bluuebunny/crossref_metadata_2025_split huggingface dataset:
The chemistry of cycloheptatriene: Part VII: Thermal isomerization of 7‐deuterocycloheptatriene by trans‐annular 1‐5 shifts of hydrogen
Authors: ter Borg A. P. , Kloosterziel H. , van Meurs N. 
Published: September 2010

Abstract7‐Deuterocycloheptatriene ‐ prepared from tropylium bromide and lithium aluminium deuteride in 94% isotopic purity ‐ rearranges on heating at 100‐140°. Mass spectrometry and proton magnetic resonance (NMR) spectroscopy showed that by an intramolecular process a mixture of the 7‐, α‐, β‐ and γ‐monodeuterocycloheptatrienes is formed. The changes in shape and intensity of the NMR signals proved that these isomers arise in successive steps, each of which involves a trans‐annular 1‐5 shift of hydrogen, combined with a shift of two double bonds. The Arrhenius parameters of the shift are E = 31‐32 kcal/mole and log A (s−1) = 10.9‐11.5. In transition‐state theory this corresponds with an appreciable negative entropy of activation, indicating a rigid transition state.A number of known isomerizations in 7‐membered ring systems, particularly those of the Buchner esters and acids, can be explained by a trans‐annular 1‐5 shift.
Studies in the zinc reduction series: The reduction of certain 2‐benzoylbenzoic acids and esters
Authors: Risinger Gerald E. , Thompson James A. 
Published: September 2010

AbstractThe reaction mechanism of the reduction o certain 2‐benzoylbenzoic acids and esters is discussed. It is suggested that the carboxyl group directs product formation either by neighboring group participation or by facilitating the hydrogenolysis of the carbinol group. Furthermore, it is concluded that the intermediate in the reduction of the esters does not contain a carbinol group.
A study of the polarographic reduction of the acridizinium and phenanthridizinium ions
Authors: Frost Jackie G. , Saylor John H. 
Published: September 2010

AbstractThe properties of acridizinium and phenanthridizinium at the dropping mercury electrode have been investigated, and a mechanism for reduction is proposed. Acridizinium is reduced in two one‐electron stages at potentials of −0.807 volts and −1.022 volts in acid and neutral solutions, these values being independent of pH. In basic solution, these two reduction steps disappear and two other waves appear at potentials of approximately −1.5 volts and −2.1 volts (vs. saturated calomel electrode). This change in polarographic behavior has been linked with “pseudo‐base” formation. Phenanthridizinium is reduced in a single two‐electron step with a measured half‐wave potential of −1.202 volts. The reduction potential is independent of pH.
Addition of carbonyl compounds to alkynes under the influence of boron trifluoride
Authors: Bos H. J. T. , Arens J. F. 
Published: September 2010

Abstractα,β‐Unsaturated ketones are formed by reaction of aldehydes and ketones with phenylethyne under the influence of boron trifluoride. When using aromatic aldehydes 2,4,6‐triarylpyrylium tetrafluoroborates are formed as by‐products. trans‐2,3‐Diphenylindane‐1‐one is obtained from 1,2‐diphenylethyne and benzal‐dehyde.
Mechanism of reactions of unsaturated ethers and thioethers XIII: Reaction of 1‐ethoxy‐1‐alkynes with carboxylic acids in non‐aqueous solvents
Authors: Zwanenburg B. , Drenth W. 
Published: September 2010

AbstractThe reaction between 1‐ethoxy‐1‐alkynes and carboxylic acids has been studied in non‐aqueous solvents. The first stage of this reaction, the formation of 1‐ethoxyvinyl esters, is described in this paper. The kinetics of the reaction in benzene follow the rate equationv = k03·C1‐alkynyl ether·C2acidwhereas in dioxan and sulpholane the equationv = (k03·C2acid + k4·C3acid) C1‐alkynyl etheris obeyed. A considerable rate increase was observed on varying the solvent from dioxan to sulpholane, while the rate in benzene is approximately equal to that in sulpholane. From measurements on the reaction of ethoxyethyne and either normal or O‐deuteroacetic acid in benzene a kinetic isotope effect, kH/kD, of 3.1 was observed. In sulpholane as solvent kH/kD was equal to 2.8. Infrared spectra of reaction mixtures of ethoxyethyne and O‐deuteroacetic acid showed that no incorporation of deuterium into ethoxyethyne occurred during reaction in benzene and sulpholane, whereas it did occur in dioxan. The effect of added tetrabutylammonium perchlorate on the rate of reaction of ethoxyethyne and chloroacetic acid in dioxan was also studied. The rates of a number of 1‐alkynyl ethers were correlated with a Taft‐equation.It was concluded that proton transfer occurs in the rate determining step in which an ion pair is formed. Before protonation the substrate is solvated by acid molecules in a number of pre‐equilibria.
Total synthesis of aza‐steroids I: d,l‐N‐Tosyl‐6‐aza‐8,14‐bisdehydroestrone methyl ether and d,l‐N‐tosyl‐6‐aza‐8,14‐bisdehydro‐D‐homoestrone methyl ether
Authors: Huisman H. O. , Speckamp W. N. , Pandit U. K. 
Published: September 2010

AbstractA three step synthesis of the key intermediate (IV) for the total synthesis of 6‐aza‐19‐norsteroids is described.
Physical properties of organic thiones: Part V. Effect of substituents with thiocarbonyl functions on acid strength
Authors: Janssen M. J. 
Published: September 2010

AbstractThe acid dissociation constants of a number of substituted acetic acids were determined. Compounds were of the general type AC = X—BCH2COOH with A methyl, alkoxy, alkylthio or dimethylamino, X oxygen or sulphur, B oxygen, sulphur or nitrogen. The influence of the substituent AC(X)B upon the acidity is related to electronic (mesomeric and inductive) effects. In one instance complication by steric effects arises. The main results support the model, previously conceived for thiones with heteroatoms attached to the thiocarbonyl group: extensive mesomeric electron displacements together with appreciable contributions from inductive shifts, the latter especially noteworthy, where sulphur is concerned. In the molecules studied the thiocarbonyl group is more electron‐attracting than the carbonyl group.
Synthesis of arachidonic acid and related higher unsaturated compounds
Authors: van der Steen D. , Pabon H. J. J. , van Dorp D. A. 
Published: September 2010

AbstractThe usefulness of hexa‐2,5‐diyn‐1‐ol as an intermediate in the synthesis of arachidonic acid, poly‐yn alcohols and docosa‐4,7,10,13,16,19‐hexaynoic acid is demonstrated. Difficulties in the partial reduction of the latter product to the corresponding all cis‐hexaenoic acid are described.
The conformation of the red form of 2,2′‐methylenediquinoline
Authors: van Thuijl J. , Romers C. , Havinga E. 
Published: September 2010

AbstractThe studies by Scheibe and his coworkers revealed that the conformation of the red form of 2,2′‐methylenediquinoline (I) is di‐cis. This paper reports a direct proof of the conformation of the red form of 8‐bromo‐2,2′‐methylenediquinoline (III) by X‐ray analysis.
Chemistry of acetylenic ethers, 67: Allenyl thioethers from alkynyl thioethers
Authors: Brandsma L. , Wijers H. E. , Arens J. F. 
Published: September 2010

AbstractThe isomeric allenyl thioethers, III, are produced in good yield by treating 1‐ethylthio‐1‐alkynes, I, with an equivalent amount of sodamide in liquid ammonia, followed by hydrolysis of the reaction mixture.The corresponding allenyl thioethers alkylated in the 1‐position, IV, are obtained, also in good yield, by adding primary or secondary alkyl halides to the reaction product of sodamide and 1‐ethylthio‐1‐alkynes, I.
Investigations into the conformation of non‐aromatic ring‐compounds X: The crystal structure of trans‐2,3‐dibromo‐1,4‐dioxan at −100°
Authors: Altona C. , Knobler Carolyn , Romers C. 
Published: September 2010

Abstracttrans‐2,3‐Dibromo‐1,4‐dioxan crystallizes in the orthorhombic system, space group P212121, Z = 4, with cell dimensions: a = 5.685, b = 7.59, c = 15.82 Å at −100°.The structure was refined in two centrosymmetric projections by means of reflexion data obtained at −100° using copper radiation. The dioxan ring has the chair conformation; the bromine atoms occupy axial positions.
Chemistry of acetylenic ethers 69: A new synthesis of di‐(alk‐1‐ynyl) thioethers
Authors: Brandsma L. 
Published: September 2010

AbstractDi‐(alk‐1‐ynyl) thioethers IV have been prepared from 2,2′‐dichlorodivinyl thioether II by converting this compound into metallated diethynyl thioether by means of four equivalents of sodamide in liquid ammonia, followed by alkylation. The starting material II was obtained in a high yield by partial dehydrochlorination of the adduct I from vinyl chloride and sulphur dichloride. The overall yields are very satisfactory.
Gas phase pyrolysis of alkyl acetates
Authors: Scheer J. C. , Kooyman E. C. , Sixma F. L. J. 
Published: September 2010

AbstractAn investigation was made into the thermal decomposition of twenty‐seven aliphatic acetates, using a micro‐scale flow reactor connected to a gas chromatograph. The rate of elimination increases markedly as the degree of alkylation of the α‐carbon atom becomes higher. The accelerating effect of β‐alkyl substituents on the rate of elimination is small, as compared with that of α‐alkyl substituents. The reactivity of the aliphatic acetates approaches a limiting value as the carbon chain is extended. The reactivity decreases on the introduction at the β‐carbon atom of an electron‐attracting group and increases on the introduction of an electron‐releasing group. A tentative mechanism is proposed which is based on the reversible formation of an ion‐pair.
The chemistry of cycloheptatriene: Part IX: Thermal interconversion of 2,7‐ and 2,3‐dihydrotropone by transannular 1‐5 shifts of hydrogen
Authors: ter Borg A. P. , Kloosterziel H. 
Published: September 2010

Abstract2,7‐Dihydrotropone upon heating at 60‐100deg; isomerizes (partly) to the 2,3‐isomer. Kinetic data: order of the reaction, influence of solvent and entropy of activation, point to a mechanism involving an intramolecular 1‐5 shift of hydrogen in this cycloheptadiene derivative.
Investigations on syntheses “under physiological conditions”: I. Comparison of the behaviour of ammonia and methylamine as one of the reaction components
Authors: Beyerman H. C. , Enthoven P. H. , Verkade P. E. 
Published: September 2010

AbstractThe behaviour of the following six combinations of compounds has been studied “under physiological conditions”: glutaraldehyde or succinaldehyde, methylamine or ammonia, acetonedicarboxylic acid or diethyl acetonedicarboxylate. The pH was maintained at 3, 5, 7, 10 or 13; the other experimental conditions were the same in the series with acetonedicarboxylic acid and in those with diethyl acetonedicarboxylate as reaction component. The yield of reaction product was in each case determined carefully.Ammonia proved to be well suited as reaction component in these Schöpf syntheses. The relation between the pH and the yield of reaction product in the six cases was discussed in detail; ammonia and methylamine proved to behave in the same way.
Pyrones et Pyronones. I. Carboxy‐3 phényl‐6 pyrone‐2 et carboxy‐6 phényl‐3 pyrone‐2
Authors: van Dam Mathieu J. D. 
Published: September 2010

Abstract6‐Phenyl‐2‐pyrone‐3‐carboxylic acid has been prepared by acid hydrolysis of its ethyl ester and by the action of sulfuric acid on its isomer, 2‐carboxy‐5‐phenyl‐2‐penten‐4‐yn‐1‐oic acid. The distinction between these two isomers and a third, 2‐carboxy‐5‐phenyl‐2,4‐pentadien‐(1,4)olide, is set forth. A fourth isomer, 3‐phenyl‐2‐pyrone‐6‐carboxylic acid, has been synthesized by acid hydrolysis and cyclization of diethyl 2‐hydroxy‐5‐phenylmuconate.
Pyrones et Pyronones. II Synthèse d'alcoyl‐6 pyrones‐2 par réduction d'alcoyl‐6 pyronones
Authors: van Dam M. J. D. , Kögl F. 
Published: September 2010

By reaction of triacetic lactone with phosphoryl chloride 4‐chloro‐6‐methyl‐2‐pyrone was prepared; this happened to be identical with a compound of uncertain structure, previously obtained from acetyl chloride and 1,1‐dichloroethene. Reductive dechlorination yielded 6‐methyl‐2‐pyrone.Both 6‐cyclopentyl‐3‐cyclopentylcarbonyl‐4‐hydroxy‐2‐pyrone and 6‐cyclopentyl‐4‐hydroxy‐2‐pyrone were prepared by conventional methods; they have bacteriostatic properties. By chlorination and reduction of the latter compound 6‐cyclopentyl‐2‐pyrone was obtained.The mechanism of these substitution reactions is discussed.
Investigations on selective bromination of tertiary hydrogen atoms in alicyclic compounds
Authors: Siegmann R. H. , Beers M. J. , Huisman H. O. 
Published: September 2010

AbstractInvestigations are described on selective bromination of tertiary hydrogen atoms in alicyclic compounds by radical halogenation with molecular bromine.Isopropylcyclopentane, isopropylcyclohexane, bicyclopentyl and bicyclohexyl have been chosen as simple model systems.From the first two compounds the corresponding di‐tertiary 1,6‐dibromoisopropylcyclopentane and 1,7‐dibromoisopropylcyclohexane, respectively, were obtained in good yields.The structure of both these substances has been elucidated by degradation reactions as well as by independent syntheses; N.M.R.‐spectra also provide confirmatory evidence for the structures assigned to the di‐tertiary dibromo compounds.The tertiary hydrogen atoms in bicyclopentyl and bicyclohexyl cannot be brominated selectively; in both cases higher brominated compounds are obtained as the main products.
Alkaloids in Pausinystalia yohimbe (K.Schum.) ex pierre: Part I. The paper‐chromatographic identification of alkaloids occurring in some yohimbine‐containing barks
Authors: van der Meulen Th. Hajonides , van der Kerk G. J. M. 
Published: September 2010

AbstractThe simultaneous use of two solvent systems allows of an easy chromatographical identification of yohimbine and a number of related alkaloids in extracts from several yohimbine‐containing barks. By using these solvent systems the occurrence of two unknown alkaloids was demonstrated.
Alkaloids in Pausinystalia yohimbe (K.Schum.) ex pierre: Part III. The structure of a new alkaloid
Authors: van der Meulen Th. Hajonides , van der Kerk G. J. M. 
Published: September 2010

AbstractThe structure has been determined of a new alkaloid isolated from barks of Pausinystalia yohimbe. The compound is tetrahydro‐desmethyl‐corynantheine. Stereochemically it can be related to tetrahydro‐desmethoxy‐corynantheine alcohol, a compound described earlier by Karrer et al.
Applications of proton resonance spectroscopy to structural problems: Part X. Disulphonyl derivatives of 2‐Aminopyridine
Authors: Bedford G. R. , Dorn H. , Hilgetag G. , Katritzky A. R. 
Published: September 2010

AbstractProton resonance distinguishes clearly disulphonyl derivatives of 2‐aminopyridine which are derived from (a) the amino and (b) the imino form.
Aromatic sulphonation IXheterogeneous sulphonation of toluene with aqueous sulphuric acid
Authors: Cerfontain H. , Sixma F. L. J. , Vollbracht L. 
Published: September 2010

AbstractThe heterogeneous sulphonation of toluene with 81.9 and 95.9 wt‐% aqueous sulphuric acid has been studied at 25°. The isomer distribution which deviates from that observed in homogeneous sulphonation, varies with toluene conversion and with toluene to sulphuric acid volume ratio. The content of p‐toluenesulphonic acid is higher under heterogeneous conditions than under homogeneous conditions. It is suggested that the variation in isomer distribution is due chiefly to the presence of increasing amounts of sulphonic acids in the sulphuric acid phase.The heterogeneous sulphonation of toluene proceeds mainly in the sulphuric acid phase. Some sulphonation in the toluene phase by sulphur trioxide may take place as well. However, the latter process is of little ‐ if any ‐ importance.
The mechanism of the aluminium bromide catalyzed isomerization of n‐propyl bromide
Authors: Douwes H. S. A. , Kooyman E. C. 
Published: September 2010

Abstractn‐Propyl bromide is readily isomerized to isopropyl bromide in carbon disulphide solution under the influence of aluminium bromide at ‐20°. The reaction may be followed by infrared spectroscopy or by gas‐liquid chromatography. Rate data can be accommodated only by using two kinetic equations, obtaining at high and low molar intake ratios of the reactants, respectively.No incorporation of deuterium takes place when carrying out the reaction in the presence of deuterium bromide, indicating that the isomerization does not involve reversible dehydrobromination.Runs with 2‐deuterated n‐propyl bromide show a significant isotope effect, a hydrogen atom shifting about 3.4 times more rapidly than a deuterium atom.These and other results obtained may be interpreted in terms of reversible (partial) ionization, followed by a 1,2‐hydrogen shift.
Reactions of aliphatic halides with solutions of alkali metals in liquid ammonia: III. The reduction of optically active 6‐chloro‐2,6‐dimethyloctane to the corresponding hydrocarbon
Authors: Verkade P. E. , de Vries K. S. , Wepster B. M. 
Published: September 2010

AbstractThe reduction of optically active 6‐chloro‐2,6‐dimethyloctane to 2,6‐dimethyloctane by a solution of an alkali metal in liquid ammonia proceeds with predominating retention of configuration. It is concluded that the reaction proceeds via carbanions. The mechanism of the reaction is discussed.The absolute configuration of (+)‐2.6‐dimethyloctane was determined by synthesis from (S)‐(−)‐2‐methylbutanol‐1.
Studies on elimination VII. Syntheses of D,L‐Piperitone (D,L‐Δ1‐p‐Menthen‐3‐one) and Related Compounds from t‐butyl β‐keto‐esters
Authors: Lawesson Sven‐Olov , Larsen Erik Holger , Jakobsen Hans Jørgen , Frisell Christer 
Published: September 2010

AbstractMethyl vinyl ketone has been condensed with t‐butyl acetoacetate (and its 2‐alkyl and aralkyl derivatives) in the molar ratio of one to one and the infrared spectra have been examined. It is concluded that by a spontaneous cyclization the products are hydroxycyclohexanones. By heating them with catalytic amounts of p‐toluenesulfonic acid both water and the t‐butoxycarbonylgroup are eliminated smoothly giving piperitone and related cyclohexenones.
Spectropolarimetry III. Determination of the absolute configuration of some phenylethylamino derivatives
Authors: Dirkx I. P. , de Boer Th. J. 
Published: September 2010

AbstractThe absolute configurations of phenylethylamino derivatives I, II and III with two or three asymmetric centres were determined spectropolarimetrically by comparison with optical rotatory dispersions of related amino‐alcohols and amines and their dithiocarbamates and N‐nitroso derivatives.
Hetarynes VII. Evidence for the occurrence of 2,3‐pyridyne and some of its derivatives as intermediates in various reactions
Authors: Martens R. J. , den Hertog H. J. 
Published: September 2010

AbstractReactions of halogenopyridines, halogenopyridine‐N‐oxides and ethoxy derivatives of these compounds are described proceeding presumably via 2,3‐pyridyne, 2,3‐pyridyne‐N‐oxide, 4‐ethoxy‐2,3‐pyridyne and 4‐ethoxy‐2,3‐pyridyne‐N‐oxide as intermediates.
Cyclisation of ψ‐ionone with deuterated sulfuric acid
Authors: de Boer Th. J. , van't Hof H. A. , Veenland J. U. 
Published: September 2010

AbstractCyclisation of ψ‐ionone with deuterated sulfuric acid at 10° yields β‐ionone, deuterated in such positions as to indicate a predominant reaction via α‐ionone.
Valency‐bond studies of some conjugated hydrocarbons ‐ III: Calculations on heptalene
Authors: den Boer P. C. , den Boer D. H. W. , Goodwin T. H. 
Published: September 2010

AbstractValency‐bond calculations on heptalene suggest that bond length alternation occurs in the ground state. Penney‐Dirac bond orders have been determined.
Measuring air‐liquid surface tensions: A rapid method requiring small amounts of liquid (Short communication)
Authors: Rijke A. M. 
Published: September 2010

AbstractThe measurement of surface tensions of liquids is in general a time‐consuming procedure requiring relatively large amounts, i.e. severals mls of liquid. The method to be introduced here is very rapid, using only about two drops of liquid, thereby combining some of the specific advantages of the respective standard methods.The principle is very simple. The pressure required to expel the liquid, of which the surface tension is to be determined, from a narrow pore in a thin glass plate is read on a manometer. According to Laplace's equation this pressure is proportional to the surface tension of the liquidP = γ (1/R1 + 1/R2) (1)where P is the pressure in dynes/cm2, γ the surface tension (dynes/cm) and R1 and R2 the two principal radii of curvature of the liquid surface in the pore (cm.Most organic liquids have contact angles with clean glass which are zero or very nearly so, and if the pore is cylindrical, R1 and R2 will both be equal to r, the radius of the pore, so that equation (1) reduces toP = 2 γ/r (2)Now if the glass plate is sufficiently thin, so that the hydrostatic head in the pore can be neglected, and if r is known, γ can be determined using equation (2) with the same degree of accuracy as P can be measured.
Electron‐diffraction by gases apparatus and calculation techniques
Authors: Corbet H. C. , Dallinga G. , Oltmans F. , Toneman L. H. 
Published: September 2010

AbstractAn apparatus for electron‐diffraction by gases has been constructed. It incorporates a peripherally driven rotating sector; the specimen‐film distance is variable through vertical movement of the camera‐sector assembly.Calculation techniques are discussed and a least‐squares calculation with constraints is described, based on comparison of experimental and theoretical intensity data.
The reactions of cis‐cis‐tetrachloromuconic acid in solution
Authors: Shulgin A. T. 
Published: September 2010

AbstractTetrachloromuconic acid dehydrohalogenates spontaneously in an inert solvent to form either of two five‐membered lactone acids. In an alcoholic medium, however, there is the further loss of CO2 with concurrent incorporation of a molecule of solvent to yield the novel neutral lactone, IV.
Synthesis of the racemic mixtures of the diastereomeric nicotine‐2‐carboxylic acids
Authors: de Graaff G. B. R. , Ch. Melger W. , van Bragt J. , Schukking S. 
Published: September 2010

AbstractThe preparation of the racemic mixtures of the 4 stereomers of 1‐methyl‐5‐(3′‐pyridyl)proline (nicotine‐2‐carboxylic acid) has been studied; one pathway, starting from ethyl nicotinate and proceeding via 6‐(3′‐pyridyl)‐2‐piperidone proved successful.
The halogenation of aromatics: Part IX. Vapour‐phase chlorination and bromination of benzotrifluoride
Authors: Albers Robert J. , Kooyman E. C. 
Published: September 2010

AbstractVapour‐phase bromination (375‐475°) as well as chlorination (350‐450°) of benzotrifluoride led to halogenobenzotrifluorides containing 53‐54% meta, 30‐32% para and 13‐17% ortho isomers. Dihalogeno compounds were only formed to a small extent, except at high conversions. Liquid‐phase nitration of benzotrifluoride produced about 91% meta, 3% para and 6% ortho isomer.Competitive chlorinations at 400° indicated that benzotrifluoride has about the same reactivity as benzonitrile, chloro‐ and fluoro‐benzene and is 3‐4 times less reactive than benzene.These and earlier dataPart VI: J. W. Engelsma and E. C. Kooyman, Rec. Trav. Chim. 80, 537 (1961. Parts VII and VIII of this series deal with liquid‐phase halogenations: E. C. Kooyman and R. Louw, Rec. Trav. Chim. 81, 365 (1962) and 82, 616 (1963.
can be accommodated by a mechanismE. C. Kooyman, Pure and Applied Chemistry 7,193 (1963), (IUPAC Congress Lecture, London, July 1963.
involving hydrogen‐loss as the isomer‐pattern determining step in gas‐phase halogenations of aromatic compounds, possibly through a positively charged aromatic species.