bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optical activity of symmetrically substituted acetic acids. Part I: The stability against racemization of some ortho‐alkyl‐substituted diphenylacetic acids
Authors: Akkerman O. S. , Coops J. 
Published: September 2010

AbstractThe theoretically possible conformations of a substituted diphenylacetic acid and their interconversions are discussed. The activation parameters for the racemization of a series of ortho‐alkyl‐substituted diphenylacetic acids are determined.
Nuclear magnetic resonance studies in coordination chemistry. Part II: Kinetic studies of reactions occurring in the system [(π‐C4H7)PdCl]2‐triphenylarsine
Authors: Vrieze K. , Cossee P. , Hilbers C. W. , Praat A. P. 
Published: September 2010

AbstractAn NMR study has been made of the reactions occurring in systems which contain either the monomeric complex (π‐C4H7)PdCl(Ph3As) and the dimer [(π‐C4H7)PdCl]2, or only monomer and free triphenylarsine (in CDCl3). In the former case reactions were observed of Ph3As ‐ formed by the dissociation of the monomer (reaction (a)) ‐ with the dimer (b) and the monomer (c), respectively:

In the latter case, where only monomer and Ph3As are present, two reactions were studied. The first, which was observed between ‐70° and ‐40° with a very small excess of Ph3As, and which involves the exchange of Ph3As (reaction (c)), is first‐order in the arsine ligand. This reaction and the reactions in the presence of dimer were studied by measuring the rates at which the syn‐protons (or the anti‐protons) of the allyl group become magnetically equivalent. The second reaction, in which also exchange of Ph3As takes place, was measured between +10° and +80° with a higher excess of free Ph3As. This reaction is also first‐order in Ph3As, but involves the formation of either a s̀‐allyl intermediate or an activated state resembling the s̀‐allyl form. The activation energies and frequency factors of the above reactions are reported.At still higher excess of Ph3As (Ph3As/Pd ∼ 2‐3) an equilibrium (π‐C4H7)PdCl(Ph3As) + Ph3As ⇆ [(π‐C4H7)Pd(Ph3As)2]+Cl− becomes notticeable. This equilibrium moves to the right with increasing Ph3As/Pd ratio and decreasing temperature. The amount of ionic species, however, is so small that the kinetics of the above reactions are but little influenced by it.
The crystal structure of trispyridinecupriacetate
Authors: Anzenhofer K. , ten Rouwelaar L. N. A. 
Published: September 2010

AbstractThe crystal and molecular structure of the complex Cu(C5H5N)3(CH3COO)2 has been determined with three‐dimensional Patterson and Fourier methods. The copper is surrounded by two acetate and two pyridine groups, while the third pyridine molecule is not bonded to Cu at all. The arrangement of the nitrogen and the oxygen atoms around Cu is slightly but definitely non‐planar and tetrahedrally distorted.
Photolysis of dibenzyl sulfide
Authors: Laarhoven W. H. , Cuppen Th. J. H. M. , Nivard R. J. F. 
Published: September 2010

AbstractThe mixture of products formed by irradiation of dibenzyl sulfide has been analyzed by G.L.C. Dibenzyl and phenanthrene appeared to be the major products. In addition, several other products were characterized.Benzyl 1,2‐diphenylethyl sulfide was found to be a precursor in the formation of phenanthrene. The suggestion has been made that thermolysis of dibenzyl sulfide follows the same free radical mechanism as the photolysis.
Coupled and decoupled processes in the autoxidation of partially reduced pteridines and flavins
Authors: Mager H. I. X. , Addink R. , Berends W. 
Published: September 2010

AbstractOrganic hydroperoxide formation has to be regarded as the primary process in the autoxidation of partially reduced pteridines and flavins, to be distinguished from secondary oxidations and H2O2‐production. Material balances between oxidized products, O2‐uptake and H2O2‐formation have been determined under varying experimental conditions and found to be in agreement with a general formula based on the new theory. Spontaneous oxidation of a blocked dihydroalloxazine afforded a tetrahydroquinoxaline‐2‐spiro‐5′‐hydantoin as the ring‐contraction product of the transient hydroperoxide, confirming the structure previously proposed by us.
Comparison of X‐ and Q‐band ESR spectra of the ions CrOF52− and MoOF52−
Authors: Verbeek J. L. , Vink A. T. 
Published: September 2010

AbstractThe previously proposed model of Verbeek and Cornaz to account for the ESR‐spectra of the ions CrOF52− and MoOF52− was checked by measurements at two frequencies (X‐ and Q‐band) and by using central ion isotopes with different nuclear spins.The agreement with the theoretical expectations is satisfactory.
Hydrogen atom transfer from alkanes and aromatic proton complexes to aromatic cations and quinones
Authors: Buck H. M. , Oosterhoff L. J. , Sluys‐v. d. Vlugt M. J. v. d. , Verhoeven K. G. 
Published: September 2010

AbstractIn strongly acidic media alkanes react as hydrogen donating agents towards the positive radical ions of anthracene, perylene and tetracene. The aromatic radical ions appear to be converted into their related proton complexes. These proton complexes reduce quinones to hydroquinones. Qualitative data on the latter reaction are discussed in relation to its mechanism. A direct reduction of quinones by alkanes has not been observed.
Physical significance of activity coefficients of individual ions: The interaction of ions of organic acids and bases with the solvent and the influence of substitution by alkyl and phenyl groups
Authors: Alfenaar M. , de Ligny C. L. 
Published: September 2010

AbstractA study has been made of the influence of substitution by alkyl and phenyl groups in organic acids and bases on the interaction of the ions of these substances with the solvent.Knowledge of single ion activity coefficients is essential for the interpretation of the different effects.
Anticoagulants. Part II: Heterocyclic analogues of 4‐hydroxycoumarins
Authors: Kralt T. 
Published: September 2010

AbstractIn a search for compounds with anticoagulant activity analogues of 4‐hydroxy‐coumarin have been made in which the benzene nucleus has been replaced by thiophene. The compound 7‐hydroxy‐5‐thieno[3,2‐b]pyran‐5‐one (Ia) was obtained. From Ia two derivatives were prepared with substituents from known anticoagulants of the 4‐hydroxycoumarin group.
Cleavage of the carbon‐silicon bond in 1‐alkynylsilanes by silver nitrate: Protection of a terminal triple bond in hydrogenation reactions with the trimethylsilyl group
Authors: Schmidt H. M. , Arens J. F. 
Published: September 2010

AbstractIt is possible to reduce non‐terminal triple bonds in poly‐ynes selectively when the terminal triple bonds are previously protected silylation. Desilylation after the reduction can be easily effected with aqueous alcoholic silver nitrate.
The conformation of non‐aromatic ring compounds. Part 38 The chlorination of 1,4‐thioxane in carbon tetrachloride and the NMR analysis of 1,4‐thioxane, 1,4‐thioxene and some chloro‐substituted thioxanes
Authors: de Wolf N. , Henniger P. W. , Havinga E. 
Published: September 2010

AbstractA study has been made of the chlorination of 1,4‐thioxane under varying conditions, yielding mono‐, di‐, tri‐ and tetra‐chloro derivatives (cf. Fig. 1). Inspection of the NMR spectra of the compounds and fractions isolated leads to the following generalisations:Substitution of chlorine takes place preferentially at a carbon atom adjacent to the sulfur atom and, up to three chlorine atoms, in one half of the ring. The use of peroxide catalysts favours substitution adjacent to the oxygen atom.Of the compounds studied the following were found to occur as a conformational equilibrium, the two (half) chair conformations both being present to a substantial percentage: thioxane, 3,3‐dichlorothioxane (IIb), 2,2,3,3‐tetrachlorothioxane (IVc), thioxene, 3‐chlorothioxene (Ib), 3,5‐dichlorothioxene (IId). Except for the last one these compounds show a similar A2B2‐system due to the four protons at the unsubstituted side of the molecule. Conformationally fixed compounds such as 3‐chlorothioxane (Ia), trans‐2,3‐dichlorothioxane (IIc) and 2,3,3‐trichlorothioxane (IIIb) show an ABCD pattern due to the four protons in the unsubstituted half. Dipole moments have been determined and have been used in the conformational analysis of a few compounds.
Non‐enzymic conversion of all‐cis 8,11,14‐eicosatrienoic acid into prostaglandin E1
Authors: Nugteren D. H. , Vonkeman H. , van Dorp D. A. 
Published: September 2010

AbstractIt is shown that prostaglandin E1 is formed during autoxidation of all‐cis 8,11,14‐eicosatrienoic acid. However, the yield is low, which is due to the occurrence of many side reactions and the complex stereochemistry of the products. This non‐enzymic prostaglandin formation may give rise to artifacts in biological studies.
Heterocyclic Steroids. Part XI 1‐Hydroxy‐1‐vinylquinolizidine ‐ its synthesis, stereochemistry and attempted conversion to 5‐azasteroids
Authors: van Hes R. , Pandit U. K. , Huisman H. O. 
Published: September 2010

AbstractReaction of vinylmagnesium bromide with quinolizidine‐1‐one yielded a mixture of two stereoisomeric 1‐hydroxy‐1‐vinylquinolizidine systems (III and IV). Structural assignments of the latter are based upon infrared, nuclear magnetic resonance and mass spectral data. Attempts to transform the vinyl alcohols into 5‐azasteroids were unsuccessful.
Base‐catalysed elimination‐addition reactions of ethyl N‐(tosylmethyl)‐ or ethyl N‐(α‐tosylbenzyl)‐carbamates and ‐thiocarbamates
Authors: Olijnsma T. , Engberts J. B. F. N. , Strating J. 
Published: September 2010

AbstractBase‐catalysed elimination‐addition reactions of ethyl N‐(tosylmethyl)‐ or ethyl N‐(α‐tosylbenzyl)‐carbamates and ‐thiocarbamates were carried out with secondary aliphatic amines, thiophenol, methanol or the carbamate itself as nucleophilic reagents. The reaction with sodium borohydride has been investigated in two cases.
Bond lengths in diphenyloctatetraene
Authors: Olthof Roeli , Vos Aafje , Kracht D. 
Published: September 2010

AbstractThe crystal structure of all trans‐diphenyloctatetraene has been refined. The C‐C bond lenghts from previous work were confirmed. The experimental bond lenghts are compared with the values calculated by the Hückel method both with constant and variable β, and with those calculated by the approximate SCMO method for three sets of parameters. The discrepancies between the best theoretical bond lengths and the experimental values need not be significant.
The synthesis of lactones. Part III: δ‐Enollactones and lactones with exocyclic double bonds
Authors: Begemann P. Haverkamp , Lamberti V. , Weller W. T. 
Published: September 2010

AbstractA series of 4‐alken‐5‐olides has been prepared by dehydration of the corresponding 5‐oxoalkanoic acids. These enollactones are sensitive to both oxygen and moisture.For the synthesis of 9cis‐dodecen‐5‐olide, 4‐heptynylmagnesium bromide was coupled with cyclopentanone to form 1‐(4‐heptynyl)cyclopentanol, which was oxidized to 5‐oxo‐9‐dodecynoic acid. Two‐step reduction and dehydration yielded the lactone. Similarly, 5‐oxo‐6‐dodecynoic acid, prepared from 1‐heptynylmagnesium chloride and glutaric anhydride, was converted into 6cis‐dodecen‐5‐olide.6cis‐Dodecen‐4‐olide was synthesized by coupling 2‐octynylmagnesium bromide with methyl 4‐oxobutanoate to give methyl 4‐hydroxy‐6‐dodecynoate; this was converted into 6‐dodecyn‐4‐olide, which was partially hydrogenated. The product was separated gas‐chromatographically from the accompanying 5‐vinyl‐4‐decanolide.
Hydrogenation of hexamethylbicyclo[2.2.0]hexa‐2,5‐diene (hexamethyldewarbenzene)
Authors: Volger H. C. , Hogeveen H. 
Published: September 2010

AbstractHexamethylbicyclo[2.2.0]hexa‐2,5‐diene can be hydrogenated nearly quantitatively, with preservation of the bicyclic structure, to either the dihydro or the tetrahydro compound, depending on the reaction conditions. In both hydrogenation products the hydrogens are located in the exo position, as revealed by NMR spectroscopy. The corresponding dideutero compound was also prepared.Thermal isomerization of the dihydro product yields cis‐1,2,3,4,5,6‐hexamethylcyclohexa‐1,3‐diene quantitatively.
Aromatic sulfonation. Part XIX: Two mechanisms of sulfonation in aqueous sulfuric acid
Authors: Kort C. W. F. , Cerfontain H. 
Published: September 2010

AbstractThe dependence of the sulfonation rates and isomer distributions of several aromatic compounds on the sulfuric acid concentration is explained in terms of two reaction mechanisms. One involves H2S2O7 as the sulfonating entity and predominates at high sulfuric acid concentrations; the other, with H3SO4+ as the sulfonating entity, predominates at lower acid concentrations. The latter mechanism is more selective than the former.
Chemistry of acetylenic ethers. Part 89: The reaction of organolithium compounds with 1‐alkynyl ethers
Authors: Kooyman J. G. A. , Hendriks H. P. G. , Montijn P. P. , Brandsma L. , Arens J. F. 
Published: September 2010

AbstractDisubstituted acetylenes C4H9C≡CR are produced in the reaction of 1‐ethoxy‐1‐hexyne C4H9C≡COC2H5 with organolithium or Grignard compounds RLi or RMgBr. The yields are moderate to satisfactory. Ethoxyethyne HC≡COC2H5 and phenyllithium C6H5Li afford phenylacetylene HC≡CC6H5 (after hydrolysis) in moderate yield.The formation of acetylenes probably proceeds by an addition‐elimination mechanism.
Interrelation of thioethers containing conjugated systems with 6π‐electrons: (Base‐catalysed isomerisations in liquid ammonia)
Authors: van Boom J. H. , Brandsma L. , Arens J. F. 
Published: September 2010

AbstractThe present investigation deals with interrelations between thioethers of the types R1CH2CR2 = CH ‐C≡CSCH3 (3‐en‐1‐yne thioethers)R1CH = C(R2)CHC = CHSCH3 (1,2,4‐trienyl thioethers)R1CHC(R2)C≡CCH2SCH3 (4‐en‐2‐yne thioethers) andR1CH2CR2 = C = C=CHSCH3 (1,2,3‐trienyl thioethers). Under the influence of sodium ethoxide in liquid ammonia all compounds with R1=H are isomerised quantitatively into 3‐en‐1‐yne thioethers CH3 − C(R2)=CH‐C ≡ CSCH3, whereas the homologues with R1 = CH3 are quantitatively converted into a mixture of 1,2,4‐trienyl thioether and 4‐en‐2‐yne thioether. For further details see Table I.Treatment of our substrates with an excess of sodamide in liquid ammonia and subsequent hydrolysis always produces 1,2,4‐trienyl thioethers; 1,2,3‐trienyl thioethers are the presumed intermediates (Tables II‐V).The yields of the sodamide reactions are often rather low because of side‐reactions, among which polymerisation is included. Certain substrates suffer extensive loss of the thioether group by nucleophilic attack at sulfur (see Table II).In Appendix III a simple method for expressing the notation of unsaturated systems is developed; it is useful in drawing conveniently arranged diagrams depicting interrelations.
The crystal structure of glycerol and its conformation
Authors: van Koningsveld H. 
Published: September 2010

AbstractThe crystal structure of glycerol was determined by X‐ray analysis, with the aid of a direct method. Out of six possible staggered conformations of glycerol the structural investigation leads to the symmetrical aa‐conformation. This result is compared with the results of extended Hückel calculations supplemented by other considerations.
Conformation of open chain compounds. Part II: Dipole moments and conformational equilibrium of some vicinal dibromides, the “benzene effect”
Authors: Altona C. , Hageman H. J. 
Published: September 2010

AbstractThe dipole moments of some acyclic vicinal dibromides have been measured in carbon tetrachloride and in benzene. The gauche Br…. Br interaction energy is solvent dependent; its value in benzene is consistently 380 ± 30 cal/mole lower than in carbon tetrachloride.
Formation and structural assignments of four trimethylcyclopentadienes
Authors: de Haan J. W. , Kloosterziel H. 
Published: September 2010

AbstractThermolysis of isobornyl acetate in an inert gas atmosphere in a tube reactor, at temperatures between 420° and 480°C yields four trimethylcyclopentadienes as well as other compounds. Their isolation is described. Their structures were established by hydrogenation and by spectroscopic methods.A number of vicinal, allylic, homoallylic and long‐range coupling constants were obtained from the NMR spectra. The formation of 2,5,5‐trimethylcyclopentadiene from bornene is discussed.
Synthesis of N‐acetyl‐N‐(3‐amino‐2,4,6‐triiodophenyl)‐ β‐aminoalkanoic acids suited for use as oral cholecystographic agents
Authors: Korver J. A. 
Published: September 2010

AbstractThe reaction of m‐nitroaniline with α,β unsaturated acids like acrylic acid, methacrylic acid and crotonic acid gives N‐(m‐nitrophenyl)‐β‐aminoalkanoic acids which are converted to N‐acetyl‐N‐(3‐amino‐2,4,6‐triiodophenyl)‐β‐aminoalkanoic acids by successive acetylation, reduction and iodination.N‐Acetyl‐N‐(3‐amino‐2,4,6‐triiodophenyl)‐β‐aminoisobutyric acid* was found to be an excellent oral cholecystographic agent of low toxicity.
Conformation of non‐aromatic ring compounds.: Part 45. Carbon‐halogen stretching frequencies and conformation of 1‐alkyl‐1‐halogenocyclohexanes
Authors: Altona C. , Hageman H. J. , Havinga E. 
Published: September 2010

AbstractThe conformational properties of some 1‐alkyl‐1‐halogenocyclohexanes have been studied by infrared and Raman spectroscopy. Carbon‐halogen stretching frequencies were assigned to the possible conformations by comparing the observed values with those predicted by using the previously determined THHH, TCHH and TCCH frequencies.In solution, as well as in the neat liquid, the most stable conformation has the halogen atom in axial position. The side chain methyl group in 1‐ethyl‐1‐halogenocyclohexanes prefers to assume the gauche conformation with respect to the halogen atom.The dipole moments were measured in carbon tetrachloride and in benzene; no information about the equilibrium composition could be obtained by this method.
Acetylacetone as a ligand in nickel(II) perchlorate
Authors: van Leeuwen P. W. N. M. 
Published: September 2010

AbstractA new type of complex is described containing acetylacetone (acaH) as neutral ligand. Three compounds are described in detail [Ni(acaH)3](ClO4)2, [Ni)acaH)2(AcOH)2](ClO4)2 and [Ni(acaH)2(H2O)2](ClO4)2. AcaH is shown to be a fairly strong ligand also without the loss of its 3‐proton from the spectrochemical parameters Dq being 976 cm‐1 and B being 933 cm‐1. The infrared spectra and some near‐infrared absorptions are reported. It is tentatively proposed that the keto‐tautomer is present in the complexes.
Diffusion‐controlled stress relaxation in cross‐link density determinations, applied to ethylene‐propylene rubber
Authors: Knibbe D. E. 
Published: September 2010

AbstractOn stretching a rubber vulcanizate in an excess of solvent the degree of swelling will increase. It has been found possible to calculate the rate and extent of the increase in swelling from stress relaxation data. This method yields more accurate cross‐link density data than when the additional swelling is neglected, as is usually done.For ethylene‐propylene‐diene rubber in n‐heptane at 20°C a polymer/solvent interaction parameter of 0.42 ± 0.01 was found, irrespective of the degree of extension or amount of solvent present during the vulcanization within the ranges studied. Diffusion coefficients derived in this report are in accordance with literature data.
The standard chemical free enthalpy, enthalpy, entropy and heat capacity of hydration of the hydrogen ion, and the surface potential of water at 25°C
Authors: de Ligny C. L. , Alfenaar M. , van der Veen N. G. 
Published: September 2010

AbstractThe standard chemical free enthalpy, enthalpy, entropy and heat capacity of hydration of the H+ ion have been determined. The determination is based on a cyclic process in which the ferricinium ion and the ferrocene molecule are involved.No rather arbitrary divisions or long‐range extrapolations of thermodynamic data for electroneutral combinations of ions have to be made in this method. The accuracy of the values obtained, especially of the entropy, is high, and is determined mainly by the accuracy of the experimental data. For the first time an estimate of the heat capacity of a single ion is given.From the value of the chemical free enthalpy of hydration obtained and literature data on the real free enthalpy of hydration, the surface potential of water can be calculated.If 1 atm fugacity and 1 molal concentration are used as standard states in the gas‐phase and the aqueous solution, respectively, the following values are obtained (at 25 °C):
Interpretation of solubility data on the n‐alkanes and some other substances in the solvent water
Authors: Nelson H. D. , de Ligny C. L. 
Published: September 2010

AbstractData on the free enthalpy, enthalpy and entropy of solution in water for the n‐alkanes are interpreted, following the lines of the work of Némethy and Scheraga and of Pierotti.Solubility data for polar compounds are discussed on the basis of Butler's principle of additive contributions of the various constituent groups.
Electrochemical reduction of aza aromatics. Part I. Polarographic reduction of aromatic di‐aza compounds and correlation of results with H.M.O. calculations
Authors: van der Meer D. , Feil D. 
Published: September 2010

AbstractThe polarographic reduction of di‐aza compounds has been investigated in N,N‐dimethylformamide (d.m.f.) by two‐ and three‐electrode polarography with an Hg‐pool and Ag/AgCl in d.m.f. as reference electrodes, respectively. The i vs. V curves of the di‐aza compounds show that the reduction products are more sensitive to water than the negative ions of the comparable hydrocarbon aromatics. From the results obtained, we can conclude that, even with a water content less than 0.05%, protonated products are formed. This can also be concluded for the mono‐aza compounds from a critical examination of literature data. The E1 values obtained for the first wave have been found to fit the correlation with the energy of the lowest vacant π‐molecular orbital in the H.M.O. approximation.
Synthesis of DL‐Prostaglandin B1 and its reduction product DL‐prostaglandin E1‐237
Authors: Klok R. , Pabon H. J. J. , van Dorp D. A. 
Published: September 2010

AbstractCoupling of 3‐(2′‐tetrahydropyranyloxy)‐1‐octynylmagnesium bromide with 2‐(6′‐carboxyhexyl)‐2‐cyclopenten‐1‐one followed by Oppenauer oxidation and removal of the protecting group yielded crystalline DL‐2‐(6′‐carboxyhexyl)‐3‐(3′‐hydroxy‐1′‐octynyl)‐2‐cyclopenten‐1‐one. Hydrogenation of the latter substance in the presence of Lindlar's catalyst and subsequent elaidination gave DL‐2‐(6′‐carboxyhexyl)‐3‐(3′‐hydroxy‐1′‐trans‐octenyl)‐2‐cyclopenten‐1‐one ‐ shown to be identical with authentic PGB1 ‐ whereas hydrogenation in the presence of Pd on BaSO4 afforded DL‐2‐(6′‐carboxyhexyl)‐3‐(3′‐hydroxyoctyl)‐2‐cyclopenten‐1‐one known as PGE1‐237.
Intramolecular charge transfer in some donor‐acceptor molecules as N‐picrylauramine
Authors: Knoop F. W. E. , Buck H. M. , Oosterhoff L. J. 
Published: September 2010

AbstractIntramolecular charge transfer in picryl derivatives of benzophenonimide has been studied. Dipole moments and NMR spectra reveal that the contribution of charge transfer structures to the ground state is of minor importance in contrast with what could be expected. The discrepancy can be explained if a geometrical structure is assumed which closely resembles that of N,N‐diphenyl‐N′‐picrylhydrazyl.
Botrallin, a novel quinone produced by Botrytis allii
Authors: Overeem J. C. , van Dijkman A. 
Published: September 2010

AbstractBotrallin, a metabolic product of Botrytis allii, is shown to be a benzoquinone substituted with a methyl, a methoxyl and a 2‐carboxy‐3‐hydroxy‐5‐methoxy‐phenyl group.
The reaction of aldopentoses and secondary amine salts, a convenient method of preparing 4‐hydroxy‐5‐methyl‐2,3‐dihydrofuran‐3‐one
Authors: Peer H. G. , van den Ouweland G. A. M. , de Groot C. N. 
Published: September 2010

Abstract4‐Hydroxy‐5‐methyl‐2,3‐dihydrofuran‐3‐one was prepared from aldopentoses and secondary amine salts. A proposed mechanism for the reaction could be verified experimentally and led to reaction conditions giving an optimum yield.