bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation and properties of gold(III)dithiocarbamato complexes
Authors: van Der Linden J. G. M.
Published: September 2010

The preparations of a series of compounds containing the bis(N.N‐di‐alkyl‐dithiocarbamato)gold(III)‐ion of formula [Au(R2dtc)2]+X−, with R = H, Me. Et, n‐Pr. n‐Bu and Ph, and with X− = Br−, ClO4−, PF6−, AgBr2−, AuBr2−, B(Ph)4−, Au(S2C6H3CH3)2−, and Au(S2C2(CN)2)2− are reported.

The C‐N stretching frequencies are measured in the crystalline state as well as in chloroform solutions. These data show that some negative ions have a distinct effect on the C‐N stretching frequency in the solid state, but this effect is absent in chloroform solutions. Since X‐ray studies have shown that these anions are situated near the nitrogen atom of the cation their effect on the C‐N frequencies is due to a polarisation of the C‐N bond.

Electric conductivity measurements reveal these complexes to be 1 : 1 electrolytes in nitrobenzene solutions. From the measurements in this solvent several limiting ionic conductances are determined.
The nitration of mono‐alkylbenzenes conformational analysis and steric hindrance: Part I: Primary alkylbenzenes
Authors: Baas J.M.A. , Wepster B.M.
Published: September 2010

The partial rate factors for the nitration of seven primary alkylbenzenes have been determined. The activation entropy of the ortho‐substitution in neopentylbenzene is 2.9±1.7 e.u. smaller than that of the para‐substitution. The steric hindrance of the nitration in the ortho‐positions has been discussed by reference to the conformations of the initial states and the transition states. The increase of the steric hindrance is compensated by the increase of the polarizability of the alkyl groups.
Simplified synthetic routes to symmetrical heterohelicenes
Authors: Lehman P.G. , Wynberg Hans
Published: September 2010

The synthetic route to heterohelicenes has been simplified significantly by a judicious choice of starting materials and the use of appropriate intermediates.
Solution calorimetry of some tetra‐alkylammonium bromides in formamide
Authors: de Visser C. , Somsen G.
Published: September 2010

Enthalpies of solution of tetra‐alkylammonium bromides (R4NBr, R = methyl, ethyl, n‐propyl and n‐butyl) in formamide have been determined calorimetrically at concentrations down to 10−1molal. The corresponding enthalpies of transfer from water to formamide deviate substantially from those of the alkali bromides. The unknown lattice enthalpies of Et4NBr and n‐Bu4NBr are evaluated from relationships between a, the enthalpies of solvation of Me4NBr, n‐Pr4NBr and alkali bromides in water and formamide with the cationic radii, and b, the enthalpies of hydration of Mc4NBr, n‐Pr4NBr and the alkali bromides with the partial molal volumes of these salts in water.
Hydrogen‐Deuterium exchange between methane and deuterium oxide on molecular sieve catalysts
Authors: Munter H. J.
Published: September 2010

The activity of zeolite‐based catalysts containing protons was investigated in the hydrogen‐deuterium exchange reaction of methane with deuterium oxide at temperatures above 600 °K.
The halogenation of aromatics: Part X. Vapour phase chlorination of biphenyl
Authors: de Mey Catharina A. , Kooyman E. C.
Published: September 2010

Vapour phase chlorination of biphenyl in the temperature range 350‐450° leads to monochlorides with isomer distribution 35‐38% ortho, 47‐52% meta and 14‐16% para.

This pattern is little temperature‐dependent. It is markedly different from that obtaining in liquid phase electrophilic chlorination as well as from the equilibrium distribution of monochlorobiphenyls, 53, 0, 47% and 3, 64, 33%, respectively. Thus as with other vapour phase halogenation patterns the isomer formed to the smallest extent in liquid phase electrophilic chlorination (meta) predominates.
Thermolytic reactions of esters. Part VI: A study on the steric and polar nature of the β‐elimination mechanism
Authors: Tinkelenberg A. , Kooyman E. C. , Louw R.
Published: September 2010

A general study on the β‐cis‐elimination mechanism was made, concentrating on the steric requirements of the reaction and the influence of substituents in the alkyl (especially the β‐position) and in the acid moieties. Kinetic data on cycloalkyl esters ‐ mainly substituted cyclohexyl acetates ‐ show that a planar transition state, if not essential, is highly preferred. Polar substituent effects (β‐alkyl, ‐chloro, ‐acetoxy and ‐acetyl) in the alkyl moiety, being relatively small as such, are found to be coupled with those of other structural variations, especially in the case of β‐acetyl derivatives.

Mechanistic implications are discussed in detail, leading to a transition state description comparable with that of solvolytic elimination reactions: a range of structures – in this case of a strongly concerted character – intermediate between carbonium ion‐ and carbanionlike extremes.
Aromatic sulfonation 31: (Isomer distribution in the homogeneous sulfonation of toluene with sulfur trioxide and some acidic sulfonating reagents)
Authors: van Albada M. P. , Cerfontain H. , Koeberg‐Telder A.
Published: September 2010

The isomer distribution in the sulfonation of toluene with sulfur trioxide in nitromethane at ‐ 25.0° and 25.0° has been determined aso: m: p= 13.6: 0.8: 85.4, and 12.2: 1.4: 86.4, respectively. These isomer distributions are overall data for the primary and secondary sulfonation. As indicated by flow system experiments, the degree ofortho‐substitution is greater for the primary sulfonation than for the secondary sulfonation.

The degree ofortho‐substitution for the sulfonation of toluene in nitromethane as solvent is virtually the same for the protic reagents ClSO3H, FSO3H, H2S2O7, C6H5S2O6H and CH3S2O6H,viz.6.0 ± 0.8%.
Proton‐deuteron exchange in tetra‐arylcyclobutenyl cations. Additional evidence of homocyclopropenyl cations from calculated and (13C nmr) experimental charge densities
Authors: van der Hout‐Lodder A. E. , Buck H. M. , de Haan J. W.
Published: September 2010

Ortho‐deuteration (with respect to the para‐substituent) in the phenyl ring at the saturated carbon atom enables one to assign completely the PMR spectra of tetra‐arylcyclobutenyl cations. By this method it was confirmed that the other three phenyl rings bear part of the positive charge and must be conjugated with the cyclobutenyl ring. The cyclobutenyl cations formed from 13C‐enriched acetylenes were prepared and the 13C‐shifts were correlated with the charge on the carbon atoms. The experimental charges thus obtained allowed different models for calculation by the SCF method to be tested. The calculations indicated that the one‐centre core integrals had to be adjusted as a result of a hybridization which is deshielding with respect to benzene, caused by the angle of 90° in the cyclobutenyl ring.
The infrared spectrum of linear alkynoic acids
Authors: Bus J. , Memelink A. A.
Published: September 2010

The infrared spectra of a number of linear alkynoic acids with 2‐5 triple bonds, many of them containing methylene interrupted triple bond sequences, are discussed. Compounds with an equal number of methylene groups between the carboxylic acid group and the first triple bond show great similarity in the 1180‐1350 cm−1 region. This indicates that the bands in this region are predominantly determined by this part of the chain. The conclusion is in agreement with literature data concerning alkanoic and alkenoic acids.
Structure and physical properties of aluminium alkoxides. Part IV: Vapour pressures of aluminium isopropoxide
Authors: Bleyerveld R. H. T. , Fieggen W. , Gerding H.
Published: September 2010

The vapour pressure of aluminium isopropoxide is measured statically at temperatures ranging from 80° to 126°. In the lower part of this range the compound is more volatile than is indicated by previous data. For the latent heat of vaporization a value of 11.5 ± 1.5 kcal/mole is calculated. This low value points to just small shifts in degree of association upon vaporization.
Properties of cyclodextrins. Part VII: Gaschromatographic determination of the solubility of saturated hexane and 2,3‐dimethylbutane vapours in aqueous solutions of cyclodextrin derivatives
Authors: Lammers J. N. J. J. , Koole J. L. , van Diemen A. J. G.
Published: September 2010

Specific interaction of aqueous solutions of cyclodextrin derivatives has been investigated with respect to the isomers hexane and 2,3‐dimethylbutane.

Saturated vapour of hexane or 2,3‐dimethylbutane is equilibrated with aqueous solutions of different concentrations of cyclodextrin derivatives at 1, 10, 20, 30 and 40°. The solubilities of the hydrocarbons in these solutions and in water are measured gaschromatographically. It appears that linear interaction isotherms are formed, from which the degree of occupation of the cyclodextrin voids can be calculated, assuming for the present a 1 : 1 composition of the inclusion complex.

The complex association constant has been calculated for the equilibrium: saturated vapour + cyclodextrin derivative ⇆ inclusion complex.

Plots of the natural logarithms of the association constants vs 1/T show linear relationships. The standard molar values of the free enthalpy, enthalpy and entropy pertaining to the above‐mentioned equilibrium have been calculated.
Aromatic sulfonation 32: Kinetic isotope effect of hydrogen in sulfonation and sulfonylation of benzene
Authors: van Albada M. P. , Cerfontain H.
Published: September 2010

The substrate kinetic isotope effects of hydrogen in the sulfonation and sulfonylation of benzene were determined by the competitive method, using mixtures of benzene and hexadeuterobenzene. For the sulfonation with chlorosulfuric acid, kH/kD = 1.7 ± 0.1 and 1.55 ± 0.1 for nitromethane as solvent at 25° and for dichloromethane at 0°, respectively; for the consecutive sulfonylations, kH/kD = 1.1 ± 0.1 and 1.3 ± 0.2, respectively.

For the aluminum chloride catalyzed sulfonylation with p‐toluenesulfonyl chloride at 25°, kH/kD = 1.5 ± 0.1 and 3.3 ± 0.2 for nitromethane and dichloromethane as the respective solvents.
Nucleophilic aromatic addition. Part IX: A route from 1,3,5‐trinitrobenzene to a dinitro‐tropane derivative
Authors: van Velzen J. C. , Kruk C. , Spaargaren K. , de Boer Th. J.
Published: September 2010

1,3,5‐Trinitrobenzene takes up three methylene groups from diazomethane at −80° to give 1 (Scheme 1).

Reduction of I with NaBH4 in pyridine yields the dihydro derivative II by saturation of the nitro‐olefinic double bond in I.

In a protic solvent like methanol, this reaction proceeds with rupture of the isoxazoline‐N‐oxide ring, and leads to the intermediary formation of a nitroso‐and a primary alcohol‐function. The nitroso‐group reacts spontaneously further with a nearby HCNO2‐fragment, and this transannular process generates the tropane ring‐system of III. The hydroxyl‐group at the nitrogen‐bridge is easily oxidised, to give a relatively stable nitroxide, detectable by ESR. Spectral data, including X‐ray analysis of III1 fully confirm the proposed structures.
Activation and transfer of oxygen. VI. The influence of hydrochloric acid on the autoxidation of dihydroalloxazines
Authors: Mager H. I. X. , Berends W.
Published: September 2010

Autoxidative processes in HCl may be influenced by reactions of the organic peroxy intermediates, or of H2O2, with the medium. These reactions with HCl led to the evolution of O2 and also of Cl2 under certain conditions. The question whether HCl is oxidized by an organic peroxy intermediate or by H2O2 could be answered.

Organic compounds may be chlorinated by H2O2‐HCl in high yields. The experiments strongly support the idea that aromatic chlorination is then effected by the species HOCl and/or HOOCl which are produced in situ.
The eigenvalue problem of (CH3)2S, CH3SCD3 and (CD3)2S
Authors: Ypenburg J. W.
Published: September 2010

A set of force constants for dimethyl sulfide and deuterated analogues CH3SCD3 and (CD3)2S has been calculated using a modified general valence force field. The calculated force constants reproduce the fundamental frequencies observed fairly well.
Synthesis of 4‐methylthio‐3‐butenyl isothiocyanate, the pungent principle of radish root
Authors: Brandsma L. , Vermeer P. , Kooijman J. G. A. , Boelens H. , Maessen J. Th. M.
Published: September 2010

4‐Methylthio‐3‐butenyl isothiocyanate, isolated from radish root, has been synthesized in about 50% overall yield starting from formaldehyde dimethyl dithioacetal.
Equilibration of benzene derivatives. Part IV: Isomer equilibria among 1,2‐disubstituted phenylmercuric acetates
Authors: Verwey J. , Wolters J. , Kooyman E. C.
Published: September 2010

Transmercuration involving the equilibrium process Ph‐HgOAc + ArH ⇆ ArHgOAc(o,m,p) + PhH, was previously reported to lead to unusual isomer patterns characterized by high proportions of ortho‐isomers irrespective of the nature of the substituent present in ArH1.

1,2‐Disubstituted compounds ArH were found to produce equilibrium compositions often disagreeing from those calculated on an additive basis, using the data for mono‐substituted mercurials.

Naphthylmercuric acetates appeared to constitute the first example of an equilibrium between α‐ and β‐isomers in which the α‐isomer predominates.

Interpretations are based on 1) the small steric requirements of the Hg atom, 2) its positive charge, 3) the dipolar nature of the ‐HgOAc group, 4) buttressing effects, 5) mesomeric coupling between a Hg atom and an aromatic ring.
Reactivity of aminobromoquinolines towards potassium amide in liquid ammonia
Authors: den Hertog H. J. , Buurman D. J.
Published: September 2010

The isomeric aminobromoquinolines in which amino groups and bromine atoms are attached to the pyridine nucleus were reacted with potassium amide in liquid ammonia at −33°.

2‐Amino‐3‐bromo‐ and 2‐amino‐4‐bromo‐quinoline are converted via 3,4‐didehydroquinoline into 2,3‐diaminoquinoline together with some 2,4‐diaminoquinoline. Ring transformations occur during reactions of 4‐amino‐2‐bromo‐ and 3‐amino‐2‐bromo‐quinoline yielding 4‐amino‐2‐methylquinazoline and 3‐cyanoindole, respectively. 3‐Amino‐4‐bromoquinoline yields a meta‐rearranged substitution product i.e. 2,3‐diaminoquinoline, while 4‐amino‐3‐bromoquinoline does not react under the conditions applied.

Mechanisms of the reactions described are discussed.
Organophosphorus compounds XI: Stereochemistry of grignard displacement reactions at phosphorus in isopropyl methylphosphonohalogenates
Authors: van den Berg G. R. , Platenburg D. H. J. M. , Benschop H. P.
Published: September 2010

A series of stereospecific reactions, starting from (−)‐(isoPrO)MeP(O)H (I) (see Reaction Scheme), establishes that the absolute configuration of (+)‐(isoPrO)‐MeP(O)SMe(II) (R′=Me) is (R), and not (S) as previously suggested. The reassigned configuration is confirmed by X‐ray analysis. It follows that the displacement of X by Ph in isoPrO(Me)P(O)X proceeds with complete retention of configuration when X = SMe, but proceeds with complete inversion when X = F. In the case of X = Cl, the reaction proceeds at least predominantly with inversion of configuration.
The reduction of alkylnaphthalenes with lithium in liquid ammonia
Authors: Nieuwstad Th. J. , van Bekkum H.
Published: September 2010

The reduction of naphthalene and alkylnaphthalenes with lithium in liquid ammonia has been studied. With excess of alkali metal and in the absence of a proton donor the reaction yields tetralins. The reduction of 1, 4‐dideuteronaphthalene shows that the first proton addition at an α‐position is irreversible and that the amide‐catalyzed isomerization of the initially formed 1, 4‐ into the 1, 2‐dihydronaphthalene is mainly a one step process. This isomerization is the rate‐determining step in the reduction to tetralin. Reduction of 1‐alkyl‐ and 1, 4‐dialkyl‐naphthalenes occurs mainly in the unsubstituted ring. With 2‐alkyl‐naphthalenes the selectivity of ring reduction depends on the alkyl group; in 2‐methylnaphthalene the substituted ring is about twice as reactive as the unsubstituted ring whereas the reverse is true for 2‐t‐butylnaphthalene.
Vibrational spectra and structure(s) of some X(SR)4 molecules with X  C, Si, Ge, Sn and R = methyl, ethyl, isopropyl
Authors: Ypenburg J. W. , Gerding H.
Published: September 2010

The vibrational spectra (Raman and infrared) of tetrakis (methylthio) methane, tetrakis (ethylthio) methane, tetrakis (methylthio) silane, tetrakis (methylthio) germane and tetrakis (methylthio) stannane have been recorded and analyzed with an assignment of the frequencies observed. The vibrational spectrum of tetrakis‐ (isopropylthio) methane has been obtained also.

The liquid states of tetrakis (methylthio) methane (TMC), – silane (TMSi) and ‐ germane (TMGe) contain probably two rotamers; liquid and solid tetrakis‐(methylthio) stannane (TMSn) contain probably one configuration in which internal rotation is nearly free.

Solid TMC shows a remarkable behaviour concerning the rotamers: modification 1, which is stable at temperatures below 23°, contains only the D2d configuration; modification 2, stable between 23° and 46°, contains only the S4 configuration and modification 3, stable between 46° and the melting point, consists of a mixture of both configurations.

Rotamers present in solid and liquid tetrakis (ethylthio) methane (TEC) are at least partly different. Raman spectra of solid TEC at temperatures above and below the transition point at ‐ 94° are identical within errors of measurement.

Solid TMSi and TMGe consist in all probability of one of the rotamers present in the liquid.
Pyrazoles IX. Nitration of 1‐methyl‐4‐phenylpyrazole
Authors: Cohen‐Fernandes Pauline , Habraken Clarisse L.
Published: September 2010

In contrast to nitration with nitric acid in sulfuric acid giving 4‐(o,p‐dinitrophenyl)‐l‐methylpyrazole 2, both the phenyl and the pyrazole ring are substituted on nitration with acetyl nitrate. With the latter method also a predominant ortho substitution in the phenyl ring is observed. It is concluded, that the pyrazole ring is quite susceptible to nitration at positions other than the, hitherto favoured, 4‐position.
Activity coefficients of single ions (V) in acetone and acetone‐water mixtures
Authors: Bax D. , de Ligny C. L. , Remijnse A. G.
Published: September 2010

A method for the estimation of standard chemical potential differences (Δμ°) of single ions for the transfer from one solvent to another, described previously, is further improved and applied to the transfer from water to acetone and acetone‐water mixtures.

With some reservation a value of the surface potential χ of acetone is derived.
Folded conformations. Part III: An NMR study of the conformations of aryl N‐arylsulfonylmethyl)‐N‐methylcarbamates
Authors: van Est‐Stammer Renee , Engberts Jan B. F. N.
Published: September 2010

Intramolecular shielding effects observed in the NMR spectra of the aryl N‐(arylsulfonylmethyl)‐N‐methylcarbamates 1‐7 and of phenyl N‐hydroxy‐N‐(p‐tolylsulfonylmethyl)carbamate 8 are interpreted in terms of the occurrence of folded conformations in which the aryl rings are in proximity of each other. The 2′,6′‐protons of the ester aryl group are more upfield shifted than the 3′,5′‐protons, whereas the protons of the aromatic ring attached to the sulfonyl moiety experience no significant shifts. These results indicate that the planes of the aryl rings make an angle with each other. In one case (3) the long wave‐length UV absorption was indicative for weak intramolecular CT interaction between the aromatic rings. Stereochemical information concerning the equilibrium conformation around the NCH2 bond was provided by the ESR spectra of the nitroxide 19 (derived from 8) at variable temperatures using the magnitude of the β‐H hyperfine splitting constant as a probe for conformational preferences.
Preparation and properties of Ni(IV), Pd(IV) and Pt(IV) trisdithiocarbamato complexes
Authors: Willemse J. , Cras J. A.
Published: September 2010

Oxidation of N,N‐dialkyldithiocarbamato (R2dtc) complexes of Ni(II), Pd(II) and Pt(II) with 3,5‐bis(N,N‐dialkyliminium)‐1,2,4‐trithiolane ion (R4bitt)2+ containing compounds and with M(R2dtc)X2 (M = Cu, Au; X = Cl, Br) is reported. From the oxidation of Ni(R2dtc)2 the componds Ni(R2dtc)3X (X = Cl, Br, FeCl4) were obtained. The oxidation of Pd(R2dtc)2 with R4bitt2+Cu2X2−6 (X = Cl, Br) resulted in the new compounds [Pd(R2dtc)3]2Cu2X6.

The new compound Pt(R2dtc)3CuBr2 could be obtained by the oxidation of Pt(R2dtc)2 with either (R4bitt)2+Cu2Br2−6 or Cu(R2dtc)Br2, or by the reaction of Pt(R2dtc)3Br with CuBr2. The analogous copper chloride compound was prepared from (R4bitt)2+Cu2Cl2−6 with Pt(R2dtc)2. The compound Pt(R2dtc)3AuBr2 was prepared from Pt(R2dtc)2 and Au(R2dtc)Br2. The metal‐sulfur infrared stretching frequencies are in accord with the assumption that in all these compounds the metal atoms Ni(IV), Pd(IV) and Pt(IV) have a D3 symmetry. Conductivity measurements showed the platinum complexes to be 1:1 electrolytes.
Concentration and distribution of nucleic acids in normal and atherosclerotic human aortas
Authors: Klynstra F. B. , Rothuis‐ ter Haar H. A. M.
Published: September 2010

Quantitative determinations of the nucleic acids in normal and atherosclerotic human aortic tissues were carried out. Intima (lesions removed), media (lesions removed), fatty streaks and spots, plaques and atheromas of the thoracic aorta at the various stages of atherosclerosis were separately analysed.

A marked decrease was found in the deoxynucleic acid (DNA) level in the intima and the media from stage 0 to stage I. The DNA level in the more advanced lesions was significantly lower than that in the surrounding apparently unaffected tissue.

From the observed RNA/DNA ratios it is concluded that the RNA content of the tissue‐cells gradually increases in the course of the disease.
The formation of 2‐(dimethylamino)‐3‐hydroxy‐6‐methyl‐4H‐pyran‐4‐one from chlorokojic acid and dimethylamine. The preparation of 2,3,5‐trioxohexanoic acid N,N‐dimethylamide
Authors: Dekker W. H.
Published: September 2010

The reaction of chlorokojic acid with dimethylamine yields 2‐(dimethylamino)‐3‐hydroxy‐6‐methyl‐4H‐pyran‐4‐one in addition to the expected 2‐[(dimethylamino)methyl]‐5‐hydroxy‐4H‐pyran‐4‐one. Upon oxidation the former could be converted into 2,3,5‐trioxohexanoic acid N,N‐dimethylamide.
Photopyro‐ and photoisopyro‐calciferol: Photochemical formation and thermal decomposition
Authors: Bloothoofd‐Kruisbeek A. M. , Lugtenburg J.
Published: September 2010

The thermal “Woodward‐Hoffmann forbidden” reactions of photopyro‐ and photoisopyro‐calciferol and their photochemical formation reactions have been studied.
Synthesis of 1,2‐disubstituted imidazole‐5‐carboxaldehydes and ‐4,5‐dicarboxaldehydes
Authors: Godefroi E. F. , Loozen H. J. J. , Luderer‐Platje J. Th. J.
Published: September 2010

1,2‐Disubstituted imidazoles are shown to react with refluxing 37% formaldehyde in acetic acid‐sodium acetate buffer. Both 5‐hydroxymethyl‐ and 4,5‐bishydroxymethyl‐imidazole derivatives may be formed in 25–50% yields. Bis‐hydroxymethylation is favoured by prolonged reaction times and is dependent upon the nature of the C(2) substituent. Oxidation of the mono‐ and dihydroxymethylimidazoles by means of lead tetra‐acetate in pyridine affords the imidazole‐mono‐ and ‐di‐carboxaldehydes. A few reactions of the readily accessible 1‐benzyl‐2‐isopropylimidazole‐4,5‐dicarboxaldehyde with certain ketones and hydrazine, respectively, are described.
Infrared spectra of tetragonal and monoclinic zirconia: (Short communication)
Authors: Erkelens J. , Rijnten H. Th. , Eggink‐ Du Burck S. H.
Published: September 2010

Different infrared spectra are obtained from samples of monoclinic and tetragonal zirconia. The various infrared bands are assigned to freely vibrating and to interacting surface hydroxyl groups.

By exchanging the samples with deuterium gas, acidic sites could be demonstrated on the surface.
Synthesis of guaipyridine and some related sesquiterpene alkaloids
Authors: van Der Gen A. , van Der Linde L. M. , Witteveen J. G.
Published: September 2010

Syntheses are described of guaipyridine (8) from guaiol (3) and of epiguaipyridine (2) from α‐gurjunene (10).

The alkaloid isolated from Pogostemon patchouli Pellet, possesses structure 8 of guaipyridine.

The configuration at C(10) was confirmed by proton magnetic resonance studies on the conformationally rigid tricyclic structures 14 and 15. Natural α‐gurjunene was shown to be a mixture of the C(10)‐epimers 10 and 11.
The oxidation of alkanes to stable carbonium ions by antimony pentafluoride
Authors: Lukas J. , Kramer P. A. , Kouwenhoven A. P.
Published: September 2010

Antimony pentafluoride is a unique reagent for the formation of stable carbonium ions by oxidation of saturated hydrocarbons. The kinetic parameters for the abstraction of hydride ion from ethane and neopentane have been determined. Compared to the reactions with mixed Brönsted‐Lewis acid systems (HF‐SbF5, molar ratio ⩾5/1, and FSO3H‐SbF5, molar ratio 1/1), the analogous reactions with pure SbF5 show considerably enhanced reaction rates. Moreover, neat SbF5 is capable of removing the aldehydic proton from aldehydes to yield oxocarbonium ions. It is concluded that for hydride abstraction in the so‐called “magic acid” (FSO3H‐SbF5, molar ratio 1/1) a mechanism involving protonation to alkanonium ions is not the main reaction pathway.
Chiroptical properties of (+)‐ and (−)‐2,6‐dimethyl‐1‐nitrosopiperidine in connection with the sector rule for N‐nitrosoamines
Authors: Maat L. , Beyerman H. C.
Published: September 2010

The sector rule for N‐nitrosoamines predicts a positive Cotton effect for (−)‐(R,R)‐2,6‐dimethyl‐1‐nitrosopiperidine at about 350 nm. The applicability of this rule is doubted in recent publications. We found the chiroptical properties of the title compounds in agreement with the sector rule.
Acid catalyzed hydrolysis of ethoxypropadiene
Authors: de Jonge I. , Drenth W.
Published: September 2010

The acid catalyzed hydrolysis of ethoxypropadiene has been studied in aqueous solution. The reaction is general acid catalyzed and catalytic constants for carboxylic acids conform to the Brønsted relation with an exponent α = 0.62. The average value of the solvent isotope effect k(H3⊕)/k(D3⊕) is 3.05 ± 0.11. These values are similar to corresponding values for vinyl ethers. Proton transfer from acid to substrate is rate‐determining. Zucker‐Hammett and Bunnett parameters suggest, that water is not covalently bound in the transition state of the rate‐determining step.
On the occurrence of the anrorc mechanism in aminations of substituted halogenoaza‐aromatics with potassium amide in liquid ammonia On the mechanism of the reaction of 4‐halogeno‐2,6‐diphenylpyrimidines and of 5‐bromo‐4‐chloro‐2,6‐diphenylpyrimidine with potassium amide in liquid ammonia
Authors: de Valk J. , van der Plas H. C. , de Bode J. W. A.
Published: September 2010

Evidence is presented that the amination of 4‐chloro‐2,6‐diphenylpyrimidine with potassium amide in liquid ammonia into the corresponding 4‐amino compound occurs to the extent of about 45% by the ANRORC mechanism. In the amination of the 4‐iodo‐ and 4‐fluoro derivatives of 2,6‐diphenylpyrimidine, however, the ANRORC mechanism is not operative at all. The amination of 5‐bromo‐4‐chloro‐2,6‐diphenylpyrimidine into 4‐amino‐5‐bromo‐2,6‐diphenylpyrimidine occurs to the extent of about 18% by the ANRORC mechanism. The synthesis of 5‐bromo‐4‐chloro‐2,6‐diphenyl‐[1(3)‐15N]pyrimidine and of the 4‐fluoro, 4‐chloro and 4‐iodo derivatives of 2,6‐diphenyl‐[1(3)‐15N]pyrimidine is described.
The wittig rearrangement of (diarylmethoxy)acetamides
Authors: van Der Stelt C. , Heus W.J. , Haasjes A.
Published: September 2010

N,N‐Dialkyl‐2‐(arylmethoxy)‐ or N,N‐dialkyl‐2‐(diarylmethoxy)acetamides were found to undergo a Wittig rearrangement under the influence of bases such as sodium hydride to form either N,N‐dialkyl‐3‐aryl‐ or 3,3‐diaryllactamides. When the diarylmethoxy group was asymmetric, the rearrangement resulted in diastereoisomeric reaction products. Ortho substitution in one or both aryl rings altered the course of rearrangement with the result that additionally, or even exclusively, p‐benzylmandelic amide derivatives were formed. Not only rearrangement products but also byproducts like diaryl ketone, diarylmethane and tetraarylethane were formed. The formation of the latter compound would indicate that radicals are somehow involved in the reaction mechanism. To date, attempts to obtain more than circumstantial evidence for such a mechanism have failed. In several cases byproducts with the structure of a substituted p‐benzylbenzoic acid were isolated. These acids were found to arise from the above “para rearrangement” products by further decomposition under the influence of the basic catalyst. The scope of the reaction was explored by studying the rearrangement of some thirty ethers.
Enolization and oxidation: II. Oxidation of ferrocene by molecular oxygen and hydrogen peroxide in acidic media
Authors: Lubach J. , Drenth W.
Published: September 2010

Ferrocene can be oxidized by molecular oxygen in acidic aqueous ethanol. The rate is first order in oxygen and second order in ferrocene and in acid. Probably, hydrogen peroxide is an intermediate. This hydrogen peroxide is able to oxidize ferrocene and ferricenium ions, but the rates of these reactions are relatively slow. Hydrogen peroxide is removed mainly by reaction with the solvent ethanol. The latter reaction is catalyzed by small amounts of iron ions which originate from decomposition of ferrocene. The presence of this catalytic effect of iron ions in the reaction between hydrogen peroxide and solvent was shown in separate experiments.
A NMR study of N,N,N′,N′‐tetraethylthiuram disulfide and its complexes with ZnI2, CdI2 and HgI2
Authors: Grotens A. M. , Pijpers F. W.
Published: September 2010

The thermodynamic constants of the hindered rotation around the S2CNR2 bond of N,N,N′,N′‐tetraethylthiuram disulfide and its complexes with Zn, Cd and Hg(II) halides have been obtained by NMR.

It is shown that the effect of the solvent on the rotation rate is small.

At low temperatures the NMR patterns reveal the existence of a second process that interchanges inequivalent ethyl groups. This process is due to the nonequivalence of the ligand sulfur atoms as can be seen from the crystallographic structure of HgI2 (Me4tds). The thermodynamic constants of the interconversion between these two inequivalent configurations are also presented.
Synthesis of substituted 6H‐1,3‐thiazines
Authors: Hoff S. , Blok A. P.
Published: September 2010

Substituted 4,5‐dihydro‐4‐hydroxy‐6H‐1,3‐thiazines II can be prepared in high yields from the BF3 etherate‐catalysed reaction between α,β‐unsaturated aldehydes, ketones and ketols on the one hand and thioamides, thioureas and dithiocarbamates on the other.

In some instances these dihydrohydroxythiazines can be converted into the corresponding 6H‐1,3‐thiazines III with POCl3 in pyridine or with acid in aprotic solvents. The conditions of this elimination reaction are discussed.
Conformational preference of cis‐1‐aryl‐2‐(2‐benzo[C]phenanthryl)‐and cis‐1‐aryl‐2‐(3‐phenanthryl)‐ethenes
Authors: de Jong M. H. , Laarhoven W. H.
Published: September 2010

NMR measurements under different conditions (temperature, solvents used, presence of a shift‐reagent) of cis‐ and trans‐1‐aryl‐2‐(2‐benzo[c]phenanthryl)‐ethenes reveal that an overcrowded conformation predominates in cis isomers. In the analogous 1‐aryl‐2‐(3‐phenanthryl)ethenes no clear conformational preference is found.
Derivatives of NPCl2(NSOCl)2 and (NPCl2)2NSOCl. Part I: The preparation of a monophenyl and a difluoro derivative of cis‐NPCl2(NSOCl)2
Authors: Baalmann H. H. , van De Grampel J. C.
Published: September 2010

Reaction of NPCl2(NSOCl)2* and Ph2Hg in tetrachloroethane at room temperature yields the monophenyl derivative NPCl2NSOClNSOPh. Treatment of NPCl2(NSOCl)2 with AgF2 in carbon tetrachloride leads to the formation of NPCl2(NSOF)2. From IR spectra it was determined that the phenyl and fluorine substituents are bonded to sulfur ring atoms.

The IR and mass spectra of the two new compounds are discussed.
Preparation of some derivatives of meta‐di‐tert‐butylbenzene and tert‐butylbenzene
Authors: de Koning A.J.
Published: September 2010

The preparation of a number of mono‐brominated derivatives of meta‐di‐tert‐butylbenzene and tert‐butylbenzene from 3,5‐di‐tert‐butylacetanilide is described.
Alcohols as ligands: Part IV. Complexes of ethylene glycol with some metal(II) sulfates and nitrates
Authors: Knetsch D. , Groeneveld W.L.
Published: September 2010

A number of complexes are reported of some metal(II) nitrates and sulfates containing ethylene glycol as the ligand. The general formula is M(EG)xAn, where M = Mn, Co, Ni, Cu, Zn, Mg, Ca and Cd; A = NOand SO; x = 1 ‐ 4; n = 1 ‐ 2.

The compounds were characterized by means of physical measurements and chemical analyses.

Ligand field parameters were calculated for the Co, Ni and Cu compounds, and the ligand is placed in the spectrochemical series.

The infrared spectra indicate coordination of NOand SO. A considerable amount of hydrogen‐bonding is present in the complexes.

In most of the compounds, the coordination of ethylene glycol is probably monodentate.
Conformational analysis of some (hydroxy)alkyl groups on benzene: Part II: The barriers to rotation of the hydroxyalkyl groups in 1,3,5‐tri(1‐hydroxy‐2,2‐dimethylpropyl)benzene and 1,3,5‐tri(1‐hydroxy‐1,2,2‐trimethylpropyl)benzene
Authors: Baas J.M.A. , Sinnema A.
Published: September 2010

The 100 MHz PMR spectra of the diastereoisomers of 1,3,5‐tri(1‐hydroxy‐2,2‐dimethylpropyl)benzene (2) and 1,3,5‐tri(1‐hydroxy‐1,2,2‐trimethylpropyl)‐benzene (1) are discussed. The high barrier to rotation reported in the literature for the hydroxyalkyl groups of 1 is probably in error. A value of 9.5 kcal/mole at −77° has been determined for 1‐(1‐hydroxy‐1,2,2‐trimethylpropyl)‐3,4,5‐trimethoxybenzene (3) and the low temperature spectra of 1 indicate a value in the same range. The barrier to rotation for the hydroxyalkyl groups in 2 or in the 3,4,5‐trimethoxybenzene derivative (4) could not be determined.
Reactivity of derivatives of 3‐bromo‐l, 5‐naphthyridine and 3‐bromoquinoline towards potassium amide in liquid ammonia
Authors: Pomorski J. , den Hertog H. J. , Buurman D. J. , Bakker N. H.
Published: September 2010

Reactions of some 2‐substituted derivatives of 3‐bromo‐l, 5‐naphthyridine and 3‐bromoquinoline with potassium amide in liquid ammonia were investigated. The course of these aminations is compared with that of corresponding processes studied previously.
Vilsmeier formylation of vinylcyclopropanes: 1. Formylation of thujopsene
Authors: Traas P. C. , Boelens H.
Published: September 2010

Thujopsene(1) can be formylated in the 3‐position in 80% yield by use of one equivalent of the Vilsmeier reagent. The resulting 3‐formylthujopsene(4) is useful for the synthesis of other 3‐substituted derivatives (CH2OH, COOH, COCH3). With an excess of the reagent higher formylation products are formed. Two such products have been isolated and characterized and a mechanism for their formation is put forward.
A spectroscopic study of zinc(II), cadmium(II) and mercury(II) complexes with tricyclohexylphosphine as ligand
Authors: Moers F. G. , Langhout J. P.
Published: September 2010

The preparations of the complexes M(PCy3)2X2 and M(PCy3)X2 with M = Zn, Cd or Hg, X = Cl, Br, I or SCN, PCy3 = tricyclohexylphosphine and some of their adducts with acetone, methanol or carbon disulfide are reported. Their infrared spectra in the range 4000‐200 cm−1 and their Raman spectra between 4000‐100 cm−1 have been investigated. From these data we conclude for the dimeric complexes M(PCy3)X2 with M = Cd or Hg and X = Cl, Br or I, a distorted tetrahedral coordination around mercury or cadmium. For the complex Hg(PCy3)(SCN)2 we suggest a trigonal coordination around mercury. Assignments are proposed for the metal‐halogen and metal‐phosphorus frequencies.
Thermal rearrangement of 2‐alkynyl alkanedithioates
Authors: Meijer J. , Vermeer P. , Bos H. J. T. , Brandsma L.
Published: September 2010

2‐Alkynyl alkanedithioates R1R2CHC(S)‐S‐CH(R3)CCR4 (R1‐R4=H or alkyl) rearrange at 130‐140° in the presence of catalytic amounts of C2H5N(i‐C3H7)2 to 1,3‐dithiole derivatives (5) possibly via allenyl alkanedithioates R1R2CHC(S)SC(R4)CCHR3 although these intermediates have not been isolated. Traces of acids can cause dimerisation of the 1,3‐dithioles.
The crystal and molecular structure of the p‐iodobenzoate of 23‐demethylgorgosterol
Authors: Hsu I‐Nan , van der Helm Dick
Published: September 2010

The crystal and molecular structure of a cyclopropane containing marine steroid, 23‐demethylgorgosterol, and its absolute configuration have been determined on the p‐iodobenzoate derivative. The compound crystallizes in the space group P21212,1 with cell dimensions a = 14.076, b = 39.15 and c = 5.987 Å. There are four formula units (C36 H51 O2 I) per unit cell. The structure was determined and refined using 1872 counter data. The final R‐value is 7.4%. The structure determination confirms the presence of a cyclopropane ring in the side chain. An explanation is given for the two additonal highfield protons observed in the NMR spectrum.
Photodecomposition of some carboxylic acids and the properties of the radicals formed
Authors: van Beek H. C. A. , Heertjes P. M. , Schaafsma K.
Published: September 2010

Irradiation of dl‐mandelic, phenylacetic, formic, malonic or dl‐tartaric acid in aqueous or ethanolic solutions with U. V. light results in the photodecomposition of these acids into ·COOH and the respective residual radicals. The ·COOH radical has strong reducing properties and can reduce azo dyes, if they are added to the solution prior to irradiation, to amines. The residual radicals formed together with ·COOH upon photodecomposition of the carboxylic acids, can cause fading of the dyes either by reduction or by addition to the chromophoric system.
Synthesis of two new corticotrophic peptides containing homoarginine in position 8
Authors: Tesser G. I. , Pleumekers A. W. J. , Bassie W. , Balvert‐Geers I. C.
Published: September 2010

The octadecapeptide amide I and the tetracosapeptide II containing homoarginine in position 8 have been synthesized according to a generally approved scheme. As a new feature, the hydroxyl functions of the serine and tyrosine residues were protected in the synthesis of the N‐terminal decapeptide. The latter, presumably by its higher solubility in organic solvents, afforded the protected end products in an improved yield. For complete deprotection, however, acid‐treatment of these compounds had to be extended over longer periods than in the absence of the ether functions.
“Investigation of the angular dependency of Co‐O‐Co superexchange by means of magnetic susceptibility measurements in dilute systems”
Authors: van Leeuwen G. C. M.
Published: September 2010

Magnetic susceptibility measurements in the temperature range of 4 to 150°K have been performed on samples of CoxMg1‐x O, x ranging from 2.5% to 5% and on LiMg1‐xCoxPo4, x ranging from 1.5% to 5%. Deviations from the single ion susceptibility have been observed for all samples and explained by taking into account an effective exchange interaction 2JsTi. STj between ions within various types of isolated clusters, s being the fictitious spin of the doublet ground state.

From the experimental data on CoxMg1‐xO for J(90°)/k and J(180°)/k the values 5.0 °± 0.3°K and 135 ± 10°K have been derived, while in LiMg1‐xCoxPO4 J(132°)/k has been found equal to 12 ± 4°K.
The conjugate addition of methyl Grignard reagents to 5α‐1‐estren‐3‐ones
Authors: Bolt C. C. , Zeelen F. J.
Published: September 2010

The conjugate addition of methyl Grignard reagents to 5α‐1‐estren‐3‐ones leads to 1α‐methyl derivatives. It is suspected that this is due to formation of a half chair conformation of ring A upon 1α attack, whereas 1β‐attack would yield a product having a half boat conformation of ring A.
Synthesis and thermal decomposition of tertiary β‐nitroalkyl peroxynitrates
Authors: Duynstee E. F. J. , Hennekens J. L. J. P. , Housmans J. G. H. M. , van Raayen W. , Voskuil W.
Published: September 2010

Three tertiary β‐nitroalkyl peroxynitrates 2a, 2b and 2c were prepared by reaction of N2O4 and excess O2 with isobutene (la), 2,3,3‐trimethyl‐2‐butene (1b) and 2,3‐dimethyl‐2‐butene (1c), respectively. These compounds are rather unstable and at 23° slow decomposition occurs. It seems likely that this decomposition starts by O‐O bond fission yielding an NO3 radical and a β‐nitroalkoxy radical. In the case of 2a this alkoxy radical either reacts with NO2 or dimerises but no β‐fission is observed. In the case of 2b and 2c extensive β‐fission of the alkoxy radical produces alkyl radicals which react with NO3 radical forming alkyl nitrate or react with O2 and NO2 (produced from NO3) forming alkyl peroxynitrate.
Chemistry of cyclopropene IV. The formation of cycloprop‐1‐enylcarbinols
Authors: Schipperijn A. J. , Smael P.
Published: September 2010

A relatively simple method has been developed for the preparation of (cycloprop‐1‐enyl)methylcarbinols from 1‐sodiocyclopropene and epoxides. Satisfactory yields are obtained only with epoxides having at least one unsubstituted epoxy carbon atom.

In addition, a method is given for the synthesis of cycloprop‐1‐enylcarbinols from 1‐sodiocyclopropene and ketones. Its applicability is limited by the tendency of the products to polymerize and is restricted to those ketones which have at least one alkyl substituent at each of the carbon atoms adjacent to the carbonyl group. Aldehydes fail to give the corresponding carbinols.
Some aspects of the solution photochemistry of 1,3‐cyclohexadiene, (Z)‐ and (E)‐1,3,5‐hexatriene
Authors: Minnaard N. G. , Havinga E.
Published: September 2010

UV irradiation (λ = 265 nm) of 1,3‐cyclohexadiene yields (Z)‐1,3,5‐hexatriene with good efficiency (Φ = 0.41). UV irradiation also effects equilibration between (Z)‐ and (E)‐isomers, be it with rather low quantum yields (ΦZ→E = 0.034; ΦZ→E =0.016). The Z ⇄ E isomerization can be sensitized by triplet sensitizers, e.g. biacetyl. This reaction occurred also upon irradiation of solutions in bromoform with light of 436 nm (So → T absorption).

A simple formula for the calculation of quantum yields from composition data is given.
Chemistry of acetylenic ethers 102: Reaction of di(1‐alkynyl) sulfides with sodium sulfide, selenide and telluride. Formation of 1,4‐dithiins, 1,4‐thiaselenins and 1,4‐thiatellurins
Authors: Meijer J. , Vermeer P. , Verkruijsse H. D. , Brandsma L.
Published: September 2010

Interaction between di(1‐alkynyl) sulfides (1) and sodium sulfide, selenide or telluride in mixtures of liquid ammonia and methanol or dimethylformamide and methanol gives 1,4‐dithiins (2), 1,4‐thiaselenins (3) and 1,4‐thiatellurins (4).
Benzoheterocyclic synthesis via benzoannelation of heterocyclic ortho‐dicarboxaldehydes: Benzimidazoles from an imidazole‐4,5‐dicarboxaldehyde; a benzo[b]furan from a furan‐2,3‐dicarboxaldehyde
Authors: Corvers A. , de Groot Ae. , Godefroi E. F.
Published: September 2010

The base‐catalyzed condensation of an imidazole‐4,5‐dicarboxaldehyde, 1, with sulfides (ZCH2)2S (Z = an electronegative group) is shown to constitute a general route to 5,6‐disubstituted benzimidazoles. In one case, a sulfoxide, (CH3OOCCH2)2SO, behaves similarly. Sulfones (ZCH2)2SO2 bring about the transformation of 1 into imidazo[4,5‐d]thiepin‐6,6‐dioxides; these are stable compounds, losing SO2 only at elevated temperatures with formation of benzimidazoles. The general applicability of this benzoannelation route is further illustrated by the conversion of furan‐2,3‐dialdehyde, 9, to benzo[b]furan, 10.
Mass spectrometry of products obtained by reduction of 6‐nitroquinaldine and 2‐nitrophenanthrene with phosphine
Authors: Leclercq P. A. , Bellaart A. C. , van de Ven L. J. M.
Published: September 2010

Reduction of 6‐nitroquinaldine and of 2‐nitrophenanthrene was carried out with phosphine under conditions described by Buckler

S. A. Buckler, L. Doll, F. K. Lind and M. Epstein, J. Org. Chem. 27, 794 (1962).

. Reduction of 6‐nitroquinaldine yielded 3,9‐dimethyldipyrido[3,2‐a: 3′,2′‐h]phenazine, pyridazino‐[4,3‐f: 5,6‐f′]biquinaldine‐3‐oxide and 6,6′‐azoquinaldine, while 2‐nitrophenanthrene afforded only 2,2′‐azoxyphenanthrene. Reduction of pyridazino[4,3‐f: 5,6‐f′]biquinaldine‐3‐oxide with zinc dust and sodium hydroxide yielded 6,6′‐diamino‐5,5′‐biquinaldyl, which was converted into 6,6′‐di(acetylamino)‐5,5′‐biquinaldyl. The structures were verified by spectrometry. Mass spectra of the new compounds are discussed.
Thermal and photoinduced deboronations of some pyridine‐ and benzeneboronate anions
Authors: Fischer F.C. , Havinga E.
Published: September 2010

Dissociation constants of 3‐ and 4‐pyridineboronic acid and σ‐values for the meta‐ and para‐B(OH)2 and ‐B(OH)3− groups have been determined; in aqueous solutions the compounds occur predominantly in the pyridiniumboronate form. 2‐Pyridineboronate seems to be thermally unstable, whereas 3‐ and 4‐pyridineboronic acids are thermally stable but decompose upon treatment with methyl iodide.

Irradiation in neutral or slightly basic solution of 3‐ and 4‐pyridineboronic acids effects splitting into borate and pyridine (in its turn photochemically converted into “photopyridine”).

We suggest that these thermal and photoreactions may be considered as SE l‐protodeboronations of the pyridinium boronate form. Experimental reactivities could be roughly correlated with results of P.P.P. calculations of the change of electrostatic energy between initial and transition state.
Halogen migration and amination in reactions of halogeno derivatives of five‐membered hetarenes with potassium amide in liquid ammonia
Authors: van der Plas H. C. , de Bie D. A. , Geurtsen G. , Reinecke M. G. , Adickes H. Wayne
Published: September 2010

On treatment of 2‐bromothiophene, 2,3‐, 2,4‐, and 2,5‐dibromothiophene with potassium amide in liquid ammonia at − 75°, a bromine migration of position α to position β of the thiophene ring takes place. On treatment of the above mentioned compounds with potassium amide in liquid ammonia at − 33°, besides α to β bromine rearrangement, amination to 3‐aminothiophene was observed.

The mechanism of the transbromination is assumed to be an intermolecular process, involving dibromo‐ and tribromo‐thiophenes. The formation of 3‐aminothiophene does not occur via a didehydro intermediate, but it is the result of amination of a polybromothiophene, yielding an amino‐bromothiophene, which is debrominated by reaction with amide ion or a thiophene anion.
Stereochemical aspects in mass spectrometry: Comparison of the mass spectra of some (E)‐ and (Z)‐ionone and ‐ionol derivatives
Authors: van Wageningen A. , Cerfontain H. , Nibbering N. M. M.
Published: September 2010

The mass spectra of the (E)‐ionones and (E)‐ionols are markedly different from those of the corresponding (Z)‐isomers. The differences are explained ‐ using the concept of charge localization in terms of the difference in ability of the molecular ions of a given pair of geometrical isomers to undergo intramolecular ring closure and intramolecular hydrogen transfer reactions. The mass spectral difference of a given pair of geometrical isomers can be used for the configurational assignment of the two isomers.
Étude conductimétrique de la réaction de NOCl sur SO3 dans SO2 liquide à −20°C
Authors: de Jaeger R. , Heubel J.
Published: September 2010

From a conductimetric study of the effect of NOCl on SO3 in SO2 at − 20°C the compounds NO(SO3)nCl in which n = 1,2,3 have been isolated and the probability of the presence of much more condensed terms (n = 4,5,6) indicated.

The solubility of NOSO3Cl and NOS2O6Cl in SO2 at −20°C has been determined and it has been demonstrated, by the variations of the equivalent conductivity in terms of 1/√c, that the behaviour of NOSO3Cl in SO2 resembles that of a weak electrolyte.