bluuebunny/crossref_metadata_2025_split huggingface dataset:
The mannich condensation of sulfinic acid with aldehydes and carboxamides, sulfonamides, or lactams. Part IV
Authors: Olijnsma T. , Engberts J. B. F. N. , Strating J. 
Published: September 2010

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

AbstractA closed form lineshape formula is given for the characteristic ‘full field’ rigid matrix ESR signal of molecules existing in an electronic triplet state. The formula enabled a computer analysis to be made of the complex rigid matrix spectra produced by the alkali‐metal reduction products of some β‐diketones. It was concluded that the spectra consisted of the resonance signals of a monoradical and two dimerization products with triplet character.The experimental data provided information on the structures of the two dimers and on the mechanism leading to their formation.
The determination of the standard potential of the silver‐silver bromide and the silver‐silver iodide electrode in a 87.68 wt% methanol‐water mixture and in 100% methanol
Authors: Alfenaar M. , de Ligny C. L. , Remijnse A. G. 
Published: September 2010

AbstractThe standard potential of the silver‐silver bromide and the silver‐silver iodide electrode in a 87.68 wt% methanol‐water mixture and in 100% methanol has been determined by comparison with the known standard potential of the silver‐silver chloride electrode in these solvents.The potential of the silver‐silver bromide and the silver‐silver iodide electrodes appeared to be very sensitive to light.
Chemistry of sulfines. Part III: Further investigations on the preparation
Authors: Zwanenburg B. , Thijs L. , Strating J. 
Published: September 2010

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

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

AbstractComposite hydrolytic dissociation constants, KI and KII, of 4‐aminobenzoic acids substituted as follows, 2‐H‐, 2‐CH3‐, 2‐Cl‐, 2‐Br‐, 2‐NO2‐, 2‐OH‐, 2‐OCH3‐, 3‐Br‐, 2,6‐(CH3)2‐, 2,6‐(C2H5)2‐, 2,6‐Cl2‐ and 2,6‐Br2‐, have been determined in aqueous solution, at 50°C and at an ionic strength of 0.1.From the values of pKI and pKII and the postulate that the inductive effect of the 4‐NH3+ group on the dissociation of the 1‐COOH group is the same for all the acids studied, namely 0.54, all four individual pK values have been calculated for each acid as well as the fraction of zwitterion. After comparison of the individual pK values with the correspondingly substituted benzoic acids and anilinium ions, several conclusions could be drawn with respect to the configurational and energetic relationships between the acids.
Decarboxylation of substituted 4‐aminobenzoic acids in acidic aqueous solution
Authors: Los J. M. , Rekker R. F. , Tonsbeek C. H. T. 
Published: September 2010

AbstractRates of decarboxylation have been determined of the following substituted 4‐aminobenzoic acids 2‐H‐, 2‐CH3‐, 2‐Cl‐, 2‐Br‐, 2‐NO2‐, 2‐OH‐, 2‐OCH3‐, 3‐Br‐, 2,6‐(CH3)2‐, 2,6‐(C2H5)2‐, 2,6‐Cl2‐ and 2,6‐Br2‐ in aqueous hydrochloric acid solution (pH ranging from about 0 to about 2), at 50° and an ionic strength of 0.1 (except for the lowest pH values).Analysis of the data in terms of a second‐order mechanism involves predominantly the species neutral ampholyte (notzwitterion) and hydronium ion for the range 0 < pH < 2. A general rate expression has been derived with the following features: (a) both (neutral) ampholyte and anion decarboxylation and (b) hydronium‐ion inhibition at lower pH. Essential to the mechanism is that the σ‐complex formed by addition of a proton at the C(1)position of the neutral acid cannot decarboxylate unless it first ionizes into the corresponding anion (loss of the carboxyl proton). The formation of the σ‐complex is not necessarily rate determining.The reaction mechanism can explain not only all relevant facts concerning the acids investigated but also the data offered by the literature on substituted benzoic acids, in particular all available data on the13C‐carboxyl‐isotope effect and the (H2O, D2O)‐solvent‐isotope effect.
Chemistry of sulfines. Part IV: Reaction with halogens, tetrachloro‐ortho‐quinone, triphenylphosphine and water
Authors: Strating J. , Thijs L. , Zwanenburg B. 
Published: September 2010

AbstractThe addition of chlorine and bromine to 2‐methoxynaphthalene‐1‐thial‐S‐oxide (II) yields the dichloride and dibromide (IVa and b). The dichloride gives upon treatment with triethylamine 2‐methoxythionaphthoyl chloride‐S‐oxide (V). Similarly, thiobenzaldehyde‐S‐oxide (prepared in situ) was converted into cis‐ and trans‐thiobenzoyl chloride‐S‐oxide (scheme B).Tetrachloro‐ortho‐quinone reacted with xanthione‐S‐oxide (IX) and thiofluorenone‐S‐oxide (I) yielding 1:1 adducts (X and XI) in which the α‐dioxo part of the quinone had acted as diene.The reduction of the sulfine I with triphenylphosphine gave initially the thioketone, which reacted further with the phosphine as outlined in scheme D. The same reaction was carried out with the thial‐S‐oxide II.The acid catalyzed hydrolysis of thioketone‐S‐oxides gave rise to the formation of the corresponding ketones (scheme E).
Hetarynes. Part XV: N‐oxides of 2,3‐ and 3,4‐pyridyne
Authors: Martens R. J. , den Hertog H. J. 
Published: September 2010

AbstractThe action of potassium amide in liquid ammonia on the N‐oxides of 2‐, 3‐ and 4‐bromopyridine, 3‐fluoropyridine, 2‐ and 3‐bromo‐4‐methylpyridine, 3‐ and 4‐bromo‐5‐ethoxypyridine and 3‐ and 4‐bromo‐2,5‐dimethylpyridine has been investigated.3‐Fluoropyridine‐N‐oxide does not react under the conditions applied; the other N‐oxides yield mixtures containing one or two amino compounds. The mechanisms of the formation of these substances are discussed.It was established that the SNAr2 (= AE) reaction is almost the sole reaction pattern in the aminations of the 4‐bromopyridine‐N‐oxides and one of the mechanisms occurring in the aminations of the 2‐bromopyridine‐N‐oxides.The 2‐bromopyridine‐N‐oxides react partially and the 3‐bromopyridine‐N‐oxides exclusively via 2,3‐pyridyne‐N‐oxides as intermediates, except the N‐oxides of 3‐bromo‐2,5‐dimethylpyridine and 3‐bromo‐5‐ethoxypyridine in the aminations of which 3,4‐pyridyne‐N‐oxides play a role.
Chemistry and spectroscopy in strongly acidic solutions. Part IV: NMR Spectroscopic observation and structure of protonated aldehydes. Kinetics of deprotonation
Authors: Hogeveen H. 
Published: September 2010

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

AbstractInorganic complexes of two cyclic sulfoxides viz. tetramethylene sulfoxide and pentamethylene sulfoxide are reported. The hexasulfoxide metal complexes are identified by their analyses, melting points, X‐ray powder patterns and infrared spectra. The shifts in the S = O stretching frequencies in the complexes can be qualitatively related to the electron negativities of the metal ions. The infrared spectra of the complexes of Cu(II) show two separated S = O stretching frequencies in the solid state. The Cu(II) complexes are isomorphous with hexasulfoxide complexes of other metal ions, which have only one S = O frequency. The splitting of the band in the Cu(II) complexes is probably caused by tetragonal distortion.
Chemistry and spectroscopy in strongly acidic solutions. Part IX: Configurational preference in protonated carboxylic acids. Kinetics of reversible alkyl oxocarbonium ion formation
Authors: Hogeveen H. 
Published: September 2010

AbstractProtonation of aliphatic carboxylic acids RCOOH in HF‐BF3 solution at low temperature leads to dihydroxycarbonium ions. The configurations as regards the groups R and H at the partly double magnified image bonds depend on the steric requirements of group R: In the case of RCH3, CH2Cl, CH3CH2 and (CH3)2CH both a cis‐ and a trans‐configuration, and in the case of R(CH3)3C two trans‐configurations probably exist.The rate constants of the dehydration of the protonated acids to acyl cations that takes place at higher temperatures proved to vary only slightly for RCH3, CH3CH2, (CH3)2CH and (CH3)3C. In agreement with previous work on protonated formic acid the rates were found to be much lower in HF‐BF3 than in sulfuric acid solution (as estimated from Deno's results), possibly due to a difference in molecularity of the reaction.
Chemistry and spectroscopy in strongly acidic solutions. Part X: Formation, structure and decomposition of hydroxy‐alkoxy‐carbonium ions
Authors: Hogeveen H. 
Published: September 2010

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

AbstractThe degree of ortho‐substitution in the sulfonation of toluene, ethylbenzene and isopropylbenzene with sulfuric acid varying in concentration from 80.6 to 98.5% H2SO4 at 25° was determined. For a given sulfuric acid concentration the ratio of ortho‐ to (para‐ + meta‐) substitution decreases with increasing size of the alkyl group, whereas for a given alkyl group this ratio decreases with decreasing sulfuric acid concentration.Partial rate factors for the homogeneous sulfonation of toluene, ethylbenzene, isopropylbenzene and t‐butylbenzene in 86.3% sulfuric acid at 25° were calculated. The partial rate factors for ortho‐substitution decrease with increasing size of the alkyl group, while those for para‐substitution follow the Baker‐Nathan order.Introduction of a sulfonic acid group ortho to the alkyl group of an alkylbenzene can be effected with weak oleum (∼ 16%) as reagent under conditions of disulfonation with toluene, ethylbenzene and isopropylbenzene, but not with t‐butylbenzene.
Anticoagulants. Part I: Synthesis of 2,3‐disubstituted 1,4‐naphthoquinones and 4‐hydroxycoumarins
Authors: Kralt T. , Bots J. P. L. , Moed H. D. , Ariens E. J. 
Published: September 2010

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

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

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

AbstractInfrared spectra are reported of methyl cyanide coordinated to the monovalent cations, Li, Na, K, Rb, Cu, Ag, Au, Tl and the divalent cations, Be, Mg, Ca, Sr, Ba, Mn, Fe, Co, Ni, Cu, Zn, Cd, Pd, in complexes of the types M (CH3CN)pn+ (SbCl6)n‐ and M (CH3CN)pn+ (SnCl6)n/22−.The shifts in the different bands are discussed. Metal ions are placed in a series of electronegativity towards methyl cyanide. The sequence is compared with ionization energies of the metals, and with other measures of metal electronegativity.
Sulfur compounds in free radical reactions. Part II: Thermal decomposition of arenediazothiolates
Authors: van Zwet H. , Kooyman E. C. 
Published: September 2010

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

AbstractNOSO3Cl forms monoclinic crystals with space group P21/c. The unit cell with dimensions a = 8.997 Å, b = 7.101 Å and c = 7.557 Å, β = 109.80°, contains four molecules, all atoms are in general fourfold positions. The structure was solved by vector analysis and fourier synthesis, followed by a least squares refinement using photometered CuKα reflections. Discrete NO+ and SO3Cl− ions are present. The SO3Cl− ion has C3v symmetry. The S‐Cl distance is 2.05 Å, the S‐O distance 1.43 Å. The very short N‐O distance found (0.94 Å), is explained by estimating a correction (0.09 Å) to the mean separation of the atoms from their thermal motions.
Pyrazoles. Part IV Effects of solvents and steric effects on UV and PMR spectra of 4‐phenylpyrazoles
Authors: Cohen‐Fernandes Pauline , Habraken Clarisse L. 
Published: September 2010

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

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

AbstractProtonation of propionitrile‐15N leads to formation of the imino‐15N ethylcarbonium ion, which according to its NMR spectrum occurs in one configuration only. Chemical shifts and coupling constants have been determined at some temperatures.Line‐broadening measurements of the low‐field 15N‐H doublet show that the deprotonation of the imino‐15N ethylcarbonium ion by fluoride anions in hydrogen fluoride‐boron trifluoride solution is diffusion‐controlled.
The chemistry of small ring compounds. Part XI Oxidation of 1‐methoxycyclopropanol and 1‐methoxy‐2,2‐dimethylcyclopropanol by metal ions
Authors: Schaafsma S. E. , Molenaar E. J. F. , Steinberg H. , de Boer Th. J. 
Published: September 2010

AbstractOn oxidation of 1‐methoxycyclopropanol 1 by ammoniacal cupric sulfate, methyl acrylate 4a and dimethyl adipate 3a are formed exclusively in high yield. It is shown that the latter compound is formed from the intermediate radical 2 by dimerisation and predominantly by addition to methyl acrylate. The same products and a tricarboxylic ester 8 are formed using ferric nitrate as the oxidant.1‐Methoxy‐2,2‐dimethylcyclopropanol 10 reacts with ammoniacal cupric sulfate to form the tetramethyladipic esters 13 and 14 as the main products and the α,β‐ and β,γ‐unsaturated esters 16 and 17 in smaller quantities. These compounds originate from the radicals 11 and 12.If the oxidation is carried out with ferric nitrate only radical 12 is produced, which is oxidised further yielding the unsaturated esters 16 and 17 and the β‐hydroxy‐ester 18. The diversity of products obtained from the hemiacetal 10 and ammoniacal cupric sulfate, as compared with the ferric nitrate system, is ascribed to transient copper complexes which affect the transition state of the oxidation.With ferric chloride the hemiacetals 1 and 10 give the β‐chloro compounds 9 and 19 through an efficient ligand transfer oxidation of the intermediate radicals 2 and 12.
The Reaction of 4,4‐dimethyl‐1‐phenylisochroman with hydriodic acid and phosphorus
Authors: van der Stelt C. , Hofman P. S. , van der Vlies C. , Bickelhaupt F. 
Published: September 2010

AbstractIn continuation of earlier work, the reaction of 4,4‐dimethyl‐1‐phenylisochroman (1) with hydriodic acid and phosphorus was subjected to a closer investigation. 10, 11‐Dihydro‐10, 10‐dimethyl‐5H‐dibenzo[a,d]cycloheptene (2) and 9, 10‐dihydro‐9‐isopropylanthracene (4) were identified as the reaction products in a ratio 2:1. Fractionation of the reaction mixture afforded, among other products, anthracene as a pyrolysis product of compound 4. A plausible reaction mechanism for the formation of 2 and 4 is proposed.
A study of the effect of labelling on the solubility of thallous bromide in water: On the feasibility of the radiometric determination of solubility
Authors: Gelsema W. J. , de Ligny C. L. , Blijleven S. H. A. 
Published: September 2010

AbstractThe solubilities of thallous bromide, both inactive and labelled with 204T1, in water at 25°, have been determined titrimetrically and proved to be identical within experimental error.The specific count rates of labelled thallous bromide, both in saturated and unsaturated solution, have been determined and proved to be identical within experimental error.These results lend strong support to the validity of the radiometric method for the determination of solubility, which was challenged recently by Spitsyn et al.The solubility of thallous bromide in water at 25.0° is 576.7 ± 0.3 mg/l.
Inorganic complexes with acetic acid as the ligand
Authors: van Leeuwen P. W. N. M. , Groeneveld W. L. 
Published: September 2010

AbstractCoordination complexes containing hexa‐acetic acid metal groups are reported with the divalent cations Mg, Mn, Co, Ni, Cu and Zn and with the tetrafluoroborate, perchlorate and nitrate anions. Visible spectra, some infrared data and isomorphism according to X‐ray powder diagrams are recorded. The compounds are prepared from the hydrated salts and acetic anhydride. The spectrochemical position of acetic acid is given and compared with related molecules such as acetamide and urea. The preparation of complexes of the last two ligands is briefly reported.
PMR spectroscopic investigation of structures, stabilities, and rearrangement reactions of C4‐C7tertiary carbonium ions in HF‐SbF5
Authors: Brouwer D. M. 
Published: September 2010

AbstractSolutions in HF‐SbF5 of the tertiary butyl, pentyl, hexyl, methylcyclopentyl and heptyl cations have been investigated by PMR spectroscopy. A variety of procedures, conventional as well as novel ones, for preparing stable solutions of these cations are briefly described.Tertiary hexyl and heptyl cations rearrange rapidly to equilibrium mixtures of the isomeric tertiary hexyl and heptyl cations, respectively. The equilibrium compositions show the differences in thermodynamic stability of isomeric tertiary carbonium ions to be small. Equilibrations effected by a single 1,2‐hydride or methyl shift between equivalent positions have half‐lives of less than 10−3 s at ‐ 60 °C. Rearrangements of the type tert‐2‐methylpentyl to tert‐3‐methylpentyl cation have a half‐life of about 0.1 s at 0° (Eact = ∼ 14 kcal/mole, and Sact = ∼ 0). For these rearrangements a stepwise mechanism by successive hydride, methyl and hydride shifts via secondary carbonium ions is in agreement with the experimental data. Rearrangements of tertiary carbonium ions involving a change in the degree of chain branching (monobranched to linear or to dibranched cations) have half‐lives of the order of 10 s at 0°.