide (III, Fig. 2).Removal of the blocking groups from III, followed by oxidation, yielded a preparation assumed to contain a “homologue” of oxypressin with two consecutive molecules of tyrosine instead of one (Fig. 1, n = 2).
On the impedance of galvanic cells: II. Experimental verification
Authors: Sluyters J. H. , Oomen J. J. C. 
Published: September 2010

AbstractIt is shown by experiment that both types of frequency dependency of the cell impedance, treated in Part I, occur. From the results the diffusion constant of the Hg++2 ion in 1M HClO4 and the reaction rate constant of the zinc amalgam electrode in 1M NaClO4 + 10−3M HClO4 base electrolyte are calculated. In addition the value of the double layer capacity of the zinc amalgam electrode is reported.
Chemistry of acetylenic ethers XLV: Some reactions of esters of (ethylthio)propynoic acid
Authors: Bonnema J. , Arens J. F. 
Published: September 2010

AbstractThe addition of ethanethiol to ethyl (ethylthio)propynoate I (R = C2H5) afforded ethyl α,β‐bis(ethylthio)acrylate III (R = C2H5).Reduction of I gave γ‐(ethylthio)allyl alcohol IX, which was converted into β‐(ethylthio)propionaldehyde X by acid.The Diels‐Alder addition of 1,3‐butadiene to I (R = C2H5) gave rise to ethyl 2‐ethylthio‐3,6‐dihydrobenzoate XII.Interaction of I (R = C2H5) with phenylhydrazine afforded a mixture of the ethyl ester of the phenylosazone of mesoxalaldehyde acid XVII and ethyl 3‐(ethylthio)indole‐2‐carboxylate XVIII.
Synthesis of alkyl‐substituted 3‐phenyl‐4‐hydroxycoumarins
Authors: van Zanten B. , Nauta W. Th. 
Published: September 2010

AbstractAs part of a series of investigations into the relationship between chemical structure and biological activityB. van Zanten, Thesis, Vrije Universiteit, Amsterdam, 1960.
, a number of 3‐phenyl‐4‐hydroxycoumarins with alkylsubstituents in the 3‐phenyl group were synthesized.
N.M.R. spectra of some derivatives of nitrocyclopropane
Authors: Smidt J. , de Boer Th. J. 
Published: September 2010

AbstractAs part of the investigation of the structure of “trismethylene‐trinitrobenzene” VIa, N.M.R. spectra are recorded of a number of its degradation products, viz. the dicarboxylic acid Ia, anhydride IIa, trans‐nitrocyclopropane carboxylic acid III, the corresponding cis isomer IV and the lactone Va. The spectra are in accordance with the presence of cyclopropyl groups in all these compounds; alternative olefinic structures can definitely be excluded. Furthermore some information is obtained from the spectrum of “trismethylene‐trinitrobenzene”, supporting structure VIa and excluding VIb.The protons of the cyclopropyl rings of compounds Ia and IIa are easily recognised as belonging to the AB2 and ABX classes, respectively. For these two compounds the chemical shift and the spin‐spin coupling constant have been calculated.
The effect of surface‐active substances on a miscibility gap: The miscibility gap in the system water‐phenol‐cetyltrimethylammonium bromide (CETAB)
Authors: Prins A. 
Published: September 2010

AbstractThe miscibility gap was determined by measuring the cloud point of a number of water‐phenol‐CETAB mixtures.The position of the tie‐lines was established at 20°, 40° and 48°, by analysing the coexisting phases.
The determination of the electric dipole moments of some derivatives of tetraphenylethene and tetraphenylbutatriene
Authors: BÖttcher C. J. F. , Altona C. , van Woerden H. F. 
Published: September 2010

AbstractThe experimental determination of the dipole moments of some derivatives of tetraphenylethene and tetraphenylbutatriene is described. The agreement between the experimental and theoretical values is demonstrated.
Studies on vitamin D and related compounds XV: Irradiations at low temperatures
Authors: de Kock R. J. , van der Kuip G. , Verloop A. , Havinga E. 
Published: September 2010

AbstractIrradiation of ergosterol, lumisterol, tachysterol or previtamin D at room temperature for a long time brings about a considerable lowering of the extinction in the region 220‐300 mμ, whereas this phenomenon is not observed on irradiation of these compounds at 80°K in solid solution. From this it may be deduced that in the course of the photochemical reaction at room temperature ‐ besides the well‐known isomerisations – di‐ or poly‐merisations take place. A solution of tachysterol in liquid propane also shows the lowering of the extinction on irradiation. This indicates that the high viscosity of the medium rather than the low temperature is responsible for the non‐occurrence of lowering of the extinction in solid solution at 80°K.It is found that the photochemical cis/trans isomerisation of previtamin D into tachysterol is not ‐ or only partially ‐ inhibited by lowering the temperature to 80°K either in solid or in liquid solution. The conversion of tachysterol into previtamin D, on the other hand, did not occur on irradiation in liquid propane solution at 80° K. This is in agreement with theoretical considerations which were recently worked out in this laboratory for the mechanism of the cis/trans isomerisation in the case of stilbene. These studies lead to the assumption that for the conversion of the photo‐excited trans‐isomer (in the singlet state) thermal energy is required to provide the (rather small) energy of activation. The excited cis‐form may isomerise into the trans‐form without the help of thermal activation.
The autoxidation of isopropylbenzenes to benzoic acids in acid media: I. The oxidation of the intermediate acetophenones
Authors: van Helden R. , Kooyman E. C. 
Published: September 2010

AbstractA detailed picture is given of the mechanisms involved in the oxidation of acetophenones with oxygen to benzoic acids, at 150°, using manganese salts as catalysts and butyric acid as solvent.Kinetic studies indicate that the reaction is first‐order with respect to ketone and butyric acid, except at very high acid concentrations, and independent of the manganese concentrations as long as these exceed 0.008 M.The results are most satisfactorily described by a mechanism involving enolization of the ketone as the rate‐determining step. The enol is then assumed to be oxidized by Mn+++ to form the phenacyl radical, which adds on oxygen to form the phenacyl peroxy radical. This in turn readily reoxidizes Mn++ to Mn+++; the phenacyl peroxy anion rearranges to form formaldehyde and the benzoate anion.Supporting evidence for this postulated scheme has been obtained from a study of some electron transfer reactions of side‐chain‐substituted acetophenones and of other compounds with manganic ions.When cobalt ions instead of manganese ions are used as the catalyst, the reaction becomes much slower and is first order in cobalt ion. The cause to which this difference is attributed is that now the re‐oxidation of cobaltous ion by the phenacyl peroxy radicals becomes rate‐determining, the oxidation potential of the cobalt ions being appreciably higher than that of the manganese ions.Electron‐withdrawing nuclear substituents were found to have a retarding effect, whereas electron‐supplying substituents had an accelerating effect, probably on account of their influence on enol formation.
Sulphonation of benzene with sulphur trioxide in the gas‐phase
Authors: Heertjes P. M. , van Beek H. C. A. , Grimmon G. I. 
Published: September 2010

AbstractThe reaction of gaseous sulphur trioxide with gaseous benzene has been studied at three different temperatures with different ratios of the reactants. The reactions are rapid. The number of products can be rather large and depends on the ratio of sulphur trioxide to benzene.At low ratios (up to 1.2) diphenylsulphone, benzene‐monosulphonic acid and benzene pyrosulphonic acid are formed, at higher ratios also more highly sulphonated products are obtained.The amount of sulphonic acid groups increases proportionally to this ratio. It is concluded that diphenylsulphone is formed via the intermediate product, benzenepyrosulphonic acid, because the presence of acetic acid reduced the amount of sulphone proportionally. The temperature – between 100 and 230° ‐ had no marked influence on the results.
Electron spin resonance studies on ziegler catalyst systems: Part I. The system titanium tetrachloride‐aluminium diethyl chloride
Authors: Adema E. H. , Bartelink H. J. M. , Smidt J. 
Published: September 2010

AbstractElectron spin resonance was measured at room temperature in a mixture of TiCl4 and Al(C2H5)2Cl in heptane. No resonance could be demonstrated in the precipitate. At room temperature the concentration of unpaired electrons reaches its maximum value in approx. 10 minutes. At an Al/Ti ratio less than one the concentration of unpaired electrons remains for some hours at a constant value of about 4.6 × 10−3 times the initial concentration of aluminium compound, a value which is only slightly dependent on the initial titanium concentration.At higher temperatures or at an Al/Ti ratio greater than one the number of unpaired electrons also reaches a maximum, but decreases afterwards.The concentration of unpaired electrons appeared to be highly governed both by the TiCl3 precipitate formed and by other substances, such as water, alcohol, carbon tetrabromide and oxygen.
Chemistry of acetylenic ethers. L. Di(alk‐1‐ynyl)sulphides
Authors: Brandsma L. , Arens J. F. 
Published: September 2010

AbstractDi(but‐1‐ynyl)sulphide (IV, R = C2H5) and di(prop‐1‐ynyl)sulphide (IV, R = CH3) have been prepared as outlined in the reaction scheme.
Aromatic sulphonation III: Sulphonation of benzenesulphonic acid and m‐toluenesulphonic acid in fuming sulphuric acid
Authors: Cerfontain H. 
Published: September 2010

AbstractThe kinetics of the sulphonation of benzenesulphonic acid and m‐toluenesulphonic acid have been measured in oleum, containing 0.7 to 43.6% of sulphur trioxide The composition of oleum solutions is expressed in the percentage by weight of sulphur trioxide, present in excess of the composition H2SO4. The term concentration will be used for the different species present in oleum Solutions only.
at 25°. The reaction is first order with respect to the sulphonic acid. The kinetics are shown to be consistent with the sulphonation mechanism proposed by Brand 1, in which the reaction proceeds by a stepwise attachment of SO3 and H+ to the substrate, followed by the loss of a proton from the benzene ring.Sulphonation of the protonated sulphonic acid cannot be ruled out. Its contribution to the total rate of sulphonation is regarded as small in view of its electrophilic nature.
Reserpine analogues: I. β‐Indolylethylamine derivatives
Authors: Kralt T. , Asma W. J. , Haeck H. H. , Moed H. D. 
Published: September 2010

AbstractThe synthesis of a series of compounds resembling in some respects the alkaloid reserpine is described. The compounds are β‐indolylethylamine (tryptamine) derivatives.
Precipitate impregnated membranes: II. On the permeability of the BaSO4 membrane
Authors: Hirsch‐Ayalon P. 
Published: September 2010

AbstractThe effective BaSO4 membrane hinders the passage of Ba++ and SO4−− ions, but does not become impervious by precipitation of BaSO4. It remains permeable to other ions and to water.Characteristic for this type of membranes is their self‐regeneration mechanism, which repairs disturbances in the formation and adjustment of the membrane due to microscopic causes.An attempt is made at a mechanical explanation of the permeation of electrolytes through the effective BaSO4 membrane: assumption of the movement of small amounts of solution through randomly arising and again disappearing openings in the effective precipitate layer within the membrane, however, proves to be untenable.The permeability of the effective BaSO4 membrane is selective and is obviously electrochemical in character.
Glucosides of 1‐hydroxyanthraquinone 3‐carboxylic acid and 3‐hydroxy‐1‐methylanthraquinone
Authors: Bellaart A. C. , Koningsberger C. 
Published: September 2010

AbstractA synthesis of 1‐glucosido‐anthraquinone 3‐carboxylic acid and of 3‐glucosido‐1‐methylanthraquinone is described.
Untersuchungen über Derivate von 2,3‐Dihydropyran‐2,4‐Dion: (3. Mitteilung)
Authors: Salemink C. A. 
Published: September 2010

AbstractDie vorliegende Arbeit behandelt die Darstellung von einigen bisher unbekannten höheren Homologen von Dehydracetcarbonsäure. Die antibakterielle Wirkung dieser und der schon bekannten Verbindungen wurde bei Staphylococcus aureus, Mycobacterium phlei und Escherichia coli untersucht und verglichen mit jener von Dehydracetsäure und ihren Homologen.
The halogenation of aromatics: Part V. Gas‐phase chlorination of phenoxybenzene
Authors: Engelsma J. W. , Kooyman E. C. 
Published: September 2010

AbstractThe gas‐phase chlorination of phenoxybenzene was studied at 300‐500°, using the experimental methods described earlier. The results obtained are in contrast with those found in liquid‐phase chlorination: there the product was mainly para‐chlorophenoxybenzene, while in the present investigation, at temperatures above 350°, monochlorinated products were mainly the meta‐isomer; they did not contain any ortho‐compound. Instead, dibenzofuran was formed.Between 300 and 350°, appreciable proportions of para‐chlorophenoxybenzene were also formed, presumably owing to the occurrence of electrophilic substitution in the liquid‐phase afterchlorination or at the walls of the reactor.The high‐temperature halogenation of phenoxybenzene therefore leads to substitution at the carbon atom carrying the highest positive charge, i.e. the position corresponding to the highest Hammett σ‐value, in the same way as in our earlier gas‐phase halogenations of halobenzenes and of benzonitrile.
Distribution of radioactivity in recoil‐labelled toluene‐14C
Authors: Visser R. , Redvanly C. R. , Sixma F. L. J. , Wolf A. P. 
Published: September 2010

AbstractToluene‐14C1 produced by the thermal neutron irradiation of a mixture of benzene and 2‐methylpyrazine is not specifically labelled in the methyl group, ruling out simple hydrogen replacement in benzene by the recoiling carbon‐14 for at least some fraction of the radioactive toluene produced. Using a recently published degradation scheme, the distribution of radioactivity in the ring relative to the methyl group has now also been determined.
Contact angles; wetting and de‐wetting of mercury: Part I. A critical examination of surface tension measurement by the sessile drop method
Authors: Smolders C. A. , Duyvis E. M. 
Published: September 2010

AbstractA survey is given of the existing methods for measuring the surface tension from the geometry of sessile drops. These methods, which generally consist of the measurement of simple drop dimensions, are insufficiently accurate for use with adsorption studies.A new procedure is described to find the surface tension by means of a graphical evaluation of the drop shape factor β (the constant shape factor as defined in Bashforth and Adam's treatment of the sessile drop). In this way the accuracy is considerably increased (0.1% uncertainty in γ).The interfacial tension of the system mercury/0.05 M Na2SO4 at −0.460 V vs. saturated calomel electrode, and at 25°, is found to be 426.2 ± 0.2 dynes/cm, which agrees well with the literature.
The V‐T‐x space model of the ethylene‐naphthalene system, I
Authors: van Welie G. S. A. , Diepen G. A. M. 
Published: September 2010

AbstractV‐T measurements carried out on the ethylene‐naphthalene system at constant composition are described. The measurements also provide data on the saturation volumes of solutions of naphthalene in supercritical ethylene.
Chemistry of acetylenic ethers LII acetylenic tert. Butyl ethers and some other acetylenic ethers with branched alkyl groups: Some remarks concerning the preparation and the pyrolysis of acetylenic ethers
Authors: van Daalen J. J. , Kraak A. , Arens J. F. 
Published: September 2010

AbstractTert. butoxyethyne IV and some 1‐tert.butoxy‐1‐alkynes V have been prepared as outlined in the scheme below. The elimination of HBr from 2‐bromo‐1,2‐unsaturated ethers such as III and VI by means of sodium amide in liquid ammonia gives much better yields of acetylenic ethers than the procedure using KOH. Some examples of this modification of a much used method for the preparation of acetylenic ethers are given. In the case of propynyl ethers CH3C≡COR an excess of sodamide must be avoided, because this isomerizes the propynyl ethers into propargyl ethers HC≡CCH2OR.Tert.butoxyalkynes V split off isobutene at 70–80°, forming cyclobutenone ethers X.The thermal stability of 1‐alkoxy‐1‐alkynes decreases in the order C2H5O > i.C3H7O > t.C4H9O.
On the cobalt‐catalyzed decomposition of tert.‐butyl hydroperoxide in the presence of some five‐membered heterocycles
Authors: Bigot J. A. 
Published: September 2010

AbstractThe cobalt‐catalyzed decomposition of tert.‐butyl hydroperoxide in the presence of a number of five‐membered heterocycles is described. With tetrahydrofuran displacement of the alpha‐hydrogen atom by a peroxy group is observed; with furan and pyrrole 1.4 addition of peroxy radicals takes place. Thiophen does not react under the conditions used.
Studies in transition metal chemistry. Part II: The addition of organic halides to bis‐cyclopentadienyl vanadium(II)
Authors: de Liefde Meijer H. J. , Janssen M. J. , van der Kerk G. J. M. 
Published: September 2010

AbstractSeveral organic halides were found to add to Cp2V(II). The reactions of benzyl chloride, ethyl bromide and methyl iodide were studied in detail. Instead of the expected compound Cp2V(IV)RX (X = Cl, Br, I) the tervalent halide Cp2V(III)X was formed exclusively in the presence of excess alkyl halide. When excess Cp2V(II) was present, however, both Cp2V(III)X and Cp2V(III)R were found as reaction products. The following reaction equations are proposed: a) Cp2V + RX → [Cp2VRX]; b) [Cp2VRX] + Cp2V → Cp2VR + Cp2VX; c) Cp2VR + + RX (excess) → Cp2VX + R2. The compounds Cp2V(III)R and Cp2V(III)X were synthesized and the occurrence of reaction c) was demonstrated.
Investigations in the vitamin A‐Series: IV. Some cases of abnormal decarboxylation
Authors: Smit A. 
Published: September 2010

AbstractDecarboxylation of a number of α‐carboxy‐α,β‐unsaturated nitriles leads to β,γ‐unsaturated nitriles. These products smoothly rearrange into the normal α,β‐unsaturated nitriles.
Influence de la Configuration sur L'absorption dans L'infrarouge des Doubles Liaisons Dans des Stéroides
Authors: Barker J. , van den Bogaert H. M. 
Published: September 2010

AbstractComparison of steroids, containing a 4,6‐dien‐3‐one system, shows that the difference between the two frequencies of the unsaturated system in compounds with a retro‐configuration is greater than that in compounds with a natural one.