bluuebunny/crossref_metadata_2025 huggingface dataset:
Absolute Configuration of Scopolamine N-Oxide and of Related Compounds
Authors: Huber Carol Saunderson , Fodor Gabor , Mandava Nagabhushanam
Published: May 2006

Structure analysis of (−) scopolamine N-oxide (1) hydrobromide monohydrate by X-ray crystallography has proven that the N-methyl group is axial and the amineoxide function is equatorial. The absolute configuration of the tropic acid residue has also been determined by anomalous scattering as being S, in complete agreement with chemical correlation experiments.The N-stereoisomer of 1 has also been detected as a minor product 2 for the first time, as a result of using 100 MHz n.m.r. spectroscopy in the product analysis of the oxidation of (−) scopolamine with hydrogen peroxide in ethanol. A similar n.m.r. study was undertaken with atropine and tropine and correlation of chemical shifts with N-configuration in the N-oxides, 3–6, was attempted. N-oxidation of scopolamine, and by analogy of related tropane bases, has taken a preferentially equatorial course, similar to other quaternization reactions.
Ion Scavenging by Neopentane in γ-Irradiated Liquid Alkanes
Authors: Stone J. A. , Matsushita G.
Published: May 2006

The γ-radiolysis of low concentrations of neopentane in liquid cyclo-C5H10 and C2H6 at 0.25 g ml−1 density leads to methane yields much greater than expected from the mixture compositions. In cyclo-C6H12, n-C6H14, cyclo-C6H11CH3, and 3-methylpentane the yields are much less than expected. The effect is explained in terms of positive ion scavenging which is enhanced by added electron scavengers. The efficiency of scavenging by C(CD3)4 in C2H6 is equal to that of ND3. The efficiency in cyclo-C5H10 is less than that in C2H6 but is greater than that observed previously in this solvent.
Hydration of CN−, NO2−, NO3−, and OH− in the Gas Phase
Authors: Payzant J. D. , Yamdagni R. , Kebarle P.
Published: May 2006

By measuring the A−(H2O)n−1 + H2O = A−(H2O)n equilibria in the gas phase and their temperature dependence, the equilibrium constants and ΔHn, n–1 and ΔSn, n–1 for some of the hydrates of NO2−, NO3−, CN−, and OH− were determined. Available thermochemical data are used for the evaluation of the total heats of hydration of the above ions. The total heats of hydration were then compared with the ΔH1,0. Relative to the total hydration energies the ΔH1,0 of the above ions were found larger than the ΔH1,0 of the halide ions.An approximate linear correlation was found to exist between ΔH1,0 of negative ions and the heterolytic bond dissociation energy D(A−–H+). With this relationship independent estimates for the electron affinities of NO2 and NO3 could be obtained.The ΔHn, n–1 of OH− were found in essential agreement with earlier measurements from this laboratory and in disagreements with recent measurements (Friedman) which gave much higher values.
The Effect of SF6 and N2O on the 2537 Å Photolysis of Aqueous I− and Fe(CN)64−
Authors: Crawford M. , Rumfeldt R.
Published: May 2006

The solvated electron yield from the 2537 Å photolysis of aqueous I− containing N2O and SF6 is given by [Formula: see text] with the calculated ratio [Formula: see text] from the 2537 Å photolysis of aqueous Fe(CN)64− was measured using SF6, N2O, and mixtures of N2O and SF6 as the scavengers with the material balance being represented by[Formula: see text]. The average value obtained was [Formula: see text] = 0.67 ± 0.03 and the calculated values of [Formula: see text] were 2.20 ± 0.2 from the product ratio's at low [SF6] and 1.86 ± 0.2 from a competition plot at higher [SF6]. A mechanism is presented describing the specificity of SF6 as a scavenger of eaq−.
Total Synthesis of DL-Glucose, 3-O-Methyl-DL-glucose, and 3-Deoxy-DL-ribo-hexopyranose from 1,6:3,4-Dianhydro-β-DL-allo-hexopyranose, a Product Obtained from Acrolein Dimer
Authors: Singh U. P. , Brown R. K.
Published: May 2006

The reaction of butyllithium in ether with 1,6:2,3-dianhydro-4-deoxy-β-DL-ribo-hexopyranose (1), a substance obtained in five steps from acrolein dimer, gave 1,6-anhydro-3,4-dideoxy-β-DL-erythro-hex-3-enopyranose (2). The compound 1,6:3,4-dianhydro-β-DL-allo-hexopyranose (3), obtained from 2, was converted by reaction with aqueous barium hydroxide followed by hydrolysis of the product, to DL-glucose 5. Treatment of 3 with sodium methoxide in methanol followed by acid hydrolysis of the 1,6-anhydro intermediate 6, gave 3-O-methyl-DL-glucose (7). The same intermediate, 6, along with the methyl glycoside 8, could be obtained by the acid-catalyzed reaction of 3 with methanol. Lithium aluminum hydride reacted with 3 to form 1,6-anhydro-3-deoxy-β-DL-ribo-hexopyranose (9), which was hydrolyzed readily to 3-deoxy-DL-ribo-hexopyranose (10).Yields were excellent throughout. All products obtained from the oxirane 3 were those resulting only from trans diaxial opening of the oxirane ring.
Crystal and Molecular Structure of the 1:1 Complex of Chloral Hydrate and 7-Bromo-2,3-dihydro-1-methyl-5-phenyl-1,4-benzodiazepin-2-one
Authors: Dunphy R. F. , Lynton H.
Published: May 2006

The structure of a 1:1 complex of chloral hydrate and 7-bromo-2,3-dihydro-1-methyl-5-phenyl-1,4-benzodiazepin-2-one has been determined by the heavy atom method. The complex crystallizes in the orthorhombic system, space group Pbca, with unit cell dimensions a = 13.45(1), b = 26.74(2), c = 11.23(1) Å and 8 molecules in the unit cell. The 1:1 complex of chloral hydrate and diazepam, 7-chloro-2,3-dihydro-1-methyl-5-phenyl-1,4-benzodiazepin-2-one, is isomorphous with the above compound and has unit cell dimensions a = 13.43(1), b = 26.60(2), c = 11.20(1) Å. The final atomic parameters have been obtained from a block-diagonal least squares refinement using anisotropic thermal parameters. The final agreement residual for 575 observed reflections is R = 0.079.The structure consists of chains of chloral hydrate and Br-diazepam molecules linked by hydrogen bonds.
The Specific Activity of Silica Supported Platinum for the Catalysis of Hydrogen – Water Deuterium Exchange
Authors: Sagert N. H. , Pouteau R. M. L.
Published: May 2006

Some rate data are reported for deuterium exchange between water and hydrogen using series of platinum–silica catalysts. Three different methods of preparing catalysts were used to give different series of metal particle sizes. Within each series, the particle size was increased by sintering batches in air, at temperatures up to 700 °C. These methods produced platinum particles ranging from 5 to 250 Å in diameter. Metal surface areas and particle sizes were measured by hydrogen chemisorption, X-ray diffraction, and electron microscopy.The specific rates, i.e., rates per unit surface area of platinum varied by a factor of three within each series, reaching a maximum for sintering temperatures of about 500 °C. These maximum rates, measured at 127 °C with a water-to-hydrogen ratio of 0.31, varied from 1.9 × 10−8 to 5 × 10−8 mol D2 cm−2 s−1. Thus no effect of particle size on rate was observed, and the differences noted are ascribed to other effects of the methods of preparing the catalysts.
The Photolysis and Radiolysis of Simple Mercaptans in Dilute Glassy Matrices
Authors: Skelton J. , Adam F. C.
Published: May 2006

The e.p.r. spectrum of thiyl radicals is obtained when dilute solutions of aliphatic mercaptans are photolyzed in a xenon matrix at 77 °K. No proton hyperfine structure is observed at low concentrations of thiol but it appears at higher concentrations due to the reaction of hot hydrogen atoms with solute mercaptan molecules. When small amounts of the thiols are dissolved in glassy hydrocarbon matrices such as 3-methylpentane, there is produced after photolysis hyperfine structure characteristic of the solvent as well as the thiyl resonance. The e.s.r. absorption due to the solvent species disappears when the matrix is warmed a few degrees above 77 °K but thiyl radicals are stable up to the melting point of the glass. The corresponding γ-irradiated glasses do not give thiyl absorption, but two other species are produced along with solvent radicals. No thiyl radicals are observed following radiolysis, or upon photo-bleaching the new species. The spatial distribution of the neutral radicals in the glasses is discussed in view of these results.
Exchange Averaging of Methylol Groups Attached to Phosphorus
Authors: Ellzey Jr. S. E. , Connick Jr. W. J. , Boudreaux Gordon J.
Published: May 2006

Variable temperature 1H n.m.r. spectra of pyridine solutions of tetrakis(hydroxymethyl)phosphonium chloride indicate that chemical exchange of methylol groups of the salt with those of the small amount of tris(hydroxymethyl)phosphine formed is the cause of their magnetic equivalence at elevated temperatures. Triethylamine transforms the salt into the phosphine and at least two other phosphorus species which may result from reaction of formaldehyde at oxygen of the phosphine.
Cyclopentadienylidenecarbonyl: the Major Primary Thermolytic Fragment of Salicylaldehyde
Authors: Mamer O. A.
Published: May 2006

The thermal fragmentation of salicylaldehyde was studied from two aspects. Firstly, the temperature dependence of the intensity of the thermolytic fragment molecular ions was observed at 11 eV in the effluent from a helium flow thermal reactor attached through a helium separator to the ion source of a mass spectrometer. Secondly, the products of the thermolysis on a semi-preparative scale under trapping conditions were determined by coupled gas chromatographic – mass spectrometric analysis.The title compound is the major primary thermal fragment in this study and was trapped with methanol as carboxymethylcyclopentadiene.
Isolation of 2(S)-Dichloroacetamido-3-(p-acetamidophenyl)propan-1-ol from a Chloramphenicol-producing Streptomyces Species
Authors: Wat Chi-Kit , Malik V. S. , Vining L. C.
Published: May 2006

Cultures of a chloramphenicol-producing Streptomyces to which 2(S)-amino-3(R)(p-nitrophenyl)-propan-1,3-diol (p-nitrophenylserinol) was added produced a new metabolite which has been identified as 2(S)-dichloroacetamido-3-(p-acetamidophenyl)propan-1-ol (1). The structure was confirmed by chemical synthesis. No radioactivity was incorporated into 1 when 14C-labeled p-nitrophenylserinol was used, suggesting that 1 is formed not by metabolism of the supplement but by diversion of intermediates normally used for chloramphenicol biosynthesis.
Transient Phenomena in Dissociation of Diatomic Molecules
Authors: Boyd R. K. , Burns George
Published: May 2006

A model suitable for studies of non-equilibrium effects in chemical reactions (13) was used to predict incubation times for the dissociation of O2 in Ar between 2900 and 7200 °K. It was found that the model accounts satisfactorily for the experimental data. On the other hand previously used theories underestimate these incubation times by a factor of five to ten; the discrepancy is traced to assumptions used in previous investigations. When the same model is applied to the dissociation of Br2 in Ar and Cl2 in Ar, it correlates well a variety of experimental data, obtained over a wide temperature range.
Methyl Cyanodithioformate as a Reactive Dienophile in Diels–Alder Reactions
Authors: Vyas D. M. , Hay G. W.
Published: May 2006

A Diels–Alder reaction between cyclopentadiene and methyl cyanodithioformate afforded a 60:40 mixture of the isomers 2a and b. The n.m.r. studies of these compounds and the products of LiAlH4 reduction, 3a and b, established that the major isomer, 2a, was 3-exo-cyano-3-methylthio-2-thiabicyclo-[2.2.1]hept-5-ene, and that 3a was the corresponding 3-exo-aminomethyl compound.
The Reaction of trans-Chlorocarbonylbis(triphenylphosphine)iridium(I) with Silver Nitrate
Authors: Cash D. N. , Harris R. O.
Published: May 2006

The reaction of trans-[IrI(CO)(PPh3)2Cl] (1) with AgNO3 in acetone leads to two products. If a small excess of AgNO3 is present, [IrI(CO)(PPh3)2(NO3)] is isolated; while if a larger excess of AgNO3 is present, the novel compound [Ir(CO)(PPh3)2(NO3)2Ag] is isolated as product. The characterization, and some reactions of these complexes are discussed.
Olefin Formation in the Radiolysis of n-Hexadecane
Authors: Falconer W. E. , Sunder W. A. , Walker L. G.
Published: May 2006

Olefin production in n-hexadecane, irradiated both in liquid and solid states, was estimated by gas chromatography and coulometric titration. Yields of congruent olefin extrapolated to zero dose were G = 1.6 and 2.8 in the solid and liquid, respectively. Total olefin yields at low doses are 2.2 and 4.2 in the solid and liquid. Scission olefin yields are 0.5 and 1.0. Evidence was found for cis as well as trans hexadecene isomers. cis-Olefins can be lost preferentially by exposure to air.
Hydrogen Gas Solubility in the Dimethyl Sulfoxide – Water System: A Further Clue to Solvent Structure in These Media
Authors: Symons E. A.
Published: May 2006

The solubility of hydrogen gas in the dimethyl sulfoxide (DMSO) – water system has been measured as a function of temperature from 25 to 80 °C. A distinct minimum occurs in the solubility, as expressed on the molar scale, in the region 25–35 mol% DMSO at 25 °C. As the temperature is raised towards 80 °C the minimum becomes less pronounced. The maximum deviation from calculated "ideal" behavior is found at 32 ± 5, 35 ± 5, and 32 ± 5 mol% DMSO for 25, 50, and 80 °C, respectively.A maximum is observed for both the partial molal entropy and heat of solution of hydrogen in the same solvent composition region. These results are discussed in terms of a changing entropy and energy of hole formation in the solvent with composition, which in turn is related to DMSO–water interaction in solution.A temperature-dependent equilibrium between DMSO•2H2O and DMSO•3H2O complexes in solution is proposed in an attempt to correlate the considerable data which have been reported in the literature for the DMSO–water system. The second complex is thought to be present in significant quantity only at temperatures well below 25 °C.
Photoelectron Spectra and Bonding in Some Halosilanes
Authors: Frost D. C. , Herring F. G. , Katrib A. , McLean R. A. N. , Drake J. E. , Westwood N. P. C.
Published: May 2006

The photoelectron spectra of some halosilanes, SiH3X (X = F, Cl, Br), SiH2X2 (X = F, Cl), and SiHCl3 have been studied, to obtain information on the bonding, especially (p → d)π back-bonding to silicon. The spectra were assigned on simple orbital overlap grounds, by comparison with the carbon analogues and by use of CNDO/2 calculations. Few discrepancies were found, but in these cases the first method was preferred. There is ample evidence from the individual ionization potentials and by comparison of the spectra with those of the analogous carbon compounds for interaction of the halogen pπ electrons with the silicon d orbitals. This is also indicated by some empirical calculations on the chlorosilanes, which also confirm the assignment of the spectra.It can also be shown that the ionization potentials are consistent with the silicon–halogen σ bond strength decreasing through the series H3SiF > H3SiCl > H3SiBr.
Observations on the Visible Emission from Electronically Excited CS2
Authors: Arnold S. J. , Kimbell G. H.
Published: May 2006

A detailed study bas been made of the CS2 afterglow emission observed when either pure CS2 or a CS2–Ar mixture is passed through a microwave discharge or when CS2 is introduced into a stream of discharged argon or active nitrogen. The emission is continuous and extends from 340 to 640 nm with a maximum at 440 nm. The emitting state is thought to be the V state which is responsible for the CS2 fluorescence.
The Pyrolysis of Tetramethyltin
Authors: Johnson R. P. , Price S. J. W.
Published: May 2006

The pyrolysis of tetramethyltin has been studied in a toluene carrier flow system from 803–941 °K using total pressures of 10.6 to 52.4 mm. Contact times varied from 0.49 to 13.8 s and the amount of decomposition from 1.35–98.7%. The progress of the reaction was followed by measuring the amount of methane, ethane, ethylene, and ethylbenzene formed. No appreciable heterogeneous reaction was detected and the first order rates constants appear to have been determined at the high pressure limit. The quantity of undecomposed alkyl was also measured and was found to be in agreement with the product analysis if four methyl radicals are released for each molecule undergoing reaction.Least squares analysis gives[Formula: see text]with an estimated uncertainty in E of ± 1 kcal mol−1. The activation energy should be a good approximation to D[(CH3)3Sn—CH3].
Theoretical Anisotropic Hyperfine Tensors in Neutral Radicals
Authors: Falle H. R. , Whitehead M. A.
Published: May 2006

Anisotropic hyperfine tensors were calculated for C—H, (C—CH3), allyl, and perinaphthenyl. In the McConnell and Strathdee theory, the anisotropic proton tensor depends primarily on the STO exponent chosen for the 2pπ, carbon atom orbital. By decreasing the exponent ζπ from the normal Slater value to ~ 1.3, the effect of σ-spin density in the C—H bond could be taken into account. However, this reduction in ζπ yields too small a value for [Formula: see text] which governs the anisotropic 13C tensor. Contributions to the anisotropic proton and 13C hyperfine tensors are discussed, and the results compared with recent abinitio calculations, as well as single-crystal and liquid crystal data.
Infrared Studies on Rotational Isomerism. VI. Normal-Coordinate Analysis of 2-Chloro-, 2-Bromo-, and 2-Cyanoethanol
Authors: Giguère Paul A. , Schneider Michel
Published: May 2006

A normal-coordinate analysis of three substituted ethanol molecules X—CH2—CH2—OH (where X = Cl, Br, or CN) was carried out using the simple valence force field model, and a computer program of Schachtschneider translated into Fortran language by Brooks. The effect of internal hydrogen bonding was studied by adding one extra symmetry coordinate, H … X (two, H … C and H … N, in the case of 2-cyanoethanol). The corresponding force constants show a good correlation with the hydrogen bond strengths. Most of the other force constants maintain the same value in the gauche and the trans rotamers. In general the calculated fundamental frequencies agree closely with the observed ones. The potential energy distribution confirms the extensive coupling between certain vibrations; particularly the skeleton stretching and the CH2 twisting and rocking. Only the C—X stretching and the skeleton bending vibrations are strongly affected by rotational isomerism.
Rates of Reaction of Nickel (II) with Terpyridine in Dimethyl Sulfoxide
Authors: Cock Patricia A. , Cottrell C. E. , Boyd R. K.
Published: May 2006

The rates at which 2,2′,2″-terpyridine reacts with nickel(II) ion to form the monoligand–nickel(II) and the bisligand–nickel(II) complexes were determined in DMSO solution. Ni(terpy)Cl2 was isolated, and used to study the rate of formation of bis complex. The second-order rate constants were found to parallel the rates of DMSO exchange, determined using n.m.r. techniques, from the respective paramagnetic nickel species. Attempts were made to relate the results to the generally accepted "dissociative" pathways for this class of substitution reactions.
Photocyclization Reactions of Aryl Polyenes. V. Photochemical Synthesis of Substituted Chrysenes
Authors: Leznoff Clifford C. , Hayward Roger J.
Published: May 2006

The photocyclization-oxidation reaction of 1,6-di-p-substituted-phenyl-1,3,5-hexatrienes gave 3,9-disubstituted-chrysenes. Similarly, irradiation of 1-p-substituted-phenyl-6-phenyl-1,3,5-hexatrienes yielded 3-substituted-chrysenes. The 3-substituted-chrysenes were independently prepared in a high yield by the photocyclization-oxidation of 1-α-naphthyl-2-p-substituted-phenylethylenes.
The Reactions of Substituted Germyl- and Silylhydrazines with BX3 and CY2 Acceptor Species
Authors: Peterson L. K. , Thé K. I.
Published: May 2006

Boron trimethyl reacts with each of the organometalloid-hydrazine derivatives Me2NN(R)GeMe3 (R = H, Me, SiMe3) except Me2NN(SiMe3)GeMe3, and with Me2NNHSiMe3, forming 1:1 adducts. With Me2NN(SiMe3)GeMe3 and BMe3, no adduct was formed even at low temperatures. On the basis of p.m.r. spectra, the metalloid-substituted nitrogen atom rather than the terminal nitrogen, is indicated as the basic center at which adduct formation occurs. With BF3, the Si—N and Ge—N bonds of the hydrazine derivatives were cleaved, again indicating attack at the central nitrogen atom. In a series of experiments involving CY2 (Y = O, S) and Me2NN(R)MMe3 (R = H, Me, SiMe3; M = Si, Ge), reaction occurred readily for R = H, but less readily for R = Me and for the compound Me2NN(GeMe3)2, while no reaction was observed for the compounds Me2NN(SiMe3)2 and Me2NN(SiMe3)GeMe3, even when heat or basic catalysts were employed. Reaction products, carbamate and thiocarbamate derivatives, Me2NN(R)C(Y)YMMe3, were characterized on the basis molecular weight, i.r., p.m.r., and mass spectroscopy, and m.p. data. Ease of formation is discussed in terms of electronic and steric effects.
The Infrared and Raman Spectra of 3-Chloro-1,2,5-thiadiazole
Authors: Richardson A. W.
Published: May 2006

The i.r. and Raman spectra of 3-chloro-1,2,5-thiadiazole have been recorded. Assignments have been made for all 15 fundamental vibrations on the basis of these observations plus some data from the vapour-phase u.v. absorption spectrum.
Energy Distributions of Reaction Product by Statistical Phase Space Theory
Authors: Wong W. H.
Published: May 2006

The phase space theory of chemical reaction in which all accessible channels are uniformly weighted was shown to be inappropriate for describing exothermic reactions. Modification to the theory was introduced by a concept of partial statisticity in which only that portion of the phase space available to each vibrational level was treated statistically. The product rotational and translational distributions of the reaction, Cl + HI, and its isotopic variant, Cl + DI, were computed by this modified formulation and compared with that obtained from a straight application of the phase space theory. The implication of the profound differences found from these two formulations was discussed in light of experimental data.
Anomalous Ratios of Formation Constants: Possible Invalidity in the Successive Constants
Authors: Steger H. F.
Published: May 2006

The causes of inaccuracy in the values of the successive formation constants for 1:2 metal:ligand complex systems for which K1 ≤ K2 are discussed. The experimental error in the [Formula: see text] pL data has been shown to become increasingly important as K1/K2 decreases. It has been concluded that the successive constants cannot be determined if K1/K2 < 10−2.4. Their product, K1K2, can, however, be determined. It is also shown that the value of K2 cannot be determined for the iron complexes with bipyridyl and 1,10-phenanthroline.
A Semi-empirical Analysis of the Electronic Spectra and Molecular Structures of Hydrogen Cyanide and Carbon Dioxide
Authors: Absar I. , McEwen K. L.
Published: May 2006

All valence electron molecular orbital calculations have been carried out on hydrogen cyanide and carbon dioxide using a minimum basis set of Slater-type orbitals by a semi-empirical SCF-LCAO-MO method described earlier for formaldehyde. Since many of the excited states of these molecules are bent, a series of calculations is carried out on hydrogen cyanide in the linear configuration and in bent configurations with H—C—N angles of 150°, 120°, and 90°, and on carbon dioxide in the linear configuration and bent configuration with O—C—O angle of 90°. The binding energy changes in various molecular orbitals on bending are used to interpret electronic spectra and are also compared with Walsh's curves.
Urea–Boron Trihalide Adducts. I. The Boron Trifluoride Adduct of Tetramethylurea
Authors: Hartman J. S. , Schrobilgen G. J.
Published: May 2006

Evidence is presented that oxygen is the donor atom in the 1:1 adduct of tetramethylurea and boron trifluoride (TMU•BF3). Hydrogen fluoride, a common impurity in boron trifluoride, leads to the formation of [Formula: see text] as well as TMU•BF3. Exchange reactions among TMU, [Formula: see text]and TMU•BF3 are investigated briefly. The results of the present investigation are compared with the results of a previous study which indicated that nitrogen is the donor atom in BF3 adducts of some partially alkylated ureas.
Chemistry of Proximal π-Bond Systems. Part I. Synthesis of Vicinal Exocyclic Dimethylene Hydrocarbons
Authors: Butler D. N. , Snow R. A.
Published: May 2006

Thirteen new bi- or polycyclic vicinal exocyclic dimethylene hydrocarbons (10–22) have been synthesized and some of their spectral properties recorded. The generally most useful synthetic route to such compounds utilizes base-catalyzed double elimination from trans-1,2-bis(hydroxymethyl)alkyl p-toluenesulfonates as the final step in the production of the conjugated diene.
Mass Spectrometry of some Nuclear Substituted Styryl Ketones
Authors: Smith P. J. , Dimmock J. R. , Taylor W. G.
Published: May 2006

The mass spectra of a series of nuclear substituted styryl ketones with the structure[Formula: see text]and several relaTed compounds have been determined. The major fragmentation pathways include such processes as an aromatic substitution reaction occurring in the molecular ion as well as the McLafferty rearrangement. Only one of the two possible α-cleavages at the carbonyl function was observed. The major decomposition processes are outlined and compared with the recent results of a study on α,β-unsaturated aliphatic ketones. Mechanistic pathways are suggested for the formation of the major fragment ions.
Fully Fluorinated Alkoxides. Part VI. Derivatives of Hydroxyhexafluoroisobutyric Acid
Authors: Price J. T. , Tomlinson A. J. , Willis C. J.
Published: May 2006

Hydroxyhexafluoroisobutyric acid, HOC(CF3)2COOH, H2(HHIB), gives complexes with a variety of metals, acting as a chelating, dinegative ligand. Derivatives prepared include [B(HHIB)2]−, [M(HHIB)2]2− (M = Ni, Cu, Co), [M(HHIB)3]3− (M = Al, Cr, Mn, Fe), and mixed ligand complexes of Cu and Ni with HHIB and nitrogen- or phosphorus-containing ligands. In some cases, the HHIB anion appears to act as a tridentate ligand through carboxylate bridging. HHIB is close to water in the spectrochemical series.
Structure cristalline et moléculaire du thiocyanate mercurique
Authors: Beauchamp A. L. , Goutier D.
Published: May 2006

Hg(SCN)2 crystals belong to the monoclinic space group C2/m with a = 10.878 Å, b = 4.042 Å, c = 6.435 Å, β = 95.28°, and Z = 2. The structure was solved by the Patterson method and refined on 217 independent observed reflections to a R factor of 0.032. All the atoms are found on the planes of symmetry of the unit cell with mercury occupying centrosymmetric positions and forming collinear Hg—S bonds to two coplanar SCN groups. An octahedral environment is achieved through weak interaction of mercury with the nitrogen atoms on four neighboring molecules.
Photoreactions of Nitroso Compounds in Solution. XX. Photoreduction, Photoelimination, and Photoaddition of Nitrosamines
Authors: Chow Y. L. , Lau M. P. , Perry R. A. , Tam J. N. S.
Published: May 2006

It has been established that alkylnitrosamines undergo photoreduction in methanol solutions in the presence of an acid to give the parent amine, formaldehyde, and N-aminoformamide. Where it is possible, an exchange reaction between the δ-hydrogen and the nitroso group is also observed during this photolysis. However, photoelimination also occurs in competition with photoreduction, the extent of which is dependent on the rates of the two photoprocesses. In aqueous solutions, N-nitrosamines predominantly undergo photoelimination. Those nitrosamines that undergo rapid photoelimination or photoreduction do not efficiently add to olefins photolytically. Conversely if photoaddition is retarded, a nitrosamine takes elimination or reduction pathways. Excitation of n → π* or π → π* transition band of N-nitrosamines gives virtually the same photoreaction patterns. Minor differences in the photoproducts are attributed to other secondary reactions.
A Convenient Synthesis of Propargylic Esters and γ-Keto Esters. The Reaction of Trialkynylboranes with Ethyl Diazoacetate, and the Unidirectional Hydration of Propargylic Esters
Authors: Hooz John , Layton Robert B.
Published: May 2006

Trialkynylboranes react with ethyl diazoacetate to provide propargylic esters. The process occurs under mild conditions (−20°) and in good yields. Propargylic esters undergo unidirectional mercuric ion-promoted hydration to afford good yields of γ-ketoesters.
The Crystal Structure of Potassium Hydrogeniodate (V), KIO3•HIO3
Authors: Kemper G. , Vos Aafje , Rietveld H. M.
Published: May 2006

The crystal structure of KIO3•HIO3 has been determined by three-dimensional single crystal X-ray diffraction and by neutron powder diffraction. The crystallographic data are a = 7.025(2), b = 8.206(2), c = 21.839(5) Å, β = 97.98(2)°, space group P21/c, Z = 8 units KIO3•HIO3. The residual [Formula: see text] was 0.048 for 7516 independent X-ray reflections measured on a three-circle diffractometer with Zr-filtered Mo radiation. The results of the present study show good qualitative agreement with the structure recently determined by Chan and Einstein (7). The HIO3 and [Formula: see text] groups are pyramidal, the I—O(H) bonds vary from 1.898 to 1.939(4) Å and the I—O bonds from 1.786 to 1.827(4) Å, these lengths are not corrected for the effects of thermal motion. Strong O—I … O interactions and electrostatic attractions between K+ and Oδ− give slabs of thickness [Formula: see text] The slabs are connected by hydrogen bonds of 2.710 and 2.694 Å.
Etude de l'association du 2,6-di-ter-butylparacrésol avec la cyclohexanone
Authors: Bourdéron C.
Published: May 2006

The association between 2,6-di-tert-butylparacresol and cyclohexanone has been investigated in solutions down to liquid nitrogen temperature through the measurement of i.r. spectra. The presence of 1:1 and 1:2 complexes in a certain range of concentration was ascertained and the nature of these complexes was established. We observed solvent induced hydrogen bond formation in a bromine containing solvent.
Hindered Rotation in Styryl Anions
Authors: Brownstein S. , Worsfold D. J.
Published: May 2006

Magnetically non-equivalent meta-protons, and occasionally ortho-protons, were observed on the benzene ring in styryl anions. With some cations and solvents it was possible to follow the coalescence of the peaks with increasing temperature and obtain Arrhenius activation energies for rotation of the phenyl group.
Use of Eu(fod)3 Shift Reagent and Solvent Effects in Structural Elucidation of Novel Isomeric Pyrimidones and Model Methoxylated Pyrimidines
Authors: Neville George A.
Published: May 2006

1-Ethyl-1,6-dihydro-2,4-dimethoxy-5-methyl-6-oxopyrimidine (1a) and 1,5-diethyl-1,6-dihydro-2,4-dime-thoxy-6-oxopyrimidine (2a) are shown to be the correct positional isomers, respectively, for the major O,O-dimethyl derivatives isolated from the reaction products of 1-ethyl-5-methylbarbituric acid (1) and the new 1,5-diethylbarbituric acid (2) with excess diazomethane. In addition to the above compounds, the behavior of 2,4-dimethoxypyrimidine (3), 4,6-dimethoxypyrimidine (4), 2,4,6-trimethoxypyrimidine (5), and 6-chloro-2,4-dimethoxypyrimidine (6) were studied by p.m.r. spectrometry in various solvents. The relatively new shift reagent, Eu(fod)3 was used in these studies because of its affinity for weak electron donors such as ethers.
The Structures of the Trihydroxyflavans from the Acid-catalyzed Rearrangement and Dimerization of 3-Carene-2,5-dione
Authors: Still I. W. J. , Snodin D. J.
Published: May 2006

The structures of the trimethyl ethers of three of the four mechanistically probable trihydroxyflavans derived by acid-catalyzed rearrangement and dimerization of 3-carene-2,5-dione have been assigned on spectroscopic grounds and by analogy with earlier results obtained under conditions which precluded dimerization. Confirmation of these assignments has been obtained by the unambiguous synthesis of two of the isomeric trimethyl ethers from simple aromatic precursors.
Selective Reduction of Carbohydrate Nitroolefins
Authors: Baer Hans H. , Rank Werner
Published: May 2006

Reduction of the four stereoisomeric methyl 4,6-O-benzylidene-2,3-dideoxy-3-nitro-hex-2-enopyranosides (1–4) with sodium borohydride gave in 80–90% yield the corresponding saturated nitro glycosides that possess an equatorial nitro group (5–8). Reduction of 1–4 with zinc and acetic acid gave in similar yields the corresponding 2,3-dideoxy-3-oximino glycosides (9–12). Two of the latter were deoximated to 2,3-dideoxy-3-oxo sugar derivatives.
Sur la reduction par les hydrures complexes de benzyl-3 camphres
Authors: Richer Jean-Claude , Rossi Armand
Published: May 2006

Benzyl-3 camphors have been prepared and the stereochemistry of their reduction by complex hydrides is reported; the corresponding benzyl-3 borneols have also been prepared and characterized.
Kinetics and Mechanism for the Hydrolysis of Chlorothionoformate and Chlorodithioformate Esters in Water and Aqueous Acetone
Authors: McKinnon D. M. , Queen A.
Published: May 2006

The effects of structural changes on the rates of hydrolysis of a series of chlorothionoformate esters and the analogous chlorodithioformate esters have been studied. For both classes of compound, the reactivity is enhanced by increased electron donation by the hydrocarbon group. These results, the activation parameters for the hydrolyses of the methyl compounds, and the solvent isotope effect are shown to be consistent with the operation of the SN1 mechanism.
Conformational Studies of the Benzophenone and Thiobenzophenone Radical Anions
Authors: Adam F. C. , Aarons Leon J.
Published: May 2006

A conformational energy map is calculated for the anions of benzophenone and thiobenzophenone, using a Bartell repulsion potential. A low energy configuration is obtained in which the phenyl rings are counterrotated by 30° from the planar form. The energy barrier to concerted rotation is also calculated and found to be in reasonable agreement with the findings of Takeshita and Hirota for the oxyketyl. Spin density distributions are also given.
Photolysis of Di-tert-butyl Peroxide at High Pressure
Authors: Yip C. K. , Pritchard H. O.
Published: May 2006

Di-tert-butyl peroxide has been photolyzed at 2537 Å in the gaseous phase in the presence of up to 47 amagats (2.10 mol/l) of propane and of cyclopropane. It was confirmed that no acetone is formed in the limit of infinite hydrocarbon concentration and therefore that the primary chemical act leading to the eventual formation of acetone is the formation of two tert-butoxy radicals from the excited peroxide molecule; in addition, some crude information was obtained concerning relative rates of photochemical vs. deactivation processes. It was also found that at these densities the tert-butoxy radical formed in the photolysis of di-tert-butyl peroxide did not appear to differ in chemical reactivity from the tert-butoxy radical formed in the thermal decomposition of di-tert-butyl peroxide.
Microwave Spectrum of 1,3-Dioxane
Authors: Kewley R.
Published: May 2006

The microwave spectrum of 1,3-dioxane has been studied within the region 8 to 40 GHz. The rotational constants of the molecule in its ground vibrational state are, in MHz, A = 4999.94(0.05), B = 4807.61 (0.05), and C = 2757.12(0.05). The dipole moment components are, in Debye units, μb = 1.61 (0.02), μc = 1.29(0.01), and μ = 2.06(0.03). The values of the above quantities are consistent with a chair form structure. Rotational spectra due to five excited vibrational states of 1,3-dioxane have been assigned.
The Interception of N-Dibenzylaminonitrene Generated from N-Azido Dibenzylamine
Authors: Ahmed Riaz , Anselme J.-P.
Published: May 2006

N-Dibenzylaminonitrene (6) has been shown to be generated from the decomposition of N-azido dibenzylamine (9) by its interception with 4-phenyl-1,2,4-triazoline-3,5-dione, as the azimine (8).
An Electron Spin Resonance Examination of Ferrocenylalkyl- and Aryl Ketyls
Authors: Bigam G. , Hooz John , Linke Siegfried , McClung R. E. D. , Mosher Melvyn W. , Tanner Dennis D.
Published: May 2006

Several ferrocenylalkyl- and aryl ketyls were generated and their e.s.r. spectra were recorded. Pentadeuterio-benzoylferrocene and benzoyl perdeuterioferrocene were synthesized. Analysis of the e.s.r. spectra of their corresponding ketyls enabled the determination of the hyperfine splitting constants of benzoylferrocene ketyl, and allowed an assignment of the electron densities at various positions in the molecule.A comparison of the magnitudes of the g-values for the ketyls derived from benzophenone (2.0034), benzoylferrocene (2.0062), and 2,2-dimethylpropanoylferrocene (2.0126), combined with the proton hyperfine splittings, gave some insight into the nature of the interaction of the free electron with the ferrocene system.
Synthesis and Ion Exchange Properties of Thermally Stable Titanium(IV) Vanadate: Separation of Sr2+ from Ca2+, Ba2+, and Mg2+
Authors: Qureshi Mohsin , Varshney K. G. , Kabiruddin S. K.
Published: May 2006

A new, thermally stable, and highly strontium-specific inorganic ion exchanger, titanium(IV) vanadate, has been prepared by mixing 0.5 M solution of titanic chloride and sodium vanadate at pH 0–1. Its ion exchange capacity is 0.65 mequiv./g at 400 °C. Separation factors of Sr2+ with respect to Ba2+, Ca2+, and Mg2+ are 8, 11.8, and 33.3, respectively. Binary mixtures of Sr2+ with Ba2+, Ca2+, and Mg2+ have been separated. Calcium and magnesium are eluted with 0.001 M HNO3. Barium and strontium are eluted with 0.01 and 0.1 M HNO3, respectively. A new parameter ΔC/ΔT is proposed for the study of structural changes in inorganic ion exchangers.
Kinetics and Rate Constants of Reactions Leading to Hydration of and in Gaseous Oxygen, Argon, and Helium Containing Traces of Water
Authors: Payzant J. D. , Cunningham A. J. , Kebarle P.
Published: May 2006

The rate constants for the forward and reverse components of gas phase reactions:[Formula: see text]were measured with a pulsed electron beam, time resolved detection high pressure mass spectrometer at 300 °K. O2, Ar, and He at pressures from 1–7 Torr were used as third gas M. The forward reactions were found to be third order and the reverse reactions second order. Establishment of the equilibria could also be observed.
Sterically Hindered Aromatic Compounds. IV. Solvolysis of t-Butyl-, Phenyl-, and Trialkyl-benzyl Chlorides in Ethanol–Water. Evidence for Steric Acceleration in 2,4,6-Tri-t-butylbenzyl Chloride
Authors: Barclay L. R. C. , Sonawane H. R. , Hudson J. C.
Published: May 2006

The effect of o-, m-, and p-t-butyl and phenyl groups on solvolysis of the benzyl chlorides in 80% by volume ethanol–water was studied through conductometric rates and activation parameters. The rate constants for para-and meta-substituents were correlated by a Brown σ+ plot indicative of an SN1-type mechanism. Variations in ΔS* can be rationalized in terms of differential solvation effects. Solvolysis data for the trialkylbenzyl chlorides-2,4,6-trimethyl-, 2,4,6-tri-i-propyl-, 2,4-di-t-butyl-6-methyl-, and 2,4,6-tri-t-butylbenzyl chloride indicated an unexpected high reactivity for the latter compound. The abrupt increase in ΔS* for this compound is attributed to steric hindrance to solvation at the reaction site and steric acceleration is offered as an explanation for the unusual reactivity of this compound.
Isotope Effect Studies on Elimination Reactions. VIII. The Mechanism of the 1,3-Elimination Reaction of 3-Phenylpropyltrimethylammonium Iodide with Amide Ion in Liquid Ammonia
Authors: Westaway K. C. , Bourns A. N.
Published: May 2006

Reaction of 3-phenylpropyltrimethylammonium iodide with potassium amide in liquid ammonia at −55 °C was found to give concurrent 1,3-elimination forming phenylcyclopropane and 1,2-elimination forming 3-phenylpropene and cis- and trans-1-phenylpropene. Deuterium tracer studies on the salt labelled at C-3 established that neither a carbene nor an ylide are intermediates in the 1,3-elimination process. Isotopic exchange at C-3 was shown to accompany the reaction of the deuterated salt in ordinary ammonia, but it was not detected in the reaction of unlabelled salt in ammonia-d3. A nitrogen isotope effect, k14/k15, of 1.022 ± 0.001 was found for the 1,3-elimination, while the corresponding hydrogen isotope effect, estimated from the effect of isotopic substitution on the 1,3- and 1,2-elimination ratio, was shown to exceed 20. The hydrogen isotope effect for the disappearance of undeuterated and deuterated salts (elimination and exchange) was approximately 7.4. These observations, as well as the influence of deuterium substitution in both the quaternary salt and the solvent on the relative rates of 1,3- and 1,2-elimination, have been shown to be in accord with an Elcb mechanism in which the rate constants for the conversion of the intermediate 3-carbanion to 1,3-elimination product and for return to reactant by abstraction of a proton from ammonia are of the same order of magnitude.
Chemical Shift. VII. The Long-range Shielding Effects of the Cyano Group
Authors: ApSimon J. W. , Beierbeck H. , Todd D. K.
Published: May 2006

Using the methods described in parts I–VI of this series, we have examined the long-range shielding effects of the cyano group upon the C-18 and -19 methyl protons in several cyano-steroids and the ring protons in 2-endo- and 2-exo-cyanonorbornenes.It was found that the most important shielding mechanism of the cyano group is its electric field effect, with the magnetic anisotropy effect making at most a minor contribution to the screening. However, only in the cases of the cyano-steroids was good agreement obtained between the calculated and the experimental shifts.
Photoelectron Spectra of Some Bromoethylenes and 2-Bromopropene
Authors: Chadwick D. , Frost D. C. , Katrib A. , McDowell C. A. , McLean R. A. N.
Published: May 2006

The photoelectron spectra of vinyl bromide, cis- and trans-1,2-dibromoethylene and 2-bromopropene have been obtained. Interaction of the bromine "lone pair" electrons with those in the C=C π bond is discussed. The assignments are considered in relation to the chloroethylenes. The spectra provide experimental evidence for a proposal by Klasson and Manne that previous studies have reported too many I.P.'s for some of the chloroethylenes.
Optical and Thermal Bleaching of Trapped Electrons in Aliphatic Amine Glasses
Authors: Noda Shoji , Fueki Kenji , Kuri Zen-ichiro
Published: May 2006

An optical bleaching study has been made of trapped electrons in γ-irradiated aliphatic amines at −196 °C. The results indicate that the optical absorption of the trapped electrons in the amines is attributed to optical transitions to both bound excited states and a continuum state. The thermal decay of the trapped electrons has been studied by the e.s.r. technique at temperatures above −196 °C. It has been found that the line width of the e.s.r. spectra of the trapped electrons in some of the amines changes on warming.
Reactivity of Organic Halides toward the Mobile Electron in Methyltetrahydrofuran Glass
Authors: Kato Noriyuki , Fueki Kenji , Kuri Zen-ichiro
Published: May 2006

The relative reactivity of a number of organic halides with the mobile electron produced in γ-irradiated methyltetrahydrofuran glass at 77 °K has been studied by a scavenger competition kinetics. It has been found that for the organic halides there exists a correlation between the relative electron capture cross section in the glassy matrix and the heat of reaction for dissociative electron capture estimated from gas phase data.
Mass Spectrometry in Structural and Stereochemical Problems. CCXVII. Electron Impact Promoted Fragmentation of O-Methyl Oximes of some α,β-Unsaturated Ketones and Methyl Substituted Cyclohexanones
Authors: Sheikh Younus M. , Liedtke Raymond J. , Duffield A. M. , Djerassi Carl
Published: May 2006

Deuterium labeling and high resolution mass spectrometry have been utilized to delineate the modes of mass spectrometric fragmentation of O-methyl oximes of α,β-unsaturated ketones and methyl substituted cyclohexanones. α,β-Unsaturated ketone and 2- and 4-methylcyclohexanone O-methyl oxime ether derivatives fragment upon electron impact in a manner reminiscent of the carbonyl derivatives from which they were prepared. However, several fragmentation sequences characteristic of the O-methyl oxime ether group were observed.
Sulfur-free Penicillin Derivatives. I. Functionalization at C-5
Authors: Wolfe Saul , Lee Wha Suk , Kannengiesser Gérard , Ducep Jean-Bernard
Published: May 2006

Direct chlorination of an anhydropenicillin produces a sulfur-free dichloride in which the two C—S bonds are replaced by two C—Cl bonds. The reaction is general for anhydropenicillins and proceeds with predominant retention of configuration at C-5 except in the case of anhydro-6-phthalimidopenicillin, which gives variable stereochemical results.Hydrolysis of the COCl function to COOH, conversion of the acids or acid chlorides to methyl, t-butyl, and benzhydryl esters, and regeneration of the acids from the latter two esters are described.Nucleophilic substitution at C-5 of these compounds proceeds smoothly and with inversion of configuration. The rate of the reaction depends on the C-6 substituent in the direction H2N > acylamino > phthalimido.
INDO Molecular Orbital Calculations of Nitrogen–Proton Spin–Spin Coupling Constants Over Two and Three Bonds. Effects of Lone-pair Orientation, of Dihedral Angles, and of Protonation
Authors: Wasylishen R. , Schaffer T.
Published: May 2006

Molecular orbital theory at the INDO level of approximation is used to calculate the Fermi contact contribution to two-bond and three-bond nitrogen–proton coupling constants for a wide variety of compounds. The dependence of calculated N,H coupling constants upon the spatial orientation of the nitrogen lone-pair is examined for selected molecules. For both saturated and unsaturated compounds the calculated 2J(15N,H) is large and negative when the lone-pair is oriented cis to the proton, and is small and of either sign when the lone-pair lies trans to the proton. Calculated 3J(N,H) depends both on the orientation of the nitrogen lone-pair and on the HCCN dihedral angle. Computed 2J(N,H) and 3J(N,H) generally follow the experimentally known substituent and structural effects. It is suggested that observed phosphorus–proton coupling constants in tervalent phosphorus compounds are dependent on lone-pair orientation in a manner analogous to the corresponding nitrogen–proton coupling constants. The influence of the nitrogen lone-pair orientation on geminal proton–proton coupling constants in methylamine is computed and compared with experiment. Calculated barriers to pyramidal inversion and methyl group rotation are in reasonable agreement with available experimental data.
A Low Temperature Dielectric Cell and the Permittivity of Hexagonal Ice to 2 K
Authors: Gough S. R.
Published: May 2006

The limiting high frequency permittivity ε∞ of hexagonal ice, measured using a coaxial three terminal dielectric cell designed to minimize errors arising from differential thermal contraction, varies from 3.093 ± 0.003 at 2 K to 3.15 ± 0.02 at 200 K. The result is discussed in relation to the translational lattice vibrations and a comparison is made with other ices.
Etude cinétique des systèmes Cu(II)•Adénosine et Cu(II)•D-Ribose
Authors: Boivin G. , Zador M.
Published: May 2006

The kinetics of the formation and dissociation of Cu(II) complexes of adenosine have been determined in acidic and basic medium. In acidic medium, the complex is formed between the Cu(II) and the adenine base and the kinetic parameters have been obtained in this case using a temperature jump method. In basic medium, only the dissociation of the complexes could be studied by a stopped-flow method, by addition of EDTA or strong acid solutions. In these complexes, Cu(II) is bridged with ribose hydroxyls. Finally, D-ribose has also been studied for comparison in the same conditions. The mechanism of these reactions is discussed.