bluuebunny/crossref_metadata_2025_split huggingface dataset:
Über das Elektrische Potential von Oxidelektroden: I. Manganoxidelektroden
Authors: Drotschmann C. 
Published: September 2010

Abstract
Bei chemischem Abbau von rhombischem γ‐MnO2 ‐ besser η‐MnO2** ‐ ebenso wie von tetragonalem β‐MnO2 entsteht monokilines γ‐MnOOH. Das Ruhepotenital beider‐teilweise‐reduzierter Oxide sinkt mit sinkendem Sauerstoffgehalt. Der Potentialabfall ist nicht in rechnerischer Übereinstimmung mit dem Konzentrationsverhältnis [Mn4+]:[Mn3+] Vielmehr wird das Potential beeinflusst durch die Konzentration von Mn2+.
Die aus I Gramm‐Mol Braunstein maximal erhältliche Kapazität in Amperstunden ist abhängig von sekundären, nicht elektrochemisch wirksamen Reaktionen des primär gebildeten Mn2+ (Abdiffusion, chemisorptive oder chemische Bindung von Mn2+).
Das Braunsteinpotenital sowohl im Ruhezustand der Elektrode wie auch während elektrischer Entladungen gehorcht den Forderungen der Gleichung: e = e0 + RT/2F in (H+)4 ‐ RT/2F in (Mn2+)
Die Ansicht, dass konstante Ruhe‐Potentiale gemessen werden, wenn ein Oxid durch chemischen Abbau in eine niedrigere Oxidationsstufe in heterogener Phase umgewandelt wird, und dass mit sinkendem Oxidationsgrad sinkende Potentiale gemessen werden, wenn der Abbau in homogener Phase erfolgt, ist im Falle der Manganoxide, nicht bestätigt.
The chemistry of 3‐ketotetrahydrofurans I: Syntheses of 3‐ketotetrahydrofuran by oxidation
Authors: Weiland J. H. Sperna , Dijkstra H. , Pik A. B. 
Published: September 2010

Abstract3‐Ketotetrahydrofuran (II) has been obtained spectroscopically as well as gas‐chromatographically pure. A major modification in the dichromate‐sulphuric acid oxidation of the starting alcohol (I) has almost doubled the yield to 60%.The chromium trioxide‐pyridine oxidation of (I) is described for the first time and yields as high as 70% are obtained. The NMR spectrum of (II) is reported.
Stoichiometric considerations on the reaction between titanium trichloride and aluminum trimethyl
Authors: Miotto Mirella 
Published: September 2010

AbstractThe dependence of uptake of Al(CH3)3 by solid TiCl3 on the surface area of the latter has been studied. A “step reaction” technique permits the investigation of the stoichiometry of the reaction at different degrees of advancement, the amount of chlorine abstracted from the TiCl3 being taken as the advancement parameter.Methane evolution and aluminum and carbon fixation on the solid phase appear to be linearly related to this parameter and the slopes of the respective lines are taken as significant parameters from which the stoichiometry of the reaction is deduced.
The chemistry of cycloheptatriene: Part VIII: Transannular 1‐5 shifts of hydrogen in phenylcycloheptatriene
Authors: ter Borg A. P. , Kloosterziel H. 
Published: September 2010

Abstract7‐Phenylcycloheptatriene‐1,3,5 rearranges on heating to a mixture of the 3‐, 1‐ and 2‐isomers. These are formed in the order indicated by successive trans‐annular 1‐5 shifts of hydrogen. The isomerization of the 7‐ to the 3‐isomer, by which the trienic and aromatic systems enter into conjugation, is appreciably faster than the 1‐5 shift in cycloheptatriene itself. The interconversion of the 3‐ and 1‐isomers, however, proceeds at a rate comparable with that of the unsubstituted compound.The nature of the solvent has no influence on the rate of the 1‐5 shift.
Thiophen chemistry VIII: Michael Additions to 2(5H)‐thiophenone
Authors: Jakobsen Hans Jørgen , Larsen Ertk Holger , Lawesson Sven‐Olov 
Published: September 2010

Abstract2‐Hydroxythiophen exists at room temperature mainly in the tautomeric form 2(5H)‐thiophenone13 and is conveniently prepared3 by splitting 2‐thienyl t‐butyl ether by heating it with catalytic amounts of p‐toluenesulphonic acid at about 150°. 2(5H)‐Thiophenone, an α,β‐unsaturated cyclic thioester (thiolactone), has been shown to undergo Michael addition with different types of so‐called active methylene compounds.
An apparatus for the automatic recording of temperature‐time curves of condensed phases
Authors: Block R. , Mijlhoff F. C. 
Published: September 2010

AbstractIn studying transitions in condensed phases temperature‐time diagrams are frequently used. In this paper the principles for the construction of an apparatus for automatic recording of these diagrams using thermocouples are outlined. Temperature intervals and their initial points can be chosen at will; the lower limit of the interval depends only on the recorder‐sensitivity, and is in our case 6°. The diagram obtained is exactly interpretable in terms of thermal emf's. Constant specific heat of the sample is represented in the diagram by a line of constant slope.
Aromatic sulphonation VIII: Partial rate factors in the sulphonation of toluene with aqueous sulphuric acid
Authors: Cerfontain H. , Kaandorp A. W. , Vollbracht L. 
Published: September 2010

AbstractThe ratio of the overall rate constants for the sulphonation of toluene and benzene in aqueous sulphuric acid at 25° decreases from 110 to 25 on varying the acid concentration from 78 to 92 wt‐%. Similar trends are observed at 5° and 45°.The partial rate factors for ortho‐, meta‐ and para‐substitution in the sulphonation of toluene with aqueous sulphuric acid all decrease strongly with increasing acid concentration. The partial rate factor for para‐substitution is temperature independent, indicating a negligible difference in activation enthalpy between substitution at the para‐position in toluene and at a single position in benzene. The corresponding difference in activation entropies is 7 ± 2 cal · deg−1 · mole−1.The latter difference is ascribed to differences in solvation of the starting hydrocarbons or/and of the transition states. These differences in solvation may also be responsible for the small but apparent deviations from the Selectivity Relationship observed in the present study. It is suggested that the sulphonation of toluene and benzene in aqueous sulphuric acid proceeds via a Wheland type of intermediate.
Usefulness of the phthalimidomethyl group for the reversible protection of carboxyl functions
Authors: Nefkens G. H. L. , Tesser G. I. , Nivard R. J. F. 
Published: September 2010

AbstractThe stability of the ester bond in phthalimidomethyl benzoate has been tested under a wide variety of circumstances, applied for the removal of protecting groups from amino acids. The chemical properties of the ester (table I) warranted the expectation that the phthalimidomethyl group would be useful for the protection of carboxyl functions in peptide syntheses.Several amino acid esters of phthalimidomethanol (table III) have been prepared by simple methods. Some of these compounds have been converted into peptides by conventional routes (table IV). No racemization was observed during these reactions.The usefulness of the phthalimidomethyl esters in peptide syntheses has been investigated further with amino acid and peptide esters containing also amino or other carboxyl protecting groups (benzyloxycarbonyl, benzyl, p‐nitrobenzyl or tert.‐butyl). In all cases the phthalimidomethyl group as well as the other substituents could be removed separately and very specifically, giving pure products in satisfactory or good yields (see e.g. schemes A and B).
Equilibration of benzene derivatives: Part I. Bromobenzenes
Authors: Augustijn G. J. P. , Kooyman E. C. , Louw R. 
Published: September 2010

AbstractRelative rates of aluminium bromide catalyzed debromination of bromobenzenes have been determined by competition runs at room temperature. Ortho‐halo‐substituents have an accelerating effect; the influence of m‐ and p‐substituents is also different from that observed in electrophilic substitutions.Isomer equilibria among halo‐bromobenzenes showed low proportions of ortho‐isomers (5‐6%) and meta/para ratios of about 1.7‐2.0; with alkyl‐bromobenzenes, appreciable proportions of ortho‐isomers were found. This difference is attributed to dipole interactions having opposite signs in the two cases. Equilibrium patterns for disubstituted bromobenzenes agreed with isomer distributions computed from mono‐substituted bromobenzenes on the basis of additivity; steric effects may cause deviations, e.g. in the bromo‐ortho‐xylenes.Equilibrium constants for exchange reactions PhZ + PhBr⇄BrPhZ + PhH were found to be 1.45, 1, 0.055, 0.10 and 0.075 for Z = CH3, H, Br, Cl and F, respectively. Combination of these constants with the isomer distributions leads to “partial equilibrium factors” for the exchange of a bromine and a hydrogen atom at a given position in a substituted benzene relative to benzene.
The photo‐oxidation of nylon 6 and 66
Authors: Kroes G. H. 
Published: September 2010

AbstractOn the basis of experimental results published earlier1 and data from the literature2, an extension of the complex of reactions taking place in the photooxidation of polyamides is proposed.It is shown that after the completion of a chain break, at least one of the ends formed is shortened step by step until suitable conditions for termination are present. In this connection the availability of oxygen as well as the relative immobility of the activated ends are of importance.
Syntheses of the isomeric amino‐ and bromo‐1,5‐naphthyridines
Authors: Czuba W. 
Published: September 2010

AbstractSyntheses of the three isomeric bromo‐1,5‐naphthyridines from 2‐hydroxy‐1,5‐naphthyridine, 3‐amino‐5‐bromopyridine (Skraup‐synthesis) and 4‐hydroxy‐1,5‐naphthyridine are described.New methods for the preparation of 2‐ and 3‐amino‐1,5‐naphthyridine are given.Some physical and chemical properties (inter alia the infrared spectra) of the substances investigated have been established.
Rearrangements during aminations of bromo‐1,5‐naphthyridines, probably involving a naphthyridyne as an intermediate
Authors: Czuba W. 
Published: September 2010

AbstractWhen reacted with potassium amide in liquid ammonia both 3‐bromo‐and 4‐bromo‐1,5‐naphthyridine are converted into a mixture containing 3‐amino‐ and 4‐amino‐1,5‐naphthyridine. The course of these reactions can be explained by a mechanism involving 1,5‐naphthyridyne‐3,4 as an intermediate.An abnormal reaction takes place during the aminations of 2‐bromo‐1,5‐naphthyridine, a compound, C8H8N4, together with the chief product 2‐amino‐1,5‐naphthyridine and 1,5‐naphthyridine being formed.In the case of 3‐bromo‐2‐ethoxy‐1,5‐naphthyridine an amination reaction afforded only 3‐amino‐2‐ethoxy‐1,5‐naphthyridine. Syntheses of 3‐bromo‐2‐ethoxy‐1,5‐naphthyridine and 3‐amino‐2‐ethoxy‐1,5‐naphthyridine are described.
9‐pyridylidenefluorenes, a new class of anti‐inflammatory substances
Authors: Buu‐Hoï N. P. , Delbarre F. , Jacquignon P. , Brouilhet H. , Rose A. , Sabathier J. F. , Sinh M. P. 
Published: September 2010

AbstractThe condensation of fluorene with the three formylpyridines and 2‐formyl‐6‐methylpyridine has been investigated, and the 9‐pyridylidenefluorenes obtained have been tested in rats for anti‐inflammatory activity. 9‐(3‐Pyridylidene)fluorene proved the most potent compound, with an activity half of that of subcutaneously injected prednisone, in an oral dose ten times greater.
Investigations on sterols XXI: An alternative route for the synthesis of some 6‐dehydro‐9β,10α‐steroid hormone analogues
Authors: Smit A. , Westerhof P. 
Published: September 2010

AbstractSelective ozonisation of isolumisterone produced 9β,10α‐bisnorchola‐4,6‐dien‐3‐on‐22‐al. This compound could be converted into: 6‐dehydro‐9β,10α‐progesterone (9β,10α‐pregna‐4,6‐diene‐3,20‐dione); 6‐dehydro‐17α‐hydroxy‐9β,10α‐progesterone (9β,10α‐pregna‐4,6‐dien‐17α‐ol‐3,20‐dione) and 6‐dehydro‐9β,10α‐testosterone (9β,10α‐androsta‐4,6‐dien‐17β‐ol‐3‐one).
Hetarynes VI: Amination of bromoethoxypyridines
Authors: den Hertog H. J. , Pieterse M. J. , Buurman D. J. 
Published: September 2010

AbstractAminations of 2‐bromo‐3‐ethoxy‐, 2‐bromo‐4‐ethoxy‐, 2‐bromo‐5‐ethoxy‐, 3‐bromo‐2‐ethoxy‐ and 4‐bromo‐2‐ethoxy‐pyridine with potassium amide in liquid ammonia are described.A survey is given of the behaviour of the 10 isomeric bromoethoxypyridines towards this reagent.
The chemistry of 3‐ketotetrahydrofurans II: The cyclization of 2‐alkoxyethyl diazomethyl ketones
Authors: Weiland J. H. Sperna 
Published: September 2010

AbstractRing closure of 2‐alkoxyethyl diazomethyl ketones (VII) under the influence of a catalytic amount of hydrochloric acid gives 3‐ketotetrahydrofuran (VIII). The yields obtained in this reaction are greatly influenced by the choice of the alkoxy group. 3‐Ketotetrahydrothiophen (XX) is prepared from 2‐tert.butylthioethyl diazomethyl ketone (XIXa) by the same procedure.
Determination of molecular weights by means of thermoelectric vapour phase osmometry
Authors: van Dam J. 
Published: September 2010

AbstractA description is given of a thermoelectric vapour phase osmometer for the determination of molecular weights or, more generally, of the osmotic activity of solutions. In this instrument the vapour pressure difference between a solution of the substance under investigation and the pure solvent is converted into a temperature difference between the junctions of one or more thermocouples. From a detailed consideration of the heat and mass transfer in the steady state, the temperature difference can be calculated. The theory is fully corroborated by some experiments on solutions in benzene and water of substances of known molecular weights. Finally, an application of the method to the determination of the molecular weights of some polystyrene samples, ranging between 3 000 and 14000, is discussed. The upper limit lies around 30 000 with an accuracy of about 10%.
Synthèse et propriestes physiques des tétraalcoylméthanes en C17
Authors: Maire Jean‐Claude , Desgrandchamps Guy 
Published: September 2010

AbstractLa synthèse des tétraalcoylméthanes en C17 a été effectuée suivant une méthode basée sur une synthèse de Knoevenaegel. Les courbes viscositè‐température des hydrocarbures obtenus ont été tracées entre 20 et 120° et l'allure des courbes confrontée avec les formules proposées par: Andrade et Sheppard, Walther, Hugel et Watermann. Entre deux températures dont la différence est inférieure α 40°, l'écart relatif entre les valeurs mesurées et les valeurs calculées par interpolation α l'aide des trois dernières formules n'excède pas un pourcent.
Untersuchungen über N‐Oxyde des 2‐Dimethylaminopyridins: (die Nitrierung des N1‐oxyde des 2‐Dimethylaminopyridins)
Authors: Wieczorek J. S. , Płazek E. 
Published: September 2010

AbstractBei der Einwirkung von Peressigsäure auf 2‐Dimethylaminopyridin entsteht ein N‐Oxyd welches von dem N1‐Oxyd, das aus dem N‐Oxyd des 2‐Chloropyridin durch Aminolyse erhalten worden ist, verschieden ist; das Sauerstoffatom in der neuen Verbindung befindet sich offenbar am Stickstoff der Dimethylaminogruppe (N2‐Oxyd). Bei der Nitrierung des bekannten N1‐Oxydes entsteht ein N1‐Oxyd des 2‐Dimethylamino‐5‐nitropyridins. Mehrere Derivate der letzten Verbindung, darunter das Reduktionsprodukt: das N1‐Oxyd des 5‐Amino‐2‐dimethylamino‐pyridins sind dargestellt worden.
Phosphatidic acids and derivatives XII: Synthesis of bis‐β‐glycerophosphatidic acids starting from αγ‐diglycerides with one or two saturated component acids
Authors: van Gijzen J. , Hoefnagel M. A. , Verkade P. E. 
Published: September 2010

AbstractA method is described for the preparation of bis‐β‐glycerophosphatidic acids starting from αγ‐diglycerides with one or two saturated component acids.
Structure of 2,4,6‐trialkylsubstituted 1,3,5‐trioxans
Authors: Barón Máximo , Hollis Donald P. 
Published: September 2010

AbstractThe structure of several 2,4,6‐trisubstituted 1,3,5‐trioxans has been studied by N.M.R. and the dipole moment of α‐parabutylchloral has been measured in solution. All compounds were found to be in the chair conformation.
On the ozonolysis of indane and tetralin as well as some dimethyl homologues in connection with the reactivity of the bonds in the ring system: (with reference to the so‐called Mills‐Nixon effect)
Authors: de Jong F. P. K. , Wibaut J. P. 
Published: September 2010

AbstractIn the ozonolysis of 4,7‐dimethylindane the aliphatic dicarbonyl compounds methylglyoxal and glyoxal are formed in a combined yield of 0.1 mol of dicarbonyl compound per mol of dimethylindane. The molecular ratio glyoxal: methylglyoxal is 1.57: 1.In the ozonolysis of 5,6‐dimethylindane the aliphatic dicarbonyl compounds methylglyoxal and dimethylglyoxal (diacetyl) are formed in a combined yield of 0.05 mol per mol of dimethylindane. The molecular ratio diacetyl: methylglyoxal is 3.5: 1.From the above it follows that each of the six carbon‐carbon bonds of the aromatic six‐membered ring in 4,7‐ and 5,6‐dimethylindane respectively can react with ozone. There is no question of a “fixation” of the double bonds in the aromatic six‐membered ring. From the molecular proportion of the dicarbonyl compounds it follows that during the action of ozone on 4,7‐ and 5,6‐dimethylindane respectively there is a marked preference for the attack of the common carbon‐carbon bond of the ring system. This common carbon‐carbon bond displays towards ozone a stronger double‐bond character than do the adjacent carbon‐carbon bonds in the aromatic ring. This result is contrary to the theory ofMillsandNixon, but is qualitatively in agreement with the calculations ofLonguett‐HigginsandCoulson.In the ozonolysis of 5,8‐dimethyltetralin the aliphatic dicarbonyl compounds glyoxal and methylglyoxal are formed in a combined yield of 0.07 mol per mol of dimethyltetralin. The molecular ratio methylglyoxal: glyoxal is about 3: 1. In the ozonolysis of 6,7‐dimethyltetralin the aliphatic dicarbonyl compounds methylglyoxal and dimethylglyoxal are formed in a combined yield of 0.09 mol per mol of dimethyltetralin. The molecular ratio methylglyoxal: dimethylglyoxal is 1.1: 1.From these findings it follows that each of the six carbon‐carbon bonds of the aromatic six‐membered ring in 5,8‐ or 6,7‐dimethyltetralin can react with ozone.There is no marked preference for the attack of the common carbon‐carbon bond, as compared with the attack of the adjacent carbon‐carbon bonds in the aromatic six‐membered ring. This result is contrary to the theory ofMillsandNixon.To check the analytic method used by us, we examined the ozonolysis of p‐xylene and of 1,2,4,5‐tetramethylbenzene (durene).In the ozonolysis of p‐xylene, methylglyoxal and glyoxal are expected to be formed in the molecular ratio 2: 1; the proportion found was 2.15: 1.In the ozonolysis of durene, methylglyoxal and dimethylglyoxal are expected to be formed in the molecular ratio 2: 1; the proportion found was 1.93: 1.
Chemistry of acetylenic ethers 73: Alkali amide cleavage of allenyl thioethers
Authors: Montijn P. P. , Brandsma L. 
Published: September 2010

AbstractAllenyl thioethers of the type CH3CHC (R = alkyl) have been converted in very good yield into 1,3‐enynes HCC‐CHCH‐R (IV) on treatment with two equivalents of alkali amide in liquid ammonia, followed by hydrolysis of the reaction mixture.
The alkylation of phenol with isobutene
Authors: de Jong J. I. 
Published: September 2010

AbstractSome aspects of the alkylation of phenol with isobutene using small quantities of sulfuric acid as a catalyst are discussed. It is shown that initially ortho and para substitution take place to roughly the same extent. In the course of the reaction the isomer distribution changes in favour of the para isomer, the alkylation being reversible. Equilibrium constants were determined in the temperature range of 50‐125°.
Oxidative rearrangement of trismethylene‐trinitrobenzene: Nucleophilic aromatic addition VI
Authors: de Boer Th. J. , van Velzen J. C. 
Published: September 2010

AbstractTrismethylene‐trinitrobenzene I undergoes ring contraction when oxidised under mild, alkaline conditions to give stereoisomeric hydroxy‐acids IVa and IVb. Both isomers yield the same cyclic ketone V when oxidatively decarboxylated. This ketone can be subjected to a similar rearrangement as I by successive treatment with selenium dioxide and copper sulphate in pyridine, resulting in another pair of stereoisomeric hydroxy‐acids, VIIIa and VIIIb. Both these isomers are oxidatively decarboxylated to the cyclic ketone IX. V and IX, both α‐nitro‐ketones, undergo ring fission with alkali. The resulting carboxylic acids are identical with acids obtained previously from I by different routes.
Degradative iodination of thioanisole
Authors: van der Veen J. , Stevens W. 
Published: September 2010

AbstractDegradative halogenation of thioanisole by iodine at temperatures between 100° and 150° was found to produce diphenyl sulfide, diphenyl disulfide, thianthrene and trimethylsulfonium iodide together with small amounts of hydrogen sulfide, hydrogen iodide, methyl iodide and dimethyl sulfide. Diphenyl sulfide and thianthrene did not react with iodine under analogous conditions. Diphenyl disulfide, on the other hand, reacted with iodine to yield diphenyl sulfide, thianthrene and hydrogen sulfide.A thin‐layer chromatographic method was developed in order to identify thioanisole, diphenyl sulfide, diphenyl disulfide and thianthrene in the reaction mixtures obtained.
Aromatic sulfonation X: Determination of the kinetic isotope effect of hydrogen in the sulfonation and sulfonylation of benzene remarks on hydrogen exchange between benzene and benzenesulfonic acid
Authors: Cerfontain H. , Hofman H. J. , Telder A. 
Published: September 2010

AbstractThe kinetic isotope effect of hydrogen for sulfonation with sulfur trioxide has been determined at 25.0° in a competitive study, using hexadeuterated and ordinary benzene, askH/kD= 1.14 ± 0.06. Hydrogen exchange between benzene and benzenesulfonic acid is relativelys slow under these conditions and does not interfere with the determination of the isotope effect.Diphenylsulfone was found as a by‐product in the sulfonation reaction. The kinetic isotope effect for the sulfonylation of benzene at 25.0° was found to bekH/kD= 0.86 ± 0.06.It is proposed that the hydrogen exchange between benzene and anhydrous benzenesulfonic acid proceeds according to a SE‐2 type of mechanism.
Investigations on sterols XXII. The synthesis of 4‐H3‐9β,10α‐progesterone and 4‐H3‐6‐dehydro‐9β,10α‐progesterone
Authors: van Kamp H. , Westerhof P. , Niewind H. 
Published: September 2010

AbstractThe synthesis is described of 9β,10α‐progesterone and of 6‐dehydro‐9β,10α‐progesterone and of 6‐dehydro–β,10α‐progesterone both tritiated at C4.
Studies on vitamin D and related compounds XVII: The photo‐formation of lumisterol
Authors: Sanders Georgine M. , Havinga E. 
Published: September 2010

AbstractA further investigation has been made of the pathway of the photo‐formation of lumisterol, which had remained doubtful after the previous analyses of irradiation mixtures, in which lumisterol was determined indirectly3. Experiments using tachysterol3‐7‐3H reveal that lumisterol is not formed directly from tachysterol to a significant extent. Thin layer chromatograms of mixtures obtained after various times of irradiation starting with solutions of pre‐calciferol3 and tachysterol3 indicate the direct formation of lumisterol3 from precalciferol3. The modified scheme of interrelationships between pro‐ and pre‐vitamin D, lumisterol and tachysterol is essentially the one originally postulated by Velluz, Amiard and Goffinet11. The question whether ergosterol and tachysterol yield other photo‐products besides precalciferol remains to be investigated.
Note on the isolation of β‐hydroxypalmitic acid from the extracellular lipids of: Rhodotorula Glutinis
Authors: van Ammers M. , Deinema Maria H. , Landheer C. A. , van Rooyen Margaretha H. M. 
Published: September 2010

AbstractFrom the extracellular lipids produced by Rhodotorula Glutinis, β‐hydroxy‐palmitic acid was isolated. The structure of this acid was established by NMR and confirmed by synthesis.