bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of water nuclear magnetic resonance relaxation times to study of metal complexes of the soluble soil organic fraction fulvic acid
Authors: Deczky Katalin , Langford Cooper H.
Published: May 2006

The binding of the paramagnetic metal ions Mn2+, Cu2+, and Fe3+ to the acid soluble organic fraction of soils, fulvic acid, has been examined. The measurements use effects on paramagnetic ion induced longitudinal (T1) and transverse (T2) relaxation in the proton magnetic resonance signal of solvent water. The effects of the fulvic acid sample are compared to model ligand effects. Evidence is developed to suggest that Mn2+ forms outer sphere complexes with fulvic acid. On the contrary, Cu2+ and Fe3+ appear to form inner sphere complexes.
Some empirical observations concerning the liquid scintillation counting of coloured solutions
Authors: Wigfield Donald C. , Cousineau Catherine M. E.
Published: May 2006

The colour quenching capabilities of nine dyes have been examined, and compared with the visible absorption spectra of the dyes in toluene solution. From these data an empirical relationship is derived, from which the liquid scintillation counting efficiency is estimated simply from the λmax (wavelength of maximum absorption) of the dye and its absorption, A, at that wavelength. For the particular instrument, window settings, and scintillator solutions used in this work the relationship was[Formula: see text]Colour quenching agents are classified as severe (λmax 380–480 nm), moderate (λmax 480–520 nm), light (λmax 520–560 nm), or zero (λmax > 560 nm).The normal external standard channels ratio method for obtaining counting efficiency of chemically quenched samples has been applied to samples that contain colour quenchers and various combinations of colour and chemical quench. The results are in excellent agreement with the actual counting efficiencies; this result is in direct contrast to current views on the matter. It appears, therefore, that the counting of samples quenched both chemically and by colour may not always be impossible and the user is well advised to investigate his own System to evaluate whether results within acceptable error may be obtained.
Studies with model membranes. Part XXIV. Evaluation of thermodynamic activation parameters, effective fixed charge density, and test of the theory of bi-ionic potential based on the thermodynamics of irreversible processes
Authors: Siddiqi Fasih A. , Beg M. Nasim , Khan M. Ibadur Rahman , Haq Abdul , Saksena S. K. , Islam Badrul
Published: May 2006

The various ionic processes in the membrane System, notably (a) ionic transport, (b) membrane potential, (c) electrical conductivity, (d) ionic distribution equilibria, and (e) spatial distribution of ions and the potential within the membrane have been thoroughly studied with parchment-supported membranes. By applying the theory of absolute reaction rate, various thermodynamic parameters, namely, enthalpy of activation ΔH≠, energy of activation ΔF≠, and entropy of activation ΔS≠ were evaluated. The ΔS≠ values were found to be negative, indicating that diffusion takes place with partial immobilization in the membrane phase. A formal relation between ΔHhydration, ΔFhydration, and ΔShydration of cations with corresponding values of ΔH≠, ΔF≠, and ΔS≠ for diffusion was also worked out. Thermodynamically fixed charge density was evaluated using methods based on thermodynamics of irreversible processes. Potentiometric selectivity and recent theory of bi-ionic potential based on nonequilibrium thermodynamics was tested and found applicable to parchment membranes.
Porphyrin syntheses requiring negative substituents
Authors: Kobayashi Hiroshi , Archibald John L. , MacDonald S. Ferguson
Published: May 2006

Syntheses which convert pyrromethenes, pyrromethanes, or pyrroles to porphyrins in one step are limited by the necessity of avoiding inseparable mixtures of products. Such mixtures from pyrromethenes or pyrromethanes may become separable, and those from pyrroles avoided, if the products bear appropriate negative substituents.It would appear that isomeric porphyrins with two negative substituents, on adjacent and on opposite rings, respectively, do not form mixed crystals (solid solutions) and are easily separated by crystallization.
Pyrazolato bridged binuclear complexes of palladium and platinum
Authors: Bonati Flavio , Clark Howard C.
Published: May 2006

Pyrazolato bridged binuclear complexes of palladium and of platinum, (C8H12X)2M2(μ-Pz2) (X = OCH3 or pyrazolato), are obtained by reaction of (1,5-cyclooctadiene)dichloro-palladium(II) or -platinum(II) with a 1 unsubstituted pyrazole and sodium hydroxide in methanol.
Volatility of amines used for water treatment in steam generating systems
Authors: Balakrishnan Poyilath Varieth
Published: May 2006

The relative volatilities of cyclohexylamine and morpholine in dilute aqueous solution have been measured in the temperature range 150 to 300 °C at the corresponding equilibrium vapour pressure of the solution. Cyclohexylamine strongly prefers the steam phase while morpholine has a relatively volatility close to that of water. In both cases an azeotrope of the amine and water, with a vapour pressure higher than that of either component, must exist; however, with morpholine and water azeotrope formation only occurs above 175 °C. The concentration dependence of the distribution between the steam and solution phases of both amines is explained in terms of their partial ionization in solution.
Influence des composés organiques sur la vitesse d'apparition du complexe de transfert de charge 1Sn(II)—4Sn(IV) dans les bains acides d'étamage brillant
Authors: Verville Gaston
Published: May 2006

The effect of a number of organic compounds on the rate of formation of 1Sn(II)–4Sn(IV) charge transfer complex in acidic stannous sulphate solutions and on the stability of these solutions has been determined by measuring, spectrophotometrically, the change of absorption of these solutions with time. From the results, it is possible to classify these organic compounds into three broad categories in terms of how they affect the formation of the charge transfer complex and the stability of the solution.These results have been interpreted taking into account that the formation of the 1Sn(II)–4Sn(IV) complex depends on the initial concentration of stannic ions present as an impurity in the stannous sulphate solution, the rate of oxidation of the stannous ions, the rate of hydrolysis of the stannic ions, and the stability of stannic colloids that are formed.
Sterically hindered aromatic compounds. VIII. Comparative photochemistry of 2,4,6-tri-tert-butyl- and 2,5-tert-butylnitrosobenzenes
Authors: Barclay L. Ross C. , Carson Derek Leigh , Gray Jean A. , Grossman Michael , Khazanie Prabhaker G. , Milton John R. , Scott Christopher E.
Published: May 2006

Ultraviolet irradiation of hydrocarbon solutions of 2,4,6-tri-tert-butylnitrosobenzene (1) formed [Formula: see text] The initial products were 2-methyl-1-nitroso-2-(3,5-di-tert-butyl)-phenylpropane (Ar—C(CH3)2CH2NO)2 (3) and a mixed dimer (4). Secondary and minor photoproducts isolated included 2-methyl-2-(3,5-di-tert-butyl)phenylpropanal oxime (5), 2-methyl-2-(3,5-di-tert-butyl)phenylpropanal (6) derived from 5, and 1,3,5-tri-tert-butylbenzene (7). The initial products are explained by formation of a tri-tert-butylphenyl radical (15), rearrangement of a hydrogen atom from an orthotert-butyl to the ring in 15, and rapid recombination of the neophyl radical with nitric oxide. Photolysis of 2,5-di-tert-butylnitrosobenzene (2) initially gave [Formula: see text] (10). Product analysis indicated a comparatively complex mixture including 1,4-di-tert-butylbenzene (11), 2,5-di-tert-butylphenol (12), and 2,5-di-tert-butylanilino-p-(2,5-di-tert-butyl)quinone (13). Evidence indicates that 12 and 13 form from free radical reactions involving 10 and the 2,5-di-tert-butylphenyl radical. The different photochemistry of 1 and 2 is discussed in terms of differential steric and conformational effects on the nitroso function which also is evident in their ultraviolet spectra.
Synthesis and reactions of 2-epoxyethylenepyridine 1-oxide with nitrogen, oxygen, and sulfur nucleophiles
Authors: Benderly Abraham , Fuller George B. , Knaus Edward E. , Redda Kinfe
Published: May 2006

The reaction of 2-epoxyethylenepyridine 1-oxide (4), obtained by m-chloroperbenzoic acid oxidation of 2-vinylpyridine (2), with nitrogen, oxygen, and sulfur nucleophiles has been investigated. Reaction of 4 with cyclic or acyclic amines affords pyridylethanolamine 1-oxides 8 which on reductive deoxygenation using palladium-on-charcoal and hydrogen give rise to pyridylethanolamines 9. Similar reactions with sodium ethoxide and sodium thiophenol yield the respective ethyleneglycol 8f and thioethanol 8g derivatives.
Phenol sulfate esters: ultraviolet, infrared, 1H and 13C nuclear magnetic resonance spectroscopic investigation
Authors: Ragan Mark A.
Published: May 2006

Renewed interest in naturally occurring phenol sulfate ester salts has necessitated modem spectroscopic investigation of these compounds. Synthetic methods, plus spectroscopic (uv, ir, 1H nmr, 13C nmr), chromatographic, and electrophoretic properties are given for the potassium salts of phenyl sulfate (1), pyrocatechol disulfate (2), resorcinol disulfate (3), hydroquinone disulfate (4), phloroglucinol mono- (5), di- (6), and tri- (7) sulfates, and for the 2-sulfate (8) and 2,5-disulfate (9) of 1,2,3,5-tetrahydroxybenzene (10). 13C nmr chemical shift effects resulting from the replacement of phenolic —OH with —OSO3K are reported. Spectroscopic properties of the related compounds 1,2,3-tribenzyloxybenzene (11), 2,6-dibenzyloxy-1,4-benzoquinone (12), 2,6-dimethoxy-1,4-benzoquinone (13), 1,3-dibenzyloxy-2,5-dihydroxybenzene (14), and of a tentatively identified 1,3-dibenzyloxy-2,5-dihydroxybenzene monoethyl ether (15) are available as supplementary material.
Photoelectron spectra of 4-substituted stilbenes
Authors: McAlduff E. J. , Chan Tammy
Published: May 2006

The photoelectron spectra of stilbene and 4-R-stilbene (R = CH3O, CH3, F, Cl, NO2) has been determined and the five highest Π ionization potentials assigned. By considering the stilbenes to be formally constituted by union of a styrene and substituted benzene the influence of substituent on molecular orbital energies gas been rationalized. The data suggest that the stilbenes exist in a planar or nearly planar configuration in the gas phase. CNDO/2 calculations have been performed on a wider variety of 4-R-stilbenes (R = NH2, CH3, OH, F, CN, CF3, NO2) and it is suggested that planar configurations also predominate for those stilbenes. First ionization potentials of some of the stilbenes are correlated with bromination and ozonolysis rate data.
β-Lactams. II. The synthesis of cis-N-(2′-carboxyphenyl)-3-N-phenylacetamido-4-methoxymethyl-2-azetidinone
Authors: Just George , Zamboni Robert
Published: May 2006

The synthesis of the β-lactam 19 from anthranilic acid is described.
Allene–methylacetylene isomerization over silica-supported cobalt and iron catalysts
Authors: Khulbe C. P. , Mann R. S.
Published: May 2006

Equilibrium between allene and methylacetylene was studied over iron catalyst in the temperature range of 165 to 200 °C, with allene or methylacetylene as the initial reactant. In both cases similar equilibrium product-distribution (allene 16% and methylacetylene 84%), fairly close to the calculated value, is observed.Kinetics of allene-methylacetylene isomerization was studied between 70 and 165 °C. The order of reaction was always one and temperature independent. Both activity and calculated energy of activation (11.8 and 11.2 kcal/mol over iron and cobalt respectively) were similar for the two catalysts, suggesting that active sites for the reaction were also similar. This similarity, as well as the first order kinetics, are fully explained by a reaction mechanism based on adsorbate migration.
Thermal expansivities of water + tetrahydrofuran mixtures at 298.15 K
Authors: Kiyohara Osamu , D'Arcy Patrick J. , Benson George C.
Published: May 2006

Densities of water + tetrahydrofuran mixtures were measured at 5 K intervals of temperature from 288.15 to 308.15 K. Excess thermal expansion coefficients and partial molar excess thermal expansivities at 298.15 K over the whole mole fraction range were derived from the results. The significance of the expansivities is discussed in terms of the structural changes accompanying the formation of the mixture.
Heats of mixing of trialkylamines: disorder and steric hindrance contributions
Authors: Philippe Robert , Delmas Geneviève , Hong Phuong Nguyen
Published: May 2006

Nine trialkylamines, triethyl- to trihexylamine trioctyl-, tridodecyl, tri(methyl-2-butyl)-, and dimethyldodecylamine have been used for heats of mixing of the following systems at 298 K: A, fourteen systems made of all the possible binary mixtures (except one) of the six shorter amines; B, twelve systems made of a long chain amine, trioctyl-, tridodecyl- or dimethyldodecylamine with the four shorter members of the series; C, two systems consisting of the mixture of two long-chain compounds, trioctylamine with tridodecyl- and dimethyldodecylamine. Heats for the class A systems are less than or equal to 40 J/mol, indicating no net effect of the small polarity of the shorter members of the series. The experimental HE of these mixtures are compared with two theories. The Monte Carlo approach gives good predictions but the heats calculated with the Snider–Herrington theory are too negative. Heats of the class B systems are suitable for the investigation of two new contributions to the heats of mixing, the positive heat of disordering of long-chains HE(dis.) and the negative heat found in systems where one of the components is sterically hindered, HE(ster.hindr.). HE(dis.) found with the long-chain amines indicates an orientational order larger than in the case of the n-alkane of the same chain-length but equivalent to that found in the tetraalkyltin compounds of the same length. Recent work has shown that the tetrapropyl and tetraethyltin derivatives when mixed with long-chain alkanes or tin derivatives give rise to a HE(ster.hindr.) contribution. From this work and the present study, the steric hindrance contributions of five sterically hindered compounds tetraethyltin and tetrapropyltin, triethyl- and tripropylamine, and 3,3-diethylpentane mixed with different second components are calculated. The steric hindrance contribution is found proportional to the volume of the second component and increasing in the following order of the sterically hindered component: triethyl- < tripropylamine < tetraethyl- < tetrapropyltin < 3,3-diethylpentane. Heats of the class C systems are small without significant contribution of HE(dis.) due to the fitting of the long-chains in solution.
The Raman spectra of tetrachloroantimony(V) dichloro nonafluorodiantimonate(V), tetrachloroantimony(V) undecafluoroantimonate(V), and related molecules
Authors: Ballard Jack G. , Birchall Thomas
Published: May 2006

The Raman spectra of [SbCl4+][Sb2Cl2F9−], [SbCl4+][Sb2F11−], [AsCl4+][SbF6−], and SbCl4F(NbF5)x are reported. The spectra of all compounds except the last are interpreted in terms of a tetrahedral cation with weak association between the cation and anion. The spectra of the adduct found between SbCl4F and NbF5 are interpreted in terms of polymeric fluorine bridged arrangements.
Inductive substituent constants from dissociation of methyl-substituted 3-picolinium ions
Authors: Fischer Alfred , King Murray John , Robinson Frank Price
Published: May 2006

The dissociation constants of 30 α-substituted 3-methylpyridinium ions in water at 25 °C have been measured by potentiometric and spectrophotometric methods. Correlation of the pK values with σI values gives, for n = 16, slope ρI = 3.044, intercept −pK0 = −5.59, correlation coefficient r = 0.993, and enables new σI values to be evaluated. Application of the dual substituent parameter equation gives λ(≡ρR/ρI) = 0.04, confirming that resonance effects are negligible in this series. Dissociation constants of the 3-pyridinylmethylammonium ion and its N-methyl and N,N-dimethyl derivatives are also reported.
Inductive substituent constants from dissociation of methyl-substituted 4-picolinium ions
Authors: Fischer Alfred , King Murray John , Robinson Frank Price
Published: May 2006

The dissociation constants of 29 α-substituted 4-methylpyridinium ions in water at 25 °C have been measured by potentiometric or spectrophotometric methods. Correlation of the log K values with σI values gives, for n = 13, slope ρ = 2.922, intercept log K0 = 5.93, correlation coefficient r = 0.990. Effective σI values evaluated from the dissociation of substituted 4-picolinium ions are in good agreement with those calculated from dissociation of substituted 2- and 3-picolinium ions and with literature values. pK values of the 4-pyridinylmethylammonium ion and its N-methyl and N,N-dimethyl derivatives are 8.22, 8.48, and 7.63, respectively.
Studies on nucleation phenomena occurring in aqueous solutions supersaturated with calcium sulfate. II. The induction time
Authors: Keller Douglas Martin , Massey Ronald E. , Hileman Jr. O. E.
Published: May 2006

The results of a set of experiments designed to delineate the effects of changes in temperature and supersaturation levels on the length of the time interval between establishing those levels and the detection of a steady-state nucleation rate of CaSO4•2H2O from solution are reported. The data were obtained using the droplet technique coupled with insitu generation of SO42− at such a rate that the system experienced a near step function change in the driving force with time. A theoretical model for the length of the time interval is derived and compared with the data. Empirical modeling studies led to a rather different functional relationship that is compared with a theoretical model discussed in the literature by Frisch and Carlier. The functional form of an equation relating together the lag time and the subsequent nucleation rate exhibited by a given system is proposed.
Sensitized photolysis of bis(acetylacetonato)copper(II); general reaction pattern
Authors: Buono-Core Gonzalo , Iwai Kiyoshi , Chow Yuan L. , Koyanagi Tohru , Kaji Aritsune , Hayami Jun-Ichi
Published: May 2006

Bis(acetylacetonato)copper(II) was sensitized by some ketones with a wide range of triplet energies to undergo photodecomposition to give the same products as that obtained in the direct photolysis but with much better efficiency. Other sensitizers such as fluorenone and aromatic hydrocarbons failed to sensitize the reaction. There exists no correlation of the sensitizer triplet energies with the sensitization results. This, and rapid quenching processes, indicated that the classical energy transfer process was unlikely. The sensitization process by an electron transfer within an encounter complex was proposed to explain the decomposition of Cu(acac)2; the calculated free energy changes (ΔG) associated with the electron transfer from the available data support the proposal. Chemical reactions of excited state anthracene and 1-cyanonaphthalene with Cu(acac)2 may also occur. Irradiation of Cu(acac)2 in the presence of triphenylphosphine and benzophenone led to an excellent yield of Cu(acac)(PPh3)2 without causing precipitation of copper(I) complexes.
The molecular and crystal structure of [Pt(diethylenetriamine)(guanosine)](ClO4)2
Authors: Melanson R. , Rochon F. D.
Published: May 2006

The crystal structure of [Pt(diethylenetriamine)(guanosine)](ClO4)2 has been determined by X-ray diffraction. The crystals are orthorhombic, space group P212121, with a = 12.486(6), b = 13.444(7), c = 14.678(11) Å, and Z = 4. The structure was refined by block-diagonal least-squares analysis to a conventional R factor of 0.050 and a weighted Rw = 0.045.The coordination around the platinum atom is square planar. Guanosine is bonded to platinum through N(7). The purine planar ring makes an angle of 62.7° with the platinum coordination plane. The structure is stabilized by hydrogen bonding.
Use of scaled-particle theory in the assessment of the Ph4As+/Ph4B− assumption for single ions
Authors: Abraham Michael H. , Nasehzadeh Asadollah
Published: May 2006

A novel method for the assessment of the Ph4As+/Ph4B− assumption for free energies of transfer of single ions has recently been suggested by Treiner, and used by him to deduce that the assumption is not valid for transfers between water, propylene carbonate, sulpholane, dimethylsulphoxide, N-methyl-2-pyrrolidone, and perhaps also dimethylformamide. The basis of the method is the estimation of the free energy of cavity formation by scaled-particle theory, together with the hypothesis that the free energy of interaction of Ph4As+ (or Ph4B−) with solvent molecules is the same in all solvents, ΔGt0(int) = 0. It is shown in the present paper that (a) whether or not the Ph4As+/Ph4B− assumption applies to transfer to a given solvent depends on which other solvent is taken as the reference solvent in Treiner's method, (b) the calculation of the cavity free energy term by scaled-particle theory and by the theory of Sinanoglu – Reisse – Moura Ramos (SRMR) yields values so different that the method cannot be considered reliable, (c) the calculation of cavity enthalpies and entropies for Ph4As+ or Ph4B− by scaled-particle theory yields results that are chemically not reasonable, (d) the hypothesis that ΔGt0(int) = 0 conflicts with SRMR theory, and (e) the conclusions reached by Treiner are not in accord with recent work that in general supports the Ph4As+/Ph4B− assumption for solvents that are rejected by Treiner.
Triphenylphosphine complexes of mercury(II) acetate and fluoroacetates. Preparation, characterization, and spectral studies
Authors: Allman Tim , Goel Ram G. , Pilon Pierre
Published: May 2006

Triphenylphosphine reacts with mercury(II) acetate and fluoroacetates to form complexes of the types Ph3PHg(O2CR)2, (Ph3P)2Hg(O2CR)2, and (Ph3P)3Hg(O2CR)2, where R = CH3, CH2F, CHF2, or CF3. The 1:1 and 2:1 have been isolated and characterized by elemental analysis, molecular weight, and conductance measurements and by vibrational and nmr spectroscopic studies. The formation of the 3:1 complexes is inferred by 31P nmr spectral measurements at 183 K. Both the 1:1 and 2:1 complexes are indicated to be monomeric molecular species in which the O2CR groups are bidentately bonded to mercury. The Hg—O and Hg—P stretching frequencies for these complexes have been assigned by infrared and Raman spectral measurements. The 199Hg–31P spin–spin coupling constants and the 31P coordination chemical shifts for the 1:1 as well as the 2:1 complexes increase in the order: O2CCH3 < O2CCH2F < O2CCHF2 < OCCF3 Correlations between 1J(199Hg–31P) values, 31P coordination chemical shifts, and the pKa values for the carboxylic acids are discussed.
Ethylenediamine-N,N′-diacetic acid complexes with divalent manganese, zinc, cadmium, and lead: a thermodynamic study
Authors: Gualtieri R. J. , McBryde W. A. E. , Powell H. K. J.
Published: May 2006

The four protonation constants are reported for the dianion of ethylenediamine-N,N′-diacetic acid(H2L),25°C, I = 0.10 M(KNO3), (log ki = 9.60, 6.51, 2.12, 1.3). log K(potentiometric) and ΔH(calorimetric) data are reported for the formation of the complexes [ML], M = Mn2+, Zn2+, Cd2+, and Pb2+ (log K = 6.87, 10.99, 9.16, and 10.66; ΔH = −2.9, −24.4, −16.7, and −28.0 kJ mol−1 respectively). The complexes [ZnL] and [PbL] undergo (aqua) proton dissociation reactions, [Formula: see text] log KD = −10.56 and −11.02, ΔHD = +60.7 and +38.5 kJ mol−1, respectively. Potentiometric and nmr studies indicate that the ligand undergoes a slow (metal catalysed) hydrolysis or rearrangement in aqueous acid.
Facile syntheses of the enantiomers of sulcatol
Authors: Johnston Blair D. , Slessor Keith N.
Published: May 2006

The synthesis of R-(−)- and S-(+)-6-methyl-5-hepten-2-ol (sulcatol) from commercially available ethyl S-(−)-lactate via chiral methyloxiranes is reported. Both substances have crystalline intermediates in their synthetic routes insuring high optical purity. The necessity for a simple route to S-(+)-sulcatol results from the identification of this chiral substance in the pheromone complement of Gnathotricusretusus, a northwestern American timber pest.
The reactivity of [C3H3+] ions; a thermochemical study
Authors: Holmes John L. , Lossing F. P.
Published: May 2006

The loss of halogen atom from the molecular ions of compounds of formulae C3H3Cl and C3H3Br produces the cyclopropenium cation as daughter ion. Each reaction takes place with appreciable reverse activation energy, most of which is partitioned into translational degrees of freedom of the products. In marked contrast, the iodo-analogues generate [propargyl]+ as daughter ions at the thermochemical threshold (i.e. Erev for these fragmentations is ∼0). It is proposed that the reason for this behaviour lies in a large activation energy for the reaction [cyclo-C3H3]+ + I• → [C3H3I]+•
The electron spin resonance spectrum of (CH3)313COO
Authors: Howard J. A.
Published: May 2006

The esr spectrum of (CH3)313COO• has been observed in solution and the hyperfine interaction with the carbon-13 nucleus is 3.92 G.
A correction in the published nuclear magnetic resonance spectra of trans-camphane-2,3-diols
Authors: Johnson Mark A. , Fleming Michael P.
Published: May 2006

It is unequivocally shown that the published nmr spectra assigned to 2-endo,3-exo-camphanediol and 2-exo-3-endo-camphanediol should be reversed. The 2-exo,3-endo isomer is prepared unambiguously by hydroboration–oxidation of camphor enol silyl ether.
The synthesis and characterisation of the trifluoromethylsulfates of silver(II) and gold(III)
Authors: Leung Patrick C. , Lee Keith C. , Aubke Friedhelm
Published: May 2006

The new trifluoromethylsulfates Ag(SO3CF3)2 and Au(SO3CF3)3, as well as the compound Cs[Au(SO3CF3)4], are synthesised by the solvolysis of the corresponding fluorosulfates in an excess of trifluoromethyl sulfuric acid. The resulting compounds are characterised by their vibrational spectra and, in the case of Ag(SO3CF3)2, also by esr.
Fragmentation and rearrangement processes in the mass spectra of perfluoroaromatic compounds. Part XI. Heterocyclic derivatives of phosphorus and some transition metals
Authors: Jones Timothy R. B. , Miller Jack M. , Gardner Sylvia A. , Rausch Marvin D.
Published: May 2006

The mass spectra of a number of phospholes and metalloles of general structure 1 and 2 are[Formula: see text]discussed with respect to their fragmentation and ion rearrangement processes. Of special interest is the migration of ring fluorines to the central atom during fragmentation. The bonding principles involved for the postulated intermediates are discussed.
The interaction between the excited triplet state of ketones and olefins: the role of triplet exciplexes
Authors: Loutfy Rafik O. , Dogra S. K. , Yip R. W.
Published: May 2006

The quenching of triplet acetone in degassed acetonitrile solution by electron-rich and electron-deficient olefins has been measured by flash emission technique. With the exception of fumaronitrile, the efficiency of quenching of triplet ketones by olefins is not determined by the triplet energy of the ketone, but by the ability of the excited ketone to donate or accept electrons. The results are consistent with the assumption that back dissociation of the triplet exciplex is an important process in the overall reaction and accounts for quenching rate constants which are less than those for diffusion-controlled reactions. Lifetimes and binding energies of the triplet exciplexes have been estimated.
Violation of the 'para' rule in the boron trifluoride catalyzed cycloaddition of 4,4-dimethyl-2,5-cyclohexadien-1-one to isoprene. Total synthesis of ionene
Authors: Liu Hsing-Jang , Browne Eric N. C.
Published: May 2006

In violation of the 'para' rule, the boron trifluoride catalyzed addition of 4,4-dimethyl-2,5-cyclohexadien-1-one (1) to isoprene gave rise to the unexpected enone 3 as the only adduct. Under similar conditions, the addition of trans-piperylene proceeded as predicted by the 'ortho' rule to give the single adduct 6. Enone 3 was converted in three steps to the naturally occurring hydrocarbon ionene (12).
Reactions of phenyl(trichloromethyl)carbinol with substituted thioureas, thiobenzhydrazide, and amino thiols to form heterocyclic compounds1
Authors: Reeve Wilkins , Coley III W. Robert
Published: May 2006

Phenyl(trichloromethyl)carbinol reacts with bifunctional reagents containing nucleophilic sulfur such as thioureas, thiobenzhydrazide, o-aminothiophenol, etc., in a series of steps involving an initial attack of the sulfur anion on the intermediate epoxide 2 followed by ring closure to a heterocyclic compound. Thiazolidinones, thiadiazinones, benzothiazinones, and thiomorpholinones are easily obtained in yields ranging from 57–20%. Monosubstituted ureas react to give exclusively the 2-substituted iminothiazolidinones. Evidence is presented that these are actually in the aminothiazolone form with considerable zwitterionic character. 1,3-Disubstituted ureas do not give heterocyclic products. The reaction works particularly well with those nucleophiles which are stable to base, contain a sulfur nucleophilic center for the initial step of the reaction (2 to 3) and an amino or imino group properly positioned for the final ring closure to the heterocyclic compound.Hydroxylamine forms α-oximinophenylacetohydroxamic acid, an oxidation–reduction reaction having occurred. Thiophenol forms phenyl(phenylthio)acetic acid in nearly quantitative yield.
An ion cyclotron resonance study of competitive solvation of gas phase anions
Authors: Clair R. L. , McMahon T. B.
Published: May 2006

Reactions of trifluoromethoxide ion, CF3O−, with carboxylic acids have been examined. Facile fluoride transfer is observed to occur to the acids and a subsequent fluoride transfer equilibrium established in mixtures of carboxylic acids. From the equilibrium constant obtained for fluoride transfer acetic acid and propionic acid are found to have near identical fluoride binding energies. Further reaction between the acid solvated fluoride ions and the carboxylic acids is observed to occur resulting in HF displacement and formation of bicarboxylate anions. In mixtures of acetic and propionic acids acetate and propionate anion transfer equilibria are again established. An analysis of the energetics for these processes reveals that propionic acid binds the carboxylate anions more strongly than acetic acid by 0.1 to 0.2 kcal/mol.
Polarizable acid–acid and acid–water hydrogen bonds with H3PO2, H3PO3, H3PO4, and H3AsO4
Authors: Leuchs Martin , Zundel Georg
Published: May 2006

Hypophosphorous, phosphorous, phosphoric, and arsenic acids, pure and their aqueous solutions were studied by ir spectroscopy. Strong continuous absorptions observed with the pure liquid acids and with solutions containing less than one water molecule per acid molecule demonstrate that acid–acid hydrogen bonds in these systems are easily polarizable. The discussion of the PO and AsO bands as well as the discussion of the structure of the continuum demonstrates, however, that the degree of asymmetry of the energy surfaces in these hydrogen bonds is relatively large. It is shown that extended networks of such bonds exist. Due to the polarizability of these bonds, the proton motion in these bonds is strongly correlated. With addition of water, easily polarizable acid–water hydrogen bonds (I) [Formula: see text] (II) are formed. The energy surfaces in these hydrogen bonds are similar to those in the acid–acid hydrogen bonds. With further addition of water, proton boundary structure II receives noticeable weight, i.e., the degree of asymmetry of the energy surfaces in these bonds decreases due to addition of water molecules. The degree of symmetry of the energy surfaces in the acid–water hydrogen bonds increases in the series arsenic, phosphoric, phosphorous, and hypophosphorous acid.
σ complexes as biophysical and biochemical probes. Part III. Competitive demethylation and σ-complex formation in reaction of 4,6-dinitro-7-methoxybenzofuroxan with nucleophiles
Authors: Buncel Erwin , Chuaqui-Offermanns Noemi , Moir Robert Y. , Norris Albert R.
Published: May 2006

4,6-Dinitro-7-methoxybenzofuroxan (4) reacts with MeONa–MeOH or with Et2NH competitively by σ-complex formation and demethylation, by nucleophilic reaction at the aromatic and aliphatic carbon centers, respectively. Carbonate ion in CHCl3 in the presence of 18-crown-6 polyether also results in rapid demethylation. The facile leaving group ability in these SN2 displacements is consistent with the large acidity constant of 4,6-dinitro-7-hydroxybenzofuroxan (pKa ca. −3.7), i.e., 4pK units stronger than picric acid. Some unusual features exhibited in the nmr spectral characteristics of the σ-complexes are accounted for in terms of stereoelectronic effects.
The kinetics and equilibrium of the hydration of phthalaldehyde
Authors: McDonald Robert S. , Martin Earl V.
Published: May 2006

The equilibrium position and the kinetics of the extensive hydration of the title compound 1 have been investigated by spectroscopic (uv and nmr) techniques. The hydrate exists exclusively as the geometrically isomeric 1,3-phthalandiols and the hydration equilibrium constant is 7.7 ± 0.5 at 25 °C. From the temperature dependence of the equilibrium position, values of the enthalpy and entropy of hydration were calculated. The reaction is general acid – general base catalyzed; the Brønsted α and β coefficients are both near 0.5. Catalysis by Zn(II) is observed. The mechanism of the reaction (which probably proceeds via rate-determining formation of the normal gem-diol followed by rapid cyclization) is discussed.An analysis of the thermodynamic data for the hydration of a variety of carbonyl compounds reveals that the degree of hydration is normally determined by both enthalpy and entropy contributions to the free energy. However, the extensive hydration of 1 is determined solely by the enthalpy term. No hydration could be detected for benzaldehyde or the other isomeric dialdehydes.
Modelling of interactions in solutions: alkali halides in DMSO
Authors: Kruus Peeter , Poppe Barbara E.
Published: May 2006

A model of solutions of alkali halides in DMSO is developed. Each ion is described by a radius, a charge, a polarizability, and an exponential repulsion parameter. Each molecule is described by a polarizability, charges, 6-12 energy parameters, and 6-12 distance parameters centered on each of the 10 atoms in the molecule. The model is applied to calculate (i) the vaporization energy of solvent molecules, (ii) single ion solvation energies and configurations of the solvating molecules, and (iii) the energy as a function of reaction coordinate for the formation of an ion pair. The energies and configurations are obtained by allowing the systems to relax to minimum energy configurations by allowing motion of the molecules. The results of (i) give a vaporization energy 60% of the experimental. The results of (ii) give solvation energies in reasonable agreement with the experimental, and configurations which are reasonable from the point of view of mobilities of ions. The results of (iii) show the presence of a distinct solvent separated ion pair which actually has an energy lower than the contact ion pair. Advantages and problems involved in using this approach to model solutions are discussed.
Self-adduct formation in the extraction of cobalt(II) chelates of certain 8-quinolinols
Authors: Rane Arvind T. , Bhatki Kashinath S.
Published: May 2006

Equilibrium distribution ratios have been determined for the extraction of cobalt(II) with 8-quinolinol and its 2-methyl-, 4-methyl-, 5-chloro-, and 5-nitro- analogues into chloroform as a function of pH and reagent concentration at ambient temperature. Except in the case of 2-methyl-8-quinolinol, which formed a simple 1:2 chelate, the extractable complexes were mono-adducts, that is, 1:2 chelates to which a third molecule of the reagent was coordinated. The overall formation constants of the cobalt chelates in aqueous solution were determined. A linear correlationship was observed between the formation constants, adduct formation constants, and the basicity of the reagent. This dependence could be used to predict, based on known data, the stabilities of not yet studied complexes of cobalt with this family of ligands. The distribution coefficients of the chelates and the chelate adducts are discussed in terms of structural influences. A penta-coordinate, square pyramidal structure has been proposed for the self-adducts of cobalt(II) with 8-quinolinols (except 2-methyl analogue).
Synthesis and crystal and molecular structure of ethanolaminogallium dimethyl, H2NCH2CH2O•GaMe2
Authors: Chong Kenneth S. , Rettig Steven J. , Storr Alan , Trotter James
Published: May 2006

Details of the synthesis and physical properties of H2NCH2CH2O•GaMe2 are given. The compound crystallizes in the tetragonal space group P43, a = 12.2771(2), c = 9.7345(4) Å, Z = 8. The structure was solved by Patterson and Fourier syntheses and was refined by fullmatrix least-squares procedures to a final R value of 0.028 and Rw of 0.036 for 1378 reflections with I ≥ 3σ(I). The structure consists of monomeric molecules containing tetrahedrallycoordinated gallium atoms. Molecules are linked by an extensive network of N—H … O hydrogen bonds. Bond lengths (corrected for libration) are: Ga—O, 1.916(5) and 1.917(4), Ga—N, 2.056(6) and 2.072(6), and Ga—C, 1.962–1.974(8–9) Å.
Dichotomous reactions of thioketones with tetracarbonylferrate
Authors: Alper Howard , Marchand Bernard , Tanaka Masato
Published: May 2006

Treatment of nonenolizable and enolizable thioketones, first with disodium tetracarbonylferrate and then with an acid chloride, affords saturated and unsaturated thioesters, respectively. Mechanisms are proposed for these different reactions.
Passage des phosphorinènes aux hexadiényl-3,5-phosphines: un nouveau type de coordinat P(III)-diène pour les métaux de transition
Authors: Mathey François , Santini Catherine
Published: May 2006

The reaction of tertbutyllithium with 1-phenylphosphorinan-4-one yields a mixture of isomeric alcohols which are partly separated as their P-sulfides. This mixture is dehydrated by P4S10 to afford 1-phenyl-4-tertbutylphosphorin-3-ene sulfide. This sulfide with nickelocene and allyl iodide gives a P(III) → Ni(II) complex which reacts with P(OMe)3 to yield a methylphenylphosphorinenium salt. This salt with BuLi and cyclohexanone gives the corresponding open chain product, i.e. a hexa-3,5-dienylphosphine oxide. This oxide is reduced by HSiCl3 to the corresponding phosphine which is characterized as its P → Fe(CO)4 complex. The phosphorinene sulfide is metalated on C(2) by n-butyllithium in THF. The lithium derivative with acetone yields a mixture of 'cis' and 'trans' alcohols which are separated and fully characterized. Significant variations of 2J(H–P), 3J(H–P) coupling constants and ν(OH), ν(P=S) ir frequencies are observed between the two isomers. The mixture of 'cis' and 'trans' alcohols is dehydrated to give a endo-exocyclic diene which is not isomerized when reacted with Fe3(CO)12. A reduction-complexation of the P=S group is observed instead. The 2-lithio-phosphorinene is also reacted with iodine to afford a bridged dimer.
Syntheses and spectroscopic study of a new series of mixed-ligand complexes of As(III) and Sb(III) with dithio-ligands
Authors: Kheiri Fadel M-N. , Tsipis Constantinos A. , Tsiamis Christos L. , Manoussakis George E.
Published: May 2006

Seventeen new mixed-ligand complexes of As(III) and Sb(III) with dithio-ligands have been prepared and studied. The preparation of the mixed-ligand complexes has been made by reacting the corresponding iodobis(dialkyldithiocarbamate) complexes with either CS2 and HNR2 or the sodium salt of the dithiocarbamate. Alteration of the second method facilitated the preparation of the mixed-ligand dithiocarbamate–xanthate complexes of Sb(III) whereas the analogous arsenic compounds have not been isolated. The study of these new compounds reveals that their stability depends on the nature of both ligand and central atom. The spectroscopic data of the compounds are discussed and compared with those of similar complexes of Bi(III).
Etude structurale du monofluorophosphate de potassium K2PO3F
Authors: Payen Jean-Luc , Durand Jean , Cot Louis , Galigne Jean-Louis
Published: May 2006

K2PO3F is orthorhombic, space group Pnma, with a = 7.554(4), b = 5.954(5), c = 10.171(6) Å, and Z = 4. Intensity data have been measured on an automatic diffractometer with CuKα radiation. The crystal structure was determined by analogy with that of K2SO4 and shows an important interaction "F---K". The final R index is 0.065 for 353 observed reflections.
Cycloadditions and other chemistry of 4-oxygenated pyrazoles
Authors: Fagan Paul J. , Neidert Eli E. , Nye Martin J. , O'hare Michael J. , Tang Wah-Piu
Published: May 2006

Several synthetic routes to some new substituted pyrazol-4-ols and the reactions: methylation, acetylation, Michael addition, and oxidation are reported. Synthesis and cycloaddition reactions of the systems pyrazolium-4-olate and 3,4-diazacyclopentadienone are also reported. The former does not cycloadd, whereas the latter behaves as both a diene and a dienophile in various cycloadditions.
Phosphorus-31 nuclear magnetic resonance spectra of methylplatinum(II) and methylpalladium(II) cations containing 4-substituted pyridine ligands
Authors: Clark Howard C. , Milne Charles R.
Published: May 2006

The 31P nmr spectra of the compounds cis-[M(CH3)(L)diphos]PF6, where M = Pd, Pt; L = 4-C5H4NX; X = CH3, H, NMe2, COOMe, COMe, CN; diphos = 1,2-bisdiphenylphosphino ethane, have been recorded. The 31P chemical shifts and 31P–195Pt coupling constants decrease regularly as the ρ values of the substituent on pyridine decrease. These trends are attributed to decreasing lone pair donation from phosphorus as the electron donating ability of the other ligands on the metal increases. The trans influence of the coordinated pyridine molecule, as measured by J(195Pt–31P), is greater than its cis influence on the phosphorus atoms.
Thermodynamics of transfer of hydrogen halides from water to glycerol–water mixtures and the structuredness of the solvents
Authors: Basumallick Indra Narayan , Kundu Kiron K.
Published: May 2006

Standard free energies (ΔGt0) and entropies (ΔSt0) of transfer of HX (X = Br and I) from water to glycerol–water mixtures containing 10, 30, 50, and 70 wt.% glycerol have been determined from emf measurements on the cell: Pt, H2(g, 1 atm)/HX(m), solvent/AgX–Ag at seven equidistant temperatures ranging from 10–40°C. The observed ΔGt0–composition profiles of HBr, HI, and also of HCl obtained from the relevant literature data are essentially similar to those in aquo-alcoholic and aquo-glycolic systems. But the observed short maxima in TΔSt0(HX)–composition profiles with their relative order: HI > HBr > HCl in water-rich compositions and the reverse order at higher proportions of glycerol are indicative of the effect of small structure promoting propensity of glycerol. Comparison of TΔSt0(HI)–composition profiles of methanol, isopropanol, and tert-butyl alcohol on the one hand and that of methanol, ethylene glycol, and glycerol on the other, leads us to suggest that the structure promoting ability of hydrophobic —CH3 group is significantly reduced due to 'specific site hydration' effect when its one H-atom is being replaced by one hydrophilic —OH group. Also, the compositions at which the characteristic maxima appear, either in the former cases or in the latter, are, as expected, the size effect of the co-solvents.
Electrochemical synthesis of some 1,2-dimethyl 1,2-disubstituted ethylenes
Authors: Renaud Roger N. , Champagne Philippe J.
Published: May 2006

The anodic oxidation of sodium acetate in the presence of a series of 1,2-disubstituted ethylenes was performed in acetonitrile–water solution. Under low concentration of substrates, very good yields of the monomeric 1,2-dimethylated products were obtained. In the case of diethyl fumarate, an increase in concentration caused a decrease in the ratio of monomer to polymer when all other parameters were held constant.The stereoisomers of the products were separated and their physical properties are reported.
Spin trapping of the •CO2− radical in aqueous medium
Authors: Harbour John R. , Hair Michael L.
Published: May 2006

The •CO2− radical has been generated by photolysis of a solution of sodium peroxydisulfate containing sodium formate and by hydrogen abstraction using TiCl3 and H2O2 in the presence of sodium formate. In both cases, the inclusion of DMPO resulted in the formation of a spin adduct with aN = 15.8 G, aβH = 19.1 G, and g = 2.0058 which is assigned to the •CO2− adduct. In addition the DMPO adduct of SO4−• is presented. Finally, it is shown that DMPO can react with anionic radicals and that the resultant spin adducts are themselves highly dissociated.
Milieux hyperbasiques: Recherches sur les amides et lactames ω-halogénés. Essais de cyclisation
Authors: Cuvigny Thérèse , Hullot Pierre , Mulot Patrick , Larcheveque Marc , Normant Henri
Published: May 2006

Linear halogenated N,N-disubstituted amides afford cyclic amides in good yields by reaction with 'activated' lithium dialkylamides. However, the same reaction with substituted amides gives mainly ω-ethylenic amides.In the same way, N-substituted γ- and δ-lactams with an ω-halogenated chain in the α position afford pure spirolactams whereas the reaction of ε-Iactams furnishes a mixture of spiro and ethylenic compounds.
Structure et réactivité. III., Evolutions stéréochimiques et chemins réactionnels des radicaux cyclohexyles substitués en 2 et cyclohexényles substitués en 3 (réaction de Kochi)
Authors: Monnier Maurice , Aycard Jean-Pierre
Published: May 2006

The chlorodecarboxylation reaction (Kochi reaction) of a series of cyclohexane and cyclohexene carboxylic acids was investigated. Competitive acetoxy decarboxylation occurs, and the proportion of acetates is shown to increase with steric hindrance due to the R-substituent relative to the radical center. A partial evolution involving high energy conformers is suggested to explain the difference of stereoselectivities in the formation of acetates and chlorides.
Pyrolysis of cyclopentane behind reflected shock waves
Authors: Kalra Bansi L. , Feinstein Stuart A. , Lewis David K.
Published: May 2006

Gas samples containing either 0.20% or 1.0% cyclopentane plus 0.25% tert-butyl alcohol in argon have been heated to 1185–1257 K in a single pulse shock tube. The previously studied dehydration of the alcohol was used as an internal standard reaction for temperature measurement. Pyrolysis of the cyclopentane yielded a broad spectrum of C1–C5 hydrocarbon products; however, the products and their concentration ratios were in good agreement with those recently reported by Tsang, in a comparative rate study of cyclopentane pyrolysis vs. cyclo-hexene decyclization. Thus strong support is offered for Tsang's proposed complex mechanism involving (a) molecular isomerization to 1-pentene and subsequent degradation of that product, (b) molecular decomposition to cyclopropane and ethene, followed by isomerization of cyclopropane to propene, and (c) induced decomposition to a variety of C1–C5 hydrocarbons plus H2 via hydrogen atom abstraction from cyclopentane by various radicals generated from 1-pentene. The only significant disagreement with Tsang's study is a ∼40° temperature discrepancy; possible sources of this are discussed.