bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermolytic reactions of esters. Part III: Pyruvates
Authors: Louw R. , Kooyman E. C.
Published: September 2010

Whereas pyruvic acid smoothly decarboxylates in the vapour phase to give acetaldehyde, methyl pyruvate is much more stable. Between 440 and 480°, carbon monoxide is eliminated leading to methyl acetate.

In an excess of toluene, allyl pyruvate reacts much faster than the methyl ester, giving large proportions of CO2, CO and CH4; 4‐phenyl‐1‐butene and bibenzyl are also important products. Decomposition thus resembles that of allyl acetate11. However, the pyruvate reacts some thousand times more rapidly, the activation energy being 12 kcal · mole−1 lower. This suggests the first step of allyl pyruvate breakdown to be a multiple fission into acetyl, CO2 and allyl. Analogously, benzyl pyruvate decomposes much faster than the corresponding acetate.

In an Appendix, kinetic data on allyl and benzyl esters are discussed on the basis of ‐ known or derived ‐ heats of formation; it would appear that consistency is not always satisfactory.
α‐thiopyran‐1,1‐dioxide: A re‐examination of the structure of γ‐thiopyran‐1,1‐dioxide
Authors: Molenaar E. , Strating J.
Published: September 2010

The “γ”‐thiopyran‐1,1‐dioxide, described previously1,2, has proved to be α‐thiopyran‐1,1‐dioxide, as was definitely established by an X‐ray diffraction study as well as by the synthesis of the α‐isomer by an independent route.
NMR kinetic investigation of the system norbornadiene‐μ‐dichloro dirhodium dinorbornadiene. Occurrence of a five‐coordinated rhodium complex
Authors: Volger H. C. , Hogeveen H.
Published: September 2010

NMR spectra of solutions containing norbornadiene (N) and μ‐dichloro dirhodium dinorbornadiene (Rh2N2Cl2) at low temperatures (< − 40°C) show the presence of a new species, a five‐coordinated rhodium dinorbornadiene chloride (RhN2Cl). It is formed according to

Rh2N2Cl2 + 2 N ⇌ 2 RhN2Cl.

At higher temperatures (−40° to + 100°C) line broadening is observed, indicating the occurrence of rapid exchange processes. From the data the following mechanism is deduced: a slow reaction (by one or two steps) of the dimeric complex with one mole of N

Rh2N2Cl2 + N ⇌ RhN2Cl + RhNCl,

and a subsequent fast reaction yielding a second mole of RhN2Cl

RhNCl + N ⇌ RhN2Cl.
Isotope effects in the chlorination of naphthalene
Authors: de La Mare P. B. D. , Lomas J. S.
Published: September 2010

The chlorination of naphthalene shows an inverse deuterium isotope effect, the reaction of naphthalene being slower than that of octadeuterionaphthalene by a factor of 0.85. The product‐forming stages are also subject to a deuterium isotope effect which influences the partitioning between addition and substitution; the most direct interpretation of the results is that the values of kH/kD for the stages of proton‐loss are subject to a normal deuterium isotope effect, with kH/kD ⦔ 1.4.
Chemistry and spectroscopy in strongly acidic solutions. Part XIII: Spectroscopic observation of protonated nitroalkanes
Authors: Hogeveen H.
Published: September 2010

Some protonated nitroalkanes in HF‐BF3 and HF‐SbF5 solutions have been observed by NMR spectroscopy. The added proton on the NO2 group absorbs at extremely low field (δ = 16.8‐17.5 ppm from TMS). This deshielding effect is probably caused by both the positive charge and the magnetic anisotropy of the NO2 group. IR data show a parallel between RNO2H⊕‐RNO2 and RCOOH‐RCOO⊖ stretching absorptions. The thermal decomposition of protonated 2‐nitropropane is briefly discussed.
NMR spectra and configuration of phenylallyl and related anions
Authors: Heiszwolf G. J. , Kloosterziel H.
Published: September 2010

A number of phenyl‐substituted allyl anions and corresponding isoelectronic oxaallyl anions have been obtained by reacting phenyl‐substituted propenes, phenylacetaldehyde and benzyl methyl ketone with potassium amide in liquid ammonia.

The NMR spectra of the anions are decribed. They yield information on the distribution of the negative charge and on the configurations. The configurational stability is also discussed.
The crystal structure of 6,6′‐methylenediphenanthridine
Authors: van Thuijl J. , Romers C.
Published: September 2010

The crystal structure of 6,6′‐methylenediphenanthridine (I), C27H18N2, has been determined from X‐ray diffraction data collected at ‐180°. The crystals are monoclinic; the space group is P21/c with a = 9.52, b = 15.4, c = 6.66 Å, β = 100°, and Z = 2. The planar molecules have a centre of pseudosymmetry coinciding with centres of symmetry in the lattice. The structure being disordered no extensive structure determination has been carried out. Is was found that tetrabenz[a,c,h,j]anthracene (II) is isomorphous with I.
Conversions of sarcosine and pipecolic acid with phenyl and methyl isothiocyanate
Authors: Beyerman H. C. , Maat L. , Sinnema A. , van Veen A.
Published: September 2010

Sarcosine and pipecolic acid give with phenyl isothiocyanate in an alkaline medium according to the Edman method “abnormal” adducts, the structures of which are elucidated amongst others with the aid of spectroscopic data. In ethanol the 3‐phenyl‐2‐thiohydantoins are formed from the same reactants.

With methyl isothiocyanate on the other hand sarcosine and pipecolic acid always give the 3‐methyl‐2‐thiohydantoins, both in an alkaline medium and in ethanol.

In the literature contradictions are to be found about the structure of the reaction product of the ethyl ester of pipecolic acid with phenyl isothiocyanate. From our investigation it appears that invariably the phenylthiohydantoin is formed.

The proton magnetic resonance spectra of 3‐phenyl‐2‐thiohydantoins of some amino and imino acids are discussed.
Natural chromones. Part VIII: The synthesis of some linear chromonofurancarboxylic acids. A novel total synthesis of visnagin
Authors: Badawi M. M. , Fayez M. B. E.
Published: September 2010

A new synthesis of visnagin (I) has been realised by condensation of 6‐formyl‐7‐hydroxy‐5‐methoxy‐2‐methyl‐chromen‐4‐one (II) or its 5‐hydroxy analogue (X) with diethyl bromomalonate and subsequent elimination of the ethoxycarbonyl groups from the resulting intermediates III and IV.
Preparation of thioamides from alkynethiolates and amines
Authors: Schuijl P. J. W. , Brandsma L.
Published: September 2010

Thioamides RCH2C = S(NR2′) have been prepared in good yields by adding ethereal solutions of lithium alkynethiolates RC ≡ CSLi to an excess of an amine and t‐butyl bromide.
The conformation of non‐aromatic ring compounds.: Part 42. Carbon‐halogen stretching frequencies and conformation of 1‐halogeno‐ and 1‐alkyl‐1‐halogenocyclopentanes
Authors: Buys H. R. , Altona C. , Havinga E.
Published: September 2010

The infrared and Raman spectra of 1‐halogeno‐(1‐alkyl)cyclopentanes have been recorded. It is concluded that the conformations with the halogen atom in axial position predominate in solution, the substituents occupying the most puckered part of the ring. For the 1‐halogenocyclopentanes this observation is confirmed by the NMR spectra. The bands assigned to the equatorial C‐halogen stretching modes are found to be much broader than those due to the axial ones, which is ascribed to a less defined geometry of the equatorial conformers.
Ketene S,N‐acetals from thioamides
Authors: Schuijl P. J. W. , Bos H. J. T. , Brandsma L.
Published: September 2010

1‐Dialkylamino‐1‐alkylthio‐1‐alkenes RCH=C(SR″) (NR′2) with R = H or alkyl and R′, R″ = alkyl have been obtained in good yields by treatment of thioamides RCH2C(= S) (NR'2) with one equivalent of potassium amide in liquid ammonia and subsequent alkylation with alkyl bromides R″Br.
A semi‐empirical energy‐level diagram for octahedral, Nickel(II) Complexes
Authors: Reedijk J. , van Leeuwen P. W. N. M. , Groeneveld W. L.
Published: September 2010

An energy diagram for Ni(II) in octahedral environment is constructed from spectral data of a large number of nickel complexes, with the aid of ligand‐field theory. These complexes are placed in a so‐called “Tanabe‐Sugano” series, according to increasing values of Dq/B.

Two empirical relations are introduced. One relation between Dq/B and the shape of the second absorption band; and one relation between Dq/B and λ/B.
Oxidation of three N,N′‐diacetyl‐2‐deoxyinosadi‐amines‐1,3 with periodic acid and a tridentate complex of the cis‐cis isomer
Authors: Dijkstra D.
Published: September 2010

The reaction between the periodate ion and 1,2,3‐triols has been studied using substrates in which the hydroxyl groups are attached to a six‐membered ring with a fixed “chair” conformation. The behaviour of the trans‐trans, the cis‐trans and the cis‐cis‐isomers is in line with Barker and Shaw's views on the possible formation of a tridentate complex.
Preparation and some properties of trimethylaminemethylenetriphenylborane
Authors: Bickelhaupt F. , Barnick J. W. F. K.
Published: September 2010

Trimethylaminemethylenetriphenylborane (IV) has been prepared and its structure proved by degradation reactions. Its thermal stability is intermediate between that of the corresponding sulfur and phosphorus compounds.
The crystal and molecular structure of 1,3,5,7‐tetramethoxy‐2,6‐dioxa‐adamantane (C12H20O6)
Authors: Kanters J. A. , Hulscher J. B.
Published: September 2010

Crystals of 1,3,5,7‐tetramethoxy‐2,6‐dioxa‐adamantane (C12H20O6) are orthorhombic (Pbcn) with a = 10.31, b = 13.23 and c = 9.23 Å; there are 4 molecules in the unit cell; the asymmetric unit consists of one half molecule. 460 independent three‐dimensional intensities were collected on a Nonius retigraph. The structure was solved by a systematic sign correlation procedure and refined by using least squares methods to R =.062. The coordinates of the carbon and oxygen atoms were refined with anisotropic thermal motion, those of the hydrogen atoms with a constant isotropic thermal parameter. The geometry of the adamantane skeleton of the molecule does not differ greatly from that of adamantane, in spite of the fact that two methylene carbon atoms are replaced by two oxygen atoms. The molecule has a two‐fold axis coinciding with the space‐group two‐fold axis.
Mono‐ and dicarbonium ions of β‐dicarbonyl compounds (ketones, carboxylic ACIDS and esters)
Authors: Brouwer D. M.
Published: September 2010

A PMR spectroscopic study is described of the protonation of a series of β‐dicarbonyl compounds (Table I) in HF‐SbF5. At high acidity they form 1,3‐dicarbonium ions, except in the case of compounds VI and VII. At lower acidity monocations are formed: diketones give allylic type monocations, and keto esters, dicarboxylic esters and acids give alkoxyhydroxy and dihydroxy‐carbonium ions, respectively.

Between these two groups there is a marked difference in spectroscopic behaviour of solutions containing comparable amounts of mono‐ and dications. Equilibration of mono‐ and dications is “slow” with the diketones and “fast” with the other compounds.

For the compounds studied, the equilibrium constants KB* = [dication]/[monocation] [H2F+] vary from less than 10−2 for tri‐ and hexafluoroacetylacetone to more than 107 for ethyl acetoacetate. The monocation‐dication equilibrium systems are useful as indicators and buffers at high acidity; they are unreactive towards alkylcarbonium ions. A lower limit has been established for the basicity of isobutene, which turns out to be much more basic than benzene.
On silicon tritelluride, Si2Te3, and alleged phosphorus tritelluride
Authors: Haneveld A. J. Klein , van der Veer W. , Jellinek F.
Published: September 2010

Silicon(III) telluride, Si2Te3, which was formerly regarded as SiTe2, is hexagonal with a = 7.429 Å; c = 13.471 Å; c/a = 1.813. There is a pronounced subcell with a′ =1/3 √3 a, c′ = 1/2 c. The tellurium atoms are in a hexagonal close packing; the Si atoms occupy tetrahedral and probably also octahedral holes in this packing, but their detailed arrangement could not be determined unambiguously. The alleged compound P2Te3 has been found to be a mixture of tellurium and amorphous red phosphorus.
Synthesis of oxytocinoic acid and oxytocin on a solid support VIA triazolides from active esters
Authors: Beyerman H. C. , Boers‐Boonekamp C. A. M. , van den Brink‐Zimmermannová H. Maassen
Published: September 2010

The syntheses are described of S,S′‐dibenzyloxytocinoic acid and S,S′‐dibenzyloxytocin on copolystyrene‐divinylbenzene according to the solid‐phase method of Merrifield, but using the triazolide method of coupling developed in this Laboratory. Cleavage with amide formation of the nonapeptide‐polymer bond by ammonolysis proceeded quite satisfactorily with methanolic ammonia. The nonapeptides were obtained in the pure state by mere crystallization.

The conversions of the linear nonapeptides into the cyclic compounds oxytocinoic acid and the hormone oxytocin are known.
Thermal isomerisation of trimethylcyclopentadienes
Authors: de Haan J. W. , Kloosterziel H.
Published: September 2010

The thermal behaviour of 1,5,5‐ and 2,5,5‐trimethylcyclopentadiene (TMCPD) has been investigated. The following isomerisations have been observed and their activation parameters determined:

Evidence is presented that these reactions occur by an intramolecular, sigmatropic 1,5 shift of a methyl group.
Correlations between molecular structure and mass spectra. Part II: The mass spectrometric fragmentation behaviour of isopentyl cyanide and its deuterium analogues
Authors: Rol N. C.
Published: September 2010

The fragmentation of the isopentyl cyanide ion has been investigated by means of deuterium labelling and precision mass measurements. The results throw light on interesting fragmentation reactions. Comparisons with the reactions postulated to account for the mass spectra of cyanides, especially those of isohexyl cyanide and its deuterium analogues, reveal some unexpected features.
Structure and physical properties of aluminium alkoxides: 1. Mass spectra of aluminium isopropoxides
Authors: Fieggen W. , Gerding H. , Nibbering N. M. M.
Published: September 2010

The mass spectrum of aluminium isopropoxide has been investigated using an AEI‐MS 9 mass spectrometer.

The results indicate that the vapour of the solid consists largely of tetramer species; dimer and trimer are possibly present also in minor quantities.

Probable fragmentation schemes are deduced from comparison of mass spectra of unlabelled and deuterated samples (deuterated at the secondary carbon atom of the isopropyl group). The tetramer molecular ion loses an isopropoxy radical or, successively, a methyl radical and a molecule of acetaldehyde, followed by the elimination of di‐isopropyl ether. A mechanism for this reaction is proposed. The further fragmentation may involve the loss of propene, di‐isopropyl ether and/or aluminiumoxide isopropoxide.
Palladium‐Catalysed reactions of unsaturated compounds in non‐aqueous solvents: The PdII‐catalysed halogen displacement in vinyl chloride by carboxylate and alcoholate
Authors: Kohll C. F. , van Helden R.
Published: September 2010

In the presence of catalytic amounts of divalent palladium salts vinyl chloride reacts with acetate ions in acetic acid or dimethylformamide solution to produce vinyl acetate in high yield. The reaction was found to be first‐order both in catalyst and in acetate concentration. Chloride anions inhibit the reaction by reducing the effective catalyst concentration by formation of the tetrachloropalladium complex.

The mechanism of the reaction is discussed in terms of a displacement of chloride by acetate via a π‐olefin‐PdII complex. The vinylation reaction is considerably accelerated by addition of catalytic amounts of ferric acetate/lithium chloride (molar ratio 1).

Also discussed is the influence on the reaction of the solvent and of various transition metal salts. The palladium‐chloride‐catalysed halogen displacement in 2‐chloropropylene by acetate ions in acetic acid was found to produce isopropenyl acetate and acetone + acetic anhydride, which indicates that attack of acetate occurs at the carbon atom carrying the chlorine. Reaction of alcohols with vinyl chloride in the presence of a base (alcoholate or tert‐amine), using palladium chloride as catalyst yields acetaldehyde dialkylacetales. Halogen exchange in vinyl bromide by chloride in dimethylformamide solution using palladium chloride as catalyst proved to be possible.
Mechanistic aspects of the palladium (II)‐catalysed synthesis of vinyl acetate from vinyl chloride
Authors: Volger H. C.
Published: September 2010

Labelling with deuterium has shown that in the conversion of vinyl chloride into vinyl acetate by sodium acetate in glacial acetic acid at 60‐70°C in the presence of catalytic amounts of palladium chloride, (i) the acetate enters at the chlorine‐carrying carbon atom and(ii) the geometric configuration of the vinyl chloride is lost in the vinyl acetate produced. An addition‐elimination mechanism is proposed.
The determination of the solubilities of some n‐alkanes in water at different temperatures, by means of gas chromatography
Authors: Nelson H. D. , de Ligny C. L.
Published: September 2010

Gas chromatography has been used to determine the solubility in water of pentane, hexane, heptane and octane at different temperatures. From the results the standard free enthalpy, enthalpy and entropy of solution have been calculated.
Complexes with ligands containing nitrile groups: Part VI: Some methyl cyanide adducts of metal chlorides
Authors: Reedijk J. , Groeneveld W. L.
Published: September 2010

Seven new metal chloride adducts with methyl cyanide, viz. MgCl2(CH3CN)2, NiCl2(CH3CN), CdCl2(CH3CN), GaCl3(CH3CN)2, InCl3(CH3CN)2, TlCl3(CH3CN)2 and SnCl4(CH3CN)3, are described.

Methyl cyanide coordinated via the nitrogen in these compounds was demonstrated with the aid of infrared spectra. Further characterization and identification of the adducts was obtained from X‐ray powder diagrams, ligand‐field spectra, Raman spectra, far‐infrared spectra and conductivity data.
Polynuclear heterocyclic systems. Part VI: Synthesis of perhydropyridazo[1,2‐a]cinnoline
Authors: de Waard E. R. , Neeter R. , Pandit U. K. , Huisman H. O.
Published: September 2010

In a model study directed towards the synthesis of 5,10‐diazasteroids, piperidazine was condensed with 2‐methoxycarbonylmethylcyclohexanone (2) to give decahydro‐Δ7a(11a)‐6‐oxopyridazo[1,2‐a]cinnoline (4). Reduction of 4 with lithium aluminium hydride yielded decahydro‐Δ7a(11a)‐pyridazo[1,2‐a]cinnoline (5). Subsequent reduction of 5, either catalytically or with sodium borohydride, proceeded stereospecifically to the perhydropyridazo[1,2‐a]cinnoline (8), with B/C cis ring fusion.
Byproducts in the cyclization of ψ‐ionone to β‐ionone; structural determination of two new ionone isomers
Authors: Kruk C. , de Boer Th. J. , Haring H. G. , Ter Heide R. , Boelens H.
Published: September 2010

It is shown that the well known acid‐catalysed cyclization of ψ‐ionone leads to the formation of small amounts of the spiro‐dihydrofuran XV, the cyclohexadienylic ketone XVI, and the unsaturated ketones XVIIa and b. These are all isomers of ionone; the first two have hitherto not been described in the literature, whereas XVII has been obtained by a different route as a mixture of cis‐trans isomers.

The structural proof of these products is based mainly on spectroscopic data.
Phase transitions in the nickel selenide Ni3Se2 and related phases
Authors: Stevels A. L. N. , Bouwma J. , Wiegers G. A. , Jellinek F.
Published: September 2010

The thermal behaviour of Ni3Se2 has been studied by differential thermal analysis and by high‐temperature X‐ray diffraction. Ni3Se2 is rhombohedral at low temperature and face‐centred cubic at high temperatures. The transition between the two forms shows a strong thermal hysteresis. When heating, the transition occurs at about 600° C. On cooling the face‐centred cubic form is transformed to a metastable body‐centred tetragonal form at about 560°; this form converts itself to the stable rhombohedral form at a temperature between 550° and 510° (depending on the cooling rate). The metastable form is stabilized if the metal is partly substituted by Co or Fe, or if part of Se is substituted by Te. A corresponding metastable form of Ni3S2 could not be detected. The various modifications observed for Ni3S2,Ni3Se2 Ni3(Se1.6,Te0.4) and Ni3Te2 are compared.
Determination and interpretation of the differential titration curves of proteins: The differential curves of bovine methemoglobin, CO‐hemoglobin and serum albumin
Authors: de Bruin S. H. , van Os G. A. J.
Published: September 2010

In this paper a refinement of the usual experimental titration procedure of proteins is described, by means of which the differential titration curve can be obtained with good accuracy. From this curve the positions of the inflection points of the normal titration curve can be localised with better precision, and, as is shown, the analysis of the differential curve has certain advantages above that of the normal curve. The capabilities of experimental and analysing procedure are illustrated by results, obtained with the proteins bovine methemoglobin (MetHb), bovine CO‐hemoglobin (HbCO) and bovine serum albumin (BSA).
The conformation of non‐aromatic ring compounds. XLVIII: The crystal structure of trans‐syn‐trans‐2,3,5,6‐tetrachloro‐1,4‐dioxane
Authors: Rutten Elisabeth W. M. , Nibbering N. , Macgillavry Caroline H. , Romers C.
Published: September 2010

Crystals of trans‐syn‐trans‐2,3,5,6‐tetrachloro‐1,4‐dioxane are monoclinic prismatic. The space group is P21/n, a = 6.724, b = 7.552, c = 7.626 Å, β = 93.13° and Z = 2. The structure has been solved by Patterson methods and refined by use of integrated photographic copper data measured with a microdensitometer.

The molecule has a chair conformation with all chlorine atoms in axial positions and with symmetry ī. Due to steric repulsions by the halogen atoms the chair is rather flat. The mean endocyclic torsional angle is 40°. In agreement with similar observations in other dioxane compounds the C‐Cl bond lengths (average value 1.823 Å) are rather long.
Semi‐empirical prediction of bond lengths and conformations
Authors: Dallinga G. , Ros P.
Published: September 2010

For a number of cyclic hydrocarbons we compared overlap populations, obtained by applying a Mulliken population analysis to the results of an extended Hückel calculation, with experimental bond lengths. We analysed the effect of a refinement, viz. the introduction of non‐bonded interactions. Further, we discuss the use of orbital energies in predicting relative stabilities of isomers and conformers.
Palladium‐catalysed reactions of unsaturated compounds in non‐aqueous solvents: Synthesis of vinyl acetate via palladium salt/ethylene complexes
Authors: van Helden R. , Kohll C. F. , Medema D. , Verberg G. , Jonkhoff T.
Published: September 2010

The reaction of ethylene with palladium acetate in acetic acid solvent produces vinyl acetate. The rate of this reaction increases considerably upon addition of small amounts of sodium acetate, lithium chloride or lithium chloride/ferric acetate to the system. The reaction is first‐order with respect to both the palladium acetate and the catalyst (NaOAc, LiCl, LiCl·Fe(OAc)3) concentration. In reactions starting from PdCl2 and NaOAc the rate was found to be proportional to the PdCl2 and NaOAc concentrations. In addition, in one case (LiCl· Fe(OAc)3) the rate was shown to be proportional to the ethylene concentration.

A mechanism is proposed according to which the reaction proceeds via species of the type C2H4· PdOAcX2− ; vinyl acetate is formed through displacement of a hydrogen atom in the olefin molecule by coordinated acetate.

The overall rate was found to be strongly influenced by the ligands bound to the metal; it increases in the order:

The effect of ferric acetate on the rate is tentatively explained on the basis of an increased transfer of charge in the intermediate C2H4· PdOAcX2− complex. The fact that in the displacement of Cl− by acetate in the corresponding vinyl chloride complex (C2H3Cl. PdOAcCl2−) the overall rate is lower is attributed to the formation of vinyl chloride/PdOAcCl2− complexes proceeding less readily than that of ethylene complexes.

In the LiCl‐catalysed reaction the formation of vinyl acetate was found to be completely inhibited at high concentrations of chloride ions with respect to palladium acetate; under these conditions ethylene is dimerized to butylenes.

Depending on the conditions of the reaction various by‐products are formed: acetaldehyde, ethylidene diacetate, ethyleneglycol acetates, butenes. The formation of these products is discussed in relation with other studies.

Finally, the results are presented of some studies on the oxidation with oxygen ‐ of palladium metal in acetic acid to palladium acetate.
α‐Diazosulfones as proton donors in hydrogen bonding
Authors: Engberts J. B. F. N.
Published: September 2010

The PMR spectra of three aryl‐ and two alkyl‐sulfonyldiazomethanes in aliphatic and aromatic solvents have been studied. Solvent effects on the chemical shift of the methine proton indicate that this proton participates in rather strong hydrogen bonding. Relative to an inert solvent like carbon tetrachloride, the observed solvent shifts are mainly dependent on acceptor ability and magnetic anisotropy effect of the solvent molecules. In solvents of weak acceptor ability, intermolecular association between α‐diazosulfone molecules results in concentration dependent chemical shifts of the methine proton.
Ring transformations in reactions of heterocyclic compounds with nucleophiles (III): Conversion of pyrimidine and some of its methyl derivatives by hydrazine and by methylhydrazine sulfate into pyrazoles and methylpyrazoles
Authors: van der Plas H. C. , Jongejan H.
Published: September 2010

Investigations on ring contraction of pyrimidine and some of its homologues into pyrazoles have been extended.

When pyrimidine, 4‐methyl‐ and 4,6‐dimethylpyrimidine are allowed to react with hydrazine, pyrazole, 3(=5)‐methylpyrazole and 3,5‐dimethyl‐pyrazole, respectively are formed in excellent yields. The same compounds, when treated with methylhydrazine sulfate yield 1 ‐methylpyrazole, an isomeric mixture of 1,3‐ and 1,5‐dimethylpyrazole and 1,3,5‐trimethylpyrazole, respectively. The quaternary salts 1‐methylpyrimidinium iodide and 1,4,6‐trimethylpyrimidinium methyl sulfate are converted by hydrazine into pyrazole and 3,5‐dimethylpyrazole.

A mechanism of this ring transformation, involving an open‐chain intermediate, is proposed.
Ring transformation in reactions of heterocyclic halogeno compounds with nucleophiles (XIII): Conversion of some 5‐substituted 4‐chloro‐2‐phenylpyrimidines into 4(5)‐substituted 2‐phenylimidazoles
Authors: van Meeteren H. W. , van der Plas H. C.
Published: September 2010

5‐Amino‐4‐chloro‐2‐phenylpyrimidine and 4‐chloro‐5‐methyl‐2‐phenylpyrimidine are converted into 4(5)‐cyano‐2‐phenylimidazole and 4(5)‐ethynyl‐2‐phenyl‐imidazole, respectively, by reaction with potassium amide in liquid ammonia at ‐ 33°.
Fragmentation of molecular ions of fatty acid methyl esters into methoxycarbonylalkyl ions by electron impact
Authors: Sonneveld W. , van der Steen D. , Pabon H. J. J.
Published: September 2010

The fragmentation of the molecular ions of methyl octadecanoates into methoxycarbonylalkyl ions with m/e = 143 and 199 has been investigated. The contributions of three reaction types are determined with esters labelled with13C at the 8 and 14 positions. The required methyl 8‐ and 14‐13C‐octadecanoates have been synthesized by coupling a methoxycarbonylalkanoyl chloride with thiophene, followed by Wolf‐Kishner reduction, esterification, introduction of the isotopic carbon atom by acylation, again reduction and desulfurization.
Structure analysis by nmr spectroscopy of a quinone methide trimer formed by oxidation of 4‐methoxy‐2,6‐dimethylphenol
Authors: Westra J. G. , Huysmans W. G. B. , Mijs W. J. , Gaur H. Angad , Vriend J. , Smidt J.
Published: September 2010

A detailed structure analysis by proton magnetic resonance spectroscopy has been made of the main oxidation product of 4‐methoxy‐2,6‐dimethylphenol, ano‐quinone methide trimer. Several long range spin‐spin interactions of aromatic or vinylic protons with methoxy or aliphatic protons were clearly demonstrated by multiple resonance techniques.
A new swelling pressure osmometer
Authors: van de Kraats E. J.
Published: September 2010

A swelling pressure osmometer has been constructed in which gels can swell isotropically in interchangeable swelling chambers having accurately fixed dimensions. The gels are in contact with the pure diluent via a porous steel disc. The swelling pressure is balanced and measured directly by a mercury column which is servocontrolled by a displacement transducer attached to a thin platinum foil forming one side of the swelling chamber. The mercury column exerts a counter‐pressure on the platinum foil. If the mercury column is replaced by another counter‐pressure device, swelling pressures as high as one hundred atmospheres or as low as one hundredth of an atmosphere can be measured with an accuracy of about 1 ‰.

This method of pressure detection is in principle also applicable to the determination of pressure changes at constant volume, such as occur, for example, in the study of the kinetics of phase transitions and equilibria.
Synthesis of 2‐chloro‐[2‐14C] naphthalene and [2‐14C] naphthalene
Authors: van der Jagt P. J. , den Hollander W. , van Zanten B.
Published: September 2010

The reaction of indene with [14C]dichlorocarbene, generated from [14C]chloroform with the aid of potassium t‐butoxide, leads to the dichlorocarbene adduct. Without isolation from the reaction mixture this adduct has been converted to 2‐chloro‐[2‐14C]naphthalene with an overall yield of 60‐67%. Catalytic dehalogenation of 2‐chloro‐[2‐14C]naphthalene yields almost quantitatively [2‐14C]naphthalene. The chemical and radiochemical purity of this compound was proved to be better than 99%.
The metabolism of hydroxyanthranilic acids. Part II: The partial purification of 3‐hydroxyanthranilate oxygenase and its action on some aminocresotic acids
Authors: Cox M. C. L. , Diamond E. M. , Levy P. R.
Published: September 2010

A simple thirty‐fold purification of 3‐hydroxyanthranilate oxygenase from an acetone powder of rat liver is described. 2‐Amino‐3,4‐cresotic acid (III) resembles 3‐hydroxyanthranilic acid (I) when incubated with the enzyme; 2‐amino‐3,5‐cresotic acid (IV) is a competitive inhibitor; 2‐amino‐3,6‐cresotic acid (V) is inert.
Investigation into the conformation of a series of 2‐alkyl‐1‐(o‐alkylphenyl)cyclohexanols. Part 2: Synthesis and NMR spectra of some o‐alkylbenzyl alcohols
Authors: Timmerman H. , Zaagsma J. , Th. Nauta W.
Published: September 2010

A series of o‐alkylbenzyl alcohols was synthesised; the NMR spectra were compared with those of correspondingly substituted o‐alkylphenyl cyclohexanols in order to ascertain how the o‐alkyl substituents in the cyclohexanols investigated affect the shift of the hydroxyl proton.
Thermolytic reactions of esters. Part IV. The methyl esters of cyanoacetic, acetoacetic and malonic acid
Authors: den Tonkelaar W. A. M. , Louw R. , Kooyman E. C.
Published: September 2010

The compounds on the title proved to be more stable than their ethyl analogues, 1,2‐acid elimination being impossible. Acetic acid causes a pronounced rate enhancement. Kinetic as well as product data ‐ including the effect of added water and/or alcohols ‐ are interpreted on the basis of acetic acid catalysed enolisation as the primary step, followed by elimination of alcohol to form a ketene derivative. In the case of dimethyl malonate, this methoxycarbonyl ketene may loose a second molecule of methanol to produce carbon suboxide.
Photoreactions of aromatic compounds. Part XV: Photosolvolysis of some 5‐substituted 3‐nitrophenyl phosphates and of 3‐nitrophenyl sulfate
Authors: de Jongh R. O. , Havinga E.
Published: September 2010

Quantum yields have been determined for the photosolvolysis of 5‐chloro‐, 5‐bromo‐ and 5‐methyl‐3‐nitrophenyl phosphate in alkaline solutions of different pH and ionic strength. Quantum yields are found to be the same for light of 313 mμ and 265 mμ. The 5‐bromo‐ and 5‐methyl‐compounds show a behaviour comparable to that of 3‐nitrophenyl phosphate itself, be it with lower quantum yields under the same reaction conditions; the data suggest a shortening of the lifetime of the reacting excited species. 5‐Chloro‐3‐nitrophenyl phosphate reacts with water in the pH range studied with a relatively high quantum yield (0.15), probably due to the favourable electronic effect of the chlorine substituent. There is no indication of a photoreaction with OH−, not even in 0.1 molar NaOH and ionic strength ∼ 1; for this compound the reaction with the solvent (H2O) may be so fast that reactions with solutes (OH−) cannot compete. Another compound for which only a reaction with water and not with OH was observed, is m‐nitrophenyl sulfate. Here again, the quantum yield of photohydrolysis is high (0.5) and practically constant over the range pH2‐13. This makes it unlikely that protonation or deprotonation is one of the essential steps of the reaction. Cl−‐ and especially Br−‐ions only when present in high concentration (∼ 1 mole) quench the photosolvolysis of m‐nitroanisole (by OH−), and probably also the reaction of m‐nitrophenyl sulfate with water. This suggests that the reacting excited species is in the first singlet rather than in a triplet state.
Photolysis of alkyl aralkyl sulfides
Authors: Laarhoven W. H. , Cuppen Th. J. H. M. , Nivard R. J. F.
Published: September 2010

Reactions analogous to the photolytic formation of dibenzyl, stilbene and phenanthrene from dibenzyl sulfide have been observed on irradiation of various alkyl aralkyl sulfides. Exceptions were found in alkyl α‐alkylbenzyl sulfides containing a hydrogen atom at the β‐carbon relative to the aromatic ring. From these a dibenzyl derivative is obtained, but instead of stilbenes and phenanthrenes styrenes are formed. A possible explanation for the results is given.
Complexes with ligands containing nitrile groups. Part IX . Magnetic measurements on solid methyl‐cyanide solvates
Authors: Reedijk J.
Published: September 2010

Magnetic susceptibilities and paramagnetic resonance spectra for a number of complex solvates M(CH3CN)n2+(anion), in which M = Mn, Fe, Co, Ni, Cu, Zn, n = 4 or 6 and the anion is SbCl6−, SnCl62–, TlCl4−, FeCl4−, GaCl4−, ClO4−, have been determined.

The octahedral shape of the ions M(CH3CN)62+, with M = Mn, Fe, Co and Ni, has been confirmed. The ion Cu(CH3CN)62+ has been found to be distorted octrahedral. In Cu(CH3CN)4SnCl6 no copper‐copper interaction is found.

The spin‐orbit coupling constants for the solvated metal ions are shown to be reduced 15‐50% compared with the free metal ions.
Electron diffraction by gases: The molecular structure of bicyclo[3.1.1]heptane
Authors: Dallinga G. , Toneman L. H.
Published: September 2010

The molecular structure of bicyclo[3.1.1]heptane has been investigated by means of electron diffraction of the vapour. The molecule has one plane of symmetry and an average carbon‐carbon bond length of 1.537 Å. Details of the structure are compared with those in similar molecules and differences between the carbon‐carbon bond lengths are discussed with reference to semi‐empirical predictions based on the results of MO calculations.
Chemistry and spectroscopy in strongly acidic solutions. Part XXII: Protonation of hexamethyldewarbenzene. Interconversion of exo‐ and endo‐1,2,3,4,5,6‐hexamethylbicyclo[2.1.1]hexenyl cations
Authors: Hogeveen H. , Volger H. C.
Published: September 2010

Protonation of hexamethyldewarbenzene at low temperatures leads to formation of exo‐ and endo‐1,2,3,4,5,6‐hexamethylbicyclo[2.1.1]hexenyl cations (ratio 1:3). These ions interconvert rapidly and intramolecularly, the added proton remaining attached to the same carbon atom. The mechanism proposed for this isomerization involves tricyclic ions as intermediates. Values for the rate constant at various temperatures were obtained by comparison of the experimental NMR spectra with the computer‐simulated ones. Quenching of the ions with methanol‐sodium methoxide at low temperature afforded a number of products.
The nitration of 2‐nitro‐1,4‐di‐t‐butylbenzene: Synthesis of the three dinitro‐1,4‐di‐t‐butylbenzenes and some related compounds
Authors: Hoefnagel A. J. , Nunnink J. H. A. J. , van Veen A. , Verkade P. E. , Wepster B. M.
Published: September 2010

Nitration of 2‐nitro‐1,4‐di‐t‐butylbenzene provides a mixture from which, in addition to 2,4‐dinitro‐ and 3,4‐dinitro‐t‐butylbenzene, all three possible dinitro‐1,4‐di‐t‐butylbenzenes could be isolated. Pure 2,3‐dinitro‐ and 2,6‐dinitro‐1,4‐di‐t‐butylbenzene have been isolated for the first time. The difficult separation of a mixture of 2,6‐dinitro‐ and 2,5‐dinitro‐1,4‐di‐t‐butylbenzene was effected by using molecular sieve 10X.

The 2,6‐dinitro isomer has also been prepared starting from 2,5‐dinitro‐1,4‐di‐t‐butylbenzene.

Dipole moments and ultraviolet, infrared, and NMR data of the isomers are given and certain aspects are discussed.
Stereoselectivity in the complex formation of histidine with cobalt(II) and nickel(II)
Authors: Ritsma J. H. , van de Grampel J. C. , Jellinek F.
Published: September 2010

The stability constants of Co(II)‐ and Ni(II) complexes of L‐histidine and racemic histidine in aqueous solution have been measured. The observed difference between the stability of MDL and ML2 complexes shows a preference for the formation of the MDL molecule. The excess Gibbs energy of ½(MD2 + ML2) relative to MDL is found as 0.31 kcal/mole fir the Co(II) complex and as 0.49 kcal/mole for the Ni(II) complex.
Chemistry of acetylenic ethers 93. Photochemical additions of acetylenes (I) reactions of ketones with 1‐methylthio‐1‐propyne
Authors: Bos H. J. T. , Boleij J.
Published: September 2010

Photoaddition of aromatic ketones to 1‐methylthio‐1‐propyne affords, via C3O‐cycloaddition, 4,4‐diaryl‐3‐methylthio‐3‐buten‐2‐ones in good yields. Analogously acetone gives 4‐methyl‐3‐methylthio‐3‐penten‐2‐one (CH3)2CC(SCH3)COCH3, together with some 1,2‐bis(methylthio)‐1‐propene CH3C(SCH3)CH‐SCH3.
Solvolysis of endo‐bicyclo[3.2.1]octa‐2,6‐dien‐8‐yl derivatives
Authors: Klumpp G. W. , Ellen G. , Bickelhaupt F.
Published: September 2010

The hydrolysis of endo‐bicyclo[3.2.1]octa‐2,6‐dien‐8‐yl chloride and the acetolysis of endo‐bicyclo[3.2.1]octa‐2,6‐dien‐8‐yl tosylate have been investigated. The importance of anchimeric assistance in these solvolyses has been estimated and compared with other homoallylic systems.
Synthesis of the α,α′‐dehydrodimer of methyl octanoate and the β,β′‐dehydrodimer of methyl nonanoate and their mass and NMR‐spectra
Authors: Voet W. J. E. , Zeilstra E. M.
Published: September 2010

Dimethyl 7,8‐tetradecanedicarboxylate and 7,8‐di(methoxycarbonylmethyl)‐tetradecane have been synthesized. 2‐Bromooctanoic acid ester was coupled to ethyl cyanoacetate and the reaction product converted with hexyl iodide. Saponification, decarboxylation with copper and acid hydrolysis yielded the octanoic acid dehydrodimer. 7,8‐Di(hydroxymethyl)tetradecane was converted with tosyl chloride and the product treated with KCN to give a dicyanide.

The purity of the compounds was checked with GLC. Their mass spectra showed different characteristic fragmentation patterns. In the NMR spectra δ‐shift values were different.
Synthesis and some properties of 1‐alkenyl alkyl disulfides and di(1‐alkenyl) disulfides
Authors: Wijers H. E. , Boelens H. , van der Gen A. , Brandsma L.
Published: September 2010

The synthesis of 1‐alkenyl alkyl disulfides, R‐CH=CH‐S‐S‐R′, and di(l‐alkenyl) disulfides, R‐CH=CH‐S‐S‐CH=CH‐R, with R = H or alkyl and R′ = alkyl, is reported. Reaction of 1‐alkenethiolates R‐CH=CH‐SLi(Na), prepared in situ by cleavage of 1‐alkenyl alkyl sulfides with alkali metal in liquid ammonia, with S‐alkyl alkanethiosulfonates, R′‐S‐SO2‐R′ or alkyl thiocyanates, R′‐SCN, affords 1‐alkenyl alkyl disulfides in excellent yields. Reaction of alkenylmagnesium halides, R‐CH=CH‐SMgCl(Br), likewise leads to formation of 1‐alkenyl alkyl disulfides, but yields are moderate. Treatment of l‐ethylthio‐2‐propenylthioethene, CH3‐CH=CH‐S‐CH=CH‐S‐C2H5, with podium amide in liquid ammonia, results in formation of sodium 1‐propenethiolate which reacts with S‐propyl propanethiosulfonate to give propenyl propyl disulfide in good yield. Oxidation in situ of 1‐alkenethiolate anions with iodine affords the corresponding di‐(l‐alkenyl) disulfides.
Peptide derivatives related to the active site of some hydrolytic enzymes: IV. Tetrapeptide derivatives containing D‐serine
Authors: Kienhuis H. , van der Holst J. P. J. , Verweij A.
Published: September 2010

The syntheses of derivatives of the L‐L tetrapeptides Gly‐Asp‐Ser‐Gly and Gly‐Glu‐Ser‐Gly have been described in preceding communications

H. Kienhuis, A. van de Linde, J. P. J. van der Holst and A. Verweij, Rec. Trav. Chim. 80, 1278 (1961).

A. van de Linde, H. Kienhuis, A. Verweij and J. P. J. van der Holst, ibid. 80,1305 (1961).

H. Kienhuis, J. P. J. van der Holst and A. Verweij, ibid. 83, 1129 (1964).

. These compounds were used as models for esterases. In order to study the effects of configuration and conformation in our model reactions, we synthesised the diastereoisomeric peptide derivatives containing D‐serine instead of L‐serine. In Fig. 1 the difference of the relative positions of the side chains of aspartic acid and serine is demonstrated for the stretched forms of the L‐L and L‐D peptides.
Nitromethane as a ligand. Part II: Complexes with some divalent metals and the tetrachloroferrate (III) anion
Authors: Driessen W. L. , Groeneveld W. L.
Published: September 2010

Five new complexes are reported with nitromethane as a ligand, viz. [M(CH3NO2)6]2+[FeCl4]2− where M is Mg(II), Mn(II), Fe(II), Co(II) and Ni(II). They are identified by chemical analysis and with the aid of physical measurements.

The NO2 rocking mode (BI) shifts to higher frequencies; no shift in the NO stretching frequencies has been observed.

In the far infrared a metal‐dependent absorption band is observed, which is attributed to the metal‐ligand stretching vibration.

It is noticed that the relative size and stability of the anion influences such quantities as formation of the complex in the first place, shifts in ligand vibrational frequencies, ligand field transitions.
The oxidation of dithiocarbamato complexes of nickel, copper and zinc
Authors: Brinkhoff H.C. , Cras J.A. , Steggerda J.J. , Willemse J.
Published: September 2010

Oxidation of N,N‐di‐n‐butyldithiocarbamato (bu2dtc) complexes of Cu(I), Ni(II), Zn(II), Cd(II) and Hg(II) is reported. Oxidation of Ni(bu2dtc)2 with Cl2, Br2, or of NiX2 (X = Cl, Br, NO3) with N,N,N′,N′‐tetra‐n‐butylthiuram disulfide (bu4tds) gives complexes of composition [Ni(bu2dtc)3]X. These compounds are diamagnetic and dissolve in nitrobenzene as 1:1 electrolytes, their UV spectra resemble that of the iso‐electronic Co(bu2dtc)3. The experimental data are in accord with the assumption that in these compounds Ni(IV) flow spin d6) is surrounded by 6 S atoms in octahedral symmetry. The analogous selenium compound tris (N, N‐di‐n‐butyldiselenocarbamato) nickel(IV) bromide, having the same properties as the thio compounds, can also be prepared. Oxidation of Cu(bu2dtc) with Cl2 or Br2 yields paramagnetic products with the composition CuX3(bu2dtc), in which Cu also has the formal oxidation number + 4, but the structure of these compounds is still obscure. Oxidation of Zn(bu2dtc)2 and the corresponding Cd and Hg compounds yields products, the analysis of which suggests the composition MX2(bu2dtc)2 (M = Zn, Cd or Hg, X = Br or I), but infrared studies indicate that the dithiocarbamato ligands of the starting substances are oxidized to bu4tds, which in the reaction products is coordinated to the metal in its normal oxidation state + 2.
The vibrational spectra and structures of the compounds KNO2S2O7 and NOHS2O7
Authors: Gerding H. , Gijben H. , Stufkens D.J.
Published: September 2010

The infrared absorption and Raman spectra of the compounds KNO2S2O7 and NOHS2O7 have been studied. It follows from these spectra that both compounds are ionic and should be written as K+NO2+S2O7− and NO+HS2O7−, respectively.
Isomerization of cyclic olefins in basic media. Part 3: The double bond migration of [l‐14C]‐cyclohexene.
Authors: Tjan S.B. , Steinberg H. , de Boer Th. J.
Published: September 2010

The double bond migration of [l‐14C]‐cyclohexene under the influence of potassium tert‐butoxide in dimethyl sulfoxide has been studied at three temperatures. The activation parameters are ΔH‡ = 19.5 ± 0.4 kcal/mole and ΔS‡ = −24.6 ±0.6 e.u.

The reaction is first order in olefin and 3/2 order in base up to about 0.3 molar. It is postulated that in dimethyl sulfoxide a small amount of base is present as a catalytically ineffective trimer, which dissociates into various active basic species, thus explaining the 3/2 order. At concentrations above 0.3 molar the kinetic order decreases, presumably because of ineffective solvation of charged species by lack of solvent molecules.
Ring transformations in reactions of heterocyclic compounds with nucleophiles. Part. XVI: A tracer study of the formation of 4(5)‐ethynyl‐2‐phenylimidazole from 4‐chloro‐5‐methyl‐2‐phenylpyrimidine by potassium amide in liquid ammonia
Authors: van Meeteren H.W. , van der Plas H.C. , de Bie D.A.
Published: September 2010

Treatment of 4‐chloro‐5‐methyl‐2‐phenyl‐[4‐14C]pyrimidine with potassium amide in liquid ammonia yields a 4(5)‐ethynyl‐2‐phenylimidazole, in which the ethynyl group is attached to the radioactive carbon atom. This result indicates that during ring contraction the bond between C5 and C6 of the pyrimidine ring is broken.
Mössbauer effect of octahedral iron(II) solvates
Authors: Reedijk J. , van Der Kraan A. M.
Published: September 2010

Mössbauer measurements for some compounds of the formula Fe(ligand)6(ClO4)2 are reported. The values for the chemical shift and the quadrupole splitting are compared with literature data. For several ligands the chemical shift is compared with the spectrochemical parameters Dq and β. No simple relationship between the chemical shift and either Dq, or β, or Dq/β could be observed.
Heterogeneous and homogeneous hydrogenation of hexamethyl‐Dewar‐benzene
Authors: van Bekkum H. , van Rantwijk F. , van Minnen‐Pathuis G. , Remijnse J. D. , van Veen A.
Published: September 2010

The heterogeneous hydrogenation of hexamethyl‐Dewar‐benzene (1) over various transition metal catalysts has been studied. At 25° selective (> 95%) cis,exo addition of hydrogen was observed yielding 1,2,3,4,5 endo, 6 endo‐hexamethylbicyclo[2.2.0]hex‐2‐ene (2). Hydrogenation at 50°, of 2 and of 1,2,3,4,5 endo, 6 exo‐hexamethylbicyclo[2.2.0]hex‐2‐ene (3) was found to be less stereospecific; the extent of trans addition increased in the order Ru < Rh < Pd < Pt.

Homogeneous hydrogenation of 1 has been accomplished using platinum‐tin complexes; a 3 : 1 mixture of 3 and 2 was formed. The mechanism of this homogeneous hydrogenation is discussed on the basis of deuteration experiments.

The three 1,2,3,4,5,6‐hexamethylbicyclo[2.2.0]hex‐2‐enes and five 1,2,3,‐4,5,6‐hexamethylbicyclo[2.2.0]hexanes have been isolated. Configurations have been determined by means of NMR spectroscopy.

The thermal isomerization of 1,2 endo, 3 endo, 4, 5 endo, 6 endo‐hexamethylbicyclo[2.2.0]hexane into 1,2 exo, 3 exo, 4, 5 exo, 6 exo‐hexamethylbicyclo[2.2.0]‐hexane is described.