bluuebunny/crossref_metadata_2025 huggingface dataset:
Direct substitution in pyridine ring systems by basic reagents
Authors: Vajda T. , Kovács K.
Published: September 2010

Pyridine reacts directly with an alkylamine in toluene in the presence of powdered sodium or potassium. The yield of the 2‐alkylamino‐pyridine increases proportionally with the amounts of pyridine and sodium used. α‐Picoline and quinoline react in the same manner. Some derivatives of these heterocyclic bases have been prepared by reaction with primary alkyl‐ or aralkyl‐amines. Experiments with aromatic or secondary amines were unsuccessful. A mechanism has been proposed for this direct substitution in view of the experimental facts.
Reserpine analogues I
Authors: de Groot S. , Strating J.
Published: September 2010

The systematic synthesis of the simplified reserpine skeleton to the stage at which reserpine like activity was observed, is described.
Fries rearrangement of the benzenesulphonates of xylenols
Authors: Baliah V. , Uma M.
Published: September 2010

The benzenesulphonates of xylenols undergo isomerisation when heated with anhydrous aluminium chloride, giving hydroxy‐sulphones, the structures of which have been established.
Condensations of isatinic acid with ureas, ethyl carbamate and guanidine
Authors: Stefanović Gj. , Lorenc Lj. , Lj. Mihailović M.
Published: September 2010

By condensing the potassium salt of isatinic acid ‐ (o‐aminophenyl)‐glyoxylic acid ‐ with urea, N‐substituted ureas and ethyl carbamate, 2‐hydroxyquinazoline‐4‐carboxylic acid was obtained, in excellent yield. In a similar condensation with guanidine, potassium isatinate reacted quantitatively to give 2‐aminoquinazoline‐4‐carboxylic acid. Various derivatives were obtained from these new acids by methylation and decarboxylation reactions.
Investigations in the vitamin B6‐series: I. synthesis of nor‐vitamin B6
Authors: van der Wal B. , de Boer Th. J. , Huisman H. O.
Published: September 2010

The synthesis is described of nor‐vitamin B6(nor‐pyridoxol) by a selective demethylation of a suitable vitamin B6precursor. The demethylation is accomplished in a three step process following the sequence CH3→ CHO → COOH → H, in which SeO2appears to be a particularly selective oxidant for the first step. The nor‐vitamin B6proves to be biologically inactive on the growth ofSaccharomyces carlsbergensisas well as in growth‐tests on rats

G. PolandK. J. Klein Obbink,ibid.80, 217 (1961).

.
Tests of the biological activity of nor‐vitamin B6
Authors: Pol G. , Obbink H. J. Klein
Published: September 2010

Nor‐vitamin B6 is inactive as a substitute for vitamin B6 in growth tests with Saccharomyces carlsbergensis and does not inhibit the effect of vitamin B6. It has little, if any, effect on the growth of vitamin B6‐deficient rats.
Fuming sulphuric acid: Dependence of the concentration of sulphur trioxide and its activity coefficient on the composition of oleum
Authors: Cerfontain H.
Published: September 2010

UV absorption measurements of fuming sulphuric acid solutions of varying composition (3‐60% sulphur trioxide) were made at 25±2°. From these measurements the concentration dependence of sulphur trioxide on acid composition was estimated and compared with calculated sulphur trioxide concentrations assuming the simple equilibrium

H2SO4 + SO3 ⇌ H2S2O7 [6].

From this comparison it was deduced that K6 ≥ 5 mole−1 ·l. The sulphur trioxide concentration in 100% sulphuric acid at 25 ± 2° was calculated with this value for K6 to be 8 × 10−5 mole·l−1 at the most.

Evidence is put forward that the activity coefficient of sulphur trioxide is almost independent of the composition of oleum over the acid range studied.
Liquid‐liquid extraction of metal salts from acidic solutions using amine salts: Derivation of a formula for D o/a
Authors: van Ipenburg K.
Published: September 2010

In this article on the SX of metal salts by amine salts some formulae have been derived for the distribution ratio D o/a for a metal salt, partitioning between an acidic aqueous layer and an organic phase, containing amine salts.

The effects of association of the amine salt, or of the extracted complex or both, are taken into account, as is the effect of the simultaneous extraction of two or more metal salts, the formation of more than one complex per metal salt and the presence of different kinds of anions.

The ways, in which formulae may be derived, if two or more active solvents are present in the organic phase at the same time, or when the diluent does not behave inertly, are outlined.
The reaction of 4‐chloropyridine with some amines
Authors: Wibaut J. P. , Broekman F. W.
Published: September 2010

4‐Chloropyridine reacts with primary and secondary amines with the formation of substituted 4‐aminopyridines. Amongst tertiary amines it reacts only with pyridine.
Reserpine analogues: II. β‐Phenylethylamine derivatives
Authors: Kralt T. , Asma W. J. , 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‐phenylethylamine derivatives.
The condensation of rhodanine and derivatives with pyridine and quinoline aldehydes
Authors: Allan F. J. , Allan G. G. , Thomson J. B.
Published: September 2010

The condensation products of rhodanine, 3‐ethylrhodanine, 3‐phenylrhodanine, 3‐allylrhodanine and 3‐carboxymethylrhodanine with various substituted and unsubstituted pyridine and quinoline aldehydes have been prepared for bacterial and fungicidal evaluation. An earlier series of unsubstituted pyridylmethylene‐rhodanines has thus been extended to include products substituted in either or both of the heterocyclic rings. Such substitution may enhance the already known fungicidal character of such rhodanine‐aldehyde condensation products. The products obtained by the condensation of the quinoline aldehydes may be considered as substituted in a similar manner as the less accessible dialkylpyridine products and it is possible that these two types of compounds will show a similarity in biological activity. Condensations between the rhodanines and the aldehydes were carried out in acid medium and crystalline coloured condensation products were obtained in good yield.
Reserpine analogues: III. Alkoxy‐β‐phenylethylamine derivatives
Authors: Kralt T. , Asma W. J. , Moed H. D.
Published: September 2010

The synthesis of a series of compounds resembling in some respects the reserpine alkaloid and containing a β‐phenylethylamine configuration substituted at the phenyl group with alkoxyl groups is described.
The halogenation of aromatics: Part VI. Types of reactions occurring in the gas‐phase halogenation of benzene derivatives
Authors: Engelsma J. W. , Kooyman E. C.
Published: September 2010

A series of chlorinations of benzene derivatives C6H5X showed that three main reaction types may be distinguished, viz. a) substitutions into the nucleus with retention of X (X = C6H5‐O, Cl, F, CN, CCl3, COCl, COOCH3), b) substitution within the group X (X = alkyl, CHO, probably OCH3) and c) exchange of X for Cl (X = NO2, CHO, Br, probably Cl).

Bromination of chlorobenzene led to bromobenzene and bromochlorobenzenes as well as to dibromobenzenes and dichlorobenzenes. Isomer distributions in the latter two dihalides were slightly different from those found in the bromination of bromobenzene and chlorination of chlorobenzene, respectively.

Some of the mechanisms involved are briefly discussed.
Stereoselective preparation of DL‐4‐allohydroxyproline
Authors: Beyerman H. C.
Published: September 2010

A convenient preparation is described of DL‐4‐allohydroxyproline by reduction of DL‐4‐oxoproline with sodium borohydride in aqueous methanol. This reduction proceeds without appreciable formation of DL‐hydroxyproline, as shown by paper chromatography and by paper electrophoresis. The allo‐configuration of the reduction product (OH/COOH in cis‐position) was proved further by conversion of the latter into its lactone hydrobromide.
Studies on cyclohexane derivatives: I. A chemical proof of the configuration of the two 1,4‐dimethyl‐cyclohexanes
Authors: van Bekkum H. , Kleis A. A. B. , Massier A. A. , Verkade P. E. , Wepster B. M.
Published: September 2010

Starting from cis‐ and trans‐cyclohexane‐1,4‐dicarboxylic acid, cis‐and trans‐1,4‐dimethylcyclohexane are prepared in a way that leaves no doubt as to the configuration of the latter compounds.
Studies on cyclohexane derivatives: II. Preparation and chemical proof of the configuration of the two 4‐methylcyclohexanecarboxylic acids
Authors: van Bekkum H. , Kleis A. A. B. , Massier A. A. , Medema D. , Verkade P. E. , Wepster B. M.
Published: September 2010

The preparation of pure low‐melting 4‐methylcyclohexanecarboxylic acid (m.p. 30.5‐31.5°) is described for the first time.

By chemical means it is proved that low‐melting 4‐methylcyclohexanecarboxylic acid possesses the cis‐configuration and the high‐melting isomer the trans‐configuration. For this purpose these acids were converted into cis‐ and trans‐1,4‐dimethylcyclohexane respectively, using reactions which take place without any change of configuration at the cyclohexane nucleus. The configuration of these two hydrocarbons has been proved in the first paper of this series.
Migration of an acyl group in glycerol derivatives: II. Transformation of diacylglycerol‐β‐iodohydrins into diphenyl diacylglycerol‐α‐phosphates
Authors: Hoefnagel M. A. , Hartman‐Köhler A. H. , Verkade P. E.
Published: September 2010

The action of silver diphenyl phosphate on a diacylglycerol‐α‐iodohydrin or the isomeric diacylglycerol‐β‐iodohydrin in benzene as medium gives the diphenyl diacylglycerol‐α‐phosphate in practically equal and very satisfactory yields. In the latter case therefore a migration of an acyl group from an α‐ into the β‐position occurs.

The reaction has been studied for the compounds with stearoyl, 4‐methoxybenzoyl, and 2,6‐dimethyl‐4‐nitrobenzoyl as the acyl group. It proceeds almost equally smoothly in all cases.

On the basis of these facts the reaction mechanism is briefly discussed.
Contact angles; wetting and de‐wetting of mercury: Part II. Theory of wetting
Authors: Smolders C. A.
Published: September 2010

A theory is given for the behaviour of contact angles, as a function of the concentration of surface active substances, observed in wetting and de‐wetting experiments of metal and mineral surfaces.

It is shown, that the change of the contact angle with solute concentration can be related quantitatively to the adsorption densities at the three interfaces, which meet at the line of contact.

Some published results are discussed in terms of the theory developed.
The V‐T‐x space model of the ethylene‐naphthalene system II
Authors: van Welie G. S. A. , Diepen G. A. M.
Published: September 2010

Projections of the V‐T‐x space model of the ethylene‐naphthalene system are derived from the observations recorded in the preceding publication 1 together with some supplementary measurements. The value for the critical volume at the second critical endpoint is found to be 77.0 ml/mol.

A number of T‐x and V‐x sections through the space model are derived from the same observations.
The mull spectra of NaNO2, KNO2 and AgNO2
Authors: Ketelaar J. A. A. , Schutte C. J. H.
Published: September 2010

The 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

The 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

From 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

The 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

The 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

Pure 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

A 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.
Investigations on Herbicides IV: The synthesis of 2,6‐dichlorobenzonitrile
Authors: Koopman H.
Published: September 2010

Four new methods are described for synthesizing 2,6‐dichlorobenzonitrile.
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

The 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

The 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

For 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

The 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

Chloroform 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.
(Dichloro‐fluoromethyl)sulfenyl chloride
Authors: Kloosterziel H.
Published: September 2010

Evidence is presented that the compound obtained from trichloromethylsulfenyl chloride and mercuric fluoride is dichlorofluoromethylsulfenyl chloride.
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

The 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

The 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

BF3 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

The composition and molecular size of enzymatically synthesized polyadenylic and polyuridylic acids (poly‐A, poly‐U

The 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

When 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

Les 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

The 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

Heating 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

Electron 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

A 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

Tropylium 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

The 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

The 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

An 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

9‐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

Boiling 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

The lattice energies U of octahedrally coordinated Ca ‐ Zn compounds can be represented by an equation

‐ U = C + I ‐ neΔ

where 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

It 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)and

2 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.
Synthesis and physiological properties of some heterocyclic‐aromatic sulphides and sulphones: II. Synthesis of some aryl‐pyrimidyl, aryl‐thiazolyl and aryl‐thienyl sulphides
Authors: van Zwieten P. A. , Huisman H. O.
Published: September 2010

The synthesis of some heterocyclic‐aromatic sulphides with potential acaricidal properties is described. The benzene nucleus in these sulphides is substituted either with a para‐chlorine atom or with three chlorine atoms in positions 2,4 and 5. The heterocyclic nuclei are pyrimidine, thiazole and thiophen. These nuclei are either unsubstituted or carry a halogen substituent; only in the thiophen series a nitro group is substituted.
The chemistry of cycloheptatriene: Part V: Reactions of tropone and 2‐chlorotropone with Grignard reagents
Authors: ter Borg A. P. , van Helden R. , Bickel A. F.
Published: September 2010

Interaction of tropone and phenylmagnesium bromide yields 2‐phenyl‐2,7‐dihydrotropone (II). This compound is in thermal equilibrium with 2‐phenyl‐6,7‐dihydrotropone (III) in a 1: 4 ratio.

The reaction of 2‐chlorotropone with isopropylmagnesium bromide yields a mixture of chloroisopropyldihydrotropones, which upon dehydrochlorination gives rise to 2‐isopropyltropone. This compound may be converted into 3‐isopropyltropolone (α‐thujaplicine).
The photooxidation of nylon 6 and 66
Authors: Boasson E. H. , Kamerbeek B. , Algera A. , Kroes G. H.
Published: September 2010

The chemical changes occurring in nylon (6 and 66) on irradiation have been studied.

The results confirm earlier work on model systems which showed the main attack to be between the‐NH‐group of the amide bond and the adjacent‐CH2‐group. However, a number of products were found that indicate a more complicated course of the reaction.

The similarily of photooxidation and thermal degradation8 is pointed out.
The t‐butoxy group, a novel hydroxyl‐protecting group for use in peptide synthesis with hydroxy‐amino acids
Authors: Beyerman H. C. , Bontekoe J. S.
Published: September 2010

We have found a novel way of protecting the hydroxyl function in hydroxy‐L‐amino acids, making use of the t‐butoxy group, which is readily split by acids, but not by bases.

This group is introduced by acid‐catalysed addition of isobutene to N‐acylated hydroxy‐L‐amino acids. The blocking group is easily removed at or below room temperature with trifluoroacetic acid without racemization and without breaking peptide bonds 1,2
Exchange of alkylgroups in triethyl aluminium, diethyl aluminium chloride and a mixture of these substances, and in a mixture of methyl aluminium dichloride and dimethyl aluminium chloride
Authors: Smidt J. , Groenewege M. P. , de Vries H.
Published: September 2010

Proton magnetic resonance has shown that there is exchange between the outer‐ and the bridge‐alkylgroups in dimeric triethyl aluminium at room temperature. At lower temperatures the rate of exchange diminishes, and at −60° exchange is hardly noticeable.

In diethyl aluminium chloride no exchange of alkylgroups was found between room temperature and −60°. The observation fits in well with the concept of chlorine bridges in the dimer.

In a 1:1 mixture of both compounds exchange of alkylgroups was observed at room temperature. Lowering of the temperature first stops the exchange between the alkylgroups of the two different compounds and then also stops the exchange between the alkylgroups in the triethyl aluminium.

In a 1:1 mixture of methyl aluminium dichloride and dimethyl aluminium chloride it was also found that upon a lowering of the temperature the exchange between alkylgroups stops.
Note on the reactivity of some o‐(hydroxybenzoyl) benzoic acids towards diazomethane
Authors: Bellaart A. C. , Kooistra C. , Koningsberger C.
Published: September 2010

Reactions between diazomethane and several o‐(hydroxybenzoyl)benzoic acids were studied both in purely ethereal solutions as well as in presence of methanol. In all cases the phenolic groups involved appear to be more or less sluggish in their response. On the other hand, it is also noted that nitro groups can exercise an activating influence.
The synthesis of the optical isomers of 3,5,5‐trimethylcyclohexyl mandelate (cyclandelate)
Authors: Ernsting M. J. E. , Nauta W. Th.
Published: September 2010

To investigate possible differences in spasmolytic activity the four isomers of cyclandelate (the DL‐mandelate of low melting 3,5,5‐trimethylcyclohexanol) as well as the corresponding isomeric esters from high melting 3,5,5‐trimethylcyclohexanol were prepared.
Investigations on organogermanium compounds I: On the redistribution reaction between tetra‐n‐butylgermanium and germanium tetrachloride
Authors: van der Kerk G. J. M. , Rijkens F. , Janssen M. J.
Published: September 2010

The redistribution reaction between tetra‐n‐butylgermanium and germanium tetrachloride has been investigated. Under suitable conditions it is possible to prepare tributylgermanium chloride and dibutylgermanium dichloride by this reaction in yields of over 80%. The presence of anhydrous aluminium chloride is required. The analogous preparation of butylgermanium trichloride in good yield has not been realized.

The relative reactivity of the compounds BunGeCl4‐n (n = 0, 1 or 2) with respect to alkylation by tetrabutylgermanium in the precence of aluminium trichloride was found to be Bu2GeCl2> BuGeCl3>> GeCl4.

The new compound butylgermanium trichloride is characterized.
Free‐radical reactions of allene the interaction of allene and thiyl radicals
Authors: van der Ploeg H. J. , Knotnerus J. , Bickel A. F.
Published: September 2010

The free‐radical addition of 1‐propanethiol, benzenethiol (thiophenol) and α‐toluenethiol (benzyl mercaptan) to allene in benzene solution has been investigated.

At high allene/thiol ratios the two sulfides resulting from the addition of one mole of RSH to allene (isopropenyl‐SR and allyl‐SR) are formed in yields of the same order of magnitude.

At low allene/thiol ratios the more reactive isopropenyl sulfide is not present among the products, since it is quantitatively converted into 1,2‐di‐SR‐propane. Thiol addition to the allyl sulfide to yield 1,3‐di‐SR‐propane is a much slower process.
A simple synthesis of some hydroxypyridine carboxylic acids
Authors: Broekman F. W. , van Veldhuizen A. , Janssen H.
Published: September 2010

A simple method for the synthesis of 3‐hydroxypicolinic acid and 4‐hydroxynicotinic acid via the cyano compounds starting from 3‐hydroxy‐2‐iodo‐ or 4‐hydroxy‐3‐iodopyridine, is described.
Studies on cyclohexane derivatives: IV Preparation and chemical proof of the configurations of the two 4‐isopropylcyclohexanecarboxylic acids
Authors: van Bekkum H. , Kleis A. A. B. , Medema D. , Verkade P. E. , Wepster B. M.
Published: September 2010

The preparation of pure low‐melting 4‐isopropylcyclohexanecarboxylic acid (m.p. 40–41°) is described for the first time. It was isolated from mixtures of the low‐melting and the high‐melting isomer, making use of the fact that only the latter gives an inclusion compound with thiourea.

By chemical means it is proved that low‐melting 4‐isopropylcyclohexanecarboxylic acid has the cis‐configuration and the high‐melting isomer the trans‐configuration. For this purpose these acids were converted into cis‐ and trans‐1‐methyl‐4‐isopropylcyclohexane (cis‐ and trans‐para‐menthane) respectively, using reactions which take place without any change of configuration at the cyclohexane nucleus. The configuration of these two hydrocarbons has been proved in paper III of this series.
Bromination of pyridine in fuming sulphuric acid
Authors: den hertog H. J. , van der Does L. , Landheer C. A.
Published: September 2010

When pyridine (4 moles) is heated at 130° in fuming sulphuric acid with bromine (1 mole), 1.6‐1.8 moles of pure 3‐bromopyridine are formed according to the equation 2 C5H5N + 2 SO3 + Br2 → 2 C5H4BrN + SO2 + H2SO4. The reaction product contains but a small amount of dibromopyridines (less than 0.1 mole), 2,5‐dibromopyridine being the chief component in the mixture.

The reaction products were analysed semiquantitatively by gas chromatography.
The thermal decarboxylation of alkali trichloroacetates in aprotic solvents IV decarboxylation in the presence of hexa‐ and pentachloroacetone
Authors: Wagner W. M. , Kloosterziel H. , Bickel A. F.
Published: September 2010

Thermal decarboxylation of sodium trichloroacetate in the presence of hexachloroacetone yields CO2, CO, CCl4, perchloroisopropenyl acetate and perchloroisopropenyl acrylate. A mechanism is suggested involving Cl+‐abstraction by a CCl3− ion from the ketone as the primary step, followed by Favorskii rearrangement of the resulting anion CCl3COCCl2.−

In the corresponding reaction of sodium trichloroacetate with pentachloroacetone both H+‐abstraction from the ‐CHCl2 group and Cl+ ‐abstraction from the ‐CCl3 group occur.
Some 1,2‐dihalogeno derivatives of cycloheptane and cyclo‐octane
Authors: Henniger P. W. , Wapenaar E. , Havinga E.
Published: September 2010

Cis‐1,2‐dibromocycloheptane and cis‐1,2‐dibromocyclo‐octane and the corresponding trans dibromo‐ and ‐dichloro compounds have been prepared. Dipole moments have been calculated from data on solutions of the compounds in benzene and in carbon tetrachloride. Infrared absorption spectra were taken from solutions in carbon disulphide. A short discussion is given comparing the results with those formerly obtained for the cyclohexane derivatives.
Investigations into the hydrogen bonding between n‐butanol and some ketones by infra‐red spectroscopy
Authors: Hoeke Miss M. , Koevoet A. L.
Published: September 2010

On considering the hydrogen bonding of n‐butanol with several ketones it appears that there is a regular increase in the value of the association constant on the introduction of methyl groups. Introduction of a phenyl group into a ketone brings about a decrease in hydrogen bonding. The cyclic ketones have high association constants, presumably due to their convenient structure for hydrogen bonding. An exception is formed by cyclopentanone, in which the sterical effect is counteracted by the larger double bond order of the >CO‐group. With sterically hindered molecules, such as di‐isopropyl ketone and di‐tert.‐butyl ketone there is less hydrogen bonding.

From the results of the experiments no conclusions, as to the existence of a simple relation between K on the one side and the half width v½ and the frequency‐shift Δv on the other, could be drawn.
Investigations on organotin compounds XVII: The structure of trialkyltin acylates
Authors: Janssen M. J. , Luijten J. G. A. , van der Kerk G. J. M.
Published: September 2010

By infrared spectroscopy it is shown that trialkyltin acylates in the solid state occur as coordination polymers in which each tin atom is penta‐coordinated,viz. by three alkyl groups and two oxygen atoms belonging to different acylate groups. In apolar solvents or in the liquid state, however, the compounds are monomolecular and show resemblance to organic esters. Only in very concentrated solution or just above the melting point is association detected. In a search for the generality of the concept it was found that the occurrence of the polymeric crystal structure is counteracted by steric hindrance, that it does not occur with thio‐ or dithio‐acetates and, finally, that lead behaves like tin but germanium and silicon compounds are monomolecular throughout.
Aromatic sulphonation V: A kinetic study on the sulphonation of toluene, ethylbenzene and isopropylbenzene in aqueous sulphuric acid
Authors: Kaandorp A. W. , Cerfontain H. , Sixma F. L. J.
Published: September 2010

Rate measurements have been made on the homogeneous sulphonation of toluene in aqueous sulphuric acid varying from 70.0 to 95.9 wt‐% at 5.0°, 25.0° and 45.0°. In addition, rate constants have been determined for the homogeneous sulphonation of ethylbenzene and isopropylbenzene at 25.0° in aqueous sulphuric acid solutions varying from 72.4 to 89.1 wt‐%. All reactions were found to be first order with respect to the aromatic compound. It is suggested that the differences in the overall rate constants for the sulphonation of toluene, ethylbenzene and isopropylbenzene originate predominantly from steric hindrance for ortho‐substitution.
Microbiological conversion of 19‐nortestosterone: (IV) 15α‐hydroxylation
Authors: de Flines J. , van der Waard W. F. , Mijs W. J. , Szpilfogel S. A.
Published: September 2010

Microbiological reaction of 19‐nortestosterone with Penicillium sp.ATCC 11598 leading to about equal amounts of the 15α‐hydroxy‐derivative and 15α‐hydroxy‐19‐nor‐androst‐4‐one‐3,17‐dione is described. Fermentation of 19‐nortestosterone with Fusarium orthoceras afforded mainly 15α‐hydroxy‐19‐norandrost‐4‐ene‐3,17‐dione and only minor amounts of 15α‐hydroxy‐19‐nortestosterone.