bluuebunny/crossref_metadata_2025 huggingface dataset:
Pyrochlores. III. X-Ray, neutron, infrared, and dielectric studies of A2Sn2O7 stannates
Authors: Brisse François , Knop Osvald
Published: May 2006

A number of compositions [Formula: see text] and of related mixed phases were prepared and investigated. For the trivalent lanthanons from La to Lu, and for Y, the homogeneous A2Sn2O7 phases were of the cubic pyrochlore type (space group Fd3m, No. 227). Their lattice parameters gave a very good linear relationship when plotted against the Templeton–Dauben radii of A3+. The applicability of other sets of ionic radii was also tested. The lower limit of the r(A3+):r(Sn4+) ratio for cubic pyrochlore stannates is about 1.19 (Ahrens radii), while the upper limit is at least 1.60. Attempts to extend the lower limit by preparing mixed Yb + Sc stannates were only partially successful. Bi2Sn2O7 is not a cubic pyrochlore.The structures of Y2Sn2O7 and Sm2Sn2O7 were refined from X-ray powder data, and that of La2Sn2O7, from neutron powder data. The positional parameter of the majority oxygen atom, x(O2), has been found to increase with the size of A3+. The distortion of the SnO6 octahedra in the pyrochlore structure thus decreases with increasing r(A3+).From a systematic study of the infrared spectra of the stannates it appears that it is the size of the Y3+ ion rather than its chemistry (as distinct from the Ln3+ ions) that determines its place among the 3–4 pyrochlores. No evidence of ferroelectricity was found in Pr, Er, and Lu stannates between room temperature and 4.2 °K.
Surface oxidation and reduction of platinum electrodes: Coverage, kinetic and hysteresis studies
Authors: Gilroy D. , Conway B. E.
Published: May 2006

Studies on the electrochemical formation and reduction of surface oxide at platinum electrodes have been carried out with particular reference to polarization and hysteresis effects in these processes. Comparisons between the results of galvanostatic and potential sweep techniques have been made for three types of surfaces of platinum electrodes prepared by: (a) heating in hydrogen; (b) heating in a flame; and (c) electrolytically forming platinum black surfaces. The dependence of the quantity of reducible oxide formed under prior steady-state potentiostatic conditions has been related to potential and time of anodic polarization. Polarization effects in the reduction of the surface oxide have been evaluated in terms of the potential dependence of the pseudocapacitance maximum for the oxide reduction process, and a mechanism for the reduction is suggested. The relative slowness of the reduction process is important in regard to the question of the role of oxide in the kinetics of electrocatalytic oxidations at platinum anodes. Hysteresis effects in anodic formation and cathodic reduction of the oxide are discussed in terms of a totally irreversible phase transition involving the ad-layer.
Cinnamaldehydeanil complexes of rhodium(I)
Authors: Kang Jung W. , Maitlis P. M.
Published: May 2006

Cinnamaldehydeanils reacted readily with [Rh(CO)2Cl]2 under mild conditions to form Rh(CO)2ClL (2), where L is PhCH=CH—CH=NPh or PhCH=CH—CH=NTo (Ph = phenyl, To = p-tolyl). Under vigorous conditions RhCl(CO)L2 (3) was isolated from this reaction. From the infrared and proton magnetic resonance spectra the ligands, L, appear only to coordinate through the nitrogen atom to the rhodium.Cinnamaldehyde reacted with Rh(CO)2Cl(p-toluidine) to give (2b) in good yield. Heating (2) in boiling benzene afforded (3) and Rh metal. Triphenylphosphine reacted with (2) or (3) to form RhCl(CO)(PPh3)2. The reaction of (3) with 1,5-cyclooctadiene gave (1,5-C8H12)RhClL, which was also prepared by reaction of (1,5-C8H12RhCl)2 with L.Some electronegatively substituted acetylenes reacted with (3) to yield the stable acetylene complexes (RC≡CR)RhClL2 (R = CF3, COOMe).
Crystal structure of Cu3(AsO4)2
Authors: Poulsen Sandra J. , Calvo C.
Published: May 2006

Cu3(AsO4)2 forms a monoclinic crystal with lattice parameters a = 6.327(5) Å, b = 8.642(5) Å, c = 11.313(5) Å, β = 92.04(4)°, and Z = 4. The space group is P21/c. The two orthoarsenate anions in the unit cell have average AsO bond lengths of 1.68 Å and 1.70 Å with mean deviations of 0.02 Å and 0.01 Å respectively. The three cations are fivefold coordinated to oxygen atoms with mean cation oxygen atom bond lengths of 2.005 Å, 2.053 Å, and 2.017 Å for the three independent cations. The range of bond distances extends from 1.892 Å to 2.362 Å. Only one additional cation oxygen distance of less than 3 Å occurs and this lies at 2.76 Å. The cation polyhedra form sheets parallel to the ab plane by corner and edge sharing of common oxygen atoms. Adjacent sheets are bonded through the long Cu—O bond distance cited above and by the AsO43− anions. Each of the arsenic atoms shares three oxygen atoms with one sheet and one with the adjacent one.
Homogeneous rate of recombination of hydrogen atoms
Authors: Larkin F. S.
Published: May 2006

The rate of decay of hydrogen atoms has been measured in a conventional type of discharge-flow system at temperatures between 190–350 °K. The recombination fitted the equation[Formula: see text]where ks is the first order surface rate constant. No three-body recombination for M = H was observed at the low levels of dissociation (2–5%) employed. When the flow gases contained traces of water vapor and (or) oxygen as impurities, the homogeneous rate constants (k2,M) had a small positive activation energy which was due to the influence of a surface reaction between hydrogen atoms and the impurities. In the absence of impurities, true homogeneous rate constants were obtained. A value of k2,Ar = 4.6 ± 0.5 × 1015 cm6 mole−20s−1 was found at 291 °K. The temperature variation was approximately T−1/2 over the range 190–350 °K.
Absolute rate constants for hydrocarbon oxidation. VIII. The reactions of cumylperoxy radicals
Authors: Howard J. A. , Ingold K. U. , Symonds M.
Published: May 2006

Absolute rate constants have been measured for the reactions of cumylperoxy radicals with a number of hydrocarbons. The cumylperoxy radicals were produced from cumene hydroperoxide. Sufficient hydroperoxide was present to ensure that only cumylperoxy radicals were involved in the rate-determining propagation reaction.Primary and secondary deuterium isotope effects have been measured for propagation and termination in the oxidation of cumene. The rate of hydrogen atom abstraction from ring-substituted cumenes by cumylperoxy radicals can be correlated by the Hammett equation using σ+ substituent constants, ρ = −0.29. Primary and secondary peroxy radicals are about 3–5 times more reactive in hydrogen abstraction than tertiary peroxy radicals.
Dielectric relaxation and orientational ordering of water molecules in hexamethylenetetramine hexahydrate
Authors: Davidson D. W.
Published: May 2006

To account for the dielectric properties of hexamethylenetetramine hydrate, which include a static dielectric constant half that of ice, some modification is necessary of the partial orientational ordering of the water molecules proposed by Mak. It is suggested that water hydrogen atoms occupy fixed positions only in the hydrogen bonds with nitrogen.
Chemistry of episulfides. II. The reactivities of propylene sulfide and propylene oxide towards acetic acid
Authors: Isaacs Neil S. , Neelakantan K.
Published: May 2006

The rates and products of solvolysis of propylene oxide and propylene sulfide in acetic acid have been determined. The results show that terminal attack is preferred, although not exclusively, and that the sulfide is the less reactive by a factor of 50–60. This difference is accounted for mainly in the preexponential factor. Solvent isotope effects are also observed.
The reaction of 1,2,3-thiadiazoles with base. I. A new route to 1-alkynyl thioethers
Authors: Raap R. , Micetich R. G.
Published: May 2006

The reaction between 1,2,3-thiadiazoles, unsubstituted in the 5-position, and a strong base such as an organolithium compound, sodamide, sodium methylsulfinyl carbanion, or potassium t-butoxide results in cleavage of the thiadiazole ring system with evolution of nitrogen and formation of alkalimetal alkynethiolate. Subsequent addition of an alkyl or acyl halide to the reaction mixture produces 1-alkynyl thioethers. 4-(5-Phenyl-1,2,3-thiadiazolyl)lithium, obtained from 5-phenyl-1,2,3-thiadiazole and methyl-or phenyllithium, reacts with methyl iodide to give 4-methyl-5-phenyl-1,2,3-thiadiazole.
Diastereoisomeric 2-aryl-6-methyl-3,4 (1,2-piperido)-oxazines
Authors: Cooke G. A. , Fodor G.
Published: May 2006

The alkaloid sedridine (1) is formed stereospecifically by catalytic hydrogenation of optically active α-picolyl methyl carbinol (2). The levorotatory 1 gave on action of p-nitro benzaldehyde two μ-aryl oxazines, one crystalline and levorotatory, the other oily and dextrorotatory. This is the first example where both epimers of a μ-aryl oxazine could be detected. The configurations and the conformations of these isomers (10 and 11) and those of sedridine have been discussed in terms of their nuclear magnetic resonance spectra, with particular reference to spin-decoupling evidence.
Cationic cyclization of bicyclic diterpenes
Authors: Edwards O. E. , Rosich R. S.
Published: May 2006

Manool and agathadiol cyclize in formic acid to the 13-epimeric pimara-8,15-dienes and 14α-hydroxyhibane derivatives. The mechanistic and biosynthetic implications of these results are discussed in relation to other work involving cations in tetracyclic diterpenes. The nuclear magnetic resonance spectra of relevant tricyclic and tetracyclic diterpenes are documented.
Nitrations of acetanilides by reagents of NO2X type
Authors: Lynch Brian M. , Chen Catherine M. , Wigfield Yuk-Yung
Published: May 2006

The distribution of products in the nitration of a series of eight substituted acetanilides has been studied using differing nitrating agents.With mixed nitric and sulfuric acids, attack para to the acetamido group is favored, while with acetyl nitrate or nitronium tetrafluoroborate, predominant ortho substitution occurs. It is suggested that ortho substitution results from SN2 displacement by a pair of substituent electrons (on nitrogen or carbonyl oxygen) on the species NO2X (X = BF4 or OAc), leading to formation of the most readily accessible σ complex, while the para substitution favored in mixed acids results from substitution in the conjugate acid of acetanilide.Nitroacetanilides follow an unusual path with acetyl nitrate, yielding the corresponding dinitrobenzene in addition to the expected dinitroacetanilides.Nuclear magnetic resonance spectroscopy efficiently demonstrates the structures of the reaction products, and reveals the preferred intramolecularly hydrogen-bonded conformation of ortho-nitroacetanilides.
Velocity of sound in liquid argon at high pressures and temperatures
Authors: Bowman D. H. , Lim C. C. , Aziz R. A.
Published: May 2006

Measurements were made of the velocity of sound in liquid argon in the temperature range 86–146 °K and at pressures up to 65 atm. The velocity versus pressure isotherms are steeper and more curved at the higher temperatures. At any one pressure, the velocity is a smoothly decreasing function of temperature. Analysis of the results using existing density data showed that the specific heat ratio, γ, decreases with pressure and increases with temperature in this range. The coefficient in Rao's relation was found to increase with temperature at constant pressure, while that in the relation due to Carnevale and Litovitz exhibited no definite trend with temperature or pressure.
Transition from internal to external oxidation in indium–silver alloys
Authors: Pethe L. D. , Mathur H. B. , Biswas A. B.
Published: May 2006

The kinetics of oxidation of In–Ag alloys of 5,10, and 15 at. % indium have been studied on a vacuum microbalance. The 15 at. % indium alloy oxidizes externally and the 5 at. % alloy internally. A plot of logarithm of the parabolic oxidation rate, kp, versus reciprocal of the absolute temperature for 10 at. % indium alloy gives two intersecting straight lines corresponding to the energies of activation of 23 and 39.6 kcal/mole for the oxidation below and above 600 °C respectively. These are comparable to the energies of activation of 23 kcal/mole for the internal oxidation of 5 at. % indium alloy and 40 kcal/mole for the external oxidation of 15 at. % indium alloy. The rate–controlling step in the external oxidation of 15 at. % indium alloy is the diffusion of indium through the alloy. Photomicrographs of the cross sections of the oxidized foils of these alloys confirm the conclusions derived from the kinetic data.
Radiolysis of cyclohexane in a xenon matrix at 77 °K
Authors: Stone J. A.
Published: May 2006

Low concentrations (less than 7 mole %) of cyclohexane and cyclohexane-d12 have been irradiated in xenon matrices at 77 °K. The products are qualitatively the same as those obtained by the radiolysis of the pure hydrocarbon but the yields differ. In particular G(H2) = 6.7 for 6.2 mole % cyclohexane is much higher than that for solid cyclohexane at the same temperature (4.65). (All G values are calculated on energy absorbed in the whole sample.) The G values for products are reduced to limiting values, which are ~50–75 % of the initial ones, by low concentrations of SF6. Carbon tetrachloride reduces the yields to a greater extent than does SF6. Both ionic and nonionic product formation probably occur. Ion chamber dosimetry has been used to determine the energy absorption by xenon which is anomalous due to the presence of low energy, scattered gammas in the cobalt-60 source.
Kinetics of neopentyl chloride pyrolysis. II. The radical-chain decomposition
Authors: Shapiro J. S. , Swinbourne E. S.
Published: May 2006

The radical-chain thermal decomposition of neopentyl chloride was studied in the temperature range of 410–496 °C and over the pressure range of 22 to 340 mm. A small surface effect was noted after prolonged conditioning of the vessel and in a vessel of high surface/volume ratio. The reaction is of three-halves order and the rate coefficient is expressible by k3/2 (11/2 mole−1/2 s−1) = 1013.55 ± 0.67 × e−56300 ± 2100/RT. The experimental facts are shown to be consistent with a mechanism involving chlorine atoms as the principal propagating radicals, with a first-order initiation step and a termination step involving the combination of methyl and chloromethyl radicals. The relative concentrations of the various radicals, calculated from known and estimated kinetic parameters, have been shown to be dependent on the hydrogen chloride produced from the concurrent unimolecular decomposition of neopentyl chloride reported in Part I. 1,1-Dimethylcyclopropane, found as a reaction product, is believed to be formed directly from neopentyl chloride by a radical-chain mechanism.
Photometric analysis of trace amounts of hydrazine with p-dimethylamino benzaldehyde. Chemical equilibria. Part II
Authors: Gamble Donald S.
Published: May 2006

Additional chemical equilibrium data are presented for aqueous solutions into which have been put p-dimethylaminobenzaldehyde, HCl, and hydrazine sulfate. The photometric measurement of the thermodynamic equilibrium constant for p-dimethylaminobenzaldehyde protonation agrees to within experimental error with the value from solubility experiments. The average of the two is [Formula: see text].Some analytical chemical applications are discussed.
Refinement of the crystal structure of scandium oxide
Authors: Knop Osvald , Hartley Jean M.
Published: May 2006

The crystal structure of Sc2O3 (C-type; a0 = 9.8459 ± 15 Å at 20 ± 2 °C) was refined from X-ray powder diffractometer data. Isotropic individual temperature factors were used in full-matrix F (19 reflections) and F2 (41 reflections) programs. The positional parameters were determined as u(Sc) = −0.0355 ± 1, x(O) = 0.3933 ± 3, y(O) = 0.1513 ± 3, and z(O) = 0.3835 ± 3. The merits and limitations of refining from careful powder diffractometer data are briefly discussed.
Gas–solid exchange reactions: Zinc vapor and polycrystalline zinc selenide
Authors: Secco E. A. , Su Chien-Huo
Published: May 2006

The exchange kinetics of zinc vapor with polycrystalline zinc selenide have been studied in a static system in the temperature range 720–800 °C.The kinetic data are consistent with a diffusion-controlled process from the initial stage, in contrast with existing exchange data on ZnO and ZnS powders. The diffusion equation is given as:[Formula: see text]
Determination of the heat of formation of trimethylindium and calculation of the mean In—CH3 bond dissociation energy
Authors: Clark W. D. , Price S. J. W.
Published: May 2006

The enthalpy of reaction of In(CH3)3,c with a chloroform solution of bromine is −162.5 kcal mole−1. With this value ΔHf0298[In(CH3)3,c] = 29.5 kcal mole−1 and ΔHf0298[In(CH3)3,g] = 41.1 kcal mole−1. Combining the latter with ΔHf0298[CH3,g] = 33.2 kcal mole−1 and ΔHf0298[In,g] = 58.2 kcal mole−1 then gives E(In—CH3) = 38.9 kcal mole−1. From previous kinetic studies D[(CH3)2In—CH3] + D[In—CH3] = 87.9 kcal mole−1. Hence D[CH3In—CH3] = 28.8 kcal mole−1.
Electrochemistry of zinc, cadmium, and mercury ions in fused AlCl3–NaCl–KCl eutectic
Authors: Hames D. A . , Plambeck James. A.
Published: May 2006

The electrochemistry of the ions of zinc, cadmium, and mercury in the AlCl3–NaCl–KCl eutectic at 150 °C was investigated by e.m.f., voltammetric, and chronopotentiometric techniques. Oxidation states of +2 were observed for these three elements and oxidation states of +1 were observed for cadmium and mercury. Values of equilibrium constants for the reactions [Formula: see text] and [Formula: see text] were calculated to be 26 and 36 000 respectively. A standard potential scale for the Zn(II)/Zn, Hg(II)/Hg(I), Hg(I)/Hg(0), Ag(I)/Ag(0), and Al(III)/Al(0) couples was established in the solvent system AlCl3–NaCl–KCl.
Isomeric yield ratios of 133Xe in fission of 232Th, 233U, 235U, and 238U with protons of energies 20–85 MeV
Authors: Forster. J. H. , Yaffe L.
Published: May 2006

The ratio of 133Xe isomers produced in the fission of 232Th, 233U, 235U, and 238U by protons ranging in energy from 20–85 MeV was measured. The Hafner, Huizenga, and Vandenbosch formalism was applied with different sets of input parameters to establish their effect on the relation between initial fragment spin and isomer ratio for three spin-pair classes of isomers. The isomer ratio was found to be independent of the spin and type of fissioning target and only weakly dependent on projectile energy.
Electrocrystallization and surface diffusion: Effect of chemical reaction in the solution
Authors: Rangarajan S. K.
Published: May 2006

A theoretical solution to the problem of electrochemical crystal growth when (a) surface diffusion, (b) diffusion in the solution phase, and (c) a chemical reaction in the solution are all present is derived. The rate of lattice incorporation is assumed to be finite. A generalized impedance function is derived and its characteristics discussed.
Hydroxyl stretching vibration in 2,6-dimethyl- and 2,6-dichloro-4-substituted phenols
Authors: Leary Gordon
Published: May 2006

The infrared frequencies and apparent half band widths of the O—H stretching band of a series of 2,6-dimethyl-4-substituted phenols and a series of 2,6-dichloro-4-substituted phenols have been measured in carbon tetrachloride solution. The slopes of the Hammett plots for the frequencies and half band widths of both these series are compared with those calculated from published data for 2,6-di-t-butyl-4-substituted phenols and 3- or 4-substituted phenols. Significant differences are found in ρ obtained from the frequency data for the four series. The 2,6-dimethyl-4-substituted phenols, unlike the unhindered phenols, are found to parallel the 2,6-di-t-butyl-4-substituted phenols in having a negative ρ for the frequency data and a negative ρ for the half band width correlation. It is concluded that the negative ρ from the half band widths of 2,6-di-t-butyl-4-substituted phenols is primarily a result of electronic rather than steric factors.
Fischer indole synthesis. The reaction of N′-alkyl-2,6-dialkylphenylhydrazines with cyclohexanone
Authors: Bajwa G. S. , Brown R. K.
Published: May 2006

Condensation of N′-methyl-2,6-dimethylphenylhydrazine with cyclohexanone in refluxing benzene gives 8,9-dimethyl-1,2,3,4-tetrahydrocarbazole along with water and ammonia. Yields of the 8,9-dimethyl-1,2,3,4-tetrahydrocarbazole are improved and general decomposition in the reaction mixture minimized if the hydrazine hydrochloride is used. In this case, however, the ammonia is obtained as ammonium chloride contaminated with ~6% of methylammonium chloride. N′-Ethyl-2,6-dimethylphenylhydrazine hydrochloride and N′-methyl-2,6-diethylphenylhydrazine hydrochloride condense with cyclohexanone to give 9-ethyl-8-methyl-1,2,3,4-tetrahydrocarbazole and 8-ethyl-9-methyl-1,2,3,4-tetrahydrocarbazole respectively along with ammonium chloride contaminated with a very small amount of ethylammonium chloride and methylammonium chloride respectively.The results are interpreted in terms of the formation first of the intermediate enamine then the dienone–imine.
Etude par diffusion de la lumière de la polydispersité résiduelle des polymères fractionnés
Authors: Ahad Elie , Prud'homme Jacques , Sicotte Yvon
Published: May 2006

The general trend of the theoretical results obtained by Tung on simulated fractionations is verified experimentally, showing that the sharpness of the fractions and the variation of the sharpness in the different fractions of a given fractionation are very much dependent on the fractionation conditions and especially on the polymer starting concentration. For very low starting concentration, the middle fractions can be considered as being monodisperse as far as polydispersity detection by light scattering is concerned. The ratio [Formula: see text] for these fractions can be used as a reference for polydispersity characterization of other samples of the same polymer. The comparison of this ratio to the same ratio obtained on a polydisperse sample yields [Formula: see text]. Results obtained in this way for a moderately sharp fractionation are in good accord with the theoretical predictions of Tung.
Kinetics of disproportionation of chlorous acid
Authors: Hong C. C. , Rapson W. H.
Published: May 2006

A mechanism involving HOCl, Cl—ClO2, and Cl2 as intermediates is proposed for the disproportionation of chlorous acid. In the absence of chloride, the reaction is controlled by two simultaneous processes, 2HClO2 → H+ + HOCl + ClO3− and HClO2 + ClO2− → HOCl + ClO3−. Chloride has a catalytic effect and an inhibiting effect as well on the formation of chlorine dioxide. The initial reaction rate passes through a minimum at a certain concentration of chloride at low acidities, which can be interpreted by the postulated mechanism. Under chloride catalysis, the reaction is controlled by the process H+ + Cl− + HClO2 → 2HOCl.
Vapor–liquid equilibrium studies of n-propanol–n-decanol mixtures
Authors: Singh Jaswant , Benson G. C.
Published: May 2006

Static vapor pressure measurements were made on mixtures of n-propanol with n-decanol over the temperature range 20–50 °C. From the results, the molar excess Gibbs free energies were calculated. The applicability of the principle of congruence to these values and to similar data published previously for methanol–decanol and ethanol–decanol systems was examined.
Association of perchlorate, fluoroborate, and fluorophosphate ions with complexions of palladium and platinum
Authors: Westland A. D. , Pluščec J.
Published: May 2006

Perchlorate, tetrafluoroborate, and hexafluorophosphate salts containing the ions (PhSC3H4SPh)2M2+ where M = Pd or Pt are extensively associated as 1:1 electrolytes in nitromethane. Association is preceded by loss of one of the ligand molecules.
Radiolysis of methylcyclopentane. II. Effects of benzene and 1,3-cyclohexadiene in the liquid phase
Authors: Stover E. Diane , Freeman Gordon R.
Published: May 2006

The inhibiting effects of benzene and of 1,3-cyclohexadiene (CHD) on the formation of hydrogen during the radiolysis of methylcyclopentane (MCP) have been analyzed according to the nonhomogeneous kinetics of charge scavenging. The results are consistent with the following suggestions: CHD is an efficient scavenger of electrons; benzene is not an efficient scavenger of electrons but it may scavenge positive ions. These reactions offer alternatives to the hydrogen atom scavenging mechanism that has often been postulated in the past. They can decrease the hydrogen yield from MCP by 20 g units (based upon the energy absorbed only in MCP). In addition to the above scavenging mechanisms, which occur at relatively low solute concentrations (~ 1 mole %), benzene and CHD can each take part in a less efficient hydrogen inhibition reaction that can decrease g(H2) by another 1.6 units. This confirms the earlier suggestion (J. Chem. Phys. 33, 71 (I960)) that two different, inhibitable hydrogen forming processes occur during the radiolysis of saturated hydrocarbons.The yields of other products are also reported.
Group vibrations and the vibrational analysis of molecules containing methylene groups. Part I. The basic equations and the application of the method to methylene dichloride and cyclopropane
Authors: Freeman J. M. , Henshall T.
Published: May 2006

The vibrations of the methylene group first considered by King have been reexamined; and the group factorization procedure previously applied to molecules containing methyl groups has now been extended to molecules containing methylene groups. The vibrational analysis of such molecules can be simplified by factoring from the secular determinant those frequencies that are characteristic of the symmetric and antisymmetric CH2 stretching, and the [Formula: see text] angle bending modes. Corrections are then applied to the G and F matrices to account for the interactions with the molecular framework of the CH2 'rocking', and [Formula: see text] angle deformation modes, where the atoms X may form part of a ring system.
Crystal structures of RuSe2, OsSe2, PtAs2, and α-NiAs2
Authors: Stassen W. N. , Heyding R. D.
Published: May 2006

The atom positions in RuSe2, OsSe2, PtAs2, and α-NiAs2 have been determined from X-ray powder diffraction data. In the pyrite-type compounds (Pa3), the metal atoms are in 4(a), the face-centered positions, and the nonmetal atoms in 8(c), with x = 0.381 ± 3 (RuSe2, a = 5.935 Å); x = 0.382 ± 4 (OsSe2, a = 5.946 Å); and x = 0.385 ± 4 (PtAs2, a = 5.967 Å).In orthorhombic α-NiAs2 (Pbca, a = 5.770, b = 5.838, c = 11.419 Å), the atom positions are[Formula: see text]As in the marcasite and pyrite structures, the nonmetal atoms in α-NiAs2 are paired, and the metal atoms have six nearest nonmetal neighbors at the corners of a distorted octahedron. Between metal atom layers these octahedra are coordinated alternately by corner sharing only, as in the pyrite lattice, and by a combination of corner and edge sharing, as in the marcasite lattice. The mean Ni—As distance is 2.38 Å, with minimum and maximum distances of 2.25 and 2.46 Å. The As—As distance is 2.46 Å, and the shortest Ni—Ni distance is 3.72 Å.
Thermal rearrangement of α,β- to β,γ-unsaturated esters. Evidence for a 1,5-hydrogen transfer mechanism
Authors: McGreer Donald E. , Chiu Norman W. K.
Published: May 2006

Methyl cis-4-methyl-2-pentenoate (1) has been found to rearrange at 252 °C by a simple first-order and presumably unimolecular mechanism to methyl 4-methyl-3-pentenoate (3) with a rate constant k of 4.28 × 10−5 s−1. The heat of activation ΔH†, was determined to be 37.5 ± 2 kcal/mole and the entropy of activation, ΔS†, was determined to be −8.2 ± 4 e.u. These activation parameters and the steric requirements of the reaction support a mechanism involving a cyclic 1,5-transfer of hydrogen. Studies on the isomerization of methyl cis-2-pentenoate, methyl cis-2,4-dimethyl-2-pentenoate, and methyl cis-2-methyl-2-pentenoate to the corresponding 3-pentenoates suggest that the 1,5-hydrogen transfer mechanism could well be general for the equilibration of α,β- and β,γ-unsaturated esters.An isopropyl group cis to a methyl or a carbomethoxy group on a double bond is shown by nuclear magnetic resonance to prefer a conformation with the methyls of the isopropyl group held away from the methyl or carbomethoxy group. A cis hydrogen does not restrict the conformation of the isopropyl group.
Reaction of chloral with naphthalene, and the synthesis of α-methoxynaphthylacetic acids from naphthyl(trichloromethyl)carbinols
Authors: Reeve Wilkins , Hoffsommer John C. , Aluotto Patrick F.
Published: May 2006

From the Friedel–Crafts reaction of chloral and naphthalene, others have reported the isolation of only 2-naphthyl(trichloromethyl)carbinol. Our reexamination of this reaction has shown that a mixture of 1- and 2-naphthyl(trichloromethyl)carbinols is obtained and that 80 to 90% of the product consists of the 1-naphthyl(trichloromethyl)carbinol. The 1- and 2-naphthyl(trichloromethyl)carbinols, their acetates, and their methyl ethers differ in their nuclear magnetic resonance (n.m.r.) spectra in that the signal of the α-hydrogen of the side chain of the 1-naphthyl isomer always occurs 0.8 p.p.m. downfield compared to the signal of the α-hydrogen of the corresponding 2-naphthyl isomer. This is because the α-hydrogens in the 1-naphthyl series of these compounds are in the region between the 1- and 8-positions of the naphthalene ring and subject to the ring currents of both benzenoid rings.The mixture of crude naphthyl(trichloromethyl)carbinols was converted to the mixture of α-methoxynaphthylacetic acids, and these were separated. A small amount of α,α′-dimethoxy-1,5-naphthalenediacetic acid was also obtained, demonstrating that a certain amount of 1,5-substitution occurred in the Friedel–Crafts reaction of naphthalene and chloral.
Synthesis and chemistry of 1-methyl-3-imino-4-hydroxy-4-phenyl-6-chloro-1,2,3,4-tetrahydroquinoline-2-one
Authors: Podesva C. , Vagi K. , Solomon C.
Published: May 2006

Reaction between 2-(N-methyl)dichloroacetamido-5-chlorobenzophenone and aqueous ammonia yields 1-methyl-3-ammo-3,4-dihydroxy-4-phenyl-6-chloro-1,2,3,4-tetrahydroquinoline-2-one which dehydrates readily to give the title compound. Structural proof of this substance is reported and several of its transformation products are described.
Anomalous reaction products from the alkylation of the disodium adduct of benzophenone anil
Authors: Smith James G.
Published: May 2006

Treatment of the disodium adduct of benzophenone anil with isopropyl bromide produced substantial amounts of a by-product as well as the previously reported product, 2-methyl-N,1,1-triphenylpropylamine. This by-product is shown to be N(o-isopropylbenzhydryl)aniline, formed by alkylation of the adduct on the aromatic ring.The structural proof relies both upon the synthesis of the unknown amine and upon the oxidation of the unknown amine to o-isopropylbenzophenone.
Synthesis of oxytocin using the solid phase technique
Authors: Ives D. A. J.
Published: May 2006

This communication reports the synthesis of oxytocin using the Merrifield solid phase technique. For the synthesis both the o-nitrophenyl sulfenyl and t-butyloxycarbonyl blocking groups were used for masking the amino function. The oxytocin precursor obtained gave the same yield of hormone when subjected to the usual procedures as that obtained from a nonapeptide synthesized by conventional methods.
Electron spin resonance study of the interaction of tert-butyl hydroperoxide with zinc oxide
Authors: Codell Maurice , Gisser Henry , Iyengar R. D.
Published: May 2006

The complexity of the electron spin resonance signal, appearing at g = 1.96 on ZnO vacuum outgassed at higher temperatures, has been examined by adsorption of tertiary butyl hydroperoxide (TBHP). Two individual signals with g values 1.961 and 1.965 observed following TBHP adsorption have been attributed to Zn+ ions and oxygen vacancies with trapped electrons.
Lapachol
Authors: Pettit George R. , Houghton Leonard E.
Published: May 2006

A practical total synthesis of hydroxyhydrolapachol and lapachol has been summarized.
Synthesis of 2-amino-2-deoxy-D-talose and 2-amino-2-deoxy-D-galactose
Authors: Perry M. B. , Webb Ann C.
Published: May 2006

Treatment of D-lyxose with nitromethane in the presence of sodium methoxide gave 1-deoxy-1-nitro-D-galactitol which, after conversion to 2,3,4,5,6-penta-O-acetyl-1-deoxy-1-nitro-D-galactitol, reacted with saturated methanolic ammonia solution to yield 2-acetamido-1,2-dideoxy-1-nitro-D-talitol and 2-acetamido-1,2-dideoxy-1-nitro-D-galactitol. 2-Acetamido-1,2-dideoxy-1-nitro-D-talitol and 2-acetamido-1,2-dideoxy-1-nitro-D-galactitol were converted by a modified Nef reaction to 2-acetamido-2-deoxy-D-talose and 2-acetamido-2-deoxy-D-galactose which on hydrolysis with hydrochloric acid afforded 2-amino-2-deoxy-D-talose hydrochloride and 2-amino-2-deoxy-D-galactose hydrochloride. The properties and derivatives of the aminoglycoses are described.
Proton magnetic resonance spectra of some aromatic amines and derived amides
Authors: Brown R. F. C. , Radom L. , Sternhell S. , Rae I. D.
Published: May 2006

The chemical shifts of ring protons in substituted anilines, N-methylanilines, some heterocyclic amines, and their derived acetamides and 4′-bromobenzamides are reported. The magnitude of the downfield shift accompanying acylation is related to the preferred configuration of the amide.
Investigations on steroids. XXXIX. 14,19-Dihydroxy-14β-progesterone and related compounds
Authors: Gupta Virendra N. , Ehrenstein Maximilian
Published: May 2006

Strophanthidol (1) was converted into 3β,19,21-triacetoxy-5,14-dihydroxy-5β,14β-pregnan-20-one (7) which by treatment with methylmagnesium bromide gave a mixture of the two C-20 epimers of 3β,5,14,19,20,21-hexahydroxy-bisnor-5β,14β-cholane (8). Oxidation of 8 with sodium periodate yielded the amorphous 3β,5,14,19-tetrahydroxy-5β,14β-pregnan-20-one (9) which was characterized as the crystalline 3,19-diacetate (10). Selective oxidation of 9 with N-bromoacetamide, followed by dehydration of the reaction product 11 gave 14,19-dihydroxy-14β-progesterone (12) which was characterized as the 19-monoacetate (13).Compound 12 was found to be devoid of progestational and antiprogestational activity.
Tetrahydropyranyl protecting group. I. Tetrahydropyran-2-yl isocyanate
Authors: Horning D. E. , Muchowski J. M.
Published: May 2006

It is shown that monoalkyl and unsymmetrical dialkyl ureas, and alkyl carbamates, are preparable via a two-step sequence involving tetrahydropyran-2-yl isocyanate, and a primary or secondary amine, or an alcohol, respectively.
Hydroboration of cyclic allenes with disiamylborane
Authors: Sethi D. S. , Joshi G. C. , Devaprabhakara D.
Published: May 2006

It has been shown that 1,2-cyclononadiene and 1,2-cyclotridecadiene undergo 78 and 100% hydroboration respectively, with disiamylborane. 1,2-Cyclononadiene gave products which represented 83% attack of boron at the central carbon atom and 17% attack at the terminal carbon atom. 1,2-Cyclotridecadiene gave 62% central carbon attack and 38% terminal carbon attack. The reactivity and selectivity may be explained mainly in terms of steric effects on a four-centered transition state.
Nuclear magnetic resonance spectra of oriented 4-spin systems with C2v symmetry (AA′BB′). The spectrum of thiophene
Authors: Diehl P. , Khetrapal C. L. , Lienhard U.
Published: May 2006

The general Hamiltonian for the nuclear magnetic resonance (n.m.r.) spectra of oriented 4-spin systems with C2v symmetry of the type (AA′BB′) is reported. The system can be discussed analytically, if only the direct coupling between the various nuclei is considered. The expressions for transition frequencies and intensities for such a case are given.The proton spectrum of thiophene in the nematic phase of p,p′-di-n-hexyloxyazoxybenzene has been analyzed. The ratios of the various interproton distances are determined.
Studies on complex compounds. V. Coordination compounds of mercury and biologically active amines
Authors: Misra C. H. , Parmar Surendra S. , Shukla S. N.
Published: May 2006

Five mercury complexes were synthesized by condensation of mercuric chloride with different biologically active amines. In the present study D-amphetamine, L-amphetamine, DL-amphetamine, methyl-amphetamine, ephedrine, and tyramine were used where a stereoisomeric effect was observed during the formation of the mercury complexes. The complex compound synthesized from DL-amphetamine was found to be a mixture of the mercury complexes of D-amphetamine and L-amphetamine, and the difference in their solubilities was utilized for their separation. The estimation of the carbon, hydrogen, and nitrogen content, the determination of the amount of chlorine and mercury, and measurements of the infrared absorption spectra at 700–3500 cm−1 indicated the ratio of 2:1 for amine to mercury in these coordination compounds. Further characterization of these mercury complexes was done by ultraviolet absorption spectra and conductance measurements.
Some reactions of pentafluorothiophenol. Preparation of some pentafluoro-phenylthio metal derivatives
Authors: Peach M. E.
Published: May 2006

The new compounds M(SC6F5), where M = Cs, Tl, Cu, Au, and Ph3Pb; M(SC6F5)2, where M = Pb, Cd, Hg, Ni, and Pt; M(SC6F5)3, where M = As or Bi; and Sn(SC6F5)4 have been prepared from pentafluorothiophenol and metal ions in aqueous solution. Zn(SC6F5)2 has been prepared from zinc oxide and pentafluorothiophenol in methanol. The compounds have been characterized, and their infrared spectra and 1H and 19F nuclear magnetic resonance spectra examined.Some of the reducing properties of pentafluorothiophenol and its polymerization have been studied.
Phase equilibria in the system: silver tetrafluoroborate – 1-pentene
Authors: Quinn H. W. , VanGilder R. L.
Published: May 2006

A determination has been made of the phase diagram within the region 0.40 to 0.85 mole fraction of 1-pentene. Complexes with 1:2 and 1:3 stoichiometry melting congruently at 43.3 and −30.3 °C respectively have been observed. Evidence was also obtained for the existence of a 1:1 complex stable only in the solid state below about −10 °C.
Effect of counter-ion in the anionic polymerization of styrene in cyclohexane
Authors: Roovers J. E. L. , Bywater S.
Published: May 2006

The propagation reaction in the anionic polymerization of styrene has been studied in cyclohexane with the counter-ions: K, Rb, and Cs. Some association of the ion-pairs was found with K. Absolute propagation rate constants were determined in the three cases. Some experiments were carried out in benzene–cyclohexane mixtures to check that the results were consistent with those previously observed in benzene.
Solubility in the potassium stannate – potassium hydroxide – water system at 0 to 95.0 °C
Authors: Rosenblum P.
Published: May 2006

Solubilities and phase relations have been determined in the K2Sn(OH)6–KOH–H2O system between 0 and 95.0 °C. The isotherms consist of only one major solubility branch, that of K2Sn(OH)6, while the solubility branch of KOH is indistinguishable, since the isothermal invariant point is extremely close to the solubility of potassium hydroxide. Solid phases have been determined by Schreinemakers' method and checked with the polarizing microscope.
Model reactions for a synthesis of streptamine based on the diamination of nitrocyclitol acetates
Authors: Baer Hans H. , Wang Margaret C. T.
Published: May 2006

Treatment of trans,trans-2-nitro-1,3-cyclohexanediol diacetate with ammonia followed by acetylation gives trans,trans 1,3-diacetamido-2-nitrocyclohexane (4). Catalytic hydrogenation of 4 and subsequent acetylation lead to trans,trans-2,6-diacetamidocyclohexylamine (5) and trans,trans-1,2,3-triacetamidocyclohexane (6), respectively. Permanganate oxidation of 4 affords cis-2,6-diacetamidocyclohexanone (7; 2,4-dinitrophenylhydrazone, 8). Sodium borohydride reduction of 7 produces trans,trans-2,6-diacetamidocyclohexanol (9; O-acetate, 10).
A(1,3) interaction and conformational energy of axial–axial 1,3-dimethyl interaction
Authors: Chow Y. L. , Colón C. J. , Tam J. N. S.
Published: May 2006

A(1,3) type strain was demonstrated directly from the nuclear magnetic resonance studies of the acyl and nitroso derivatives of 2-methylpiperidine (2 series) and 2,6-cis-dimethylpiperidine (1 series). In these two series, the bulky 2-methyl groups are forced to assume the axial conformation due to a severe A(1,3) interaction in the equatorial conformation. The free energy of activation (ΔG*) for the internal rotation around the N—C and N—N bonds in 1a–1g was determined. The comparison of these (ΔG*) values with those of the corresponding derivatives of dimethylamine indicates the decreases are in the range of 3.6–4.7 kcal/mole which is in fair agreement with the conformational energy of 1,3-diaxial CH3/CH3 interaction. An argument was presented to show that this interaction energy corresponds to the decrease of ΔG* in 1a-1g.
Nuclear magnetic resonance and mass spectral properties of 5-aryltetrazoles
Authors: Fraser Robert R. , Haque K. E.
Published: May 2006

The nuclear magnetic resonance and mass spectral behavior of 5-phenyltetrazole, 5-p-nitrophenyl-tetrazole and the 1-methyl and 2-methyl derivatives of each have been determined. Characteristic differences between the spectra of the 1-methyl and 2-methyl isomers have been noted and found to be useful for the purpose of structural assignments. The synthesis of 1- and 2-methyl-5-phenyltetrazole containing 47.5 % of 15N in the 1- and 4-positions of the tetrazole ring aided interpretation of the mass spectra and also allowed measurement of a geminal and a vicinal 15N—H coupling constant.
Synthesis of branched-chain sugars by the wittig reaction
Authors: Rosenthal Alex , Catsoulacos P.
Published: May 2006

The Wittig reaction has been extended to yield a 2,3-dideoxy branched-chain sugar from 2-deoxy-3-ketose 3. Improvements in the procedures for the preparation of ketose (3) are also described.
Studies in solvolysis. Part I. The neutral hydrolysis of some alkyl trifluoroacetates in water and deuterium oxide
Authors: Winter June G. , Scott J. M. W.
Published: May 2006

The temperature dependence of the rates of neutral hydrolysis of a series of alkyl trifluoroacetates (CF3COOR; R = methyl, ethyl, s-propyl, t-butyl) has been determined in both light and heavy water. From these studies the thermodynamic parameters (ΔH≠, ΔS≠) which characterize the activation process have been calculated. Sufficient rate data have been obtained in the case of the ethyl ester to calculate the heat capacity of activation (ΔCP≠) for the hydrolysis of this compound in light water. Both the entropies and enthalpies of activation as well as the solvent isotope effects are consistent with the proposal that the primary and secondary esters react by an acyl–oxygen BAc2 mechanism, in contrast to the tertiary ester, which appears to react either by a carbonium ion (SN1) process or by a route which combines both the BAc2 and SN1 paths.
Photolytic hydration of cyanamides
Authors: Chow Y. L. , Haque K. E.
Published: May 2006

N-Cyanopiperidines (1 and 2) have been shown to possess a n → π* transition band in the vicinity of 260 mμ and, in the presence of a dilute acid, undergo photolytic reactions leading to hydration products (3 and 4). The fact that the reaction can be sensitized by acetophenone demonstrates that 1 reacts through a triplet state. ET is about 76 kcal/mole. Increasing the water content in the photolysis medium reduced the yield of the hydration product.
Free radicals by mass spectrometry. XXXIX. Primary steps in the mercury-photosensitized decompositions of methyl and ethyl mercaptan
Authors: Yamashita S. , Lossing F. P.
Published: May 2006

The reaction between Hg(3P1) atoms and methyl mercaptan at 55° is mainly H-atom removal from sulfur[Formula: see text]with a minor participation (~10%) of C—S bond rupture[Formula: see text]Ethyl mercaptan dissociates by two main processes[Formula: see text]Some evidence was found for a small amount of dissociation by C—C bond rupture. No C—H bond rupture in either compound could be detected.
The transmission of polar effects. Part VI. The ionization of ortho-substituted benzoic acids
Authors: Bowden Keith , Manser G. E.
Published: May 2006

The pKa values of a series of ortho-substituted benzoic acids in 50% ethanol–water have been determined. The effect of ortho-substitution on the ionization of benzoic acid in this and other solvents has been correlated by a linear free energy relation. The reaction constants found are compared with those for the meta/para-substituted benzoic acids. While those for the former system are insensitive to changes in the medium, the latter vary considerably. It is suggested that this is due to transmission by the field effect passing almost entirely through the molecular cavity for ortho-substituents.
Electric dipole moments of ortho-, meta-, para-, and penta-fluorostyrene molecules
Authors: Bock E. , Iwacha D.
Published: May 2006

The dipole moments of ortho-, meta-, para-, and penta-fluorostyrene were determined in dilute benzene solution at 25 °C. It was found that the magnitude of the molecular dipole moment depends on the position of the fluorine atom in the benzene ring.
Isomerization of nitrito- to nitro-pentakis(methylamine)cobalt(III) cation
Authors: Parris M. , Majid L.
Published: May 2006

The preparations of these two linkage isomers are described. In aqueous solution the isomerization of nitrito to nitro is very similar to that for the parent pentaamine while in the solid phase it is retarded.
Chemistry and pharmacology of some benzo[1,2]cyclohepta[3,4,5-d,e]isoquinolines
Authors: Humber Leslie G. , Davis M. A. , Beaulieu G. , Charest M.-P.
Published: May 2006

The chemistry of 1,2,3,7,8,12b-hexahydro-, 1,7,8,12b-tetrahydro-, and 7,8-dihydrobenzo[1,2]cyclohepta[3,4,5-d,e]isoquinolines has been investigated, leading to the synthesis of a wide variety of derivatives bearing substituents in the 2- and 3-position. Also, the reactions of 1,7,8,12b-tetrahydrobenzo[1,2]cyclohepta[3,4,5-d,e]isoquinoline with 1-buten-3-one, methyl mercaptoacetate, and 3-mercaptopropionic acid have yielded representatives of three novel pentacyclic systems; benzo[4,5]cyclohepta[1,2,3-g,h]-benzo[a]quinolizine, benzo[1,2]cyclohepta[3,4,5-d,e]thiazolo[2,3-a]isoquinoline, and benzo[1,2]cyclohepta[3,4,5-d,e]-1,3-thiazino[2,3-a]isoquinoline. The central nervous system and cardiovascular pharmacology of the compounds have been investigated and the results are presented.
Determination of —SH and —SS— groups in proteins. I. A reassessment of the use of methylmercuric iodide
Authors: Forbes W. F. , Hamlin C. R.
Published: May 2006

Amperometric titration with methylmercuric iodide was found to be unsatisfactory for the quantitative determination of —SH and —SS— values in several soluble proteins. It is concluded that the "high reactivity" of the mercurial has previously been overemphasized. Consistent values can, however, be obtained by permitting protein samples to react with an excess of the mercurial, for about 100 h, followed by the polarographic estimation of the remaining reagent. Contrary to general belief, this procedure was found to be more precise than amperometric titration, and, if appropriate precautions are taken, it is applicable to considerably smaller amounts (<0.5 μmole —SH or —SS—) of either soluble or insoluble protein. The necessary experimental procedure is described and results are reported for several proteins. For the compounds studied, methylmercuric iodide did not react at non-sulfhydryl sites, and did not additionally bind to the mercaptides formed; there was no indication of disulfide bond cleavage, despite the long reaction times used.
Reaction of acetylenic hydrocarbons with α,β-unsaturated ketones in tetrahydrofuran in the presence of lithium naphthalene
Authors: Suga Kyoichi , Watanabe Shoji , Suzuki Toshimitsu
Published: May 2006

Lithium naphthalene reacts easily with terminal acetylenic hydrocarbons, such as acetylene, methyl-acetylene, or phenylacetylene, to give the corresponding lithium compounds quantitatively. The reaction of these lithium compounds with α,β-unsaturated ketones gives the corresponding acetylenic carbinols in a good yield under mild conditions.