bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spectroscopical investigations of olefinic compounds: Part II. An Infrared Method for the Cis/Trans Assignment of Trialkylated Ethylenes
Authors: Rummens F. H. A. 
Published: September 2010

AbstractWhen R2 ≠ R3, cis/trans isomerism exists in trisubstituted ethylenes R1HC = CR2R3. A previously1 described and tested concept of rehybridization makes possible the prediction of certain infrared frequency shifts as a function of sterical hindrance. In this paper it is shown that rehybridization accounts also reasonably well for certain frequency shifts of those tri‐alkylated ethylenes where cis/trans isomerism is absent. A number of rules are then developed which make possible the assignment of the cis or trans configuration when such isomerism is present.It is proposed that the cis/trans labelling of the National Bureau of Standards' standard samples of the 3‐methyl‐2‐pentenes and 3,4‐dimethyl‐2‐pentenes be reversed. The geranyl group is given the cis configuration and neryl the corresponding trans configuration, contrary to the hitherto accepted structures. The Δ4 (trans, Δ6 (7) (cis) structure has been assigned to the high‐boiling alloocimene and the all‐trans configuration to the corresponding low‐boiling isomer.
Energy data on the carbon‐carbon bond VI: Stability of ortho‐ethyl‐ and ortho‐isopropyl‐substituted diphenylmethyl radicals
Authors: Fleurke K. H. , Nauta W. Th. 
Published: September 2010

AbstractThe present investigation deals with the effect of the number of ortho‐ethyl and ortho‐isopropyl substituents on the stability of diarylmethyl radicals. These diarylmethyls were obtained by halogen abstraction from the correspondingly substituted benzhydryl chlorides.If not all ortho positions of the diarylmethyl carried ethyl or isopropyl groups, complete dimerization led to a symmetrical tetra‐arylethane; if all four positions were occupied by ethyl groups an equilibrium was reached between the radical and the dimer, while diarylmethyls with four ortho‐isopropyl groups showed no dimerization at all. Radicals of the last type were prone to disproportionation, however.
Studies in transition metal chemistry. Part III the oxidation of biscyclopentadienylvanadium compounds by oxygen and the synthesis of cyclopentadienylvanadium oxydichloride
Authors: de Liefde Meijer H. J. , van der Kerk G. J. M. 
Published: September 2010

AbstractCp2V and Cp2VR (Cp = πC5H5, R = alkyl or aryl) were found to react with atmospheric oxygen to give a product with the empirical formula C10H12O5V2. Evidence was obtained that in the oxidation product cyclopentadienyl rings π‐bonded to the vanadium atoms are present and that each vanadium atom is bonded to one such ring only. The formation of CpVOCl2 was found possible by three different methods: a) reaction of Cp2V with air and subsequently with thionyl chloride, sulfuryl chloride or acetyl chloride; b) chlorination of Cp2VCl2 followed by treatment with oxygen and c) reaction of VOCl3 with (C5H5)2Mg. The procedures a) and c) appeared useful for the preparation of CpVOCl2.
Charge‐transfer complexes of non‐coplanar derivatives of 4,4′‐dimethoxystilbene and of cis‐trans isomer pairs of substituted stilbenes
Authors: Laarhoven W. H. , Nivard R. J. F. 
Published: September 2010

AbstractCharge‐transfer absorption spectra of tetracyanoethylene complexes with a number of stilbene derivatives as donor molecules (1‐15, Table 1) have been measured in dichloromethane as solvent. Job tests showed that the complexes present in the solutions must be 1 : 1 complexes.All curves show two absorption maxima. The longest wavelength absorption band has been ascribed to a complex in which the complete stilbene molecule acts as the electron donor. Its position varies with increasing lack of coplanarity of the donor molecule. The other peak may belong to a configuration in which one of the aromatic rings in the stilbene molecule is the donating part. Values of the equilibrium constants (K) and extinction coefficients (ϵ) of the charge‐transfer complexes have been derived from Benesi‐Hildebrand graphs. A statistical analysis of the results has been given in the appendix. In the series of alkylated 4,4′‐dimethoxystilbenes (1–9) K decreases with increasing hindrance of coplanarity reaching a nearly constant value when the angle of twist of the phenyl nuclei in the stilbene component becomes large. Parallel to this decrease the character of the charge‐transfer absorption seems to change from complex to contact charge‐transfer.Finally the existence of linear relationships between ionisation potentials of donors or electron affinities of acceptors and vmax of their charge‐transfer absorptions has been tested.
Solvent dependence of 13CH and HH coupling in acetone and dimethyl sulfoxide
Authors: de Jeu W. H. , Gaur H. Angad , Smidt J. 
Published: September 2010

AbstractThe coupling constants J13CH and JHH for acetone and dimethyl sulfoxide were measured in a variety of solvents. J13CH for acetone was found to vary by up to 1.5% and JHH by up to 30%. The magnitudes of these variations are in almost linear relationship with the carbonyl 13C and 17O chemical shifts in the same solvent. A reason for this is sought in polar structures caused by the formation of hydrogen bonds and favoured by the polarity of the solvent. J13CH for dimethyl sulfoxide also varies with the solvent but JHH remains constant.
Steric effects of o‐methyl groups on the ionization constants of phenols and anilines
Authors: de Ligny C. L. , Kreutzer H. J. H. , Visserman G. F. 
Published: September 2010

AbstractThe values of the ionization constants of the phenols and anilines in water and water‐ethanol mixtures, determined by Gelsema et al.3, have been analysed for the presence of “o‐effects” by the method, devised by McDaniel and Brown7. It appeared that, contrary to the prevailing belief, in the phenol series an “o‐effect” is present, which is attributed to steric hindrance of hydration.The partition coefficients of benzene, toluene, the xylenes and the phenols and anilines derived from these hydrocarbons have been determined for the n‐heptane‐water system at 25°.Assuming that the standard free enthalpy of hydration, referred to the solution in n‐heptane, is in first approximation the sum of contributions of the hydrocarbon moiety and the ‐OH and ‐NH2 groups, respectively, the latter quantities (ΔG° ‐OH and ΔG° ‐NH2) have been calculated. An analysis for “o‐effects” showed them to be definitely present in the phenol series. In the aniline series the effect is so small that its significancy could not be proved.By combining the “o‐effect” on ΔG° ‐OH and ΔG° ‐NH2 (if real) with that on the ionization constants in water, the influence of steric hindrance of hydration by one o‐methyl group on the standard free enthalpy in aqueous solution could be calculated for the species R‐OH, R‐NH2, R‐O⊖ and R‐NH3⊕. The values obtained were 0.4, 0.1, 0.6 and 0.8 kcal/mole, respectively.Heinen's17 recent results on the association of phenols with acetone in carbon tetrachloride solution have also been explained in terms of steric hindrance of solvation by one o‐methyl group.
Organophosphorus compounds. II: Synthesis and cholinesterase inhibition of a series of alkyl and cycloalkyl methylphosphonofluoridothionates
Authors: Boter H. L. , Ooms A. J. J. 
Published: September 2010

AbstractA number of alkyl and cycloalkyl methylphosphonofluoridothionates were prepared by treatment of methylphosphonothioic difluoride with a mixture of one mole equivalent each of the appropriate alcohol and triethylamine in ether or benzene medium. Reaction velocities of the irreversible inhibition of acetylcholinesterase and butyrylcholinesterase were determined and compared with those of the corresponding phosphonofluoridates. A convenient method for the preparation of methylphosphonothioic difluoride is given.
Oxidation of cyclopropanone hydrate and hemiacetal by metal ions: (Preliminary communication)
Authors: Schaafsma S. E. , Steinberg H. , de Boer Th. J. 
Published: September 2010

AbstractThe isomerisation of cyclopropanone hemiacetal to propionic ester can be suppressed by metal ions such as Ag+ and Cu2+. These mild oxidising agents can lead to adipic ester (up to 80%) through dimerisation of a radical CH2CH2COOR (III) detectable by ESR. This radical is not formed via propionic ester, but by isomerisation of a cyclic radical II, the primary oxidation product of the hemiacetal. With ferric chloride the radical can pick up chlorine to form β‐chloropropionic ester.The reactions are equally facile with cyclopropanone hydrate leading to adipic acid and β‐chloropropionic acid.
Aromatic sulfonation XIV orientation in the homogeneous sulfonation oft‐butylbenzene in sulfuric acid
Authors: Arends J. M. , Cerfontain H. 
Published: September 2010

AbstractThe isomer distribution in the homogeneous sulfonation oft‐butylbenzene in 74.0‐103.0 wt‐% sulfuric acid has been determined at various temperatures.Ortho‐substitution does not take place. The degree ofmeta‐substitution is low under all conditions. The partial rate factors forpara‐ andmeta‐substitution in 86.3 wt‐% H2SO4at 25° are 53 ± 6 and 3.0 ± 0.3 respectively.Isomerization ofp‐ andm‐t‐butylbenzenesulfonic acids is relatively insignificant at temperatures below 110°.
Synthesis and physiological properties of some heterocyclic‐aromatic sulfides and sulfones. VI: Synthesis of some ring‐substituted aromatic‐heterocyclic ethene thioethers and their corresponding sulfones
Authors: Trompen W. P. , Huisman H. O. 
Published: September 2010

AbstractThe synthesis of some ring‐substituted aromatic‐heterocyclic ethene thioethers and their corresponding sulfones is described. The acaricidal activity and ovicidal action on eggs of Tetranychus urticae, Koch are reported.
A new distillation rate method for determining osmotic activity in dilute solutions, especially of highly reactive solutes
Authors: van Vulpen A. , Coops J. 
Published: September 2010

AbstractA new method is described for investigating the osmotic situation of nonvolatile compounds in various solvents with a concentration limit as low as about 10−3 mole/1. The method is based on measuring as a function of time the loss of weight of an evaporator made of porous material wetted with the pure solvent, hanging in the vapour of the solution under investigation. The gas‐free solution is injected by its own vapour pressure through a crystal‐seal in an evacuated glass apparatus, having no ground joints or valves. Calibration data are given.
On the synthesis of cephalosporin antibiotics. Synthesis of substituted furo‐oxathiins
Authors: Beyerman H. C. , Reinhoudt D. N. , Sinnema A. , van Veen A. 
Published: September 2010

Abstractβ‐Acetylthiomethyl‐α‐tetronic acid (4‐acetylthiomethyl‐3‐hydroxy‐2,5‐dihydrofuran‐2‐one, X) with the boron trifluoride complexes of (substituted) benzaldehyde(s) yielded 2‐aryl‐7‐oxo‐5,7‐dihydro‐4H‐furo[3,4‐e]‐1,3‐oxathiins (V). This new ring‐closure is discussed as a potential step toward a synthesis of the cephalosporin C antibiotics.The nuclear magnetic resonance spectra of the compounds V show that the long‐range spin‐spin coupling of protons “through vinyl” depends on steric factors.
Studies in homogeneous catalysis: The stepwise degradation of unbranched aldehydes to acetaldehyde and formate units by copper‐catalysed oxidation
Authors: Brackman W. , Gaasbeek C. J. , Smit P. J. 
Published: September 2010

AbstractStraight‐chain aliphatic aldehydes of at least three carbon atoms can be catalytically in methanol solutions of copper‐pyridine complexes and triethylamine by oxygen at 40 °C. In this oxidation the carbon atoms, starting with the carbon atom, are successively split off as methyl formate or formic acid, until the aldehyde is degraded to acetaldehyde, which is not reactive. The reaction probably proceeds via α‐ketoaldehydes.The oxidation of aliphatic ketones with the same catalyst system has been investigated.
Kinetics of the autoxidation of ethylbenzene
Authors: Altes F. W. Korthals , van den Berg P. J. 
Published: September 2010

AbstractA study was made of the kinetics of formation and decomposition of ethylbenzene‐hydroperoxide in the liquid phase. For a simplified mechanism, a first order decomposition of the hydroperoxide theoretically leads to an oxidation rate proportional to the square root of the hydroperoxide concentration. It is shown that only experiments at low concentration show this proportionality. At higher concentrations not all radicals originated by the thermal decomposition of the hydroperoxide cause chain branching. An extension of the mechanism is proposed and a mathematical form for the kinetics has been drawn‐up. Experiments with molecular oxygen at 120° are in agreement with this formula for the rate equation.
A one‐step replacement of aromatic amino groups by chlorine or bromine
Authors: Brackman W. , Smit P. J. 
Published: September 2010

AbstractA direct conversion of aromatic amines into the corresponding chloro compounds can be effected by the CuCl2‐NO complex:

CuBr2NO similarly leads to bromobenzene. The reaction proceeds at room temperature and can be applied to substituted anilines and aromatic diamines. The factors governing the yields are discussed.
Organophosphorus compounds. III: A new method for the preparation of alkyl methylphosphonofluoridates
Authors: Boter H. L. , van den Berg G. R. 
Published: September 2010

AbstractSome alkyl methylphosphonofluoridates were prepared by the reaction of the dicyclohexylamine salts of O‐alkyl hydrogen methylphosphonothioates with 2,4,6‐trinitrofluorobenzene in acetone solution. The mechanism of the reaction is discussed. The synthetic route was found to be useful for the synthesis of t‐butyl methylphosphonofluoridate, which is difficult to obtain otherwise. This compound decomposed quickly at 75°, yielding methylphosphonofluoridic acid and 2‐methylpropene.
The synthesis of ω‐functionalized 1‐adamantylalkanes
Authors: Hoek W. , Wynberg Hans , Strating J. 
Published: September 2010

Abstract2‐(1‐Adamantyl)thiophene can be easily carboxylated, formylated, acylated and nitrated, giving 2,5‐disubstituted thiophenes. Desulfurization furnishes the corresponding (1‐adamantyl)alkanes with a functional group at the ω‐carbon atom.
Friction coefficients and properties of polyelectrolyte membranes
Authors: Dorst W. , Staverman A. J. 
Published: September 2010

AbstractTransport through a polyelectrolyte membrane in aqueous binary electrolyte solutions is described by six constants, either six permeabilities Lik (with i, k = 1, 2, 3, including i = k) or friction coefficients fik (with i, k = 1, 2, 3, 4; i ≠ k). In a porous, selective membrane the friction of the co‐ion with the polymer matrix can be neglected, whereas the molecular friction coefficient of small ions and solvent approaches its free solution value. The required experimental information reduces to three independent measurements, for which electro‐osmosis, conductivity and co‐ion diffusion may be taken. A check on the fik values thus calculated is provided by expressing the ratio of electric transference numbers in friction quantities and comparing with experiment. The proposed device does not involve concentration averages; it is shown to be compatible with experimental data.
Syntheses and some reactions of aliphatic 1,2,3‐trienes
Authors: Montijn P. P. , Brandsma L. , Arens J. F. 
Published: September 2010

AbstractTrienes of the type R(R′)CCCCH2 (R and R′ are H or alkyl) have been prepared in good to excellent yields from 1,4‐dichloro‐2‐alkynes, R(R′)C(Cl)CCCH2Cl, and zinc dust or sodium iodide in dimethyl sulfoxide.The dichloro compounds were obtained from the corresponding 1,4‐dihydroxy‐2‐alkynes and thionyl chloride.The 1,4‐diols were synthesized from propargyl alcohol; the adduct of this alcohol and 2,3‐dihydropyran, , was coupled with an aldehyde RCHO or a ketone RR′CO (R and R′ are alkyl) under Grignard conditions. The resulting products R(R′)C(OH)CCCH2OT.H.P. (T.H.P. = tetrahydropyranyl) were treated with a catalytic amount of p‐toluenesulfonic acid in an excess of methanol, furnishing the diols R(R′)C(OH)CCCH2OH (R = H and R′ = alkyl or R and R′ are both alkyl) in good overall yields.Reaction of the cumulenes with equivalent amounts of alkali amide in liquid ammonia followed by hydrolysis of the reaction mixtures afforded the isomeric 3,1‐enynes, R(R′)CCHCCH, in good yields. Buta‐1,2,3‐triene, CH2CCCH2, and hexa‐1,2,3‐triene, CH3CH2CHCCCH2, were isomerized by sodium methoxide in liquid ammonia to the enynes vinylacetylene, HCCCHCH2, and hex‐2‐en‐4‐yne, CH3CHCHCCCH3, respectively. In the case of buta‐1,2,3‐triene also a considerable quantity of the 1,4‐adduct of methanol, 1‐methoxy‐2‐butyne, CH3CCCH2OCH3, was isolated.The addition of ethanethiol to buta‐1,2,3‐triene and hexa‐1,2,3‐triene proceeded readily, yielding mixtures of isomeric adducts, C2H5SCH2CHCCH2 and C2H5SCH2CCCH3, in the first case, and C2H5CH(SC2H5)CHCCH2, C2H5CH(SC2H5)CCCH3 and C2H5SCH2CHCCHC2H5, in the second case. These compounds lost ethanethiol when treated with alkali amide in liquid ammonia, the 3,1‐enynes, HCCCHCH2 and HCCCHCHC2H5, respectively, being produced.
Chemistry of propadiene. III. The addition of nitrosyl chloride to propadiene
Authors: Peer H. G. , Schors A. 
Published: September 2010

AbstractIn contrast to the addition of nitrosyl chloride to olefins, yielding chloronitroso addition products, the reaction of propadiene and nitrosyl chloride leads to the formation of 1,3‐dichloroacetone. The reaction sequence involved is discussed.
The crystal structure of tetragonal P4O6S4
Authors: Mijlhoff F. C. , Portheine J. , Romers C. 
Published: September 2010

AbstractThe crystals of P4O6S4 are tetragonal with space group \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm I}\bar 4{\rm c}2 $\end{document}. The unit cell with dimensions a = 9.065 and c = 13.55 Å contains four molecules with symmetry \documentclass{article}\pagestyle{empty}\begin{document}$ \bar{4}3 {\rm m} $\end{document} (Td) at positions 000, 00 ½, ½ ½ ½ and ½ ½ 0. The structure was solved by vector analysis and refined by the least‐squares method using CuKα reflexions (eye‐estimated and partly photometered data). The average PO and PS distances are 1.61 and 1.86 Å. The shape of the molecule and the packing are compared with those of analogous molecules.
Amino‐acid sequence study in peptides by mass spectrometry: Application of trideuteromethyl esters
Authors: Flikweert J. P. , Heerma W. , Penders Th. J. , Dijkstra G. , Arens J. F. 
Published: September 2010

AbstractCaproyl‐peptide methyl esters are suitable derivatives for mass spectro‐metrical analysis. Comparison of mass spectra of methyl esters of caproylpeptides with mass spectra of trideuteromethyl esters of the same compounds, allows easy detection of C‐terminal fragments. The spectra of ala‐gly, gly‐ser, val‐tyr‐pro and val‐lys‐val‐tyr‐pro were examined.
Kinetics of the isomerization of toluenesulfonic acids in aqueous sulfuric acid
Authors: Wanders A. C. M. , Cerfontain H. , Kort C. W. F. 
Published: September 2010

AbstractThe kinetics of the isomerization of the three isomeric toluenesulfonic acids have been studied at 140° in 68.7 and 74.0 wt‐% sulfuric acid.The isomer distribution in the sulfonation of toluene at this temperature and acid concentrations, has also been determined. The equilibrium mixtures contain mainly the meta‐ and para‐ and only small amounts of ortho‐isomer.The experimentally determined pseudo first‐order isomerization rate constants compare satisfactorily with the rate constants calculated from desulfonation rate constants and sulfonation isomer distribution data. This result is discussed in terms of an intermolecular isomerization mechanism.
Polymer gel structure elucidation by means of light scattering and photo‐elasticity
Authors: Donkersloot M. C. A. , Gouda J. H. , van Aartsen J. J. , Prins W. 
Published: September 2010

AbstractAmorphous polymer networks are commonly pictured as assemblies of randomly crosslinked coiling chains. The existence of more complicated structures in dilute (5%) and concentrated (50%) swollen polymer networks is, however, revealed by the present light scattering and photo‐elasticity study on polyvinyl alcohol and polyglycol methacrylate gels. On the basis of a Rayleigh‐Gans model of independent anisotropic scatterers, the light scattering data can be interpreted as resulting from rodlike orientation‐correlated regions of the order of 3λ. Although the model is certainly not unique, it is supported by the Mooney‐Rivlin type equilibrium stress‐strain and birefringence‐strain relations, which according to Volkenstein, Gotlib and Ptitsyn should indeed be found if the network is composed of coiling chains in which a number of rodlike aggregates are imbedded. Rodlike anisotropic regions may be formed as a result of segregation due to incompatibility with the diluent or as a result of micro‐syneresis. It is suggested that inhomogeneous crosslinking is largely responsible for the development of these structures.
The conformation of non‐aromatic ring compounds. Part 36: Comments on the Dipole Moments and Conformational Equilibria of Cyclic Sulfites
Authors: van Woerden H. F. , Havinga E. 
Published: September 2010

AbstractThe strong preference of the SO bond in trimethylene sulfite for an axial position (chair conformation), may not always prevent the molecules from occurring also in other conformations. A highly polar form having an equatorial SO bond may show up in polar solvents, due to a favourable interaction energy, and supported by e.g. an a → e change of a tert.‐butyl group.Closer examination of the electric moment of the sulfite group suggests that the lone‐pair of electrons on the sulfur contributes significantly to the overall moment. This interpretation provides a consistent description in terms of additive partial moments for the dipole moments of cyclic sulfites, thionyl chloride and related compounds.
Slow proton transfer in the nitration of anthracene; determination of the kinetic isotope effect of hydrogen in the nitration of naphthalene and anthracene with nitronium tetrafluoroborate
Authors: Cerfontain H. , Telder A. 
Published: September 2010

AbstractThe kinetic isotope effect of hydrogen in the nitration of anthracene with nitronium tetrafluoroborate has been determined, using anthracene‐9‐d as substrate. In sulfolane as solvent at 30° and in acetonitrile at 0°, kH/kD was found to be equal to 2.6 ± 0.3 and 6.1 ± 0.6, respectively. The kinetic isotope effect of hydrogen in the nitration of naphthalene in these two solvents under similar reaction conditions, using naphthalene‐1,4‐d2 as substrate, were found to be 1.15 ± 0.05 and 1.08 ± 0.05, respectively.UV spectral evidence was obtained that the nitration of anthracene with nitronium tetrafluoroborate in sulfolane as solvent proceeds via an intermediate which is suggested to be the 9‐nitro‐9‐anthracenonium ion. This intermediate is formed directly on mixing the reagents. The proton transfer from this intermediate with formation of 9‐nitroanthracene is a relatively slow process.
Organophosphorus compounds. Part V: The resolution of O‐alkyl hydrogen methylphosphonothioates with (+)‐ and (−)‐α‐phenylethylamine
Authors: Boter H. L. , Platenburg D. H. J. M. 
Published: September 2010

AbstractA series of four O‐alkyl hydrogen methylphosphonothioates, (RO)MeP(S)OH, was resolved using both (+)‐ and (−)‐α‐phenylethylamine. Because it gives better results, is rapid and of general applicability the method is to be preferred to that in which alkaloids are used as resolving bases. In one case optical purities of the isolated enantiomers were determined after conversion into acetylcholinesterase inhibitors.