bluuebunny/crossref_metadata_2025 huggingface dataset:
The Stability of Some Metal Complexes in Mixed Solvents
Authors: Mui Kwan-Kit , McBryde W. A. E. , Nieboer Evert
Published: May 2006

Acidity constants and stability constants of certain metal complexes (nickel(II), zinc(II), and manganese(II)) with ethylenediamine and glycine were determined at 25 °C and in 0.1 M ionic strength in mixed aqueous solutions of methanol (MeOH), dioxane (DOX), acetonitrile (MeCN), and dimethylformamide (DMF). In general, the stability constants of the metal complexes and the first protonation constant of glycine increase with increasing composition of the co-solvent in the order[Formula: see text]The protonation constants of ethylenediamine pass through a minimum at some particular solvent composition, while the second protonation constant of glycine exhibits behavior characteristic of the particular solvent employed.These results are discussed in terms of medium and solvent effects and properties of the solvent that might affect these, but find more satisfactory explanation in terms of solvent displacement during the association reactions. The observations can be accounted for in terms of a complete equilibrium constant incorporating the concentration (activity) of each solvent substance.
Enthalpy–Entropy Compensation for Micellization and Other Hydrophobic Interactions in Aqueous Solutions
Authors: Jolicoeur Carmel , Philip Patrick R.
Published: May 2006

The temperature dependence of the critical micelle concentration for 26 ionic and 48 non-ionic surfactants in aqueous solutions has been reexamined and used to calculate ΔHm0 and ΔSm0, the heats and entropies of micellization, at 25 and 50 °C. ΔHm0 and ΔSm0 values exhibit a significant correlation with compensation temperatures (Tc) of 319 and 222 °K at 25 °C for the groups of ionic and non-ionic surfactants respectively. These results are compared with Tc values which are expected to be characteristic of pairwise interactions between hydrophobic solutes.
The Determination of Traces of Bismuth by Solid State Luminescence
Authors: Ryan D. E. , Rollier H. , Holzbecher J.
Published: May 2006

Traces of Bi(III) are determined with good selectivity by measurement of the luminescence (λex = 355 nm; λem = 430 nm) of CaO:Bi phosphor after co-precipitation with calcium oxalate and ignition at 850–900 °C. The detection limit is better than 0.01 μg Bi in 15 mg CaO; bismuth can be quantitatively recovered from 500 ml sample volumes and analysis is possible for 0.02 ng Bi/ml. The method has been successfully applied to the determination of trace amounts of bismuth added to synthetic blood and kidney samples.
Constituents of Solidago Species. Part VI. The Constitution of Diterpenoids from a Chemically Distinct Variety of Solidagoserotina
Authors: McCrindle Robert , Nakamura Etsu
Published: May 2006

One known (1) and eight new (3, 5, 6a, 7, 8a, 15, 16, and 19b) diterpenoids have been isolated from a chemically distinct subgroup within the species Solidagoserotina Ait. The constitution and stereochemistry of the new compounds are deduced from their spectroscopic properties and chemical reactions. Of key importance are the conversions of (i) 6a and 8a into 8b, which has been synthesized from methyl kolavenate (9); (ii) 1 and 15 into 3; and (iii) 15 and 19b into 16. Also discussed are the cleavages of the epoxides 10 and 15 with boron trifluoride which result in rearrangement, the products being 12 and a mixture of 16, 17a, and 17b, respectively.
The Preparation and Crystal Structure of [I2]+[Sb2F11]−
Authors: Davies C. G. , Gillespie R. J. , Ireland P. R. , Sowa Joy M.
Published: May 2006

The crystal structure of the compound I2+Sb2F11− has been determined from three-dimensional X-ray counter data. Crystals are monoclinic with a = 13.283(5), b = 8.314(3), c = 5.571(2) Å; β = 103.75(2)°; V = 579.5 Å3;Z = 2 and Dc = 3.92 g cm−3. The structure has been refined in the space group C2 with a final conventional R factor of 0.055 for 365 independent reflections with I ≥ 3σ(1). The structure consists of discrete I2+ cations and Sb2F11− anions, each with a crystallographic two-fold rotation axis through the center. The I—I bond length is 2.557(4) Å while the Sb—F bridge length is 2.00(1) Å with a bridge angle of 166(3)° in the symmetric anion.
The Crystal Structure of Tripotassium bis(Oxalato)dioxovanadate(V) Trihydrate
Authors: Drew R. E. , Einstein F. W. B. , Gransden Susan E.
Published: May 2006

The potassium salt of bis(oxalato)dioxovanadate(V), K3[V(O)2(C2O4)2]•3H2O crystallizes in a triclinic lattice with space group [Formula: see text] Two formula units make up the asymmetric unit which has dimensions a = 7.851(2), b = 11.603(2), c = 7.778(2) Å, α = 94.26(1), β = 110.07(1), γ = 91.25(1)°. Three-dimensional single-crystal X-ray diffraction counter data was refined by full-matrix least-squares techniques to R = 0.039. Hydrogen atomic parameters were included in the 213 variables used. A total of 3869 reflections was measured of which 85.4% were classed observed by the criterion I ≥ 2.3σ. The 563 unobserved reflections were included in the final cycle of structure-factor calculations but were not used in the refinement.The anion has irregular octahedral geometry with the two double-bonded oxygen atoms (V=O, 1.628(2) and 1.639(2) Å) cis to each other. The V—O (oxalate) bonds are of two significantly different types: (i) those that are trans to each other (2.009(2), 1.995(2) Å) and (ii) those that are trans to oxo ligands (2.158(2), 2.230(2) Å). The non-coplanar oxalate ligands are twisted about the C—C single bonds (1.550(3) and 1.551(4) Å), while the terminal C—O bonds average to 1.226(9) Å, and the inner ones to 1.274(16) Å. The anions exhibit an approximate non-crystallographic two-fold axis, though distortions from regularity are found. These distortions may best be attributed to hydrogen bonding with the three water molecules and, to a much lesser extent, by contact with the potassium ions.
Excess Volumes, Ultrasonic Velocities, and Adiabatic Compressibilities for Binary Cycloalkanol Mixtures at 25 °C
Authors: Kiyohara Osamu , Grolier Jean-Pierre E. , Benson George C.
Published: May 2006

Molar excess volumes and ultrasonic velocities were determined for the systems cyclopentanol + cyclohexanol, cyclopentanol + cycloheptanol, and cyclohexanol + cycloheptanol at 25 °C. Values of the adiabatic compressibilities were calculated from the experimental results.
Etude de l'influence de l'ionicité du milieu réactionnel sur les propriétés texturales de gels d'oxyde de titane
Authors: Brusset Henry , Mendelbaum Henri-Georges , Flicoteaux Chantal
Published: May 2006

A systematic study has been made of the influence of two factors on the synthesis of titanium dioxide gels: (i) the acidity of the reaction medium and (ii) the presence of a solvent. This study demonstrates that, in an aqueous acid medium, the development of textural properties is related to the concentration of free hydrogen ions. The presence in an acid reaction medium of a solvent, such as butanol or benzene, of low dielectric constant, inhibits the development of the structural properties by lowering the ionic dissociation of the acid. Our results provide an explanation for the apparently divergent measurements in the literature.
Infrared and Raman Spectra of Arylazo Complexes: Assignment of ν( N=N ) in Some Molybdenum and Tungsten Polypyrazolylborate Compounds of the Type [RB(pz)3M(CO)2(N2Ar)]
Authors: Sutton Derek
Published: May 2006

The infrared and Raman spectra have been measured for the series of arylazo complexes [RB(pz)3M(CO)2(N2Ar)], where R = H, pz; M = Mo, W; pz = 1-pyrazolyl, and Ar = C6H5, C6D5, p-C6H4F, m-C6H4F, p-C6H4N02, o-C6H4CH3, and o-C6H3(CH3)2. On the basis of spectral shifts (including 15N-substitution) and Raman intensities, a band in the region 1530–1580 cm−1 is assigned as ν(NN) and a band at 1600–1630 is tentatively assigned as having a contribution from the antisymmetric [Formula: see text]
Diffusion of Gases in Porous Solids. I. Theoretical Background and Experimental Method
Authors: Weller K. R. , Stenhouse N. S. , Watts Harry
Published: May 2006

In the past, some authors have not defined the diffusion coefficient appropriate to their experimental system, consequently, valuable data have been lost. We discuss the various diffusion coefficients referred to all possible frames of reference in relation to the choice of a suitable experimental system for the determination of gaseous diffusion coefficients in porous media. A modified Ney and Armistead type diffusion cell is described with an improved method of calculation of results from continuously monitored concentration changes in the diffusion cell.
Sorption and Diffusion of n-Heptane in 5A Zeolite
Authors: Doetsch I. H. , Ruthven D. M. , Loughlin K. F.
Published: May 2006

Kinetic and equilibrium data for sorption of n-heptane in 5A zeolite are presented and discussed in relation to previously reported data for the C2–C4 hydrocarbons in the same zeolite.A satisfactory interpretation of the equilibrium data is obtained on the basis of a simple theoretical model in which it is assumed that there are, within each cavity of the zeolite lattice, two distinct and energetically different adsorption sites. These sites may correspond to the region close to the cavity wall in which adsorption is energetically favorable, giving rise to localized adsorption, and the central region of the cavity in which the sorbate is less strongly bound with greater rotational and translational freedom. The differential diffusivity increases strongly with sorbate concentration and, as with the lighter hydrocarbons, the form of this concentration dependence may be satisfactorily explained by considering the driving force for the transport process to be the gradient of chemical potential. The limiting diffusional activation energy for n-heptane is 7.5 kcal and this value is somewhat higher than the activation energy for the lighter paraffins.
Resonance Raman Spectra of Cu-tetrapyridinoporphyrazine
Authors: Sunder S. , Bernstein H. J.
Published: May 2006

Resonance Raman spectra of dilute aqueous solutions of Cu-tetrapyridinoporphyrazine have been obtained using a tunable dye and Ar+ lasers. Six bands in the spectra have anomalous depolarization ratios. This is the first observation of anomalous polarization in a molecule of C4h point group symmetry. Intensities and depolarization ratio, ρ1, of the observed bands are measured as a function of the wavelength of the exciting radiation. Bands are assigned to different symmetry species on the basis of the dispersion of their ρl values.
Studies on Trifluoromethanesulfonic Acid. Part I. Trifluoromethanesulfonic Acid as a Weak Acid of the Sulfuric Acid Solvent System
Authors: Russell David Graham , Senior John Brian
Published: May 2006

Trifluoromethanesulfonic acid ionizes as a weak acid in anyhdrous sulfuric acid. Conductance measurements and conductimetric titrations with the base potassium hydrogensulfate, lead to a Ka value of 8 × 10−4 mol kg−1 at 25 °C. Trifluoromethanesulfonic acid is thus a weaker acid in this solvent than is fluorosulfuric acid and is similar in strength to chlorosulfuric acid.
Thyroid Hormone Stereochemistry. III. Molecular Structure of Triiodothyropropionic Acid Ethyl Ester
Authors: Camerman Norman , Camerman Arthur
Published: May 2006

The three-dimensional structure of triiodothyropropionic acid ethyl ester has been determined as part of an investigation of the stereochemistry of the thyroid hormones. The compound crystallizes in the monoclinic space group P21/c, with cell dimensions a = 14.60, b = 8.843, c = 16.70 Å, β = 111°27′; Z = four molecules per cell. The structure was determined by direct centrosymmetric phasing procedures to locate the iodine atoms and phasing on the iodines to find the light atoms. Refinement was by anisotropic full-matrix least squares to a final discrepancy value R = 0.038.The two phenyl rings in the molecule are skewed with respect to each other and are not far from being mutually perpendicular, with angles of 88 and 10° between the plane of the inter-ring ether linkage and the planes of the diiodo-ring and the monoiodo-ring, respectively. The conformation is such that the 3′-iodine atom is proximal to the diiodo-ring, similar to the molecular conformation found in the crystal structure of triiodo-L-thyronine hydrochloride.
The Vibrational Spectra of Methyl Cyanoacetate and Methyl Cyanoacetate-d3
Authors: Sinha Deepali , Katon J. E.
Published: May 2006

The i.r. spectra of methyl cyanoacetate in both liquid and solid phases and of methyl cyanoacetate-d3 in the liquid phase have been recorded in the region 4000–250 cm−1. The Raman spectra of both the compounds in the liquid phase have also been recorded. A tentative vibrational assignment has been made both for the light and the heavy ester. Evidence is presented for the existence of conformational isomers in the liquid phase.
Structure of a Phosphonomannan, as Determined by the Effect of Lanthanide Ions on Its Carbon-13 Magnetic Resonance Spectrum
Authors: Gorin Philip A. J. , Mazurek Mytosk
Published: May 2006

The carbon-13 magnetic resonance spectrum of phosphonomannan 2 in deuterium oxide expands on addition of europium and praseodymium chlorides. With the aid of a parallel study on structurally related α-D-mannose-1-phosphate and α-D-mannose-6-phosphate the signal displacements were interpreted in terms of chemical structure. Both ions cause predominantly contact shifts, and in general addition of praseodymium ion produces a downfield shift of the 13C.m.r. signal of the esterified 13C nucleus, which is accompanied by a smaller downfield shift of that of the adjacent carbon. Europium ion produces smaller and approximately equal shifts of signals of the corresponding α-13C and β-13C nuclei, but in the opposite direction and with less broadening. Displacements produced by neodymium chloride were comparable in size and downfield. Other lanthanide chlorides, namely those of ytterbium, holmium, neodymium, and gadolinium, broadened the signal of the 13C nucleus attached to the phosphodiester group without displacement. Changes produced in proton nuclear magnetic resonance spectra of the phosphates and phosphodiester 2 are more difficult to interpret in terms of structure.
The Effects of Adsorbed Ions on Simple Electrode Reactions. II. The Reduction Of Chromium(III) Ion in The Presence of TolueneP-Sulfonate Anions
Authors: Alias Kamaruzzaman , Fawcett W. Ronald
Published: May 2006

The kinetics of electroreduction of Cr3+ ion have been studied at a mercury electrode both in the absence and in the presence of chemisorbed toluene p-sulfonate ions. The rate of the reaction was considerably accelerated in the presence of the chemisorbed anions. Analysis of the data has shown that the reaction acceleration can be accounted for on the basis of Frumkin's theory for double layer effects suggesting that the reaction site is at the outer Helmholtz plane or close to it in the diffuse layer.
Effect of Molecular Weight on Glass Transition by Differential Scanning Calorimetry
Authors: Blanchard Louis-Philippe , Hesse Jean , Malhotra Shadi Lal
Published: May 2006

The influence of molecular weight (900 to 1.8 × 106) on the glass transition temperature of low polydispersity polystyrene (anionically prepared) has been studied by differential scanning calorimetry at heating rates of 5 to 80 °C min−1. Over the range of molecular_weight studied, and at an extrapolated heating rate of 1 °C min−1,[Formula: see text] A thermally prepared polystyrene sample ([Formula: see text]and Pd = 3.2) showed a Tge value of 93 °C, some 10° below the value predicted by the above equation. Low molecular weight species in the highly polydisperse sample are believed to be responsible for the discrepancy. The changes in heat capacity brought about by the glass transitions are accompanied in all cases on heating by an endothermic peak and this regardless of the heating rate (even extrapolated to 1 °C min−1) or the molecular weight of the sample, suggesting that the glass transition phenomenon encountered with polystyrene is a process involving a positive heat effect.
Carbon-13 Nuclear Magnetic Resonance Studies of Some Methyl Substituted Diphenylmethanes
Authors: Buchanan Gerald W. , Montaudo Giorgio , Finocchiaro Paolo
Published: May 2006

Carbon-13 n.m.r. chemical shifts are reported for diphenylmethane and nine methylated derivatives. Results are compared with those for related methylbenzenes. In the case of tri-ortho-substituted materials the predominance of a perpendicular conformation is suggested. Ring current calculations show that in contrast to the 1H chemical shift interpretations, the 13C shielding trends cannot originate primarily from anisotropic effects.
Methyl 5-Bromolevulinate
Authors: MacDonald S. F.
Published: May 2006

Methyl 5-bromolevulinate (30%) is obtained directly by brominating levulinic acid in methanol. The synthesis of 5-aminolevulinic acid over the 5-phthalimido ester thus becomes a three-step one.
Koenigs–Knorr Syntheses of some α-1 → 2 and β-1 → 2 linked Nitro Disaccharides
Authors: Baer Hans H. , Fréchet Jean M.J. , Williams Ursula
Published: May 2006

2,3,4,6-Tetra-O-benzyl-α-D-glucopyranosyl bromide (1) and, in one instance, its α-D-galacto isomer (2) were condensed under conditions of the Heiferich modification of the Koenigs–Knorr reaction with the four stereoisomeric methyl 4,6-O-benzylidene-3-deoxy-3-nitrohexopyranosides having the α-D-galacto (3), β-D-galacto (4), α-D-gluco (5), and β-D-gluco (6) configurations. Six new, 1 → 2 linked, fully blocked nitro disaccharides (7–12) were isolated. The configurations of the disaccharidic linkages were established by n.m.r. spectroscopy to be α in four of the products (8, 9, 11, and 12) and β in two (7 and 10). The steric course of the disaccharide bond formation was found to depend on the anomeric as well as the over-all configuration of the alcoholic components 3–6.
Photoelectron Spectrum and Electronic Structure of Tetrathiofulvalene (TTF)
Authors: Berlinsky A. John , Carolan James F. , Weiler Larry
Published: May 2006

The electronic structure of tetrathiofulvalene (TTF) has been determined from its photoelectron spectrum and the photoelectron data for the tetrahydro derivative of TTF and 1,3-dithiolane. Correlations of the ionization potentials (i.p.) and several molecular orbital calculations are used in the assignment of the photoelectron spectra of these three compounds. The first five i.p. of TTF and their assignment are as follows: 6.92 (3b1u), 8.67 (2b2g), 9.73 (2b1u), 10.16 (au) and 10.49 eV (b3g). The sixth i.p. at 11.00 eV is tentatively assigned to the 1b2g level. The electronic structure of TTF is important in understanding the crystal packing and band structure of the highly conducting salt, TTF•TCNQ.
Electron Spin Resonance Studies of Aliphatic Ammonium Ion Radicals in Aqueous Sulfuric Acid Glasses
Authors: Falle Howard Reginald , Sargent Frederick Peter
Published: May 2006

The reaction of hydrogen atoms with n-butylammonium ions in 6 M sulfuric acid glasses yields a characteristic eight-line e.s.r. spectrum, which is attributable to CH3ĊHCH2CH2NH3+. Evidence is drawn from computer simulated spectra and from the spectra of other alkylammonium radicals to account for this spectrum. Qualitative agreement between the simulated and experimental spectra is achieved by assuming that the CH3ĊHCH2— moiety can adopt a range of conformations and can also undergo torsional motion about the sp2 carbon – methylene carbon bond. The site of hydrogen abstraction from alkylammonium ions is evidently influenced by both NH3+ and CH3 groups; abstraction tends to occur away from the former and adjacent to the latter.
An Electron Spin Resonance Study of Hydrogen Atom Reactions with Butenes Trapped in Aqueous Sulfuric Acid Glasses
Authors: Falle Howard Reginald , Sargent Frederick Peter
Published: May 2006

Hydrogen atom reactions with butenes trapped in sulfuric acid glasses yield sec-butyl radicals by addition and methallyl radicals by abstraction. The character of the e.s.r. spectra due to the CH3ĊHCH2CH3 radicals depends on whether cis-2-butene or trans-2-butene was the precursor. Computer simulated spectra indicate that the most probable conformation for the CH3ĊHCH2CH3 radicals derived from cis-2-butene and trans-2-butene are 'oblique' and 'trans', respectively. Qualitative agreement between the simulated and experimental spectra is achieved by adding together the spectra computed for CH3ĊHCH2CH3 and [Formula: see text] in the percentage ratio 40:60. In computing the spectra for CH3ĊHCH2CH3, it is assumed that the radicals are distributed over a range of conformations and can undergo torsional motion.
Solubility of Indium Trichloride and Some Double Salts
Authors: Kartzmark Elinor M.
Published: May 2006

The solubility of indium trichloride in water has been determined in the range 25 to 110 °C. The ternary systems: indium chloride – sodium chloride–water; indium chloride–calcium chloride–water, and indium chloride–dioxane–water, have been investigated at 25 &([a-z]+);C. Three double salts have been found to occur, having the formulas: 6(InCl3•3H2O)•5(CaCl2•4H2O); InCl3•3C4H8O2•2H2O, and InCl3•2C4H8O2•2H2O.
Di-(1-adamantyl)iminoxy. Preparation and Dipole Moment
Authors: Lindsay D. , Horswill E. C. , Davidson D. W. , Ingold K. U.
Published: May 2006

The di-(1-adamantyl)iminoxy radical, (1-Ad)2C=NO•, has been prepared from the corresponding imine. It is a blue, crystalline material that is stable indefinitely in air at room temperature in the solid state. Dipole moments have been measured in benzene at 30° for the radical (2.90 D), for (1-Ad)2C=NH (2.49 D), and for (1-Ad)2C=NOMe (0.79 D). In the radical the unpaired spin density on nitrogen is estimated to be ca. 25%.
Les phases cyanures de nickel(II) hydratés
Authors: Mathey Y. , Mazieres C.
Published: May 2006

A critical study of the preparation and properties of the hydrated forms of Ni cyanide shows the existence of three different phases in the compounds Ni(CN)2•xH2O.•By X-ray diffraction and u.v.–visible spectroscopy, it is found that all three phases are formed by different stacking of polymeric [Ni(H2O)2Ni(CN)4]∞ layers similar to the [Ni(NH3)2Ni(CN)4]∞ layers existing in Ni amminocyanides, with interlamellar noncoordinated H2O molecules. All three phases are indexed in the orthorhombic system and can be given as Ni(H2O)2Ni(CN)4•yH2O.
Etude des fluorures et oxyfluorures de chlore ClF5 et ClOF3 liquides par résonance magnétique nucléaire
Authors: Alexandre Michel , Rigny Paul
Published: May 2006

Nuclear relaxation time measurements and interpretations of absorption line shape in ClF5 and ClOF3 allow one to complete data for these compounds. Thus, the chemical shift between non-equivalent fluorine atoms in ClOF3 has been found equal to 50 ± 2 p.p.m. The coupling constant, chlorine 35Cl–fluorine is 192 Hz for the axial fluorine, and less than 20 Hz for the equatorial fluorines. In addition to other information, such as exchange times between fluorine atoms in ClOF3, and the mean coupling constant chlorine–fluorine in ClOF3 and ClF3, is reported.
Substrate Activation in the Carboxypeptidase A Catalysis of Ester Hydrolysis
Authors: Murphy Joe , Bunting John W.
Published: May 2006

The hydrolyses of the O-hippuryl derivatives of glycolic acid (1a), 2-methyllactic acid (1b), and p-chloromandelic acid (1c) by bovine carboxypeptidase A display substrate activation. The hydrolyses of the latter two esters also display substrate inhibition at high substrate concentrations (>0.03 and >0.05 M respectively). Partial kinetic analyses are presented, and these phenomena are discussed in terms of reaction schemes which involve substrate binding at both activating and inhibiting regulatory sites.The hydrolysis of 1b by this enzyme is the first indication that the presence of a hydrogen atom on the α-carbon atom of the alcohol moiety is not obligatory for ester substrates of carboxypeptidase A. The binding of 1c at the catalytic site is approximately 1000 times weaker than for O-hippurylmandelic acid and indicates a dramatic influence for the p-chloro substituent on the binding of the phenyl ring of the mandelic acid unit.
Synthesis of 2-O-, 3-O-, and 4-O-β-D-Glucopyranosyl-L-rhamnose, and of 2-O-β-D-Galactopyranosyl-L-rhamnose
Authors: King Russell R. , Bishop Claude T.
Published: May 2006

Reaction of 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl bromide with benzyl-α-L-rhamnopyranoside in the presence of silver carbonate yielded benzyl 2-O-, 3-O-, and 4-O-(2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl)-α-L-rhamnopyranosides in a molar ratio of 1.0:3.6:1.6. The products were separated by preparative t.l.c. Deacetylation followed by hydrogenolysis afforded the unsubstituted disaccharides. Proton magnetic resonance spectra of each derivative and methylation analysis of the disaccharide benzyl glycosides provided confirmation of the structures. The preparation, by a similar method, of benzyl 2-O-β-D-galactopyranosyl-α-L-rhamnopyranoside, characterized as its crystalline acetate, is also described.
Coordination Compounds of Indium. Part XXVII. Addition Compounds of Acetato(dimethyl)indium(III)
Authors: Habeeb J. J. , Tuck D. G.
Published: May 2006

The compound Me2In(OAc), which is polymeric in the crystalline state, reacts with neutral donor ligands in organic solvents to yield three series of adducts. With monodentate donors, the product is Me2In(OAc)L (L = dimethylsulfoxide or pyridine), which is formulated as a five-coordinate monomer in solution. With bidentate donors, the product is either the monomeric six-coordinate Me2In(OAc)LII (LII = ethylenediamine or 1,2-bis(diphenylphosphino)ethane), or the complex [Me2In(OAc)]2LII (LII = 2,2′-bipyridyl or 1,10-phenanthroline). The n.m.r. and vibrational spectra of these compounds are discussed.
Conformational Studies on 1,3-Dioxepanes. Part IV. Applications of Geminal Coupling Constants to Conformational Analysis of 1,3-Dioxepanes
Authors: Grindley T. Bruce , Szarek Walter A.
Published: May 2006

The magnitude of —OCH2O— group geminal H,H coupling contants, the size of the vicinal coupling constants, and the tenets of conformational analysis were used to establish that in solution the conformation of the 1,3-dioxepane rings in derivatives of 1,3:2,5-di-O-methylenemannitol and 2,5-O-methylenemannitol is predominantly the twist-chair in which the C2 axis passes through the acetal carbon.
Infrared Studies of Water in Crystalline Hydrates: K2FeCl5·H2O (Erythrosiderite) and Related Aquopentachloroferrates(III)
Authors: Falk Michael , Huang Chung-Hsi , Knop Osvald
Published: May 2006

Infrared spectra of M2[FeCl5(H2O)] (M = K, Rb, NH4) at different degrees of deuteration were recorded, between 4000 and 300 cm−1, at 30 and −160 °C. The spectra of the three compounds were closely similar, as was that of natural K2[FeCl5(H2O)] (erythrosiderite). They indicate the existence of only one type of water molecule in the structure. The water molecules are symmetric, well separated from one another, and engage in O—H … Cl bonds with O … Cl distances of about 3.22 Å, as estimated from the OH and OD stretching frequencies. These conclusions support the structure proposed for K2[FeCl5(H2O)] by Bellanca and lead to approximate location of the H atoms. The observed mixing of the librational and translational modes, which occurs when the frequencies of translational modes are high, may be characteristic of H2O molecules coordinated to cations of high charge.
Synthesis of 6-Hydroxyfulvenes. II. Isomerization of 7-Oxanorbornadienes and 3-Oxaquadricyclanes
Authors: Bansal Raj Kumar , Mcculloch Archibald Wilson , Rasmussen Paul Wayne , Mcinnes Alister Gavin
Published: May 2006

Substituted 7-oxanorbornadienes (1a–e) isomerize in good yield in the presence of iodine to 6-hydroxyfulvenes (2a–e): the reaction is catalyzed by light. Oxaquadricyclanes having bridgehead methyl substituents (3b, c) also undergo slow photoisomerization (2537 Å) to the same fulvenes. Irradiation of the oxanorbornadienes with bridgehead phenyl substituents (1d, e) resulted in oxepines (7d, e). Phenyl substituted oxaquadricyclanes could not be isolated.
An X-Ray Study of the Synthetic Intermediate 9-Cyano-1,10-Dimethyl-6-Ethylenedioxy-1-Octalin
Authors: Lynton Harry , Siew Pik-Yuen
Published: May 2006

The crystal structure of the synthetic intermediate, 9-cyano-1,10-dimethyl-6-ethy]enedioxy-1-octalin, C15H21O2N, was solved by direct methods. The compound crystallizes in the space group p21/c with cell dimensions a = 12.282(4), b = 7.144(3), c = 15.619(5) Å, β = 104.04(1)°. Refinement was carried out isotropically for hydrogen and anisotropically for non-hydrogen atoms using full matrix least squares to an R-value of 0.043 for 1669 observed reflections.This compound, which has a cis configuration at the octalin ring junction, is a precursor to a moiety of the alkaloid thelepogine. The cis conformation is essential for total synthesis of thelopogine by this route.
Nuclear Magnetic Resonance Studies. XXVII. Homoenolization of Fenchone. A Mechanistic Study Utilizing C And H Nuclear Magnetic Resonance
Authors: Johnson A. L. , Stothers J. B. , Tan C. T.
Published: May 2006

Deuterium exchange occurs at five β positions in fenchone under homoenolization conditions (t-BuO−–t-BuOD, 185°), C-6(exo and endo), C-8, C-9, and C-10. Both13C and 2H n.m.r. methods were employed to monitor deuterium incorporation and the particular advantages of the latter are illustrated. The relative rates of the five exchange processes were determined directly by 2H n.m.r. in contrast to the earlier homoenolization studies for which the stereoselectivity of exchange was established indirectly. The intermediate homoenolate ion can lead to rearrangement and the rearrangement products have been characterized by 13C n.m.r. as the 3,3,6-trimethyl-norcamphors. Homoenolization of this mixture gave further evidence on the stereochemistry of homoenolate formation.
6H-Dibenzo[b,d]pyrans. I. Synthesis
Authors: Devlin John P.
Published: May 2006

The preparation of 2′,4′-dihydroxy- and 2′,6′-dihydroxybiphenyl-2-carboxylic acid lactones (3 and 4) is described. Grignard addition to or direct boron trifluoride etherate – sodium borohydride reduction of these lactones yields respectively these 6,6-substituted (e.g. 6) or the 6,6-unsubstituted (13a) 6H-dibenzo[b,d]pyrans. Evidence that the reductive route proceeds without ring cleavage is presented.
Rotating Ring-disc Electrode Studies of Lead in HCl and NaCl Solutions
Authors: Barradas Remigio Germano , Belinko Keith , Ghibaudi Elena
Published: May 2006

The rotating ring-disc electrode technique was used to investigate the nature of the dissolution reactions that take place during the anodic charging of a Pb electrode in aqueous chloride electrolytes. Chemical dissolution of the PbCl2 film formed on the disc was found to be an important process which occurred prior to and after passivation of the disc electrode. A ring current due to the electrochemical dissolution of the Pb disc was only observed at low disc currents during galvanostatic charging experiments, or at low disc overpotentials in potentiostatic and voltammetric studies. Observations of anodic ring current excursions under potentiostatically cathodic conditions hitherto not reported in the literature are described.
The Photolyses of Chloropentammine and Chloropentakis(alkylamine) Chromium(III) Complexes in Acetone/Water Mixtures
Authors: Wong C. F. C. , Kirk A. D.
Published: May 2006

The photochemistry of the [Cr(RNH2)5Cl]2+ ions where R = H,CH3,C2H5,n-C3H7,n-C4H9 has been investigated in water and in acetone/water solutions at pH 3. In water and in 33 w/w% acetone/water, the predominant reaction for each ion was found to be amine aquation to give predominantly cis-[Cr(RNH2)4(H2O)Cl]2+. Photolysis of [Cr(CH3NH2)5Cl]2+ in acidified acetone yielded a solvent substituted product [Cr(CH3NH2)4(S)Cl]2+ which has predominantly the cis-configuration but the extents of water and acetone substitution were not established. The amine quantum yields are almost solvent independent, only slightly wavelength dependent, and they decrease significantly in going from R = H to R = n-C4H9. The chloride quantum yields, which are of the order of 10−4 at 565 nm, are about an order of magnitude smaller than had been previously reported for [Cr(NH3)5Cl]2+; they are several times larger at 401 nm. The chloride quantum yields show a significant decrease upon changing the solvent from water to 33% acetone/water.The solvent independence of the main photochemical reaction suggests that the reaction is determined primarily by the photophysical properties of the reacting excited state. The different wavelength and solvent dependences of the amine and chloride quantum yields suggest that the two reactions do not originate from the same excited state. In addition the relative constancy of chloride yields as the ligand field strength of the ligands varies supports the idea that the reponsible state is not a ligand field state. Together with the increase in chloride quantum yield at shorter wavelengths, it suggests that the chloride originates from an excited state partaking of ligand to metal charge transfer character.
La photolyse du sulfure de méthyle et de vinyle
Authors: Leduc Gilles , Rousseau Yves
Published: May 2006

The photolysis of methylvinylsulfide in the 230–270 nm region yields products which can be explained by the following primary reactions.[Formula: see text]The methyl and vinyl radicals are titrated by the addition of methyl mercaptan to the system.[Formula: see text]At short photolysis time, the sum of the methane and ethylene quantum yields is near unity.
Water-Soluble Lysine-containing Polypeptides. II. The Interaction of Several Sequential Lysine–Glycine Polypeptides with DNA. A Circular Dichroism Study of DNA Conformation in Annealed Complexes
Authors: Williams Ross E. , Kielland Sandra L.
Published: May 2006

To serve as models of protein–nucleic acid complexes, annealed complexes of several sequential lysine–glycine polypeptides with DNA have been formed. Circular dichroic spectra of the DNA contained in the complexes indicates that several discrete conformations of DNA can exist when complexed.
The Reaction of Hydroperoxides with Triphenylarsine and Triphenylstibine
Authors: Hiatt R. , McColeman Christine , Howe G. R.
Published: May 2006

Triphenylstibine reduced t-BuO2H to t-BuOH almost as fast as Ph3P does, while triphenylarsine reacts only 1/60 as fast. Both reductions are first-order in each component; in ethanol k2 for Ph3Sb and Ph3As are 106.7e−9.7/RT and 109. 1e−15.7/RT, respectively. The reductions are not very sensitive to choice of solvent, but are strongly catalyzed by compounds of molybdenum and vanadium.The relative rate order PH3P ≥ Ph3Sb > Ph3As is ascribed to two conflicting trends, availability of d-orbitals for π-bonding with peroxidic oxygen, and the Group VB to oxygen bond strength.
The Reaction of Hydrogen Atoms with Palladium and its Alloys
Authors: Oates W. A. , Flanagan Ted B.
Published: May 2006

H atoms, which have been generated in the gas phase, have been allowed to interact with palladium metal and several of its substitutional f.c.c. alloys. It has been found that quite high concentrations of interstitial hydrogen can be introduced in this manner even in the absence of poisons such as H2S. The kinetics of hydrogen uptake have been followed as a function of the hydrogen content of the palladium. The kinetics of the subsequent loss of hydrogen from the palladium have been investigated. Mechanisms for the surface reactions of hydrogen on palladium are discussed.
Fluorinated Alkoxides. Part VIII. Mixed Ligand Complexes of Perfluoropinacol with Ni2+, Pd2+, Pt2+ and Cu2+. Solvation Equilibria between 4- and 5-coordinate Ni2+
Authors: Cripps W. Stafford , Willis Christopher J.
Published: May 2006

Perfluoropinacol, (CF3)2C(OH)C(OH)(CF3)2, ionizes by loss of two protons, and the resulting dinegative ion (PFP2−) chelates to Ni2+, Pd2+, Pt2+, and Cu2+. A variety of stable neutral complexes may be isolated if the tetracoordination of the metal ion is completed with two monodentate or one bidentate nitrogen- or phosphorus-containing ligands; square-planar structures are invariably found. The structures of these complexes are contrasted with those of analogous halides, and it is concluded that electronic effects are predominant in determining them, although steric influences may sometimes be important. The ligand field strength of the perfluoropinacolato ion is approximately equal to that of the thiocyanate ion.The nickel complexes Ni(PFP)22− and (PFP)Ni(RNHCH2CH2NHR) react with donor solvents (water, methanol, pyridine, etc.) to give equilibria between four- and five-coordinate solvated species; six-coordinate species are not observed. This unusual behavior is attributed to the steric hindrance imposed by the bulk of the PFP2− ligand.
Energetics of the Ionization and Fragmentation of Phosphorus Trifluoride by Electron Impact
Authors: Torgerson David F. , Westmore John B.
Published: May 2006

Relative intensities and appearance potentials of several positive ions in the mass spectrum of PF3 are reported as well as an ionization efficiency curve for F−, the only negative ion of significant intensity. Probable ion fragmentation pathways are proposed, together with heats of formation of some positive ions, and ionization potentials for PF3, PF2·, and PF. The results are compared with available data for other Group V halides.
Complexes of 2-Mercaptobenzothiazole with Cu(II), Ni(II), Co(II), Cd(II), Zn(II), Pb(II), Ag(I), and Tl(I)
Authors: Khullar I. P. , Agarwala U.
Published: May 2006

The complexes of 2-mercaptobenzothiazole with Cu(II), Ni(II), Co(II), Cd(II), Zn(II), Pb(II), Tl(I), and Ag(I) have been synthesized. Their structures have been assigned on the basis of analytical, spectral (i.r. and visible), and magnetic data.
Horseradish Peroxidase. XVII. Reactions of Compounds I and II with p-Aminobenzoic Acid in Deuterium Oxide
Authors: Hubbard C. D. , Dunford H. B. , Hewson W. D.
Published: May 2006

The kinetics of reactions of horseradish peroxidase compounds I and II (HRP-I and HRP-II, respectively) with p-aminobenzoic acid have been studied in ordinary water and in deuterium oxide solution over a pH (pD) range 3–10, at 25° and at an ionic strength of 0.11. Under the conditions of the experiments the rate of reaction is first order both in substrate concentration and in enzyme concentration in both solvents. An analysis of the pH dependence of the second order rate constant in H2O confirms the presence of two acid dissociation groups on the enzyme with pKa' of 8.6 and ∼0 for HRP-II, whereas for HRP-I the data suggest a pKa of 5.1 on the enzyme and reveal, as previously shown, the influence of the ionization of the substituted ammonium group of the substrate. In deuterium oxide the pD profiles are similar to those in water but significant shifts for both kinetic and acid dissociation constants are observed for both compounds.The numerical values of the isotope effects taken together with previous results in general confirm that with labile substrates the group of pKa 8.6 in H2O on HRP-II is involved in general acid catalysis. p-Aminobenzoic acid is intermediate between labile and somewhat unreactive substrates and behaves similarly to the ferrocyanide ion in that both acid dissociation groups (pKa's 8.6 and ∼0) are influential in the catalysis of substrate oxidation by HRP-II. The kinetic isotope effect for the HRP-I reaction with p-aminobenzoic acid at high pH (pD) is consistent with a rate determining proton transfer but the group of pKa 5.1 in H2O remains unidentified.
Structural Studies of (π-C5H5)2MX2 Complexes and their Derivatives. The Structure of Bis(π-cyclopentadienyl)titanium Dichloride
Authors: Clearfield Abraham , Warner David Keith , Saldarriaga-Molina Carlos Herman , Ropal Ramanathan , Bernal Ivan
Published: May 2006

The crystal and molecular structure of bis(π-cyclopentadienyl)titanium dichloride, (C5H5)2TiCl2, has been determined from three dimensional X-ray data. The crystals are triclinic with a = 7.882(5), b = 19.478(10), c = 12.156(9) Å, α = 90.46(2), β = 102.58(2), γ = 143.49(2)°. Intensity data (3742 reflections above background) were collected by the θ–2θ scan method using an automated counter diffractometer. The structure was refined in space group [Formula: see text] by block-diagonal least squares methods to a conventional R of 0.032. Since Z = 4, there are two symmetry independent molecules per unit cell. However, these two molecules are almost identical structurally. The coordination about the titanium atom formed by the two chlorine atoms and the centroids of the cyclopentadiene rings is that of a distorted tetra hedron. The average Ti—Cl bond distance is 2.364(3) Å and Ti—Cp—(centroid) 2.058 Å The C—C distances vary from 1.339(11) to 1.419(9) Å. The structural results are compared to those for similar type molecules.
Electron Spin Resonance Studies on Ti(H2O)63+ in Frozen Aqueous Solutions of Titanium(III) Chloride, Bromide, Iodide, and Sulfate
Authors: Premović Pavle Ilija , West Paul Ronald
Published: May 2006

Strongly acidic aqueous solutions of titanium(III) chloride, bromide, iodide, or sulfate (0.02 M metal ion) provide no detectable e.s.r. signal at room temperature. In the frozen solution (77 K) an identical spectrum is observed from each sample with [Formula: see text] A maximum signal is observed at 6–8 M added anion, indicating not all titanium(III) species are e.s.r. active. Analysis indicates that the local symmetry of the Ti3+(3d1) ions providing the signal is D3. It is proposed that these ions are Ti(H2O)63+ species located in sites in the ice structure subject to a strong asymmetric electric field from nearby counter ions. Since the spectrum is independent of anion, the counter ions are unlikely to be in the first or second coordination shell of the Ti3+.
Synthesis of some A-Ring Steroidal Cyclopropanols
Authors: Templeton J. F. , Wie C. W.
Published: May 2006

The preparation of two epimeric secondary cyclosteroid alcohols in the steroidal A-ring by an intramolecular 1,3-elimination of bromide with zinc–copper couple is described. Iso merization of the endo-cyclopropanol to the exo-cyclopropanol is shown to occur with either the couple or zinc acetate. Solvolysis of the cyclopropyl tosylates is discussed. Spectral data are recorded.
The Chemistry of Cochliodinal, a Metabolite of Chaetomium Spp.
Authors: Jerram W. A. , McInnes A. G. , Maass W. S. G. , Smith D. G. , Taylor A. , Walter J. A.
Published: May 2006

not available
The Mechanism of the Microbial Hydroxylation of Steroids. Part 2. Hydroxylation of a Δ4-3-Ketosteroid Analog by Rhizopus arrhizus ATCC 11145
Authors: Holland Herbert L. , Auret Barbara J.
Published: May 2006

The Δ4-3-ketosteroid analog (± )-4a-methyl-4,4a,5,6,7,8-hexahydro-2(3H) naphthalenone (1) is hydroxylated at both C-8α and C-8β by Rhizopusarrhizus ATCC 11145. The ratio of C-8α to C-8β hydroxylation is compared with that obtained from the peracid oxidation of 2-ethoxy-4a-methyl-3,4,4a,5,6,7-hexahydronaphthalene (4) and a mechanism is proposed for both microbial and chemical hydroxylation in which the stereochemistry of the product is transition state controlled. The significance of this to the mechanism of microbial C-6β hydroxylation of Δ4-3-ketosteroids is discussed.
General Base Catalysis of β Elimination by a Steroidal Enzyme Model
Authors: Guthrie J. Peter , O'Leary Stella
Published: May 2006

The water soluble steroid 1 acts as a catalyst for the enolization of the ketones 2a-c. The rate enhancement for 1-catalyzed reaction relative to imidazole-catalyzed reaction (R), increases as the size of the aromatic ring system of the substrate increases; a plot of log Rvs π has a slope of 0.43. This is interpreted in terms of hydrophobic binding between steroid α-surface and aromatic ring system which lowers the free energy level of the transition state for steroid-catalyzed enolization.
Autoxidation and Photooxidation of 1,3-Diphenylisobenzofuran: A Kinetic and Product Study
Authors: Howard James A. , Mendenhall G. David
Published: May 2006

Photooxidation of 1,3-diphenylisobenzofuran (DPBF) in aromatic solvents at 30° gives a monomeric peroxide along with minor amounts of o-benzylphenyl benzoate, whereas in CCl4o-dibenzoylbenzene is the principal reaction product. 1,3-Diphenylisobenzofuran is very susceptible to autoxidation at this temperature (kp/(2kt)1/2 = 4 M−1/2 s−1/2, kp ∼ 105 M−1s−1 2kt ∼ 5 × 108 M−1s−1) yielding a polyperoxide (50%) and o-dibenzoylbenzene (35%). Clearly, in the absence of appropriate control experiments, neither rapid disappearance of DPBF nor production of o-dibenzoylbenzene are sufficient to prove the intermediacy of singlet delta oxygen during molecular oxygen oxidations.
Outer Sphere Oxidations of Alcohols and Formic Acid by Charge Transfer Excited States of Iron(III) Species
Authors: Carey John H. , Langford Cooper H.
Published: May 2006

When methanol, 2-propanol, and formic acid are used as scavengers in the ligand to metal charge transfer (l.m.c.t.) photolysis of Fe(OH2)63+, Fe(OH2)5CI2+, Fe2(OH2)8(OH)24+, or FeEDTA, there is a linear relationship between quantum yield for Fe(II) production and scavenger concentration, [S], at higher [S] values. Extrapolation of the linear portions to [S] = 0 gives an intercept corresponding to the limiting yields observed for scavenging with tert-butyl alcohol. Butanol scavenging at the limit has been shown to give the primary free radical yields from photolysis of aquo iron(III) species. Nuclear magnetic resonance relaxation time studies show that alcohols do not coordinate to Fe(III) and calculations from known stability constants indicate that formic acid does not coordinate under the experimental conditions. The increase of Fe(II) yields with [S] is attributed to an outer sphere oxidation of noncoordinated organic species by the charge transfer excited states of Fe(III) species. There is no discrimination among the organic reductants. The results may be understood without postulating a long lifetime for the Fe(III) l.m.c.t. states if the reaction is assumed to occur only with organic molecules in encounter with the Fe(III) complex at the time of excitation. Organic products were formaldehyde from methanol oxidation and acetone from 2-propanol oxidation. The Fe(II): formaldehyde stoichiometry was 2:1.
Chemically Induced Dynamic Nuclear Polarization During Irradiation of Phenol in the Presence of Amides
Authors: Vaish Shiv P. , Chen Holger E. , Tomkiewicz Micha , McAlpine Robert D. , Cocivera Michael
Published: May 2006

Irradiation of D2O solutions containing various phenols with aliphatic amides at pH values between 9 and 12 results in nuclear spin polarization which is observed as n.m.r. emission signals during irradiation. No polarization is observed for the phenols which include tyrosine, cresol, p-hydroxybenzoic acid, phenol, and others. For the amides which include acetamide, propionamide, N-methylacetamide, and N,N-dimethylacetamide, polarization was observed for only the protons on the carbon bonded to the carbonyl group. Because excited phenolate ions are known to eject electrons, it is proposed that the radical RĊ(O−)NR2 is formed by reaction of the amide with the hydrated electron. The polarization observed for the amides can be explained by reaction of RĊ(O−)NR2 with a benzosemiquinone radical via a radical pair.
π-Perfluoroallyltricarbonylcobalt: Synthesis and Reaction with Triphenylphosphine
Authors: Stanley Keith , McBride D. W.
Published: May 2006

Perfluoroallyl iodide reacts with Zn[Co(CO)4]2 to give π-C3F5Co(CO)3 and CF3CF=CFCo-(CO)4. The reaction of π -C3F5Co(CO)3 with PPh3 gives two products; trans-CF3CF=CFCo(CO)3PPh3 and a compound tentatively identified as cis-CF2=CFCF2Co(CO)3PPh3; (cis and trans refer to configuration about cobalt). Infrared and n.m.r. data for the compounds are reported.