bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photoreactions of aromatic compounds IX: Photo‐fries rearrangement of aryl sulfonates
Authors: Stratenus J. L. , Havinga E. 
Published: September 2010

AbstractPhenyl and a‐naphthyl p‐toluenesulfonates as well as phenyl methanesulfonate were found to undergo photochemical rearrangement upon irradiation with light from a high pressure mercury arc lamp. In the case of phenyl p‐toluenesulfonate, o‐ and p‐hydroxyphenyl‐p‐tolylsulfone and phenol were identified as products originating from a photo‐Fries reaction.
Studies in homogeneous catalysis: mechanism of the oxidation of aliphatic aldehydes and ketones catalysed by copper‐pyridine complexes
Authors: Brackman W. , Volger H. C. 
Published: September 2010

AbstractFrom kinetic and stoichiometric data the following mechanism is derived for the oxidative steps of the degradation of saturated aldehydes and ketones with oxygen, catalysed by copper‐pyridine complexes in the presence of triethylamine, described in the previous paper.The aldehyde (ketone) is deprotonated by methoxide ions, formed from methanol and triethylamine. The enolate ion co‐ordinates with cupric ion and pyridine to a complex which does not decompose spontaneously. This complex, however, is reactive toward oxygen, yielding an a‐hydroperoxide anion of the carbonyl compound, which decomposes via ionic reactions. The complex is also reactive towards triphenylphosphine, yielding a cuprous phosphine complex and presumably an enolate radical. The dimers of such radicals have been isolated.At high concentrations of oxygen the overall reaction rate is controlled by the rate of formation of the copper‐enolate complex or, if the copper concentration is sufficiently high, by the deprotonation step. In the absence of oxygen the same reactions control the rate of the reaction with triphenylphosphine.
Chemistry of acetylenic ethers 83: Acid‐catalyzed rearrangement of allenyl thioethers into thioethers with a conjugated diene system
Authors: Wijers H. E. , Brandsma L. , Arens J. F. 
Published: September 2010

AbstractAllenyl thioethers RCHCC(SR″′ )CHR′R″ (R, R′, R″ are H or alkyl: R′″ = alkyl) have been isomerized under the influence of acids into the dienes RCHCHC(SR′″) = CR′R″.
The conformation of non‐aromatic ring compounds. XXIII: Some halogenated 1,4‐dithianes
Authors: Kalff H. T. , Havinga E. 
Published: September 2010

AbstractSeveral 2,3‐ and 2,5‐disubstituted halogeno‐1,4‐dithianes have been prepared and their conformational features have been investigated by means of dipole moments and infrared spectra. The NMR spectra, described elsewhere2, support the results presented in this paper. The crystal structures of trans‐2,3‐dichloro‐1,4‐dithiane3 and trans‐2,5‐dibromo‐1,4‐dithiane1, determined by X‐ray analysis, provide us with a basis for the conformational analysis. In both compounds the halogen atoms are in axial positions.For the 2,3‐compounds (dichloro‐, dibromo‐, and 2‐bromo‐3‐chloro‐) the dipole moments remain constant on changing the solvent; the infrared spectra in the solid state (KBr discs) and in solution (CS2) are practically identical. The 2,5‐compounds, however, show additional peaks in solution in carbon disulfide, indicating a shift from the conformation with two axial halogen atoms to that with two equatorial halogen atoms in solution. The tetrachloro‐1,4‐dithiane, described by Varvoglis and Tsatsaronis4, is proved to be 2,2,3,3‐tetrachloro‐1,4‐dithiane.No trace of mono‐substituted, cis‐2,3‐ or cis‐2,5‐disubstituted products could be detected in our synthetic experiments.
On the oscilloscopic determination of rate constants of electrode reactions by means of square wave and sine wave current II: Scope of the method
Authors: Teppema P. , Sluyters‐Rehbach M. , Sluyters J. H. 
Published: September 2010

AbstractThe sources of error pertaining to the oscilloscopic determination of rate constants of electrode reactions are studied and the upper and lower limits of the methods are given. The former is mainly determined by the accuracy with which the moment of zero diffusion polarization can be adjusted.It is shown that the extrapolation of cell responses to zero frequency does not eliminate the contribution of the double layer capacitance completely. The remaining contribution is a negative resistance,‐2 σ2 Cd, irrespective of waveform.
On the reactivity of organophosphorus compounds: II. The effects of structural variations in the alkyl and alkoxy groups on the values of ΔH* and ΔS* for the alkaline hydrolysis of a number of organophosphorus esters
Authors: Ginjaar L. , Blasse‐Vel S. 
Published: September 2010

AbstractThe second‐order rate constants of the alkaline hydrolysis at different temperatures of a number of nitrophenyl phosphorus esters and the values of the quantities ΔH* and ΔS* at 25°C are reported. The effect of structural changes on the values of ΔH* and ΔS* are considered and are compared with similar changes in other nucleophilic substitution reactions, on both phosphorus and carbon atoms.
Microbiological transformation of 9β,10α‐steroids: I. Side chain degradation and 15‐hydroxylation of 9β,10α‐steroids
Authors: de Flines J. , van der Sijde D. , van der Waard W. F. 
Published: September 2010

AbstractFermentation of 9β,10α‐progesterone with Sporormia pollaccii yielded mainly 9β,10α‐testosterone.Fermentation with Helicosporium lumbricopsis afforded 9β,10α‐androst‐4‐ene‐3,17‐dione.Fermentation with Colletotrichum gloeosporioides afforded 15α‐hydroxy‐9β,10α‐progesterone. This product was converted with Helicosporium lumbricopsis to 15α‐hydroxy‐9β,10α‐androst‐4‐ene‐3,17‐dione. Fermentation of 6‐dehydro‐9β,10α‐progesterone with Mastigosporium heterosporum afforded 9β,10α‐androsta‐4,6‐diene‐3,17‐dione.
Microbiological transformation of 9β,10α‐steroids: II. 16‐Hydroxylation of 9β,10α‐steroids and of progesterone
Authors: van der Waard W. F. , van der Sijde D. , de Flines J. 
Published: September 2010

AbstractFermentation of progesterone, 9β,10α‐progesterone, 6‐dehydro‐9β,10α‐progesterone and 9β,10α‐testosterone with Sepedonium ampullosporum afforded the respective 16α‐hydroxy derivatives.
Enamine chemistry VIII. The syntheses of dienamines
Authors: Madsen Peter , Lawesson Sven‐Olov 
Published: September 2010

AbstractDienamines have been prepared by reacting n‐alkyl methyl ketones with morpholine. It is suggested that the initial step in the reaction is a condensation of two ketone molecules to an α,β‐unsaturated ketone followed by the reaction with morpholine.
Adducts of thiophosphoryl compounds with metal halides. I.: Addition compounds of triphenylphosphine sulfide
Authors: van der Veer W. , Jellinek F. 
Published: September 2010

AbstractAddition compounds have been prepared of triphenylphosphine sulfide with HgCl2, AlCl3, AlBr3, SnCl4, TiCl4, TiBr4, SbCl5, NbCl5, TaCl5, FeCl3 and FeCl2, and of triphenylphosphine oxide with AlCl3, AlBr3, TiBr4, SbCl5 and TaCl5. Reaction of NbCl5 with triphenylphosphine oxide yields the addition compound (Ph3PO)2NbOCl3. The syntheses, infrared spectra and some properties of the adducts are described and discussed.
The system titanium‐sulfur. I: The structure of Ti5S8 and the unit cells of Ti3S4 and Ti4S5
Authors: Flink E. , Wiegers G. A. , Jellinek F. 
Published: September 2010

AbstractThe structure of the phase Ti5S8 (rhombohedral) has been determined. It is based on a close packing of sulfur of the type cchh; the octahedral holes between adjacent cc sulfur layers and between adjacent hh layers are fully occupied by Ti, while the octahedral holes between adjacent ch layers are partly (1/5) occupied by metal atoms. The unit‐cell dimensions of Ti3S4 (rhombohedral) and Ti4S5 (hexagonal or trigonal) are given.
Investigations on organotin compounds. XXII: Hydrolysis products of alkyltin trichlorides
Authors: Luijten J. G. A. 
Published: September 2010

AbstractWhen ethyl‐, butyl‐ and octyl‐tin trichlorides are subjected to increasingly severe hydrolysis conditions a number of hitherto unknown compounds are formed which are intermediates between alkyltin trichlorides and alkanestannonic acids. The preparation and properties of these compounds and of the corresponding stannonic acids are described.
Structure determination of unknown peptides isolated from pig neurohypophysis, by mass spectrometrical analysis: (Of their 2,4‐dinitrophenyl peptide methyl esters)
Authors: Penders Th. J. , Heerma W. , Copier H. , Dijkstra G. , Arens J. F. 
Published: September 2010

AbstractThe amino‐acid sequence of 2,4‐dinitrophenyl‐peptide methyl esters has been determined by mass spectral analysis. Using this technique, the structure of a number of simple peptides isolated from pig neurohypophysis, could be elucidated. The structure of valyl‐leucine, alanyl‐valyl‐leucine, tyrosyl‐glycine and O‐Acetyl‐tyrosyl‐valine was established.
Conformation of non‐aromatic ring compounds XXX: Dipole moments, NMR spectra and conformations of some trans‐1,2‐dihalogenocyclopentanes
Authors: Altona C. , Buys H. R. , Havinga E. 
Published: September 2010

AbstractThe dipole moments and NMR spectra of trans‐1,2‐dichloro‐ (I), trans‐1,2‐bromochloro‐ (II), trans‐1,2‐dibromo‐ (III) and trans‐1,2‐dibromo‐1‐methylcyclopentane (IV) in several solvents are reported. Special attention is given to the separation of the outer peaks in the low‐field part of the NMR spectra, due to the protons in the CHX‐moiety. This separation is equal to JAX + JBX and is shown to be correlated linearly with the square of the electric moment.It is proposed that the conformational properties of these molecules be described in terms of a solvent‐dependent dynamic equilibrium aa ⇌ ee, with the diaxial conformation predominating even in a highly polar solvent. Each of the two conformers may correspond to the half‐chair or the envelope model with the halogen atoms in the most puckered part of the ring. A limited pseudolibration about these forms is possible.
Conformation of non‐aromatic ring compounds XXXI: Infrared and Raman Spectra of some trans‐1,2‐dihalogenocyclopentanes
Authors: Buys H. R. , Altona C. , Havinga E. 
Published: September 2010

AbstractThe infrared and Raman spectra of trans‐1,2‐dichloro‐(I), trans‐1‐bromo‐2‐chloro(II), trans‐1,2‐dibromo‐(III) and trans‐1,2‐dibromo‐1‐methylcyclo‐pentane(IV) were measured in carbon disulfide and in the neat liquid. From the properties of the bands assigned to the carbon‐halogen stretching frequencies it is concluded that the diaxial conformations predominate in solution, the halogen atoms occupying the most buckled part of the ring. The absorption bands of I are broader than those of III and IV. This seems to indicate that the ring geometry of I is less defined and that in compound I twisting of the ring in a pseudolibration movement occurs to a larger extent. From a comparison with the carbon‐halogen stretching frequencies in the analogous cyclohexanes several common features emerge.
Studies in transition metal chemistry. part V: Soluble Ziegler‐type catalysts based on vanadium. Part I
Authors: de Liefde Meijer H. J. , van den Hurk J. W. G. , van der Kerk G. J. M. 
Published: September 2010

AbstractExperiments are described aiming at a simplification of the catalyst system originally consisting of a mixture of tetraphenyltin, aluminium bromide and vanadium tetrachloride (or vanadium oxytrichloride). It is shown that tetraphenyltin merely acts as a phenylating agent for the aluminium bromide and that only two of the four phenyl groups are available for this purpose. With regard to catalytic activity the original mixture is equivalent to mixtures of vanadium tetrachloride and excess of monoalkyl‐ or monoaryl‐aluminium halides. Some evidence has been obtained that organic groups are part of the vanadium/aluminium complex occurring in the reaction mixtures.
Fluorescent intermediates in the Maillard reaction
Authors: Berrens L. 
Published: September 2010

AbstractThe development of fluorescent compounds has been studied in mixtures of amines and aldoses undergoing Maillard reaction at moderate temperatures, and the fluorescence emission spectra of some N‐substituted 1‐amino‐1‐deoxy‐2‐ketoses are given. A study of pH‐dependency suggests fluorescence to be mainly due to the 1,2‐enol and 2,3‐enediol tautomers of the Amadori product formed, the latter enol contributing in the form of a cyclic configuration.Some results are presented illustrating the formation of highly resistant nitrogen‐containing ring systems during Kjeldahl‐digestion of N‐substituted 1‐amino‐1‐deoxy‐2‐ketoses.
Extended Hückel calculations on some conformational problems
Authors: van Eijck B. P. 
Published: September 2010

AbstractThe extended Hückel theory applied to single molecules of simple carboxylic acids is able to provide an explanation for the coplanarity of many carboxyl groups with an α‐substituent, which is observed in the crystalline state. Quantitative agreement with experimental rotation barriers is poor, but the shape of the calculated barriers largely agrees with experimental data.
Transannular course in the addition of halogen to cis‐cyclo‐octene and in some related reactions
Authors: Henniger P. W. , Dukker L. J. , Havinga E. 
Published: September 2010

AbstractIn reactions of (cis)cyclo‐octene with lead tetrachloride and hydrogen chloride/methylene chloride as well as with N‐chlorourea and acetic acid/water, transannular reactions were found to prevail. The dichlorocyclo‐octane fractions isolated from the products of the two reactions, both consisted of a mixture of cis‐ and trans‐1,4‐dichlorocyclo‐octanes, trans‐1,2‐dichlorocyclo‐octane and possibly very small amounts of other compounds. The main product of the reaction with N‐chlorourea in an acetic acid/water medium under standard conditions (vide infra) is 4‐chlorocyclo‐octanol (one isomer), which on treatment with phosphorus pentachloride yields a mixture of the 1,4‐dichlorocyclo‐octanes and some trans‐1,2‐dichlorocyclo‐octane. 4‐Chlorocyclo‐octene on addition of hydrogen chloride yields a mixture of cis‐ and trans‐1,4‐dichlorocyclo‐octanes.The reactions leading to the corresponding bromo compounds proceed in a similar way; it proved difficult to perform a controlled reaction with lead tetrabromide, however. With the reaction of bromine and cyclo‐octene “transannular addition” is observed at low temperatures (∼ −100°).
Pyrazoles I.: Ionisation constants and UV spectra of 4‐nitropyrazoles
Authors: Habraken Clarisse L. , van Woerkom P. C. M. , De Wind H. W. , Kallenberg C. G. M. 
Published: September 2010

AbstractThe differences in UV spectra and acidity between 4‐nitropyrazole and 3(5)‐methyl‐4‐nitropyrazole and 3,5‐dimethyl‐4‐nitropyrazole indicate the absence of steric influence of ortho‐methyl groups.
The conformation of non‐aromatic ring compounds, part XXXII. The crystal structure of trimethylene sulfite at −100°C
Authors: Altona C. , Geise H. J. , Romers C. 
Published: September 2010

AbstractTrimethylene sulfite, m.p. − 14°, crystallizes in the orthorhombic system, space group P212121, Z = 4. The unit cell dimensions at − 100° are a = 7.451, b = 7.703 and c = 8.98 Å. The structure was solved by means of a Patterson synthesis and refined by the least squares method, using three‐dimensional reflexion data (MoKa radiation, collected at − 100°). The six‐membered ring has the chair conformation and the SO bond points toward the axial direction. The geometry of the ring is described in terms of torsional angles.
Preparation of primary alcohols related to prostaglandins
Authors: Pabon H. J. J. , van der Wolf L. , van Dorp D. A. 
Published: September 2010

AbstractPrimary alcohols related to prostaglandins were prepared by reduction of the methyl ester of prostaglandin E1 with lithium tetrahydridoaluminate. The structures of the reaction products were established by mass spectrometry.
Studies on imidazoles. Part III The Synthesis of Some 7,8‐Dialkylpurines
Authors: Trout G. E. , Levy P. R. 
Published: September 2010

AbstractThe synthesis ‐ using preformed 1,2‐dialkylimidazoles as starting materials ‐ of a number of 7,8‐dialkylpurines is described.
Equilibration of benzene derivatives. Part III: Mono‐ and poly‐substituted iodo‐ and bromo‐benzenes
Authors: Augustijn G. J. P. , Kooyman E. C. 
Published: September 2010

AbstractTransiodination occurs when reacting iodobenzenes with other halogeno‐or with alkylbenzene derivatives in the presence of aluminium bromide at room temperature.Isomer equilibria among iodobenzenes resemble those for the corresponding bromides1. Di‐ and tri‐substituted bromo‐ and iodo‐benzenes show equilibrium patterns agreeing with those computed on the basis of addivitity, using patterns for monosubstituted halogenobenzenes. Results are discussed in terms of partial equilibrium factors1, believed to be mainly governed by electrostatic and steric interactions.Results of direct brominations (AlBr3 catalyst, no solvent) indicate that for halogeno‐ and alkylbenzenes the main difference between the isomer ratios observed and those at equilibrium consists in the large proportions of meta (or 1, 3, 5) isomer found in the latter case.
Investigations on sterols XXXI: Synthesis and conformation of ring B of 6,6‐dihalo‐9β,10α‐testosterones
Authors: Westerhof P. , Hartog J. 
Published: September 2010

AbstractHalogenation of 3‐ethoxy‐6‐halo‐9β,10α‐androsta‐3,5‐dien‐17β‐ol 17‐acetates with perchloryl fluoride, N‐chlorosuccinimide or N‐bromosuccinimide gives rise to the formation of 6,6‐difluoro‐, 6α‐ and 6β‐chloro‐6‐fluoro‐ and 6α‐ and 6β‐bromo‐6‐fluoro‐9β, 10α‐testosterone 17‐acetates. With perchloryl fluoride, besides fluorination at position 6, introduction of fluorine at position 4 takes place. The dehydrohalogenation of the 6,6‐dihalo compounds is investigated. NMR data indicate that ring B of 6β‐bromo‐6‐fluoro‐9β,10α‐testosterone 17‐acetate has a boat‐conformation.
Alcohols as ligands. I. Crystalline hexa‐ethanol metal salts
Authors: van Leeuwen P. W. N. M. 
Published: September 2010

AbstractThe syntheses of approximately twenty coordination complexes with the ligand ethanol are reported. A new synthetical method is used to obtain these crystalline hexa‐alcohol solvates. About ten perchlorates and fluoroborates of divalent metal ions are easily prepared by dissolving the corresponding hydrates in ethyl orthoformate. In the solid state, even the nitrates contain hexa‐ethanol coordinated metal ions. The electronic and vibrational spectra, a summary of the proton magnetic resonance spectra and some X‐ray powder patterns are given. The complexes of this very weak ligand are now easily obtainable and will be of great importance because ethanol may be replaced simply by many ligands.
Chemistry of acetylenic ethers. Part 88: Synthesis of β‐hydroxy‐alkynes, substituted at the α‐carbon atom
Authors: Schaap A. , Brandsma L. , Arens J. F. 
Published: September 2010

AbstractMetallation of allenyl thioethers, R1CHCCHSC2H5 (I) (R1 = alkyl), by means of methyl‐ or butyl‐lithium in ether, followed by addition of aldehydes or ketones, R2R3C  O (R2 and R3 are H or alkyl), affords a mixture of the two carbinols R1CHCC[CR2R3C(OH)](SC2H5) (III) and R1CH[CR2R3(OH)] CCSC2H5 (IV). By treatment of the mixture with an excess of potassium amide in liquid ammonia IV is converted into the metallated β‐hydroxy‐alkyne R1CH[CR2R3(OH)]CCH (VI), probably via a nucleophilic substitution at sulfur. In the cases where R1  CH3, ethanethiol is eliminated from III with formation of the metallated enynyl alcohol HCCCHCH[CR2R3(OH)], (V). A number of alkylated derivatives RCCCHR1CH2OH have been prepared from VI (with R2 and R3 = H).
Reactions of γ‐thiopyran‐1,1‐dioxide
Authors: Molenaar E. , Strating J. 
Published: September 2010

AbstractAddition reactions of γ‐thiopyran‐1,1‐dioxide (I), are compared with those of divinyl sulfone (II). In contrast with II no Diels‐Alder reactions could be realized with I. Fairly strong nucleophiles, however, give addition products with I; usually only one mole is added and the remaining double bond is shifted from the α‐ to the β‐position with respect to the sulfonyl group.
Aromatic Sulfonation. Part XVI: Sulfonation of naphthalene and its monosulfonic acids in concentrated aqueous sulfuric acid
Authors: Cerfontain H. , Telder A. 
Published: September 2010

AbstractThe sulfonation of naphthalene in concentrated aqueous sulfuric acid has been reinvestigated. Rate measurements have been made in the region of 79.0‐83.4 wt‐% H2SO4 at 25°. The kinetically determined isomer distribution has been determined in the acid range of 75.5‐95.2 wt‐% H2SO4. At 25°, the ratio of 1‐ to 2‐naphthalenesulfonic acid decreases from 5.9 to 4.1 on varying the acid concentration from 75 to 95 wt‐% H2SO4. The higher reactivity of the 1‐ as compared with the 2‐position of naphthalene is largely due to the difference in enthalpy of activation, for the difference in entropy of activation is very small. The partial rate factors for sulfonation at the 1‐ and 2‐ positions decrease with increasing acid concentration. The ratio of the logarithms of these partial rate factors is 1.60 ± 0.03.The ratio of the rate constants of sulfonation of 1‐ and 2‐naphthalenesulfonic acid at 25° is ∼ 0.08. The partial rate factors for the most reactive positions of these acids have been compared with those for meta‐substitution of benzenesulfonic acid.
Chemistry of propadiene. Part IV: The addition of formaldehyde to propadiene in aqueous sulfuric acid solution
Authors: Peer H. G. , Schors A. 
Published: September 2010

AbstractThe reaction between propadiene and formaldehyde in aqueous sulfuric acid solution was investigated. When an excess of formaldehyde is present, it reacts with propadiene in a molecular ratio of 8: 1, yielding the 2,4,10,12,15‐pentaoxadispiro[5.1.5.3]hexadecan‐7‐one.
Chemistry of the silylamines. Part VI: Condensation of N,N‐diethylaminotrimethylsilane with alcohols
Authors: Pike R. M. , Weaver S. J. 
Published: September 2010

AbstractThe rate of condensation of a series of alcohols with N,N‐diethylaminotrimethylsilane have been measured. It was observed that the relative rate varied inversely with the chain length of the straight chain primary alcohols investigated. Branched alcohols reacted at slower rates than the straight chain alcohols through n‐octyl alcohol.
Structure determination of the allergenic agent, isolated from tulip bulbs
Authors: Brongersma‐Oosterhoff Ulrika W. 
Published: September 2010

AbstractHandling of tulip bulbs taking place in bulb nurseries often causes a typical allergic reaction of the skin (“tulip fingers”). It is the purpose of this paper to report the results of an investigation into the structure of the chemical compound, possessing the allergic properties.The principle is a yellow, hygroscopic, non‐crystalline substance, which can be obtained by extraction of the tulip bulb (tulipa gesneriana) with 70% ethanol or 70% acetone and resolving the crude extract by paper chromatography. Paper chromatography (paper Whatman no. 1) gives a Rf‐value of 0.63 in ethyl acetate: pyridine: water = 2: 1: 2. The allergenic principle is soluble in ethanol and water, but not in cyclohexane, carbon tetrachloride, chloroform, diethyl ether and ethyl acetate. Since it could not be obtained in crystalline form, X‐ray analysis could not be used and for this reason other chemical and physical methods had to be used.
Properties of diazosulfonates. Part II: The rate of the reaction between 2‐methoxybenzenediazonium and sulfite ions
Authors: van Beek L. K. H. , Helfferich J. , Jonker H. , Thijssens Th. P. G. W. 
Published: September 2010

AbstractThe reaction between 2‐methoxybenzenediazonium and sulfite ions in aqueous solution was followed by polarography. The polarographic waves of sulfite, diazonium, and diazosulfonate were studied in the pH range of 1‐7. The second order rate constants found at 11° and 20° and the rate constant at 25°C reported in part I were corrected to zero ionic strength yielding values of 400, 700, and 2000 1 mole−1 s−1, respectively.