bluuebunny/crossref_metadata_2025 huggingface dataset:
Fluorine N.M.R. Spectra of Sulfur, Phosphorus, and Silicon Fluorides: Hydrolysis and Intra- and Intermolecular Mechanisms of Fluorine Exchange
Authors: Gibson James Andrew , Ibbott David George , Janzen Alexander F.
Published: May 2006

The fluorine n.m.r. spectra of SF4, [(CH3)2CH]2NSF3, PF5:O(C2H5)2, SiF5−, SiF5:NH3−, and SiF5:HN(C2H5)2− have been recorded after treatment of glassware and reagents with [(CH3)3Si]2NH to remove H2O and HF impurities. A mechanism of intramolecular and intermolecular fluorine exchange, involving Lewis acid – Lewis base interaction and rapid equilibration of five and six coordinate geometries, is proposed.
α-Pyrones. II. The Synthesis of α-Pyrones From α,β-Unsaturated Aldehydes. Part II
Authors: Engel Ch. R. , Krassny A. F. de , Bélanger A. , Dionne G.
Published: May 2006

It is shown that the reaction of acrolein with bromomalonate in the presence of an alkali alkoxide, leading to a 2-formylcyclopropane-1,1-dicarboxylate, may be applied to the steroid series; thus, a 20-methylene 21-aldehyde gives in excellent yield the corresponding cyclopropane derivative. The possibility of converting such systems to α-pyrones was investigated in the case of the acrolein adduct, diethyl 2-formylcyclopropane-1,1-dicarboxylate. While its cyclopropane ring could not be isomerized to an olefin with aluminum chloride or by reactions catalyzed by transition metals and while photolysis led to a dihydrofuran derivative, pyrolysis in high vacuum at 550–575° afforded directly an α-pyrone, ethyl coumalate. Evidence is put forward for the intermediacy of 3-ethoxycarbonyl-α-pyrone in this reaction.
4-Chlorothiane 1-Oxide Conformations: a Large 1,4-Dipolar Effect
Authors: Wood Gordon , Barker C. C. , Kligerman Anne
Published: May 2006

Conformational ratios of cis- and trans-4-chlorothiane 1-oxide were obtained through low temperature n.m.r. studies. The former compound exists predominantly in the S—O axial form (74:26) and the latter almost exclusively in the S—O axial form (at least 96:4). The cis compound approximates additive behavior; the large discrepancy in the trans compound is consistent with a 1,4-dipolar interaction.
Conformational Study of N-Methyl-5,6-dihydro-7H,12H-dibenz[c,f]-azocine by Nuclear Magnetic Resonance Spectroscopy
Authors: Renaud Roger N. , Layton Robert B. , Fraser Robert R.
Published: May 2006

A study of the n.m.r. spectra of N-methyl-5,6-dihydro-7H,12H-dibenz[c,f]azocine, its deuterated derivative, and its conjugate acid in deuteriochloroform and in trifluoracetic acid at 27 and at −62° has shown that the molecule prefers the rigid "crown" conformation. From the equilibrium constant for the equilibrium flexible [Formula: see text] crown at 27 and at −62°, ΔH and ΔS values of −3.2 ± 0.5 kcal/mol and −7 ± 3 e.u. respectively were determined, indicating the preference for the crown conformer. A barrier to interconversion of the flexible to crown form at −62° was determined to be 15.3 ± 0.3 kcal/mol.These parameters provide the first experimental data pertinent to the conformational properties of the 1,4-cyclooctadiene system.
Arrhenius A Factors of Unimolecular Decomposition of Alcohols Formed by Insertion of O(1D2) Atoms into the CH Bonds of Paraffins
Authors: Mintz K. J. , Cvetanović R. J.
Published: May 2006

The Arrhenius A factors of unimolecular decomposition of alcohols have been calculated approximately by a simple formula from the experimental rate constants of decomposition of "chemically activated" alcohols (formed by insertion of O(1D2) atoms into the CH bonds of paraffins) and the structural and thermochemical properties of the alcohols. The more exact R.R.K.M. method of calculation is shown to be in reasonable agreement with the simpler method for CH3OH decomposition. The resultant large positive entropies of activation are consistent only with involvement of "loose" activated complexes in the unimolecular decomposition of alcohols.
A Quantitative Investigation of the Ozonolysis Reaction. XVIII. A Kinetic Study of the Ozone Attack on Phenylethylenes
Authors: Henry H. , Zador M. , Fliszár S.
Published: May 2006

Absolute reaction rates for the ozonolysis of phenylethylenes in the liquid phase indicate: (i) a Hammett dependence, with [Formula: see text], for the ring-substituted trans stilbenes, (ii) a solvent effect, whereby the ozone attack is promoted by polar solvents, and (iii) no temperature effect between 15 and 35 °C, thus indicating [Formula: see text].
Photoionisation en milieu rigide. Evolution de la fonction de distribution des électrons piégés autour des cations
Authors: Bullot Jacques , Ceccaldi Dominique , Gallais Odile
Published: May 2006

A kinetic model for describing isothermal recombination luminescence (ITL) of trapped electrons in a rigid medium is proposed. Assuming that cavities in the glass are pre-existing, a continuous trap-depth distribution is generated from the long-range Coulomb field of the cation. ITL decay kinetics simply is the superposition of an infinite sum of first order decays of correlated electrons. This model is able to fit experimental decays within ± 3%. Numerical solutions are tested by introducing a Gaussian trapped electron distribution function (parameters: rmax Å and width b Å) and keeping the formerly found trap parameters: half-width L = 1.70 Å and lifetime at infinity [Formula: see text]. This model is used for studying how the trapped electron distribution function is shifted when experimental conditions are altered. (1) During the glass isothermal relaxation. The initial values rmax = 32.0 Å, b = 6.2 Å found just after cooling are shifted to rmax = 40.0 Å and b = 9.0 Å, 24 h after cooling. The model indicates that the total number of trapped electrons is steadily decreasing as long as the relaxation is proceeding. (2) As a function of the u.v. irradiation period. The trapped electron distribution function is pushed away from the cationic center when tirrad is increasing. Near the saturation plateau the distribution function is no longer shifted; only the total number of trapped electrons is increased. (3) As a function of u.v. light intensity. By integrating as a function of r the trapped electron distribution function at time t = 0 when u.v. light is turned off, the resulting area, which is proportional to the total number of trapped electrons, is shown to be proportional to the square of the light intensity. In others words with this model the well-known one-electron two-photon ionization law is recovered. This is to be considered as a test of the model self-consistency.
Spectrométrie de masse des cyclohexanones gem-diphénylées. I. Localisation de la charge positive
Authors: Fortin Claude J. , Forest M. , Vaziri C. , Gravel D. , Rousseau Yves
Published: May 2006

Using gem-diphenyl cyclohexanones as models, the relative importance of gem-diphenyl υs. carbonyl functions as possible site of localized charge initiating and directing fragmentation has been determined. The influence of each function is recognized by studying molecules where this group has been isolated. The results show that the carbonyl does not play an important role in the gem-diphenyl cyclohexanones decomposition under electron impact. Furthermore the ionization potentials of the molecules containing both functions are very close to those of the corresponding molecules comprising the gem-diphenyl function exclusively.
Photochemical Studies. XVI. Second Moment Analysis of the Electron Spin Resonance Spectra of Radicals Formed by Ultraviolet Irradiation of 9-Phenylacridine and of Acridine
Authors: Castellano Azélio , Catteau Jean-Pierre , Lablache-Combier Alain , Allan Guy
Published: May 2006

The irradiation of 9-phenylacridine in methanol, ethanol, or ether leads to the formation of the 9-phenylacridinyl radical. In methanol-d4, the radical formed is the singly deuterated analog. The structure of these radicals, which exhibit a hyperfine structure in their e.s.r. spectra measured at 233 °K, is supported by simulation of the spectra using calculated spin densities. The agreement between the experimental and theoretical second moment values of the deuterated radical indicates that the parameters previously chosen for the calculation of the theoretical second moments of pyridinyl-type radicals derived from six-membered ring azaaromatics are suitable and that the second moment method can be used in studies of radicals of this type. We conclude that acridine irradiated in methanol-d4 leads to the formation of the singly deuterated acridinyl radical.
Equilibria of the Simultaneously Existing Multiple Species in the Copper(II)–L-Histidine System
Authors: Kruck Theo P. A. , Sarkar Bibudhendra
Published: May 2006

The complete species distribution and the stability constants of the complex species in the Cu(II)–L-histidine system have been worked out for the pH range 2–11. The method of "analytical potentiometry" has been applied successfully to this system having excess ligand with respect to Cu(II) ion. The equilibria of three systems of Cu(II) (M) and L-histidine (H3A) in molar ratios of 1:2, 1:4, and 1:8 were investigated by this technique in 0.15 M NaCl at 25°. The following species were detected in this system: MHA, MA, MH2A2, MHA2, MA2, MH−1A2, MH−1A, and M2H−2A2. Statistical analysis on the numerical results has been performed and is given as standard deviation together with the individual values for the stability constants.
Reaction Kinetics of Ground State Fluorine, F(2P), Atoms. I. Measurement of Fluorine Atom Concentrations and the Rates of Reactions F + CHF3 and F + Cl2 using Mass Spectrometry
Authors: Clyne Michael A. A. , McKenney Donald J. , Walker Ronald. F.
Published: May 2006

Reactions of F(2P) atoms generated by a 2.45 GHz discharge in dilute F2 + He mixtures have been studied mass spectrometrically with a beam inlet system from a fast flow reactor. F atom concentrations have been measured from the consumption of Cl2 in the simple and extremely rapid bimolecular reaction 1[Formula: see text]k1 was determined to be (1.1 ± 0.3) × 10−10 cm3 molecule−1 s−1 at 300 °K.Rate measurements for the reaction 2, which forms CF3 radicals, are reported, over the range 301 to 667 °K,[Formula: see text][Formula: see text]A less detailed survey of the rates at 298 °K of a series of reactions of F with H2, CH4, CH3Cl, CH2Cl2, and CHCl3, is also given; in these cases, the source of F was a discharge in CF4 + Ar, and [F] was measured by titration with ClNO.
Di-imide: Some Physical and Chemical Properties, and the Kinetics and Stoichiometry of the Gas-phase Decomposition
Authors: Willis C. , Back R. A.
Published: May 2006

Preparation of di-imide by passing hydrazine vapor through a microwave discharge yields mixtures with NH3 containing typically about 15% N2H2, estimated from the gases evolved on decomposition. The behavior of the mixture (which melts at −65 °C) on warming from −196 to −30 °C suggests a strong interaction between the components. Measurements of magnetic susceptibility and e.p.r. experiments showed that N2H2 is not strongly paramagnetic, which with other observations points to a singlet rather than a triplet ground-state.Di-imide can be vaporized efficiently, together with NH3, by rapid warming, and the vapor is surprisingly long-lived, with a typical half-life of several minutes at room temperature. The near-u.v. (3200–4400 Å) absorption spectrum of the vapor was photographed; it shows well-defined but diffuse bands, with εmax = 6(± 3) at 3450 Å.Di-imide decomposes at room temperature in two ways:[Formula: see text][Formula: see text]Formation of NH3 was not observed but cannot be ruled out. The decomposition of the vapor is complicated by a sizeable and variable decomposition that occurs rapidly during the vaporization. The stoichiometry of this and the vapor-phase decomposition depends on total pressure and di-imide concentration. The kinetics of the decomposition of the vapor were studied from 22 to 200 °C by following the disappearance of N2H2 by absorption of light at 3450 Å, or the formation of N2H4 by absorption at 2400 Å, and by mass spectrometry. The kinetics are complex and can be either first- or second-order, or mixed, depending on surface conditions. The effect of olefin additives on the decomposition was studied, and is also complex.Mechanisms for the decomposition are discussed, including the possible role of trans-cis isomerization. The relatively long lifetime found for di-imide in the gas phase suggests that it may be an important intermediate in many reactions of hydronitrogen systems.
The Isomeric Enol Acetates of Acetylacetone. Evidence for an Unusual Stabilizing Interaction between cis Acetyl and Acetoxy Groups
Authors: Awang Dennis V. C.
Published: May 2006

The configuration and conformation of the isomeric enol acetates of acetylacetone have been elucidated. P.m.r. shift data obtained by the use of tris(1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octanedionato)europium(III) (Eu(fod)3) allow assignment of the (S)-cis conformation to both isomers. The remarkable stability of the isomer having acetyl cis to acetoxy is attributed to neighboring group interaction, a rationale consistent with p.m.r. spectroscopic data.
Spectrum, Kinetics, and Radiation Chemical Yield of Solvated Electrons in Hexamethylphosphoric Triamide
Authors: Shaede Eric A. , Dorfman Leon M. , Flynn Garry J. , Walker David C.
Published: May 2006

The spectrum, yield, and kinetics of solvated electrons in hexamethylphosphoric triamide were investigated by the pulse radiolysis method. The optical absorption band is in the infrared with a maximum at 2200 ± 100 nm. The molar absorptivity at this maximum is (3.2 ± 0.5) × 104 M−1 cm−1, and the oscillator strength for the transition is estimated to be f = 0.7 ± 0.2. A free ion yield of G(es−) = 2.3 + 0.4 solvated electrons/100 eV was determined from the observed yields of anthracene and pyrene radical anions formed by electron attachment.Kinetic studies provided values of the rate constants for the reaction of solvated electrons with anthracene and N2O. The decay mechanism of the solvated electrons in the absence of added solutes was found to be complex, and the half-life (in the range of 2 to 50 μs) was dependent on experimental conditions. A second transient species, absorbing at wavelengths below 500 nm, was observed but not identified. In solutions containing bromide ion the species Br2− was observed. The pulse radiolysis of stable solutions of es−, formed by dissolving sodium metal in HMPA, is also reported.
Kinetics of the Reaction of Nickel(II) and 2,2′-Bipyridine in Ethanol
Authors: Sanduja M. L. , Smith W. MacF.
Published: May 2006

The kinetics of formation of the monobipyridine complex of nickel(II) in ethanol has been studied with stopped-flow methods over the temperature range 7 to 35 °C. The value of the second order rate constant kf at 25 °C of 6.6 × 10−3M−1 s1 and the values of ΔH≠ (10.1 ± 1.0 kcal mol−1) and of ΔS≠ (−7.3 ± 3.4 cal deg−1 mol−1) are close to the corresponding values for ethanol exchange on nickel(II) and suggest that the mechanism is dissociative interchange. However the difference in the values of the kinetic parameters of this reaction and those previously reported for the reactions involving the chemically similar phenanthroline imply a degree of ligand specificity for the reactions in ethanol which is considerably larger than is the case for reactions in water and methanol and that a common Id mechanism with monodentate formation being rate controlling is not applicable to both reactions.
Mutual Solubilities of Hydrocarbons and Water at 0 and 25 °C
Authors: Polak Jiri , Lu Benjamin C.-Y.
Published: May 2006

Mutual solubilities of 14 paraffinic and 6 aromatic hydrocarbons and water were determined experimentally at 0 and 25 °C. The solubilities are generally smaller at 0 than at 25 °C except the solubilities of paraffins in water which are larger at 0 than at 25 °C. The coefficients of the Redlich–Kister equation were evaluated from the experimental data and correlated as a function of molar volume of liquid hydrocarbons and group contributions. The correlation allows calculation of the mutual solubilities of paraffinic and aromatic hydrocarbons and water at 0 and 25 °C from the knowledge of the molar volume of liquid and the contribution of their component groups.
Thermodynamic Properties of Cyclopentanol + p-Dioxane Mixtures at 25 °C
Authors: Anand S. C. , Grolier J.-P. E. , Kiyohara Osamu , Benson G. C.
Published: May 2006

Excess enthalpies, excess volumes, and total vapor pressures were measured for cyclopentanol + p-dioxane mixtures at 25 °C. The method of Barker was used to calculate vapour–liquid equilibria and excess Gibbs free energies from the vapor pressure results. A comparison with results (from the literature) for the systems cyclohexane + cyclopentanol and cyclohexane + p-dioxane indicates that the excess thermodynamic properties of cyclopentanol + p-dioxane mixtures arise primarily from the disruption of the structure of the p-dioxane solvent.
The Quenching of O2(1Σg+) by Aliphatic Hydrocarbons
Authors: Davidson J. A. , Ogryzlo E. A.
Published: May 2006

Rate constants for the quenching of O2(1Σg+) in the gas phase have been determined for 12 aliphatic hydrocarbons. The values are discussed in terms of a mechanism in which the magnitudes of the rate constants are determined by the abilities of the quenchers to become vibrationally excited when O2(1Σg+)is relaxed to O2(1Δg).The resulting equations are tested quantitatively by relating the rate constants to the absorption spectra of the quenchers at the frequencies of the O2(1Σg+−1Δg) transition.
The Synthesis of Four Possible in vitro Metabolites of the Hallucinogen 1-(2,5-Dimethoxy-4-methylphenyl)-2-aminopropane (DOM)
Authors: Coutts Ronald T. , Malicky Jerry L.
Published: May 2006

The synthesis of four possible in vitro metabolites of the hallucinogen 1-(2,5-dimethoxy-4-methylphenyl)-2-aminopropane (DOM) is described. These compounds, 1-(2,5-dimethoxy-4-methylphenyl(-2-propanone, the corresponding oxime, 1-(2,5-dimethoxy-4-methylphenyl)-2-propanol, and 1-(2,5-dimethoxy)-4-methylphenyl-2-(hydroxylamino)propane, could be products of side chain metabolic oxidation of DOM.
Strong Crystalline Field Perturbation Calculations for d3, d7 Penta-Coordinate Complexes. II. The Square Pyramid
Authors: Varga Judith A. , Becker Clifford A. L.
Published: May 2006

Crystal field calculations for d3, d7 square pyramidal complexes are carried out via the strong field formalism and in the limit of zero spin-orbit coupling. The field produced by the lone axial ligand is treated as an integral part of the crystal field potential. In the ionic model approximation the three crystal field parameters: Dq, Ds, and Dt; depend markedly on the angle of distortion, β, defined as that portion of the La—M—Lb bond angle in excess of 90°. The square pyramidal d3 symmetry eigenfunctions are constructed from the one-electron crystal field eigenfunctions. Spin is only implicitly included, but both types of doublet wavefunctions are identified. The crystal field matrix in parametric form is strictly diagonal, but Coulombic interactions connect states arising from different strong field configurations. Coulombic calculations are performed in terms of the Slater–Condon–Shortley parameters: F0, F2, and F4; then converted to the Racah parameters: A, B, and C, The complete (crystal field and Coulombic) perturbation matrices are used to interpret the spectroscopic properties of a strong field Co(II) square pyramidal complex. Both the symmetry and multiplicity of the ground state are dependent on β. An energy level diagram showing all doublets and quartets is calculated for β = 0°. Partial energy level diagrams are also given depicting behavior of the doublet and quartet states, individually, as functions of β. As β increases the crystal field bands shift to lower energy and become more clustered. Current experimental applications are also briefly cited.
Structural Investigation of Sigma Complexes of Aromatic Amines with 1,3,5-Trinitrobenzene
Authors: Buncel Erwin , Webb John G. K.
Published: May 2006

Reaction of the 1,3,5-trinitrobenzene (TNB) – methoxide ion adduct 1 with a series of substituted arylamines in dimethyl sulfoxide (DMSO) solution yields new 1,3,5-trinitrobenzene – aromatic amine σ-complexes (2). The parent TNB–anilide complex is also obtained in the reaction of TNB with potassium anilide in DMSO. Identification of the complexes is effected by n.m.r. and visible spectroscopy. The n.m.r. parameters of the complexes are influenced in characteristic manner by substituents in the aryl-amine moiety. An analysis of electronic and structural factors in these systems is given, with emphasis on the following aspects: structural implications of NH–Hβ′ coupling; aromatic protons on the arylamine moiety; amino protons in free and complexed arylamines.
The Quenching of Type II Photodecomposition of 2-Pentanone in n-Hexane Solution by Metal Chelates
Authors: Flood J. , Russell K. E. , Carlsson D. J. , Wiles D. M.
Published: May 2006

The effect of certain metal chelates on the yield of acetone from the photodecomposition of 2-pentanone in n-hexane solution has been studied. The chelates act as quenchers but the slopes of the Stern–Volmer plots are lower than the slope observed for cis-1,3-pentadiene. These additives protect solid polyolefins against photodegradation but it is unlikely that the mechanism primarily involves quenching of carbonyl triplets.The quantum yield of acetone production in the type II decomposition of 2-pentanone in n-hexane solution is 0.20 ± 0.01; the triplet state lifetime of 2-pentanone is 2.3 × 10−8 s.
Isotope Effect Studies on Elimination Reactions. IX. The Nature of the Transition State for the E2 Reaction of 2-Arylethylammonium Ions with Ethoxide in Ethanol
Authors: Smith P. J. , Bourns A. N.
Published: May 2006

Kinetic isotope effects have been determined for the E2 reaction of some 2-arylethyltrimethyl-ammonium ions with ethoxide in ethanol at 40°. The nitrogen effect, (k14/k15 − 1)100, decreased with increasing electron-withdrawing ability of the para substituent; i.e. 1.37, 1.33, 1.14, and 0.88 for p-OCH3, p-H, p-Cl, and p-CF3, respectively. Furthermore, the primary hydrogen–deuterium isotope effects increased for the same substituents, respectively; i.e. kH/kD = 2.64, 3.23, 3.48, and 4.16. A large positive ρ value of 3.66 was found as well as a small secondary α-deuterium effect of 1.02 for p-H. In addition, the nitrogen isotope effect decreased with increasing strength of the abstracting base for the reaction of ethyltrimethylammonium ion; i.e. 1.86 and 1.41 at 60° for reaction with EtO−–EtOH and t-BuO−–t-BuOH, respectively. The results are discussed in terms of recent theoretical treatments of the effect of base, substituents, and nature of the leaving group on the nature of the transition state for an E2 process. The conclusion is reached that any structural change which causes one bond (C—H) to be weakened more at the transition state will have a corresponding effect on the other bond [Formula: see text]
Excess Volumes of Binary Mixtures of Alcohols in Methylcyclohexane
Authors: Rao Murari Venkata Prabhakara , Naidu P. Ramachandra
Published: May 2006

Excess volumes of binary mixtures of alcohols in methylcyclohexane have been determined at 30.0 and 40.0 °C, using a modified dilatometer of Brown and Smith. The systems include: (I) 1-propanol – methylcyclohexane, (2) 1-butanol – methylcyclohexane, (3) 1-pentanol–methylcyclohexane, and (4) 1-hexanol–methylcyclohexane. The VE values are found to be positive over the entire range of composition in all the four systems and the values are interpreted on the basis of the structure-breaking effect of methylcyclohexane.
Mechanism of Hydrogen Peroxide Pyrolysis
Authors: Tessier André , Forst Wendell
Published: May 2006

The pyrolysis of hydrogen peroxide was followed mass spectrometrically, under conditions such that a steady-state concentration of the HO2 radical equal to or exceeding 1/100th of the concentration of hydrogen peroxide would have been detected. The actual steady-state concentration of HO2 in a reacting mixture was found to be below the detection limit, from which it is concluded that the simplest mechanism that provides an entirely adequate quantitative description of the pyrolysis is[Formula: see text]
Reactions of Functionalized 1,3-Dipoles
Authors: Lown J. W. , Landberg B. E.
Published: May 2006

A new synthetic approach to the formation of 5–5, 5–6, 5–5–5, and 6–5–6 fused heterocycles employing cycloadditions with functionalized dipoles is described and its scope and utility explored through representative examples. The regiochemistry and stereochemistry of the additions is established by specific deuterium labelling, n.m.r. spectroscopy, and by chemical means.
The Microwave Spectrum of Trifluoromethyl Hypofluorite
Authors: Buckley P. , Weber J. P.
Published: May 2006

The microwave spectrum of trifluoromethyl hypofluorite (CF3OF) has been analyzed in the region 8–40 GHz. Only μa R-type transitions were observed despite a careful search and using double-resonance techniques. These determine the following rotational constants: A = 5600 ± 100, B = 3108.13 ± 0.02, C = 3049.25 ± 0.02 MHz. The dipole moments determined from Stark effect measurements are μa = 0.30 ± 0.02, μb = 0.10 ± 0.06, μc = 0 D. The υ = 1 state of the CF3 torsion has also been measured; relative intensity measurements lead to a potential barrier of 3.9 kcal/mol, somewhat higher than the electron diffraction results.
Far Infrared Spectra of Crystalline Iodine Monobromide and Iodine Monochloride
Authors: Leung Hsiao-Chian , Anderson Anthony
Published: May 2006

Infrared spectra, in the range 20–400 cm−1, of thin polycrystalline films (at 80 °K) of iodine monobromide and the β-form of iodine monochloride have been recorded. For IBr, the intramolecular stretching region shows two peaks separated by 16 cm−1 and shifted appreciably from the gas phase value, indicating strong intermolecular interactions. Four lattice modes are also observed and assigned in accordance with group theoretical predictions. For β-ICl the spectrum of the stretching region confirms the presence of two distinct molecules with different bond lengths. The complexity of the ICl structure prevents an assignment of the ten observed lattice absorptions.
An Electron Spin Resonance Study of Radicals Formed by γ-Irradiation of 1-Substituted 5-Nitro-amino and 5-Nitroso-aminotetrazoles
Authors: Catton Richard C. , Butler Richard N.
Published: May 2006

γ-Irradiation of 1-methyl-5-methylnitro-aminotetrazole 1 and 1-methyl-5-nitro-aminotetrazole 2 resulted in cleavage of the exocyclic N—N bond giving only one detectable radical (NO2•) in each case. The stability and motion of the NO2• radicals formed in these systems was studied. The NO2• radical obtained from compound 1 was immobile in the lattice while that obtained from compound 2 was rotating about the y-axis. Irradiation of 1-methyl-5-methyl-nitroso-aminotetrazole 3 and 1-phenyl-5-nitroso-aminotetrazole 4 did not give a simple N—N bond cleavage and radicals which could not be fully identified were encountered. The radical obtained from compound 3 appeared to be a nitroxide radical and that obtained from compound 4 appeared to arise from electron capture by the nitrosamino moiety.
Etude conformationnelle des alcényl phénylcétones par spectrographies infrarouge, ultraviolette et par l'utilisation de l'effet Overhauser nucléaire et de complexe de lanthanide Eu(dpm)3 en résonance magnétique nucléaire
Authors: Thoai Nguyen , Minh-Chau Trinh-
Published: May 2006

By the use of i.r., u.v. and n.m.r. (n.O.e. and europium chelates) we have shown that a series of phenyl ketones (R1R2C=CR3—CO—C6H5) exist within the s-cis conformation probably because of the steric bulk of the benzene ring. When these ketones have an alkyl substituent (R3=Me, Et) on the carbon atom α to the carbonyl group, the molecule is no longer planar. The molecular torsion in this case is not around the CO—C6H5, bond but rather at the CO—C= bond. The resulting dihedral angle is about 65°. We propose a tabular method which together with the use of Eu(dpm)3 allows rapid determination of the preferred conformation of non rigid α,β-unsaturated ketones and in the case of non-planar conformations allows the estimation of the dihedral angle between the C=C and C=O chromophores. [Journal translation]
Photochemistry of NOx and HNOx Compounds
Authors: Johnston Harold S. , Graham Richard
Published: May 2006

Cross sections for absorption of radiation between 190 and 700 nm are given for N2O, NO2, NO3, N2O4, N2O5, HNO2, and HNO3. The quantum yields and the primary products of photolysis of each of these substances are discussed. This article includes spectral data obtained in this laboratory for NO2, NO3, N2O3, HNO3, and HNO3 and it includes spectral data from the literature for N2O and N2O4. The quantum yields are based both on results from this laboratory and from the literature.
Stratospheric Aerosols Physicochemistry
Authors: Bricard J. , Vigla D.
Published: May 2006

The stratospheric aerosol layer, a few kilometers thick and centered a few kilometers above the tropopause, is currently believed to be composed of Aitken nuclei, composed principally of ammonium sulfate, and large particles greater than 1 µ; particles larger than 5 µ contain little sulfate and are believed to be of meteoritic origin.With acceptance of the direct or indirect terrestrial origin of the stratospheric ammonium sulfate particles, three processes can be suggested for their occurrence in the stratosphere: (1) coagulation of stratospheric Aitken nuclei previously formed in the troposphere; (2) oxidation of SO2 of terrestrial origin in the stratosphere to H2SO4 followed by nucleation and internal growth; and (3) reactions involving hydrous stratospheric ions such as (H3O)+.n(H2O) which act as primary nuclei and facilitate reaction of gaseous constituents of terrestrial origin such as NH3, O2, and HCl.
Climatic Effects of Stratospheric Chemistry
Authors: Dickinson Robert E.
Published: May 2006

The paper reviews the present understanding of the climatic effects of stratospheric chemical composition within the general framework of climate modeling. The modulation of radiative fluxes by carbon dioxide, ozone, and aerosols provides an input to climate models. It is difficult observationally to distinguish between climate variation forced by changes in these or other external parameters and internal noise of the system. Indeed, ozone concentration is so coupled to atmospheric dynamics that it should be regarded as one of the internal variables. One-dimensional vertical and latitudinal climate models are described, and their conclusions as to tropospheric and stratospheric climate change discussed.
Kinetics of Dehydration of Aromatic Aldehydes Determined by the Rotating Disc Electrode Technique
Authors: Barradas R. G. , Kutowy O. , Shoesmith D. W.
Published: May 2006

The rate constant for the irreversible dehydration of a number of aromatic aldehyde hydrates has been measured. The hydrates were generated by constant potential electrolysis of the respective aromatic acid at a rotating disc electrode. The aldehydes are then further reduced to the alcohol. The rate constant can be calculated from the ratio of the concentration of intermediate aldehyde to the total concentration of products.The theory was further extended to include the reverse hydration of the aldehyde to the hydrate and applied in the case of m-chlorobenzaldehyde. A value for the equilibrium constant of K = 1.30 ± 0.25 was obtained for this reaction.
Spectrométrie de masse d'imines aliphatiques
Authors: Leduc Gilles , Rousseau Yves
Published: May 2006

The electron impact induced fragmentation pattern of four aliphatic imines are reported. These are derived from studies involving deuteriated imines and from the observed metastable transitions. The elimination of the R1• radical from [Formula: see text] appears to be preferred provided R1• and R2• are methyl or ethyl radicals. The ionization potentials of the compounds studied have been determined.
A Sequence of Attaching the Unit CH2CH2COCH3 to 2,2,6-Trimethylcyclohexanone
Authors: Schmidt Cirill , Adams Keir Leigh , Fechner Uwe
Published: May 2006

A method is described of joining the 2-oxo-butyl group to a ketone. The sequence is illustrated by the synthesis of dihydro-β-ionone (2) from 2,2,6-trimethylcyclohexanone (1).
A Proton Spin–Lattice Relaxation Study of Molecular Motion in Several Addition Complexes of Trimethylamine and Trimethylphosphine
Authors: Ang T. T. , Dunell B. A.
Published: May 2006

The spin–lattice relaxation times of the solid complexes of trimethylamine with I2, ICl, Br2, BCl3, and BBr3 and the relaxation null times of trimethylphosphine – boron trichloride and – boron tribromide have been measured over a range of temperature by pulsed proton magnetic resonance. A minimum in T1 corresponding to reorientation of the methyl groups about the C—N bonds is observed in each complex, although in the case of Me3, NBr2 the minimum corresponds to a combination of methyl group reorientation and reorientation of the whole Me3N moiety. The complexes with the boron trihalides show a second minimum in T1. These minima have been analyzed in terms of either of two possible motions, reorientation of NMe3 about its threefold axis, or that same motion combined with isotropic molecular tumbling. We favor the interpretation involving the simpler motion. Activation energies have been measured for all the motions. The barriers to reorientation of methyl groups about the C—N bond in the moiety Me3N appear to increase as the thermal stability of the complex decreases.
A Kinetic Study of High Pressure Aqueous Oxidations of Organic Compounds Using Elemental Oxygen
Authors: Taylor Jay E. , Weygandt John C.
Published: May 2006

The high pressure (< 136 atm) and high temperature (< 250°) reactions of elemental oxygen with aqueous solutions of selected soluble alcohols, ketones, and acids have been examined in detail for the first time. Saturated acids and methyl alcohol are not oxidized under the imposed conditions. The end product for the oxidation of ketones and primary alcohols is mainly carbon dioxide at 200 °C; however, appreciable yields of acids are obtained at 250 °C. tert-Butyl alcohol and secondary alcohols form the corresponding ketones which are then further oxidized. Those alcohols and ketones which were studied quantitatively all exhibited second-order kinetics, first order in organic compound and first order in oxygen. The compounds are listed below in the order of decreasing rate at 200°, ΔH≠ in kcal/mol and ΔS≠ in entropy units are noted in parentheses: 2-butanone (16.0, −25) > tert-butyl alcohol (24.2, −9) > cyclopentanone (12.4, −36) > isobutyl alcohol (21.5, −17) > sec-butyl alcohol (23.9, −15) > n-butyl alcohol > (21.3, −22) > acetone (15.1, −37). The alcohols have both higher entropies and enthalpies of activation than the ketones. Two non-chain mechanisms are proposed. (I) A ketone equilibrates with its enol which oxidizes to a metastable oxygenated intermediate. At 250° the intermediate decomposes to an acid or at 200° it is further oxidized to carbon dioxide. (II) Alcohols oxidize by an initial bimolecular mechanism to the corresponding ketone or aldehyde which may then be oxidized further.
The Kinetics of Isotope Effects in a Model Solvolysis System Involving One Optically Active Ion Pair Intermediate
Authors: Vogel P. Christian
Published: May 2006

The derivation of the observed first-order rate constants from the "exact" integrated rate equations for the kinetic scheme of reaction 1 is presented. It is shown that the solvolytic exponential first-order rate constant is a special case of the polarimetric rate constant and that the optical activity of the product is determined by a multiplicative ratio of rate constants for the optically important reactions of the ion pair intermediate. A form of the integrated first-order polarimetric rate equation with a linearly independent parameter set is presented. The functions for the first-order rate constants derived using the steady state approximation are special cases of the functions derived from the exact equations, as are the functions for the first-order rate constants for two systems which involve pre-equilibria followed by a slow product forming step. These functions cannot all be derived one from the other. A differential analysis of observed isotope effects as functions of isotope effects on the rate constants for reactions involving the intermediates is presented.
Conformational Isomerism and Oriented Polycrystal Formation of Dimethyl Carbonate
Authors: Katon J. E. , Cohen Mark D.
Published: May 2006

It has been found that dimethyl carbonate exists in the liquid phase as a conformational equilibrium mixture. The conformers differ by rotation about the C—O bonds. The enthalpy difference of the two conformers is found experimentally to be 2.6 ± 0.5 kcal/mol. Dimethyl carbonate crystallizes in contact with alkali halide windows as an oriented polycrystalline film, as shown by polarized infrared spectra.
Selective-phase Ion Cyclotron Resonance Spectroscopy
Authors: Comisarow Melvin B. , Marshall Alan G.
Published: May 2006

In-phase ("dispersion"), 90° out-of-phase ("absorption"), and "absolute-value" (square root of the sum of the squares of the "absorption" and "dispersion") ion cyclotron resonance (i.c.r.) spectra of CH3+ and CH4+ have been obtained by broad-band frequency-swept r.f. irradiation of an ionized methane sample, followed by broad-band detection, digitization of the transient i.c.r. response, Fourier transformation using a digital computer (1), and application of a linear phase correction across the F.t.-i.c.r. spectrum. The "absorption" spectrum is the same as would be obtained by conventional marginal-oscillator field-sweep i.c.r. detection and provides a means for identifying spurious "foldover" peaks; the "dispersion" response is not observable with a marginal oscillator detector. The principal advantages of the new "absolute-value" display are (1) the signal-to-noise ratio is significantly better than for the conventional "absorption" mode, at the expense of a slight broadening of the i.c.r. spectral line shape; and (2) "absolute-value" display will very likely be the method of choice in frequency-sweep F.t.-i.c.r. spectroscopy (2), in order to circumvent the complicated non-linear phase corrections which may otherwise be required to obtain an "absorption" mode display.
Skeletal and Lattice Vibrations of Crystals of Dihalogenobis(pyridine)zinc(II)
Authors: Wong P. T. T.
Published: May 2006

Detailed measurements of the low-frequency Raman spectra of the crystals of [ZnPy2Cl2] and [ZnPy2Br2] at room temperature, where Py is the pyridine molecule, and the far-infrared spectrum of the crystal of [ZnPy2Cl2] at liquid nitrogen temperature have been made. The vibrational frequencies for the single molecule and for the complete crystal of these two complexes have been calculated and compared with the observed spectra, and the distribution of the potential energy of the normal modes has also been calculated to assist the refinement of the calculation and the interpretation of the spectra. Apparently, the skeletal Zn–ligand vibrations of the individual molecule couple with the lattice vibrations in the crystal, except for the normal modes at 326 cm−1 for [ZnPy2Cl2] and at 250 cm−1 for [ZnPy2Br2] which are dominated by the Zn–halogen stretching vibrations. Reasonably good Zn–ligand stretching force constants were obtained. The nature of the coordination bonds of these complexes has been discussed.
A Kinetic Model of the Accommodation Pumping Phenomenon
Authors: Branton Graham Richard , Ryce Stephen Alan
Published: May 2006

A simple kinetic model of the accommodation pumping phenomenon is developed. This model is consistent with the earlier suggestion that the extent to which specular reflection occurs from smooth Pyrex surfaces is dependent upon the velocity of the atoms. It is shown that the upper limit for the pump ratio (PA/PB) is 2, but that in any real situation this ratio would be less than this value. The model is used to show that the deviation of the thermal transpiration ratio from the ideal value, (T1/T2)1/2, should be the same as the accommodation pumping ratio for the same tubing with the same temperature difference.
Thermodynamique de composés azotés. I. Etude calorimétrique des enthalpies de sublimation des trois acides aminobenzoïques
Authors: Sabbah Raphaël , Chastel Raymond , Laffitte Marc
Published: May 2006

The measurement of enthalpies of sublimation of three aminobenzoic acids was made at 367.35, 376.75, and 389.95 K using a Tian–Calvet microcalorimeter equipped with an effusion cell.From the curves (ΔHsub)m(T) = f(T), it was possible to obtain the values for the standard enthalpies of sublimation of the compounds at 298.15 K: (104.9 ± 1.0), (128.0 ± 3.2), and (116.1 ± 3.7) kJ mol−1, respectively, for the 2-aminobenzoic acid, the 3-aminobenzoic acid, and the 4-aminobenzoic acid.The experimental (ΔHsub0)m (298.15 K) values can be accounted for quantitatively from the various contributions (benzene ring, amine, and' carboxylic group) obtained from similar compounds.With the help of structural data, we have tried to explain the differences between the enthalpies of these compounds.We also report here the calculated saturation vapor pressure of these acids, as well as the mean free path of their molecules, at the three temperatures given above.
Crystal and Molecular Structure of the N-Methyldiethanolaminogallane Dimer, [CH3N(CH2CH2O)2GaH]2
Authors: Rettig Steven J. , Storr Alan , Trotter James
Published: May 2006

Crystals of the N-methyldiethanolaminogallane dimer are orthorhombic, a = 19.112(4), b = 9.947(2), c = 7.709(2) Å, Z = 4, space group P212121. The structure was determined by Patterson and Fourier synthesis and was refined by full-matrix least-squares procedures to a final R of 0.056 for 1477 observed reflections. The structure provides the first1 known crystallographic example of pentacoordinate gallium, the dimerization of MeN(CH2CH2O)2GaH occurring via the formation of a four-membered Ga2O2 ring. The coordination about the gallium is distorted trigonal bipyramidal with an angle of 151.2(4)° between the axial substituents. The mean bond distances are: Ga—N, 2.192(5), and Ga—O, 2.018(2) for axial ligands; Ga—O, 1.847(2), 1.960(8), and Ga—H, 1.41(4) for equatorial ligands; O—C, 1.419(14), C—N, 1.470(7), C—C, 1.520(12), and C—H, 1.00(13) Å. The molecule has C2 symmetry to within experimental error. There are possible [Formula: see text] hydrogen bonds ([Formula: see text] 3.13(1)–3.44(1) Å) in the structure.
121Sb Mössbauer Spectroscopy: Stereochemical Activity of the 5s Electrons in some Sb(III) Halide Complexes
Authors: Ballard Jack G. , Birchall Thomas , Milne John B. , Moffett W. Duncan
Published: May 2006

The 121Sb Mössbauer spectra of a number of SbX4− and Sb2X93− salts have been recorded. Only SbF4−, SbCl4−, and Sb2F93− show significantly large quadrupole splittings with the 5s electrons being stereochemically active.
An Investigation of σ and π Contributions to Long-range 1H–1H Coupling Constants in Planar Aromatic Derivatives Using CNDO and INDO Molecular Orbital Calculations
Authors: Peat Ian R. , Reynolds William F.
Published: May 2006

Molecular orbital calculations of coupling constants based on finite perturbation theory in the CNDO/2 and INDO approximations have been carried out for styrene, benzaldehyde, and naphthalene. INDO calculations have also been carried out in which one-center exchange integrals involved in σ–π interaction are omitted (INDO(σ) calculations). Both CNDO and INDO(σ) constants give reasonable estimates of σ contributions to long-range 1H–1H couplings, with the former giving better results when strongly stereospecific σ contributions are present. INDO calculations also give reasonable, but generally overestimated, π contributions to these couplings.
Comments on the 14-12-8-6 Potential Function
Authors: Caligaris Roberto Emilio , Scalise Osvaldo Héctor , Grigera José Raul , Smith Jr. Vedene H. , Thakkar Ajit J.
Published: May 2006

Argon second and third virial coefficients for the recently proposed 14–12–8–6 potential are calculated and compared with experiment. The influence of the coefficients in the longrange dispersion energy on both of the virial coefficients is discussed.
Carbon-13 Nuclear Magnetic Resonance Spectra of Carcinogenic Polynuclear Hydrocarbons. I. 3-Methylcholanthrene and Related Benzanthracenes
Authors: Ozubko Richard S. , Buchanan Gerald W. , Smith Ian C. P.
Published: May 2006

Carbon-13 chemical shifts are reported for a series of carcinogenically active and related inactive polynuclear hydrocarbons. Resonance assignments for complex systems such as 3-methylcholanthrene, dibenzanthracenes, benz[a]anthracene and its 7-methyl and 7,12-dimethyl derivative, have been made primarily from a study of simpler models, including phenanthrene, triphenylene, and anthracene. Selective proton decoupling has been employed extensively. Quaternary carbon assignments have been aided by deuterium isotope shift and spin–lattice relaxation time measurements. Vicinal C—D couplings have been found to be unreliable as means of assignment for quaternary carbons.
Pyridine-catalyzed Halogenation of Aromatic Compounds. II. A Study of the Bromine Adducts of Pyridinium Bromide using Differential Scanning Calorimetry and Isothermal Gravimetric Analysis
Authors: Taylor G. R. , Gesser H. D. , Dunn G. E.
Published: May 2006

The composition and melting points of the bromine adducts of pyridinium bromide have been determined. Differential scanning calorimetry has been found to be particularly well suited to this type of phase study because it uses small, enclosed samples and responds rapidly to small heat changes. The adducts are described in terms of stoichiometric mixtures of pyridinium bromide and pyridinium tribromide, or in terms of a general formula PyHBr(Br2)n where n equals 1/3, 1/2, 2/3, 1, 3, 6, 18. When pyridinium bromide is allowed to pick up bromine isothermally in an apparatus for thermogravimetric analysis it does so in a stepwise manner with a plateau for each of the above adducts plus one with n equal to 3/2. This provides valuable confirmation of the compositions of adducts deduced from conventional phase diagrams.
Radiation-sensitized Thermal Cracking of n-Butane. I. Radical Reactions
Authors: Matsuoka Shingo , Tamura Takaaki , Oshima Keichi , Oshima Yunosuke
Published: May 2006

The radiolysis of n-butane was investigated at temperatures ranging from 17 to 548 °C in both static and flow systems.It was concluded that in the radiation-sensitized thermal cracking region the main products, methane, ethane, ethylene, and propylene, were formed by a radical chain mechanism. The conclusion was reached from comparison with the thermal cracking products, the effect of ammonia addition, the dose rate dependence, and in particular the correlation between the temperature change of the type of the main chain-termination reaction and that of the activation energy of propylene formation. The value of the activation energy for propylene formation showed that the main chain-termination reaction at temperatures between 410 and 520 °C was a combination reaction of ethyl radicals. The major part of 1-butene, trans-2-butene, and cis-2-butene, formed in the chain region, was shown to result from the thermal decomposition of the chain carrying butyl radicals.Rate parameters for some of the reactions involved were calculated.
Cinétique de l'interaction de l'inosine avec le [Pt(dien)Br]Br
Authors: Séguin Jean-Yves , Kong Pi-Chang , Zador Miklos
Published: May 2006

Kinetics of substitution of [Pt(dien)Br]+ by inosine in water has been investigated. The reaction is strongly inhibited by bromide ions, while the order with resect to inosine is smaller than one. These results are in agreement with a mechanism via an aquo-intermediate, [Pt(dien)H2O]2+ and also with a relatively small contribution of the SN2 path. The kinetic parameters have been determined and are discussed.