bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of U.V.‐light on some components of the nucleic acids. IV. The influence of oxygen on the extent of the first irreversible reaction, shown by uracil and orotic acid
Authors: Beukers R. , Ijlstra J. , Berends W.
Published: September 2010

The percentage of orotic acid, sensitive to ultraviolet light, has been found to depend on the concentration of oxygen in solution. Diminishing this concentration by bubbling through nitrogen or hydrogen, the sensitivity increases from 14 % to 37 %. Saturation of the solution with oxygen leads to protection (instead of 14 % an irreversible loss of 7%). One of the reactions, shown by uracil on irradiation (“the first irreversible reaction”) also exhibits this relationship. The possibility of an intermediate triplet state is proposed.
Square wave electrolysis. I. The cyclic potential‐step method
Authors: Smit W. M. , Wijnen M. D.
Published: September 2010

Drawbacks of the well‐known potential‐step method are briefly mentioned. A new method called the cyclic potential‐step method is introduced, the essential of which is that a square wave voltage is applied to a polarisable electrode. It is shown mathematically that the current response approaches rapidly to a constant pattern. The derivations presented are free from restrictions concerning the reversibility of the system and the magnitude of the amplitude of the square wave.

It is shown that the cyclic potential‐step method offers easy means for the determination of the transfer‐coefficient (α) and the standard exchange current density (j00).
Synthesis of isocoumarin‐3‐carboxylic acids
Authors: Ribbens C. , van der Stelt C. , Nauta W. Th.
Published: September 2010

2‐Carboxyphenylpyruvic acid and its derivatives with substituents in the phenyl nucleus can be prepared via a modified azlactone synthesis. These phenylpyruvic acids display a spontaneous ring closure into the corresponding isocoumarin carboxylic acids.
The effect of ultraviolet light on some components of the nucleic acids. VI The origin of the U.V. sensitivity of deoxyribonucleic acid
Authors: Beukers R. , Ijlstra J. , Berends W.
Published: September 2010

The rapid decrease in extinction of deoxyribonucleic acid in the first moments of irradiation with U.V. light (2537 Å) is due to the conversion of the pyrimidines into low‐absorbing substances. Thymine in this natural polymer reacts according to the so‐called “first irreversible reaction” shown by the free bases in solution. This could be demonstrated by means of a peculiar property of the irradiation product of thymine. Cytosine is supposed to react in the same way. The importance of this finding with respect to the lethal action of U.V. light on micro‐organisms is discussed.
Paper chromatography of derivatives of ethylenebis (dithiocarbamic acid)
Authors: Thorn G. D. , Ludwig R. A.
Published: September 2010

Disodium ethylenebisdithiocarbamate and its products of oxidation by air (ethylenethiuram monosulphide, ethylenethiourea and sulphur) have been separated by ascending paper chromatographic techniques. Several commercial preparations derived from the dithiocarbamate have been analyzed for the presence of these oxidation products.
Studies on vitamin D and related compounds X. Preparation and properties of cis‐isotachysterol2
Authors: Verloop A. , Corts G. J. B. , Havinga E.
Published: September 2010

The photochemical conversion of isotachysterol2 (in ether) has been studied; the effects of wave‐length and time of irradiation on the composition of the irradiation mixture are discussed. On chromatography of the crude irradiation product a compound was obtained in a pure, non‐crystalline form. The compound did not show antirachitic activity. The ultra‐violet and infra‐red absorption spectra, the iodine‐catalysed quantitative conversion to isotachysterol2, the behaviour on heating in solution and the very low reactivity towards maleic anhydride led to the conclusion that the compound is the Δ6,7‐cis isomer of isotachysterol2, i.e. 9,10‐secoergosta‐5(10),6‐cis, 8(14), 22‐tetraen‐3β‐ol.
Über Verwendungsmöglichkeiten von 2‐chlor‐3,5‐dinitropyridin bei Untersuchungen über Eiweissabbau und Aminosäuren
Authors: Talik Zofia , Plaźek Edwin
Published: September 2010

Es wurde festgestellt, dass das 2‐Chlor‐3,5‐dinitropyridin äusserst leicht kristallinische Derivate mit den wichtigsten aliphatischen Aminosäuren gibt. Auch mit einigen Polypeptiden und Eiweisstoffen wurden unlösliche gelbe Kondensationsprodukte erhalten.

Es wird darauf hingewiesen, dass das 2‐Chlor‐3,5‐dinitropyridin vollwertig das Fluor‐2,4‐dinitrobenzen bei Eiweissuntersuchungen zu ersetzen vermag, und dabei manche Vorteile bietet.
Telomerization and prins reaction of styrene and formaldehyde in acetic acid. The role of cyclic formal in the reaction mechanism
Authors: Heslinga A.
Published: September 2010

The effect of variations in the reaction conditions on the composition of the end product was studied in the reaction of styrene with formaldehyde in acetic acid. Initially a relatively large amount of 4‐phenyl‐1,3‐dioxan is formed along with telomer homologues. This cyclic formal is cleaved by protolysis in a comparatively slow secondary reaction with styrene; it thus acts as an intermediate formaldehyde donor.

The results are interpreted in terms of a carbonium‐ion mechanism.
On toxoflavin, the yellow poison of pseudomonas cocovenenans
Authors: van Damme P. A. , Johannes A. G. , Cox H. C. , Berends W.
Published: September 2010

About 1933 a bacterium, now called Pseudomonas cocovenenans, was discovered by van Veen et al. as being responsible for the well known bongkrek‐poisonings in Java. Two toxic principles are produced by this microorganism. One of these is identical with the yellow pigment of this bacterium. The isolation of this substance, toxoflavin, was worked out and the elucidation of its structure was described. However, in our opinion the conclusions as to the structure were very improbable and for this reason we started a new investigation of this problem. The result of this work, leading to an entirely different structure, is described. Simultaneously the isolation of toxoflavin has been simplified.
The standard potential of the silver bromide‐silver electrode in anhydrous methanol at 25°
Authors: de Ligny C. L. , Wieneke A. A.
Published: September 2010

In the determination of pH values of standard buffer solutions in anhydrous methanol by the method of the National Bureau of Standards, it appeared that the pH values found by using a cell with a silver chloride electrode differed from the pH values found by using a cell with a silver bromide electrode. The assumption that this difference was caused by the use of an incorrect literature value for the standard potential of the silver bromide electrode, was checked by an experimental determination of this potential, viz. by determining the difference between the standard potential of the silver chloride electrode (which is supposed to be correct) and the silver bromide electrode.

The new value found for the standard potential of the silver bromide electrode in anhydrous methanol is ‐0.1375 volt against the normal hydrogen electrode.
Infrared spectra of some methacrylic esters and their polymers
Authors: Salomon G. , Schooneveldt‐van der Kloes C. J. , Zwiers J. H. L.
Published: September 2010

Spectra of 10 monomers and polymers of methacrylate esters and of methyl chloroacrylate have been studied between 6000‐450 cm−1.

A number of known regularities are confirmed. The CH2 and CH3 deformation vibrations in the 1500‐1350 cm−1 region of the polymer unit can be distinguished from absorptions due to the substituents. Some absorptions typical for the substituents have been confirmed between 800‐450 cm−1.

Absorptions due to deformation and stretching vibrations of the =CH2 group are readily determined in the corresponding first overtone region. An application of quantitative monomer estimation in the near infrared is reported.
The chemistry of the N‐alkylaldimines. I. The reaction of N‐alkylaldimines with acetic anhydride
Authors: Breederveld H.
Published: September 2010

N‐Alkylaldimines add on acetic anhydride with the formation of the corresponding N‐alkyl‐N(1‐acetoxyalkyl)‐acetamides, which readily split off acetic acid to yield N‐alkyl‐N(1‐alkenyl)‐acetamides as the final products.

N‐Propyl‐N‐vinyl‐, N‐propyl‐N(1‐propenyl)‐ and N‐propyl‐N(1‐butenyl)‐acetamide have been prepared by this method; the infrared spectra are discussed.
The structural proof of trismethylene‐trinitrobenzene: Nucleophilic aromatic addition III
Authors: de Boer Th. J. , van Velzen J. C.
Published: September 2010

“Trismethylene‐trinitrobenzene” has structure IV and not VI (chart 1) as shown by ozonolysis, yielding an aldehydic acid VIII, a dicarboxylic acid IX and, on decarboxylation, a monocarboxylic acid X (chart 2). Ozonolysis in methanol leads to products which are consistent with the mechanism put forward by Criegee (chart 3). Oxidation of “trismethylene‐trinitrobenzene” with chromium trioxide results in a ketone XVIII, which can be cleaved by alkali into a carboxylic acid XIX (chart 4), the structure of which is again explicable only with structure IV for the parent compound.
Physical properties of organic thiones. Part I. Electronic absorption spectra of nitrogen‐containing thione compounds
Authors: Janssen M. J.
Published: September 2010

The electronic absorption spectra of some thioamides, dithiocarbamic esters, thioureas and one thioncarbamic ester are recorded in a hydrocarbon, diethyl ether, ethanol and concentrated sulphuric acid as solvents. The bands are classified according to their intensities and solvent effects. It is shown that the assignment of Koch must be reversed. The spectra of substituted thioureas are discussed in relation to their spatial structures.
Über Muscaridin. II
Authors: Salemink C. A. , Schuller P. L. , Demel R. A.
Published: September 2010

A recent investigation of Kögl, Salemink and Schuller established the constitution of muscaridin as the quaternary trimethylammonium salt of 6‐amino‐2,3‐dihydroxyhexane.

The present communication gives a preliminary description of a synthesis which started from 2,3‐dihydropyran, leading to racemic muscaridin. The synthetic product gives the same RF‐value and a fully similar infrared spectrum as the natural base.
Electrochemical methods of ultramicroanalysis
Authors: Alimarin I. P. , Petrikova M. N.
Published: September 2010

For a long time the attention of many analytical chemists in various countries has been attracted by the problem of studying the composition of small amounts of matter.

The development of this interesting and practically important field of analytical chemistry is much indebted to the investigations, carried out by a number of outstanding chemists of our time.Emich, Pregl, Hechtin Austria, and the Russian analystsKorenman, Komarovsky, Tananaev, Malyarovand others, might be mentioned in this connection. The development of microchemistry owes much tovan Nieuwenburg, who, as long ago as 1937, wrote, that microanalysis, as he was firmly convinced, might be and would be the chemical analysis of the future

C. J. van Nieuwenburg, Mikrochemie21, 184 (1937).

. A great propagandist of microchemistry

Idem., Bull. soc. chim. France No. 11–12, c.63 (1953).

Idem., Chim. Anal.38, (12), 423 (1956).

Idem., Analyst81, 450 (1956).

he considered the future development of micromethods and mentioned ultramicroanalysis.

In this paper a short description of some of our investigations on electrochemical methods of ultramicroanalysis is given.
Dosage du Plomb dans les Alliages Techniques. Précipitation à l'état de PbSO4 dans les solutions homogènes
Authors: Burriel‐Marti F. , Gárate M. T.
Published: September 2010

On précipite le plomb à l'état de PbSO4, dans les solutions provenant de l'attaque du plomb pur par HNO3 et de ses alliages par un mélange des acides nitrique et fluorhydrique dilués.' La précipitation est effectuée, en presence d'alcool éthylique, par l'acide sulfamique comme générateur de l'ion sulfate.
The microchemistry of the platinum metals. Separation and determination of micro amounts of rhutenium, rhodium and palladium
Authors: Jasim Fadhil , Magee Robert J. , Wilson Cecil L.
Published: September 2010

A method is outlined for the separation and determination of small amounts of ruthenium, rhodium and palladium individually as well as in combinations of two or even all three elements mentioned. It is based principally upon reactions of these elements with 8‐hydroxyquinoline. Determinations are carried out spectrophotometrically on the metal oxinate extract in chloroform. The procedure gives reproducible results and provides a. rapid method for the determination of each of the three elements even in their mixtures.
Polarography of copper (II) thiocyanate solutions
Authors: Kolthoff I. M. , Okinaka Y.
Published: September 2010

Conflicting interpretations are found in the literature of polarograms of copper (II) in thiocyanate solutions. In the present study it is shown that the polarograms change with concentration of thiocyanate and time of aging of the solutions when the thiocyanate concentration is greater than about 0.1 M. A wave appearing at the most negative potential (half‐wave potential −1.5 V vs. SCE), which is attributed in the literature to the reduction of copper (I) to copper metal or to a catalytic reaction, is actually due to the reduction of hydrogen ions produced as a result of reduction of copper (II) by thiocyanate ions.
Etude Analytique des Acides Sébacique Et Tétrachlorophtalique en Vue du Dosage du Thorium
Authors: Wenger Paul E. , Kapétanidis I.
Published: September 2010

Au cours du prèsent travail, nous avons établi les constantes de dissociation thermodynamiques des acides sébacique (pk1 = 4,40, pk2 = 5,22) et tétrachlorophtalique (pk1 = fort, pk2 = 2,94). De même, nous avons déterminé les solubilités des sébacates et des tétrachlorophtalates du thorium et des terres cériques, ce qui nous a permis de calculer les produits de solubilité théoriques correspondants.
Some quantitative remarks on extraction equilibria IV
Authors: Oosting M.
Published: September 2010

Two equations are derived, which predict the course of solvent extraction in the presence of complexing ions or when an insoluble compound can be formed. The correctness of the equations is proved for a few extraction systems.
Metabolism and functions of phosphatides: The preparation of a series of L‐α‐lecithins
Authors: Kögl F. , de Haas G. H. , van Deenen L. L. M.
Published: September 2010

Ten L‐α‐lecithins have been prepared by acylation of L‐α‐glyceryl‐phosphorylcholine. Solubilities, RF‐values and other physical data are reported of L‐α‐[diacetyl]‐lecithin, L‐α‐[dibutyryl]‐lecithin, L‐α‐[diheptanoyl]‐lecithin, L‐α‐[didecanoyl]‐lecithin, L‐α‐[di‐10‐methyl‐undecanoyl]‐lecithin, L‐α‐[dipentadecanoyl]‐lecithin, L‐α‐[dioctadecanoyl]‐lecithin, L‐α‐[di‐undecenoyl]‐lecithin and L‐α‐[dioctadecenoyl]‐lecithin.
A simple preparation of phthaloyl amino acids via a mild phthaloylation
Authors: Nefkens G. H. L. , Tesser G. I. , Nivard R. J. F.
Published: September 2010

Phthaloyl amino acids can be synthesized from N‐carboethoxy phthalimide and amino acid salts under very mild conditions in water. The preparation of 11 of these phthaloyl derivatives is described, some of which are new. Up to the present the method has only failed with tryptophane. Retention of the optical configuration during the reaction is shown.
The dissociation constants of some aliphatic amines in water and methanol‐water mixtures at 25°
Authors: de Ligny C. L.
Published: September 2010

The dissociation constants of some primary aliphatic amines were measured in water and in methanol‐water mixtures at 25°. These dissociation constants (K* = a*Ha*B/a*HB ) show a maximum at 60‐80% methanol. This maximum is ascribed to the unequal influence of the methanol content of the solvent on γ0,H and γ0,HB.
Acid anilides: VII. Quantitative analysis of fatty acids by paper chromatography of their anilides
Authors: de Jonge A. P. , Verhage A.
Published: September 2010

This report deals with the results of a detailed investigation into the accuracy of a quantitative analysis of mixtures of lower fatty acids (C2‐C12) by means of paper chromatography.

To this end, mixtures of 2, 3, 4 or 5 fatty acids were weighed‐in, and by means of the methods described in previous reports, converted into the anilides and subjected to paper chromatography. From the results the compositions of the fatty acid mixtures were calculated and compared with the actual compositions. The differences were statistically evaluated to a mean deviation and a standard deviation. The values clearly demonstrate the reliability of the method. The recovery of the fatty acids was 81‐88%.

The values obtained do not differ appreciably from these obtained in the analysis of pure anilides (the latter investigation had a more limited scope). It may, therefore, be concluded that the limitations of the method are connected with the paper chromatography.

No indications have been obtained that the analytical data are dependent on the percentage or on the Rf‐value.
Synthesis of ortho‐substituted benzophenones by way of benzophenones carrying A t‐butyl group as a blocking group
Authors: Hofman P. S. , Reiding D. J. , Nauta W. Th.
Published: September 2010

Whereas benzoylation of toluene or m‐xylene is known to lead to a mixture of 2‐ and 4‐methylbenzophenone and to 2,4‐dimethylbenzophenone respectively, the presence of a blocking t.butyl group in the 4‐ and the 5‐positions respectively leads to products which on debutylation yield benzophenones with substituents in the ortho position only.
Investigations on sterols. XVI: The syntheses and properties of 9β,10α‐androstanes
Authors: Westerhof P. , Reerink E. H.
Published: September 2010

In this paper are described the syntheses and properties of 9β,10α‐testosterone and some derivatives thereof.
The reaction of phenol with formaldehyde. III. selective hydroxymethylation of phenols at the ortho‐position
Authors: Peer H. G.
Published: September 2010

The 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

Cis 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

The 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

Data 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

The 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

It 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

The 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

As part of a series of investigations into the relationship between chemical structure and biological activity

B. 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

As 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

The 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

The 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

Irradiation 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

A 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

The 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

Electron 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 XLIX: Vinylthioethyne and some of its derivatives
Authors: Brandsma L. , Arens J. F.
Published: September 2010

Vinylthioethyne IV and its derivatives VI (R = CH3 or n.C4H9) and VII have been prepared as outlined in the reaction schemes.
Chemistry of acetylenic ethers. L. Di(alk‐1‐ynyl)sulphides
Authors: Brandsma L. , Arens J. F.
Published: September 2010

Di(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

The 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

The 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

The 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

A 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

Die 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

The 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

Toluene‐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

A 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

V‐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

Tert. 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

The 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

Several 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

Decarboxylation 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

Comparison 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.
Synthesis and physiological properties of some heterocyclic‐aromatic sulphides and sulphones. I. Synthesis of some aryl‐pyridyl sulphides
Authors: van Zwieten P. A. , van Velthuijsen J. A. , Huisman H. O.
Published: September 2010

The preparation of some aryl‐pyridyl sulphides with potential acaricidal properties is described. In the compounds synthesized the benzene nucleus is substituted with a para‐chlorine atom or with three chlorine atoms in positions 2, 4 and 5. Position 5 in the pyridine nucleus is either unsubstituted or carries a chlorine substituent. From a few aryl‐pyridyl sulphides the corresponding N‐oxides have been prepared.
A polarographic study of the oxidation of some polyhydroxybenzenes with atmospheric oxygen: (Preliminary communication)
Authors: van Dijk H. , Ter Haar H. E.
Published: September 2010

As a contribution to the study of the formation of humic acids in soil, a polarographic investigation has been made of the oxidation of some poly‐hydroxybenzenes in aqueous solution under different conditions. The formation of hydroxyquinone as an intermediate in the oxidation of hydroquinone was confirmed. Indications were obtained for the identity of some other intermediate reaction products. The important conclusion is drawn that the presence of tyrosinase or certain clay‐minerals frequently not only influences the reaction velocity, as is sometimes supposed, but also may alter the course of the oxidation reaction.
Use of carbonylditriazole in peptide synthesis
Authors: Beyerman H. C. , van Den Brink W. Maassen
Published: September 2010

N,N′‐Carbonyldi‐s‐triazole is shown to be a useful peptide‐forming reagent. Advantages over other reagents are: (1) low degree of racemization, (2) applicability in dimethylformamide, a solvent for both small and large peptides.
Thermodynamic properties of transition metal compounds and coordination complexes: I. The heats of hydration of divalent cations in the series Ca2+ ‐ Zn2+
Authors: Schuit G. C. A.
Published: September 2010

According to the ligand‐field theory the heat of hydration of a transition‐metal ion is the sum of an electrostatic interaction and a ligand‐field stabilization.

An estimate of the latter can be deduced from the spectroscopic Δ‐value. If the experimental heats are corrected for the ligand‐field effects, a steady rise for the residual heats is observed going from Ti2+ to Zn2+ which is considered an argument for the validity of the theory.

However, in the m.o. approximation the metal d‐electrons are either in the t2g state (non‐bonding in the absence of π‐interaction) or in the antibonding eg state. Hence formally the transition‐metal hydrates can be considered as destabilized with respect to a hypothetical standard state which can be calculated, by making suitable corrections, with help of the spectroscopic Δ‐values. It is shown here that the values so obtained are numerically equal to those given by an empirical equation for cations with the inert gas configuration

— (ΔHn) = I + constant

(I is the ionization energy for the formation of divalent cations).
Chemistry of acetylenic ethers. LV: Di(alk‐1‐enyl)ethers, ‐thioethers, and ‐selenoethers
Authors: Brandsma L. , Arens J. F.
Published: September 2010

The compounds mentioned in the title are obtained conveniently from aldehydes as outlined in the reaction schemes on this and on the following page.
Studies in IVth group organometallic chemistry VIII: Synthesis of linear organotin polymers from organotin dihydrides and acetylenic compounds
Authors: Noltes J. G. , van der Kerk G. J. M.
Published: September 2010

Linear organotin polymers with molecular weights (Mw)in the range of 45 000 to 100 000 have been obtained by poly‐addition reactions involving organotin dihydrides and α,ω‐diynes, such as 1,5‐hexadiyne, 1,8‐nonadiyne, and 1,4‐diethynylbenzene. A number of 1‐stanna‐2,6‐cycloheptadiene derivatives (cyclic monomers derived from 1,5‐hexadiyne) have been isolated.
The chemistry of propadiene: Some investigations on the addition of Br2, BrCl, and Cl2
Authors: Peer H. G.
Published: September 2010

The reaction of propadiene with Br2, BrCl, and Cl2 is studied in various solvents and at different temperatures. It is shown that only partial addition takes place, and further that the initial attack of the Hal+ ion takes place at the central C atom. The findings are interpreted as the result of the formation of the intermediary carbonium ion, stabilized by resonance: magnified image.

In the reaction with Cl2, propargyl chloride is formed besides 2,3‐dichloro‐propene. The way in which the former product is formed, is discussed.
Heterocyclic compounds IV: Synthesis and reactions of some 2,3‐pyrrolidinedione derivatives
Authors: Merchant J. R. , Srinivasan V.
Published: September 2010

A number of 2,3‐pyrrolidinediones have been synthesised by the condensation of oxalacetic and oxalpropionic esters with different aldehydes and ketones. Typical reactions and properties of the diones have been studied by the preparation of suitable derivatives.
Some new reaction products of divinylsulphone with primary amines
Authors: Bellaart A. C.
Published: September 2010

The preparation is described of some substituted 1,4‐thiazane‐1,1‐dioxides containing respectively propargyl, allyl, cyclohexyl, benzyl, octyl, dodecyl and cetyl groups in the 4‐position.

Also some quaternary compounds derived from the first four substances are described.
A convenient synthesis of 2,2‐disubstituted‐1‐cyclopentanones
Authors: Conley Robert T.
Published: September 2010

The synthesis of 2,2‐dimethyl‐ and 2,2‐diphenylcyclopentanone in high yield is reported by the ring expansion of the corresponding 1‐(disubstituted carbinol)‐1‐hydroxycyclobutane in polyphosphoric acid. Modifications of the general synthetic route using reported reactions offers a general route to 2,2‐disubstituted‐1‐cyclopentanones.
Di‐ and tri‐nitro derivatives of 1‐chloronaphthalene
Authors: Bassilios H. F. , Salem A. Y. , Shawky M.
Published: September 2010

Nitration of 1‐chloronaphthalene with excess of fuming nitric acid at a relatively high temperature provided a mixture of 1‐chloro‐4,5‐ and 1‐chloro‐4,8‐dinitronaphthalenes. The same dinitro derivatives can be obtained by further nitration of 1‐chloro‐4‐nitronaphthalene. The nitration of 1‐chloro‐4,5‐dinitronaphthalene with either fuming nitric acid or mixed acids provides the known 1‐chloro‐2,4,5‐trinitronaphthalene, while that of 1‐chloro‐4,8‐dinitronaphthalene with fuming nitric acid yields a new trinitro derivative melting with decomposition at 270° which is confirmed as being 1‐chloro‐4,5,8‐trinitronaphthalene.