bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ring transformations in reactions of heterocyclic halogeno compounds with nucleophiles (XIV): Conversion of 2‐substituted 4‐chloropyrimidines by potassium amide in liquid ammonia into 2‐substituted‐4‐methyl‐s‐triazines
Authors: van der Plas H. C. , Zuurdeeg B. 
Published: September 2010

AbstractUpon reaction with potassium amide in liquid ammonia 4‐chloro‐2‐(β‐naphthyl)‐, 4‐chloro‐2‐(N‐methylanilino)‐ and 4‐chloro‐2‐(N,N‐dimethyl‐amino)‐pyrimidines were converted into s‐triazine derivatives, while from 2‐anilino‐4‐chloro‐, 2‐benzyl‐4‐chloro‐ and 4‐chloro‐2‐(N‐methylamino)‐pyrimidines the corresponding 4‐amino compounds and no s‐triazines were obtained.The influence of the character of the substituent in position 2 of the pyrimidine ring on the reaction pathway chosen i.e. transformation into s‐triazines or conversion into 4‐aminopyrimidines is discussed.
Kinetics of the oxidation of phenylhydrazine and phenylhydrazinesulfonic acids. Part. I: Hexacyanoferrate(III) oxidations
Authors: Verwey A. M. A. , Jonker J. A. , Balt S. 
Published: September 2010

AbstractThe kinetics of the oxidation of phenylhydrazine and its sulfonic acids by the hexacyanoferrate(III) ion has been studied at constant temperature and ionic strength in 0.1 to 1 M aqueous perchloric acid. The reactions were first order in the ferrate and, apart from a small ion pairing contribution, also first order in the hydrazines. The dependence of the reaction rates on the hydrogen ion concentration could be explained by assuming a competition between the oxidation of the protonated and the unprotonated form of the phenylhydrazines. Due to the complicated nature of the interactions involved no clear picture of the ion pairing and the effects thereof on the reaction rates could be obtained.
Alkyltetrahydrofuryl and ‐pyryl cations: Formation by cyclization of protonated alkenones and transformations in different acids
Authors: Brouwer D. M. 
Published: September 2010

AbstractA PMR spectroscopic study has been made of the protonation of 1‐hexen‐5‐one (I), 2‐methyl‐l‐hexen‐5‐one (II), 2‐hepten‐6‐one (III) and 2‐methyl‐2‐hepten‐6‐one (IV) in different acids (HF, HF‐SbF5, H2SO4, FSO3H, FSO3H‐SbF5). With two exceptions, the first observable cations were alkyltetrahydrofuryl and/or alkyltetrahydropyryl cations. The cyclizations are very fast. Only in the case of I could the primary “stable” protonation product, the O‐protonated ketone, be observed below ‐ 40° in HF. Ketone IV gives a stable dication, C,O‐diprotonated IV, in the very strong acid HF‐SbF5.The heterocyclic cations derived from I and II are very stable. Those derived from III and IV give subsequent reactions, namely simple interconversion of five and six‐membered heterocyclic rings, skeleton isomerizations proceeding via acyclic dications, and in the case of the ions derived from IV the eventual formation of 1,3‐dimethylcyclohexenyl ion.The rates of all transformation reactions and the ratios of the products formed were found to depend strongly on the acid used. In the case of the skeleton isomerizations the rates depend on the acidity of the solvent (HF‐SbF5〉〉FSO3‐SbF5〉〉〉HF, H2SO4, FSO3H). For the other types of reactions the rates strongly vary with the type of solvent (HF versus H2SO4 or FSO3H).
Synthese und Biologische Eigenschaften der 8‐Mono‐ und 8,17,18‐Tri‐Ornithin‐β‐Corticotropin‐(l‐24)‐Tetracosapeptiden
Authors: Tesser G. I. , Rittel W. 
Published: September 2010

AbstractThis article describes the synthesis of two analogues of β‐corticotropin‐(l‐24)‐tetracosapeptide, in which the amidine function in one or in all three arginyl residues has been replaced by hydrogen.In connection with previous work, the weak biological) activity of both analogues proves the essentiality of a guanidine function in position 8 for hormonal activity.
The crystal structure of monochloroacetic anhydride
Authors: de Kok A. J. , Romers C. 
Published: September 2010

AbstractCrystals of monochloroacetic anhydride are monoclinic. The space group is P21/c and Z = 4. The unit‐cell dimensions are a = 5.20, b = 7.95, c = 16.88 Å and β = 100.4°.The structure was solved by application of a Buerger minimum function and refined by the method of least squares. The two C‐CO‐O fragments are planar and the angle between these moieties is 43°. The valency angle of the ether oxygen is unusually large with a value of 121°. The geometry of the molecule is given in terms of dihedral angles, the symmetry being approximately C2.
Isomerization of cyclic olefins in basic media. Part 4: The double bond migration of [14C]‐cyclopentene and [l‐14C]‐cycloheptene
Authors: Tjan S.B. , Steinberg H. , de Boer Th. J. 
Published: September 2010

AbstractThe base‐catalyzed double bond migration of [14C]‐cyclopentene and [1‐14C]‐cycloheptene has been studied in a solution of potassium tert‐butoxide in dimethyl sulfoxide at three temperatures. The activation parameters for cyclopentene are ΔH‡ = 22.1 ± 1.6 kcal/mole and ΔS‡ = ‐23.3 ± 2.6 e.u. and for cycloheptene ΔH‡ = 18.3 ± 0.5 kcal/mole and ΔS‡ = −24.5 ±0.8 e.u. It has been found that the isomerization rate increases with increasing ring size. This result is discussed in terms of angles between the planes formed by the bonds H‐C(allyl)‐C(olef.) and the nodal plane of the double bond.
Chemistry and spectroscopy in strongly acidic solutions. Part XXVI: Reduction of the norbornyl cation with molecular hydrogen. Ring opening of norbornane with protons
Authors: Hogeveen H. , Gaasbeek C.J. 
Published: September 2010

AbstractThe norbornyl cation is smoothly reduced to norbornane with molecular hydrogen; the rate of this reaction is about the same as that of the reactions of the tertiary butyl and adamantyl ions to the corresponding hydrocarbons. Reduction of the norbornyl cation with D2 affords undeuterated, mono‐, di‐, tri‐, tetra‐ and pentadeuterated norbornane.When norbornane is dissolved in HF‐SbF5 solution at room temperature an equilibrium mixture of methylcyclohexyl and 1,2‐ and 1,3‐dimethylcyclopentyl ions is formed. Reduction of this mixture with hydrogen, which occurs at the same rate as that of tertiary butyl ion, affords methylcyclohexane as the sole product, in agreement with its thermodynamic stability.
Aromatic sulfonation. Part 23: Sulfonation of p‐xylene in aqueous sulfuric acid
Authors: Kaandorp A.W. , Cerfontain H. 
Published: September 2010

AbstractThe rate of the homogeneous sulfonation of p‐xylene in aqueous sulfuric acid varying in concentration from 72 to 89% H2SO4 has been determined. Pseudo first order rate constants and apparent activation energies are reported as a function of the sulfuric acid concentration. The mechanism of the sulfonation of p‐xylene is briefly discussed.
Thermal rearrangement of 3‐ and 2‐(propargylthio)thiophene: Formation of the thiopyrans 5H‐thieno[3,2‐b]thiin and 6H‐thieno[2,3‐b]thiin
Authors: Brandsma L. , Bos H.J.T. 
Published: September 2010

Abstract5H‐Thieno[3,2‐b]thiin (III) and 6H‐thieno[2,3‐b]thiin (VI) are formed in excellent yields by heating solutions of 3‐ and 2‐(propargylthio)thiophene (I) and (IV), respectively, in hexamethylphosphoric triamide at 170–180°.
The photochemistry of bifluorenylidene
Authors: de Gunst G. P. 
Published: September 2010

AbstractProducts have been isolated and identified from two photochemical reactions of 9,9′‐bifluorenylidene (I). The photo‐oxidation of I yields 9‐fluorenone, the cyclodehydrogenation fluoreno(1,9a,9‐a,b)fluoranthene together with the reduced form of I, 9,9′‐bifluorene.
Dehydrohetarenes XVIII : Reactions of dibromopyridines with lithium piperidide and piperidine: (Preliminary communication)
Authors: Bos L. B. , den Hertog H. J. 
Published: September 2010

AbstractAnimations of the six dibromopyridines with lithium piperidide and piperidine in ethereal solution have been investigated. In boiling solution 2,6‐dibromo‐pyridine is converted into 2,6‐dipiperidinopyridine and both 3,4‐ and 3,5‐dibromopyridine give a mixture of 2,4‐ and 3,5‐dipiperidinopyridine. The other dibromopyridines yielded chiefly tarry products, 2, 4‐dibromopyridine together with some 2, 4‐dipiperidinopyridine, 2, 5‐dibromopyridine together with a small quantity of a mixture of 2,4‐ and 2,5‐dipiperidinopyridines.The mechanisms of these reactions are discussed. In this connection it was necessary to study the animations of five bromopiperidinopyridines too. Derivatives of 2,3‐ and 3,4‐dehydropyridine are assumed to be involved as intermediates in several replacement reactions.
The oxidation of methyl cyanide by vanadium(IV) chloride
Authors: van Driel C. A. A. , Groeneveld W. L. 
Published: September 2010

AbstractThe reaction products of VCl4 and excess CH3CN have been characterized by several methods. The main oxidation product is 2‐methyl‐4,6‐bis(trichloromethyl)‐1, 3, 5‐triazine.
Conformation of non‐aromatic ring compounds‐LIV: The calculation of dihedral angles from vicinal proton coupling constants in six‐membered ring compounds
Authors: Buys H. R. 
Published: September 2010

AbstractFor six‐membered ring compounds existing in solution as an equilibrium mixture of two equivalent conformers, and having a ‐ CH2 ‐ CH2‐ or a ‐ CH2 ‐CHR‐ moiety, the ratio of the vicinal coupling constants R = Jtrans/Jcis is expressed as a function of the ring dihedral angle ψ in that fragment. From the experimental coupling constants of a number of compounds the ψ values are calculated and compared with the corresponding dihedral angles obtained from X‐ray or electron diffraction data. In most cases the difference between the two results does not exceed 1‐2°.
Optical rotatory dispersion and absolute configuration XIII sedridine and allosedridine
Authors: Beyerman H. C. , Maat L. , Vlsser J. P. , Craig J. Cymerman , Chan Rosalind P. K. , Roy S. K. 
Published: September 2010

AbstractA method involving the combined use of ORD and CD is described by which both the relative and absolute configuration of the two asymmetric centres in amino alcohols, containing only the amino and hydroxyl chromophores, may be determined.Application of the method to both sedridine and allosedridine (resolved for the first time) is discussed.
A semi‐empirical energy‐level diagram for octahedral cobalt(II) complexes
Authors: Reedijk J. , Driessen W. L. , Groeneveld W. L. 
Published: September 2010

AbstractMethods of calculation for the parameters Dq and B from the ligand‐field spectra of octahedral cobalt(II) compounds are discussed. A method of calculation is introduced, which considers the lowering of the 4T1g (F) state by spin‐orbit splitting. This calculation is applied to the spectra of 43 octahedrally coordinated cobalt(II) compounds.With the aid of the spectral data an energy‐level diagram is constructed, into which the absorption bands are fitted.Comparison of calculated Dq and B values with corresponding values for isomorphous nickel(II) compounds shows that ‐ in general ‐ the crystalfield parameter Dq is highest for cobalt, although the differences with nickel are less than 4 % in most cases. The calculated B values corresponds with those of Ni, with differences less than 1 % for many ligands.
Alkylthiolation of ambident anions derived from some unsaturated organic sulfides
Authors: Wildschut G. A. , Brandsma L. , Arens J. F. 
Published: September 2010

AbstractReaction of the anions derived from 1,1‐bis(alkylthio)‐2‐alkynes RCCCH(SC2H5)2 (R = alkyl, vinyl or phenyl) with dialkyl disulfides R′SSR′ or alkyl alkanethiosulfonates R′SSO2R′ gives 1,1,3‐tris(alkylthio)‐1,2‐alkadienes RC(SR′) = C = C(SC2H5)2 in good yields. Alkylthiolation of CH3SC ≡ CC(SC2H5)2 with CH3SSCH3 affords (CH3S)2C = C = C(SC2H5)2. The 1‐alkynyl sulfides C2H5C≡CSC2H5 and CH3C≡CSCH3 have been converted into CH3C(SC2H5)=C=C(SC2H5)2 and (CH3S)2C = C=C(SCH3)2, respectively by reaction with alkali metal amide in liquid ammonia and dialkyl disulfide. The latter compound dimerises on heating. Tris(alkylthio)allenes R″CH2C(SR′)=C=C(SC2H5)2 isomerise to the conjugated dienes R″CH=C(SR′)‐CH=C(SC2H5)2 when heated in the presence of acids. Ethylthiolation of the anions of R′CH2C(R″)=C(SC2H5)2 (R″ = H or CH3; R′ = H, CH3 or SC2H5) gives predominantly R′CH=C(R″)‐C(SC2H5)3 as isolable products.
A chronopotentiometric study of the reduction behaviour of some complexes of copper(II), palladium(II) and rhodium(III)
Authors: Woodburn S. I. , Cardwell T. J. , Magee R. J. 
Published: September 2010

AbstractThe chronopotentiometric reduction behaviour of several complexes of copper(II), palladium(II) and rhodium(III) has been investigated at platinum and mercury electrodes. The aquo complexes examined were shown to undergo some dissociation before reduction at the mercury electrode.With the exception of the ethylenediamine system ligand adsorption was observed on the mercury pool electrode. As a result it was possible to calculate the degree of adsorption of some of the ligands.The rate constants for the reduction of the copper complexes were measured and found to follow the same order as the polarographic reduction potentials.
Solubilities of some alkali and tetraalkylammonium perchlorates in mixtures of water with methanol, ethanol, dioxane, acetone and acetic acid, and differences between the standard chemical potentials of these salts in their solutions in water and in the mixed or nonaqueous solvents, at 25°C
Authors: de Ligny C. L. , Bax D. , Alfenaar M. , Elferink M. G. L. 
Published: September 2010

AbstractSolubilities of some alkali and tetraalkylammonium perchlorates in mixtures of water with methanol, ethanol, dioxane, acetone and acetic acid have been determined conductometrically. From these solubilities the standard chemical potential differences for the transfer from water to the mixed or nonaqueous solvents have been calculated. In these calculations deviations from ideal behaviour caused by salt effects and ionic association have been taken into account.
Base‐induced 1,4‐eliminations with 3,4‐dialkoxy‐1, 2‐alkadienes: Formation of 3‐methoxy‐3‐alken‐1‐ynes
Authors: Hoff S. , Steenstra B. H. , Brandsma L. , Arens J. F. 
Published: September 2010

AbstractTreatment of 4‐ethoxy‐3‐methoxy‐1,2‐alkadienes H2C=C=C(OCH3)CH(R)OC2H5 (R = H or alkyl) with potassium amide in liquid ammonia affords 3‐methoxy‐3‐alken‐l‐ynes HC≡C‐C(OCH3)=CHR in excellent yields. The starting compounds can be obtained in good yields by reaction of α‐lithiated methoxypropadiene H2C=C=C(Li)OCH3 with α‐chloroethers ClCH(R)OC2H5.
Kinetics of the oxidation of phenylhydrazine and phenylhydrazinesulfonic acids. Part II: Oxidation by cationic iron(III) complexes
Authors: Verwey A. M. A. , Balt S. 
Published: September 2010

AbstractThe kinetics of the oxidation of phenylhydrazine and its sulfonic acids by cationic iron(III) complexes has been studied at constant temperature and ionic strenght in 0.1 to 1.0 M aqueous perchloric and hydrochloric acid. After correcting for associations, the reactions are first order in the iron(III) and the phenylhydrazines. Only the unprotonated phenylhydrazines are oxidized. All evidence points to an outer sphere mechanism for the reactions. Complex formation between metal ions (Fe3+, Mn2+, Ni2+) and the sulfonic acids seems to occur via the oxygen donor atoms of the sulfonic acid group.
Aromatic Sulfonation 26: Kinetics and mechanism of the sulfonation of some polyfluorobenzenes in fuming sulfuric acid
Authors: Kort C. W. F. , Cerfontain H. 
Published: September 2010

AbstractThe mechanism of sulfonation in oleum proposed by Brand et al. 3 ‐ stepwise attachment of SO3 and H+ to the substrate, followed by the loss of the proton from the benzene ring ‐ is shown to be inconsistent with the substrate isotope effects reported 3 by these authors. The sulfonation kinetics of p‐di‐, 1,2,3,4‐tetra‐, and penta‐fluorobenzene in 97‐109% sulfuric acid are discussed in terms of an extrapolation of the mechanism proposed recently 7 for aqueous sulfuric acid. In weak oleum — below 104% sulfuric acid — the rate‐limiting step ismagnified image
Chemistry and spectroscopy in strongly acidic solutions. Part XXVIII: Degenerate and non‐degenerate rearrangements of monocyclic C7H13⊕ ions
Authors: Hogeveen H. , Gaasbeek C. J. 
Published: September 2010

AbstractDegenerate isomerizations of methylcyclohexyl, 1,2‐dimethylcyclopentyl and 1,3‐dimethylcyclopentyl cations and reversible interconversions between these ions were studied by NMR line‐broadening. In addition, some classical kinetic measurements were carried out on the latter type of rearrangement. From the results the following conclusions can be drawn:
A course of non‐chain‐branching rearrangements (type‐A) as proposed for acyclic alkylcarbonium ions ‐viz. successive 1,2‐hydrogen and methyl shifts via secondary carbonium ions with the secondary‐secondary methyl shift as rate determining step ‐is consistent with the experimental data.
The impossibility of a parallel orientation of the empty p‐orbital and the CH or CC bond to be broken in type‐A rearrangements decreases the rate of this process compared with acyclic alkylcarbonium ions.
Also discussed is the remarkable stability of the monocyclic C7H13⊕ ions as compared with acyclic tert. heptyl ions.
Types of TX phase‐diagrams derived from Gibbs functions with the help of the equal‐g curve
Authors: Oonk H. A. J. , Sprenkels A. 
Published: September 2010

AbstractIt is shown that the derivation of the possible types of phase‐equilibrium diagrams can be performed in an elegant manner with the help of the equal‐G curve. Such a derivation is worked out, within the model of regular solutions, for the isobaric binary equilibrium between solid and liquid solutions. Attention is paid to the relation to the original derivation of Bakhuis Roozeboom and a remark is made about the obstacles encountered in the thermodynamical interpretation of phase diagrams. The thermodynamic excess functions are presented in the form of a series of sine terms.
The crystal structure of crassin p‐iodobenzoate
Authors: Hossain M. Bilayet , van Der Helm Dick 
Published: September 2010

AbstractThe crystal structure of crassin p‐iodobenzoate has been determined by the heavy‐atom technique and refined by the least‐squares method using three dimensional intensity data. The crystal is monoclinic with cell dimensions: a = 6.492 ± 0.002, b = 18.098 ± 0.006, c = 11.209 ± 0.004 Å, β = 97.1° ± 0.1°, with Z = 2; space group P21. The absolute configuration of the crassin molecule has been determined by using the anomalous dispersion of the iodine atom and the stereochemistry of the molecule has been confirmed. The molecule is found to consist of a 14‐membered cembrane ring fused with a δ‐lactone.
Complexes with ligands containing nitrile groups: Part XII. Metal(II) and metal(I) acetonitrile solvates with tetrabromometallate(III) anions
Authors: Reedijk J. , Vervelde J. B. , Groeneveld W. L. 
Published: September 2010

AbstractA number of solvates having the general formula M(CH3CN)m(M′Br4)n is reported. In this formula M = Cu(I), or one of the divalent ions Mg, Ca, Mn, Fe, Co, Ni, Cu, Zn, Cd; m is 4 or 6; M′ = Al, Fe, In, Tl; and n = 1 or 2.The compounds are prepared by bromide‐ion transfer reactions between MBr2 (or CuBr) and M′Br3 in anhydrous acetonitrile.Characterization and identification of these solvates were performed with the aid of chemical analyses, infrared spectra, ligand‐field spectra and X‐ray powder diagrams.The M′Br4− anions are demonstrated to be tetrahedrally co‐ordinated, whereas the M(CH3CN)62+ cations are octahedrally co‐ordinated with nitrogen as the donor atom of CH3CN.
Dithieno‐1,4‐thiazines. Part I
Authors: Grol C. J. , Faber J. S. 
Published: September 2010

AbstractThe synthesis of the first dithieno[2,3‐b : 2′,3′‐e]‐1,4‐thiazine is described, this compound was prepared by condensation of 3‐thiophenethiol with methyl 2‐bromo‐3‐nitrothiophene‐5‐carboxylate followed by reduction, acylation, bromination with NBS and ringclosure with Cu, K2CO3 in nitrobenzene.A thieno‐1,4‐benzothiazine was prepared in the same way. These compounds were synthesized in order to study the suggested correlation between charge‐transfer complexes vs. physiological activity.
C‐nitroso compounds. Part XIV: Oximes, nitroalkanes and alkyl nitrates by photolysis of C‐nitroso compounds and alkyl nitrites
Authors: Mackor A. , de Boer Th. J. 
Published: September 2010

AbstractMonomeric primary and secondary nitrosoalkanes have been generated from the trans‐dimers by heating in solution. The monomers are photochemically and thermally far more reactive than the dimers. They are isomerized to oximes in 90% yield thermally. Photolysis of nitrosocyclohexane with red light leads to the oxime in 60% yield. Photolysis in the presence of oxygen gives nitrocyclohexane as the main product (85%), together with a small amount of cyclohexyl nitrate.Considerable amounts of cyclohexanol are formed by oxidation of the solvent cyclohexane, presumably via a nitroxide‐type intermediate.When t‐butyl nitrite is photolyzed with light in the region of 400 nm and in the presence of oxygen in CFCl3, t‐butyl nitrate is produced in 90% yield, by the action of intermediary NO and NO2 radicals.
Chemistry and spectroscopy in strongly acidic solutions. Part XXX: Study of the carbonylation of carbonium ions by NMR spectroscopic measurements
Authors: Hogeveen H. , Baardman F. , Roobeek C. F. 
Published: September 2010

AbstractThe rate constants of the equilibrium R⊕ + CO ⇄ RCO⊕ have been determined by NMR spectroscopic measurements for R = t‐butyl. The rates and the activation parameters of the decarbonylation reaction are equal in HF/SbF5 (1: 1 molar ratio) and FHSO3/SbF5 (1: 1 molar ratio), while the second‐order rate constant of carbonylation is about a factor of 10 smaller in the former solvent system than in the latter.The equilibrium constant K = [RCO⊕ / [R⊕] [CO] was found to be only 15‐30 times as large for R = 2‐exo‐norbornyl and 1‐adamantyl as for R = t‐butyl and t‐pentyl. This is an indication of the unusually high stabilization of the norbornyl ion. The rates of the reactions of the carbonylation equilibrium are low for R = 2‐exo‐norbornyl, compared with those for R = t‐butyl, t‐pentyl and 1‐adamantyl, which is attributed to steric factors.
Conformation of non‐aromatic ring compounds. Part 61 Conformational equilibrium in trans‐2‐halogenocyclohexanols
Authors: Buys H. R. , de Vries H. J. A. , Hageman H. J. , Altona C. 
Published: September 2010

AbstractThe conformational equilibrium in trans‐2‐bromo‐ and trans‐2‐chloro‐cyclohexanol has been studied with the aid of dipole moments, NMR, IR and Raman spectroscopy. The physical properties of the individual conformers are obtained from the suitably biased 4‐ or 5‐t‐butyl derivatives. The diequatorial form appears to predominate strongly in solution. A comparison is made with the conformational features of the trans‐1,2‐dihalogenocyclohexanes.
The determination of the redundancy relations among the bending coordinates around a central atom
Authors: Ypenburg J. W. 
Published: September 2010

AbstractThe redundancy relations among the bending coordinates around a central atom have been derived to second order approximation by means of spherical trigonometry. The formalism derived here is not always applicable. A numerical result is more easily obtained by means of the formalism given here than in the generally applicable methods proposed by Crawford1 and Cihla and Pliva2.