bluuebunny/crossref_metadata_2025 huggingface dataset:
An investigation of the dilute solutions of lauric acid and laurate ion in cationic and anionic bilayers of disc micelles
Authors: Fujiwara F. Y. , Reeves L. W.
Published: May 2006

Type II DM mesophases with disc-shaped micelles have been synthesized from decylammonium chloride and sodium decylsulphate – decanol amphiphiles with added water and electrolyte. Small amounts of guest amphiphiles have been added in the form of lauric acid or laurate ion. Specific and perdeuterated amphiphiles have been prepared and included in small quantifies in the mesophases. The deuterium magnetic resonance spectra of the magnetically aligned phases has been studied and quadrupole splitting doublets assigned to all segments of both host and guest hydrocarbon chains. The mesophases have been diluted with water over the stable range of type II DM behaviour at 34 ± 0.2 °C.The quadrupole splittings of all hydrocarbon chain segments, which reflect the degrees of order along C—D bonds in these segments, are accurately reproduced at all water contents by a knowledge of one quadrupole splitting in the chain and a simple proportionality constant which is derived for each segment of the chain. This further extends the previous results for host chains to those of guest chains studied here. The absolute degrees of order of chain segments are greatly influenced by water content because motion of the constituent disc micelles depends on the volume of interstitial water and they also vary in size as water is added. The packing in the bilayer solution of the disc micelles of the amphiphiles is therefore not a function of the interstitial water content in so far as the detailed trans/gauche motions of the hydrocarbon chains are not affected by changes in water content.The lauric acid-d23 chain in the decylammonium chloride bilayer has the same degree of order along the D—D axis and the C—D bond, confirming that the motion of the pseudo rigid chain in the bilayer is cylindrically symmetric. The degree of order profiles of hosts and guests are all quite distinct indicating that chemical identity of the head group and its anchoring in the interface is the main determinant of the motion profiles.
Acid-catalyzed solvolysis: unusually rapid solvolysis of 3-fluoronortricyclene in CD3COOD – 0.1 M D2SO4
Authors: Werstiuk Nick Henry , Timmins George
Published: May 2006

3-Fluoronortricyclene (1a) undergoes unusually facile solvolysis in CD3COOD – 0.1 M D2SO4 at 67 °C and yields 3-acetoxynortri-cyclene-d3 (1d) which ring-opens to a mixture of deuterated norbornyl diacetates. This result contrasts with the behaviour of 3-chloro- (1b) and 3-bromonortricyclene (1c) that undergo cleavage of the three-membered ring in CD3COOD – 0.1 M D2SO4. The estimated rate acceleration for solvolysis of alkyl fluorides in acid media is 107–108.
Studies on the total synthesis of bisindole alkaloids within the voacamine family
Authors: Kutney James P. , Horinaka Akio , Ward Robert S. , Worth Brian R.
Published: May 2006

The reactions of perivinol (27) with voacangine (3), and of perivinol with catharanthine (29), yield in each case two bisindole alkaloids of the voacamine type. 1H and 13C nmr data are used to assign structures to these compounds and the general utility of these techniques for determining the position of attachment of the 2-acylindole unit to the Iboga unit in such compounds is discussed. The reaction of dregaminol (28) with catharanthine is also reported.
The structure of merosinigrin
Authors: Benn Michael
Published: May 2006

On the basis of spectroscopic evidence, a new structure is proposed for merosinigrin, a transformation product of potassium allylglucosinolate (sinigrin).
Biosynthesis of the antifungal sesquiterpene capsidiol. Confirmation of a hydride shift by 2H magnetic resonance
Authors: Hoyano Yumiko , Stoessl A. , Stothers J. B.
Published: May 2006

Direct evidence of a hydride shift in the biosynthesis of capsidiol has been obtained by incorporation studies utilizing deuteriated mevalonolactone (MVA-4,4-d2) and 2Hmr spectroscopy.
Hydrolysis and carbonyl-oxygen exchange in tertiary amides. Estimation of the free energy changes for breakdown and conformational changes of tetrahedral intermediates
Authors: Deslongchamps Pierre , Barlet Roger , Taillefer Roland J.
Published: May 2006

Second order rate constants were measured at several temperatures for the basic hydrolysis and for concurrent carbonyl-oxygen exchange with solvent for N-benzyl-N-methylformamide-18O, N-benzyl-N-methyltrideutéroacetamide-18O, and N-benzyl-N-methyl-α,α-dideuteropropionamide-18O. Carbonyl-oxygen exchange with solvent is rationalized by invoking a conformational change in the tetrahedral intermediate. Energy barriers for these conformational changes are estimated to be of the order of 5.6, 8.0, 8.2 kcal/mol respectively for the above amides.
The kinetics of internal energy randomisation in thermal unimolecular reactions
Authors: Pritchard Huw Owen
Published: May 2006

The aim of this paper is to present a minimal theory of thermal unimolecular reactions, including explicitly the kinetics of intramolecular randomisation processes. A quasi-diatomic model is formulated and, within the framework of the model, both first-and second-order randomisation processes among reactant and product states are examined.It is concluded that a vital mechanism for the intramolecular energy randomisation in thermal unimolecular reactions is a collisional one. On this assumption, a straightforward derivation of the Polanyi–Wigner specific rate function, as we have reinterpreted it, becomes possible.At the same time, anomalies in the fall-off curves for the thermal isomerisations of methyl isocyanide and ethyl isocyanide can be accounted for very simply: in the former case, values for both the first- and second-order randomisation rate constants can be derived, but in the latter case it is only possible to establish a lower limit for the second-order randomisation rate constant.
Horseradish peroxidase. XL. The oxidation of native enzyme to Compound II
Authors: Nadezhdin Alexander D. , Dunford H. Brian
Published: May 2006

The oxidation of native horseradish peroxidase to Compound II by photochemically generated inorganic free radicals [Formula: see text], [Formula: see text], and [Formula: see text] was observed. The rates of Compound II accumulation for different rates of free radical generation and different reagent concentrations have been measured. The interpretation of the experimental data allowed us to estimate the rates of the reactions [Formula: see text], [Formula: see text], and [Formula: see text]: (3–6) × 106 M−1 s−1, (2.2–3.0) × 106 M−1, and [Formula: see text] respectively. Also obtained for all three oxidants were the ratios of the number of free radicals responsible for the heme oxidation to the total number of them attacking the enzyme.
Solid state properties of poly-β-hydroxybutyrate and of its oligomers
Authors: Marchessault R. H. , Coulombe Suzanne , Morikawa Hiromichi , Okamura Keizo , Revol J. F.
Published: May 2006

The solid state properties of poly-β-hydroxybutyrate (PHB) were investigated for samples with degrees of polymerization [Formula: see text] from 4 to 994. The observed melting points ranged from 47 °C to 180 °C. Electron diffractograms on carefully prepared single crystals of a high molecular weight sample provided data which confirmed the reported a and b parameters from X-ray fiber diffraction and provided clear justification for the P212121 space group. The observed intensities in the electron diffractogram, corresponding to (hk0) reflections, were compared with the predicted intensities for two proposed structures in the literature. The observed and calculated structure factors for both structures were in good agreement. Small angle X-ray diffraction of the meridional maximum for annealed "cold drawn" and "hot drawn" fibers showed a distinctly different dependence on temperature than the maximum for stacks of lamellar single crystals. For oligomers a long spacing was observed which was about twice the length of the sample [Formula: see text] multiplied by the crystalline advance per monomer.
Silver(I) complexes of 4,6-dimethylpyrimidine-2(1H)-thione
Authors: Battistuzzi Raffaele , Peyronel Giorgio
Published: May 2006

The following silver(I) complexes of 4,6-dimethylpyrimidine-2(1H)-thione (HL) have been prepared and investigated by conductometric, infrared, and Raman methods: Ag(HL)X (X = Cl, Br, I, SCN), Ag(HL)2X (X = Cl, Br, I, NO3 (MeOH), ClO4 (0.25CHCl3), BF4 (0.25CHCl3)), AgmXn(H2L)n–m (X = Cl: m = 6, n = 11; Br: m = 2, n = 3; I: m = 5, n = 7), AgL, AgL•Ag(HL)NO3, AgL•[Ag(HL)X]2 (X = ClO4, BF4). The HL acts as N,S-chelating ligand in the Ag(HL)X and Ag(HL)2X (X = NO3,ClO4, BF4) complexes and partially in the Ag(HL)2X (X = Cl, Br, I) complexes in which the halide ion is still coordinated. In the AgmXn(H2L)n–m complexes the H2L+ ion is at least partially S-coordinated to some silver ions. In AgL, L− acts as tridentate ligand N,N,S-bridging the silver ions. In the AgL•Ag(HL)NO3 complex the nitrate ion is coordinated.
Bromination–methanolysis of 2,3-disubstituted indoles; effects of side chain structure
Authors: Gross Edward A. , Vice Susan F. , Dmitrienko Gary I.
Published: May 2006

The bromination–methanolysis of 2,3-dialkylindoles has been shown to lead in some cases to good yields of 3-methoxyindolenines via the corresponding 3-bromoindolenines. However, changes in the structure of the C-2 substituent can cause dramatic changes in the reaction pathway. Structural features expected to stabilize the "enamine" tautomeric form of an indolenine make such methoxyindolenines unstable with respect to acid catalyzed conversion to 2-methoxyalkylindole products.
Double layer structure at the mercury/methanol solution interface
Authors: Borkowska Zofia , Fawcett W. Ronald
Published: May 2006

Differential capacity against electrode potential data are presented for the mercury/methanol interface for a variety of salts at 25 °C and for NaClO4 solutions as a function of temperature. Ionic specific adsorption from solutions of KF, NaClO4, and LiBF4 was shown to be absent on the basis of the usual criteria. The dielectric properties of the inner layer are discussed on the basis of the three-state model for solvent structure from which it is deduced that the majority of solvent molecules are adsorbed at mercury with their dipole vectors parallel to the interface. The deep minimum in inner layer differential capacity, which occurs at the same electrode charge density independent of the nature of the salt (−0.05 C m−2), corresponds to conditions for which the surface concentrations of the minority components, dipoles oriented with the field or against it, are equal. The experimental temperature coefficient of the inner layer capacity is a maximum at this charge density in agreement with the predictions of the three-state model.
Solution of the strong-collision master equation for unimolecular reaction
Authors: Vatsya S. R. , Pritchard H. O.
Published: May 2006

A complete solution of the strong-collision master equation for unimolecular reaction is derived, for any number of distinct reaction products. This solution provides exact results for any chemical activation process under the strong-collision assumption.
Catalytic oxidation of n-propane and methyl alcohol over nickel(II) oxide
Authors: Hoodless I. M. , Ross R. A. , Swaminathan R.
Published: May 2006

The catalytic oxidation of propane over nickel(II) oxide has been studied in the temperature range 280 to 490 °C. Complete oxidation to carbon dioxide and water occurred. Fractional rate order dependencies were obtained for propane and oxygen and the reaction was inhibited by water vapour but not by carbon dioxide. It is suggested that the interaction of the adsorbed hydrocarbon with the adsorbed oxygen species, O−, is the rate-limiting step in the reaction at the lower temperature.Preliminary measurements of the oxidation of propane–methanol mixtures indicated that the alcohol supressed carbon dioxide formation. Conductivity studies have shown that, in these mixtures, methanol strongly interacts with the catalyst resulting in surface reduction.
Resonance Raman spectrum of a deuterated crystal violet: [p(CH3)2N•C6D4]3C+Cl−
Authors: Sunder S. , Bernstein H. J.
Published: May 2006

Resonance Raman spectra have been obtained for a deuterated crystal violet [p(CH3)2N•C6D4]3C+Cl−, as a dilute aqueous solution. The assignment of some of the strong features seen in the spectra of crystal violet and deuterated crystal violet is discussed.
Lignin and related compounds. VIII. Lignin monomers and dimers from hydrogenolysis of aspen poplar wood using rhodium-on-charcoal catalyst
Authors: Sudo Kenichi , Mullord Donald J. , Pepper James M.
Published: May 2006

Aspen poplar wood meal has been subjected to catalytic hydrogenolysis in dioxane–water (9:1) at 500 psig initial pressure of hydrogen over a 5% rhodium-on-charcoal catalyst for five hours at 195 + 5 °C. The resulting chloroform-soluble lignin degradation products were separated by cellulose and silica gel column chromatography. The following compounds were isolated and identified: 4-hydroxybenzoic acid (5), 1-(4-hydroxy-3,5-dimethoxyphenyl)-1-propanone (propiosyringone) (6), 2,2′-dihydroxy-3,3′-dimethoxy-5,5′-dipropylbiphenyl (7), 2,3-bis(4-hydroxy-3,5-dimethoxyphenyl)-1-propanol (11), and a mixture of 3-(4-hydroxy-3,5-dimethoxyphenyl)-2-(4-hydroxy-3-methoxyphenyl)-1-propanol (9) and 3-(4-hydroxy-3-methoxyphenyl)-2-(4-hydroxy-3,5-dimethoxyphenyl)-1-propanol (10).
Localized excess electrons in H2O glasses and ice
Authors: Trudel Gerald J. , Gillis Hugh A. , Klassen Norman V. , Teather George G.
Published: May 2006

The yields and decay rates of two types of localized excess electrons, absorbing in the visible (e−vis) and in the infrared (e−ir), have been compared in four pulse-irradiated H2O glasses and their D2O analogues, and in irradiated H2Oand D2O ice crystals, all at 73 K. If it is assumed that extinction coefficients of e−vis and e−ir at 650 nm and 1800 nm, respectively, are independent of isotopic substitution for both glasses and ice, the G's for both types of localized electrons are lower in all the H2O solids studied than in the corresponding D2O solids. The largest effect of isotopic substitution was found in the lifetime of e−vis in the crystal; at 73 K the inital half-life for decay of e−vis is approximately 14 times longer in D2O than in H2O ice. Even at 6 K the decay of e−vis in H2O ice is very rapid with an initial half-life of about 75 ns.
Streaming current detector for reversed-phase liquid chromatography
Authors: Terabe Shigeru , Yamamoto Kiyoshi , Ando Teiichi
Published: May 2006

Fundamental characteristics of the electrokinetic detector for high performance liquid chromatography, whose operating principle is based on the measurement of the streaming current between both ends of a bundle of glass capillaries, were studied under reversed-phase chromatographic conditions. The detector is specifically sensitive to ionizable compounds like carboxylic acids and amines, but is also universally responsive to nonionic compounds. The detection limit for the former compounds was about 10−8 g and for the latter about 10−4 g. The lowest amount actually measured was 5.8 × 10−9 g. The universal detectability makes this type of detector unsuitable for gradient elution. The observed streaming current was in the range of 10−7 to 10−8 A and was highly dependent on the flow rate of the mobile phase. Characteristics of the detectors equipped with some packed beds prepared from porous materials instead of glass capillaries were also investigated.
Protonation acidity constants for some benzamides, acetamides, and lactams
Authors: Cox Robin A. , Druet Linda M. , Klausner Adi E. , Modro Tomasz A. , Wan Peter , Yates Keith
Published: May 2006

Protonation acidity constants for 27 benzamides, acetamides, and lactams have been determined. Ultraviolet, and 13C and 1H nmr, spectroscopic methods were used; almost all the spectra were found to be subject to medium effects, some quite severe, as the sulfuric acid concentration was increased. Despite this, the excess acidity (X-function) method gave accurate [Formula: see text] and m* values. In all cases protonation, followed by a medium shift in the spectrum of the protonated form, was the only process taking place; protonation was essentially complete in 60% H2SO4. The results for the different bases are interpreted in terms of the resonance, inductive, and steric effects in operation in the acid and base forms.
Crystal and molecular structure of [dimethyl(3,5-dimethyl-1-pyrazolyl)(ethanol-amino)gallato (N(2),O,N(3))](η3-cycloheptatrienyl)dicarbonylmolybdenum
Authors: Chong Kenneth S. , Rettig Steven J. , Storr Alan , Trotter James
Published: May 2006

Crystals of [dimethyl(3,5-dimethyl-l-pyrazolyl)(ethanolamino)gallato(N(2),O,N(3))](η3-cycloheptatrienyl)dicarbonylmolybdenum are monoclinic, a = 10.511(1), b = 8.335(1), c = 24.138(3) Å, β = 102.22(1)°, Z = 4, space group P21/c. The structure was solved by Patterson and Fourier syntheses and was reflned by full-matrix least-squares procedures to R = 0.028 and Rw = 0.046 for 3708 reflections with I ≥ 3σ(I). The crystal structure consists of discrete molecules linked by N—H … O hydrogen bonds (N … O = 2.929(5) Å). The Mo atom is in a distorted octahedral environment with the η3-C7H7 ligand occupying one coordination site, trans to the amino nitrogen, as a π-donating ligand. Important bond distances (corrected for libration) are: Mo—O, 2.245(2), Mo—N(amino), 2.249(3), Mo—N(pyrazolyl), 2.270(3), Mo—C(O), 1.950(4) and 1.947(4), Mo—C(C7H7), 2.176(4), 2.364(4), and 2.380(4), Ga—O, 1.919(3), Ga—N, 1.984(3), and Ga—C, 1.982(5) and 1.983(5) Å. An unusual type of disorder is present in which a second image of the molecule, approximately mirrored by the plane y = 1/4, is in evidence at low occupancy.
The structure of chicanine, a new lignan from Schisandra sp.
Authors: Liu Jia-Sen , Huang Mei-Fen , Gao Yao-Liang , Findlay John A.
Published: May 2006

A new lignan, chicanine, isolated from the fruit of Schisandra sp., is shown to possess structure 1, 2S-(3-methoxy-4-hydroxyphenyl)-3R,4S-dimethyl-5S-(3,4-methylenedioxyphenyl)tetrahydrofuran, from spectra analysis and chemical conversions. The tetrahydrofuran ring exists in a "twist envelope" conformation.
Structure and electrochemical behaviour of 2-nitrosoquinoxaline
Authors: Armand Joseph , Armand Yvette , Boulares Line , Philoche-Levisalles Michèle , Pinson Jean
Published: May 2006

It is shown by X-ray crystallography that 2-nitrosoquinoxaline crystallizes as a dimer, the structure of which is established. In solution the monomeric form predominates and the dimerisation equilibrium constant is measured. The electrochemical reduction of 2-nitrosoquinoxaline in acidic medium leads to the oxime of quinoxaline (1H)-2-one (3) through the intermediate hydroxylamine. 3 is electrochemically reoxidized directly to 2-nitrosoquinoxaline.
Effect of the crystallographic inhomogeneity of a polycrystalline electrode surface on the kinetics of the cathodic reduction of anions
Authors: Levi M. D. , Fedorovich N. V. , Damaskin B. B.
Published: May 2006

The effect of crystallographic surface inhomogeneity of a polycrystalline electrode on the kinetics of the electroreduction of anions was investigated. It was established theoretically that corrected Tafel plots for the reduction of anions of S2O82− type should not coincide for different polycrystalline electrodes with a noticeable crystallographic inhomogeneity of the surface. The analysis of experimental data for a polycrystalline silver electrode fully confirms this conclusion.
Nonlocal dielectric response of the electrode/solvent interface in the double layer problem
Authors: Kornyshev A. A. , Vorotyntsev M. A.
Published: May 2006

A theory of the double layer in the electrolyte solution near the electrode surface is formulated in terms of the most general description of the electrode/solvent interface, the ionic plasma being treated in the Poisson–Boltzmann approximation. As a result, the differential capacitance of the electrochemical contact is calculated. In the case of low ionic concentrations [Formula: see text] it takes the form: C−1 = CGC−1 + C*−1, where the CGC is the Gouy–Chapman nonlinear differential capacitance and C* is a "constant" capacitance, not depending on the concentration, but possessing a possible dependence on the charge of the electrode. The "compact layer" capacitance C* is expressed through a unified nonlocal dielectric function of the electrode–solvent system. This may be considered as a formal approval of Grahame's parametrization of experimental data. But the physical meaning of the compact layer capacity is reconsidered subject to the relation obtained with the nonlocal dielectric function. The latter reflects the electronic structure of the metal and the structure of the solvent in contact. Thereby, the possible reasons for the dependence of the "compact layer" capacity on the nature of the electrode, solvent, and the interaction between them are revealed. A generalization of the results on the case of a more general description of ionic plasma is discussed.
The crystal and molecular structure of 2,2-dimethyl-4,4,6,6-tetrafluorocyclotriphosphazene
Authors: Cordes A. Wallace , Swepston Paul N. , Oakley Richard T. , Paddock Norman L. , Ranganathan T. N.
Published: May 2006

Crystals of the title compound are orthorhombic, a = 7.387(1), b = 8.502(2), c = 14.662(2) Å, Z = 4, space group Pnma. The structure was solved by direct methods and refined by least-squares procedures to a final R of 0.058, Rw = 0.097 for the 530 reflections with I > 3σ(I). The P3N3 ring is slightly but significantly non-planar with a crystallographically-imposed mirror plane normal to the ring, and the PN bond lengths in order from the PMe2 group are 1.601(7), 1.552(7), and 1.560(6) Å. The ring angles are 114.0(4)°, (PMe2); 120.0(4)°, PF2; 123.2(5)°, N(3); 119.6(5)°, N(4). The mean exocyclic bond lengths are P—C, 1.77(1), P—F, 1.522(6), and the exoangles are 107.4(4)° (PMe2) and 97.2(3)°, (PF2). The bond lengths within the ring are well described in terms of simple perturbation theory, but comparison with the structures of other molecules shows the importance of factors other than π-electron distribution.
Deuterium isotope exchange between molecular hydrogen and cyclopentylamine1
Authors: Symons E. Allan , Clermont Michel J.
Published: May 2006

Over the temperature range −68 to −10 °C the ability of the alkali metal cyclopentylamide salts to catalyze deuterium exchange between D2 and cyclopentylamine (CPA) is in the order [Formula: see text] The rate constant ratio at −68 °C for CsCPA/LiCPA is > 103. The measured Arrhenius activation parameters and kinetic isotope effect data are only slightly different for the Li and Na salts. The in-solution exchange reaction is so fast for the KCPA and CsCPA catalysts that rate constants independent of mass transfer could not be measured for them in the stirred gas/liquid reactor even at −68 °C.The gas solubility isotope effect, sie = [D2]/[H2], has been determined in CPA over the range −50 to +25 °C. From the values obtained (e.g. 1.08 at 25 °C, 1.10 at −25 °C) and the limited literature data available it appears that the sie for hydrogen gas may be greater for polar than for nonpolar solvents.
Site selective fluorescence and purity of a rare earth garnet crystal
Authors: Haley L. V. , Jacquier B. , Koningstein J. A.
Published: May 2006

Site selective fluorescence spectroscopy of a crystal of europium gallium garnet containing Cr3+ as an impurity has been carried out. An analysis of the experimental results reveals that the strongest fluorescence spectrum between 590.0 nm and 620.0 nm is due to emission from an Eu3+−Cr3+ pair. Fluorescences of farther removed pairs and that of Eu3+ occupying the 8-coordinated d site and 6-coordinated Ga3+ site are also assigned. Energy transfer between the various sites occurs while the excitation spectra for the R lines of Cr3+ show that extremely fast transfer takes place between the R2 and R1 levels.
Studies related to antitumor antibiotics. Part XXIV. High field 1H nmr analysis and conformations of saframycins A and C
Authors: Lown J. William , Joshua Alummoottil V. , Chen Hsiao-Hsiung
Published: May 2006

A detailed analysis of the high field (400 MHz) 1H nmr spectra of the basic antitumor antibiotics saframycin A and C in CDCl3, C6D6, and in aqueous DMSO solutions has been carried out. Selective double irradiation experiments permitted the unambiguous assignment of all the proton chemical shifts and coupling constants. Consideration of the magnitudes of the latter together with specific nOe experiments permits assignment of molecular geometry and average conformations in solution. Selective shifts occurring in DMSO–D2O solutions upon addition of CF3COOD identified the 12-N atom as the site of protonation which result bears directly on the acid promoted binding of these antibiotics to DNA templates as part of their cytotoxic action.
The least-squares triangle: a new method for evaluation of solid phase compositions from solubility measurements
Authors: Lorimer John W.
Published: May 2006

A least-squares method is described for calculating compositions of equilibrium solid phases from data on solubilities and either wet residues or initial compositions for systems of three or more thermodynamic components. The method minimizes the squares of areas of triangles formed by the solubility, wet residue (or initial composition), and solid composition points. Full descriptions of error analyses and hypothesis tests are given, along with an illustrative example and detailed comparisons with the traditional extrapolation method.
Thermodynamics of autoionization of aqueous tetrahydrofuran and 1,2-dimethoxyethane and the structuredness of solvents
Authors: Datta Jayati , Kundu Kiron K.
Published: May 2006

Autoionization constants (Ks) of aqueous mixtures of tetrahydrofuran (THF) and 1,2-dimethoxyethane (DME) containing 10, 30, and 50 wt.% cosolvent in each case have been determined from emf measurements of the cell: Pt, H2 (g, 1 atm)|KOH (m1), KBr (m2), solvent|AgBr, Ag at seven equidistant temperatures ranging from 5 to 35 °C. The standard free energies (ΔG0), entropies (ΔS0), and enthalpies (ΔH0) of autoionization of the solvents were also evaluated from these data. Relative free energy data, δΔG0(≡sΔG0 − wΔG0), for these solvents as well as those for dioxane (D) – water mixtures taken from the literature, when coupled with the previously determined transfer free energies of H+, ΔGt0(H+), yielded ΔGt0(OH−)app (≡ΔGt0(OH−) − ΔGt0(H2O)) values in the mixed solvents. Relative magnitudes of ΔGt0(H+) and ΔGt0(OH−)app and their non-Born parts, ΔGt,ch0(H+) and ΔGt,ch0(OH−)app in particular, suggest that the "basicity" of these aqueous cosolvents decreases in the order DME > THF > D and their "acidity" in the reverse order, as expected from structural and electronic consideration of these cosolvent molecules. Analysis of the relative entropie contributions, Tδ (ΔS0) (≡T (sΔS0 − wΔS0), for the autoionization of these aqueous cosolvents and in particular ΔSt0(H2O) values derived there from, suggests that while THF promotes three dimenstional (3D) ice-like water structures at initial compositions and D induces breakdown of the 3D structures right from the beginning, DME breaks down water structures at initial compositions, but induces some order around 4–14 mol% DME by forming the possible H-bonded bidentate DME–water complexes. And beyond certain compositions, depending upon the relative size and shape, all the cosolvents break down water structure due to packing imbalance.
Substituent effects upon cation–pseudobase equilibration for isoquinolinium and phthalazinium cations
Authors: Bunting John W. , Chew Vivian S.-F. , Sindhuatmadja Shinta
Published: May 2006

pKR+ values have been measured for cation–pseudobase equilibration by 4-X-2-methylisoquinolinium cations (1) (X = Br, CONH2, COC6H5, CN, NO2) at 25 °C, ionic strength 0.1. These pKR+ values are well correlated by Hammett equations using either σ or σ−para substituent constants. The best correlation gives: pKR+ = −8.8 (± 0.3) σp− + 16.5 (± 0.2) (r = 0.998). The value pKR+ = 16.29 measured by Cook et al. (Tetrahedron, 32, 1773 (1976)) for the 2-methylisoquinolinium cation in dimethyl sulfoxide – water solutions is in reasonable agreement with this correlation equation. For the 2-methyl-5-nitrophthalazinium cation, pKR+ = 7.87, and pKRO− = 12.10 for alkoxide ion formation by the pseudobase of this cation.The pH dependence of the pseudo first-order rate constants (kobs) for cation–pseudobase equilibration has been measured for 1:X = CONH2, COC6H5, CN and for the 2-methylphthalazinium cation (3) and its 5-NO2 derivative (4). For each of these cations, [Formula: see text] and kd = k1[H+] + k2 and the parameters [Formula: see text] have been evaluated. For 1:X = CONH2 and CN and 3, kOH is consistent with a correlation line between log kOH and pKR+ established for other isoquinolinium cations (J. Am. Chem. Soc. 99, 1189 (1977)). For 1:X = COC6H5, kOH is seven-fold smaller, and for 4, kOH is five-fold greater than predicted by this correlation line.
The three conformations of 3,5-dichloro-2-hydroxythiophenol in solution
Authors: Schaefer Ted , Veregin Richard P. , McKinnon David M.
Published: May 2006

The long-range spin–spin coupling constants for the sidechain protons in 3,5-dichloro-2-hydroxythiophenol show that the compound exists as a mixture of three conformers in CCl4 solution at 305 K. The conformer, in which the S—H bond is held roughly perpendicular to the ring plane by an [Formula: see text] hydrogen bond, is 13% abundant. The other two conformers, of roughly equal proportions, contain an [Formula: see text] hydrogen bond. One of these has the S—H bond cis to the OH group, the other has it trans. The chemical shifts of the SH proton and of H-6 are in agreement with these conclusions. The free energy preference of the [Formula: see text] over the [Formula: see text] bond is 1140 ± 100 cal/mol at 305 K. The five-bond coupling between the sidechain protons is negative and very likely involves proximate interactions via lone pairs on oxygen and/or sulfur.
Mixtures of methyl isobutyl ketone with three butanols at various temperatures
Authors: Riggio Roque , Ramos Juan F. , Ubeda Mariana Hernandez , Espindola José A.
Published: May 2006

The viscosities, densities, and refractive indices at 20, 25, 30, and 35 °C were determined for the systems: methyl isobutyl ketone–n-butanol (MIK–B1), methyl isobutyl ketone–sec-butanol (MIK–B2), and methyl isobutyl ketone–isobutanol (MIK–B3). From the experimental results the excess volume, excess viscosity, and excess molar free energy of activation of flow were calculated. The deviations from ideality for the excess thermodynamic function are more important for the system (MIK–B2) than for the systems (MIK–B3) and (MIK–B1). This fact is explained by the existence of hydrogen bonds in the alcohols, stronger in the primary alcohols than in sec-butanol.
The structure and conformation of 1-phenyl-2-methylcyclopropene-3-carboxylic acid and cis­2-(m-nitrophenyl)cyclopropanecarboxylic acid
Authors: Korp James D. , Bernal Ivan , Fuchs Richard
Published: May 2006

The structures of cis-2-(m-nitrophenyl)cyclopropanecarboxylic acid (1) and 1-phenyl-2-methylcyclopropene-3-carboxylic acid (2) have been determined by X-ray methods. Crystals of 1 are triclinic, space group [Formula: see text], with a = 7.422, b = 8.615, c = 9.499 Å, α = 60.24, β = 63.76, γ = 71.36°, and two molecules in the unit cell. Crystals of 2 are monoclinic, space group P21/c, with four molecules in a unit cell of dimensions a = 9.345, b = 13.286, c = 8.187 Å, and β = 98.22°. The carboxyl group of 1 approaches the bisecting conformation. The phenyl group is 37° from this conformation, by contrast with the unhindered compound 2-(p-nitrophenyl) cyclopropyl methyl ketone. In 2 the carboxyl group bisects the three-membered ring, indicating that carbonyl-cyclopropene π interactions can occur if sterically allowed. The two rings are essentially coplanar, permitting maximum interaction of the phenyl group and the double bond. In both compounds, the carbonyl oxygen of the carboxyl is the nearer oxygen to the three-membered ring.
A pulse radiolysis study of trapped electrons in aqueous ethylene glycol glasses
Authors: Wu Zhennan , Klassen Norman V. , Gillis Hugh A. , Teather George G.
Published: May 2006

The yield and reaction kinetics of trapped electrons, [Formula: see text] and [Formula: see text], in several ethylene glycol/D2O glasses have been studied from 6–72 K by pulse radiolysis. An increased D2O concentration is believed to increase the concentration of IR-traps thereby leading to a greater [Formula: see text] and to decrease the concentration of VIS-traps thereby increasing the stability of [Formula: see text]. The yield and stability of [Formula: see text] are also increased by lowering the temperature. A redetermination of [Formula: see text] (1.3 × 104 M−1 cm−1 at 1800 nm) confirms earlier values.
Structural studies of steric effects in phosphine complexes. Part XI. Synthesis, characterization, crystal and molecular structure of the dinitrato(trimesitylarsine)mercury(II) dimer
Authors: Alyea Elmer C. , Dias Shelton A. , Ferguson George , Siew Pik Y.
Published: May 2006

The synthesis and crystal and molecular structure of the dinitrato(trimesitylarsine)mercury(II) dimer are reported. The compound [HgAs(mesityl)3(NO3)2]2 belongs to the monoclinic space group P21/c[Formula: see text] with a = 20.001(2), b = 17.591(5), c = 16.553(2), β = 99.991(6), and Z = 4; the asymmetric unit contains two independent half dimers. The structure was refined to a final R of 0.0458 for 2631 observed reflections measured by diffractometer with 2 < θ < 20°. The crystal structure consists of discrete centrosymmetric dimeric molecules of [HgAs(mesityl)3(NO3)2]2 separated by normal van der Waals distances. The mercury coordination in both dimers I and II is characterized by three strong, nearly coplanar bonds (in I Hg—As 2.476(3), Hg—O 2.41(2) and 2.20(2), and in II Hg—As 2.482(3), Hg—O 2.28(2) and 2.39(2), and three weaker Hg—O bonds in the range 2.55–2.90 Å. Both independent trimesitylarsine ligands have the same regular propeller conformation (Hg—As—C—C torsion angles of 45 to 50°) and the largest C—As—C angles (mean value 112.5(8)°) yet determined. The As(mesityl)3 cone angle is 202°. The two independent dimers differ primarily in the orientation of the non-bridging nitrato groups. Nitrato vibrational and arsine 1H nmr data are also presented for [HgAs(mesityl)3(NO3)2]2, which becomes monomeric in dichloroethane solution.
Basicité et structure de phosphoramides aliphatiques: dosage protométrique en solvants non-aqueux
Authors: Bollinger Jean-Claude , Faure René , Yvernault Théophile
Published: May 2006

Brönsted basicities (as half-neutralization potentials) have been determined at 25 °C by potentiometric titrations in nitromethane or in the mixture sulfolane/benzene 98:2 p/p for 19 aliphatic phosphoramides OPXYZ, with X, Y, or Z = Me; OEt; NMe2; NEt2; NHEt; N(CH2)n (n = 3 or 4); or X + Y = —NMe—(CH2)2—NMe—. Almost all of these weak bases give an homohydrogen bonding. Those with an Me or N(CH2)3 substituent are not stable in acidic medium, which is confirmed by back-titration and measure of E vs. time at the equivalent point. After comparing the results obtained in the two solvents, the effect of the nature of the substituents X, Y, Z on half-neutralization potentials and instability in acidic medium is analyzed.
Synthesis and physical properties of the six furylpyridines
Authors: Ribereau Pierre , Queguiner Guy
Published: May 2006

The 3-step synthesis of furylpyridines is described, using ethyl pyridinoylacetates as starting materials for 2-furyl compounds and chloroacetylpyridines for 3-furyl isomers. Furthermore, these last compounds were prepared by a convenient new method for 3-substituted furan synthesis. This synthesis starts from bromopyridines and proceeds through the key intermediates (2,2-diethoxyacetyl)pyridines and methyl 2-(x-pyridyl)-4,4-diethoxy-2-methoxy-2-butenoates. The physical properties of the furylpyridines have been determined. Structures and interactions between furan and pyridine rings have been discussed by comparing their uv spectra, basicity constants, and dipole moments with those of phenyl and thienylpyridines.
The H3O+ ion in aqueous sulfuric acid
Authors: Giguère Paul A.
Published: May 2006

not available
Platinum group elements in seawater. I. Palladium
Authors: Weiss H. V. , Fresco James
Published: May 2006

Palladium was coprecipitated quantitatively from seawater with an added bismuth carrier precipitated as a sulfide. The 109Pd formed upon neutron irradiation of the isolated material was measured by γ-ray spectrometry following radiochemical purification. By this procedure the concentration of palladium in Pacific coastal water was measured as 2.2 ± 1.2 × 10−10 g per L.
Energy partitioning in some atom/radical reactions found in atmospheric pollution systems
Authors: Donaldson D. J. , Sloan J. J.
Published: May 2006

A modification of the arrested relaxation infrared chemiluminescence technique has been used to study the energy disposal in two atom–radical reactions. Vinyl and formyl radicals were generated chemically and their subsequent reactions with O atoms (in the case of vinyl) and F atoms (in the case of formyl) were followed. Product CO emission was observed in the system O/C2H3. Emission from both CO and HF was seen in the F/HCO system. The O/C2H3 reaction gives rise to substantially higher excitation in the CO product than does the F/HCO case. In each case, bound intermediates may be formed; the differences in energy diposal are discussed in terms of the possible influence of these intermediates.
Visible electronic absorption spectrum of vinyl radical
Authors: Hunziker H. E. , Kneppe H. , McLean A. D. , Siegbahn P. , Wendt H. R.
Published: May 2006

A simple, banded absorption spectrum has been detected by photochemical modulation spectroscopy in Hg-photosensitized reactions forming vinyl radicals. It starts at 499.5 nm, reaches maximum intensity ε ≈ 30 M−1 cm−1 around 400 nm, and contains progressions of 1200 and 920 cm−1 vibrations. These features are compatible with the electronic structure, equilibrium geometries, and energies of the 2A′ ground and 2A″ first excited states of vinyl which were determined by abinitio SCF calculations. The upper state of the observed transition is analogous to the [Formula: see text] state of the isoelectronic formyl radical.
Tungsten carbonyl complexes of Main Group IV organometallic sulfides
Authors: Lucas C. Robert
Published: May 2006

Vibrational spectroscopic data from the literature and from seven new compounds is treated by the methods of Cotton and Kraihanzel and of Graham. The results are interpreted as evidence that in (R3MSPh)W(CO)5 (R = Me, Ph: M = Si, Ge, Sn) there are W → S dπ–dπ and S → M pπ → dπ components to the bonding, the extent of the latter varying in the order Si > Ge > Sn. It is concluded that changes in the carbonyl stretching spectra reflect changes in electron density on sulfur. Thus, the carbonyl spectra are affected both by the electronegativity of groups bound to sulfur and by the extent of S → M π-bonding. The fact that changing M affects spectroscopic properties of a bond three atoms away represents long range transmission of effects via multiple bonds but in a manner quite unlike that in conjugated organic systems.
Enantiomeric synthesis of 9-hydroxy-(E)-2-decenoic acid, a queen honeybee pheromone
Authors: Kandil Ali A. , Slessor Keith N.
Published: May 2006

S-(+)-, R-(−)-, and (±)-9-hydroxy-(E)-2-decenoic acid have been synthesized by organocuprate-catalyzed opening of S-(−)-, R-(+)-, and racemic methyl oxiranes. This acid, of unknown chirality, is an important constituent of the honeybee queen's mandibular gland.
The autoxidation of unsaturated lipids in micelles. Synergism of inhibitors vitamins C and E
Authors: Barclay Lawrence Ross Coates , Locke Steven Jeffrey , MacNeil Joseph Mark
Published: May 2006

The kinetics of thermally (30 °C) initiated autoxidations of unsaturated lipids, linoleic acid, and methyl linoleate are studied in 0.50 M sodium dodecyl sulfate (SDS) micelles. The rate of chain initiation, R1, was controlled by using known amounts of the thermal initiator, di-tert-butylhyponitrite (DBHN). The initiator efficiency, e, determined by the induction period method with x-tocopherol, was 0.30 for linoleic acid and varied (0.30 to 0.36) for methyl linoleate autoxiation as the concentration of the ester increased. The rate of autoxidation of linoleic acid follows the classical rate law since it is proportional to the substrate concentration and to the square root of chain initiation. The oxidizability of linoleic acid measured in micelles is 4.09 × 10−2 M−1/2 s−1/2. The oxidizability of methyl linoleate varied from 2.37 × 10−2 to 6.92 × 10−2 M−1/2 s−1/2 as the amount of solubilized ester increased. The latter results are indicative of pooling of the ester in the micellar phase. Additions of aqueous solutions of ascorbic acid to α-tocopherol-inhibited micellar autoxidations result in very significant extensions of the efficient inhibition period compared to that obtained with α-tocopherol alone. The mechanism of this synergism is briefly discussed.
Charge distributions and chemical effects. XXXI. Molecular energies of ethylenic compounds
Authors: Béraldin M.-T , Fliszár S.
Published: May 2006

not available
A kinetic study of the hydrogenation of hexene-1 catalyzed by a ferrocenyl-phosphine derivative of ruthenium(II)
Authors: Rodgers Glen E. , Cullen William R. , James Brian R.
Published: May 2006

The complex, dichloro(triphenylphosphine){1-[N,N-α-dimethylaminoethyl]-2-diphenylphosphinoferrocene}ruthenium(II), prepared from RuCl2(PPh3)3 by ligand displacement, catalyzes the hydrogenation of terminal olefins under mild conditions. The experimental rate-law for hydrogenation of hexene-1 in n-butanol at 40 °C shows a first-order dependence on both olefin and hydrogen, and an inverse dependence to added triphenylphosphine. The dependence on ruthenium goes from first- to half-order with increasing metal concentration. The kinetic data, together with spectroscopic data, and studies on reactivity of the complex toward hydrogen, are interpreted in terms of catalysis via a ruthenium(I) complex that dissociates a phosphine ligand to generate the active species.
Methylmercury(II) sulfhydryl interactions. Potentiometric determination of the formation constants for complexation of methylmercury(II) by sulfhydryl containing amino acids and related molecules, including glutathione
Authors: Arnold Alan P. , Canty Allan J.
Published: May 2006

Formation constants for the interaction of methylmercury(II) with 2-mercaptoethanol, mercaptoacetic acid, O-methyl-mercaptoacetate, 2-mercaptosuccinic acid, L-cysteine, D,L-penicillamine, N-acetyl-D,L-penicillamine, glutathione, thiocholine, and 4-mercapto-N-methylpiperidine have been determined by potentiometric titration. For the equilibrium [Formula: see text], log β occurs in the range 14.60(1)–17.14(1), with the lowest value obtained for the cationic complex of thiocholine, [Formula: see text]. Acid dissociation constants for the ligands are reported. Formation constants for the addition of both one and two equivalents of MeHg(II) to L-cysteine have been determined, giving log K ca. 4.1 for the reaction[Formula: see text]occurring at low pH, and log K 8.8 for the reaction[Formula: see text]occurring at higher pH.
The nature of bonding in hexahalothorates and hexahalouranates(IV)
Authors: Westland Alan D. , Tarafder M. T. H.
Published: May 2006

Enthalpies of reaction have been determined by solution calorimetry for the process 2AX(c) + ThX4(c) = A2ThX6(c) where A = K, Cs and X = Cl, Br. The measurements afforded the following values of standard enthalpies of formation [Formula: see text], in kJ mol−1: K2ThCl6, −2108; Cs2ThCl6, −2151; K2ThBr,−1774; Cs2ThBr6,−1826. The standard enthalpies of formation of ThCl62− (g), ThBr62− (g), UCl62− (g), and UBr62− (g) and the two-halide ion affinities of ThCl4, ThBr4, UCl4, and UBr4 were compared by assuming semi-empirical (Kapustinskii) values of the lattice energies of the complexes. Homolytic and heterolytic bond energies were also calculated.
Energy transfer by an exchange mechanism in fluid solutions. A generalized treatment
Authors: Martinho J.M. G. , Conte C.
Published: May 2006

Energy transfer in solution by an exchange mechanism has been analysed. The diffusion equation with an added sink term describing the energy transfer process was solved for steady-state conditions using the radiation boundary condition. The transfer rate constant so obtained takes into account the possibility that the reaction does not occur during an encounter. In the limit the equations contain the cases of totally absorbing and totally reflecting barriers. The short range effects were analysed and their influence was introduced under new boundary conditions.
Selenoketone spectroscopy: vibronic analysis of the and n → π electronic transitions in F2CSe
Authors: Bölük M. Y. , Moule D. C. , Clouthier D. J.
Published: May 2006

The spectrum of F2CSe has been surveyed over the 700–200 nm wavelength region and three distinct absorptions identified. These are the spin-allowed, [Formula: see text] and spin-forbidden [Formula: see text] overlapping n → π* transitions, λmax = 434 nm, and the orbitally-allowed [Formula: see text] transition, λmax = 236 nm. Vibrational assignments for the band systems have been made and the out-of-plane energy levels analyzed in terms of a quadratric-Lorentzian double minimum potential. The barriers to inversion for the Ã1A2/ã3A2 states were found to be 2483/2923 cm−1 and the out-of-plane angles 30.1/31.4 deg. The singlet–triplet separation was E(Ã1A2) − E(ã3A2) = 671 cm−1 The [Formula: see text], system displays continuous structure and was not subject to a vibrational analysis.
Platinum(II) and magnesium(II) nucleotide complexes. Synthesis, FT-ir spectra, and structural properties
Authors: Tajmir-Riahi H. A. , Theophanides T.
Published: May 2006

Guanosine-5′-monophosphate (5′-GMP) reacts with Pt(II) and Mg(II) metal ions to give complexes of the type Pt(5′-GMP)nCl2•xH2O, cis- and trans-[Pt(NH3)2(5′-GMP)2]Cl2•xH2O and Mg(5'-GMP2)•xH2O, where n = 1, 2, 3, 4 and x = 4–10.Spectroscopic and chemical evidence showed marked similarities with those of the structurally known N7-bonded 5′-GMP complexes of Mn(II), Co(II), Ni(II), Cu(II), and Cd(II) metal ions. Therefore, Pt(II) and Mg(II) are also found to be N7-bonded in these series of nucleotide complexes.The direct phosphate coordination was observed in Mg(II) nucleotide complexes obtained from acidic solution, whereas Mg(II) complexes prepared from neutral solution showed no direct phosphate–Mg(II) interaction. Pt(II) complexes exhibited no direct phosphate metal bonding, while the possibility of an indirect Pt(II)–phosphate interaction through a hydrogen-bonded water molecule can be proposed here.
The crystal structure of N-[[6-methoxy-5-(trifluoromethyl)thio-1-naphthalenyl]thioxomethyl]-N-methylglycine, C16H14F3NO3S2
Authors: Varughese Kottayil I. , Przybylska Maria , Sestanj Kazimir , Bellini Francesco , Humber Leslie G.
Published: May 2006

The crystals of C16H14F3NO3S2 belong to the monoclinic space group P21/c with a = 11.577(1), b = 12.404(1), c = 12.366(1) Å, β = 90.01(1)°, and Z = 4. The structure was solved by MULTAN 78. The parameters were refined by block-diagonal least-squares to a final R of 0.047 for 2679 observed reflections. Of particular interest is an intramolecular attractive interaction between the sulfur and oxygen atoms with an [Formula: see text] distance of 2.879(2) Å, in which oxygen appears to act as an electrophile. Intermolecular hydrogen bonds between the hydroxyl and keto groups join the molecules related through a centre of symmetry into dimers.