bluuebunny/crossref_metadata_2025 huggingface dataset:
Enthalpies of solvation of alkali halides in formamide. III.: Structural considerations
Authors: Somsen G.
Published: September 2010

Experimental ionic enthalpies of solvation in formamide are converted into absolute enthalpies of solvation by considering the differences between the experimental enthalpies of solvation of cations and anions with identical radii. These differences are caused by the particular charge distribution in the solvent molecule and can be represented as a function of the quadrupole moments of the solvent molecule. The absolute enthalpies of solvation of alkali and halide ions are interpreted in terms of the interaction energy of an ion with six coordinated formamide molecules. In addition, the polarization energy of the solvent beyond the first coordination shell is taken into account.
Messung der magnetischen Susceptibilität von braunsteinhaltigen galvanischen Zellen während der Entladung
Authors: Zeilmaker H. , Drotschmann C.
Published: September 2010

Measurements of the magnetic susceptibility of Leclanché‐type galvanic cells during electric discharges with γ‐ and β‐MnO2 show a different reaction mechanism. Mn2+ is formed during the first part of the discharge of γ‐MnO2. This Mn2+ remains in the MnO2 lattice in solid state. After the catholyte has become alkaline and when a sufficiently great quantity of Mn2+ has been formed in the lattice, a second solid phase will appear. With β‐MnO2, forming of a second solid phase seems to start already after the beginn of the discharge.
Investigations on sterols XXX: Synthesis and stereochemistry of 9β,10α‐isomers of some adrenocortical hormones
Authors: Smit A. , Bakker J.
Published: September 2010

The structure of a microbiological hydroxylation product of 17α,21‐dihydroxy‐9β,10α‐pregn‐4‐ene‐3,20‐dione is found to be 11α,17α,21‐trihydroxy‐9β, 10α‐pregn‐4‐ene‐3,20‐dione. This product is converted into 9β,10α‐cortisone and to 9β,10α‐hydrocortisone. Reduction of the 11‐keto group with lithium aluminium hydride proceeds with the formation of 11β‐hydroxy in minor quantity only. The stereochemistry of the 11‐hydroxyl compounds is discussed on the basis of their nuclear magnetic resonance spectra.
Synthesis of vinyloxypentene and its pyrolysis to aldehyde
Authors: Harkes P. D.
Published: September 2010

The multi‐stage synthesis of vinyloxypentene from 1‐penten‐3‐ol, described by Hurd and Pollack, has been studied. In each reaction step a mixture of a straight‐chain and a branched isomer is formed, the content of the branched compound gradually decreasing. It is highly probable that in the end product no 3‐vinyloxy‐1‐pentene, but only 1‐vinyloxy‐2‐pentene is present, for on pyrolysis of the end product exclusively 3‐ethyl‐4‐pentenal is formed, and no 4‐heptenal as stated in the relevant literature.

The synthesis of the model compound 3‐ethyl‐4‐pentenal is described.
The effect of pH upon the solubilities of some inorganic hydroxides in water
Authors: McGowan J. C.
Published: September 2010

Ionization constants for the dissociations of protons from hydrated metal ions have been estimated and variations with pH of the solubilities of some inorganic oxides and hydroxides in aqueous solutions have been interpreted. It is suggested that the metal ions in solutions of most amphoteric hydroxides exist in two forms at least: there is present either the unhydrated ion and one or more hydrated ions or at least two hydrated ions with different numbers of coordinated groups. When a given ion forms two hydrates, the one with the higher co‐ordination number is the more basic.
Amination of the isomeric dibromopyridines with potassium amide in liquid ammonia
Authors: Streef J. W. , Den Hertog H. J.
Published: September 2010

In connection with an investigation being carried out in our laboratory on the influence of substituents on the course of reactions of halogenopyridines with potassium amide in liquid ammonia, the aminations of 2,3‐, 2,4‐, 2,5‐, 3,4‐ and 3,5‐dibromopyridine and of possible intermediate products, i.e., 4‐amino‐3‐bromopyridine, the 5‐ and 6‐bromo derivatives of 3‐aminopyridine and the 3‐, 4‐ and 5‐bromo derivatives of 2‐aminopyridine, have been studied. End‐products are diaminopyridines or mixtures of these compounds and in some reactions a small amount of 4‐amino‐2‐methylpyrimidine. The last‐mentioned substance is the sole product isolated from the reaction mixture, obtained in the amination of 2,6‐dibromopyridine3,4.

The course of the aminations can be explained from what is known on the mechanisms of the aminations of the isomeric monobromopyridines and the mode of addition of ammonia to the triple bond in 3‐ and 4‐substituted benzynes. For the formation of 4‐amino‐2‐methylpyrimidine from 2,3‐, 2,4‐ and 2,5‐dibromopyridine a mechanism is suggested which is analogous to that assumed for the formation of that substance from 2,6‐dibromopyridine3,4.
The reaction mechanism of the acid‐catalysed autoxidation of xanthene to xanthylium ion
Authors: ter Borg A. P. , Gersmann H. R. , Bickel A. F.
Published: September 2010

This paper describes an investigation into the kinetics of the autoxidation of xanthene to xanthylium ion and hydrogen peroxide in a perchloric acid/acetic acid mixture at 20°. Apart from acid catalysis, the reaction also shows the characteristics of a free‐radical chain autoxidation. In the mechanism devised to account for the results the key feature is hydrogen abstraction by a protonated peroxy radical with simultaneous production of the stable xanthylium ion:
\documentclass{article}\pagestyle{empty}\begin{document}\[{\rm RH + RO}_{\rm 2}{\rm H}\cdot^\oplus\to{\rm R}^\oplus+{\rm H}_{\rm 2}{\rm O}_{\rm 2}+{\rm R}\]\end{document}
Derivatives of benzo‐ and indolo‐quinolizines IV: Synthesis of some 1‐ or 3‐substituted hexahydro‐2H‐benzo[a]‐quinolizines and octahydroindolo[2,3‐a]quinolizines
Authors: Gootjes J. , Nauta W. Th.
Published: September 2010

The preparation of some derivatives of 1,3,4,6,7,1 1b‐hexahydro‐9,10‐dimethoxy‐2H‐benzo[a]quinolizine and 1,2,3,4,6,7,12,12b‐octahydroindolo‐[2,3‐a]quinolizine substituted with two alkyl groups, either in the 1‐ or the 3‐position is described. Two reaction routes were followed for each of the two types of compounds and some of the numerous intermediates have been isolated.
Conformation of non‐aromatic ring compounds XXIX: Conformation and pseudorotation intrans‐1,2‐dihalogenocyclopentanes
Authors: Altona C. , Buys H. R. , Havinga E.
Published: September 2010

The relative energies of the pseudorotation conformations oftrans‐1,2‐dihalogenocyclopentanes are evaluated excluding dipole‐dipole interactions. The most stable form corresponds to the half‐chair model with the halogen atoms diaxally disposed about the “puckered” carbon‐carbon bond.
Studies in transition metal chemistry. Part VI: Soluble Ziegler‐type catalysts based on vanadium. Part II
Authors: de Liefde Meijer H. J. , van den Hurk J. W. G. , van der Kerk G. J. M.
Published: September 2010

Spectrophotometric measurements in the visible region on soluble catalyst systems prepared from (i) vanadium tetrachloride, aluminium bromide and tetraphenyltin and (ii) vanadium tetrachloride or vanadium oxytrichloride and ethylaluminium dihalides are reported. The formation of hydrocarbon‐soluble inorganic vanadium/aluminium halide complexes containing the transition metal in the tetra‐, tri‐ and di‐valent oxidation state is described and their absorption spectra are recorded. By means of these spectra it is shown that all catalyst systems contain analogous vanadium species, viz. complexes of divalent vanadium in which the transition metal is surrounded octahedrally by halogen atoms only. Evidence is given for the view that organic groups are attached to the aluminium site of the complexes. The structure of the catalytically active species in these systems is discussed.
Acid‐Catalyzed hydrolysis of benzoylphenyldiazomethane: Short communication
Authors: Engberts J. B. F. N. , Bosch N. F. , Zwanenburg B.
Published: September 2010

Kinetic measurements show that in acidic media the hydrolysis of benzoyl‐phenyldiazomethane is generally acid‐catalyzed. A mechanism for this reaction is proposed. In neutral solutions a different mechanism operates.
Nuclear magnetic resonance studies in coordination chemistry. I: Structure and conformational rearrangements of π‐allyl complexes containing group‐V donor ligands
Authors: Vrieze K. , Maclean C. , Cossee P. , Hilbers C. W.
Published: September 2010

Nuclear magnetic resonance has been employed to investigate the structure of the complexes (π‐allyl) PdCl(L) (L = phosphine, Ph3As, Ph3Sb) and the conformational rearrangements of the allyl group in these compounds as affected by the ligand, the ligand‐to‐metal ration and the temperature (in CDCl3).

Several types of rearrangement were observed, depending on the choice of the variables mentioned above. At low temperatures a short‐lived σ‐allyl intermediate was found in the case of the phosphines only, whereas at higher temperatures rotation of the π‐allyl group was inferred for all the ligands. At very high temperatures and high ligand‐to‐metal ratios a σ‐allyl group had to be postulated to explain the NMR spectra, which are analogous to those of σ‐allyl‐magnesium halide compounds.

A molecular orbital description has been used to rationalize some of the experimental results.
On the mechanism of cis‐ligand insertion
Authors: Cossee P.
Published: September 2010

For reactions of the type magnified image L‐O, generally called “cis‐ligand insertion”, there is increasing experimental evidence that the group<//UEQN> Q migrates. The present paper gives a theoretical analysis of this rearrangement, which is illustrated by the specific example of the growth reaction in Ziegler polymerizations of a‐olefins:magnified image

As a first approximation to the reaction path the angular vibrabtion of R is analysed from a quantum‐mechanical point of view, showing the role that d orbitals in transition‐metal compounds play in the migration of alkyl groups to π‐bonded olefins.

It appears that the migrating ligands finds a suitable combination of orbitals to remain bonded to the complex all along the reaction coordinate.
Investigations on organogermanium compounds. IV Transalkylation reactions between germanium compounds
Authors: Rijkens F. , Bulten E. J. , Drenth W. , van der Kerk G. J. M.
Published: September 2010

Transalkylation reactions between germanium derivatives, including substituted digermanes, have been investigated. These reactions, which usually need a catalyst, e.g. a germanium dihalide, are tentatively explained by an electrophilic attack on the carbon atom of a germanium‐carbon bond of the alkyl‐donor. Many reactions reported in the literature which involve alkyl‐transfer among derivatives of the IVB group elements can be interpreted in the same way.
Preparation of some new derivatives ofmeta‐di‐tert‐butylbenzene
Authors: Knoester C. J. , de Koning A. J. , Verkade P. E. , Wepster B. M.
Published: September 2010

Some new derivatives ofmeta‐di‐tert‐butylbenzene are described. The rates of deacetylation of a number of such derivatives are briefly discussed.
Preparation of some 4‐ or 5‐substituted 2‐tert.butylbenzoic acids
Authors: Baas J. M. A. , Wepster B. M.
Published: September 2010

The preparation of fifteen derivatives of 2‐tert.butylbenzoic acid, substituted in the aromatic nucleus in the 4‐ or the 5‐position, and of a 4,5‐disubstituted 2‐tert.butylbenzoic acid is described.
Synthesis and investigation of γ‐substituted α‐ethoxycarbonyl‐γ‐lactones
Authors: Maat L. , Sinnema A. , Beyerman H. C.
Published: September 2010

Ten γ‐substituted α‐ethoxycarbonyl‐γ‐butyrolactones (1–10) have been prepared from diethyl malonate and 1‐chloroalkan‐2‐ols. The scope and the course of the reaction are discussed. The products have been investigated by infrared and proton magnetic resonance methods. The lactones have been characterized by their anilides and some other derivatives.
Chemistry of propadiene. II. The addition of dichlorocarbene to propadiene
Authors: Peer H. G. , Schors A.
Published: September 2010

The addition of dichlorocarbene to propadiene has been investigated. The reaction between propadiene and dichlorocarbene obtained from chloroform and potassium t‐butoxide leads to tarry products. When generated by thermal decomposition of sodium trichloroacetate, the dichlorocarbene reacts with propadiene, yielding 1,1‐dichloro‐2‐methylenecyclopropane (II). The structure of this compound was established by means of infrared and NMR spectroscopy and confirmed by chemical means.
Electron diffraction by gases: The molecular structure of bicyclo[2,1,1]hexane
Authors: Dallinga G. , Toneman L. H.
Published: September 2010

The structure of bicyclo [2,1,1] hexane has been investigated by means of electron diffraction of the vapour. In the discussion of the results presented here, emphasis is on the ambiguities connected with the analysis of molecules containing many nearly equal interatomic distances.
Hetarynes XIV: Action of potassium amide on 2‐, 3‐ and 4‐bromoquinolines in liquid ammonia
Authors: den Hertog H. J. , Buurman D. J.
Published: September 2010

Both 3‐ and 4‐bromoquinoline when reacted with potassium amide in liquid ammonia, are converted into a mixture of 3‐ and 4‐aminoquinoline probably via 3,4‐quinolyne as an intermediate.

2‐Bromoquinoline yields together with 2‐aminoquinoline, 2‐methylquinazoline as the result of a ring transformation.

The mechanisms of the reactions are discussed.
Chemistry of α‐diazosulfones. Part IX. Synthesis of sulfonylcyclopropanes by addition of a sulfonylcarbene to alkenes
Authors: van Leusen A. M. , Mulder R. J. , Strating J.
Published: September 2010

Sulfonyl substituted cyclopropanes are formed in good yields on photolysis of p‐methoxyphenylsulfonyldiazomethane in the presence of alkenes. The reaction with cis‐ and trans‐2‐butene is stereospecifically cis, which may indicate that the intermediate sulfonylcarbene reacts in its singlet spin state.
The copper‐catalysed oxidation of unsaturated carbonyl compounds: Part VI: Synthesis of α,β‐unsaturated γ‐lactams by oxidative coupling of unsaturated ketones and ammonia
Authors: Volger H. C. , Brackman W.
Published: September 2010

Oxidative coupling by oxygen of ammonia and α,β‐or β,γ‐unsaturated ketones containing a primary γ‐carbon atom in a homogeneous solution of a copper ammonia methoxide catalyst in methanol leads to the formation of α,β‐unsaturated γ‐lactams in moderate yield.
Enthalpies of solvation of alkali metal and halide ions in N‐methylformamide and N‐methylacetamide at 25°
Authors: Weeda L. , Somsen G.
Published: September 2010

Measurements of the enthalpies of solution of LiI, NaI, KF, KCl, KBr, KI, RbI and CsI in N‐methylacetamide at 35° with an adiabatic calorimeter are reported.

A calculation of the ionic enthalpies of solvation of the alkali metal and halide ions in N‐methylformamide and N‐methylacetamide is given. From the difference in ionic enthalpy of solvation of the fluoride and the potassium ions in water, formamide, N‐methylformamide and N‐methylacetamide, respectively, the quadrupole moments of these solvent molecules have been calculated.
The conformation of non‐aromatic ring compounds. Part 35: Trimethylene Sulfite and Related Compounds
Authors: van Woerden H. F. , Havinga E.
Published: September 2010

A series of 2‐substituted trimethylene sulfites have been synthesized; in most cases two stereoisomers were isolated. The geometric and conformational characteristics were studied by the determination of dipole moments in carbon tetrachloride and in benzene, as well as by taking infrared spectra in various solvents and in the solid state (KBr discs). It is concluded that the SO bond has a preference for the axial position, its A‐value amounts to −3.5 ± 1 kcal/mole. The stretching frequency of the SO bond is 1190‐1205 cm−1 in the axial position and 1230‐1250 cm−1 in the equatorial position. The dipole moments can be quantitatively interpreted in a consistent way by assuming the partial moment of the sulfite group to be 2.5 D (CH  0 D), and its direction significantly deviating from the SO bond direction (Fig. 2).
Efficiency of chromatographic procedures. Part IV: The efficiency of paper chromatography on various kinds of Whatman paper and of thin‐layer chromatography on various kinds of cellulose powder for the separation of amino‐acids
Authors: de Ligny C. L. , Remijnse A. G.
Published: September 2010

An improved equation for the efficiency of strip chromatography (i.e., paper and thin‐layer chromatography) is derived.

This equation is used to investigate the efficiency of ten kinds of Whatman chromatography paper and of six kinds of cellulose powder for the separation of amino‐acids by means of a 4: 1: 5 butanol ‐ acetic acid ‐ water mixture.
The synthesis of lactones. Part I: Saturated δ‐ and ϵ‐Lactones
Authors: Lardelli G. , Lamberti V. , Weller W. T. , de Jonge A. P.
Published: September 2010

A homologous series of δ‐ and ϵ‐lactones has been synthesized, as well as some branched‐chain δ‐lactones.

The δ‐lactones have been prepared by oxidation of 2‐alkylcyclopentanones or 2,5‐dialkylcyclopentanones with Caro's acid or by hydrogenation of corresponding oxo acids. The latter were obtained by chromic acid oxidation of these 2‐alkylcyclopentanones, or by Cason synthesis from 4‐methoxycarbonyl‐butanoyl chloride and dialkylcadmium, or by condensation of vinyl ketones with diethyl malonate.

The alkylcyclopentanones were prepared by catalytic hydrogenation of 2‐alkylidenecyclopentanones obtained by aldol condensation of cyclopentanone and alkanals. The 2,5‐dialkylcyclopentanones, used as starting compounds for branched‐chain δ‐lactones, were obtained either by aldol condensation or by Dieckmann synthesis.

A general method for the preparation of ϵ‐lactones (lactonisation of 6‐hydroxy acids under the influence of aromatic sulfonic acid) has been developed.

Some physical constants of the pure compounds (including the intermediates) and of some of their characteristic derivatives have been determined.
Salcomine‐catalyzed oxidations of some phenols: A new method for the preparation of a number ofpara‐benzoquinones
Authors: van Dort H. M. , Geursen H. J.
Published: September 2010

Bis(salicylidene)ethylenediiminocobalt(II) (salcomine)* is a homogeneous catalyst for the oxidation of phenols with molecular oxygen in solutions of chloroform or methanol at room temperature. A number of substituted phenols with a freepara‐position have been studied; in most cases the correspondingpara‐benzoquinone was the main reaction product. Compounds originating from coupling of aryloxy radicals were also detected or isolated. Some speculations on the mechanism of the reaction have been made.
The preparation of Ca, Sr, Cd and Mn antimonites
Authors: Wanmaker W. L. , Hoekstra A. H. , Verriet J. G.
Published: September 2010

By heating CaO, SrO, CdO or MnCO3, in a non‐oxidizing atmosphere, with Sb2O3 it was possible to prepare some new antimonites, viz.: CaSb2O4, Ca2Sb2O5, Ca3Sb2O6, SrSb2O4, Sr2Sb2O5, CdSb2O4, Cd3Sb2O6 and Mn3Sb2O6. The X‐ray powder diagrams of the compounds synthesized and the reflection spectra of some of the antimonites are given. The thermal stability was determined by heating in an atmosphere of nitrogen on a thermobalance.
Dielectric study of complex formation: Application to organozinc chemistry
Authors: Gevers E. Ch. Th.
Published: September 2010

The method of dielectric constant titration was applied to the study of complexes of dialkylzinc compounds with 2,2′‐bipyridine and with N,N,N′,N′‐tetramethylethylenediamine.
Cyclic sulfites of glycerol and its chlorohydrins
Authors: van Woerden H. F. , van Valkenburg Clara F. , van Woerkom G. M.
Published: September 2010

The synthesis is described of some cyclic sulfites derived from glycerol, glycerol α‐ and β‐monochlorohydrin and 2,2‐dichloropropane‐1,3‐diol.
Chemistry and spectroscopy in strongly acidic solutions. Part III: Formation of two different entities on protonation of formic acid
Authors: Hogeveen H. , Bickel A. F. , Hilbers C. W. , Mackor E. L. , Maclean C.
Published: September 2010

It has been shown by NMR spectroscopy that protonation of formic acid in HF‐BF3 solution leads to an equilibrium mixture of two different proton adducts, which probably differ in the configuration around the partly double carbon‐oxygen bond. Diffusion‐controlled proton transfer reactions take place between the stable protonated species (which are not directly interconvertible under the experimental conditions) and fluoride anions. No evidence has been found of the occurrence of protonated CO.
Decomposition of dimeric α‐nitrosocarboxylic acids in sulfuric acid
Authors: Duynstee E. F. J. , Mevis M. E. A. H.
Published: September 2010

When dimeric α‐nitrosocyclohexanecarboxylic acid (I) is dissolved in cold concentrated sulfuric acid, rapid decomposition occurs and two products can be isolated. The first is a product to which we tentatively assign structure II (cyclohexanespiro‐4′‐(4′,5′‐dihydro‐1′,2′,3′‐oxadiazol‐5′‐one‐3′‐oxide)). The second product is cyclohexene‐1‐carboxylic acid. Dimeric α‐nitrosoisobutyric acid does not give an analogous decomposition.
Some electrophilic substitution reactions of 9,10‐dimethyltriptycene
Authors: de Koe P. , de Rijke C.
Published: September 2010

Friedel‐Crafts acylation, bromination and nitration of 9,10‐dimethyltriptycene are described.
Mass spectra of the tetramethyl and tetraethyl compounds of carbon, silicon, germanium, tin and lead
Authors: de Ridder J. J. , Dijkstra G.
Published: September 2010

This paper reports the monoisotopic mass spectra of the tetramethyl and tetraethyl compounds of carbon, silicon, germanium, tin and lead.

Metastable ion transitions and appearance potentials are given. The primary ionization results in an electron deficiency on the metal atoms, which attain electron configurations similar to those of the third‐group elements. The stabilities of the valence states of these elements explain the cracking patterns.
Absolute configuration of (‐)‐β‐hydroxy‐β‐(m‐hydroxyphenyl)‐propionic acid
Authors: Deljac A. , Balenović K. , Urbas B.
Published: September 2010

(‐)‐β‐Hydroxy‐β‐(m‐hydroxyphenyl)propionic acid has been correlated with D‐mandelic acid through reaction stages (I‐VII). The resulting absolute configuration is represented by the projection formula VI. As consequence of this correlation (‐)‐m‐hydroxymandelic acid (VII) must also belong to the D‐series of α‐hydroxy‐acids.
pH‐measurements in alcohol‐water mixtures. On the use of aqueous standard buffer solutions for calibration
Authors: Gelsema W. J. , de Ligny C. L. , Blijleven H. A.
Published: September 2010

To investigate the variation with alcohol‐percentage of the standard potential of glass electrodes of a wide range of types and manufactures, e.m.f.‐measurements have been made on cells of the type: glass electrode/standard buffer solution/saturated KCl‐solution (aq.)/Hg2Cl2‐Hg, using standard succinate buffer solutions in methanol‐water and ethanol‐water mixtures.

An analysis is given of the accuracy of pH‐determinations in alcohol‐water mixtures, using both standard buffer solutions in the same solvent and aqueous standard buffer solutions for calibration.
Aromatic sulfonation. Part XVII: Kinetics and mechanism of the sulfonation of chlorobenzene in aqueous sulfuric acid
Authors: Kort C. W. F. , Cerfontain H.
Published: September 2010

Chlorobenzene has been sulfonated homogeneously in aqueous sulfuric acid varying from 83.4 to 99.6 wt‐%, at 25°. The isomer distribution‐98.8% para, 0.8% ortho, 0.4% meta ‐ is constant over the acid range studied. The substrate isotope effect has been determined under conditions of rapid hydrogen exchange; kD/kH varies from 0.8 in 95% sulfuric acid to 0.4 in 97%. The dependence of the reaction rate and the isotope effect on the acid concentration is explained by an SE2‐mechanism involving attack by H2S2O7 followed by proton removal from the σ‐complex by HSO4−; the latter process is partly rate‐limiting at high acid concentrations.
Proton magnetic resonance spectra of protonated dialkyl ketones: (Dialkylhydroxycarbonium ions)
Authors: Brouwer D. M.
Published: September 2010

Proton magnetic resonance spectra of eight protonated dialkylketones (dialkylhydroxycarbonium ions) have been measured in HF ‐ SbF5. Due to restricted rotation about the partially double C ‐ O bond, which leads to synanti isomerism, symmetric ketones (R1 = R2) give cations with non‐equivalent alkyl groups. Unsymmetric ketones (R1 ≠ R2) give two isomeric cations which are spectroscopically distinguishable below 0°C. The free energy barrier to rotation is at least 17 kcal/mole. Assignments of the observed PMR signals to the one or the other isomer of dialkylhydroxycarbonium ions are given. The preference of the hydroxyl proton for being syn to an alkyl group increases in the order tert‐butyl < neopentyl, ethyl, isopropyl < methyl. For methyl tert‐butyl ketone, the isomer ratio is about 15. The preferred conformations about the OC ‐ Cα bond of the alkyl groups are discussed on the basis of observed chemical shifts and stabilities.
Cyclopentadienyl(triphenylphosphine)nickel(II) halides
Authors: van den Akker M. , Jellinek F.
Published: September 2010

The cyclopentadienyl(triphenylphosphine)nickel(II) halides C5H5NiPPh3X with X = Cl, Br, I, have been synthesized in good yields from nickelocene and triphenylphosphonium halides. Some chemical, physical and crystallographic properties of the complexes are given and their electronic, infrared and particularly their proton‐magnetic‐resonance spectra are discussed. The iodide forms an inclusion compound with hexane of composition C5H5NiPPh3I · 1/2C6H14.
Conformation of non‐aromatic ring compounds. Part 41. Dipole moments and NMR spectra of 1,1,2‐trihalogeno‐cyclo‐hexanes and ‐cyclopentanes
Authors: Buys H. R. , Altona C. , Havinga E.
Published: September 2010

The dipole moments and NMR spectra of 1,1,2‐trihalogeno‐cyclohexanes and ‐cyclopentanes in several solvents are reported. The low‐field part of the NMR spectra, due to the proton in the CHX‐moiety, yields J = JAX + JBX. Equilibrium studies are carried out with the aid of the J‐values of the equilibrating and the conformationally homogeneous compounds. The equatorial conformer is found to be the predominant one. Long‐range coupling constants (4J) are determined for a number of these compounds.
Covalency effects in the spectrum of the tetrachloroferrate(III) anion
Authors: Balt S.
Published: September 2010

The ligand field approach to the interpretation of the visible spectrum of the tetrachloroferrate(III) anion has been critically reviewed. The influence of differences in the delocalisation of the metal t2 and e orbitals has been considered. This covalency influence could be worked out either by using different nephelauxetic parameters or by introducing different crystal field parameters. Both approaches were found to give a satisfactory explanation of the relative positions and the number of bands in the spectrum, although the agreement between calculated and observed energies is not very good.
Complexes with ligands containing nitrile groups Part I. Methyl cyanide complexes of mono‐ and di‐valent metal chlorides with antimony pentachloride
Authors: Zuur A. P. , Groeneveld W. L.
Published: September 2010

This paper describes systems of mono‐ and di‐valent metal chlorides with antimony pentachloride in methyl cyanide. The Cl−‐ion transfer, which occurs between the chlorides and antimony pentachloride in solution, has been studied conductometrically. This transfer is discussed on the basis of electrostatic theory.

In the solid state, complexes of the types M+1(CH3CN)xSbCl6− and M2+(CH3CN)y(SbCl6−)2 are isolated. The mono‐ and di‐valent metal ions are solvated by the methyl cyanide molecules. Magnetochemical measurements indicate that the divalent transition metal ions are surrounded octahedrally by six methyl cyanide molecules.
The chemistry, herbicidal and fungicidal activities of 2,1,3‐benzothiadiazoles
Authors: van Daalen J. J. , Daams J. , Koopman H. , Tempel A.
Published: September 2010

The synthesis and test results on the herbicidal and fungicidal activities of a large number of 2,1,3‐benzothiadiazoles, mainly 4,5,7‐trisubstituted derivatives, are described and discussed.
Kinetics of the desulfonation of benzenesulfonic acid and the toluenesulfonic acids in aqueous sulfuric acid
Authors: Wanders A. C. M. , Cerfontain H.
Published: September 2010

The kinetics of the desulfonation of benzenesulfonic and the isomeric toluenesulfonic acids have been studied at 120‐155° in 65‐85 wt‐% sulfuric acid with the aid of an inert gas (nitrogen) stripping technique. All reactions were found to be of the first order with respect to the initial sulfonic acid. At high temperatures and/or high sulfuric acid concentrations substantial isomerisation of the toluenesulfonic acids took place, especially at low nitrogen flow rates.

The rate‐constants of the desulfonation step proper ‐ i.e. the rate‐constants corrected for resulfonation ‐ increase with increasing acid concentration and temperature. The dependence of the rate of desulfonation on acidity is compatible with the sulfonation mechanism recently proposed by Kort and Cerfontain40, if the sulfonate anion is supposed to be the active substrate species in the desulfonation reaction.

Partial rate‐factors for protodesulfonation of the toluenesulfonic acids and the tert‐butylbenzenesulfonic acids have been calculated. For a given alkyl substituent fo > fp >> fm. The protodesulfonation obeys the Selectivity Relationship. It is, therefore, suggested that the protodesulfonation of arenesulfonic acids in aqueous sulfuric acid proceeds via a Wheland‐type intermediate.
Mass spectra of some tetra‐alkylgermanium compounds
Authors: de Ridder J. J. , van Koten G. , Dijkstra G.
Published: September 2010

This paper reports the monoisotopic mass spectra of the compounds Ge(Alkyl)4, in which Alkyl = methyl, ethyl, propyl, butyl, pentyl and hexyl. With the aid of metastable ion transitions the fragmentation patterns could be given. With the exception of GeMe4 these are all similar and can be explained by a few rules, the first being the tervalence of the Ge after primary ionization. In GeMe4 splitting off of alkene fragments is difficult. As the alkyl chain length increases hydrocarbon ion abundance increases considerably.
Studies on cyclohexane derivatives. Part VI: cis‐ and trans‐1,4‐Di‐t‐butylcyclohexane. Preparation and properties
Authors: van Bekkum H. , Hoefnagel M. A. , de Lavieter L. , van Veen A. , Verkade P. E. , Wemmers A. , Wepster B. M. , Palm J. H. , Schäfer L. , Dekker H. , Mosselman C. , Somsen G.
Published: September 2010

cis‐ and trans‐1,4‐Di‐t‐butylcyclohexane have been prepared. Evidence is presented showing that the cis‐isomer is mainly in a non‐chair conformation.

The enthalpy difference between the two isomers in the liquid state at 25° is 4.7 kcal/mole, the trans‐isomer having the lower strain.
NMR substituent constants in benzene derivatives: Short communication
Authors: van Meurs N.
Published: September 2010

The ortho, meta and para substituent constants of 18 benzene substituents have been determined for dilute solutions in carbon tetrachloride. They enable the ring‐proton chemical shifts of di‐ and tri‐substituted benzenes with isolated groups to be calculated within 0.05 ppm from the experimental values. In the case of 2 adjacent substituents the meta and para substituent constants generally remain unchanged, whereas the ortho constants are often dependent upon the neighbouring substituents.
Polynuclear heterocyclic systems. Part V: Heterocycles related to steroids and C‐nor‐steroids
Authors: van Hes R. , Skolnik S. , Pandit U. K. , Huisman H. O.
Published: September 2010

The preparation of 6‐methoxy‐2‐(2′‐oxocyclopentyl‐1‐tetralone (I) and 2‐(2′‐oxocyclopentyl)quinolizidin‐1‐one (II) is described. Diketones I and II have been converted to heterocyclic systems related to steroids and C‐nor‐steroids.
Synthesis of 2‐deoxyinosadiamines‐1,3 including 2‐deoxystreptamine
Authors: Dijkstra D.
Published: September 2010

Hydrogenation of 4,6‐dinitropyrogallol over a rhodium‐platinum catalyst yielded 2‐deoxy‐cis‐inosadiamine‐1, 3 as the main product. This was converted into 2‐deoxy‐epi‐inosadiamine‐1, 3 by catalytic oxidation followed by trans‐directing reduction. From the epi‐isomer, 2‐deoxystreptamine was prepared by a similar oxidation/reduction procedure.
The 5,6‐dihydrothiazolo[2,3‐b]thiazolium system
Authors: Bradsher C. K. , Jones W. J.
Published: September 2010

The cyclization of hydrohalide salts of 2‐(2‐thiazolinthio) methyl ketones to yield the first simple 5,6‐dihydrothiazolo[2,3‐b]thiazolium salts has been carried out. It is believed that the transformation which 3‐methyl‐5,6‐dihydrothiazolo‐[2,3‐b]thiazolium perchlorate undergoes in alkaline solution and in the presence of air involves ring opening and oxidation of the resulting mercaptan to a disulfide.
Organophosphorus compounds VII: The absolute configuration of sarin and related anticholinesterases established by chemical correlation
Authors: Benschop H. P. , van den Berg G. R. , Boter H. L.
Published: September 2010

The reaction of (+)‐(i‐PrO)MeP(O)SMe with phenylmagnesium bromide in tetrahydrofuran affords (+)‐(i‐PrO)MeP(O)Ph, representing the first example of a stereospecific synthesis of a phosphinate ester from a phosphonothiolate ester. Levorotatory (MeS)MeP(O)Ph is converted into (R)‐(+)‐n‐PrMeP(O)Ph with inversion of configuration by reaction with n‐propylmagnesium bromide. The two Grignard reactions are correlated by the conversion of (‐)‐(MeS)MeP(O)Ph into (+)‐(i‐PrO)MeP(O)Ph with potassium isopropoxide.

The correlation of the configuration of (R)‐(+)‐n‐PrMeP(O)Ph with that of (+)‐(i‐PrO)MeP(O)SMe by means of the fore‐mentioned reactions determines the absolute configuration of (+)‐(i‐PrO)MeP(O)SH to be (s). Since the latter compound is a common precursor for the synthesis of several types of optically active anticholinesterases, the absolute configurations of these could also be deduced, e.g. (R)‐(‐)‐isopropyl methylphosphonofluoridate (sarin).
The reaction between tri‐n‐octylamine and sulfuric acid
Authors: Foppema R.
Published: September 2010

A kinetical study is reported on the reaction between aqueous sulfuric acid and 0.4 to 1.0 M solutions of tri‐n‐octylamine (TOA) in chloroform. The results are interpreted in terms of a reaction mechanism in which two types of the intermediate TOAH+ ion are distinguished. The proposed mechanism accounts for form and magnitude of the observed equilibrium constant

A hypothetical explanation is offered for the distinction between the two intermediates. The hypothesis predicts that below a critical sulfate ion activity interconversion of the intermediates becomes predominant, leading to a more simple mechanism and a more conventional form of the equilibrium constant. Such a transition could be responsible for earlier observations, where a different type of equilibrium constant with a limited validity area was found for the analogous reaction with benzene solutions of the amine.
Photodehydrocyclizations in stilbene‐like compounds
Authors: Laarhoven W. H. , Cuppen Th. J. H. M. , Nivard R. J. F.
Published: September 2010

Photodehydrocyclizations, analogous to the formation of phenanthrene from stilbene, appear to be possible only if the sum of the free valence numbers of the proper atoms in the first excited state exceeds a critical value. Localization energies and superdelocalizabilities also set bounds to the occurrence of this type of reaction. Calculation of the relative magnitudes by the simple Hückel MO method appears to be satisfactory only in alternating compounds.
Factors governing cyclopropane versus pyrazoline formation in the reaction of diazomethane with s‐trinitrobenzene: Nucleophilic aromatic addition VIII
Authors: Louwrier‐De Wal J. , de Boer Th. J.
Published: September 2010

sym‐Trinitrobenzene reacts successively with three molecules of diazomethane yielding “trismethylene‐trinitrobenzene” (VIII). In each stage an intermediate diazonium betaine (II, V and VII) is postulated with considerable negative charge delocalisation. Such betaines lose nitrogen to give cyclopropanes rather than retaining nitrogen with ring closure to give pyrazolines. Pyrazoline formation becomes important when charge delocalisation is restricted, as in the reaction of the non‐conjugated double bond in VIII with a (fourth) molecule of diazomethane yielding the stable pyrazoline IX either via a betaine or by 1,3‐dipolar addition.
HF‐SbF5 catalysed isomerization of 2‐methylpentane: Kinetics and mechanism of rearrangement and hydride‐ion transfer steps in alkylcarbonium ion reactions
Authors: Brouwer D. M. , Oelderik J. M.
Published: September 2010

A kinetic investigation has been made of the isomerization of 2‐methylpentane with liquid HF‐SbF5 as catalyst at temperatures of from −20 to +20 °C. The isomerization proceeds in three distinct stages: first 3‐methylpentane is formed, then the equilibrium mixture of 2‐ and 3‐methylpentane isomerizes to equilibrium with 2,3‐dimethylbutane, and finally that mixture reacts to give n‐hexane and neohexane, respectively, until thermodynamic equilibrium is reached. Rate constants at 0 ° for these four reactions are 0.42, 0.030, 0.00015, and 0.0007 s−1 · (mole hexane) · (mole SbF5)−1, respectively. In the first reaction, mass transfer between acid and hydrocarbon phases is rate limiting; the rate‐determining step of the second reaction is the intramolecular rearrangement of the intermediate tertiary carbonium ions, and of the last two reactions the intermolecular hydride‐ion transfer between secondary and tertiary carbons. The rate constant for hydrideion transfer from a secondary carbon to a tertiary carbonium ion is about 0.06 1 · mole−1 · s−1 at 0 ° (EA = 14−15 kcal · mole−1), and for that between two tertiary carbons is greater than 10 1 · mole−1 · s−1. The rate of rearrangement of a tertiary ion to a secondary or tertiary ion with different degree of chain branching is about 0.1 s−1 at 0 ° (EA = 16−17 kcal · mole−1). A mechanism for that type of rearrangement via a (protonated) cyclopropane ring is consistent with the data. In particular, it explains why n‐butane does not isomerize to isobutane under conditions where n‐pentane and n‐hexane are rapidly converted.
Complexes with ligands containing nitrile groups: Part IV. Systems of di‐ and tri‐valent metal chlorides with antimony pentachloride in methyl cyanide
Authors: Zuur A. P. , van Houte J. J. , Groeneveld W. L.
Published: September 2010

Conductometric as well as potentiometric tritrations are reported to study the Cl−ion transfer in systems consisting of di‐ and tri‐valent metal chlorides with antimony pentachloride in methyl cyanide.

On the basis of the potentiometric titrations a theoretical discussion is given of this Cl− ion transfer.

During the potentiometric measurements it was ascertained that chlorinated molybdenum metal can be used as a reversible secondary chlorine electrode.

In the solid state several complexes of the types:

M3+(CH3CN)x · (SbCl6−)3 in which M = Al3+, Ga3+, In3+, Cr3+, V3+ and La3+, MCl2+(CH3CN)y · (SbCl6−)2 in which M = Fe3+ and MCl2+1(CH3CN)z · (SbCl6−) in which M = B3+, Tl3+ and Bi3+ are reported.

The formation of these complexes is studied using ternary phase diagrams.
The synthesis of some bis(1‐substituted cyclohexyl) nitroxides
Authors: Duynstee E. F. J. , Mevis M. E. A. H. , Ostendorf H. K. , de Kock R. J.
Published: September 2010

The nitrile and several esters of 1‐nitrosocyclohexanecarboxylic acid all gave the expected nitroxides upon thermal decomposition in toluene. These bis(1‐substituted cyclohexyl) nitroxides could not be isolated from the decomposition product and were therefore prepared in the pure form by another route, involving peracid‐oxidation of the corresponding bis(1‐substituted cyclohexyl) amines. The nitroxides were stable in the solid state, but in solution a slow decomposition occurred. Hydrogenation of the nitroxides yielded the corresponding hydroxylamines. The ESR parameters of the nitroxides are given.
Properties of diazosulfonates. Part VI: Quantum yields for the photolysis of 2‐methoxybenzenediazonium and for the photo‐isomerization of 2‐methoxybenzene‐trans‐diazosulfonate
Authors: Jonker H. , Thijssens Th. P. G. W. , van Beek L. K. H.
Published: September 2010

Quantum yields at pH = 1 and 4 were determined at 254, 313, 366 and 436 nm with the potassium ferrioxalate actinometer. The photoreactions were interpreted considering the reactions trans diazonium + sulfite, followed by photolysis of diazonium ions. The quantum yields for the photolysis of diazonium ions at 20° are 0.56 (254 nm), 0.39 (313 nm) and those for the photo‐isomerization of trans‐diazosulfonate are 0.29 (254 nm), 0.32 (313 nm), 0.37 (366 nm) and 0.42 (436 nm).

The trans‐cis isomerization constant Kf = ke/kt = 2.7 × 10−5 and the dissociation constant of the cis isomer Ke = k1/k2 = 1.8 × 10−5 mole/1 were derived from irradiation experiments at 436 nm and at pH = 7. The rate constants at 20° corrected to zero ionic strength are ke = 3.5 × 10−7S−1, kt = k1 = 0.013 s−1, and k2 = 700 1/mole. s.
Complexes of ligands containing S=O. Part VI. Metal‐ligand vibrations in complexes of tetramethylene sulfoxide
Authors: Reedijk J. , van Leeuwen P. W. N. M. , Groeneveld W. L.
Published: September 2010

Infrared spectra in the region 600‐200 cm−1 have been recorded for a number of complexes having the general formula M(C4H8SO)m(ClO4)n, in which M = Mg(II), Al(III), Ca(II), Cr(III), Mn(II), Fe(III), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), and Cd(II); m = 4 or 6; n = 2 or 3.

The band assigned to the vibration being mainly metal‐oxygen occurs in the region 370‐500 cm−1 for all the complexes studied. The frequency order for the divalent transition‐metal ions is found to be: Mn < Zn < Fe < Co < Ni < Cu, in agreement with other sequences and with the general stability order of Irving and Williams.
Some conversions of allenyl ethers
Authors: Hoff S. , Brandsma L. , Arens J. F.
Published: September 2010

Metallation of methoxypropadiene, CH2 = C = CHOCH3, with butyllithium in ether, followed by reaction with carbonyl compounds, R1R2C = O (R1 and R2 = H or alkyl or R1R2C = cyclohexyl), affords carbinols, CH2 = C = C[CR1R2 (OH)]OCH3, in excellent yields. Acid‐catalysed hydrolysis of these carbinols gives nearly quantitative yields of unsaturated ketols, magnified image 1‐Methoxy‐1‐methylthiopropadiene, CH2 = C = C(OCH3) (SCH3) (VI), has been obtained in 75% yield by adding CH3SSCH3 to the lithiated allenyl ether. Acid‐catalysed addition of alcohols, ROH (R = CH3 or C2H5), to methoxypropadiene affords acrolein acetals, CH2 = CHCH(OCH3) (OR) (VII), in good yields.

Diels‐Alder addition of ethoxypropadiene to a,β‐unsaturated aldehydes, R3CH = CH ‐ CH = O (R3 = H or CH3), leads to derivatives of 2,3‐dihydropyran (VIII).

The yields are moderate.

magnified image
The kinetics and thermochemistry of the thermal rearrangement of hexamethylbicyclo[2.2.0]hexa‐2,5‐diene (hexamethyldewarbenzene) and of hexamethyltetracyclo[2.2.0,02,6.03,5]hexane (hexamethylprismane)
Authors: Oth Jean F. M.
Published: September 2010

Hexamethylbicyclo[2.2.0]hexa‐2,5‐diene (hexamethyldewarbenzene) (II) rearranges thermally into hexamethylbenzene (III) above 80°. The kinetic parameters and the heat of this reaction were measured. From the heat of the reaction, from the heat of combustion of III and using thermochemical data, the strain energy of II could be deduced as:

Hexamethyltetracyclo[2.2.0.02,6.03,5]hexane (hexamethylprismane) (I) rearranges thermally into hexamethylbenzene (III). Kinetic experiments have shown that the rearrangement I → III proceeds along two parallel paths: ‐ in one path the rearrangement goes via hexamethyldewarbenzene (II) which accumulates appreciable in the course of the reaction; ‐ in one other path, the rearrangement goes most likely via hexamethyl‐tricyclo[2.1.1.05,6]hex‐2‐ene (hexamethylbenzvalene) (IV).

The kinetic parameters of the different steps and the overall heat of isomerization I → III were measured. From the heat of isomerization I → III, the strain energy of hexamethylprismane (I) could be deduced as:
Solid‐Phase synthesis of carboxyl‐terminal N‐substituted derivatives of oxytocin
Authors: Beyerman H. C. , van den Brink‐Zimmermannová H. Maassen
Published: September 2010

Previously we described the synthesis of N‐benzyloxycarbonyl‐S,S′‐dibenzyloxytocinoic acid on copolystyrene‐divinylbenzene according to the solid‐phase method of Merrifield, but using the triazolide coupling developed in this Laboratory. The nonapeptide‐polymer bond could be cleaved quite satisfactorily with methanolic ammonia to yield the linear peptide corresponding to oxytocin. Cyclization to the hormone oxytocin was known.

We now describe the facile cleavage of the nonapeptide‐polymer bond with methylamine, with hydroxylamine, and with hydrazine, which yielded the linear peptides corresponding to N‐benzyloxycarbonyl‐S,S′‐dibenzyloxytocinoic acid N′‐methylamide, N′‐hydroxyamide, and hydrazide, respectively.

Cyclization of the first derivative, presumably to oxytocinoic acid N′‐methylamide, gave material without appreciable avian depressor (fowl) activity.
Chemistry and spectroscopy in strongly acidic solutions. Part XIX: Behaviour of α,α‐dimethyl‐β‐propiolactone and hydroxypivalic acid in hydrogen fluoride‐boron trifluoride solution
Authors: Hogeveen H.
Published: September 2010

When α,α‐dimethyl‐β‐propiolactone is dissolved in HF‐BF3 solution at −80° C, an acyl‐oxygen cleavage of the ring occurs which results in the formation of protonated hydroxymethyldimethylacetyl cation (I). The hydrated form of this dication, dication (II), is obtained by protonation of hydroxypivalic acid under the same conditions.

Heating of a solution of (I) in HF‐BF3 to about −40° modifies the NMR spectrum reversibly owing to a rapid deprotonation. At about 0° an irreversible reaction takes place with the formation of oligomers (IV). At room temperature (IV) is irreversibly transformed into unsaturated oligomers (VI). Additional information on the products has been obtained from NMR, IR and mass spectrometric data of the compounds formed on quenching the acidic solutions with water.

Warming up of ion (II) to 10° effects dehydration to ion (I) and subsequent formation of oligomers (IV).
Photoreactions of aromatic compounds. Part XIV: The mechanism of the photosolvolysis of m‐nitrophenyl phosphate
Authors: de Jongh R. O. , Havinga E.
Published: September 2010

Quantum yields (φ) of photosolvolysis of m‐nitrophenyl phosphate have been determined at various hydroxyl ion concentrations and ionic strengths. The values obtained are practically the same (slightly lower) when light of 265 mμ is used as compared with those at 313 mμ, indicating that photochemical processes do not start directly from the second excited singlet, φ is independent of pH and ionic strength in neutral or weakly alkaline media (φ = 0.05 up to pH = 10‐11), suggesting that here H2O is the attacking reagent. At pH = 12 and higher there is an increase of φ with increasing [OH−] as well as with increasing ionic strength. Most probably here ‐ superimposed upon the reaction with H2O ‐, an attack by OH− takes place. The data are consistent with a simple tentative scheme (Fig. 1). 18O‐experiments indicate that water attacks at phosphorus (OP splitting) whereas OH− attacks at the ring carbon atom (CO splitting).

With o‐nitrophenyl phosphate and p‐nitrophenyl phosphate the quantum yields (in 0.01 molar NaOH) for phosphate liberation are 0.003 and 0.002, respectively; the values for nitrophenolate formation are still lower: 0.002 and 0.0004. Not only are the rates of solvolysis of the ortho‐ and para‐isomers much smaller than that of the meta compound (0.055) but also the overall reactions seem to be more complex.
The carbonyl stretching vibration of substituted benzophenones
Authors: de Roos A. M.
Published: September 2010

The carbonyl stretching absorptions of nearly fifty benzophenones were studied. Changes in the frequencies and intensities were correlated with the electronic or steric influences of the substituents, respectively.
The carbon‐oxygen stretching vibration of substituted benzhydrols and of their ethers
Authors: de Roos A. M.
Published: September 2010

The carbon‐oxygen stretching vibration in a series of substituted benzhydrols and their 2‐(dimethylamino)ethyl ethers was found to be affected by the inductive and mesomeric effects of the substituents.