bluuebunny/crossref_metadata_2025 huggingface dataset:
On the impedance of galvanic cells: XV. Evidence for the occurrence of Zn+ ions from d.c. and complex plane polarograms at the streaming zinc amalgam electrode
Authors: Ijzermans A. B. , Sluyters‐Rehbach M. , Sluyters J. H.
Published: September 2010

From d.c. and a.c. polarographic data of the reaction Zn++/Zn, especially from those obtained at a streaming amalgam electrode, it is concluded that this reaction may possibly be described as a one‐electron transfer step and a subsequent dismutation of the occurring univalent zinc ion. As regards the elucidation of mechanisms of electrode reactions, this method seems more informative in comparison with other methods.
The system CoSO4‐H2O; vapour pressure measurements from 0° TO 150°
Authors: Broers P. M. A. , van Welie G. S. A.
Published: September 2010

A systematic investigation has been carried out on the vapour pressure curves with the following result:

the quadruple‐point H7H6LG* lies at 44.7° ± 0.1 and 63.7 ± 0.3 mm Hg

the quadruple‐point H6H1LG lies at 64° ± 1 and 158 ± 5 mm Hg

The following three phase equilibria were defined as completely as possible between 3° and 150°: H7LG, H6LG, H1LG, H7H6G and H6H1G.

The following equations hold:

for the H6LG equilibrium: log pmm = ‐ 2173 ± 25/T + 8.646 ± 0.003

for the H7H6G equilibrium: log pmm = ‐ 2681 ± 25/T + 10.233 ± 0.008

for the H6H1G equilibrium: log pmm = ‐ 2679 ± 15/T + 10.148 ± 0.004

The following heats of hydration were calculated:

H6 + H2OL → H7 (25°): ‐ 1750 ± 110 cal/mol. H6

H1 + 5 H2OL → H6 (25°): ‐ 8680 ± 350 cal/mol. H1
Studies in group IV organometallic chemistry. XIX: The reaction of trialkyltin alkoxides with (thio)acylamides and (thio)carbamates
Authors: Noltes J. G.
Published: September 2010

The preparation and in particular the structure of nitrogen‐containing organotin compounds obtained by the reaction of triethyltin methoxide with a number of (thio)acylamides and (thio)carbamates are discussed.
Investigations on sterols XXVII: Synthesis of some stereoisomeric steroids and determination of the additional chemical shifts of the 18‐ and 19‐methyl protons
Authors: Halkes S. J. , Havinga E.
Published: September 2010

Additional chemical shifts of the 18‐ and 19‐methyl protons in four 9,10‐stereoisomeric steroid series are determined. Differences between the values derived for steroids with the 8β,9β,10α‐, the 8β,9β,10β‐, the 8α,9α,10α‐ and those with the natural configuration are discussed. The synthesis of some 9β‐steroid hormone analogues and of pregnanes and androstanes, isomeric at C‐8, C‐9 and C‐10, is described.
Studies on vitamin D and related compounds XIX: Optical rotatory dispersion of some 9,10,13‐stereoisomeric steroid 5,7‐dienes
Authors: Jacobs H. J. C. , Havinga E.
Published: September 2010

The rotatory dispersion curves of ergosterol and its three 9,10‐isomers (9β;10α;9β,10α) have been measured throughout the absorption band. The compounds show multiple Cotton effect curves in which the fine structure of the corresponding ultraviolet absorption band is reflected.

The identity of sign (positive) of the Cotton effects of 9β‐ and 10α‐ergosterol is ascribed to the presence of a boat conformation in ring C of the 9β‐isomer. The analogous 9β‐compound with 13α‐configuration, in which ring C can exist in the chair conformation, shows a Cotton effect of opposite sign in agreement with this hypothesis.
Oligomers of diphenylketene
Authors: Das H. , Kooyman E. C.
Published: September 2010

Diphenylketene (I) may be dimerized to form a. a cyclobutadione (IIa)1; b, a β‐lactone (IIb)2. Evidence is presented to suggest that a third dimer has the structure 1,3‐dioxo‐2,2,4‐triphenyltetralin (IIc). This compound reacts with (I) to produce a trimer (III), presumably the diphenylacetic ester of the enol form of IIc. Two compounds reported in the literature as diphenylketene dimers have been demonstrated to be 2,3‐diphenylindole and the ester, 2,3,4‐triphenylnaphthyl diphenylacetate.
Enthalpies of solvation of alkali halides in formamide. I: The enthalpies of solution of alkali halides in formamide
Authors: Somsen G. , Coops J.
Published: September 2010

The heats of solution of 18 alkali halides in anhydrous formamide at concentrations of about 0.01 molal and at 25° have been measured with an adiabatic calorimeter. Some physical properties of formamide have been determined. By applying the extended Debije‐Hückel theory the enthalpies of solution at infinite dilution were calculated. The difference in enthalpies of solution of the fluorides, chlorides, bromides and iodides, respectively, in water and in formamide appeared to be a constant, independent of the cation. An explanation in terms of van Eck's theory of ionic solvation is given.
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

When 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

The 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

Cp2V 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

Charge‐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

The 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

The 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

A 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

The 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

The 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

The 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

A 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.
Syntheses of carotenoidal compounds. II. Preparation of polyene‐(benzo)‐fulvenes
Authors: Haeck H. H. , Kralt T.
Published: September 2010

The preparation and spectra in visible light, of a number of fulvenes and benzofulvenes in the vitamin A series are described.
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

β‐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

Straight‐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

A 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.
Dihydroquinolones II
Authors: Speckamp W. N. , Huisman H. O.
Published: September 2010

The synthesis of several derivatives of 4‐oxo‐1,2,3,4‐tetrahydroquinoline and 4‐oxo‐1,2,3,4‐tetrahydrobenz[h]quinoline is described.
A one‐step replacement of aromatic amino groups by chlorine or bromine
Authors: Brackman W. , Smit P. J.
Published: September 2010

A 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

Some 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

2‐(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

Transport 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

Trienes 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

In 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

The 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

Caproyl‐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

The 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

Amorphous 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

The 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

The 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

A 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.
The mannich condensation of sulfinic acid with aldehydes and carboxamides, sulfonamides, or lactams. Part IV
Authors: Olijnsma T. , Engberts J. B. F. N. , Strating J.
Published: September 2010

The carboxamides, p‐CH3C6H4SO2CHR′NR″COR′″, the sulfonamides, p‐CH3C6H4SO2CHR′NR″SO2C6H5, and the lactams, magnified image, have been prepared by condensation of p‐methylbenzenesulfinic acid with an aldehyde and a carboxamide, a sulfonamide, or a lactam, respectively. The scope of the reaction is discussed. Infrared and PMR spectral data of the condensation products are given.
Triplet ESR spectra of some β‐diketone negative ions
Authors: Pijpers F. W. , van Willigen H. , Gerding J. J. Th.
Published: September 2010

A closed form lineshape formula is given for the characteristic ‘full field’ rigid matrix ESR signal of molecules existing in an electronic triplet state. The formula enabled a computer analysis to be made of the complex rigid matrix spectra produced by the alkali‐metal reduction products of some β‐diketones. It was concluded that the spectra consisted of the resonance signals of a monoradical and two dimerization products with triplet character.

The experimental data provided information on the structures of the two dimers and on the mechanism leading to their formation.
The determination of the standard potential of the silver‐silver bromide and the silver‐silver iodide electrode in a 87.68 wt% methanol‐water mixture and in 100% methanol
Authors: Alfenaar M. , de Ligny C. L. , Remijnse A. G.
Published: September 2010

The standard potential of the silver‐silver bromide and the silver‐silver iodide electrode in a 87.68 wt% methanol‐water mixture and in 100% methanol has been determined by comparison with the known standard potential of the silver‐silver chloride electrode in these solvents.

The potential of the silver‐silver bromide and the silver‐silver iodide electrodes appeared to be very sensitive to light.
Chemistry of sulfines. Part III: Further investigations on the preparation
Authors: Zwanenburg B. , Thijs L. , Strating J.
Published: September 2010

The preparation of sulfines by oxidation of thioketones is described. Thiobenzophenone‐S‐oxide (I) and 4,4′‐dimethoxythiobenzophenone‐S‐oxide (II) were obtained by oxidizing the corresponding thioketone with less than one equivalent of monoperphthalic acid. The oxidation of thiaxanthione appeared to give three types of sulfines, viz., IV, V, and VI, the formation of which was rationalized. Factors controlling the stability of sulfines are discussed and also the mechanism of the oxidation of the magnified image moiety with peracid. The alternative route to sulfines, viz., elimination of hydrogen chloride from sulfinyl chlorides, is described for thiofluorenone‐S‐oxide, thiobenzophenone‐S‐oxide and 2‐methoxynaphthalene‐1‐thial‐S‐oxide. In the latter case the originally published yield of 18% was increased to 63%. In addition to this sulfine the sulfinyl sulfone XI was isolated as a by‐product which loses sulfur dioxide on heating giving the sulfoxide XII.
The system phosphorus trichloride and boron trichloride
Authors: van Leeuwen P. W. N. M. , Groeneveld W. L.
Published: September 2010

The liquid‐solid diagram of PCl3 and BCl3 has been investigated. A 1: 1 addition complex was observed with melting point ‐ 94°. The liquids were completely intersoluble. The TC diagram and some characteristic cooling curves are given. Metastable phases (pure PCl3 or BCl3) frequently crystallized first.
Hydrolytic dissociation constants of substituted 4‐aminobenzoic acids
Authors: Los J. M. , Rekker R. F. , Tonsbeek C. H. T.
Published: September 2010

Composite hydrolytic dissociation constants, KI and KII, of 4‐aminobenzoic acids substituted as follows, 2‐H‐, 2‐CH3‐, 2‐Cl‐, 2‐Br‐, 2‐NO2‐, 2‐OH‐, 2‐OCH3‐, 3‐Br‐, 2,6‐(CH3)2‐, 2,6‐(C2H5)2‐, 2,6‐Cl2‐ and 2,6‐Br2‐, have been determined in aqueous solution, at 50°C and at an ionic strength of 0.1.

From the values of pKI and pKII and the postulate that the inductive effect of the 4‐NH3+ group on the dissociation of the 1‐COOH group is the same for all the acids studied, namely 0.54, all four individual pK values have been calculated for each acid as well as the fraction of zwitterion. After comparison of the individual pK values with the correspondingly substituted benzoic acids and anilinium ions, several conclusions could be drawn with respect to the configurational and energetic relationships between the acids.
Decarboxylation of substituted 4‐aminobenzoic acids in acidic aqueous solution
Authors: Los J. M. , Rekker R. F. , Tonsbeek C. H. T.
Published: September 2010

Rates of decarboxylation have been determined of the following substituted 4‐aminobenzoic acids 2‐H‐, 2‐CH3‐, 2‐Cl‐, 2‐Br‐, 2‐NO2‐, 2‐OH‐, 2‐OCH3‐, 3‐Br‐, 2,6‐(CH3)2‐, 2,6‐(C2H5)2‐, 2,6‐Cl2‐ and 2,6‐Br2‐ in aqueous hydrochloric acid solution (pH ranging from about 0 to about 2), at 50° and an ionic strength of 0.1 (except for the lowest pH values).

Analysis of the data in terms of a second‐order mechanism involves predominantly the species neutral ampholyte (notzwitterion) and hydronium ion for the range 0 < pH < 2. A general rate expression has been derived with the following features: (a) both (neutral) ampholyte and anion decarboxylation and (b) hydronium‐ion inhibition at lower pH. Essential to the mechanism is that the σ‐complex formed by addition of a proton at the C(1)position of the neutral acid cannot decarboxylate unless it first ionizes into the corresponding anion (loss of the carboxyl proton). The formation of the σ‐complex is not necessarily rate determining.

The reaction mechanism can explain not only all relevant facts concerning the acids investigated but also the data offered by the literature on substituted benzoic acids, in particular all available data on the13C‐carboxyl‐isotope effect and the (H2O, D2O)‐solvent‐isotope effect.
Chemistry of sulfines. Part IV: Reaction with halogens, tetrachloro‐ortho‐quinone, triphenylphosphine and water
Authors: Strating J. , Thijs L. , Zwanenburg B.
Published: September 2010

The addition of chlorine and bromine to 2‐methoxynaphthalene‐1‐thial‐S‐oxide (II) yields the dichloride and dibromide (IVa and b). The dichloride gives upon treatment with triethylamine 2‐methoxythionaphthoyl chloride‐S‐oxide (V). Similarly, thiobenzaldehyde‐S‐oxide (prepared in situ) was converted into cis‐ and trans‐thiobenzoyl chloride‐S‐oxide (scheme B).

Tetrachloro‐ortho‐quinone reacted with xanthione‐S‐oxide (IX) and thiofluorenone‐S‐oxide (I) yielding 1:1 adducts (X and XI) in which the α‐dioxo part of the quinone had acted as diene.

The reduction of the sulfine I with triphenylphosphine gave initially the thioketone, which reacted further with the phosphine as outlined in scheme D. The same reaction was carried out with the thial‐S‐oxide II.

The acid catalyzed hydrolysis of thioketone‐S‐oxides gave rise to the formation of the corresponding ketones (scheme E).
Hetarynes. Part XV: N‐oxides of 2,3‐ and 3,4‐pyridyne
Authors: Martens R. J. , den Hertog H. J.
Published: September 2010

The action of potassium amide in liquid ammonia on the N‐oxides of 2‐, 3‐ and 4‐bromopyridine, 3‐fluoropyridine, 2‐ and 3‐bromo‐4‐methylpyridine, 3‐ and 4‐bromo‐5‐ethoxypyridine and 3‐ and 4‐bromo‐2,5‐dimethylpyridine has been investigated.

3‐Fluoropyridine‐N‐oxide does not react under the conditions applied; the other N‐oxides yield mixtures containing one or two amino compounds. The mechanisms of the formation of these substances are discussed.

It was established that the SNAr2 (= AE) reaction is almost the sole reaction pattern in the aminations of the 4‐bromopyridine‐N‐oxides and one of the mechanisms occurring in the aminations of the 2‐bromopyridine‐N‐oxides.

The 2‐bromopyridine‐N‐oxides react partially and the 3‐bromopyridine‐N‐oxides exclusively via 2,3‐pyridyne‐N‐oxides as intermediates, except the N‐oxides of 3‐bromo‐2,5‐dimethylpyridine and 3‐bromo‐5‐ethoxypyridine in the aminations of which 3,4‐pyridyne‐N‐oxides play a role.
Chemistry and spectroscopy in strongly acidic solutions. Part IV: NMR Spectroscopic observation and structure of protonated aldehydes. Kinetics of deprotonation
Authors: Hogeveen H.
Published: September 2010

It has been shown by NMR spectroscopy that aldehydes dissolved in HF‐BF3 are completely protonated at −80°. The extreme low‐field chemical shift of the added proton demonstrates that the carbon‐oxygen bond in these protonated aldehydes remains largely a double bond. At higher temperatures deprotonation by fluoride anions takes place. Line‐broadening measurements showed this process to be diffusion‐controlled.
Complexes of ligands containing S = O. Part III Tetramethylene sulfoxide and pentamethylene sulfoxide; Jahn‐Teller effect in infrared spectra
Authors: van Leeuwen P. W. N. M. , Groeneveld W. L.
Published: September 2010

Inorganic complexes of two cyclic sulfoxides viz. tetramethylene sulfoxide and pentamethylene sulfoxide are reported. The hexasulfoxide metal complexes are identified by their analyses, melting points, X‐ray powder patterns and infrared spectra. The shifts in the S = O stretching frequencies in the complexes can be qualitatively related to the electron negativities of the metal ions. The infrared spectra of the complexes of Cu(II) show two separated S = O stretching frequencies in the solid state. The Cu(II) complexes are isomorphous with hexasulfoxide complexes of other metal ions, which have only one S = O frequency. The splitting of the band in the Cu(II) complexes is probably caused by tetragonal distortion.
On the preparation of allenes from propargyl bromide and Grignard compounds: (Short communication)
Authors: Brandsma L. , Arens J. F.
Published: September 2010

Arguments are brought forward to disprove the intermediacy of carbenes and to support an SN2′ mechanism for the formation of allenes from propargyl bromide and Grignard compounds.
Chemistry and spectroscopy in strongly acidic solutions. Part IX: Configurational preference in protonated carboxylic acids. Kinetics of reversible alkyl oxocarbonium ion formation
Authors: Hogeveen H.
Published: September 2010

Protonation of aliphatic carboxylic acids RCOOH in HF‐BF3 solution at low temperature leads to dihydroxycarbonium ions. The configurations as regards the groups R and H at the partly double magnified image bonds depend on the steric requirements of group R: In the case of RCH3, CH2Cl, CH3CH2 and (CH3)2CH both a cis‐ and a trans‐configuration, and in the case of R(CH3)3C two trans‐configurations probably exist.

The rate constants of the dehydration of the protonated acids to acyl cations that takes place at higher temperatures proved to vary only slightly for RCH3, CH3CH2, (CH3)2CH and (CH3)3C. In agreement with previous work on protonated formic acid the rates were found to be much lower in HF‐BF3 than in sulfuric acid solution (as estimated from Deno's results), possibly due to a difference in molecularity of the reaction.
Chemistry and spectroscopy in strongly acidic solutions. Part X: Formation, structure and decomposition of hydroxy‐alkoxy‐carbonium ions
Authors: Hogeveen H.
Published: September 2010

The quantitative conversion of some esters into the corresponding hydroxyalkoxy‐carbonium ions by protonation in HF‐BF3 solution at about −80 °C is reported. The probable configuration of the ions is deduced from NMR spectroscopic information. The decomposition route of these carbonium ions at higher temperatures depends on the species involved.
Aromatic sulfonation. Part XVIII: Ortho‐substitution in the sulfonation of monoalkylbenzenes with sulfuric acid
Authors: de Vries H. , Cerfontain H.
Published: September 2010

The degree of ortho‐substitution in the sulfonation of toluene, ethylbenzene and isopropylbenzene with sulfuric acid varying in concentration from 80.6 to 98.5% H2SO4 at 25° was determined. For a given sulfuric acid concentration the ratio of ortho‐ to (para‐ + meta‐) substitution decreases with increasing size of the alkyl group, whereas for a given alkyl group this ratio decreases with decreasing sulfuric acid concentration.

Partial rate factors for the homogeneous sulfonation of toluene, ethylbenzene, isopropylbenzene and t‐butylbenzene in 86.3% sulfuric acid at 25° were calculated. The partial rate factors for ortho‐substitution decrease with increasing size of the alkyl group, while those for para‐substitution follow the Baker‐Nathan order.

Introduction of a sulfonic acid group ortho to the alkyl group of an alkylbenzene can be effected with weak oleum (∼ 16%) as reagent under conditions of disulfonation with toluene, ethylbenzene and isopropylbenzene, but not with t‐butylbenzene.
Anticoagulants. Part I: Synthesis of 2,3‐disubstituted 1,4‐naphthoquinones and 4‐hydroxycoumarins
Authors: Kralt T. , Bots J. P. L. , Moed H. D. , Ariens E. J.
Published: September 2010

In a search for anticoagulants a number of 2,3‐di‐substituted 1,4‐naphthoquinones and 4‐hydroxycoumarins have been synthesized by allowing alcohols to react with 2‐substituted 1,4‐naphthoquinones and 4‐hydroxycoumarin. Some reflections are given on the mechanism of the reaction.
Properties of diazosulfonates. Part III: The absorption spectra of p‐substituted‐benzene‐trans‐diazosulfonates
Authors: van Beek L. K. H. , Helfferich J. , Houtman H. J. , Jonker H.
Published: September 2010

Benzene‐trans‐diazosulfonate has in aqueous solution well‐defined absorption bands at 219, 290 and 416 nm, which are compared with similar bands in the absorption spectra of other azo‐compounds. The bands at 290 and 416 nm are the π→π* and n→π* absorptions, respectively. The band at 219 nm (229 in azobenzene) is assigned as π ‐ Φ*. The Φ ‐ π* band appears to be buried in the π ‐ π* band and lies at approximately 255 nm. It follows from these assignments that the Φ→Φ* band should be situated at 198 nm. The spectra of benzenediazosulfonates do indeed show a steep rise in absorption at wavelengths below 210 nm. The effects of para‐substitution on the observed bands is discussed. The π→π* and the π→Φ* bands show bathochromic shifts as the electron‐donating power of the substituent increases.
Isomerization of conjugated and cumulated systems
Authors: van Dongen J. P. C. M. , de Jong A. J. , Selling H. A. , Montijn P. P. , van Boom J. H. , Brandsma L.
Published: September 2010

Various compounds with the system and have been converted into conjugated trienes by means of potassium tert‐butoxide in dimethyl sulfoxide (DMSO). Aromatization has been observed with compounds possessing the systems:magnified image
Complexes with ligands containing nitrile groups. Part III. Infrared spectra of coordinated methyl cyanide
Authors: Reedijk J. , Zuur A. P. , Groeneveld W. L.
Published: September 2010

Infrared spectra are reported of methyl cyanide coordinated to the monovalent cations, Li, Na, K, Rb, Cu, Ag, Au, Tl and the divalent cations, Be, Mg, Ca, Sr, Ba, Mn, Fe, Co, Ni, Cu, Zn, Cd, Pd, in complexes of the types M (CH3CN)pn+ (SbCl6)n‐ and M (CH3CN)pn+ (SnCl6)n/22−.

The shifts in the different bands are discussed. Metal ions are placed in a series of electronegativity towards methyl cyanide. The sequence is compared with ionization energies of the metals, and with other measures of metal electronegativity.
Sulfur compounds in free radical reactions. Part II: Thermal decomposition of arenediazothiolates
Authors: van Zwet H. , Kooyman E. C.
Published: September 2010

Arenediazothiolates (Ar‐NN‐SR; R  alkyl or aryl) undergo homolysis on heating. This follows from substituent and solvent effects on decomposition rates; product formation is interpretable on a homolytic basis. Substituent as well as solvent viscosity effects suggest that the primary step consists in the formation of a radical pair \documentclass{article}\pagestyle{empty}\begin{document}\[\left({\rm{Ar}-{\rm N}_2^\bullet+{\rm RS}^\bullet}\right)\]\end{document} rather than multiple fission \documentclass{article}\pagestyle{empty}\begin{document}\[\left({\rm{Ar}-{\rm N}_2^\bullet+{\rm RS}^\bullet}\right)\]\end{document}. In contrast to the situation at high concentration hardly any induced decomposition takes place at the low concentrations used for kinetics.
The crystal structure of NOSO3Cl
Authors: Höhle Th. , Mijlhoff F. C.
Published: September 2010

NOSO3Cl forms monoclinic crystals with space group P21/c. The unit cell with dimensions a = 8.997 Å, b = 7.101 Å and c = 7.557 Å, β = 109.80°, contains four molecules, all atoms are in general fourfold positions. The structure was solved by vector analysis and fourier synthesis, followed by a least squares refinement using photometered CuKα reflections. Discrete NO+ and SO3Cl− ions are present. The SO3Cl− ion has C3v symmetry. The S‐Cl distance is 2.05 Å, the S‐O distance 1.43 Å. The very short N‐O distance found (0.94 Å), is explained by estimating a correction (0.09 Å) to the mean separation of the atoms from their thermal motions.
Pyrazoles. Part IV Effects of solvents and steric effects on UV and PMR spectra of 4‐phenylpyrazoles
Authors: Cohen‐Fernandes Pauline , Habraken Clarisse L.
Published: September 2010

UV and PMR spectra of 1‐methyl‐4‐phenylpyrazoles indicate the existence of conjugation between the phenyl and pyrazole rings. The UV spectra are found to be solvent dependent. This solvent effect can be explained, if considerable resonance interaction is assumed.
The conformation of allyldicyclopentadienyltitanium (III) complexes
Authors: Helmholdt R. B. , Jellinek F. , Martin Hendrik A. , Vos Aafje
Published: September 2010

The structure and conformation of allyldicyclopentadienyltitanium(III), (C5H5)2TiC3H5, and of some homologues substituted in the allyl ligand (mainly by methyl groups) have been investigated. Chemical arguments and infrared spectroscopy indicate that the allylic ligands are π‐bonded to the metal and that substituents at carbon atoms 1 and 3 of the allyl group preferably occupy the syn‐position. These conclusions are confirmed by an X‐ray diffraction study of the 1,2‐dimethylallyl complex. The carbon atoms 1, 2, 3 of the allyl group have distances of 2.34, 2.43 and 2.35 Å from the metal; the plane of the allyl group makes an angle of 56° with the line connecting the centre of this group with the metal. The methyl substituents are tilted (by 0.16 and 0.17 Å) out of the plane of the allyl group towards the metal.
Chemistry and spectroscopy in strongly acidic solutions. Part XII Imino‐15N ethylcarbonium ion: NMR spectroscopic identification and rate of deprotonation
Authors: Hogeveen H.
Published: September 2010

Protonation of propionitrile‐15N leads to formation of the imino‐15N ethylcarbonium ion, which according to its NMR spectrum occurs in one configuration only. Chemical shifts and coupling constants have been determined at some temperatures.

Line‐broadening measurements of the low‐field 15N‐H doublet show that the deprotonation of the imino‐15N ethylcarbonium ion by fluoride anions in hydrogen fluoride‐boron trifluoride solution is diffusion‐controlled.