bluuebunny/crossref_metadata_2025 huggingface dataset:
Radiolysis of Liquid Di-n-propyl Ether: Alcohol Formation and Solvated Electrons
Authors: Vermeer Rebecca Arrieta , Freeman Gordon R.
Published: May 2006

In the γ radiolysis of pure di-n-propyl ether at 296 K, G(n-propanol) = 2.5 ± 0.1. The propanol yield was reduced by the addition of an electron scavenger (SF6) or proton scavenger (C3H7NH2), but was not affected by the addition of hydrogen chloride or propylene. In the absence of additives the geminate neutralization reaction [7] R2OH+ + esolv− → ROH + R gave 1.8 G units of alcohol. The charge scavenging reactions of SF6 and C3H7NH2 were consistent with the nonhomogeneous kinetics model reported earlier. The optical absorbance of solvated electrons in di-n-propyl ether increased with wavelength up to 1.6 μ, the practical limit of the detector, at all temperatures in the liquid range, including the liquid supercooled to 140 K. (f.p. = 151 K). The kinetics of electron reactions could be measured by observing the absorption at 0.9 μ. The optical absorbance observed as a function of time t at all temperatures was consistent with the kinetics model and had the general form: absorbance = b(t−1/2 + c)e−kt, where b is a proportionality constant, c is related to the free ion yield and k is a first order decay constant that describes the decay of the solvated electron free ions. At 273 K, k(esolv− + SF6) = 4.5 × 1010 M−1 s−1 and the activation energy is 3.2 ± 0.3 kcal/mol.
Mössbauer Spectra, Bonding, and Structure In Sn(IV) Acetylacetonates
Authors: Bancroft G. M. , Sham T. K.
Published: May 2006

119Sn Mössbauer spectra have been recorded for sixteen acetylacetonates of the type R2–xClxSnL2 (R=Me, Ph; L=anions of acetylacetone or substituted acetylacetone) and Cl4SnHL. The quadrupole splittings have been used to assign stereochemistry for most of these compounds. The good correlation between quadrupole splitting and center shift for the dimethyl analogues shows that there is no appreciable Sn 5s character in the Sn—L bonds. The correlation between [Formula: see text] and center shift for the dimethyl compounds is consistent with the above interpretation, and indicates that changes in [Ψ(0)5s]2 are dominant in determining both the center shift and J values for these compounds. The Mössbauer parameters for the compounds containing a neutral ligand show that the bonding properties of HL are very similar to those of L.The dimethyl compounds all show a pronounced Goldanskii–Karyagin asymmetry in their spectra. The direction of this asymmetry is shown to be consistent with a positive quadrupole splitting for all the dimethyl compounds.
An Overview of Aeronomic Processes in the Stratosphere and Mesosphere
Authors: Nicolet M.
Published: May 2006

The discrepancy noted between theoretical and observational concentrations of O3 in the mesosphere and stratosphere can be explained by an effect of hydrogen compounds and of nitrogen oxides. Solar radiation dissociates water vapor and methane in the thermosphere and upper mesosphere. In the stratosphere the reaction of the excited oxygen atom O(1D) with methane and nitrous oxide leads to a destruction of these two molecules in the stratosphere which corresponds to a production of carbon monoxide with water vapor and of nitric oxide, respectively. Hydrogen and water vapor molecules also react with the electronically excited oxygen atom O(1D) leading to hydroxyl radicals. Insitu sources of H2 exist in the stratosphere and mesosphere: reaction of OH with CH1, photodissociation of formaldehyde, and also reaction between hydroperoxyl radicals and hydrogen atoms. The vertical distribution of water vapor is not affected by its dissociation in the stratosphere and mesosphere since its reformation is rapid.The ratio of the hydroxyl and hydroperoxyl radical concentrations cannot be determined with adequate precision and complicates the calculation of the destruction of ozone which occurs through reactions of OH and HO2 not only with atomic oxygen at the stratopause but also directly in the middle stratosphere and with CO and NO in the lower stratosphere.In addition to the various reactions involving nitric oxide and nitrogen dioxide, the reactions leading to the production and destruction of nitric acid and nitrous acid must be considered. Nitric acid molecules are involved in an eddy diffusion transport from the lower stratosphere into the troposphere and are, therefore, responsible for the removal of nitric oxide which is produced in the stratosphere. Atmospheric conditions must be known at the tropopause.
Stratospheric Chlorine: a Possible Sink for Ozone
Authors: Stolarski R. S. , Cicerone R. J.
Published: May 2006

This study proposes that the oxides of chlorine, ClOx, may constitute an important sink for stratospheric ozone. A photochemical scheme is devised which includes two catalytic cycles through which ClOx destroys odd oxygen. The individual ClX constituents (HCl, Cl, ClO, and OClO) perform analogously to the respective constituents (HNO3, NO, NO2, and NO3) in the NOx catalytic cycles, but the ozone destruction efficiency is higher for ClOx. Our photochemical scheme predicts that ClO is the dominant chlorine constituent in the lower and middle stratosphere and HCl dominates in the upper stratosphere. Sample calculations are performed for several ClX altitude profiles: an assumed 1 p.p.b. volume mixing ratio, a ground level source, and direct injection by volcanic explosions. Finally we discuss certain limitations of the present model: uncertainty in stratospheric OH concentrations, the possibility that ClOO exists, the need to couple ClOx cycles with NOx and HOx cycles, and possible heterogeneous reactions.
The Interaction of Electrochemically Produced Radical Cations with Substituted Styrenes
Authors: Funt B. Lionel , Verigin Victor
Published: May 2006

Relatively stable radical cations of 9,10-diphenylanthracene (DPA) were formed by controlled potential electrolysis of solutions in acetonitrile. The rates of decay of the ions were measured in the absence and presence of substituted styrenes, including α-methylstyrene, trans-β-methylstyrene, p-methylstyrene, and styrene. In rigorously dried solvent the radical cation was relatively stable, and its rate of decay was independent of its initial concentration. In the presence of monomers the rates of decay were increased greatly and were related to the position of the methyl substituent in the styrene structure.The rate was proportional to [Formula: see text] A mechanism is suggested and interpreted to show that the rates of cation decay are indicative of the rates of propagation in the polymerization process.
Evidence for Restricted Rotation in the 1H and 19F Nuclear Magnetic Resonance Spectra of Cyclopentadienylperfluoroalkyliron and Nickel Complexes
Authors: Stanley K. , Zelonka R. A. , Thomson J. , Fiess P. , Baird M. C.
Published: May 2006

Several series of compounds CpFeCOLRF, CpNiPPh3RF, and mer-Fe(CO)3LRFI (RF = CF3, CF2CF3, CF(CF3)2; L = PPh3, PMePh2, PMe2Ph), some of them new compounds, have been prepared and characterized. Evidence for restricted rotation about both metal–alkyl and phosphorus–aryl bonds is deduced from the variable temperature 1H and 19F n. m. r. spectra of the complexes. The presence of two vCO in the i. r. spectra of the pseudotetrahedral iron complexes suggests that these compounds exist as diastereomers, the coordinated phosphine and the nickel constituting chiral centers.
Synthesis of Nucleotides from O2,2′-Cyclouridine
Authors: Ogilvie Kelvin K. , Iwacha Donald J.
Published: May 2006

Procedures for the synthesis of protected O2,2′-cyclouridines and their incorporation into dinucleoside monophosphates have been developed. The properties of these molecules with snake venom and spleen phosphodiesterases have been investigated. The cyclonucleotides are easily converted into arabinouridine nucleotides and thus provide a convenient route to these compounds.
Bimolecular Reactions of Trapped Ions. VIII. Reactions in Propane and Propane–Methane Mixtures
Authors: Solka Bruce H. , Lau Andrew Y.-K. , Harrison Alex. G.
Published: May 2006

The ion-molecule reactions in propane and in methane–propane mixtures have been studied using an ion-trapping technique and rate coefficients have been measured for the reactions occurring. In pure propane the C2H5+ primary ions react by H− transfer to form C3H7+ whereas C2H4+ reacts to form C3H6+ (25%) and C3H7+ (75%). Using isotopically labelled propanes it was found that both n-propyl and i-propyl ions were formed with the n-propyl ions reacting slowly to produce i-propyl ions. In various deuterium labelled methane–propane mixtures C(H,D)5+ reacts with the propane with a rate constant of ∼1.5 × 10−9 cm3 molecule−1 s−1 in agreement with the calculated collision rate. It is shown that no hydrogens from the CH5+ ion are incorporated in the product ions which are found to be C2H5+ (70%), (CH3)2CH+ (25%), and CH3CH2CH2+ (5%).
The Nitroalkane Anomaly
Authors: Kresge A. J.
Published: May 2006

The effect of substituents on the reaction of nitroalkanes with base is analyzed in terms of two interactions which influence both rate and equilibrium constants and two others which affect the rates alone. The results of these calculations serve to explain the Brønsted relation with negative exponent given by data for the series nitromethane, nitroethane, and 2-nitropropane reacting with hydroxide ion, and also the Brønsted exponents greater than unity recently observed for the reactions of aryl-substituted nitroalkanes with hydroxide ion and other bases.
Cobalt(II) and Nickel(II) Complexes with Nitrogen, Sulfur, and Selenium Containing Heterocyclic Ligands
Authors: Preti C. , Tosi G. , Filippo D. De , Verani G.
Published: May 2006

Cobalt(II) and nickel(II) halide complexes with thiomorpholin-3-thione and thiazolidine-2-selenone have been prepared. Infrared and far infrared spectra, electronic spectral studies, and magnetic susceptibility measurements indicate that the cobalt derivatives are tetrahedral in structure, nickel chloro- and bromo-thiomorpholin-3-thione derivatives are octahedral while [Nits2I2] and all nickel thiazolidine-2-selenone complexes have a pseudo-tetrahedral symmetry. The probable site of bonding in the ligands is nitrogen in all the complexes studied here, except the nickel derivatives of thiazolidine-2-selenone. These results are confirmed by n.m.r. measurements. Spectroscopic parameters for the complexes have been calculated and compared against similar chromophores containing MN2X2 and MS2X2 chromophores.
The Synthesis and Stereochemistry of (±)-(4a,13b-trans)-2,3,4,4a,8,9,13b,14-Octahydro-1H-benzo[6,7]cyclohepta[1,2,3-de]pyrido[2,1-a]-isoquinoline Hydrochloride (Taclamine Hydrochloride), a Novel Psychotropic Agent
Authors: Bruderlein François T. , Humber Leslie G. , Pelz Karel
Published: May 2006

Two synthetic routes to (±)-(4a,13b-trans)-2,3,4,4a,8,9,13b,14-octahydro-1H-benzo[6,7]cyclohepta[1,2,3-de]pyrido[2,1-a]isoquinoline hydrochloride (1) (taclamine hydrochloride) are described. Configurational assignments have been made on the basis of n.m.r. spectral interpretations and mechanistic considerations.
The Total Synthesis of Racemic Napelline
Authors: Wiesner Karel , Ho Pak-Tsun , Tsai Connie Shii Jeou (Pan) , Lam Yiu-Kuen
Published: May 2006

Lucidusculine 1 was converted into the lactame 5. This compound is identical with the corresponding racemate described in the accompanying Communication. The synthesis of napelline 2 from the lactame 5 is discussed. The process completes the first (formal) total synthesis of a racemic hexacyclic polysubstituted aconite alkaloid.
Organic Sulfur Mechanisms. 16. Competing Reverse Diels–Alder and Desulfonylation–Rearrangement Reactions in the Thermolysis of a Cyclic Sulfone
Authors: King James Frederick , Enanoza Rudyard Mendiola , Lewars Errol George
Published: May 2006

2,2-Dioxido-4-phenyl-2-thiabicyclo[2.2.2]octa-5,7-diene-5,6-dicarboxylic anhydride (4) on heating gives about equal amounts of a biphenyl (5) and a cycloheptatriene (6), derived respectively from a reverse Diels–Alder reaction and a desulfonylation accompanied by allylic rearrangement followed by further rearrangement. This contrasts with our earlier observation that the corresponding dimethyl ester (1a) gives only the reverse Diels–Alder products. Possible factors affecting the course of the reaction of such species are discussed.
Barrier to Internal Rotation in 2,6-Dichlorobenzal Iodide and some α,α′-m-Xylyl Halides. Experimental Evidence for the Transition State Conformation in Benzal Halides
Authors: Peeling James , Rowbotham J. Brian , Ernst Ludger , Schaefer Ted
Published: May 2006

The barriers to internal rotation in the α,α′-di-X-2,4,5,6-dichloro-m-xylenes (X = Cl, Br, I ) are determined by proton magnetic resonance bandshape analyses. Their magnitudes are experimental evidence for the calculated conformation of the activated rotational state of the benzal halides, in which the C—H bond of the side chain is predicted to lie in a plane perpendicular to the aromatic nucleus. The synthesis and the barrier to rotation in 2,6-dichlorobenzal iodide are reported.
Synthesis and 19F Nuclear Magnetic Resonance Spectra of Fluorosubstituted Bis(arene)chromium Complexes
Authors: McGlinchey Michael J. , Tan Teong-Seng
Published: May 2006

A series of substituted bis(fluorobenzene)chromium complexes, (C6H4FX)2Cr, where X is H, F, Cl, CH3, or CF3, have been synthesized by cocondensing Cr atoms and fluoroarenes. The 19F chemical shifts of these compounds correlate well with those of the corresponding C6F5X system suggesting that the overall electron-withdrawing effect of a π-bonded Cr on each ring is similar to the effect of four ring fluorine substituents.
Conformational Analysis of trans-syn-trans-4,5:9,10-Biscyclohexano-1,3,6,8-tetraoxecane: a Low-energy Pathway for Boat–Chair–Boat (BCB) Interconversion
Authors: Grindley T. Bruce , Szarek Walter A.
Published: May 2006

Two processes were observed by study of the variable temperature p.m.r. spectra of trans-syn-trans-4,5:9,10-biscyclohexano-1,3,6,8-tetraoxecane (1), one of which, an equilibrium, was still rapid at −88°; the other had an energy of activation (ΔG≠) of 11.7 kcal/mol. These processes are interpreted in terms of interchange in the 10-membered ring between four conformations, namely, two degenerate pairs of diastereomeric boat–chair–boat (BCB) conformations. Possible pathways of conformational interconversion are discussed.
The Hydrolysis of Esters Related to O-Hippuryl-2-hydroxybutanoic Acid by Carboxypeptidase A
Authors: Bunting John W. , Murphy Joe
Published: May 2006

The hydrolysis of each of the following esters by bovine carboxypeptidase A has been studied at pH 7.5, 25°, ionic strength 0.5: O-hippuryl-, O-phenaceturyl-, O-aceturyl-, O-(N-methylhippuryl)-, and O-(N-hippurylglycyl)-2-hydroxybutanoic acids, and 2-(3-benzoylpropanoxy)-, 2-benzoxyacetoxy-, and 2-(4-phenylbutanoxy)butanoic acids. Substrate inhibition occurs with only the hippuric and phenaceturic acid esters and in the six other cases simple Michaelis–Menten kinetics are observed. The relatively minor variations in the structures of the acid moieties of these esters lead to quite large variations in Km, although kcat seems to be relatively independent of the nature of the acid moiety. Binding modes of substrate molecules at both the catalytic and inhibitory sites are discussed in the light of these observations.
Etude théorique d'hydrocarbures simples par la méthode PCILO
Authors: Grignon Jacques , Fliszár Sándor
Published: May 2006

The experimental geometries of a number of alkyl-substituted ethylenes are satisfactorily reproduced by PCILO calculations. Deficiencies appear, however, with linear substituents, e.g., in 1-butene and 1-pentene. The experimental trends for the HCH angles are in general reflected but over emphasized by the PCILO method.
Regiospedfic Syntheses of Modified Steroid Hormones. Part VI. α-, α′-, and β-Mode Reactions of Hydrogen Halides with 1,2-Epoxy- and 4,5-Epoxy-3-oxo-androstanes and -estranes
Authors: Neeman M. , O'Grodnick J. S.
Published: May 2006

The reaction of A/Bcis-4β,5β-epoxy-17β-hydroxyandrostan-3-one acetate 1b with hydrogen fluoride in chloroform gave 5α-fluoro-4α,17β-dihydroxyandrostan-3-one acetate 10b by β-mode oxirane opening to 10a, followed by epimerization at C-4. Reactions of A/Bcis-α,β-epoxyketones 1a and 1c in acetone containing aqueous hydrogen chloride resulted in α-mode regiospecific oxirane opening, followed by β-dehydration to 4-chloro-4-en-3-ones 4a and 4c. Reaction of hydrogen chloride in "10%" ethanol–chloroform with 4β,5β-epoxy-17β-hydroxyandrostan-3-one 1a gave non-regioselectively 3a and 4a (α:α′1:1), whereas the reactions with 4α,5α-epoxy-17β-hydroxyandrostan-3-one acetate 2, 1α,2α-epoxy-17β-hydroxy-5α-androstan-3-one 6a, and 1β,2β-epoxy-17β-hydroxy-5α-androstan-3-one acetate 5 were α-mode regiospecific. Epoxyketone 5 was readily converted to the trans-diequatorial 2α-chloro-1β,17β-dihydroxy-5α-androstan-3-one acetate 7. The reactions of hydrogen fluoride with 4β,5β-epoxy-17β-hydroxy androstan-3-one 1a in "10%" ethanol–chloroform or in N,N-dimethylformamide, and with 1α,2α-epoxy-17β-hydroxy-5α-androstan-3-one 6a in N,N-dimethylformamide were α′-regioselective. Mechanisms are proposed for the observed α-, β-, and α′-mode reactions of hydrogen halides with steroidal α, β-epoxyketones 1, 2, 5, and 6.
Additivity Parameters for Organotin 13C Chemical Shifts
Authors: Axelson D. E. , Kandil S. A. , Holloway C. E.
Published: May 2006

Twenty-four four-coordinate organotin derivatives have been examined by 13C n.m.r. and a set of 11 additive parameters computed to determine shielding effects of substituents. The chemical shift coefficients obtained are compared to their organic analogs.
Composition and Stability of Iron and Copper Citrate Complexes in Aqueous Solution
Authors: Field Terrence B. , McCourt Janet L. , McBryde W. A. E.
Published: May 2006

The acidity constants of citric acid and the stability constants of the citrate complexes of copper(II), iron(II), and iron(III) have been measured at 25 °C in 0.1 M KNO3 background. The measurements were based on mass balances on hydrogen ions, supplemented in the case of Cu(II) and Fe(III) complexes by measurements of free metal concentration with a solid-state copper-ion-sensitive electrode and a redox electrode respectively. The data required the assumption of a binuclear copper complex, but all complexes characterized were of 1:1 stoichiometry.
Water-soluble Lysine-containing Polypeptides. I. The Synthesis and Characterization of Several Sequential Lysine–Glycine Polypeptides Including a Preliminary Study of their Interaction with DNA
Authors: Brown John , Langlois Jean R. , Lauren Denis R. , Stoochnoff Barbara K. , Williams Ross E.
Published: May 2006

The preparation and characterization of several sequential lysine–glycine polypeptides is described. A preliminary study of their interaction with DNA is also presented.
Pulse Radiolysis of Liquid Methylamine, Ethylamine, and Ammonia: The Yield of Solvated Electrons
Authors: Seddon William Arthur , Fletcher John Wallace , Sopchyshyn Fred Charles , Jevcak John
Published: May 2006

Yields of solvated electrons, [Formula: see text], have been measured in both the pure and basic solvents using biphenyl and pyrene as electron scavengers. In pure methylamine and ethylamine [Formula: see text]and 1.84 ± 0.1, respectively. However in basic solution these yields more than double giving [Formula: see text]. In liquid NH3 and ND3 at −15 °C, [Formula: see text] and 3.6 ± 0.2, respectively. The latter yields seem independent of base and temperature from −15 to −50 °C. Comparisons with previous work are discussed.
Hydrates des halogenures de gallium. II Spectroscopie de vibration des complexes coordinés GaX3•H2O (X = Cl ou Br)
Authors: Roziere Jacques , Roziere-Bories Marie-Thérèse , Manteghetti Alain , Potier Antoine
Published: May 2006

GaX3.H20 (X = Cl, Br) is a tetrahedrally coordinated adduct of gallium. From vibrational spectra of hydrates, deuteriates, and mixed crystals, bands assignments are made. Spectra are consistent with OGaX3 (C3υ) and H2O (C2υ) groups but the maximum symmetry of the whole complex (Cs) is lowered to C1 owing to the nonequivalence of the two O—H of the water molecule. The "Ga—O" stretching modes are located and the valence force field of OGaX3 skeleton is computed. The coordination bond is strong and the halogen–metal bonds are shorter than in the tetrahalogenogallate ions.
The Adsorption, Desorption, and Exchange Reactions of Oxygen, Hydrogen, and Water on Platinum Surfaces. I. Oxygen Interaction
Authors: Peng Y. K. , Dawson P. T.
Published: May 2006

The kinetics of adsorption and desorption of oxygen on a platinum filament have been studied by temperature-programmed desorption mass spectrometry. Oxygen adsorption becomes significant only after any carbon contamination is removed from the surface. At 300 °K oxygen adsorbs dissociatively into an atomic β-state which contains four overlapping sub-states. The initial sticking probability is 0.16 but this falls off rapidly with increasing coverage. A kinetic analysis for desorption from the β2- and β4-states gave Edes≠(β2) = 39 kcal mol−1 and Edes≠(β4) = 54 kcal mol−1 The desorption was first order suggesting a lack of mobility of the adatoms at the desorption temperature (∼700°K). No oxygen atom desorption could be detected in a line-of-sight experiment. Adsorption of a mixture of 32O2 and 36O2 resulted in complete isotopic mixing on desorption. At 115 °K, the β-state still populates first with the same initial sticking probability indicating adsorption is nonactivated. Moreover, the sticking probability remains at its high initial value for a much more extensive coverage range, suggesting a precursor state to adsorption. After the β3- and β4-states are fully occupied, further adsorption into the β-state is competitive with occupation of an α-state which desorbs at low temperatures (∼150°K) with first order kinetics and Edes≠(α) ∼6 kcal mol−1 No isotope mixing occurred in the α-state which is undoubtedly molecular. Prior population of the β1- and β2-states at 300 °K reduced the α-state adsorption at 115 °K suggesting that α and β occupy the same sites. Each site can adsorb either an atom or molecule since each molecule added to the β-state excludes two molecules from the α-state.
Diffusion in Partially Ion Exchanged Molecular Sieves
Authors: Ruthven D. M.
Published: May 2006

Results of a simple idealized numerical simulation are presented showing the variation of sorbate diffusivity with degree of ion exchange in a system such as the Na–Ca A zeolites. Theoretical curves showing the expected variation of diffusivity, diffusional activation energy, and pre-exponential factor are given. The pattern of behavior predicted depends on the ratio of the diffusivities for the extreme ionic forms. When this ratio is small there is a gradual variation in diffusivity, activation energy, and pre-exponential factor over the entire range of ionic compositions but for large ratios there is an abrupt change at a particular ionic composition. Limited experimental data for the diffusion of n-butane in partially Ca2+ exchanged 4A sieve are presented and interpreted in terms of the theoretical model.
Photolysis of Aqueous Solutions of Hydrogen Peroxide Containing β-Ammonio Alcohols
Authors: Foster Terry , West Paul Ronald
Published: May 2006

During the photolysis of aqueous H2O2 added β-ammonio alcohols suffer oxidative attack initiated through hydrogen abstraction by the •OH radical. At pH 7.0 the initially formed radical,[Formula: see text] undergoes fragmentation to yield [Formula: see text] and CH3COR′ exclusively. At pH 1.0 fragmentation is less important and direct oxidation to [Formula: see text] dominates. A radical deprotonation step is proposed to account for the pH dependence.
Sorption of Water, Ammonia, Ethyl Chloride, and Methane on Na—X Zeolite and Associated Framework Distortion
Authors: Rimmer D. L. , McIntosh R.
Published: May 2006

Length change and sorption isotherms have been determined for water, ammonia, ethyl chloride, and methane on compacted samples of zeolite NaX. Methane sorption at 0 °C and ethyl chloride sorption at −10°C were accompanied by little or no framework distortion as monitored by length change measurements; sorption of ammonia in the temperature range −50 to −70 °C produced more appreciable distortion; and water sorption at room temperature caused large changes. In each case the framework distortion was correlated with different stages in the sorption process. The sorption isotherms for the ammonia/NaX system indicated the possibility at high uptakes of two-dimensional condensation or multilayer formation. The critical temperature for two-dimensional condensation would be −70 °C.
Charge Distributions and Chemical Effects. VIII. Ionization Potentials of Normal and Branched Alkanes
Authors: Henry Hervé , Fliszár Sándor
Published: May 2006

The comparison of adiabatic ionization potentials of normal and branched alkanes with carbon net charges indicates a lowering of the i.p.'s with increasing electron population of the electron-richest pair of bonded C—C atoms in the molecules. In terms of "inductive charges", it is found that n = −4.4083, i.e., precisely the same ordering of charges previously determined from l3C n.m.r. shifts. The relative C charges can thus be calculated from 13C chemical shifts and used in the equation [Formula: see text], where [Formula: see text] one half the sum of charge on the pair of electron-richest bonded C atoms, to give i.p.'s with a standard error of 0.044 eV. The relevance of these charges with respect to carbon 1s binding energies is discussed.
Decomposition Mechanism of 1,2-Dioxetane
Authors: Barnett Gene
Published: May 2006

An orbital correlation diagram was constructed for the thermal decomposition of 1,2-dioxetane into products that allow chemiluminescence. A decomposition mechanism is proposed that gives a temperature dependent rupture of the OO bond, thus allowing ring twisting which is followed by the rupture of the CC bond. This mechanism is consistent with results of the thermochemical analysis for this type of reaction. The equilibrium structure of 1,2-dioxetane was determined from the molecular orbital calculations and gave a planar configuration for the COOC ring.
The Hg 6(3P)-Photosensitized Oxidation of C2Cl4
Authors: Sanhueza Eugenio , Heicklen Julian
Published: May 2006

The Hg 6(3P) sensitized photolysis of C2Cl4 was studied at 25 °C both in the absence and presence of N2O and O2. For C2Cl4 alone, the only products are polymer and Hg2Cl2. The quantum yield of C2Cl4 disappearance, −Φ{C2Cl4} ∼ 1. Thus, the photolysis produces C2Cl3 radicals and Hg2Cl2, the C2Cl3 radicals dimerize, and the resultant 1,3-C4Cl6 polymerizes. The relative quenching of Hg 6(6P) by C2Cl4 compared to N2O is 3.0.In the presence of O2 the products are CCl3CCl(O) and CCl2O which are formed in a radical chain process in a ratio of 2.6 independent of reaction conditions. CO is also produced with a quantum yield of unity. The quantum yields of the chlorine-containing products are independent of the O2 pressure and the absorbed intensity, but are proportional to the C2Cl4 pressure, the proportionality constants being 1.4 and 3.7 Torr−1, respectively, for CCl2O and CCl3CCl(O). A detailed mechanism, based on the chlorine atom chain oxidation, is presented, and appropriate rate constant ratios are evaluated.
Proton Magnetic Resonance Study of Conformational Equilibria of the Pyridinealdehydes in Solution. Comparison with Other Methods
Authors: Danchura Werner , Schaefer Ted , Rowbotham J. Brian , Wood Donald J.
Published: May 2006

A p.m.r. study of the pyridinealdehydes shows that accurate spectral analysis yields long-range spin–spin coupling constants which are a precise measure of the conformational equilibria in solution. Thus, in CS2 solution the ON-trans form of 2-pyridinealdehyde is more stable than the ON-cis form by at least 2.3 kcal/mol, while in acetone solution it is 1.6 kcal/mol more stable than the cis form. Classical solvation theory allows the conclusion that in the gas phase the trans form is more stable than the cis form by about 7 kcal/mol, in contradiction to the predictions of approximate MO theory at the INDO level. The trans form of 3-pyridinealdehyde is also more stable than the cis form in polar and in nonpolar solvents. The results are compared with those of other experiments on these equilibria.
Thermolysis of Some 4-Alkylidene-1-pyrazolines
Authors: Crawford Robert J. , Cameron Douglas M. , Tokunaga Hirokazu
Published: May 2006

The thermolysis of 4-methylene-1-pyrazoline and the kinetic isotope effects of 3,3-d2, 3,3,6,6-d4, and 3,3,5,5,6,6-d6 compounds were examined. Data suggest a simultaneous cleavage of both carbon–nitrogen bonds with the formation of an intermediate which by 13C labelling is shown to be other than the triplet planar trimethylenemethane. Product studies on 3,3-dimethyl-4-methylene-1-pyrazoline and 4-isopropylidene-1-pyrazoline are best rationalized in terms of the Chesick type intermediate.
The Chemistry of High Molecular Weight Fulvic Acid Fractions
Authors: Neyroud Jean A. , Schnitzer Morris
Published: May 2006

Fulvic acid (FA) was methylated, dissolved in benzene, and fractionated over Al2O3 with the aid of organic solvents of increasing polarities. This paper is concerned with fractions eluted with ethyl acetate (III), ethyl acetate — methanol (1:1) (IV), and methanol (V), which were quantitatively the most abundant ones and which we consider as being most representative of the original FA. Each fraction was characterized by chemical and spectroscopic methods and by degradation with alkaline permanganate. Fractions IV and V were also degraded by NaOH hydrolysis and by alkaline CuO-oxidation. The degradation products were identified with the aid of a gas chromatograph — mass spectrometer — computer system.The number-average molecular weights of the three fractions were: III, 821; IV, 945; and V, 1,397. Infrared, proton n.m.r., and carbon-13 n.m.r. spectra provided, except for functional groups, little detailed information on the chemical structures of the fractions. The major degradation products were benzenecarboxylic and phenolic acids in addition to smaller amounts of aliphatic (mainly n-fatty) acids. Evidence is presented that may be interpreted to indicate: (a) esterification of some of the fatty acids to OH groups of phenolic acids; (b) the existence in the fractions of ether (C—O) linkages; and (c) rupture of C—C bonds during degradation. While in both the lower and the higher molecular weight FA fractions benzenecarboxylic and phenolic acids were the basic "building blocks", the latter appeared to be more complex and more stable in the higher-molecular weight fractions, possibly because chemical bonding as well as hydrogen bonding, van der Waal's forces, and π-bonding were involved simultaneously.
Influence des groupes tert-butyle, triméthylsilyle et triméthylgermyle sur la stéréochimie de réactions d'addition en série cyclohexénique. I. Synthèse des alcènes et hydroboration
Authors: Freppel Christian , Poirier Marc-André , Richer Jean-Claude , Maroni Yvette , Manuel Georges
Published: May 2006

Syntheses of 1-tert-butyl-(1a), 1-trimethylsilyl-(1b) and 1-trimethylgermanyl-4,4-dimethylcyclohexene (1c) are described as are those of 6-tert-butyl- (2a), 6-trimethylsilyl- (2b) and 6-trimethylgermanyl-3,3-dimethylcyclohexene (2c). The stereochemistry of the hydroboration of these alkenes is examined. The stereochemistry is governed, on the one hand, by the steric influence of the various substituents and on the other by the steric and electronic effects of the trimethylsilyl and trimethylgermanyl groups. [Journal translation]
A Synthesis of (±)-Cularicine
Authors: Noguchi Isao , Maclean David B.
Published: May 2006

A synthesis of (±)-cularicine is reported. 2-(2′-Benzyloxyphenoxy)-4,5-methylenedioxy-phenylacetic acid was converted in four steps to 6-benzyloxy-2,3-methylenedioxy-10,11-dihydrodibenz[bf]oxepin-10(11H)-one. A modified Pomeranz–Fritsch reaction was applied to this ketone to add the two carbon atoms and one nitrogen atom required to complete the carbon skeleton of cularicine. The norcularicine derived from this reaction was N-methylated with formaldehyde and sodium borohydride.
The Synthesis of 4a-Aminoalkyl-1,2,3,4,4a,9-Hexahydrophenanthrenes. Versatile Intermediates for Potential CNS Drugs. I
Authors: Belleau B. , Conway T. T. , Doyle T. W. , Morris L. , Verbestel W.
Published: May 2006

The synthesis of 1-aminoalkyl-1-hydroxy-2,2-tetramethylene-1,2,3,4-tetrahydronaphthalenes and their Wagner–Meerwein rearrangements into 4a-aminoalkyl-1,2,3,4,4a,9-hexahydrophen-anthrenes are described.
Photo-oxidation of Iodomethane in Solid Argon
Authors: Ogilvie J. F. , Salares Virginia R. , Newlands Michael J.
Published: May 2006

Photolysis of iodomethane in the presence of oxygen in solid argon near 10 K has yielded several products detected by their vibrational absorption spectra. Isotopic labeling of reactants has proved methanal, water, hydrogen iodide, carbon monoxide, carbon dioxide, and hydro-peroxyl radicals to be significant products, and a further set of major absorptions is attributed to hydrogen hypoiodite HOI, hydrogen-bonded to methanal. Other minor vibrational features are discussed, and a possible reaction scheme is briefly outlined.
119Sn Mössbauer Spectra of Sn–Ni Compounds
Authors: Bancroft G. Michael , Butler K. David
Published: May 2006

Sn Mössbauer spectra have been recorded for eleven tin-nickel compounds of the type Clx,Sn[NiLCp]4−x (L = CO, PPh3;x = 2,3) and Cl3SnNiL2Cp.S (S = solvent molecule). The center shifts are used to distinguish coordinated SnCl3 and uncoordinated ionic SnCl3−, respectively. In the SnCl3− compounds, the Mössbauer parameters indicate that the solvent molecules are not bonded to the Sn atom. In compounds containing Sn—Ni bonds, the center shifts and quadropole splittings show that Ni(PPh3)Cp is the best donor of the first row transition metal moieties, and that the Sn—Ni bond has the highest Sn s character. Ni(CO)Cp is a slightly poorer donor than Ni(PPh3)Cp, and the Sn—Ni bond has a smaller s character.
The Determination of Traces of Nickel(II) By Solid State Spectroscopy
Authors: Ryan Douglas Earl , Holzbecher Jiri
Published: May 2006

Traces of nickel (II) are determined by measurement of light absorption in the solid state after co-precipitation with a large excess of α-benzildioxime. The detection limit is 0.2 µg Ni and nickel can be recovered even from 1000 ml sample volumes (i.e. < 1 ng/ml can be determined). Only a few foreign ions interfere.
Mixed Boron Trihalide Adducts. A Nuclear Magnetic Resonance Study of Halogen Redistribution in Adducts of Trimethylphosphine, Trimethylphosphine Oxide, and Trimethylphosphine Sulfide
Authors: Bula Michael J. , Hartman J. Stephen , Raman Chirakal V.
Published: May 2006

Halogen redistribution in the sparingly soluble boron trihalide adducts of Me3P, Me3PO, and Me3PS gives mixed boron trihalide adducts of these bases. Only small proportions of the fluorine-containing mixed boron trihalide adducts are present at equilibrium in the Me3PS adduct system, in accord with previous studies of adducts of other sulfur donors. The effects of the donor on F,Cl and F,Br halogen redistribution are discussed.
Synthèse et propriétés des tert-butyl-5 triméthyl-2,3,3 cyclohexanols
Authors: Richer Jean-Claude , Lamarre Claude
Published: May 2006

The synthesis of the four 5-tert-butyl-2,3,3-trimethylcyclohexanols is reported and the properties of these secondary alcohols are compared with those of the tertiary alcohols obtained earlier from the reduction of 5-tert-butyl-2,3,3-trimethylcyclohexene epoxides. It is confirmed that secondary alcohols are not formed during the reduction of these epoxides. The stereochemistry of the LiAlH4 reduction of the 5-tert-butyl-2,3,3-trimethylcyclohexanones is discussed.
The Application of a Simple Chemical Model of Natural Waters to Metal Fixation in Particulate Matter
Authors: Guy Robert D. , Chakrabarti C. L. , Schramm Laurier L.
Published: May 2006

A simple chemical model was used to investigate the mechanisms controlling the distribution of metals between soluble and particulate fractions in natural waters. The model particulates used were potassium bentonite, hydrous MnO2, and solid humic acid. The soluble species in natural waters were modelled by soluble humic acid, tannic acid, and bicarbonate. The sorption curves for Cu(II), Cd(II), and Zn(II) onto humic acid and MnO2 obeyed Langmuir adsorption isotherms whereas the sorption of the above ions onto bentonite followed a Freundlich isotherm. Chemical analysis of the total model using atomic absorption spectroscopy and differential pulse anodic stripping voltammetry indicated that copper distribution depends on the pH of the suspension: above pH 6.0, 50 % of the copper is sorbed onto the particulates whereas the copper in solution is in a complexed form; between pH 6 and 3.8 the soluble copper is distributed between organic complexes and "free" copper ion; between pH 4.2 to 2.5 copper is being desorbed from the particulates; and below pH 2.5 all the copper is present in solution as "free" copper ion.
Réactions des ions moléculaires cyclohexane en phase gazeuse
Authors: Collin Guy J. , Ausloos Pierre
Published: May 2006

The [Formula: see text] ions formed in the photoionization of cyclohexane (resonance lines of argon: 11.6–11.8 eV) react with cyclic (C3 and C4) and unsaturated hydrocarbons by H2 transfer. This reaction is quantitative with propene, 1-butene, 1-pentene, 1,3-butadiene, and isobutene. This transfer is efficient only if there is a terminal double bond. There is ring opening with the C3 and C4 hydrocarbons. H atom transfer reactions are also observed between [Formula: see text] ions and several compounds and the structure of the radical formed in such a reaction is determined by chemical analysis. With cis-2-butene, there is only charge transfer reaction.
Isomérisation d'époxydes d'acétates d'énols en série pinanique
Authors: Bessière Yvonne , Gaïed Mohamed Moncef El , Boussac Ginette
Published: May 2006

The isomerization of enol acetate epoxides by zinc bromide leads to ketoacetates with retention of configuration. Thermal isomerization yields a ketoacetate with inversion of the configuration by a concerted mechanism if the oxirane does not contain a hydrogen atom. In the case of an oxirane containing hydrogen, an 'acid' type mechanism competes favorably with the concerted mechanism; the former yields a ketoacetate with retention of configuration. The isomer in which the configuration is retained is not the most stable. [Journal translation]
Photolysis of Aqueous Solutions Of 9,10-Anthraquinone-2-Sulfonate. Part II. Dependence of Rates of Hydroxylation on Reaction Conditions
Authors: Broadbent Arthur D. , Matheson Hugh B. , Newton Richard P.
Published: May 2006

The rates of formation of hydroxy-9,10-anthraquinone-2-sulfonates, produced by irradiation of neutral and alkaline aqueous solutions of 9,10-anthraquinone-2-sulfonate (A) at 365 nm, have been measured for solutions with initial [A] ranging from 5 × 10−5 to 8 × 10−2 mol dm−3, saturated with either O2, air, or N2. The rate of monohydroxylation was independent of the saturating gas and, for neutral solutions absorbing all the incident light, increased with increasing initial [A] reaching a constant maximum quantum yield of 0.08 above 2 × 10−2 mol dm−3. In 0.1 mol dm−3 aqueous NaOH solution, the rate was about three times larger but had not attained a limiting value at the maximum [A] imposed by its solubility. Dihydroxy-9,10-anthraquinone sulfonates are proposed to arise from reaction of O2 with an intermediate, rather than by further hydroxylation of monohydroxy products. The rate of dihydroxylation decreased on increasing [A] above 5 × 10−4 mol dm−3, becoming essentially zero at high concentrations.
Identification of Phenyl Vinyl Ketone And Related Compounds as 2,4-Dinitrophenylhydrazones and Pyrazolines
Authors: Allen C. F. H.
Published: May 2006

The closely interrelated, titled compounds, which have similar physical properties and which form mixtures difficult to separate, are best characterized by instrumental methods.All α,β-unsaturated aldehydes and methyl ketones gave open-chain dinitrophenylhydrazones directly, whereas the arylated ketones form pyrazolines, as is well known.
Theoretical Studies of Some Nonbenzenoid Hydrocarbons. II
Authors: DasGupta Archana , DasGupta Nadna K.
Published: May 2006

not available
Adsorption of Polar Organic Molecules at Oil/Water and Air/Water Interfaces
Authors: Aveyard Robert , Chapman John
Published: May 2006

A study has been made of the adsorption of several esters of dicarboxylic acids both at the alkane/water and the air/water interface. The adsorption of n-butanol and n-heptanol at the air/water surface has also been investigated. The surface pressure (π) – surface area (A) isotherms are compared for the various films, and standard free energies of adsorption have been determined.Attempts have been made to fit the π, A isotherms using surface equations of state based on the models of both a two-dimensional gas and a two-dimensional solution. The solution model has proved reasonably successful for fairly dilute films at the air/water surface. At higher coverages, an equation derived by Smith for liquid expanded monolayers gives a moderately good description of films of heptanol on water. A simple application of the solution model to adsorbed monolayers at the liquid/liquid interface met with little success. It is found however that two-dimensional gas equations describe such systems surprisingly well for fairly low surface concentrations.As part of the study, the activity coefficients of methyl dodecanoate, and the diethyl esters of pentan-1,5-dicarboxylic acid and decan-1,10-dicarboxylic acid, all in dilute solution in n-octane at 30 °C, have been determined.
The Kinetics and Mechanisms of Exchange in the Binary System Manganese(II) – Adenosine 5′-Triphosphate
Authors: Kuntz G. P. P. , Lam Yiu-Fai , Kotowycz George
Published: May 2006

31P n.m.r. studies on the Mn(II) – adenosine 5′-triphosphate system indicate that two n.m.r. exchange mechanisms are present in solution; namely, the Eigen–Tamm mechanism and the direct ligand exchange mechanism. Their respective contributions to the observed n.m.r. line-widths and hence to the n.m.r. exchange rate depend upon the concentration of the ligand ATP. Equations are developed to prove what n.m.r. "sees" for the Eigen–Tamm mechanism and these equations are applied to this study.
Kinetic, Electron Spin Resonance, and Product Studies of the Reaction Between 2,2-Diphenyl-1-picrylhydrazyl and 2,4,6- Tri-t-butylbenzenethiol
Authors: Flood James , Russell Kenneth E.
Published: May 2006

The reaction of 2,2-diphenyl-1-picrylhydrazyl (DPPH) with 2,4,6-tri-t-butylbenzenethiol (TBBT) in benzene solution has been studied. The two major products, 2,2-diphenyl-1-picrylhydrazine (DPPH-H) and di-(2,4,6-tri-t-butylphenyl) disulfide, are those anticipated for a reaction in which DPPH abstracts hydrogen from the thiol yielding thiyl radicals which undergo coupling to produce the disulfide. About 30% of the DPPH is converted into a derivative in which a nitro group has been displaced by a 2,4,6-tri-t-butylphenylthiyl group. Displacement of NO2 from DPPH by the tri-t-butylphenylthiyl radical is thought to constitute an important secondary reaction.In the presence of excess thiol, the rate constant for disappearance of DPPH, determined spectrophotometrically, is 1.23 ± 0.04 M−1 s−1 at 25 °C, and the activation energy is 5.8 ± 0.5 kcal mol−1. The rate of reaction is halved when the thiol is deuterated at the SH group, confirming that the primary step involves hydrogen transfer. Addition of DPPH-H retards the overall reaction indicating that this primary step is reversible.An e.s.r. study of the reacting solutions shows that the concentration of thiyl radical is relatively low until most of the DPPH disappears; it also shows the slow buildup of the 2,4,6-tri-t-butylphenylthiyl derivative of DPPH. The e.s.r. spectrum of the latter derivative has been analyzed and shown to be consistent with nitrogen coupling constants A1 = 10.4 ± 0.2 G and A2 = 6.45 ± 0.2 G.
Bond Scission in Sulfur Compounds. Part X. The Hydrazinolysis of Methyl p-Nitrophenyl Sulfate
Authors: Buncel Erwin , Chuaqui Claudio
Published: May 2006

Reaction of methyl p-nitrophenyl sulfate with the hydrazine – hydrazine hydrochloride system in methanol gives rise to different types of behavior depending on the state of ionization of the reagent. For the H2NNH2/H2NNH3+ combination the observed reaction is conversion of methyl p-nitrophenyl sulfate to p-nitrophenyl sulfate ion (alkyl–oxygen scission). For the H2NNH3+/+H3NNH3+ combination, or with +H3NNH3+ alone, one observes the consecutive processes methyl p-nitrophenyl sulfate → p-nitrophenyl sulfate ion → p-nitrophenol (alkyl–oxygen followed by sulphur–oxygen scission). For the alkyl–oxygen scission process, i.e. nucleophilic displacement on the alkyl carbon, the observed pseudo first-order rate constant is given by the contributions of several nucleophilic species; [Formula: see text] A method for the dissection of kobs into the constituent terms is given. The sulphur–oxygen scission process is an acid catalyzed reaction and the measured kinetic data have been utilized for the derivation of the pKa of +H3NNH3+ in methanol. Rate data for the conversion of sodium p-nitrophenyl sulfate to p-nitrophenol in methanol containing HCl have also been determined in this connection.
A Synthetic Approach To Cadinane- and Amorphane-Type Sesquiterpenoids via Annelation Of Cyclohexanone Derivatives With (E)-2-Methyl-3-hepten-5-one. A Simple Synthesis of (±)-Cadinene Dihydrochloride
Authors: Piers Edward , Phillips-Johnson Wynona M.
Published: May 2006

The annelation of the pyrrolidine enamine of cyclohexanone with (E)-2-methyl-3-hepten-5-one (7) afforded a 7:3 mixture of the octalones 12 and 13. Lithium–ammonia reduction of the former afforded the trans-fused decalone 14, whereas, in contrast, a similar reduction of 13 gave exclusively the cis-fused decalone 16. Annelation of the pyrrolidine enamine of 4-hydroxy-cyclohexanone with the unsaturated ketone 7 yielded a 7:3 mixture of the octalones 22 and 23. The former was converted via a short, efficient synthetic sequence into (±)-cadinene dihydrochloride (30).
The Chemical Ionization Mass Spectra of Fluorotoluenes
Authors: Harrison Alex. G. , Lin Ping-Huang
Published: May 2006

The methane and hydrogen chemical ionization mass spectra of benzyl fluoride, the isomeric fluorotoluenes, and fluorobenzene have been determined. Reaction mechanisms have been elucidated by using CD4 and D2 as reagent gases. Both the CH4 and H2 spectra of benzyl fluoride show C7H7+ as the major ion. In the CH4 spectra of the fluorotoluenes MH+ is the only abundant ion resulting from protonation while in the H2 chemical ionization spectra considerable loss of HF and H2 occurs from MH+. There is no evidence for ring expansion to form tropylium type ions. The novel reactions[Formula: see text]are important reaction modes for R = CH3 or H and indicate that a long-lived collision complex is formed between CH5+ or H3+ and the aromatic neutral.