bluuebunny/crossref_metadata_2025_split huggingface dataset:
pH‐Measurements in alcohol‐water mixtures, using aqueous standard buffer solutions for calibration
Authors: Gelsema W. J. , de Ligny C. L. , Remijnse A. G. , Blijleven H. A. 
Published: September 2010

AbstractE.m.f.‐measurements on cells of the type: Hg/Hg2Cl2/saturated KCl‐soln. (aq.)/standard buffer soln./saturated KCl‐soln.(aq.)/Hg2Cl2/Hg, using standard buffer solutions in methanol‐water and ethanol‐water mixtures and liquid‐junction forming devices of different design, showed that, for three different boundary‐types, the liquid‐junction potentials are identical within experimental error.E.m.f.‐measurements on cells of the type: glass electrode/standard buffer soln./saturated KCl‐soln.(aq.)/Hg2Cl2‐Hg, using succinate standard buffer solutions in methanol‐water and ethanol‐water mixtures and different types of glass electrodes, proved that the variation of the standard potential of these glass electrodes with the composition of the alcohol‐water mixture does not depend on the type of glass electrode.These results, together with the previously shown fact, that liquid‐junction potentials at the boundaries standard buffer soln. (alcohol‐water)/saturated KCl‐soln.(aq.) are independent of the nature of the buffering solute, render possible the determination of pa*H‐values of solutions in alcohol‐water mixtures by calibration of a pH‐meter with the aid of an aqueous standard buffer solution and correction of the pH‐readings with a correction term δ. For a number of methanol‐water and ethanol‐water mixtures δ‐values are tabulated and graphs, showing the variation of δ with methanol‐ and ethanol‐percentage, are given.
Dihydroquinolones IV
Authors: Speckamp W. N. , Huisman H. O. 
Published: September 2010

AbstractAcylation of several N‐tosyldihydroquinolones and N‐tosylbenz[h]dihydroquinolones under alkaline conditions, gave results depending strongly on the steric volume of the ester employed. An explanation for this phenomenon is offered. The resulting α‐acylated ketones have been converted to the corresponding 2H‐pyrazolo[4,3‐c]quinolines and 2H‐benz[h]pyrazolo[4,3‐c]quinolines.
Microbiological transformation of 9β,10α‐steroids III.: 11‐Hydroxylation and side chain degradation of 9β,10α‐steroids
Authors: van der Sijde D. , de Flines J. , van der Waard W. F. 
Published: September 2010

AbstractFermentation of 17α,21‐dihydroxy‐9β,10α‐pregn‐4‐ene‐3,20‐dione with Aspergillus ochraceus yielded 11α,17α,21‐trihydroxy‐9β,10α‐pregn‐4‐ene‐3,20‐dione and 15α,17α,21‐trihydroxy 9β,10α‐pregn‐4‐ene‐3,20‐dione. Fermentation of 9β,10α‐progesterone with Aspergillus ochraceus afforded 11α‐hydroxy‐9β,10α‐progesterone.Fermentation of the latter product with Sporomia pollaccii and Helicosporium lumbricopsis afforded 11α‐hydroxy‐9β,10α‐testosterone and 11α‐hydroxy‐9β,10α‐androst‐4‐ene‐3,17‐dione.Fermentation of 9β,10α‐testosterone with Aspergillus ochraceus yielded 11α‐hydroxy‐9β,10α‐testosterone and 11α‐hydroxy‐9β,10α‐androst‐4‐ene‐3,17‐dione.Fermentation of 17α‐hydroxy‐9β,10α‐progesterone with Aspergillus ochraceus afforded 11α,17α‐dihydroxy‐9β,10α‐progesterone and 11α‐hydroxy‐9β,10α‐androst‐4‐ene‐3,17‐dione.
The copper‐catalysed oxidation of unsaturated carbonyl compounds: V. Kinetics and mechanism
Authors: Volger H. C. , Brackman W. 
Published: September 2010

AbstractWe have investigated the kinetics of the oxidation of α,β‐ and β,γ‐unsaturated aldehydes or ketones by oxygen in methanol containing a base and a cupric pyridine complex as a catalyst. The results show that the mechanism comprises the following steps: a rate‐determining deprotonation of the substrate, yielding a dienolate anion, oxidation of this anion by the cupric complex to a dienoxy radical (or to a charge transfer complex of cupric and the dienolate anion), and oxygenation of the radical resulting in a peroxy radical, which is reduced by a cuprous complex to a γ‐hydroperoxide anion. The subsequent base‐catalysed reactions of this species were discussed in Part III of this series.A cupric ion‐initiated chain oxidation of the substrate does not occur under the conditions applied. In the absence of oxygen the cupric complex yields a stoichiometric amount of the dienoxy radicals which combine to give α,α‐, γ,γ‐, α,γ‐ and oxygen‐γ‐dehydrodimers.The active cupric complex contains a methoxide group and only three pyridine molecules.
Chemistry of acetylenic ethers 84: Addition of aldehydes, ketones, esters and amides to 1‐alkynyl ethers under the influence of Lewis acids; direct formation of α,β‐unsaturated esters
Authors: Vieregge H. , Schmidt H. M. , Renema J. , Bos H. J. T. , Arens J. F. 
Published: September 2010

AbstractA large variety of α,β‐unsaturated esters has been prepared by addition of aldehydes and ketones to 1‐alkynyl ethers under the catalytic influence of boron trifluoride‐ether. With carboxylic esters and dimethylformamide β‐alkoxy‐ and β‐dimethylamino‐substituted acrylic esters are formed. The stereochemistry of the ester formation has been investigated.
Chemistry of acetylenic ethers 85: Preparation of compouds with a 3,5‐dien‐1‐yne system by 1,2 and 1,6 elimination of alcohols from various types of unsaturated ethers
Authors: van Boom J. H. , Brandsma L. , Arens J. F. 
Published: September 2010

Abstract1,2 Elimination of HOR [R = CH3 or CH(CH3)(OC2H5)] from ethers of the types HCCCHCHCH2CH2OR and HCCCHC(CH3)CH2CH2OR, using an excess of potassium amide in liquid ammonia, affords the dienynes HCCCHCHCHCH2 and HCCCHC(CH3)CHCH2, respectively, in good yields.1,6 Eliminations of HOR [R = CH3, C2H5, n‐C4H9, n‐C6H13, CH(CH3)(OC2H5)] from the ethers H3CCCCHCHCH2OR and H3CCC‐C(CH3)CHCH2OR have also been effected with potassium amide. The yields of the dienynes HCCCHCHCHCH2 and HCCCHC(CH3)CHCH2 obtained in this manner were good, except in the cases where R = CH3 and C2H5. 1,6 Elimination of ethanol from H5C2SCH2CCCHCHCH2OC2H5 could be achieved under milder conditions, viz. with sodium ethoxide in liquid ammonia. The dienynyl thioether H5C2SCCCHCHCHCH2 was obtained in good yield. The same compound was prepared from hexadienyne HCCCHCHCHCH2, lithium amide and diethyl disulfide C2H5SSC2H5.
Studies in transition metal chemistry. part IV: The suitability of cyclopentadienylvanadium compounds as components of Ziegler‐type polymerization catalysts
Authors: de Liefde Meijer H. J. , van der Kerk G. J. M. 
Published: September 2010

AbstractThe polymerization of ethylene with Ziegler‐type catalysts containing mono‐and bis‐cyclopentadienylvanadium compounds as constituents has been studied. The activities of these catalyst mixtures have been compared with those of two known highly active systems, viz. (i) the one based on biscyclopentadienyltitanium dichloride and aluminium alkyls and (ii) the one based on vanadium tetrachloride or vanadium oxytrichloride, respectively, and a large excess of aluminium alkyls. Under a wide variety of reaction conditions the cyclopentadienylvanadium compounds were found to be less active. Moreover, with vanadium, moderate activity was observed for systems based on monocyclopentadienyl derivatives and negligible to weak activity for mixtures based on biscyclopentadienyl derivatives. The large difference in suitability as catalyst constituents between the biscyclopentadienyl derivatives of titanium and of vanadium is discussed.
Steric effect of o‐methyl groups on the ionization constants of phenols. The influence of the solvent
Authors: de Ligny C. L. 
Published: September 2010

AbstractBy applying McDaniel and Brown's method2 for the separation of polar and steric effects of o‐alkyl groups to Rochester's data1 for the ionization constants of methylphenols in methanol, the o‐effect of a methyl group was shown to be 0.33 ± 0.01 pK‐units.This figure is much larger than the corresponding figure for the o‐effect in water as the solvent (0.14 ± 0.01), showing that the o‐effect is strongly solvent‐dependent and thus lending further support to the view that it is mainly caused by steric hindrance of solvation.
Ring‐transformations in reactions of heterocyclic halogeno compounds with nucleophiles (VI): A tracer study of the conversion of 4‐chloro‐2‐phenylpyrimidine into 4‐methyl‐2‐phenyl‐s‐triazine
Authors: van Meeteren H. W. , van der Plas H. C. 
Published: September 2010

AbstractBy treating 4‐chloro‐2‐phenylpyrimidine‐4‐14C with potassium amide in liquid ammonia, labelled 4‐methyl‐2‐phenyl‐s‐triazine was obtained. By degradation of this s‐triazine derivative by acid hydrolysis, the 14C‐label was found to be present in one position only, viz. position 4. This result strongly indicates that in this ring‐transformation no bicyclic intermediates are involved and that the opening of the pyrimidine ring occurs by fission of the C(5)C(6) bond and not of the C(4)C(5)bond. The mechanism of this reaction is discussed.
Benzilic acid‐type rearrangement of a nitro‐olefin: Nucleophilic aromatic addition VII
Authors: de Boer Th. J. , van Velzen J. C. 
Published: September 2010

Abstract14C‐labelled “trismethylene‐trinitrobenzene” (II) is oxidized by alkaline permanganate to a hydroxy‐acid (III) with a label distribution supporting a benzilic acid type rearrangement as depicted in Scheme 2.
The oxidative coupling of vinyl acetate with palladium acetate; synthesis of 1,4‐diacetoxy‐1,3‐butadiene
Authors: Kohll C. F. , van Helden R. 
Published: September 2010

AbstractVinyl acetate reacts with palladium acetate to produce 1,4‐diacetoxy‐1,3‐butadiene. In addition, 1,1,4,4‐tetraacetoxybutane and 1,1,4‐triacetoxy‐2‐butene are formed. When using palladium chloride in combination with lithium acetate no oxidative coupling takes place: vinyl acetate is then converted into acetaldehyde + acetic anhydride. The mechanism of this novel oxidative coupling reaction is discussed.
On the reactivity of organophosphorus compounds. Part III: Application of the Hammett relation to the rates of alkaline hydrolysis of a number of diethyl substituted phenyl phosphates
Authors: van Hooidonk C. , Ginjaar L. 
Published: September 2010

AbstractAs part of our program on the reactivity of organophosphorus compounds in nucleophilic substitution reactions the rates of alkaline hydrolysis have been determined for a number of diethyl substituted phenyl phosphates (diethyl phenyl phosphate and eight ortho‐, five meta‐ and thirteen para‐nuclear‐substituted derivatives).The following relationships were observed:
— an excellent ϱσ correlation between the log kOH values of diethyl phenyl phosphate and four meta‐substituted derivatives and the “primary” σ values of van Bekkum et al. for meta‐substituents;
— a satisfactory correlation between the log kOH values of some ortho‐substituted compounds and Taft's σ* values for ortho‐substituents.
Calculated σ values have been compared with van Bekkum's σn values concluding very weak and no mesomeric para interactions for − M and + M substituents respectively.
The chemistry of cycloheptatriene. Part XIV: Hydrogen shifts in (4‐Dimethylaminophenyl)cycloheptatrienes
Authors: ter Borg A. P. , Kloosterziel H. , Westphal Y. L. 
Published: September 2010

AbstractWhen the 7‐isomer of the title compound is heated, the successive formation of the 3‐, 1‐, and 2‐isomers by thermal 1–5 shifts of hydrogen is observed. Irradiation of the 3‐isomer yields the 2‐isomer. The rate constants for the various shifts are 1.7 ± 0.4 times larger than the corresponding constants for phenylcycloheptatriene.
Oxidative dimerization of β‐substituted α‐olefins by palladium acetate
Authors: Volger H. C. 
Published: September 2010

Abstractα‐Olefins carrying alkyl or aryl groups as substituents at the β‐carbon atom can be oxidized by palladium acetate to 1,1,4,4‐tetra‐substituted 1,3‐butadienes. Prolonged oxidation of the primary product by an excess of the oxidant may lead to a benzene derivative.The oxidation takes place at the terminal vinylic carbon atom exclusively.A binuclear π‐olefin palladium acetate complex is proposed as an intermediate.
Isolation and identification of α‐methylene‐butyrolactone, A fungitoxic substance from tulips
Authors: Bergman B. H. H. , Beijersbergen J. C. M. , Overeem J. C. , Sijpesteijn A. Kaars 
Published: September 2010

AbstractA fungitoxic substance has been isolated from extracts from the white skins of tulip bulbs, from the fleshy bulb scales and from the flower pistils. The compound was identified as α‐methylenebutyrolactone.
Acetylenic thiolesters as a source of thioketenes
Authors: Wijers H. E. , van Ginkel C. H. D. , Brandsma L. , Arens J. F. 
Published: September 2010

Abstract1‐Acetylthio‐1‐hexyne, magnified image, is cleaved by nucleophilic reagents. With primary and secondary amines, RR′NH (R = alkyl or aryl, R′  H or alkyl), N‐substituted acetamides CH3CONRR′ and N‐substituted thioamides C4H9CH2C(S)NRR′ are produced in good yields, the latter compounds presumably via the thioketene C4H9CHCS. In the case of ammonia, mainly acetamide and the polymer of the thioketene are obtained. Acethydrazide and 3,6‐dipentyl‐1,4 dihydro‐1,2,4,5‐tetrazine, I, have been isolated from the reaction mixture of acetylthiohexyne and hydrazine hydrate. Potassium amide, dissolved in liquid ammonia, converts acetylthiohexyne into hexynethiolate, C4H9CCSK (and acetamide); subsequent addition of ethyl bromide gives ethylthiohexyne, C4H9CCSC2H5, in excellent yield. If acetylthiohexyne is allowed to react with a mixture of ethanethiol and sodium ethanethiolate in dimethylformamide, the intermediate thioketene is trapped to produce the dithioester C4H9CH2C(S)SC2H5.
Activity coefficients of individual ions
Authors: Alfenaar M. , de Ligny C. L. 
Published: September 2010

AbstractExisting methods for the estimation of the primary medium effect for individual ions are critically reviewed and an improved method for its estimation is developed.By this method the primary medium effect of the hydrogen ion has been determined for the transfer from water to methanol‐water mixtures and methanol. The medium effect of the alkali and the halide ions are then also known. The accuracy of the values so obtained for the individual ions is of the same order as the accuracy of experimentally determined values for electroneutral combinations of ions.
Free radical additions. Part I: Free radical addition of cyclo‐octane to unsaturated compounds
Authors: van Bruggen E. , Boelens H. , Rijkens F. 
Published: September 2010

AbstractCyclo‐octyl radicals, generated by decomposition of di‐t‐butyl peroxide (DTBP) in cyclo‐octane, react with unsaturated compounds. The addition of cyclo‐octane to acrylic acid, crotonic acid, methyl vinylacetate or allyl alcohol yields the corresponding 1 : 1 adducts. Retention indices and NMR spectral data for these addition products are given.
The absolute configuration of β‐hydroxyvaline
Authors: Beyerman H. C. , Maat L. , de Rijke D. , Visser J. P. 
Published: September 2010

AbstractThe optical rotatory dispersion spectra of the enantiomers of β‐methoxyvaline were measured between 200 and 400 nm. From the Cotton effect at 210 nm follow the absolute configurations, and consequently those of the derived hydroxy amino acids: D‐(‐)‐ and L‐(+)‐β‐hydroxyvaline.
The universal pH‐scale for solutions at different temperatures and in different solvents
Authors: de Ligny C. L. , Alfenaar M. 
Published: September 2010

AbstractA universal acidity scale, holding for solutions at any temperature and in any solvent, is developed. It is based on the operational pH‐definition and relates the measured pH‐values to the change in chemical potential on transferring a proton from solution X to a hypothetical solution of unit proton activity at 25° in water.This acidity scale is an extension of the universal pH‐scale for methanol‐water mixtures at 25° proposed by the authors1 and is closely related to the universal acidity scale for water at different temperatures, proposed by Aleksandrov and Lebed'.2 The disadvantage of the latter is that it does not lead to a simple, or easily applicable, physical significance of the measured acidities.
The system NbCl5‐Nb2O5: Part V the P‐T‐x space model and the thermodynamic properties of NbOCl3
Authors: Hart W.'T , Meyer G. 
Published: September 2010

AbstractFrom the results of the vapour pressure measurements described in previous communications of this series1 and the determination of the compositions of the phases occurring in the different equilibria, the P‐T‐x space model for the binary system is derived. The P‐T and T‐x projections and the most important P‐x and T‐x sections are given. The thermodynamic constants of NbOCl3 are derived also from the results of the measurements described previously.
Complexes of ligands containing S  O: Parts IV and V. IV. Trimethylene sulfite as a ligand. V. ligand field spectra of cobalt(II) and nickel(II) compounds
Authors: van Leeuwen P. W. N. M. , Groeneveld W. L. 
Published: September 2010

AbstractThree inorganic complexes of trimethylene sulfite (abbreviated tms) viz. Ni(tms)6(BF4)2, Co(tms)6(BF4)2 and Co(tms)6(ClO4)2 are reported. The analyses and X‐ray diffraction diagrams of the three isomorphous compounds are given.In Part V the diffuse reflectance spectra are reported for complexes of the following sulfoxides: diphenyl, methyl phenyl, dimethyl, tetramethylene and pentamethylene sulfoxide, and trimethylene sulfite. Remarkable differences are found in the spectrochemical parameters in the solid state.
Structure of a thiopyran‐1,1‐dioxide
Authors: Boelema E. , Visser G. J. , Vos Aafje 
Published: September 2010

AbstractAn X‐ray diffraction study has shown the thiopyran‐1,1‐dioxide prepared by debromation of 2,3,5,6‐tetrabromotetrahydrothiopyran‐1,1‐dioxide with zinc to be α‐thiopyran‐1,1‐dioxide.
α‐Halogenovinyl sulfoxides: Re‐examination of the structure of some β‐halogenovinyl sulfoxides
Authors: Molenaar E. , Strating J. 
Published: September 2010

AbstractThe compounds obtained by dehydrohalogenation of α,β‐dihalogenated sulfoxides have the α‐halogenovinyl structure and not the β‐substituted structure previously assigned to them1−4.
Chemistry of acetylenic ethers. Part 90: Cyclotetramerization of ethynyl ethers to 1,3,5,7‐tetra‐alkoxycyclo‐octatetraenes. Syntheses of 3,5,7‐triethoxy‐2,4,6‐cyclo‐octatrienone and of 1,3,5,7‐tetra‐alkoxy‐2,6‐dioxa‐adamantanes
Authors: Braams J. F. H. , Bos H. J. T. , Arens J. F. 
Published: September 2010

AbstractEthoxyethyne and propoxyethyne are slowly tetramerized to 1,3,5,7‐tetra‐alkoxycyclo‐octatetraenes under the influence of alkali amides in liquid ammonia. By partial hydrolysis 1,3,5,7‐tetraethoxycyclo‐octatetraene (I) is converted into 3,5,7‐triethoxy‐2,4,6‐cyclo‐octatrienone (III). Treatment with acidified ethanol or methanol leads to 1,3,5,7‐tetraethoxy‐2,6‐dioxa‐adamantane (V) and 1,3,5,7‐tetramethoxy‐2,6‐dioxa‐adamantane (IV), respectively.
Protonation of halogen‐containing benzenes in HF‐SbF5. Part II.: PMR spectra of halotoluenium and halobenzenium ions
Authors: Brouwer D. M. 
Published: September 2010

AbstractA number of halotoluenes and halobenzenes have been found to give stable benzenium ions in HF‐SbF5. The PMR spectra of these ions are reported. A mixture of all three possible stable cations was obtained with m‐chloro‐ and m‐bromotoluenes; of m‐fluorotoluene only two cations were formed in observable amounts. Likewise, both possible stable m‐dichlorobenzenium ions were observed, but only one m‐difluorobenzenium ion. Reversible line broadenings in the spectra of all these ions, and of 1,3,5‐trichlorobenzenium ion showed the occurrence of rapid intramolecular and/or intermolecular hydrogen exchange reactions at temperatures of 0° C or lower, depending on the cation. In the cases of o‐chloro‐ and o‐fluorotoluenium ions fast exchange reactions lead to coalesced signals at temperatures as low as −40° and 0°, respectively. Protonated fluoro‐benzene and chlorobenzene likewise give coalesced signals at −40°.
Amino‐substituted glyoximes and furoxans
Authors: Walstra P. , Trompen W. P. , Hackmann J. Th. 
Published: September 2010

AbstractThe preparation of some N,N′‐substituted diaminoglyoximes from dichloroglyoxime diacetate and primary and secondary amines, respectively is described.The oxidation of the fully substituted diaminoglyoximes leads solely to the corresponding furoxans.
Lead chromium sulfide, PbCr2S4, and some isotypic compounds
Authors: Omloo W. P. F. A. M. , Jellinek F. 
Published: September 2010

AbstractThe compounds PbCr2S4, SrCr2S4, BaCr2S4, EuCr2S4, SrCr2Se4 and EuCr2Se4 have been prepared and characterized. The compounds are isostructural with a hexagonal structure; the unit‐cell dimensions of PbCr2S4 are: a = 21.411 Å; c = 3.478 Å c/a = 0.1624. PbCr2S4 is a ferrimagnetic semi‐conductor with a Curie temperature of 138°K.
NMR of hydrogen fluoride in the gas phase
Authors: Mackor E. L. , Maclean C. , Hilbers C. W. 
Published: September 2010

AbstractNMR experiments in gaseous hydrogen fluoride are reported; somewhat surprisingly, both nuclei in the molecule give single lines instead of doublets, which means that rapid exchange reactions take place in the gas phase.Line widths for hydrogen are smaller than 30 c/s; for fluorine the line width increases considerably at lower pressures. It is concluded that the relaxation mechanism of the fluorine spins is spin‐rotational interaction. The chemical shifts of both hydrogen and fluorine are strongly dependent on the pressure. This behaviour is discussed in terms of association of HF vapour to predominantly cyclic hexamers. The chemical shifts of the hydrogen fluoride monomer and hexamer in the vapour are +4.35 ± 0.15 and −1.20 ± 0.15 for hydrogen and +14.0 ± 1.1 and −2.45 ± 1.1 ppm, respectively, for fluorine from liquid HF, corrected for bulk diamagnetic susceptibility.
On the reactivity of organophosphorus compounds: Part IV. The alkaline hydrolysis of some O‐phosphylated 2‐pyridine oximes
Authors: van Hooidonk C. , Kraaij G. W. , Ginjaar L. 
Published: September 2010

AbstractThe rates of alkaline hydrolysis of a number of O‐phosphylated 2‐pyridine oximes, C5H4NC(R1)NOP(O)R2R3, at different temperatures have been determined. The second‐order rate constants and the values of ΔH* and ΔS* are reported. Two parallel pathways of hydrolysis are observed: a nucleophilic substitution reaction on phosphorus (SN2P) generating the oxime and the parent acid and an elimination reaction of the Beckmann type (E2 or ElcB) producing the nitrile and the parent acid. The effects of the groups R1, R2 and R3 on the rates of substitution and elimination are discussed.
Properties of diazosulfonates: Part V. The effect of substituents on spectra and dissociation of 4‐dimethylaminobenzenediazosulfonate
Authors: van Beek L. K. H. , Boven J. , Helfferich J. 
Published: September 2010

AbstractThe absorption spectra of the substituted 4‐dimethylaminobenzenediazosulfonates in aqueous solution exhibit at least five bands in the region 210‐500 nm. Of these, the low‐intensity n → π* absorption is hidden in the π → π* band, which is found between 355 and 435 nm depending on type and positions of the substituents. A transition near 210 nm is assigned Φ → Φ*, which makes it likely that another band located in between the very intense Φ → Φ* and π → π* absorption is π → Φ*. The dissociation in aqueous solution is considerably reduced by substitution of electron‐attracting groups at positions 2 and 3 of the benzene ring. The overall dissociation constants of a number of mono‐ and di‐substituted benzene‐trans‐diazosulfonates were found to obey the Hammett equation with a reaction constant of 6.3 (± 0.2). The applicability of the Hammett equation indicates that the overall dissociation constant is proportional to that of the cis isomer.A general new method is given for the synthesis of a substituted 4‐dimethyl‐amino‐nitrobenzene from the relevant 4‐chloro‐nitrobenzene derivative.