bluuebunny/crossref_metadata_2025_split huggingface dataset:
Derivatives of amino‐acids and peptides V. Complex formation of benzyloxycarbonylamino‐acids with their salts
Authors: Grommers E. P. , Arens J. F. 
Published: September 2010

AbstractBenzyloxycarbonylamino‐acids and ‐peptides very easily form addition compounds with their alkali metal salts; this sometimes causes difficulties during the preparation of benzyloxycarbonylamino‐acids or ‐peptides. The complexes may separate in crystalline form when aqueous solutions of the salts are acidified; they can also be prepared by mixing solutions of the free benzyloxycarbonyl derivatives with solutions of appropriate amounts of the salts. Some complexes are oily and fairly soluble in ethyl acetate. From one set of components (Cbo‐amino‐acid and its salt) sometimes more than one type of complex can be obtained each having a characteristic melting point. The solvent used for the crystallisation largely defines the complex. Within one type the salt content can vary. It seems that within certain limits an arbitrary number of metal ions can replace protons of COOH groups.
Determination of equilibrium constants for a number of metal‐phosphate complexes
Authors: Wolhoff J. A. , Overbeek J. Th. G. 
Published: September 2010

AbstractMany metal ions form soluble complexes with pyro‐ and tripolyphosphate. Complex formation entails a decrease in pH. By measuring the pH and in some cases the concentration of free metal ions, equilibrium constants for a number of metal‐phosphate complexes were determined at 25° and at 40°. Activity corrections were applied. The tendency to form complexes increases in the following order:

Tripolyphosphate has somewhat stronger complexing properties than pyrophosphate. The influence of the temperature is in most cases small. Constants obtained are listed in Table V.
A cryoscopic study of the behaviour of s‐trinitrobenzene and some other organic compounds in ethanolamine
Authors: Baliah V. , Ramakrishnan V. 
Published: September 2010

AbstractThe behaviour in ethanolamine of some aromatic polynitro compounds and compounds containing active methylene groups has been studied cryoscopically. It is suggested that s‐trinitrobenzene, s‐trinitro‐t‐butylbenzene, and picramide ionise by the proton‐transfer mechanism. s‐Trinitroanisole, besides exhibiting a similar behaviour, undergoes a solvolytic reaction, the methoxyl group being replaced by NH.CH2CH2OH. Picric acid ionises as (NO2)3C6H2OH → (NO2)3C6H2O− + H+. Diethyl malonate, ethyl acetoacetate, and acetylacetone undergo solvolysis. Bis(phenylsulphonyl)methane ionises by the proton‐transfer mechanism.
Chemistry of acetylenic ethers XXXIX: Reactions of acetylenic ethers with carbonyl compounds in aqueous solution
Authors: Vieregge H. , Arens J. F. 
Published: September 2010

AbstractAcetylenic ethers V react with aldehydes in aqueous medium at room temperature to yield the hydroxy esters VII and IX, often together with a small amount of the unsaturated ester VIII. The acetylenic ethers do not react in such a way with ketones and aromatic aldehydes but a similar reaction occurs with ethyl mesoxalate.
Chemistry of acetylenic ethers XL: Rearrangement during the conversion of ethoxyethyne with butynedioic acid
Authors: Cley J. , Arens J. F. 
Published: September 2010

AbstractEthoxyethyne I readily reacted with an ethereal solution of butynedioic acid V affording a product, C12H16O7, obviously formed from 1 mole of butynedioic acid, two moles of ethoxyethyne and one mole of water. Further investigations revealed that it had the anhydride structure IX. By performing the conversion in alcohol, tetraethyl DL‐butane‐1,2,3,4‐tetra‐carboxylate X, was obtained.The reactions probably involved a rearrangement as pictured in the scheme on page 931 and thus proceeded via the bis‐ketene VIII.From phenylpropiolic acid and ethoxyethyne the anhydride XI of 1‐phenylnaphthalene‐2,3‐dicarboxylic acid was obtained in low yield. Tetrolic acid was converted into its anhydride in high yield.
Nucleophilic aromatic addition: I. The reaction of diazomethane with 1,3,5‐trinitrobenzene
Authors: de Boer Th. J. , van Velzen J. C. 
Published: September 2010

AbstractThe structure of the reaction product from 1,3,5‐trinitrobenzene and an excess (i.e. at least four moles) of diazomethane, as found many years ago by Heinke, is shown to be a seven‐membered ring‐compound condensed with two cyclopropane rings and with one pyrazoline ring (VII). If 1,3,5‐trinitrobenzene is treated with diazomethane in a molar ratio of 1:3, no pyrazoline derivative is formed, but a hitherto unknown “tris‐methylene” derivative (VI), containing a seven‐membered ring system condensed with two cyclopropane rings. This remarkably stable compound is an intermediate in the reaction with excess of diazomethane. When the molar ratio of the reactants is reduced to 1 : 2 or 1 : 1, the “trismethylene” derivative (VI) results, together with unchanged 1,3,5‐trinitrobenzene.
The preparation of pure silicon
Authors: van der Linden P. C. , de Jonge J. 
Published: September 2010

AbstractAn apparatus is described for the preparation of pure silicon by thermal decomposition of trichlorosilane on a hot tantalum wire in a hydrogen atmosphere. The polycrystalline silicon is obtained in the form of rods with a diameter of about 15 mm and a length of 20‐40 cm. The yield of Si is 45‐50 % if calculated on the Si‐content of SiHCl3. From resistivity measurements, the boron content of the silicon obtained can be calculated to be 0.5 × 10−6% (resistivity of single crystals about 300–500 ohm‐cm p‐type).
Kinetics and mechanism of the cyclic‐hemiacetal ring opening in 2‐keto‐L‐gulonic acid. A polarographic study
Authors: Los J. M. , Gaspar N. J. 
Published: September 2010

AbstractThe occurrence of two consecutive cathodic waves, both with absolute rate control, in the case of the polarographic reduction of 2‐keto‐L‐gulonic acid in a buffer solution of malonic acid (pH between 4.8 and 6.3) is described. The theory of this case is based on the assumption that 2‐keto‐gulonic acid or its anion predominantly exists in the cyclic‐hemiacetal form, which is non‐reducible, but which produces the free keto‐acid or its anion by a very rapid reaction in the zone around the dropping mercury electrode. The latter substances are reducible, with different half wave potentials. Expressions in the relevant rate constants are derived for both the total current and the current of the first wave. This does not permit the calculation of all the rate constants involved. However, it could be shown that the wave heights are related to pH in the way predicted by the theory. Definite conclusions with respect to the relative magnitude of the rate constants could be drawn. The single wave in the lower pH range of 0.2 to 3.5 was also studied as a function of pH. The reaction mechanism is discussed on the basis of the relationships found and in connection with the expected influence of the ionization of the carboxyl group upon the reactivity of the catalytic species present. The process of ring closure or opening was shown to be second‐order, rather than third.
Migration of an acyl group in glycerol derivatives: I. Migration of the acyl group in monoglycerides in acid medium
Authors: van Lohuizen O. E. , Verkade P. E. 
Published: September 2010

AbstractFor a number of pairs of isomeric α‐ and β‐monoglycerides with a carboxylic acid as component acid it is shown that these isomers mutually rearrange in ethanolic hydrogen chloride. At 25° the equilibrium mixture invariably contains about 88% of α‐ and consequently about 12% of β‐monoglyceride.From measurements of the migration rate of β‐monobenzoylglycerol in the said medium at 25° it appeared that the migration reaction shows kinetics of the first order and that the migration rate is directly proportional to the concentration of the catalyst. Addition of small quantities of water to the medium retards the migration reaction to a very great extent.The determination of α‐monoglyceride in mixtures of α‐ and β‐monoglyceride was effected by periodic‐acid oxidation, as described previously.The migration rate constant of a number of β‐monoglycerides was determined under identical experimental conditions. The nature of the acyl group has great influence on the migration rate, but not ‐ see above – on the position of the equilibrium.The mechanism of this intramolecular rearrangement of the monoglycerides is discussed and used for an explanation of the facts observed.Monoglycerides with a sulphonic acid as component acid do not show any tendency towards rearrangement under the same experimental conditions.
Spectrophotometric investigations of the mechanism of complex formation: Part I: General description of the technique
Authors: Adema E. H. , Visser R. , Sixma F. L. J. 
Published: September 2010

AbstractA description is given of a cell used in taking ultraviolet spectra, especially at lower temperatures, and of a cryostat which can be kept constant within 0.02° down to −150°. Whilst the spectra are being taken, the concentration can be increased by means of a microburette, with exclusion of moisture and oxygen. Thus rates of formation and positions of equilibria of unstable systems can be determined.
Reactions between acids and thiourea: Part I. The formation of amides from acids and thiourea
Authors: Rahman Aziz‐Ur , Medrano Miguel A. , Mittal O. P. 
Published: September 2010

AbstractA method for the preparation of acid amides by heating an equimolecular mixture of acid and thiourea, is described. The method has been successfully applied to aliphatic mono‐ and di‐basic acids, aryl‐aliphatic acids as well as benzoic acid. The yield has been found to be dependent upon the relative volatility of the acid employed for the reaction. Best yields have been obtained with aryl‐aliphatic acids. The mechanism of amide formation from acid and thiourea, based upon the intermediate addition of carboxylic acid to thiocyanic acid, the latter formed by the decomposition of thiourea, is suggested and an electronic representation of the mechanism is given.
Precipitate impregnated membranes: I. Some properties of the BaSO4‐cellophane membrane
Authors: Hirsch‐Ayalon P. 
Published: September 2010

AbstractWashed‐out BaSO4‐cellophane membranes have been analysed. The number and strength of acid groups in them are the same as in the original cellophane. Membrane diffusion potentials arising with different electrolytes at washed BaSO4 membranes have been measured in the usual way and found to be the same as with original cellophane. Direct examination of the permeability of effective BaSO4 membranes to Ba and SO4 ions in a special case (viz. our “standard experiment”) confirmed that this permeability is extremely low, amounting practically to impermeability in this case. This property, as well as the characteristic membrane potentials at the effective BaSO4 membrane depend on the simultaneous presence of Ba and SO4 ions in the adjacent solutions. The special behaviour of the effective BaSO4 membrane is not due to “fixed charges” in the usual sense.
Investigations on sterols XIV studies on vitamin D and related compounds XII the photoisomerization of lumisterol2
Authors: Rappoldt M. P. 
Published: September 2010

AbstractKinetic experiments on the isomerization of lumisterol2 under the influence of ultraviolet light of various wavelengths are reported. The experiments indicate that neither tachysterol2 nor ergosterol are primary reaction products of lumisterol2. Lumisterol2 is exclusively converted into pre‐ergocalciferol. The quantum yield of this reaction is 0.41 at 2537 Å.
Studies in IVth group organometallic chemistry. V: Preparation of some p‐styrenyl‐substituted derivatives of germanium, tin and lead
Authors: Noltes J. G. , Budding H. A. , van der Kerk G. J. M. 
Published: September 2010

AbstractThe preparation of triphenylmono‐ and diphenyldi‐p‐styrenyl derivatives of germanium, tin and lead is described. The infra‐red spectra of these compounds are discussed.
The decomposition of organic hydroperoxides: Part III. Kinetics of the acid‐catalyzed decomposition of benzyl‐type hydroperoxides
Authors: de Ruyter van Steveninck A. W. , Kooyman E. C. 
Published: September 2010

AbstractThe HClO4‐catalyzed decomposition of a number of alkylbenzyl hydroperoxides has been investigated by a study of the reaction kinetics in 50% w ethanol at 50°C. A Hammett relation (p = ‐4.57) has been found to exist for the decomposition of ring‐substituted α,α‐dimethylbenzyl hydroperoxides to the corresponding phenols and acetone, σ+ values giving the best correlation. An electrolyte effect has been observed in the decomposition of the hydroperoxides studied, the magnitude of which runs parallel to the reactivity of the various hydroperoxides. A qualitative explanation of this phenomenon can be given in terms of differences in solvation for the different transition state complexes. Data for the enthalpy and entropy of activation are in accordance with this assumption. Our results provide further support for the recently proposed mechanism of the acid‐catalyzed hydroperoxide decomposition. The effect of nuclear substituents and the observation of the electrolyte effect permit of a detailed description of the transition state complex. In the acid‐catalyzed decomposition of some substituted alkylbenzyl hydroperoxides other reactions have been encountered, which are discussed briefly.
Preparation of quinazoline derivatives through ring closure of aromatic ortho‐cyano‐acylamino compounds in alkaline alcoholic or phenolic medium II
Authors: Breukink K. W. , Verkade P. E. 
Published: September 2010

AbstractSome new quinazoline derivatives were prepared by boiling the appropriate ortho‐cyano‐acylaminobenzene in alkaline alcoholic medium. Proofs of the constitution of the quinazoline derivatives are given.
An extraction procedure for the colorimetric determination of silica
Authors: Wilson H. N. , Skinner J. M. 
Published: September 2010

AbstractTri‐isodecylamine is proposed as a versatile reagent for extracting inorganic anions from aqueous solution: its use in the determination of silica is described. The advantages of a non‐aqueous extraction method are discussed and full instructions given for the determination of silica in anhydrite and the like.
Gas hydrates of nitrogen and oxygen
Authors: van Cleeff A. , Diepen G. A. M. 
Published: September 2010

AbstractGas hydrates of nitrogen and oxygen are described.P ‐ t relations of the three‐phase equilibria in the system nitrogen ‐ water are given from ‐ 4 to 18°C at pressures up to 1000atm. The dissociation pressure of oxygen hydrate is given at 0°C.
Olefinic unsaturation of styrenated linseed oils
Authors: Tiong Sie Swan , Waterman H. I. 
Published: September 2010

AbstractThe olefinic unsaturation of styrenated linseed oils has been determined by quantitative ozonolysis. Products obtained by reaction of gaseous styrene with linseed oil under various conditions have been examined and are characterized by means of a diagram in which the relative decrease in unsaturation is plotted against the relative decrease in saponification value.From the data obtained it can be concluded that two types of reactions are mainly responsible for the conversion of styrene, viz. the formation of styrene polymers and copolymerization involving the double bonds of the fatty‐acid residues. Copolymerization of linseed oil with styrene does not take place to an appreciable extent at temperatures below 200°. At 280°, however, practically no high‐molecular‐weight polystyrene is formed and the take‐up of styrene is mainly due to copolymerization.
The pH of some standard solutions in methanol and methanol‐water mixtures at 25° I. Theoretical Part
Authors: de Ligny C. L. , Luykx P. F. M. , Rehbach M. , Wieneke A. A. 
Published: September 2010

AbstractIt has been shown that pH* values, determined by the electrometric method in solvents other than water, can be interpreted as ‐log mHγ*H if the pH meter is standardized by means of a standard solution in the same solvent. The pH* of standard solutions in methanol and methanol‐water mixtures can be determined by application of the same method as has been used by the National Bureau of Standards for the measurement of the pH of standard solutions in water.The errors that may occur when the method of the N.B.S. is applied to standard solutions in solvents other than water have been discussed. In order to correct these errors we calculated, by the method of Fuoss and Onsager, the values of K and å for NaCl, KCl, KBr and KI in methanol, from literature data on the conductivity. The conductivity of solutions of NaBr and LiCl cannot be described satisfactorily by the equation of Fuoss and Onsager.
Investigations on pesticidal phosphorus compounds I. Fungicides, insecticides and acaricides derived from 3‐amino‐1,2,4‐triazole
Authors: van den Bos B. G. , Koopmans M. J. , Huisman H. O. 
Published: September 2010

AbstractThe preparation and the biological properties of a number of compounds with fungicidal, insecticidal and acaricidal activities are described. The compounds were prepared by substitution of a phosphorus containing group for a hydrogen atom of the 1,2,4‐triazole nucleus in 3‐amino‐1,2,4‐triazole or a 5‐ substituted derivative thereof.Biological activity was highest when the phosphorus containing group was a bis(dimethylamido)phosphoryl group.
Chemistry of acetylenic ethers XLIII: Reactions of oximes with ethoxyethyne
Authors: Tigchelaar‐Lutjeboer H. D. A. , Bootsma H. , Arens J. F. 
Published: September 2010

AbstractIn the reaction of oximes I with ethoxyethyne II at 75‐90° orthoesterlike products III are formed. Some aldoximes, however, are dehydrated to nitriles. The results are summarized in Table I.
Chemistry of acetylenic ethers XLIV: Additions to the ethyl ester and anilide of (Ethylthio)propynoic acid
Authors: Bonnema J. , Alkema H. J. , Arens J. F. 
Published: September 2010

AbstractThe addition of electrophilic reagents to ethyl (ethylthio)propynoate II occurs at carbon atom 2. Uncharged nucleophilic reagents (amines) are also added at carbon atom 2, but charged nucleophiles (ethoxide ion and the carbanion of malonic ester) interact at carbon atom 3. Additions to the anilide of (ethylthio)propynoic acid (XVIII) take a similar course. The results are discussed and explained.
Electro‐osmosis experiments at the germanium/electrolyte interface
Authors: Sparnaaij M. J. 
Published: September 2010

AbstractMeasurements of the electro‐osmotic transport of liquid in the germanium (powder) electrolyte solution were carried out. The results can be explained by a theory, which is given by Verwey and Payens, which was originally proposed for surface layers consisting of weakly ionized fatty acids. In the case of germanium it should be assumed that a weakly ionized germanic acid is present at the surface, giving the surface a negative charge. The experiments almost break down when p‐type Ge is used. This can be explained by potential current characteristics using p‐type or n‐type Ge as the anode.
Alkyl‐substituted benzaldehydes
Authors: Klouwen M. H. , Boelens H. 
Published: September 2010

AbstractThe ortho‐, meta‐ and para‐isomers of methyl‐, ethyl‐, isopropyl‐ and tertiary butylbenzaldehyde have been synthesized for the purpose of an olfactory study1 To be published.
. The aldehydes were isolated and purified via the semicarbazones. The ultra‐violet absorption spectra of the aldehydes as well as those of the semicarbazones were determined. Particular attention was paid to ortho‐alkylbenzaldehydes as to whether there is any steric effect of mesomerism.
Studies in IVth group organometallic chemistry. VI: Preparation and polymerization of IVth group organometallic derivatives of styrene and α‐methylstyrene
Authors: Noltes J. G. , Budding H. A. , van DerKerk G. J. M. 
Published: September 2010

AbstractThe preparation of a series of IVth group organometallic vinyl monomers derived from styrene and α‐methylstyrene, respectively, is described. Thermal or radical‐initiated polymerization of the styrene derivatives afforded transparent, solid organometal‐substituted polystyrenes. The monomers of the general structure p‐(CH3)3MIVC6H4CH  CH2 display appreciably different rates of radical‐initiated polymerization, in the order Pb > Si > C > Ge>Sn.
Investigations on sterols XVIII: The synthesis and properties of some hydroxylated 9β,10α‐pregnanes
Authors: Westerhof P. , Reerink E. H. 
Published: September 2010

AbstractThe synthesis of 17α‐hydroxy‐9β,10α‐progesterone, 6‐dehydro‐17α‐hydroxy‐9β,10α‐progesterone and some acylates of these compounds, and of 21‐acetoxy‐9β,10α‐progesterone is described.
Rapid determination of vapour‐liquid equilibria
Authors: Smit W. M. , Ruyter J. H. 
Published: September 2010

AbstractAn apparatus for the determination of vapour‐liquid equilibria at constant pressures within the range of 760 to 10 mm Hg is described.The apparatus can produce eight pairs of samples of coexisting vapour and liquid, evenly distributed over the concentration range in one run within two hours.As a proof of its operation the results obtained with six binary systems are recorded. The systems investigated are:Carbon tetrachloride‐benzene.Carbon tetrachloride‐toluene.Benzene‐dichloroethane.n‐heptane‐methylcyclohexane.methylcyclohexane‐toluene.n‐decane‐trans‐decahydronapththalene.The results obtained agree with a thermodynamic criterion which is discussed separately.
End‐to‐end distances in short‐chain molecules as determined by X‐ray diffraction in the liquid
Authors: Holleman Th. 
Published: September 2010

AbstractThe distribution of end‐to‐end distances in liquid short‐chain molecules has been studied by means of X‐ray diffraction. Solutions in n‐decane of α,ω‐diiodo‐n‐alkanes have been investigated.The distribution of intramolecular I‐I distances in these compounds was obtained by comparing the experimental X‐ray patterns of the diiodides with the pattern of a monoiodide solution having the same iodine‐to‐carbon ratio. Although the smallness of the observed effect renders the conclusions rather uncertain, the results are in general agreement with a distribution function calculated from a simple theoretical model.
The infrared absorption spectra of some aromatic hydroxy‐ketones
Authors: Cullinane N. M. , Woolhouse R. A. , Bailey‐Wood V. V. 
Published: September 2010

AbstractThe infrared spectra of dilute solutions of some hydroxyacetophenones, hydroxybenzophenones and hydroxyacetonaphthones have been measured. The effect of chelation on both the hydroxyl and carbonyl frequencies has been noted.
Oxidation of benzoic acid‐1‐14C to phenol
Authors: Schoo W. , Veenland J. U. , Bigot J. A. , Sixma F. L. J. 
Published: September 2010

AbstractUsing benzoic acid‐1‐14C the position of the hydroxyl group formed in the oxidation of benzoic acid to phenol and carbon dioxide is definitively identified as ortho in relation to the original carboxyl group.
Polarography of alkyl‐substituted 3‐phenyl‐4‐hydroxy coumarins
Authors: van Zanten B. , Th. Nauta W. 
Published: September 2010

AbstractAmong the alkyl substituted 3‐phenyl‐4‐hydroxycoumarins, synthesized to investigate the relationship between chemical structure and biological activity in this class of compounds2, eleven possess one or moreorthosubstituents.As the steric effects oforthosubstitution can manifest themselves in the polarographic behaviour, the half wave potentials of these compounds were measured and attempts were made to find relationships between the values obtained and to determine the steric effect in each case. In addition, an equation was derived for the first reduction wave in the polarogram and a reaction mechanism for this polarographic reduction is suggested.