bluuebunny/crossref_metadata_2025_split huggingface dataset:
The mull spectra of NaNO2, KNO2 and AgNO2
Authors: Ketelaar J. A. A. , Schutte C. J. H. 
Published: September 2010

AbstractThe paraffine oil mull spectra of NaNO2, KNO2 and AgNO2 are reported. The 836 cm−1 band in the spectrum of KNO2 is assigned to a vibration of the NO3− ion which always occurs as an impurity in KNO2. Evidence is presented for the occurrence of double decomposition during m ulling operations.
The thermal decarboxylation of alkali trichloroacetates in aprotic solvents. II. Decarboxylation in the presence of olefins
Authors: Wagner W. M. , Kloosterziel H. , van der Ven S. 
Published: September 2010

AbstractThe thermal decarboxylation of alkali trichloroacetates in aprotic solvents in the presence of olefins has been investigated. The isolation of dichlorocyclopropanes in good yields demonstrates the formation of CCl2 as an intermediate. By this method, the reaction of base‐sensitive acceptors such as allylchloride with CCl2 may be successfully accomplished, since it proceeds under essentially neutral conditions. Vinyl acetate gave, in addition to the cyclopropane derivative, 1‐trichloromethylethyl acetate.
A molecular compound of mandelic acid and ethyl mandelate
Authors: de Roos A. M. , Rekker R. F. , Ernsting M. J. E. , Nauta W. Th. 
Published: September 2010

AbstractFrom a quantity of ethyl mandelate there separated, after prolonged storage, a crystalline compound, which was found to consist of mandelic acid and ethyl mandelate in a 1 : 1 ratio. This product can also be prepared in situ by mixing equivalent amounts of mandelic acid and ethyl mandelate, the crystalline product separating with generation of heat. This phenomenon did not occur when some other mandelic esters were investigated.
Mechanism of reactions of unsaturated ethers and thioethers III: Acid catalyzed addition of water to ethynyl ethers
Authors: Stamhuis E. J. , Drenth W. 
Published: September 2010

AbstractThe kinetics of the addition of water to ethynyl ethers in aqueous solution were investigated:
equation image
The reaction is general acid catalyzed. This indicates, that a proton transfer is the rate determining step of the reaction:
equation image
The constitution of Tamarindus‐amyloid
Authors: Kooiman P. 
Published: September 2010

AbstractThe preparation of Tamarindus‐amyloid from seeds of Tamarindus indica L. is described in detail.The product was homogeneous under conditions of free boundary electrophoresis and of sedimentation in the ultracentrifuge. A tentative value for a molecular weight of 115,000 was found.Partial hydrolysis of the polysaccharide with Myrotheciwn‐cellulase liberated a hepta‐, an octa‐ and a nona‐saccharide, while a fungal enzyme “Luizym” yielded 6‐O‐α‐D‐xylopyranosyl‐D‐glucopyranose.Partial hydrolysis with dilute mineral acid gave the disaccharide 2‐O‐β‐D‐galactopyranosyl‐D‐xylopyranose.Experimental evidence is presented for the following structural features:
A main chain of β 1,4‐linked glucose residues.
A xylose residue attached by an α 1,6‐linkage to three glucose residues out of every four.
The three substituted glucose residues and the unsubstituted one alternate regularly.
The galactose residues are attached to the xylose residues by β 1,2‐linkages.
On the basis of this evidence a structure for Tamarindus‐amyloid is proposed.
Decomposition of organo‐titanium halides
Authors: de Vries Hn. 
Published: September 2010

AbstractPure tetravalent organo‐titanium halides and those titanium alkyls which are formed by a reaction of TiCl4 + organometallic compounds, are unstable and subject to bimolecular disproportionation into 2 TiCl3, an alkane and an olefin, provided an H‐atom on a β‐C‐atom is present in the alkyl group. On the other hand, tetravalent titanium‐alkyls lacking this H‐atom are relatively stable (e.g. TiCl3CH3 and neopentyl‐titanium‐trichloride).Chemical evidence has also been advanced in support of two other, subsidiary, bimolecular reactions of titanium alkyls in which, in a concerted reaction, the Ti‐C bonds are broken without previous atom migration taking place in the alkyl groups. In one of these subsidiary reactions the alkyl groups bonded to titanium get directly linked up, with formation of a saturated hydrocarbon and TiCl3. In the other, a titanium alkyl reacts with TiCl4 to give an alkylhalide and TiCl3.By performing the disproportionation reaction of TiCl3CD3 in heptane, or of titanium alkyls in deuterated cyclohexane, it is demonstrated that no reaction with aliphatic solvents occurs.
Preparation of diaryl sulphides
Authors: Uhlenbroek J. H. 
Published: September 2010

AbstractA new and simple method is described for the preparation of symmetrically and asymmetrically substituted diaryl sulphides from sodium thiophenolates and halogenated aromatics by heating in a suitable solvent, preferably dimethylformamide. Formation of poly‐substituted products may be suppressed by using an excess of the halogenated aromatic hydrocarbon.
Studies on vitamin D and related compounds. XVI: Synthesis of model compounds for the study of the previtamin D ⇋ vitamin D interconversion
Authors: Schlatmann J. L. M. A. , Havinga E. 
Published: September 2010

AbstractThe syntheses are described of previtamin D ‐ and vitamin D analogues to be used for the study of the thermal precalciferol ⇋ calciferol isomerization reaction.A previtamin D analogue (4) prepared as indicated by Inhoffen could not be obtained in a pure state. Closer inspection revealed that the final step, the selective partial hydrogenation of the triple bond of 3, yielded a mixture of isomers. Two calciferol analogues (15A and 15B) were synthesized, following routes used by Harrison and Lythgoe for obtaining related compounds. These vitamin D analogues showed the same remarkable smooth isomerization as the vitamin itself. With the analogues, however, the equilibrium was found to be displaced towards the “previtamin” side. This enabled us to obtain the corresponding previtamin D analogues by heating the acetates of the calciferol analogues (15) at 90°, followed by saponification and chromatographic purification.
Investigations in the vitamin A series V. Some aspects of dehydration of polyenic alcohols
Authors: van Leeuwen P. H. , Huisman H. O. 
Published: September 2010

AbstractThe facile acid‐catalysed dehydration of substituted β‐ionols, e.g. β‐C15‐ and β‐C20‐hydroxy esters, gives a substantial yield of the R (= retro) compounds and not of the corresponding β‐ionylidene compounds. This is correlated with the different properties of these molecules: almost planar configuration of R‐compounds vs. distorted β‐ionylidene derivatives.
Solubility of hydrogen in benzene, cyclohexane, decalin, phenol and cyclohexanol
Authors: Kruyer S. , Nobel A. P. P. 
Published: September 2010

AbstractFor measuring the solubility of a gas in a liquid at about atmospheric pressure a modified stripping method was developed. It was tested by measuring the solubility of hydrogen in benzene. With this method we measured the solubility of hydrogen in cyclohexane, decalin, phenol and cyclohexanol at various temperatures. We also determined the solubility of hydrogen in benzene‐cyclohexane mixtures. Within the accuracy of the experiment the solubility in the mixtures was found to be a linear function of the composition.From the rate of expulsion it was found that under the conditions of the stripping experiments the solubility equilibrium was not established and that the mass transfer between the liquid and the gas was rate determining.
A rapid and sensitive colorimetric microdetermination of free and bound choline
Authors: Böttcher C. J. F. , Pries C. , van Gent C. M. 
Published: September 2010

AbstractThe colorimetric estimation of quaternary ammonium bases with the aid of cis‐aconitic anhydride 6 has been shown to be applicable to choline, and is superior in sensitivity and reproducibility to the usual precipitation methods for determining this substance. It can be applied to substances containing choline, e.g. some of the phospholipids, without the necessity of first liberating free choline by hydrolysis. For this purpose the colour must be developed for a longer time and at a higher temperature than formerly described, until the initial red‐purple colour changes through violet to green. The optimum wavelengths for determining the extinction of the red‐purple and green solutions are 515 and 530 mμ respectively.The intensity of the green colour is linear with concentration over the concentration range 0.3‐5 μg quaternary nitrogen (N4) (= 3‐50μg choline, 20‐300 μg lecithin). The extinction per μg N4 is 0.110 for a light‐path of 1 cm and a final solution volume of 8 ml, and linearity is preserved if the solution is diluted after development of the colour. Both reproducibility and accuracy of the estimation are within ± 4%.
Protonation of ϵ‐caprolactam studied by N.M.R. and infrared techniques
Authors: Ottenheym J. H. , van Raayen W. , Smidt J. , Groenewege M. P. , Veerkamp Th. A. 
Published: September 2010

AbstractChloroform solutions of ϵ‐caprolactam, β‐caprolactam hydrochloride, α‐monochlorolactam and α,α‐dichlorolactam were studied by proton resonance. Comparison of the spectra, which could be fully identified leads to the conclusion that the protonation of the caprolactam takes place on the oxygen atom. This conclusion is supported by evidence obtained from infrared examinations of caprolactam hydrochloride, caprolactam, N‐methyl lactam, and N‐ethyl acetamide, the position of the C=O band pointing to protonation on oxygen.Furthermore, the results of both the infrared and the n.m.r. examination suggest association of the NH‐group.
The autoxidation of isopropylbenzenes to benzoic acids in acid media: II. The attack at the alkyl group
Authors: van Helden R. , Bickel A. F. , Kooyman E. C. 
Published: September 2010

AbstractThe oxidation with oxygen of p‐substituted isopropylbenzenes in butyric acid solution at 130‐150° to the corresponding benzoic acids has been investigated, using manganese and cobalt acetates as catalysts.This reaction is slow compared with the oxidation of the intermediate acetophenones to benzoic acids, discussed in part I. Rates obey a Hammett‐relationship with a p‐value of –1.1. This result has a bearing on the oxidation behaviour of p‐dialkylbenzenes to terephthalic acid, oxidation of the intermediate alkylbenzoic acids being the rate‐determining step. However, p‐alkylbenzoic acids alone appear to be much more refractory towards oxidation than would follow from the Hammett relationship; a study of the oxidation of p‐toluic acid suggested that this is attributable to a short chain length, possibly due to decarboxylation of the acid followed by phenol formation. In the presence of compounds that are readily oxidized, such as p‐xylene, p‐toluic acid may be smoothly converted into terephthalic acid.The bis‐p‐tolyl ether of ethylene glycol (p‐CH3‐C6H4‐O‐CH2‐)2 may be rapidly oxidized to the corresponding dicarboxylic acid, the electron‐repelling substituent increasing the rate of attack at the methyl groups.
Peptide derivatives related to the active site of some hydrolytic enzymes: II. Syntheses of tetrapeptide ethyl esters containing aspartic acid and serine
Authors: van De Linde A. , Kienhuis H. , Verweij A. , van der Holst J. P. J. 
Published: September 2010

AbstractThe syntheses are described of glycyl‐α‐L‐aspartyl‐L‐serylglycine ethyl ester and of the O‐acetylated derivative. The tetrapeptide ethyl esters were obtained by coupling two dipeptide derivatives using the mixed anhydride method, followed by removal of the blocking groups. The dipeptide derivatives were synthesised by the azide method.
On the nature of the bond between BF3 and lactams
Authors: Duynstee E. F. J. , van Raayen W. , Smidt J. , Veerkamp Th. A. 
Published: September 2010

AbstractBF3 forms a 1:1 complex with ϵ‐caprolactam and also with N‐methyl caprolactam. These complexes were investigated by means of I.R. spectroscopy and proton resonance. Both methods clearly showed that in these complexes the BF3 is bound to oxygen.
The characterization of preparations of polyadenylic and polyuridylic acid
Authors: Boldingh W. Hondius , Veldstra H. 
Published: September 2010

AbstractThe composition and molecular size of enzymatically synthesized polyadenylic and polyuridylic acids (poly‐A, poly‐UThe following abbreviations will be used: ADP, UDP, etc. 5′‐diphosphates of adenosine, etc.; poly‐A, ‐U, etc. polynucleotides: polyadenylic acid, etc.; poly(A + U), etc. helical aggregates of the polynucleotides; RNA ribonucleic acid; DNA deoxyribonucleic acid. Different preparations of poly‐A and poly‐U are indicated as e.g. poly‐AB 55, poly‐UB 6B, poly‐AO 7. Chemical and physical data about these preparations are collected in Table V.
) have been studied. The analyses comprised molecular weight, polydispersity, content of nitrogen, phosphorus, carbon, and hydrogen and the presence of residual protein, ‘foreign’ nucleotides, metal ions, and water. Some general aspects of the aggregation of poly‐A and poly‐U were also investigated in this connection.
Rearrangements during aminations of halopyridines, presumably involving a pyridyne intermediate
Authors: Pieterse M. J. , den Hertog H. J. 
Published: September 2010

AbstractWhen reacted with potassium amide in liquid ammonia, both 3‐chloro and 4‐chloropyridine are converted into a mixture containing 3‐amino and 4‐aminopyridine in a ratio of 1:2. The same reaction product results from the animations of 3‐iodo and 4‐iodopyridine. The course of these reactions can be explained by a mechanism involving 3,4‐pyridyne as an intermediate. 2‐Chloro and 2‐iodopyridine only yield 2‐aminopyridine.Rearrangements via ethoxy derivatives of 3,4‐pyridyne probably proceed in aminations of 3‐bromo‐6‐ethoxypyridine and 4‐bromo‐5‐ethoxypyridine. A shift of the substituent from position 3 to 2 occurs in the amination of 3‐bromo‐4‐ethoxypyridine which yields 2‐amino‐4‐ethoxypyridine.An abnormal rearrangement takes place during the amination of 2‐bromo‐6‐ethoxypyridine, 4‐amino‐6‐ethoxypyridine together with 2‐amino‐6‐ethoxypyridine being formed.
Variation de la résistance électrique avec la température pour des systèmes aromatiques: Application à quelques vitrites et leurs produits d'extraction
Authors: de Ruiter E. , Leutner R. , Tschamler H. 
Published: September 2010

AbstractLes systèmes aromatiques peuvent être considérés comme des semiconducteurs intrinsèques. En prenant comme base, d'une part, les valeurs trouvées dans la littérature et, d'autre part, celles déterminées par nous‐mêmes, nous avons recherché les facteurs qui déterminent l'énergie d'activation Δϵ qu'on peut dériver du diagramme log ρ (résistance spécifique) contre 1/T.Nous avons ensuite mesuré la variation de la résistance spécifique ρ en fonction de la température de vitrites bitumineux et de leurs produits d'extraction à la pyridine. De la comparaison relative des Δϵ des vitrites, extraits et résidus, il ressort que les Δϵ des vitrites et résidus sont du même ordre de grandeur et pratiquement indépendants du rang, tandis que les Δϵ des extraits sont toujours plus élevés que les précédents, mais diminuent lorsque le rang augmente. Nous avons tenté une conclusion basée sur les valeurs absolues de Δϵ et les résultats obtenus avec des modèles aromatiques.
Chemistry of the silylamines. V. Self‐condensation of R3Si‐NH2 type silylamines
Authors: Pike R. M. 
Published: September 2010

AbstractThe rates of self‐condensation of a series of silylamines of the type R3SiNH2 to form the corresponding disilazanes, (R3Si)2NH have been measured. The nature of the R groups attached to the silicon atom of the silylamine appreciably affects the rate of condensation. The addition of acid catalyst results in an increase in reaction rate. The observed second‐order kinetics indicate a bimolecular type mechanism.
Migration of an Acyl group in glycerol derivatives: III. An investigation of Fischer's method for the preparation of αγ‐diglycerides
Authors: Hoefnagel M. A. , de Iongh H. , van Den Brink W. Maassen , Schuil R. E. , Verkade P. E. 
Published: September 2010

AbstractHeating of a monoacid diacylglycerol‐α‐iodohydrin or diacylglycerol‐β‐iodohydrin with silver nitrite or silver nitrate in a mixture of alcohol and water leads to an (equilibrium) mixture of the corresponding αβ‐and αγ‐diglycerides. Preparation of a monoacid αγ‐diglyceride in a good yield by this method, which is due to E. Fischer, is possible only if the acyl group of the diacylglycerol‐iodohydrin has a strong tendency towards migration in acid medium, thus, for instance, if it is a fatty acid radical.
Electron spin resonance studies on ziegler catalyst systems: Part II. The system titanium tetrachloride‐aluminium ethyl dichloride
Authors: Adema E. H. , Bartelink H. J. M. , Smidt J. 
Published: September 2010

AbstractElectron spin resonance was measured in a mixture of TiCl4 and (Al(C2H5)Cl2)2 in heptane, mainly at room temperature and at various concentrations of the titanium and aluminium components. Normally, two different particles to be called S1 and S2, carrying an unpaired electron are produced after some time. The concentration of S2 is always lower than the concentration of S1.Some time after the components have been brought together, the concentration of S1 reaches a maximum value equal to about 1.8 × 10−2 times the initial concentration of the aluminium dimer compound; this value may remain constant for some hours. At first the rate of formation of the particle S1 is proportional to the 3/2th power of the aluminium dimer concentration and to the root of the titanium concentration. The k‐value amounts to (14.0 + 0.5) × 10−3 mole−1·l·min−1 at 20°. From experiments conducted at various temperatures an activation energy of 12.8 + 0.8 kcals/mole was found. The concentration of unpaired electrons proves to be influenced by solid TiCl3, ethanol and oxygen.Three types of mechanisms, that may account for the formation of S1 are discussed.These mechanisms all yield complexes of a “TiCl3‐radical” and the dimer of aluminium alkyl chloride (S1). An ion‐complex mechanism is presented as the most probable one. As to the particle S2 a complex of the “TiCl3‐radical” and the monomer of aluminium alkyl chloride is suggested.
Heterocyclic compounds II: Synthesis and reactions of some 2,3‐pyrrolidinediones
Authors: Merchant J. R. , Shah R. J. , Bhandarkar R. M. 
Published: September 2010

AbstractA number of 2,3‐pyrrolidinediones have been synthesised by the condensation of phenylpyruvic, 3,4‐dimethoxyphenylpyruvic and α‐keto‐butyric acid with different aldehydes and amines. In some cases, cinchoninic acids were the products of condensations. The properties and reactions of the pyrrolidinediones have been studied.
The chemistry of cycloheptatriene: Part III: Formation of tropylium salts by autoxidation of cycloheptatriene in acidic media
Authors: ter Borg A. P. , van Helden R. , Bickel A. F. 
Published: September 2010

AbstractTropylium perchlorate and fluoroborate have been prepared by the autoxidation of cycloheptatriene dissolved in acetic acid containing perchloric or fluoroboric acid, respectively. An optimum yield of 60 % (calculated on the strong acid) is obtained by employing twice as much cycloheptatriene as strong acid, 1.4 mmole/1 of an iron salt as a catalyst and a temperature between 40 and 50°.In addition to acid catalysis the reaction shows free‐radical characteristics. These phenomena are discussed in relation to possible mechanisms.The formation of benzene and carbon monoxide from tropylium salts and hydrogen peroxide is markedly retarded by increasing the acidity of the medium (H0) from +1.20 to −1.20.
On charge transfer spectra
Authors: Beukers R. , Szent‐Györgyi A. 
Published: September 2010

AbstractThe relationship between the maximum of absorption of a donor‐acceptor complex and the P value of the relevant donor for a series of donors with the same acceptor is reasonable linear. The P value, measure for the energy of the electron in the highest filled orbital, has the advantage of being calculable for many substances of biological interest. The relationship is still linear for low P values and also for complexes with maxima in the near infrared. The relationship is also tested for polar solvents. In case more than one maximum is formed, only one obeys the rule. Sometimes the deviations observed are systematic, e.g. effect of the solvent and are cancelled when the results of two series (two different acceptors) are compared (Foster's rule).
Synthesis of chromones: IV. 8‐Methoxy‐2‐methylfurano (2′, 3′, 5, 6) chromone, an isomer of visnagin
Authors: Rao Ch. Bheemasankara , Venkateswarlu V. 
Published: September 2010

AbstractThe synthesis of 8‐methoxy‐2‐methylfurano (2′, 3′, 5, 6) chromone, an isomer of visnagin, is reported.
Oscilloscopic determination of kinetic parameters of electrode reactions by means of sine wave current
Authors: Sluyters J. H. 
Published: September 2010

AbstractAn oscilloscopic method for the rapid determination of the kinetic parameters of an electrode reaction, making use of sine wave current is proposed. The features of the method as compared with the cyclic current step method of Wijnen and Smit are discussed. It is shown that the disturbing effect of the double layer capacity can be accounted for more rigorously in the sine wave case.
Quantitative infrared analysis for sulphonate and sulphate esters and a note on the alkylation of nucleoside analogues
Authors: Katritzky A. R. , Shepherd R. G. , Waring A. J. 
Published: September 2010

Abstract9‐Ethylguanine and other simple nucleoside analogues were prepared and their rates of ethylation under physiological conditions were examined. Sulphonate esters can be determined quantitatively by extraction into carbon tetrachloride and measurement of the peak height of the asymmetric SO2 stretching mode.
Migration of an acyl group in glycerol derivatives: IV. Migration of an acyl group upon boiling of glycerol derivatives with a mixture of acetic anhydride and acetic acid
Authors: Hoefnagel M. A. , van Veen A. , Verkade P. E. 
Published: September 2010

AbstractBoiling of diphenyl distearoylglycerol‐α‐phosphate, diphenyl distearoylglycerol‐βT‐phosphate, distearoyl‐α‐methanesulphonylglycerol, and distearoyl‐βT‐(p‐toluenesulphonyl)glycerol with a mixture of acetic anhydride and acetic acid (1:4) gives a mixture of distearoyl‐α‐acetylglycerol and distearoyl‐βT‐acetylglycerol in the proportion of about 9:1. An explanation of these and similar reactions is offered.
Thermodynamic properties of transition metal compounds and coordination complexes: II. The lattice energies of some compounds of the divalent metals Ca ‐ Zn
Authors: Schuit G. C. A. 
Published: September 2010

AbstractThe lattice energies U of octahedrally coordinated Ca ‐ Zn compounds can be represented by an equation‐ U = C + I ‐ neΔwhere C is a constant, I the ionization potential (I1 + I2) of the atom and Δ another constant that is numerically comparable to the spectroscopic ligandfield splitting factor while ne is the number of 3d electrons in eg antibonding orbitals. It is shown that deviations from the predictions of this equation can be explained by changes in coordination number or the occurrence of cation‐cation bonding. The correlation can be derived from the m.o. theory in a simple manner provided that the lattice energy of compounds of inert‐gas ions is linearly dependent on I.
The system iridium ‐ oxygen I. Measurements on the volatile oxide of iridium
Authors: Cordfunke E. H. P. , Meyer G. 
Published: September 2010

AbstractIt is shown experimentally that the volatility of iridium in oxygen at high temperatures is due to the formation of a volatile oxide. The dependence of the partial pressure of this gaseous oxide on the oxygen pressure (in equilibrium with iridium or IrO2) was determined by a transportation method. From the results the formula of the volatile oxide of iridium appeared to be IrO3.The equilibria:2 Ir(s)+ 3 O2⇄ 2 IrO3(g)and2 IrO2(s)+ O2⇄ 2 IrO3(g)were measured as a function of the temperature. The results can be expressed as: log Kp(mm) = ‐ 2034/T ‐ 7.346 and log Kp(mm) = ‐ 27596/T + 16.902, respectively.