bluuebunny/crossref_metadata_2025_split huggingface dataset:
Protonation of halogen‐containing benzenes in HF‐SbF5. Part I.: PMR spectra of fluoro‐, chloro‐ and bromomesitylenium and xylenium ions
Authors: Brouwer D. M. 
Published: September 2010

Abstract2‐Fluoro‐, chloro‐ and bromomesitylenes, and 5‐fluoro‐, chloro‐ and bromo‐m‐xylenes have been found to form stable benzenium ions in HF‐SbF5. The cations give well‐resolved PMR spectra, from which their structures have been derived. The 2‐halomesitylenes are “exclusively” protonated in the unsubstituted ring positions. The 5‐halo‐m‐xylenes give mixtures of two cations, with the captured proton ortho and para to the halogen, respectively, the preference for the para position increasing from Br to Cl to F.4‐Chloro‐m‐xylene and 2‐chloro‐p‐xylene give “stable” cations, which slowly rearrange to the 5‐chloro‐m‐xylenium ion. Protonation of 2‐ and 4‐bromo‐m‐xylenes at 0° yields instantaneously the 5‐bromo‐m‐xylenium ion, probably as the result of intermolecular reactions.A novel and facile synthetic route to 5‐bromo‐m‐xylene is described.
Adducts of thiophosphoryl compounds with metal halides. Part II: Addition compounds of thiophosphoryl chloride
Authors: van der Veer W. , Jellinek F. 
Published: September 2010

AbstractThiophosphoryl chloride is a much weaker donor towards metal chlorides than phosphoryl chloride. The only addition compounds of thiophosphoryl chloride that could be isolated in a pure state are Cl3PS · SbCl5 and Cl3PS · SO3; moreover, two adducts of PSCl3 with AlCl3 were obtained. AlBr3 reacts with PSCl3 with irreversible exchange of the halogen atoms; adducts are found as intermediates in this reaction. Infrared spectroscopy of the solid addition compounds of PSCl3 shows sulfur to be coordinated at the metal atoms. The adducts Cl3PS · SbCl5 and Cl3PS · SO3 decompose at about 120° and−10°, respectively, with formation of elemental sulfur. For comparison, adducts of phosphoryl chloride with SbCl5, AlCl3 and AlBr3 were also studied.
The nuclear magnetic resonance spectra of some substituted benzenes with D2h‐symmetry, in a nematic solvent
Authors: Bulthuis J. , Gerritsen J. , Hilbers C. W. , Maclean C. 
Published: September 2010

AbstractNuclear magnetic resonance spectra have been measured and interpreted of a number of substituted benzenes with D2h‐symmetry in the nematic phase of 4,4′‐di‐n‐hexyloxyazoxybenzene (1 p‐dichloro‐, 2 p‐dibromo‐, 3 p‐di‐iodo and 4 p‐difluoro‐benzene and 5 symm‐tetrafluorobenzene). The fine structure is caused by the average direct dipolar interaction between the spins and by the indirect couplings1‐3. The direct interactions are distance‐dependent meaning that the spectra are related to the molecular geometry. Thus ratios of proton‐proton distances have been calculated for molecules 1‐4 and molecular models have been designed with which the NMR spectra are in agreement.The liquid crystal NMR spectra allow of comparison of the direct interactions with the indirect interactions. If the sign of the former is known the sign of the latter can be inferred. Thus for symm‐tetrafluorobenzene J = ‐ 17.8 Hz, JFFp = + 11.1 Hz. For p‐difluorobenzene only the sign of the sum (J + JHFm) can be determined. Subject to the restriction that anisotropic contributions to the indirect couplings can be neglected its value is + 12.2 Hz. In symm‐tetrafluorobenzene the indirect coupling between fluorine spins in ortho position contain such anisotropic contributions; the anisotropy of the indirect coupling has, in part, been inferred from the experimental data.
Complexes with ligands containing nitrile groups: Part V: Metal(I) and metal(II) methyl cyanide complexes with tetrachlorometallate(III) anions
Authors: Reedijk J. , Groeneveld W. L. 
Published: September 2010

AbstractA number of complexes of the general formula M(CH3CN)+pn(M′Cl4)−p is reported. The anions are the tetrachlorometallates: BCl−4, AlCl−4, GaCl−4, InCl−4, TICI−4, and FeCl−4. The cations M are the monovalent cations: Li, Na, Cu, Ag, (C2H5)4N, and the divalent cations: Be, Mg, Ca, Sr, Ba, Mn, Fe, Co, Ni, Cu, Zn, Cd, Hg, and Pd. The cations are completely solvated by methyl cyanide in these complexes, except the tetraethylammonium salts and most of the sodium complexes.The compounds were synthesized in methyl cyanide by reaction of the metal chlorides with BCl3, AlCl3, GaCl3, InCl3, TlCl3 and FeCl3, respectively.A large number of complexes proved to be isomorphous from their X‐ray powder‐patterns. Information about the structure of the complexes was obtained from ligand‐field spectra, infrared spectra, and Mössbauer spectra. Structural information concerning the anions was obtained from far‐infrared spectra.
Studies on polypeptides VI: Synthesis of protected hexa‐ and octa‐peptide hydrazides related to the N‐terminal part of bovine pancreatic ribonuclease a using the solid‐phase method
Authors: Visser S. , Roeloffs J. , Kerling K. E. T. , Havinga E. 
Published: September 2010

AbstractMerrifield's solid‐phase method was applied to the synthesis of all‐L‐t‐butoxycarbonylthreonylalanylalanylalanyl‐Nϵ‐benzyloxycarbonyllysylphenylalanine hydrazide and all‐L‐Nα, Nϵ‐di‐t‐butoxycarbonyllysyl‐γ‐t‐butylglutamylthreonylalanylalanylalanyl‐Nϵ‐benzyloxycarbonyllysylphenylalanine hydrazide. Cleavage from the solid support with a solution of hydrazine hydrate in dimethylformamide and additional purification gave homogeneous products in high overall yields. Conventional syntheses of these compounds led to identical products.
The condensation of resorcinol with benzil
Authors: Bunn A. , Cudby M. E. A. , McGowan J. C. 
Published: September 2010

AbstractThe condensation of benzil and resorcinol is shown to give 3,8‐dihydroxy‐5a, 10b‐diphenylcoumarano‐2′, 3′, 2, 3‐coumaran.
Kinetics of rearrangements of methylbenzenium ions in HF
Authors: Brouwer D. M. 
Published: September 2010

AbstractRate constants and activation parameters of the following methylbenzenium ion rearrangements have been determined by direct measurement in HF containing SbF5: o‐xylenium and p‐xylenium to m‐xylenium, 1,2,3,4‐ to 1,2,3,5‐tetramethylbenzenium, 1,2,3‐ to 1,2,4‐ and 1,2,4‐ to 1,3,5‐trimethylbenzenium ions. The rate constants at 25° are 80, 335, 155, 8.9 and 1.4 × 10−5 s−1, respectively. The differences in rate of these rearrangements, which take place by successive 1,2‐hydrogen and methyl shifts with the latter as rate‐determining steps, are entirely due to differences in heat of activation, which varies from 19.8 to 23.3 kcal · mole−1, the activation entropy being about −3 cal · mole−1 · deg−1. These differences can be fully rationalized by considering the stabilities of the intermediate cations. Data on the relative stabilities of isomeric methylbenzenium ions are presented. In methylbenzenium ions the 1,2‐methyl shifts proper, the free energies of reaction of which vary from −6.5 to +6.5 kcal · mole−1, have free energies of activation of 15 to 22 kcal · mole−1, corresponding to rate constants of 35.5 to 0.00065 s−1 at 25°.
Syntheses of carotenoidal compounds IV carotene‐α, β‐dicarboxylic acids
Authors: Haeck H. H. , Kralt T. 
Published: September 2010

AbstractThe syntheses of some carotene‐α,β‐dicarboxylic acids by means of Stobbe condensations is described.According to the wavelengths of their absorption maxima in UV and visible light these compounds exhibit a high degree of steric hindrance.
Chemistry of 1,2‐di‐tert. Butylbenzene and derivatives: Part II. Hydrogenation of 1,2‐di‐tert.butylbenzene on platinum and rhodium catalysts. Synthesis of cis‐ and trans‐1,2‐di‐tert.butylcyclohexane
Authors: van de Graaf B. , van Bekkum H. , Wepster B. M. 
Published: September 2010

AbstractThe course of the hydrogenation of 1,2‐di‐tert.butylbenzene under the influence of rhodium and platinum catalysts has been investigated. Cis‐ and trans‐1,2‐di‐tert.butylcyclohexane and the intermediate product 2,3‐di‐tert.‐butylcyclohexene always appearing in the hydrogenations have been isolated and characterized. The rate of hydrogenation of 1,2‐di‐tert.butylbenzene has been compared with that of benzene and that of some 1,2‐dialkylbenzenes.
Complexes of some divalent metals with phosphorus oxychloride
Authors: Driessen W. L. , Groeneveld W. L. 
Published: September 2010

AbstractA series of new complexes is reported with phosphorus oxychloride as a ligand: viz., complexes of Mg(II), Ca(II), Sr(II), Mn(II), Co(II), Ni(II), Cu(II) and Zn(II). Reflection spectra in the visible and near infrared region indicate an octahedral configuration of the metal ion and the POCl3 molecules.
A rapid procedure for the preparation of [5‐3H]cytidine
Authors: Vaalburg W. , van Zanten B. , Buijze C. 
Published: September 2010

Abstract[5‐3H]Cytidine was obtained in a yield of 50‐60% by catalytic dehalogenation of 5‐iodocytidine with tritium gas. The isolation and purification of the [5‐3H]‐cytidine was accomplished in a single column chromatographic separation. The radiochemical purity of the final product was > 99%.
Oxidation products of 1‐phenylthiosemicarbazides and their antifungal activity
Authors: Pluijgers C. W. , Berg J. , Sijpesteijn A. Kaars , Tempel A. , Verloop A. 
Published: September 2010

AbstractThe appearance of an orange‐red colour in aged aqueous solutions of 1‐phenylthiosemicarbazide is ascribed to the formation of a red oxidation product, phenylazothioformamide.Another oxidation product, phenylazothioformamide‐S‐oxide, is obtained upon oxidation of 1‐phenylthiosemicarbazide with hydrogen peroxide in aqueous solution.Phenylazothioformamide, its S‐oxide, and certain of their substitution products are potent antifungal agents.They afford protection against certain plant diseases. In some cases phyto toxicity was observed.
Preparation, metallation and alkylation of allenyl ethers
Authors: Hoff S. , Brandsma L. , Arens J. F. 
Published: September 2010

AbstractPropargyl ethers HCCCH2OR [R = alkyl or‐CH(CH8)(OC2H5)] have been isomerized with good yields into the corresponding allenyl ethers CH2CCHOR by warming with potassium tert.‐butoxide at 70°.These allenyl ethers can be metallated with butyllithium in ether or alkali amides in liquid ammonia. In ether, subsequent alkylation with alkyl halides R′Hal affords α‐substituted allenyl ethers CH2CC(R′)OR. Alkylation in liquid ammonia produces a mixture of this same compound and the γ‐substituted product R′CHCCHOR. In both cases reasonable yields are obtained. Sodamide and potassium amide quickly convert allenyl ethers CH2CCHOR into metallated propargyl ethers MCC‐CH2OR (M = Na or K). If alkylation is not performed almost simultaneously with the metallation with sodamide or potassium amide, the only alkylation product obtained is R′CCCH2OR.
Complexes with ligands containing nitrile groups: Part VII. Metal‐ligand vibrations in methyl cyanide solvates
Authors: Reedijk J. , Groeneveld W. L. 
Published: September 2010

AbstractFar‐infrared spectra in the region 450‐150 cm−1 for a number of compounds of the type M(CH3CN)m (anion), have been investigated. Band assignments have been made with regard to the octahedral group M(NCC)6n+.Metal‐nitrogen stretching vibrations are shown to occur in the 200‐350 cm−1 region for most bivalent metal ions. The frequency order found for the transition‐metal ions is Mn < Fe < Co < Ni < Cu > Zn, in agreement with the general Irving‐Williams stability order. A comparison with metal‐ligand vibrations in solvates containing other ligands has also been made.
Quenching of triplets by iodo compounds: The photosensitized decomposition of iodoacetic acid
Authors: van Zwet H. 
Published: September 2010

AbstractBenzophenone triplets are rapidly quenched by HI and ICH2COOH. This effect is discussed in terms of external heavy‐atom spin‐orbital coupling.Benzophenone sensitizes the decomposition of ICH2COOH; the quantum yield of iodine release very much depends on the solvent, and benzophenone/2‐ propanol appears to be a favourable combination for high iodine yields. The heavy‐atom effect on the triplet state of benzophenone is ascribed to some π‐π* character of the n‐π* type excited state of the aromatic ketone. Phenanthrene and anthracene also sensitize the photodecomposition of iodoacetic acid, although the triplet state of anthracene is not high enough to supply all the energy required to break the C‐I bond; a concerted bond‐breaking bond‐forming process is therefore proposed.
1,1‐Dihydroperoxycyclohexane isolation and evidence of structure
Authors: Cosijn A. H. M. , Ossewold M. G. J. 
Published: September 2010

AbstractTwo different ways of preparing and isolating the hitherto unknown, crystalline 1,1‐dihydroperoxycyclohexane are described.In one route the gem‐dihydroperoxide is prepared by peroxidation of cyclohexanone with an excess of concentrated hydrogen peroxide in triethyl phosphate and subsequently isolated from the reaction mixture by column chromatography.In the second route the gem‐dihydroperoxide is formed by disproportionation of 1‐hydroperoxy‐1′‐hydroxydicyclohexyl peroxide and isolated by preparative thin‐layer chromatography.The peroxide has a melting point of approx. 47° ‐ 50°. It is sensitive to impact and friction and extremely hygroscopic. It tends to decompose during drying procedures.
Chemistry and spectroscopy in strongly acidic solutions. Part XVIII: Novel ring contraction of cyclohexenones via dicarbonium ions
Authors: Hogeveen H. 
Published: September 2010

AbstractA novel quantitative conversion of cyclohex‐2‐enone into 3‐methylcyclopent‐2‐enone in HF‐SbF5 solution is reported. The acidity dependence of the rate constant shows that the mechanism involves a protonated keto‐carbonium ion (dicarbonium ion) as an intermediate. Rate constants and activation parameters have been determined. The rate in FSO3H‐SbF5 is much lower than that in HF‐SbF5, which is compatible with the lower acidity of the former solvent system.Cyclohex‐3‐enone is also converted into 3‐methylcyclopent‐2‐enone, after initial isomerization to cyclohex‐2‐enone. This constitutes proof of a rapid equilibration between the cyclohexenones prior to the rate‐determining formation of 3‐methylcyclopent‐2‐enone.5‐Methylcyclohex‐2‐enone is converted into 3‐methylcyclohex‐2‐enone, which shows that hydride shifts in the intermediate dication are more rapid than the ring‐contraction steps.
Chemistry and spectroscopy in strongly acidic solutions. Part XX: Configurational equilibration in protonated formic acid and protonated acetic acid (dihydroxycarbonium ions): (Short communication)
Authors: Hogeveen H. 
Published: September 2010

AbstractIn a number of protonated organic molecules configurational isomerism around a partly double CO bond has recently been established2. We thought it of interest to determine the energy barriers of configurational equilibration around this bond (and similar partly double bonds), and to compare these experimentally determined activation energies with those calculated quantum‐mechanically3. For dimethoxymethylcarbonium ion this barrier was recently determined to be 11 ± 4 kcal · mole−1.
The use of the equal‐G curve in the interpretation of isobaric binary phase‐equilibrium diagrams
Authors: Oonk H. A. J. 
Published: September 2010

AbstractIt is shown that for the thermodynamic description of isobaric binary phase equilibria a convenient use can be made of the curve in the T,X‐plane representing the set of points of intersection of the curves for the Gibbs energy functions of the two phases. The relation of this curve, for which the name equal‐G curve is proposed, with the phase diagram is illustrated with the help of hypothetical systems. The applicability to practical cases is demonstrated on the basis of some experimental solid‐liquid equilibrium diagrams.
Some aspects of the solvolysis of 1‐phenylethyl chloride
Authors: de La Mare P. B. D. , Hall D. Muriel , Mauger Elizabeth 
Published: September 2010

AbstractThe rate of solvolysis of 1‐phenylethyl chloride has been followed both polarimetrically and titrimetrically in 60% and in 70% dioxan. The polarimetric rate exceeds the titrimetric rate, and the extent of racemisation decreases slightly with increasing water‐content of the medium. The effects of added salts (LiCIO4, NEt4CIO4, LiCl, and in less detail NaOH, and LiBr) have been examined; these results confirm the conclusion to be drawn from the discrepancy between the polarimetric and titrimetric rate coefficients, namely that ion‐pair intermediates are involved in this reaction. They suggest also that the first stage of solvolysis is slightly reversed by added chloride ions. The exchange of radiochloride into the organic chloride has also been examined, and is consistent with the above conclusion. The possibility that styrene is an intermediate significant in these solvolyses has been excluded.
Preparation and diastereoisomerism of four substituted epoxycyclopentanones
Authors: Heslinga L. , van Gorkom M. , van Dorp D. A. 
Published: September 2010

AbstractEpoxidation of 4‐acetoxy‐2‐(6′‐methoxycarbonylhexyl)‐2‐cyclopenten‐1‐one in alkaline medium yielded the two possible diastereoisomers of 2,3‐epoxy‐4‐hydroxy‐2‐(6′‐methoxycarbonylhexyl)‐1‐cyclopentanone. The structure and configuration of these compounds have been elucidated by first order analysis of the normal and spindecoupled proton magnetic resonance spectra. Both stereoisomeric epoxides can also be obtained via an alternative synthetic route by epoxidation of 2‐(6′‐carboxyhexyl)‐4‐hydroxy‐2‐cyclopenten‐1‐one. The separate cis and trans isomers of 2‐(6′‐carboxyhexyl)‐2,3‐epoxy‐4‐hydroxy‐1‐cyclopentanone are correlated with the stereoisomers of 2,3‐epoxy‐4‐hydroxy‐2‐(6′‐methoxycarbonylbexyl)‐1‐cyclopentanone by interconversion with diazomethane as well as by comparison of the proton spectra.
Isomerisation, alkylation and hydroxyalkylation of cumulenyl ethers
Authors: Selling H.A. , Rompes J.A. , Montijn P.P. , Hoff S. , van Boom J.H. , Brandsma L. , Arens J.F. 
Published: September 2010

AbstractIn dimethyl sulfoxide 1,2,3‐trienyl ethers RR′CCCCHOCH3 (with R and R′ = alkyl or RR′C = cyclohexyl) are isomerised by potassium tert‐butoxide, first to 1,2,4‐ and then to 1,3,5‐trienyl ethers. In the case of RR′C = cyclohexyl, thus with magnified image elimination of methanol takes place and further isomerisation finally leads to aromatisation to 1‐propenylbenzene. Acid hydrolysis of CH2 = C(CH3)CHC = CHOCH3 in dimethyl sulfoxide affords the aldehyde CH2C(CH3)CHCHCHO.The 1,2,3‐ and 1,2,4‐trienyl ethers have been metallated in the 1‐position by lithium amide and butyllithium, and subsequently alkylated or hydroxy‐alkylated.Recently 1,2,3‐trienyl ethers RR′CCCCHOCH3 have become available 1.The present paper describes some reactions with these compounds.
Etude de l'effet isotopique secondaire du deuterium dans la décomposition de la combinaison bisulfitique de la tertiobutyl‐4 cyclohexanone. Énergie conformationnelle du groupe SO3−
Authors: Lamaty G. , Roque J. P. 
Published: September 2010

AbstractThe rate constants for the hydrolysis of the bisulfite addition compounds of cyclohexanone, 4‐tert‐butylcyclohexanone and their α‐deuterated homologues have been measured.There is a large difference between the isotope effects observed for the cyclohexanone (kH/kD = 1.10) and the “slow” isomer from the 4‐tert‐butylcyclohexanone (‐ SO3− equatorial; kH/kD = 1.05). This result is discussed in terms of the existing difference between the geometries of the transition states.The conformational energy of the ‐ SO3− group has been determined and found to be equal to 2.25 kcal/mole.
Heterocyclic steroids XV. Synthesis of 13,14‐diazasteroidal systems
Authors: Pandit U. K. , de Jonge K. , Huisman H. O. 
Published: September 2010

Abstractβ‐Tetralone (Ia) and 6‐methoxy‐β‐tetralone (Ib) have been alkylatedviathe corresponding pyrrolidine enamines to their 1‐alkoxycarbonylmethyl derivatives IIIa and IIIb. Reaction of IIIa and IIIb with hydrazine hydrate gave benzo[f]cinnolones IVa and IVb, which were reduced with lithium aluminium hydride to tricyclic hydrazines VIa and VIc, respectively. Treatment of the latter with malonyl dichloride and triethylamine led to the formation of 13,14‐diazasteroids IXa and IXb. Condensation of IIIb with hexahydropyridazine (XIII) gave the D‐homo‐diazasteroidal system XIV in one step.
1,1‐dialkoxyalkyl alkane‐ and arene‐carboxylates. Part II. Synthesis of dialkoxymethyl esters and of 2‐acetoxy‐1,3‐dioxolanes
Authors: Scheeren J. W. , van Der Veek A. P. M. , Stevens W. 
Published: September 2010

AbstractDialkoxymethyl acetates and 2‐acetoxy‐1,3‐dioxolanes have been prepared from orthoformates and a “formic acid/acetic anhydride reaction system”. The rǒle of the “reaction system” is discussed. Other methods of synthesis of these acetates and other carboxylates are also described.
The formation of 1,2,4‐oxadiazoles from imidazoles by the action of hydrogen peroxide in alkaline solution
Authors: van Meeteren H. W. , van der Plas H. C. 
Published: September 2010

AbstractA hitherto unknown transformation of alkyl‐(aryl)‐imidazoles into alkyl‐(aryl)‐1,2,4‐oxadiazoles is described.
Synthesis of β‐alkyl and β‐aryl π‐allylic palladium halide complexes and its mechanistic aspects
Authors: Volger H. C. 
Published: September 2010

Abstractπ‐Allylic palladium halide complexes, substituted by an alkyl or aryl group at the central carbon atom, can be obtained in high yields in a one‐step synthesis by introducing the appropriate olefin into a sodium chloropalladite solution in glacial acetic acid in the presence of sodium acetate at 85°C.The reaction has been found to proceed via the π‐olefinic palladium complex, which is in equilibrium with small amounts of the π‐allylic complex according to:magnified imageAn equivalent amount of sodium acetate shifts the equilibrium completely to the right‐hand side.Specifically deuterated olefins can be obtained by dissolving the olefins in a solution of sodium chloropalladite in CH3COOD. Addition of sodium acetate after completion of the exchange affords the deuterated π‐allyl complexes.The scope of the reaction and the mechanism are discussed.
Synthesis and stability of tri‐sec‐aminomethanes
Authors: Scheeren J. W. , Nivard R. J. F. 
Published: September 2010

AbstractTri‐sec‐aminomethanes and dialkoxy‐sec‐aminomethanes can be obtained from chloroform sodium alkoxide and sec‐amines. The tri‐sec‐aminomethanes can be converted into tetra‐sec‐aminoethylenes by thermolysis. It appears that tri‐sec‐aminomethanes and tetra‐sec‐aminoethylenes have been mistaken one for the other more than once in the literature.Some interesting properties of the compounds synthesized are discussed.
Chemistry and spectroscopy in strongly acidic solutions. Part XXIV: Electrophilic substitution at alkanes
Authors: Hogeveen H. , Bickel A. F. 
Published: September 2010

AbstractA survey is given of the possible reactions between alkanes and protons or carbonium ions and in addition new kinetic data for some of these electrophilic aliphatic substitutions, including the hydrogen‐deuterium exchange in mono‐deuteroethane, and the cleavage of 2,2,3,3‐tetramethylbutane into isobutane and tert‐butyl cation. Comparison of present and former results shows that, when the proton is the electrophilic agent, electronic substituent effects predominate over steric effects. Electrophilic substitution at alkane‐carbon is likely to involve a retention of configuration, which implies a C8‐type geometry for the transition state.That the proton reactivity is lower in FHSO3‐SbF5 than in HF‐SbF5 is probably due to the lower acidity of the former solvent system.