bluuebunny/crossref_metadata_2025 huggingface dataset:
Models for the Interaction of Nitrogen with Transition Metals. Part III. Preparation and Properties of some Cationic Arylazo Complexes of Iron
Authors: Fisher D. R. , Sutton D.
Published: May 2006

Fe(CO)3(PPh3)2 reacts with p-substituted aryl diazonium tetrafluoroborates to yield the compounds [Fe(CO)2(PPh3)2(N2C6H4X)]BF4 (where X = F, Cl, Br, H, NO2, OCH3, and OH but not NEt2). The complex cation displays properties consistent with replacement of an equatorial CO ligand in Fe(CO)3(PPh3)2 by the more effective π-acceptor ligand [N2C6H4X]+ analogous to NO+. A very strong band at ca. 1720 cm−1 in the i.r. spectrum due to v(N2) has been identified by 15N isotopic substitution. This value is much higher than for most other arylazo complexes yet prepared and the azo group resists catalytic hydrogenation. A number of spectroscopic measurements are reported, including unusually small quadrupole splitting effects in the Mössbauer spectra.
Iridoids of Mentzelia decapetala (Pursh). II. Decaloside
Authors: Danielson Terry John , Hawes Edward Miles , Bliss Carman Arthur
Published: May 2006

Decaloside (1), a minor component of Mentzelia decapetala (Loasaceae) has been isolated and characterized as 1S,4aS,5R,7aR-1-O-β-D-glucosyl-5-hydroxy-1,4a,5,7a-tetrahydro-4-hydroxymethylcyclo-penta(c)pyran.
Acenaphthene III. Coupling Reactions. The Preparation of 4,4′-Dinaphthalic Anhydride and 4′,1-Naphthylnaphthalic Anhydride
Authors: Jones Louis A. , Watson Ronald
Published: May 2006

The syntheses of the previously unknown 4,4′-dinaphthalic anhydride (4) and 4′, l-naphthylnaphthalic anhydride (5) is reported. The vinylic bromination of 5-(1,-3,4-dihydronaphthyl)acenaphthene (11) is also described.
The Master Equation for the Dissociation of a Dilute Diatomic Gas IX. Rotation–Vibration Relaxation Times
Authors: Kamaratos E. , Pritchard H. O.
Published: May 2006

The relationships between individual rotational or vibrational transition probabilities and the eigenvalues of the 172nd order relaxation matrix describing the rotation–vibration–dissociation coupling of ortho-hydrogen are explored numerically. The simple proportionality between certain transition probabilities and certain eigenvalues, which was found previously in the vibration–dissociation coupling case, breaks down. However, it is shown that at 2000°K the second smallest eigenvalue of the relaxation matrix (dn−2), hitherto regarded as determining the "vibrational" relaxation time, is related more to the transition probability assigned to the largest rotational gap which lies in the first (ν = 0 ↔ ν = 1) vibrational gap, i.e. to the transition ν = 0, J = 5 ↔ ν = 0, J = 7, than to anything else; this clearly supports an earlier suggestion that the transient which immediately precedes dissociation in a shock wave has to be regarded as a rotation–vibration relaxation time rather than a vibrational relaxation time. It is suggested that the Lambert–Salter relationships can be rationalized on this assumption.An analysis is then made of the energy uptake associated with each eigenvalue at three temperatures. At 500°K, the greatest energy increment is associated with two eigenvalues (dn−13 and dn−24) and can be characterized as essentially a rotational relaxation: the calculations confirm that the observed rotational relaxation time should first decrease and then increase with increasing temperature, as was recently found to be the case experimentally. At 2000°K, large energy increments are associated with several eigenvalues between dn−2 and dn−14, and at 5000°K, with most of the eigenvalues dn−2 to dn−23; thus, the higher the temperature, the more complex is the (T–VR) rotation–vibration relaxation. Further, relaxation times for the same temperature measured by ultrasonic and shock-wave techniques need not agree.
Formation of New Tetradentate Schiff Base Metal Chelates
Authors: Malek Abdul , Fresco James M.
Published: May 2006

Condensation products of o-aminophenol, N-substituted-o-aminophenols, and 8-amino-1-naphthol with α-diketones have been compared. The basis for the lack of reactivity of these products to yield Schiff base chelates for the cases where the parent diketone is different from glyoxal was examined. Steric factors alone did not appear to influence the reaction.
Crystal Structure and Phase Transformations of Sodium Diarsenate, Na4As2O7
Authors: Leung Kiang Y. , Calvo Crispin
Published: May 2006

Sodium diarsenate at room temperature is monoclinic with lattice parameters a = 5.969(1), b = 10.126(1), c = 12.272(3) Å and β = 92.87(2)°. There are four formula units per cell with space group C2/c. The structure was refined by full-matrix least-squares to a final R value of 0.027 utilizing 1157 reflections measured on a Syntex [Formula: see text] automatic diffractometer. The anion, consisting of two AsO4 tetrahedra sharing a common oxygen atom, with a bridging angle of 123.5° at that oxygen atom, lies on a two-fold axis. The bridging As—O bond lengths are 1.783 Å and the average terminal As—O bond length is 1.658 Å uncorrected for thermal motion. Both Na ions show fivefold coordination to oxygen atoms. One of these sodium ions has a long interaction (2.852 Å) with the bridging oxygen atom of the anion. Na4As2O7 undergoes a series of phase transformations between room temperature and 220 °C, and a further major transformation near 680 °C.
The Pulse Radiolysis of Dimethylsulfoxide and Binary Mixtures with Water
Authors: Cooper T. K. , Walker D. C. , Gillis H. A. , Klassen N. V.
Published: May 2006

The simultaneous interaction of solvated electrons with strongly solvating water molecules and weakly solvating dimethylsulfoxide (DMSO) molecules has been studied by pulse radiolysis. In all DMSO/H2O mixtures investigated the solvated electrons have a single absorption band with a maximum intermediate between that of pure DMSO (λmax > 1500 nm) and that of water (λmax = 720 nm). There is a nearly linear relationship between the photon energy of λmax and the bulk dielectric constant, indicating that the optical properties of solvated electrons in the mixtures are not dominated by the water. A minimum is observed in the variation of Gεmax with DMSO/H2O composition which may be associated with intermolecular structure. In mixtures containing > 0.2 mole fraction DMSO the solvated electrons have half-lives of 11–18 ns.The radiation produced oxidizing species in DMSO has a half-life of 1–4 µs and an absorption band centered at 600 nm. This species seems to be present in all DMSO/H2O mixtures.Pure DMSO gives a free-ion yield in the range 1.2 to 1.8, as determined separately for the oxidizing and reducing species by bromide and anthracene scavenging experiments respectively. This free-ion yield is in keeping with the dielectric constant of DMSO of 46. The yields in fully deuterated DMSO are ~30% higher than in the protonated material.
Activity Determination of Cobalt in Cobalt–Gold Alloys
Authors: Wang S. S. , Toguri J. M.
Published: May 2006

Activities of cobalt in cobalt–gold liquid alloys from 1250 to 1335 °C were determined by equilibrating the alloy with pure solid CoO under a CO/CO2 gas mixture of known oxygen partial pressure. The cobalt activities were calculated from the cobalt content of the alloys after equilibration. The activities of gold were calculated by Gibbs–Duhem integration. In the present study, both activities showed positive deviations from ideality. In the terminal region, the cobalt–gold system was found to behave as a regular solution. The temperature effect on the activities was found to be negligible.
Hydrated Electrons Formed in the Flash Photolysis of Ag° and Tl°
Authors: Basco Norman , Vidyarthi Sunil K. , Walker David C.
Published: May 2006

The transient species Ag0, formed in the reduction of Ag+ by hydrated electrons, may be photodissociated to eaq− again by light in the absorption band of Ag0 centered at ~315 nm.[Formula: see text]It suggests that this band is a charge-transfer-to-solvent band. The photon energy threshold for photoionization of Ag0 (3.0 eV) is substantially smaller than the vacuum photoelectric work function of silver metal (4.5 eV). Analogous results were obtained in solutions of Tl+ indicating that Tl0 may also yield eaq− on photolysis at ~300 nm. The experiments utilized a double flash photolysis technique, in which hydrated electrons were produced by u.v. photolysis of SO42− in the first flash, reacted with Ag+ or Tl+ to give the short-lived intermediates Ag0 (lifetime ~60 μs) and T10 (lifetime < 20 μs) which were photolyzed by a second flash containing light in a restricted wavelength range.
The Fluorescence of CS2 Vapor
Authors: Lambert C. , Kimbell G. H.
Published: May 2006

The fluorescence of carbon disulfide vapor was measured as a function of both wavelength of excitation and wavelength of fluorescence. It was found necessary to invoke a vibrational cascade model in order to account for the observations. Vibrational deactivation occurred on every collision, whereas electronic deactivation was found to require about ten collisions.The quenching by the foreign gases Ar, N2, O2, CO2, COS, SF6, and C3H8 of CS2 fluorescence excited by a wavelength of 320.0 nm was measured and the rate constants computed. The degree of efficiency could be correlated with the complexity of the molecule as determined by its polarizability.
The Observation of Two Different Base-catalyzed Processes Occurring in Directly Observable Carbonium Ion Rearrangements
Authors: Chiu N. W. K. , Sorensen T. S.
Published: May 2006

In aqueous sulfuric acid, cis-1,3,4,5-tetramethylcyclopentenyl cation (1a) has been found to rearrange not only to the trans isomer (1b) but also to 1,2,3,4-tetramethylcyclopentenyl cation (1c). The 1a → 1b and 1a/1b → 1c rearrangements follow H0 with slopes of 0.94 and 0.45 respectively. The 1a → 1b rearrangement involves a neutral intermediate, 1,2,4,5-tetramethylcyclopentadiene, whereas the 1a/1b → 1c rearrangement involves a termolecular or intramolecular push–pull process.
A Synthesis of 2-Acetamido-2,6-dideoxy-D-gulose, 2-Acetamido-2,6-dideoxy-D-idose, and 2,6-Dideoxy-D-xylo-hexose (Boivinose)
Authors: Perry Malcolm B. , Daoust Virginia
Published: May 2006

The base-catalyzed addition of nitromethane to 5-deoxy-D-xylose gave a mixture of 1,6-dideoxy-1-nitro-D -gulitol (2) and 1,6-dideoxy-1-nitro-D-iditol (3) (ca. 1;1) which underwent the Nef reaction to give 6-deoxy-D-gulose and 6-deoxy-D-idose, Acetylation of mixed 2 and 3 afforded the corresponding 2,3,4,5-tetra-O-acetyl-1,6-dideoxy-1-nitro-D-gulitol (4) and 2,3,4,5-tetra-O-acetyl-1,6-dideoxy-1-nitro-D-iditol (5) derivatives which on treatment with methanolic ammonia yielded 2-acetamido-1,2,6-trideoxy-1-nitro-D-gulitol (11) and 2-acetamido-1,2,6-trideoxy-1-nitro-D-iditol (12) (ca. 6:1). Compounds 11 and 12 underwent the modified Nef reaction to give 2-acetamido-2,6-dideoxy-D-gulose (13) and 2-acetamido-2,6-dideoxy-D-idose (14) which were separated by cellulose column chromatography.Compound 4 was converted to 3,4,5-tri-O-acetyl-1,2,6-trideoxy-1-nitro-D-xylo-hex-1-enitol (6) which on catalytic reduction gave 3,4,5-tri-O-acetyl-1,2,6-trideoxy-1-nitro-D-xylo-hexitol (7). Compound 7 underwent the Nef reaction to yield 2,6-dideoxy-D-xylo-hexose (8) (D-boivinose).
Combinatorial Entropy of Mixing for Molecules Differing in Size and Shape
Authors: Lichtenthaler Rüdiger N. , Abrams Denis S. , Prausnitz John M.
Published: May 2006

In reducing experimental vapour–liquid equilibrium data it is common to calculate the Gibbs energy of mixing in excess of that for a solution whose entropy of mixing is given by one of two expressions; ideal entropy or Flory–Huggins entropy. The first of these is proper for a mixture of small molecules of similar size and the second one is proper for a mixture of monomer and chain polymer. This paper considers intermediate cases where there are significant differences in molecular shape as well as size. An expression is derived for the combinatorial entropy of mixing; this expression has Flory's result as the leading term but also contains corrections for molecular bulkiness. The combinatorial entropy of mixing depends on characteristic parameters reflecting both molecular size and shape. Methods are given for simple evaluation of these parameters and illustrations for representative mixtures are presented. In some case, the corrections for bulkiness can be very large.
Quantum Organic Photochemistry. IV. The Photoisomerization of Diimide and Azoalkanes
Authors: Baird N. Colin , Swenson Jerrald R.
Published: May 2006

Potential energy surfaces for the isomerization of diimide and azomethane in the ground, 1(n,π*),3 (n,π*), and 3(π,π*) states have been calculated by ab initio molecular orbital methods. Two mechanisms are considered in detail, the first involving in-plane motion of the substituent group and the second involving twisting about the N—N bond. The first mechanism is preferred for the ground and 3(π,π*) states, whereas the second mechanism is preferred for the (n,π*) states. A significant barrier to rotation is predicted for the 3(π,π*) state. The vibrationally-relaxed (twisted) lowest triplet of diimide is predicted to lie 36 kcal mol−1 above the ground state.
Thermodynamic Properties of Zinc Chloride in Alkali Chloride Melts by Electromotive Force Measurements
Authors: Robertson Ron J. , Kucharski Alfred S.
Published: May 2006

Electromotive force measurements on the ZnCl2–ACl systems where A = K, Rb, and Cs were made using cells of the type[Formula: see text]in the temperature range 450° to 800 °C. The partial molar free energies, enthalpies, and excess entropies have been determined from the temperature dependence of the emf results. These thermodynamic properties exhibit increasing negative departure from ideality as the basicity of the alkali metal salt increases. The results are interpreted in terms of an acid–base reaction and are discussed in relation to current models.
Nuclear Magnetic Resonance Study of Hydrogen Bonding in 1,1,1-Trifluoro-2-hydroxy-4-alkanones
Authors: Kiehlmann Eberhard , Menon B. C. , McGillivray Nora
Published: May 2006

Addition of fluoral at the α-carbon of 3-pentanone, cyclohexanone, 4-methyl-2-pentanone, and acetone gives 1,1,1-trifluoro-2-hydroxy-3-methyl-4-hexanone (1a and b, diastereomers), 2-(1-hydroxy-2,2,2-trifluoroethyl)cyclohexanone (2a and b, diastereomers), 1,1,1-trifluoro-2-hydroxy-6-methyl-4-heptanone (3), and 1,1,1-trifluoro-2-hydroxy-4-pentanone (4), respectively. Hydrogen-bonding studies, based on proton and fluorine n.m.r. measurements, show strong intramolecular [Formula: see text] bonding with relatively weak intermolecular interactions in 1a and 2a, and intermolecular [Formula: see text] bonding in 1b, 2b, 3, and 4.
The Photochemically Produced Ketyl of Perfluorobenzophenone: Electron Spin Resonance Studies of Solvent Effects
Authors: Sargent Frederick Peter , Bailey Marshall Grant
Published: May 2006

The ketyl radical is formed when solutions of perfluorobenzophenone are photolyzed with u.v. light. The radical was identified by electron spin resonance (e.s.r.) studies of the effects of solvent, temperature, chemical exchange, and deuteration on the spectra. Solvent mixtures of cyclohexane and ethanol gave spectra which were very sensitive to the mole fraction of alcohol in the range 0–1%. An equilibrium constant for solvent molecule exchange has been deduced.
Hot-Tube Reactions of Dehydroabietic Acid with Ketene-Producing Reagents. Pyrolysis of the Acid Chloride and Symmetrical and Mixed Anhydride Derivatives of Dehydroabietic Acid
Authors: Severson Ray F. , Schuller Walter H.
Published: May 2006

Dehydroabietic acid (1a) was reacted with diketene, acetic acid, acetic anhydride, isopropenyl acetate, acetyl chloride, and acetone on Vycor rod at 450 °C in a hot tube. Dehydroabietic anhydride (1b) and acetyl dehydroabietate (1c) were pyrolyzed at 450 °C and dehydroabietyl chloride (1d) was pyrolyzed over a temperature range of 290–500 °C. The major olefin products resulting from decarboxylation of the various derivatives were 19-norabieta-4,8,11,13-tetraene (2), 19-norabieta-4(18),8,11,13-tetraene (3), 19-norabieta-3,8,11,13-tetraene (4), and cis-1,10a-dimethyl-7-isopropyl-1,2,3,9,10,10a-hexahydrophenanthrene (5). High conversions to these compounds were obtained. In the presence of the ketene-producing reagents the olefins were oxidized to yield substantial amounts of retene (6), compounds 2 and 5 being the most readily dehydrogenated. The acid isomerization of 2, 3, 4, and 5 was studied using p-toluenesulfonic acid in toluene at 110 °C.
Effect of Solvents on the Quantum Efficiency of Rubrene Electrogenerated Chemiluminescence
Authors: Pighin A.
Published: May 2006

A simple and precise method for measuring the efficiency of electrogenerated chemiluminescence (e.g.c.l.) in terms of photons/(Faradaic electron)(Φcoul) is described and applied to rubrene e.g.c.l. A symmetrical square wave potential having a frequency of 20–1000 Hz was employed to produce the e.g.c.l. The electrogenerated ion radicals were shown to be completely stable at these frequencies; consequently, Φcoul was determined in the absence of side reactions. Change of solvent from N,N-dimethylformamide (DMF) to equivolume benzene-DMF resulted in an increase in Φcoul from 0.67 to 1.21% at 20 Hz. Φcoul decreased with increasing frequency. Varying the electrolyte (tetra-n-butylammonium perchlorate, TBAP) concentration did not affect Φcoul.
The Photochemistry of 2-Cyano-1,4-dihydro-1,4-ethenoanthracene
Authors: Bender Christopher Owen , Burgess Helen Diana
Published: May 2006

The direct photolysis of 2-cyano-1,4-dihydro-1,4-ethenoanthracene (5) yields 8-cyanocycloocta[b]-naphthalene (8, Φ = 0.02) and 1- and 6-cyanonaphtho[2,3-c]tricyclo-[3.3.0.02,8]octa-3,6-diene (6, Φ = 0.30 and 7, Φ = 0.04). The benzophenone sensitized irradiation of 5 yields 6 (Φ = 0.40) and 7 (Φ = 0.04) only. Deuterium labeling studies reveal that 8 derives from an initial 2π + 2π cycloaddition reaction which proceeds with bonding between the vinyl and vinylcyano bridges.
A Low Temperature Infrared Study of Hydrogen Bonding in N-Alkylacetamides
Authors: Bernard-Houplain Marie-Claude , Sandorfy C.
Published: May 2006

The infrared spectra of N-methylacetamide and two other secondary amides were measured in solution at temperatures ranging from 22 to −190 °C in both the fundamental and the overtone regions. At least two hydrogen bonded species are found as association increases with decreasing temperature. The effect of hydrogen bond formation on the anharmonicity of the NH stretching vibration and on the NH stretching – NH bending coupling constant is examined.
The Synthesis, Mössbauer and Infrared Spectra of some Dialkyltin Salts of Phosphorus Oxy-acids
Authors: Chivers T. , Roode J. H. G. Van , Ruddick J. N. R. , Sams J. R.
Published: May 2006

A number of dialkyltin(IV) salts of phosphorus oxy-acids R2Sn(PO2H2)2 (R = CH3, C2H5, n-C4H9), R2SnPO3X (R = CH3, C2H5, n-C4H9, X = H; R = CH3, X = F, OH), and [(CH3)2Sn]3(PO4)2 have been prepared in aqueous solution from the appropriate dialkyltin(IV) dichloride and the sodium salts of phosphorus oxy-acids.Infrared and 119Sn Mössbauer spectra of the dialkyltin dihypophosphites, R2Sn(PO2H2)2, are consistent with hexacoordination for tin with the alkyl groups in trans-octahedral positions and bidentate bridging hypophosphite groups coordinated through oxygens. For the dialkyltin phosphites, R2SnPO3X, polymeric structures with a non-linear R2Sn arrangement are involved, and the magnetic hyperfine Mössbauer spectrum (X = F) is consistent with either distorted trans-octahedral or distorted trigonal bipyramidal structures (with both apical or both equatorial methyl groups). In [(CH3)2Sn]3(PO4)2 the three tin environments are indistinguishable by Mössbauer spectroscopy, but the high value of the asymmetry parameter [Formula: see text] suggests penta- rather than hexacoordination about tin, for which at least one three-coordinate oxygen per formula unit must be invoked.
Evidence Against a Hydrogen Abstraction Mechanism in the Photorearrangement of Azoxybenzene to 2-Hydroxyazobenzene
Authors: Goon David J. W. , Murray N. G. , Schoch Jean-Pierre , Bunce N. J.
Published: May 2006

In an attempt to distinguish between ionic and free radical mechanisms for the photorearrangement of azoxybenzene to 2-hydroxyazobenzene, aromatic azoxycompounds carrying C—H functions ortho to the azoxy linkage have been prepared and irradiated. The failure of these weaker C—H bonds to divert the reaction from its normal course argues against a hydrogen abstraction–hydroxyl transfer mechanism. This conclusion is supported by the observation of a 30-fold increase in quantum yield for 2-hydroxyazobenzene formation on changing from a non-polar to a polar solvent and by the kinetic deuterium isotope effect, which is too small for the primary isotope effect required by the abstraction mechanism. It is concluded that the experimental observations to date may most easily be accommodated in the route originally proposed by Badger and Buttery, where the rearrangement is seen as a substitution by oxygen at the ortho ring carbon.
The Densities, Viscosities, and Diffusion Coefficients of Solutions of Mono-, Di-, and Triethylamine in Water
Authors: Campbell A. N. , Lam S. Y.
Published: May 2006

The densities, relative viscosities, and diffusion coefficients of the binary systems, monoethylamine–water, diethylamine–water, both at 25 °C, and triethylamine–water at 17 °C, slightly below its lower critical solution temperature, were investigated experimentally.Densities were determined with Ostwald–Sprengel type pycnometers and viscosities by means of Cannon and Fenske viscometer. The diffusion coefficients of the amines in aqueous solution were obtained by the Stokes diaphragm cell method. Monoethylamine has the highest diffusion rate. Plotting D vs. c and extrapolating to c = 0 gives an apparent D0 which, for all three amines, is notably smaller than the value given by the Nernst model.
The Radiolysis of Water Vapor at Very High Dose Rates. I. Hydrogen Yields from H2O, H2O–HCl, and H2O–HBr Mixtures
Authors: Boyd A. W. , Willis C. , Miller O. A.
Published: May 2006

The plateau yields of hydrogen from the Febetron radiolysis of mixtures of water vapor with up to 8 mol% of HCl or HBr are G(H2) = 7.9 ± 0.2 and G(H2) = 4.6 ± 0.2 with 1 mol% SF6. These yields are consistent with G(H) = 7.45 in pure water vapor and G(H) = 4.15 in water vapor with SF6. In the Febetron radiolysis of pure water vapor at 2 × 1027 eV g−1 s−1 and densities of ~1 mg ml−1G(H2) = 1.65 + 0.05 from 164 to 190 °C. This yield is reduced to G(H2) = 0.90 ± 0.05 on the addition of 1 mol% SF6. Using a second order equivalent rate constant for the disappearance of the OH radicals in water vapor at 1 mg ml−1 of 2 × 1010 M−1 s−1 these yields are consistent with ate constant values for the reactions H + OH (+H2O) → H2O, OH + OH (+H2O) → H2O2, and H + H (+H2O) → H2, of 1.7 ± 0.1 × 1010 M−1 s−1, 1.5 ± 0.5 × 109M−1 s−1, and 3 ± 1 × 108 M−1 s−1, respectively.
An Ionization Chamber Study of Electron and Ion Decay in Irradiated Ammonia
Authors: McCracken D. R. , Armstrong D. A.
Published: May 2006

Ionization chambers with plane parallel and coaxial electrodes have been used to study the ion and electron concentrations in ammonia subjected to 120 kvp X-ray pulses of 17 and 30 ms duration. Differences in the numbers of positive and negative ions collected on the application of pulses of high voltage imply that free diffusion of electrons to the cell walls occurs in the early part of the X-ray pulse until it is inhibited by the positive ion space charge. Thereafter, positive and negative ions decay at equal rates.The rate constant for the neutralization reaction[Formula: see text]at 1200 Torr of ammonia and 297°K was calculated to be 4.2 ± 1.0 × 10−5 cm3 ion−1 s−1. However, unless extensive precautions are taken to remove electron-attaching impurities reactions between NH4+•nNH3 ions and impurity negative ions are dominant. The results are discussed and compared to other work on electron–ion neutralization reactions.
New Route to Branched-chain Aminodeoxy Sugars by Reaction of Ketoses with Acetonitrile. Synthesis of Methyl 3-C-2′-Aminoethyl-2-deoxy-α-D-arabino-hexopyranoside
Authors: Rosenthal Alex , Schöllnhammer G.
Published: May 2006

Addition of methyl 4,6-O-benzylidene-2-deoxy-α-D-erythro-hexopyranosid-3-ulose (1) to acetonitrile in liquid ammonia at −50 to −60° in the presence of lithium amide gave, in high yield, crystalline methyl 4,6-O-benzylidene-3-C-cyanomethyl-2-deoxy-α-D-arabino-hexopyranoside (2) exclusively. The proof of structure 2 is described. Debenzylidenation of 2 afforded the branched-chain cyano glycoside 3. Compound 3 was converted into its 3,4,6-tri-O-acetate (8) and 4,6-di-O-p-nitrobenzoate (9) derivatives. Catalytic hydrogenation of 3 over rhodium on alumina yielded methyl 3-C-2′-aminoethyl-2-deoxy-α-D-arabino-hexopyranoside which was characterized as its N-2,4-dinitrophenyl derivative (7).
Matrix Infrared and Laser Raman Spectra, Molecular Structures and Normal Coordinate Analyses of Germanium Difluoride, Monomer GeF2, and Dimer (GeF2)2
Authors: Huber H. , Kündig E. P. , Ozin G. A. , Voet A. Vander
Published: May 2006

Matrix infrared and laser Raman spectra are reported for GeF2 and (GeF2)2 in both N2 and Ar matrices. Raman depolarization measurements for the monomer in N2 matrices identify ν1 at 653 cm−1. Warm-up experiments identify infrared and Raman lines at 665, 478 cm−1 and 669, 465, and 424 cm−1 respectively, with the first stage of the polymerization of GeF2 monomer and are assigned to GeF stretching modes of the dimer (GeF2)2, having a centrosymmetric C2h, non-planar structure, containing a double fluorine bridge similar to the structure proposed for (SeO2)2. A normal coordinate analysis is performed on the dimer using a force field transferred from the monomer. The results provide additional evidence for the correctness of the vibrational and stereochemical assignments for the dimer.
A Stereospecific Synthesis of L-Desosamine
Authors: Baer Hans H. , Chiu Chung-Wai
Published: May 2006

L-Desosamine (3,4,6-trideoxy-3-dimethylamino-L-xylo-hexose), the enantiomer of a widely distributed antibiotics component, was synthesized by borohydride reduction of methyl 3,4,6-trideoxy-3-nitro-α-L-erythro-hex-3-enopyranoside followed by catalytic hydrogenation of the nitro group, N,N-dimethylation of the resulting saturated amino glycoside, and acid hydrolysis of the glycosidic bond.
Some Derivatives of 2,5-Xylidine and their Cyclization to Indoles
Authors: Kricka Larry J. , Vernon John M.
Published: May 2006

N-Methyl and N-phenyl derivatives of 2,5-xylidine have been characterized, and polysubstituted indoles obtained via cyclization of appropriate derivatives of 2,5-xylidine and 2,5-xylylhydrazine.
13C Nuclear Magnetic Resonance Studies. 34. The 13C Spectra of Several Methylcyclopentanones and -cyclohexanones
Authors: Stothers J. B. , Tan C. T.
Published: May 2006

The 13C spectra of 16 methyl substituted cyclohexanones and 15 methylcyclopentanones have been determined. These series were chosen as model systems for the study of steric and conformation effects on 13C shieldings. Complete assignments of the individual signals were accomplished by intercomparison of the shielding data within each series and the trends observed are readily interpreted in conformational terms. Each of the cyclohexanones exists preferentially in chair conformations although there is evidence of ring distortion in the tetramethyl derivatives. The cyclopentanones apparently strongly favor half-chair forms with maximum puckering at C-3 and C-4. In general, shielding differences between cis and trans isomers are pronounced and the assignment of stereochemistry for some cis–trans dimethyl derivatives is illustrated.Further examples of marked deshielding trends associated with sterically crowded δ nuclei in syn-axial arrangements are described.
Metabolites of Hyalodendron sp.: Bisdethiodi(methylthio)hyalodendrin
Authors: Strunz George M. , Heissner Christopher J. , Kakushima Masatoshi , Stillwell Merlyn A.
Published: May 2006

Spectroscopic studies and chemical correlation with hyalodendrin show that a new metabolite of Hyalodendron sp. is bisdethiodi(methylthio)hyalodendrin (3-benzyl-6 hydroxymethyl-1,4-dimethyl-2,5-dioxo-3,6-di(methylthio)piperazine).
Deuterium Isotope Effect on Shifts of 13C Magnetic Resonance Signals of Sugars: Signal Assignment Studies
Authors: Gorin Philip A. J.
Published: May 2006

The 13C chemical shifts of nuclei in several sugars undergo an isotope effect 0 to −0.10 p.p.m when a proton in the β position is substituted by a deuteron. The effect may be used for signal assignments in crowded spectra if it is taken into account that lower values are observed for 13C nuclei which are attached to more electronegative groups. The β effect coupled with the elimination of the α-carbon signal have been used to assign signals in c.m.r. spectra of the α- and β-anomers of D-glucose, D-mannose, D-allose, and D-galactose.
The Specificity of the Nucleophilic Site of α-Chymotrypsin and its Potential for the Resolution of Alcohols. Enzyme-catalyzed Hydrolyses of Some (+)-, (−)-, and (±)-2-Butyl, -2-Octyl, and -α-Phenethyl Esters
Authors: Lin Yong Yeng , Palmer David N. , Jones J. Bryan
Published: May 2006

The α-chymotrypsin-catalyzed hydrolyses of a representative spectrum of (R)- and (S)-2-butyl, -2-octyl, and -α-phenethyl esters of N-acetyl-L-phenylalanine, N-acetylglycine, α-hydroxy-β-phenyl-propionic, dihydrocinnamic, and hippuric acids have been examined. The kinetic studies were carried out in order to provide data on the practicability of exploiting the stereospecificity of the nucleophilic region of the active site of the enzyme for the resolution of racemic alcohols via selective hydrolysis of their esters. The data obtained indicate that the structure and chirality of the alcohol moieties affect both the catalytic and binding constants of the substrates and that the greatest differences between enantiomeric alcohol moieties are observed for nonspecific substrates of the dihydrocinnamate and hippurate series. For racemic esters of the latter type, the stereospecificity of the alcohol site is such that significant resolution of racemic esters and alcohols can be achieved via α-chymotrypsin-catalyzed hydrolyses on a preparative scale.
A Nuclear Magnetic Resonance Study of Nucleoside Conformation in Solution. The Effect of Structure and Conformation on the Magnetic Nonequivalence of the 5′-Methylene Hydrogens
Authors: Hruska Frank E. , Wood Donald J. , McCaig Thomas N. , Smith Anthony A. , Holy Antonin
Published: May 2006

The relative chemical shift between the 5′-methylene hydrogens of a number of purine and pyrimidine nucleosides and nucleotides in solution are presented. For structurally related pyrimidine nucleosides in aqueous solution a good correlation between this relative shift and the sum of the 4′–5′ hydrogen–hydrogen vicinal coupling constants is noted. For this series of related molecules arguments are presented that the variation in the magnetic nonequivalence of this pair of hydrogens is a consequence of conformational changes about the C4′—C5′ bond. Deviations from the correlation plot are observed for purine derivatives, nucleoside monophosphates etc. and discussed in terms of the effect of the specific chemical modification upon the nucleoside conformation and upon the intrinsic chemical shift nonequivalence of the 5′-methylene hydrogens.
Restricted Rotation in α-Carbonyl Radicals
Authors: Foster Terry , Klapstein Dieter , West Paul Ronald
Published: May 2006

Electron spin resonance spectra of tertiary α-carbonyl radicals, R1R2ĊCOR3 (R1R2R3 = H, alkyl), at 24 °C in aqueous solution show fully restricted rotation about the Ċ—CO bond. The effect is identified by differing h.f.s. constants for equivalent substituents R1 and R2. The radical intermediates are generated by direct abstraction, radical fragmentation, and reductive elimination processes.
2,3-Dioximes of Various Substituted Acetoacetamides and Their Metal Chelates
Authors: Kettrup Antonius , Striegler Klaus
Published: May 2006

Methods of preparing 2,3-dioximes of various substituted acetoacetamides are presented. The dissociation constants of these compounds and the stability constants of their metal chelates were determined by potentiometric pH measurements. The influence of the substituents of the amide group on the change of stability is discussed.
Synthesis of 4-O-α-D-Mannopyranosyl-L-rhamnopyranose
Authors: Bebault Gwendolyn M. , Button Guy G. S.
Published: May 2006

4-O-α-D-Mannopyranosyl- L-rhamnopyranose has been synthesized in 55% yield by condensation of 2,3,4,6-tetra-O-benzoyl- α-D-mannopyranosyl bromide with methyl 2,3-O-isopropylidene-α-L-rhamno-pyranoside using mercuric cyanide in acetonitrile (Helferich reaction). The disaccharide has m.p. 143–145°, [α]D + 53.0° → 60.3° (c, 1.0 water), and was characterized as the crystalline peracetates of the disaccharide (m.p. 149.5–150.5°, [α]D − 4.4° (c, 4.3 chloroform)) and of the derived alditol (m.p. 84−85°, [α]D −4.4° (c, 1.9 chloroform)).
The Stereospecific Synthesis of Neutral and Cationic Tertiary Phosphine Complexes of Platinum(II)
Authors: Dixon Keith R. , Moss Kenneth C. , Smith Martin A. R.
Published: May 2006

Stereospecific synthetic methods for the preparation of complexes of the type cis- and trans[PtClL(PEt3)2]+ and cis-[PtClX(PEt3)2] have been developed. Preparations of complexes where L = py, PPh3, PClPh2, or P(OPh)3 and X = SCN, NO2, NO3, N3, NCO, or Br are described and it is shown that bridge cleavage reactions in square planar platinum(II) complexes occur with retention of stereo chemistry.
Carbon-Sulfur Bond Cleavage in the Reaction of Alkyllithiums with Sulfoxides
Authors: Durst T. , LeBelle M. J. , Elzen Rita Van den , Tin K.-C.
Published: May 2006

When sulfoxides are reacted with alkyllithiums two competing reactions can occur: (i) abstraction of an α-hydrogen to give an α-lithiosulfoxide and (ii) carbon–sulfur bond cleavage according to R1S(O)R2 + R3Li → R1S(O)R3 + R2Li. In the cleavage reaction the group which can best carry a negative charge is most readily displaced. The displacements occur with inversion of configuration at sulfur. t-Butyllithium racemizes optically active t-butyl aryl sulfoxides within a few minutes at −78° in tetrahydrofuran. The results show that in general t-butyl-lithium and n-butyllithium are unsatisfactory bases for the efficient generation of α-lithio sulfoxides. Methyllithium or lithium diisopropyl amide are better suited for this purpose.
An Efficient and Selective Monohydrido Rhodium(I) Homogeneous Hydrogenation Catalyst Containing a Cyclic Phosphine
Authors: Budd Donna E. , Holah David G. , Hughes Alan N. , Hui Benjamin C.
Published: May 2006

The preparation of the complex RhH(DBP)4 (where DBP is a dibenzophosphole derivative) is described. It is a very effective and selective catalyst for the homogeneous hydrogenation of terminal olefins. Kinetic and mechanistic data for the hydrogenation of 1-hexene are presented.
The Trishomocyclopropenyl Cation. I. Direct Observation
Authors: Masamune S. , Sakai M. , Kemp-Jones A. V. , Nakashima T.
Published: May 2006

The trishomocyclopropenyl cation has been prepared for the first time and is shown to be a remarkably stable, highly charge-delocalized species. The large [Formula: see text] value associated with the carbons formally carrying the positive charge, the high-field chemical shift of these carbons, and the absence of hydride shift, all are significant and are consistent with the formulation of 1 subject to the limit of the n.m.r. time scale.
Quaternary Nitrogen Heterocycles. IV. The 1-Methyl-4-nitroquinolinium and 4,4-Diiodo-1,1-dimethy1-1,4-dihydroquinolinium Cations, Two Methylation Products of 4-Nitroquinoline and their Reactions in Aqueous Solutions
Authors: Bunting John W. , Meathrel William G.
Published: May 2006

Methylation of 4-nitroquinoline with methyl fluorosulfonate ("magic methyl") gives the expected 1-methyl-4-nitroquinolinium fluorosulfonate. However, methylation with methyl iodide gives an unexpected product (C11H12I3N) which is shown to be 4,4-diiodo-1,1-dimethyl-1,4-dihydroquinolinium iodide. This latter salt readily loses a molecule of methyl iodide in aqueous alkaline solution and forms 4-hydroxy-4-iodo-1-methyl-1,4-dihydroquinoline. This latter product reacts in aqueous solution with excess silver iodide or bromide in the presence of silver nitrate to give 3-iodo-1-methyl-4-quinolone or the corresponding 3-bromo derivative. The 1-methyl-4-nitroquinolinium cation readily forms a pseudobase in aqueous solution (pKROH = 5.31; pKRO− = 10.95 ). Kinetic and spectroscopic data are consistent with the predominant neutral pseudobase species being 4-hydroxy-1-methyl-4-nitro-1,4-dihydroquinoline, while the predominant pseudobase anion is the alkoxide ion of 2-hydroxy-1-methyl-4-nitro-1,2-dihydroquinoline.
Infrared Studies of Water in Crystalline Hydrates: K2CuCl4•2H2O
Authors: Thomas Gwen H. , Falk Michael , Knop Osvald
Published: May 2006

Infrared spectra of polycrystalline K2CuCl4•2H2O at different degrees of deuteration were recorded, between 4000 and 300 cm−1, at temperatures from −160 to 90 °C. The spectra confirm the existence of only one crystallographically distinct type of water molecule in the structure, on sites of symmetry C2r. Vibrational coupling of the bending fundamentals of the water molecule has been analyzed in detail. It is shown that the existence and magnitude of such coupling may be used to predict, from the spectrum of a hydrate, the manner in which a water molecule participates in the crystal structure. The structure and the vibrational spectra of K2CuCl4•2H2O are compared with those of the closely related CuCl2•2H2O.
Competition between Acid Catalyzed Interconversion and Solvolysis of Adducts of Dimethyl Azodicarboxylate and 2,5-Dimethyl-3,4-diphenylcyclopentadienone
Authors: Mackay Donald , Pilger Charles W.
Published: May 2006

Trifluoroacetic acid catalyzes the conversion of each of the isomers, the Diels–Alder adduct 1a, the 1,3,4-oxadiazine 2a, and the 1,2-diazetidine 3a into the others, with the exception of 3a → 1a. The isomerizations compete with solvolysis to the common end products, the 1,3,4-oxidiazinone 4a and methyl trifluoroacetate, directly in the case of 1a and 2a, but perhaps only by way of 2a in the case of 3a. The isomerization and solvolysis rates increase with acid concentration in dilute acid but in concentrated acid there is evidence that all the isomers are converted into a (probably) multi-protonated form of 2a, which is stable to isomerization and whose solvolysis rate decreases with increasing acid concentration.
Surface Area Effects on the Sorption of Hydrogen by Palladium
Authors: Evans Michael J. B.
Published: May 2006

Pressure–composition isotherms for dilute solutions of hydrogen in palladium have been measured at temperatures between 100 and 240 °C at pressures of up to 1000 Torr using a conventional volumetric technique. For palladium foil the isotherms are consistent with data over lower temperature ranges and with existing theoretical isotherms. With samples having appreciable surface area, however, a higher sorptive capacity is found which, it is suggested, is due to the formation of a layer of adsorbed hydrogen on the metal surface. It is demonstrated that correction can be made for this effect, to some extent, giving better agreement between the experimental data and the theoretical isotherm.The variation of partial molar enthalpy of absorbed hydrogen with hydrogen content is also affected by this surface phenomenon, although the data available at present are not sufficiently accurate for a detailed discussion.
Interaction of Palladium(II) Acetate with Sodium and Lithium Acetate in Acetic Acid
Authors: Pandey Raj N. , Henry Patrick M.
Published: May 2006

Palladium(II) acetate in acetic acid in the absence of acetate ion exists as the trimeric species Pd3(OAc)6. The reaction of the trimer with NaOAc or LiOAc at 25° was not instantaneous. Spectral studies on fully equilibrated systems indicated the first equilibria involved transformation of trimer to dimer[Formula: see text]with K32 = 7.77 × 104 M−5 and K′32 = 1.76 × 102 M−5. The kinetics of the slow transformation of trimer to dimer was studied. The reaction has the rate expression: rate = [Pd3(OAc)6] (k + k′[MOAc]) (M = Li or Na). This rate expression is consistent with substitution processes suggesting the slow step of the reaction is the SN2 attack of solvent or acetate on a Pd(II)–acetate bond to break one of the acetate bridges.In the NaOAc system conversion of trimer to dimer was complete at 0.2 M NaOAc. Further addition of NaOAc caused the dimer to be converted to monomer.[Formula: see text]
The Photochemical Reactivity of Some Benzoylthiophenes. II. Photocycloaddition
Authors: Arnold D. R. , Birtwell R. J. , . Clarke Jr. B. M
Published: May 2006

The photochemical reactivity of 2- and 3-benzoylthiophene and their para-cyano and para-methoxy derivatives, upon irradiation in the presence of isobutylene, has been studied. All six ketones undergo photocycloaddition at the carbonyl group under these conditions. The resulting oxetanes are thermally unstable; they eliminate formaldehyde and yield the 1-aryl-1-thienyl-2-methylpropene. The existing generalizations, potentially useful for predicting this photochemical reactivity, are reviewed.
The Formation of Dibenzoyl Peroxide in the Autoxidation of Benzaldehyde in the Presence of Lithium Chloride
Authors: Bühler K. , Diesch W. , Ghosh A. K.
Published: May 2006

During the autoxidation of benzaldehyde catalyzed by lithium chloride, 26% (by weight) dibenzoyl peroxide is formed. The lithium chloride is responsible for the acceleration of the oxygen uptake and the formation of dibenzoyl peroxide.
Structural Studies of Histamine H1 Effector Molecules: The Crystal Structure of the Antihistamine Drug (+)-Chlorpheniramine Maleate; [(+)-S-1-(p-Chlorophenyl)-1-(2-pyridyl)-3-N,N-dimethylpropylamine maleate]
Authors: James M. N. G. , Williams G. J. B.
Published: May 2006

Dextrorotatory chlorpheniramine maleate crystallizes from warm ethyl acetate in a P21 cell containing two formula units of the salt, with unit cell dimensions; a = 5.7669(4) Å, b = 20.338(2) Å, c = 9.1347(8) Å, β = 103.73(2)°. Diffractometer data were collected with CuKα radiation to 2θ = 128°. The structure was solved and refined to R = 0.050 and wR = 0.066. The absolute configuration is confirmed as being S. The alkylamine chain is asymmetrically disposed to the two aryl rings, the p-chlorophenyl ring being more exposed and the 2-pyridyl ring partially occluded. The molecule has an open side to which both hydrogen bond and π orbital overlap linkages can occur. The maleate mono-anion is hydrogen bonded to the dimethylamino group via a normal [Formula: see text]linkage. The intramolecular hydrogen bond of the maleate ion is 2.444(5) Å long and is asymmetric.
Identification d'un nouveau alcaloïde de canneberges
Authors: Jankowski Krzysztof , Godin Simone , Cundasawmy Niven E.
Published: May 2006

The structure of a new cranberry alkaloid, 12-methyl-1,2,3,4,6,7,12,12b-octahydroindolo[2,3-a]quinolizine was established using mass spectroscopy and by synthesis.
Reactions of Aralkyl and Unsaturated Chloramines: The Nitrenium Ion Question
Authors: Edwards O. E. , Bernath G. , Dixon J. , Paton J. M. , Vocelle D.
Published: May 2006

Evidence for intermolecular electrophilic halogenation of aromatic rings and olefinic double bonds by aliphatic chloramines at low pH, and for homolytic cyclization of unsaturated chloramines in neutral medium is presented. Independent proof of structure and stereochemistry of derivatives of 6-azabicyclo[3.2.1]octane and 2-azabicyclo[2.2.2]octane was provided. No evidence for involvement of nitrenium ions in the chloramine reactions was observed.
Photochemical Ring Enlargements of Two α-Cyanocycloalkanones
Authors: Chip G. K. , Lynch T. R.
Published: May 2006

The photochemical transformations undergone by 2-cyano-2-methylcycloheptanone (1) and 2-cyano-2-methylcyclohexanone (2) have been studied in methanol and aqueous dioxane. In the former solvent, 1 is isomerized to three products in the ratio 78:8:13, corresponding to the enals 3a and 3b, and a new ring expansion product 4, respectively. In aqueous dioxane, the cyclic imide 6 was obtained in 18% yield. Cycloalkanone 2 in methanol produces four products in the ratio 61:30:7:1, these being the isomeric enals 8a and 8b, the ester 9, and the ring expansion product 10. No imide related to 6 could be obtained from irradiation of 2 in aqueous dioxane.
Deuteron Relaxation Study of the Reorienting Methyl Groups in p-Azoxyanisole
Authors: Wiszniewska M. , Dong Ronald Y. , Tomchuk E. , Bock E.
Published: May 2006

The deuteron spin-lattice relaxation times were measured in the nematic and isotropic phases of p-azoxyanisole(CD3)2. An apparent activation energy for the methyl group reorientation in the isotropic phase is obtained. The quadrupole coupling constant along the C—D bond is found to be 147 ± 8 kHz.
The Methyl Ethers of 2-Amino-2,6-dideoxyglucopyranose (Quinovosamine)
Authors: Perry Malcolm B. , Daoust Virginia
Published: May 2006

The 3-, 4-, and 3,4-dimethyl ethers of 2-amino-2,6-dideoxyglucose have been synthesized. 3,4-Di-O-methyl-L-rhamnal on treatment with nitrosyl chloride gave dimeric 2-deoxy-3,4-di-O-methyl-2-nitroso-α-L-rhamnopyranosyl chloride which on reduction and N-acetylation afforded 2-acetamido-2,6-dideoxy-3,4-di-O-methyl-L-glucose and 2-acetamido-2,6-dideoxy-4-O-methyl-L-glucose. 2-Acetamido-2,6-dideoxy-3-O-methyl-D-glucose was made from methyl 2-acetamido-2-deoxy-3-O-methyl-α-D-glucopyranoside by the reduction of its 6-deoxy-6-iodo derivative, prepared from synthesized methyl 2-acetamido-4-O-acetyl-2-deoxy-3-O-methyl-6-O-(p-tolylsulfonyl)-α-D-glucopyranoside, to yield the required 6-deoxy-L-glucose derivative.
The Hydrolysis of Benzoate Esters by Carboxypeptidase A and the pH-Rate Profile for the Hydrolysis of O-Hippuryl-L-3-phenyllactic Acid
Authors: Bunting John W. , Murphy Joe , Myers Chester D. , Cross Gordon G.
Published: May 2006

A series of para-substituted O-benzoyl-2-hydroxybutanoic acids (but not the unsubstituted ester) are hydrolyzed by bovine carboxypeptidase A (pH 7.5, ionic strength 0.5, 25°). For the CH3O, CH3, Cl, CN, and NO2 substituents, there exist linear correlations of kcat and Km with the Hammett σ constants for these substituents (log kcat = 1.1 7σ + 1.17; log Km = −0.53σ − 2.15), although the tert-butyl group shows significant deviations from both correlation lines. The above unsubstituted ester is a reversible inhibitor of the enzymic hydrolysis of O-hippuryl-L-3-phenyllactic acid and so the lack of observable hydrolysis of this ester is attributable to nonproductive binding. The pH–rate profiles for kcat/Km and kcat have been determined for the enzymic hydrolysis of O-(p-nitrobenzoyl)mandelic acid [Formula: see text] and O-hippuryl-L-3-phenyllactic acid [Formula: see text] For the latter ester kcat is pH independent in the range pH 5–10. The mechanism of ester hydrolysis catalyzed by carboxypeptidase A is discussed in the light of the above observations and the known crystal structure of the enzyme. A definition of specific and non-specific substrates for this enzyme based on the observed pH profiles for kcat/Km is proposed.
Charge Distributions and Chemical Effects. VII. AbInitio Population Analyses of Alkanes
Authors: Kean Gérard , Fliszár Sándor
Published: May 2006

STO-3G calculations are presented for methane, ethane, propane, isobutane, neopentane, ethylene, and benzene. Optimized geometries were used; all K and L shell exponents were optimized for each molecule until stable charge distributions were obtained. The marked influence of full optimization on calculated charges is discussed in comparison both with selected GTO results and with "chemical expectancy."