bluuebunny/crossref_metadata_2025 huggingface dataset:
The Decomposition of Perchloric Acid on Metal Oxide Catalysts
Authors: Gilbert R. , Jacobs P. W. M.
Published: May 2006

The thermal decomposition of perchloric acid has been investigated on five Harshaw catalysts: copper chromite, alumina, iron(III) oxide, copper(II) oxide, and manganese(IV) oxide (the last three being supported on alumina). Manganese(IV) oxide gave complex kinetics which were not fully analyzed but on the other four catalysts the reaction was.first order. Activation energies were: copper chromite, 54 kcal/mol; alumina, 28.8 kcal/mol; iron(III) oxide, 28.6 kcal/mol; copper(II) oxide, 39.0 kcal/mol. A mechanism is proposed for the decomposition which involves proton transfer to an accepter (typically an O2− ion) in the catalyst surface followed by decomposition of the ClO4− anion formed in this process. Some observations on the catalyzed thermal decomposition of ammonium perchlorate are presented.
The Vapor Phase Radiolysis of Isopropanol and Water–Isopropanol Mixtures. II. Nitrous Oxide as Electron Scavenger
Authors: Bailey M. G. , Dixon R. S.
Published: May 2006

Nitrous oxide reduces the hydrogen yield from water–isopropanol vapor mixtures by complete scavenging of electrons. Nitrogen is produced over the whole concentration range but the yield at higher isopropanol concentrations is much greater than the electron yield. The results indicate a competition between water and isopropanol for a secondary species resulting from electron attachment to N2O. Reaction of this species with isoprooanol leads to further N2 whereas reaction with water does not. The reactive intermediate is most probably N2O− or N2O2−.
Transannular Cyclizations of 6-Substituted Cyclodecynes
Authors: Balf R. J. , Rao Balaji , Weiler Larry
Published: May 2006

A series of 6-substituted cyclodecynes has been synthesized and the transannular cyclizations of these compounds were studied. The observed transannular cyclizations were highly stereoselective and give products containing the bicyclo [4.4.0] decane skeleton.
Successive Nucleophilic Substitution at Four-Coordinate Boron. Some Novel Chelated and Polynuclear Boron(n + ) Salts
Authors: Genchur Sue A. , Smith Gary L. , Kelly Henry C.
Published: May 2006

Reactions of various polyamines with the mono- and diiodoborane adducts of trimethylamine yield chelated and polynuclear boron(n + ) ions. Treatment of excess trimethylamine-monoiodoborane with N,N′-dimethylpiperazine, triethylenediamine, and N,N,N′,N″,N″-pentamethyldiethylenetriamine give the corresponding di- and trinuclear salts. At about 30°, the diiodoborane combines with triethylenediamine to give a dinuclear ion, but in refluxing benzene, the product is a polynuclear salt. Trimethyl-amine-diiodoborane reacts with pentamethyldiethylenetriamine (in excess) to produce a bicyclic chelate. The reaction between N,N,N′,N′-tetramethylethylenediamine (TMED) and the diiodoborane gives two chelated products, [TMED(CH3)3NBH]2+•2I− and (TMEDBHI)+•I−. The latter salt, unlike its B-bromo and B-hydrido analogs, exhibits acidic behavior. This is tentatively explained by assuming a relatively high lability of the boron-bonded iodine.
Syothesis of 3-Deoxy-3-nitro-D-xylose
Authors: Kovář Jan , Baer Hans H.
Published: May 2006

Crystalline 3-deoxy-3-nitro-α-D-xylose (5) was obtained in 40% over-all yield by periodate oxidation of 3-deoxy-1,2-O-isopropylidene-3-nitro-α-D-glucofuranose (2) followed by borohydride reduction and acid hydrolysis. In addition to the intermediate 3-deoxy-1,2-O-isopropylidene-3-nitro-α-D-xylofuranose (4), a small amount of an isomer probably having the D-ribo configuration was isolated. The title compound (5) was also obtained by hydrolysis of its methyl β-pyranoside (1).
Radiolysis of Trifluoroacetic Acid
Authors: Betts J. , Cherniak E. A.
Published: May 2006

The gaseous products of the 60Co-γ radiolysis of liquid CF3COOH at 23 °C and solid CF3COOH at −196 °C have been identified and their G-values have been determined. The products and G-values are, for the radiolysis of liquid CF3COOH; CO2(7.1), CO(0.71), CF3H(0.27), C2F6(1.36), H2(0.031) and, for the radiolysis of solid CF3COOH; CO2(2.5), CF3H(0.30), C2F6(0.39). CO and H2 are not produced in the radiolysis of solid CF3COOH and CF4 and C2F4 are not produced in the radiolysis of solid and liquid CF3COOH. The mechanisms of gaseous product formation in the radiolysis of solid and liquid CF3COOH are compared.
The Configuration Dependent Cyclization of β-2-Hydroxyaroylacrylic Acids
Authors: Arora P. C. , Brassard P.
Published: May 2006

Several alleged chromanone-2-carboxylic acids were reexamined. Some were found to have the assigned structures but others are in fact 2-coumaranonylacetic acids. Diagnostic proof was obtained by analysis of the n.m.r. spectra of the corresponding reduced substances. Useful correlations of the spectra with the structures of the keto acids are proposed.
The Meyer Reaction of Phenylnitromethane in Acid. II. Reactions in Acid of Benzonitrile Oxide and Benzohydroxamic Acid
Authors: Edward J. T. , Tremaine P. H.
Published: May 2006

The kinetics of the transformation of benzonitrile oxide in dilute sulfuric acid into benzohydroxamic acid have been followed by u.v. spectrophotometry at a temperature near room temperature. A mechanism is proposed on the basis of the effects of substituents and sulfuric acid concentration.The rate profile for the hydrolysis of benzohydroxamic acid in hot dilute sulfuric acid has been obtained.The results of these studies are applied to the detailed mechanism of the Meyer rearrangement – hydrolysis of phenylnitromethane in acid.
The Analytical Reduction of Porphyrins to Pyrroles
Authors: Chapman R. A. , Roomi M. W. , Morton T. C. , Krajcarski D. T. , MacDonald S. F.
Published: May 2006

When porphyrins or related pigments are reduced by HI–AcOH, their meso-substituents (R = H or alkyl) appear as α-CH2R groups in the resulting pyrroles. The identification of the pyrroles, as by g.l.p.c., defines and orders the meso-substituents flanking each pair of peripheral substituents in the porphyrin. If one meso-substituent differs from the others, all the substituents about the two adjacent pyrrole nuclei are then ordered.The pyrroles can be reductively alkylated in situ, and symmetry then reduces their number when the aldehyde used (R.CHO) corresponds to a bridge and its meso-substituent. This may simplify the pyrrole mixtures, identify meso-substituents, or make pyrroles distinguishable by g.l.p.c.The critical pyrrole – propionic acids are separable as methyl esters by g.l.p.c. Desoxophylloerythrin and pyrophaeophorbides (the latter first reduced with potassium borohydride) are reduced to cyclo-penteno-pyrroles which reveal the isocyclic rings and the 5-substituents. The r.r.t.'s of relevant pyrroles are reported.
Association of the Butyl Alcohols and n-Decanol
Authors: Rajala G. E. , Crossley J.
Published: May 2006

The dielectric constants at 0.1 MHz of n-, iso-, sec-, and t-butanol and n-decanol each at nine concentrations in the range 0.2–1.0 mole fraction in cyclohexane, p-dioxane, mesitylene, and p-xylene have been measured at 25 °C. Apparent dipole moments and Kirkwood correlation factors have been evaluated. Cyclohexane is regarded as an inert solvent in which alcohol self association alone is considered responsible for the anomalous electric polarization. The other three solvents have a disassociating effect which increases p-xylene ≤ mesitylene < p-dioxane. At the lowest concentrations the alcohols have larger apparent dipole moments in these solvents than in cyclohexane. The opposite tends to be the case for the more concentrated alcohol solutions. The results suggest that alcohol association is initially dominated by the formation of small, weakly polar multimers, and eventually larger highly polar multimers predominate.
The Effect of Some 3-Oxygen Functions on the Simmons–Smith Methylenation of 5,6-Unsaturated Steroids
Authors: Templeton J. F. , Wie C. W.
Published: May 2006

The effect of 3α- and 3β-hydroxy, 3α- and 3β-acetoxy, 3-ethylene acetal, and 3α-methoxy derivatives of 5-cholestene on the addition of the Simmons–Smith reagent to the steroidal 5,6-double bond has been investigated. Reaction occurred only with epi-cholesterol to yield chiefly 3α-hydroxy-5,6α-cyclopropano-5α-cholestane. The 3α-ethyl ether, 3α-acetate, and a dialkoxymethane have been identified as byproducts. The p.m.r. and mass spectral data are given.
Autoxidation of 2,3-Dialkylindoles
Authors: McLean Stewart , Dmitrienko G. I.
Published: May 2006

Autoxidation of 2,3-dimethylindole leads to the formation of an oxidized dimer 6a, and 2-methyl-3-ethylindole gives rise to the corresponding product 6c under the same conditions. In contrast, 2-ethyl-3-methylindole resembles 2,3-diethylindole in behavior and forms 2-acetyl-3-methylindole via the 3-hydro-peroxyindolenine, which is an isolable intermediate. Some of the side reactions which occur under autoxidative conditions have been studied, and an attempt has been made to give a satisfactory unified rationalization of our results and those obtained for related autoxidations by numerous other workers.
Axial:Equatorial Rate Ratios. 1. Eliminations Leading to the Exocyclic Methylene Group
Authors: King J. F. , Coppen M. J.
Published: May 2006

Phenyl cis-4-t-butylcyclohexanemethyl sulfoxide (4) thermolyzes to 1-t-butyl-4-methylenecyclohexane (5) at 116 and 130° about five to six times faster than its trans (equatorial) epimer 6. cis-4-t-Butylcyclo-hexanemethyl bromide (7) undergoes elimination with potassium t-butoxide in t-butyl alcohol at 100° about nine times faster than its trans (equatorial) epimer 8. The rate difference found for the sulfoxides 4 and 6 is the first clear demonstration of steric acceleration (without any contribution from any reagent repulsion effect) in the formation of an exocyclic carbon–carbon double bond in a simple anchored cyclohexane System. The faster elimination from 7 (vs. 8) is ascribed primarily to steric acceleration; the experiment neither requires nor excludes the influence of non-bonding repulsions between the substrate and the attacking base.
Electron Spin Resonance of γ-Irradiated Taurine
Authors: Lind G. , Kewley R.
Published: May 2006

The 9.5 GHz electron spin resonance (e.s.r.) spectra of single crystal and powder samples of γ-irradiated taurine, [Formula: see text], have been recorded. Overlapping spectra from three distinct radicals are present. The first of these is the species SO3− with an isotropic g-value of 2.0035 and a 33S hyperfine coupling tensor with principal values 135.2, 99.2, and 97.9 G. The second radical is a π-electron species with the unpaired electron mainly on carbon and exhibiting hyperfine interaction from at least four protons, probably [Formula: see text] and with principal g-values 2.0021, 2.0027, and 2.0034. The third radical has principal g-values 2.0024, 2.0056, and 2.0097 and principal values of the 33S hyperfine tensor of 49.6, 9.1, and 1.2 G. The proposed structure for this radical is [Formula: see text]
Carboxylate Complexing of Iron(III). I. The Formation of Monoacetatoiron(III) in Aqueous Solution: Equilibria and Kinetics
Authors: Pandey R. N. , Smith W. MacF.
Published: May 2006

The kinetics and equilibria involved in the formation of monoacetatoiron(III) from iron(III) in aqueous solution has been investigated at ionic strength 0.50 M and temperatures ranging from 5.2 to 25 °C for kinetic studies and 5.2 to 41 °C for equilibria. The results support the view that the mechanism of the acid independent reaction involves the reactants FeOH2+ and CH3COOH in an interchange dissociative (Id) mechanism with ΔH≠ = 11.1 ± 2.2 kcal mol−1. The nature of the acid dependent reactions remains unresolved.
The Crystal and Molecular Structure of Two Thiathiophthen Nitrogen Isosteres
Authors: Leung F. , Nyburg S. C.
Published: May 2006

Three dimensional crystal structure analyses have been carried out on two nitrogen isosteres (a) 5 and (b) 6 using diffractometer data. The crystal data are: (a) system: monoclinic, P21/c; a = 7.350(3), b = 12.309(5), c = 23.268(8) Å, β = 118.35(8)°; (b) system: monoclinic, P21/c; a = 9.34(1), b = 9.58(1), c = 25.65(3) Å, β = 108.08(8)°.The S … S distances are 2.396(12) and 2.814(8) Å, respectively. This difference is an indication of the cleavage of the S—S "bond" in 5 when the terminal sulfur atom is methylated. The nature of the bonding of the outer sulfur atom in 6 is discussed.
Deuterium Isotope Effects in the Reduction of Cyclohexanones. The Concepts of Steric Approach Control and Product Development Control
Authors: Wigfield Donald C. , Phelps David J.
Published: May 2006

Definitions for the terms stericapproachcontrol and productdevelopmentcontrol in relation to the degree of bonding in the transition state are put forward. Kinetic deuterium isotope effects in the reduction of a graded series of ketones by NaBH4 and NaBD4 have been measured. These effects are inverse, and show no systematic dependence on the degree of steric hindrance of the ketone. This evidence appears to invalidate the steric approach control – product development control explanation of the axial to equatorial product ratios (1). The primary isotope effect is very small, which is consistent with an early transition state in these reductions, as demanded by other explanations of product ratios, but since several other factors causing small isotope effects may be applicable, the evidence does not constitute proof of an early transition state.The main conclusions of this work have already been published in preliminary form (2).
Phase Equilibria in the Systems Acetone–Methanol, Acetone–Cyclohexane, Methanol–Cyclohexane, and Acetone–Methanol–Cyclohexane
Authors: Campbell A. N. , Anand S. C.
Published: May 2006

The vapor pressure and vapor composition of the methanol–cyclohexane system were investigated at temperatures ranging from 25 to 50°. The same properties of the binary systems: acetone–methanol and acetone–cyclohexane, as well as those of the ternary system: methanol–cyclohexane–acetone, were determined experimentally at 25°. The total pressures and compositions of the vapor for solutions lying close to the critical solution temperature of the binary system or close to the plait point of the ternary system are constant within the range of experimental accuracy. All these systems show azeotropic behavior. The methanol–cyclohexane system has an equimolar excess Gibbs free energy, GE, at 25° of 384.7 cal/mol, while the corresponding equimolar value of GE for the acetone–methanol system at 25° is 102.6 and for the acetone–cyclohexane system, at 25°, it is 274.5 cal/mol.
Reaction of Diphenylcyclopropenethione with Pyridinium Imines
Authors: Lown J. W. , Matsumoto K.
Published: May 2006

Reaction of diphenylcyclopropenethione with a variety of N-substituted pyridinium imines in refluxing benzene gives 2,4,5-trisubstituted-6H-1,3-oxazin-6-thiones in good to excellent yields. The structure of 2,4,5-triphenyl-6H-1,3-oxazin-6-thione prepared in this manner was proven by oxidation and by hydrolysis to the known 2,4,5-triphenyl-6H-1,3-oxazin-6-one. In the preparation of 4,5-diphenyl-2-ethoxy-6H-1,3-oxazin-6-thione changing the heteroaromatic residue in the imine from pyridine to 3-picoline to 3,5-lutidine had little effect on the yield (about 60%).
The Nature of the Tricyclic Dimer Formed from Acetonylacetone and Hydrazine: An Application of 13C Nuclear Magnetic Resonance
Authors: Mayo P. de , Stothers J. B. , Usselman M. C.
Published: May 2006

The structure of the dimer formed from acetonylacetone and hydrazine has been re-examined. On the basis of chemical and spectroscopic data, a covalent tricyclic structure is proposed.
The Preparation and Acetolyses of 5-Deuteriated exo-2-Norbornyl-p-bromobenzenesulfonates
Authors: Werstiuk N. H. , MacDonald R. R. , Ouwehand R. W. , Chan W. L. , Cappelli F. P. , Ballard J. G. , Young R. E. , Massey R. E. , Timmins G. , Goodwin I. , Walling A. , Teruta Miss Y.
Published: May 2006

The deuterionorborneols 2a, b, c, and e have been prepared and converted to the brosylates 1a, b, c, and e. The deuterium isotope effects determined spectrophotometrically for solvolysis in HOAc–KOAc are 1.00 ± 0.01, 1.01 ± 0.01, 0.99 ± 0.01, and 1.11 ± 0.01, respectively. These data establish that: (a) a steric deuterium isotope effect does not operate at C-5 and therefore probably not at C-6; (b) hyperconjugative stabilization of the norbornonium ion to the C-5 hydrogens is confirmed to be not important, and (c) provides the first experimental evidence that the hydrogen (deuterium) shift – internal return pathway contribution to the γ-deuterium isotope effects observed for 1d and e is minor.
Conformational Terminology for Crystalline Cellulose
Authors: Sundararajan P. R. , Marchessault R. H.
Published: May 2006

Two different crystalline models of cellulose have received attention from crystallographers: the "straight chain" model of Meyer and Misch and the "bent chain" model of P. H. Hermans. We have examined these models and have given a mathematical interpretation of each in terms of the conformational angles [Formula: see text] and ψ and the glycosidic angle τ. For a given geometry of the glucose residue, the "straight chain" corresponds to a unique value of τ; for a value of τ greater than the unique value, two "bent chains" are possible, one allowing an intramolecular hydrogen bond (O-3 … O-5′) and the other not. It is suggested that the former only be referred to as the Hermans conformation.
Carbon-13 Chemical Shifts of Methylcyclohexanes, Cyclohexanols, α- and β-D-Glucose and their Relation to Carbon Electron Densities from the Extended Hückel and Del Re Theories
Authors: Cyr N. , Perlin A. S. , Whitehead M. A.
Published: May 2006

An evaluation is made of the extent to which 13C chemical shifts of diastereoisomeric cyclohexane derivatives and pyranoses are related to electron density. Values of the latter for carbon atoms in cyclohexane, methylcyclohexanes, cyclohexanols, and D-glucose are calculated using the Extended Hückel Theory (EHT), with and without iteration, and the Del Re theory. It is shown that when electronegativities of all of the atoms are similar then the theories do not give electron densities which correlate with the 13C chemical shifts; when a strongly electronegative atom, such as oxygen, is present, the electron density differences are greater than the inaccuracy in the calculated individual densities and a fair correlation with 13C chemical shifts is obtained. Iteration is shown to give lower carbon electron densities and a better correlation.
3-Ketoglutarates: Compounds with Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Mg, and Na
Authors: Yerhoff F. W. , Larson D. W.
Published: May 2006

Where A designates the dinegative 3-ketoglutarate ion and L indicates a trinegative species (likely the enolate ion), the following compounds have been obtained: Na2A, NaCuL.XH2O, MgA.XH2O, MnA.XH2O, CoA.XH2O, NiA.XH2O. Hydration numbers are uncertain. Stoichiometry of Cu(II) and Zn(II) compounds could not be established. Structures have been assigned on the basis of the infrared spectra. Na2A appears to be a simple ionic carboxylate. MgA, MnA, CoA, and NiA are assigned a similar structure, with unidentate carboxylate coordination and hydrogen-bonded coordination between the metal and the second carboxylate oxygen (through water). NaCuL is assigned a metal-bridged polymer structure. There is not significant metal interaction with the carbonyl oxygen in any of the proposed structures.
Isothermal Compressibilities of Aqueous Solutions of Tetraalkylammonium Bromides
Authors: Desnoyers J. E. , Philip P. R.
Published: May 2006

The standard isothermal apparent molal compressibilities, [Formula: see text] of tetraalkylammonium bromides in water at 25° were calculated from known standard apparent molal adiabatic compressibilities, [Formula: see text] expansitivites, [Formula: see text] and heat capacities, [Formula: see text] is significantly different from [Formula: see text] and depends mostly on the extrapolation procedure used to obtain [Formula: see text] and on the precision of [Formula: see text]
The Effect of Heat on cis- and trans-Crotonic Acids: Alternatives to Direct cis–trans Isomerism
Authors: Hocking M. B.
Published: May 2006

The thermal cis–trans equilibration of cis- and trans-crotonic acids (2-butenoic acids) has been examined at temperatures in the range 100–189°. The trans acid has been found to yield a mixture of at least five components, of which 9–11.6% was cis-crotonic acid, and 19.4–31.7% was a dimer of trans-crotonic acid. Heating cis-crotonic acid yielded similar final mixtures, but with an initial component of vinylacetic acid, not seen in the trans acid equilibrations. The rates of formation and identities of the components formed in these two sets of experiments, together with data for the thermal tautomerization of vinylacetic acid, are discussed with reference to suggested pathways for these transformations.
A Proton Nuclear Magnetic Resonance Study of the Exchange Reactions of Acetonitrile – Boron Trihalide Adducts with Excess Acetonitrile
Authors: Fogelman J. , Miller J. M.
Published: May 2006

Proton n.m.r. studies of the mechanism for exchange of excess acetonitrile with CH3CN•BX3 (X = F, Cl, Br) adducts show that the rates and activation energy for dissociation are influenced by solvent effects when mixed solvents such as C6H5NO2/CH2Cl2 or CD3NO2/CH2Cl2 are used. On extrapolation to inert solvent conditions, first order activation energies are obtained which are in close agreement with previously measured dissociation energies of acetonitrile adducts in solution. The relative rates of dissociation are CH3CN•BF3 > CH3CN•BCl3 > CH3CN•BBr3; in agreement with previous experimental evidence that the strength of the donor–acceptor band varies as CH3CN•BBr3 > CH3CN•BCl3 > CH3CN•BF3.
13C Nuclear Magnetic Resonance Studies. XX. 13C Shieldings of Several Allyl Alcohols. Geometric Dependence of 13C Shieldings
Authors: Brouwer H. , Stothers J. B.
Published: May 2006

The 13C spectra of 21 methyl- and halo-substituted 2-propenols have been determined. The shielding data are discussed with particular emphasis on their dependence on the orientation of the 3-halo substituents. Linear regression analyses of the results gave sets of additive parameters which correlate the shieldings with reasonable precision (≤ 1 p.p.m.). A similar set of parameters has been generated from the published data for acyclic alkenes: these parameter sets are intercompared. The results of complete analysis of the proton spectra of most of the alcohols are also presented.
Spectroscopie de masse des gem-diesters épimères
Authors: Jankowski Krzysztof , Couturier Jean , Tower Robert
Published: May 2006

The analysis of mass spectra of three 2-substituted dihydropyran gem-diesters is presented. The retro-Diels–Alder fragmentation, absent in the other members of the group, was identified. The major fragmentation was the aromatization of the dihydropyran ring.
The Wetting Properties of Aqueous Solutions of Valeric Acid on Solid Surfaces
Authors: Ponter A. B. , Boyes A. P.
Published: May 2006

Contact angles are reported for aqueous solutions of valeric acid on copper, stainless steel and polytetrafluoroethylene surfaces in equilibrium with their own vapors at atmospheric pressure and 25 °C. It is demonstrated that the dependency on concentration for the polytetrafluoroethylene surface is in accord with theory.
Adsorption of Co2+ by Oxides from Aqueous Solution
Authors: Tewari P. H. , Campbell A. B. , Lee Woon
Published: May 2006

The adsorption of Co(II) by Fe3O4, Al2O3, and MnO2 has been studied as a function of Co(II) concentration, solution-pH, and temperature. It is observed that the adsorption of cobalt increases markedly with the solution pH between pH 5 and 7.5. Above pH 8 adsorption becomes increasingly masked by precipitation of Co(OH)2 and no resolution of these two contributions to the loss of Co(II) from solution is possible. A log θ/(1–θ) vs. pH plot is found to be linear between pH 5 and 7.5, where θ is the fraction of occupied adsorption sites. The presence of 0.1 m Ba2+ and Mg2+ in the solution does not seem to affect the hydrogen ion dependence of the adsorption of Co(II) on alumina.The adsorption results have been analyzed by the Langmuir adsorption isotherm over a wide range of Co(II) concentration (10−6–10−3 m). The adsorption of Co(II) is found to be an endothermic process and increases markedly with temperature between 30 and 100 °C. The heat of adsorption decreases with increasing surface coverage of the oxides. At saturation coverage, the heats of adsorption for Co(II) on Al2O3, MnO2, and Fe3O4 are −14.9, −14.3, and −6.3 kcal/mol, respectively. Hydrolysis of Co(II) is suggested as a possible mechanism for the marked dependence of adsorption on pH and temperature.
Studies of β-Diketone Complexes of Rhenium. Part II. Physical Studies of Dihalobis(pentane-2,4-dionato)rhenium(IV) Compounds
Authors: Courrier W. D. , Lock C. J. L. , Turner G.
Published: May 2006

Studies on trans-Re(acac)2Cl2 in the solid state, solution, and gas phases by spectroscopic and classical physical methods show that the compound is a monomer and not a dimer as previously claimed (2). cis-Re(acac)2Cl2, Re(acac)2Br2, Re(acac)2I2, and Re(dbm)2Cl2 have been prepared for the first time and corresponding physical measurements are reported.
The Concentration Dependence at 1 atm Pressure and 300 °K of the Binary Diffusion Coefficients of the Systems Helium – Carbon Dioxide, Helium – Nitrous Oxide, and Helium – Sulfur Hexafluoride
Authors: Harris Kenneth R. , Bell T. N. , Dunlop Peter J.
Published: May 2006

Binary diffusion coefficients are reported for the systems He–CO2, He–N2O, and He–SF6. In agreement with the Chapman–Enskog theory the concentration dependence of the diffusion coefficient of each system increases with the mole fraction of the heavier component.
Studies in Solvolysis. Part IV. Substituent and Solvent Isotope Effects in the Solvolysis of a Series of Benzyl Trifluoroacetates
Authors: Winter June G. , Scott J. M. W.
Published: May 2006

The rates of neutral hydrolysis of a series of 4-substituted benzyl trifluoroacetates 4-X-C6H4CH2OCOCF3, X = NO2, Cl, H, CH3, and OCH3 have been studied in water and deuterium oxide, both solvents containing 0.012 mol fraction of acetone. The alteration of the rates with the nature of the 4-substituent and the kinetic solvent isotope effect (k(H2O)/k(D2O)) are consistent with the proposal that the esters with X = NO2, Cl, H, and CH3 all react by an acyl–oxygen BAc2 mechanism. On the other hand, the same mechanistic criteria indicate that the 4-methoxybenzyl ester reacts by both the BAc2 and the SN1 alkyl–oxygen fission paths in equal amounts.
13C Nuclear Magnetic Resonance of Oximes. I. Solvent and Isotope Effects on the 13C Chemical Shifts of Acetoxime
Authors: Gurudata N.
Published: May 2006

The 13C n.m.r. spectrum of acetoxime has been obtained in five representative solvents and the chemical shifts of the three carbon atoms measured. The solvent effects on the chemical shifts are found to reflect specific solute–solvent interactions. The effect of deuteration of the α-protons on the chemical shift of the oximino carbon is also discussed.
Benzene Radical Cation Formation on Hydrogen Mordenite. The Role of Adsorbed Oxygen
Authors: Sagert N. H. , Pouteau R. M. L. , Bailey M. G. , Sargent F. P.
Published: May 2006

The e.p.r. spectrum of benzene on hydrogen mordenite (Zeolon H) has been studied as a function of coverage, degassing temperature, and hydrogen and oxygen treatment. The initial spectrum observed was that due to the benzene cation radical dimer. The maximum number of spins was formed when the solid was completely saturated with benzene. Large yields were obtained only when the zeolitic water and water of hydration of the protons were removed. The largest yields were observed where significant dehydroxylation had occurred. Chemisorbed oxygen was essential, and there was a 1:1.2 ratio between the maximum number of spins observed in the presence of excess oxygen and the amount of oxygen chemisorbed. The largest concentration of radical cations noted (2 × 1018/g) was much smaller than the number of acid sites known to be present (1021/g). In fact, only one unit cell of the hydrogen mordenite in 100 had a site capable of oxidizing benzene to the cation. Hence these sites must be in special positions in the solid.
A Transient Intermediate in the Bimolecular Reaction of Hydrated Electrons
Authors: Basco N. , Kenney-Wallace G. A. , Vidyarthi S. K. , Walker D. C.
Published: May 2006

Further studies are reported which attempt to identify the transient species (X) produced from hydrated electrons which may be photodissociated to re-form [Formula: see text] The method used involves the production of [Formula: see text] by u.v. flash photolysis of aqueous OH−/H2 solutions followed, after any specified delay, by a second and third photoflash of restricted wavelengths. Photoregeneration of [Formula: see text] is effected by light in the spectral range 320 to 400 nm, not at λ > 700 nm as earlier reported (1). The species X is much longer lived than [Formula: see text] having a mean lifetime of ∼5 ms at pH 11, but this is very dependent on the lifetime of [Formula: see text] in the system. Two conditions seem to be necessary in order to detect the presence of X, (i) [Formula: see text] must decay to a considerable extent through the bimolecular dimerisation reaction and (ii) the lifetime of [Formula: see text] with respect to all other reactions must be >ca. 200 μs. Thus it is not expected to be observable in most pulse radiolysis studies. Its extinction coefficient in that part of its absorption band which leads to photodissociation (320–400 nm) is estimated to average >2000 M−1 cm−1, may be as high as 6000 M−1 cm−1 at 347 nm but does not exceed 12 000 M−1 cm−1 at any wavelength. Its identity is discussed and it is concluded that X is probably the hydrated electron dimer, [Formula: see text] or a product formed there from by association with a cation.
Conformational Studies of Acyclic Organophosphate Esters using Nuclear Magnetic Resonance Spectroscopy
Authors: Donaldson Bruce , Hall L. D.
Published: May 2006

The vicinal31P—O—C—1H couplings of a series of acyclic phosphate esters have been measured and rationalized in terms of varying populations of individual rotamers. Variable temperature measurements have been interpreted in terms of the enthalpy and entropy differences between gauche and trans rotational isomers.
Concerning the Discrepancies in the Reported Infrared Spectra of Dibenzo[a, e]cyclooctatetraene
Authors: Cutshall Theodore W. , Rabideau Peter W.
Published: May 2006

Controversy has existed concerning the several syntheses of dibenzo[a,e]cyclooctatetraene. This controversy has resulted from a discrepancy with the i.r. spectrum contained in one of the original preparations with subsequent samples. We have prepared this hydrocarbon, together with 7-methylenedibenzo[a,e]cycloheptatriene, and have concluded that this discrepancy has arisen from a mixup of spectra (or samples) with this latter hydrocarbon.
The Self-Reaction of sec-Alkylperoxy Radicals: A Kinetic Electron Spin Resonance Study
Authors: Howard J. A. , Bennett J. E.
Published: May 2006

Absolute rate constants for the self-reaction of cyclopentylperoxy, cyclopentenylperoxy, and sec-butylperoxyradicals have been determined over a 125 °C temperature range. Arrhenius plots derived from these rate constants suggest that the mechanism for this reaction is more complex than the currently accepted Russell mechanism.
A Stereospecific Synthesis of Ring A-aromatic Steroids
Authors: Dickinson R. A. , Kubela R. , MacAlpine G. A. , Stojanac Z. , Valenta Z.
Published: May 2006

A diene synthesis using 2,6-xyloquinone as dienophile and boron trifluoride as catalyst does not follow the normal orientation rules and leads to a facile synthesis of ring A-aromatic steroids. A tetracyclic adduct prepared by a similar reaction and containing the steroidal C19-methyl group is also reported.
The Molecular and Crystal Structure of an Oxindole Alkaloid (6-Hydroxy-2′-(2-methylpropyl)-3,3′-spirotetrahydropyrrolidino-oxindole)
Authors: James M. N. G. , Williams G. J. B.
Published: May 2006

A previously unknown alkaloid of molecular formula C15H20O2N2 was isolated from the dried root bark of EleagnusCommutata (Wolf willow or Silverberry). An X-ray analysis was undertaken to complete the structural characterization of the molecule. Columnar crystals obtained from diethyl ether have the unit cell constants, a = 13.1949(10) Å, b = 9.4525(6) Å, c = 12.1186(6) Å, β = 109°47(1)′ and belong to space group P21/c. The structure was solved using an automated symbolic addition procedure and refined by block-diagonal least-squares to weighted and unweighted R factors of 6.25% and 4.30%, respectively. The previous structural studies were shown to be essentially correct except for the incorrect placement of the phenolic hydroxyl on C(5) of the oxindole nucleus. The correct molecular structure is implied by the systematic name given. The —OH group engages in two intermolecular hydrogen bonds with the two nitrogen atoms, but the carbonyl moiety is not involved in any such interactions.
Complex Fluorides of Tetravalent Cobalt
Authors: Quail J. W. , Rivett G. A.
Published: May 2006

A new compound, Rb2CoF6 has been prepared. Rb2CoF6 and Cs2CoF6 both have the cubic K2PtCl6 structure with a = 8.460(3) Å and d(Co—F) = 1.65(5) Å for Rb2CoF6 and a = 8.914(2) Å and d(Co—F) = 1.73(5) Å for Cs2CoF6. The temperature dependent magnetic susceptibilities of Rb2CoF6 and Cs2CoF6 are reported and interpreted. The data are consistent with the CoIV having a 2T2 ground state and both Rb2CoF6 and Cs2CoF6 exhibiting complex ferromagnetic behavior with a Curie temperature above ambient.
Influence des paramètres géométriques sur la résistance d'une cellule électrolytique
Authors: Sisi J. C. , Dubeau C. , Pélissier J. P. , Mitnyan L.
Published: May 2006

The resistance of an aqueous solution of K2SO4 in an electrolytic cell has been calculated theoretically as a function of geometric parameters of the cell. The calculated values have been verified with a new experimental method using an alternating current of 2000 cycles.
Potentiometric Titration of Fulvic Acid: Equivalence Point Calculations and Acidic Functional Groups
Authors: Gamble Donald S.
Published: May 2006

Gran's functions corrected for buffering and H2O dissociation have been incorporated into the iterative calculation for the two equivalence points and the acid dissociation equilibria. The experimental and mathematical conditions required for accurate, dependable operation of the method have been examined. The resulting equivalence point calculations are based directly on a chemical interpretation of the system, without approximations. The first equivalence point is shigher than previously reported, and is displaced upward by KCl. Detailed chemical information has been obtained for some of the acidic functional groups, from plots of KA = (mHδmA/δmAH) vs. mequiv./g. Carboxyl groups at the chelating sites are essentially all ionized for H+ concentrations less than 1 × 10−5 m.
Mass Spectra of β-Keto Esters
Authors: Weiler Larry
Published: May 2006

The mass spectra of several γ-substituted β-keto esters have been recorded and interpreted. The fragmentation patterns are compared to those of α-substituted β-keto esters and are found to be very useful in differentiating the α- and γ-substituted isomers. The mass spectral fragmentation schemes are dominated by cleavages α to the carbonyl groups and by McLafferty rearrangements.
Doubling Proton Magnetic Resonance Signals by Use of Tris(dipivalomethanato)europium(III)
Authors: Joseph-Nathan P. , Herz J. E. , Rodríguez V. M.
Published: May 2006

Doubling of some p.m.r. signals from some steroidal diastereoisomers following treatment with the shift reagent, (DPM)3Eu(III), is reported for the first time. Similar examination of the hemithioethyleneketal of methyl isopropyl ketone provided the first evidence for the diastereotopic nature of the methyl groups of the isopropyl moiety of this compound. The resolution of signals from diastereoisomers and the failure to detect the diastereotopic nature of the methylene protons of different hemithioethyleneketals is discussed briefly in terms of inhibition of free rotation in pseudocontact association.
Electronic Spectrum of Cobalt(II) in Sulfates. Part III. Equilibrium Studies in Li2SO4–DMSO Solution and in NaHSO4−KHSO4 Melt
Authors: Dickinson J. R. , Stone M. E.
Published: May 2006

The results of a study of the electronic absorption spectrum of cobalt(II) in Li2SO4–DMSO solution, an equimolar NaHSO4–KHSO4 melt, a eutectic melt of Li2SO4–Na2SO4–K2SO4, single salt melts of Li2SO4 and Na2SO4 and a doped single crystal of K2Zn2(SO4)3 have been combined with previous results in sulfate media; all the results can be explained in terms of a blue dodecahedral [Co(O2SO2)4]6− species, a pink octahedral [Co(OSO3)6]10− species or an equilibrium mixture of the two.
Model Calculations on the Influence of Mechanical and Electrical Anharmonicity on Infrared Intensities: Relation to Hydrogen Bonding
Authors: Paolo Thérèse Di , Bourdéron C. , Sandorfy C.
Published: May 2006

The influence of mechanical and electrical anharmonicity on the intensity of X—H stretching vibrations is investigated by means of model calculations in relation to hydrogen bonding. It is found that while both kinds of anharmonicities have a significant effect on the intensity, they cannot explain the characteristic increase in intensity of the fundamental and the equally characteristic decrease in the intensity of the first overtone. It is shown that not only the first but both these phenomena are due to the large value of the first derivative of the dipole moment in hydrogen bonded systems. This is linked to the possibility that the effect of electrical anharmonicity (d2μ/dQ2) might be cancelled by a high value of (dμ/dQ)c in the expression of the overtone intensity.
Sequence Studies in Biosynthesis: Trichothecin
Authors: Forrester J. M. , Money T.
Published: May 2006

An investigation of the precursor activity of α-bisabolol, γ-bisabolene and monocyclofarnesol indicates that these compounds are not intermediates in the biosynthesis of trichothecin.
The Importance of Conformation in the Ozonolysis of Acetals
Authors: Deslongchamps Pierre , Moreau Claude , Fréhel Daniel , Atlani Paul
Published: May 2006

Six gauche conformations are theoretically possible for an acetal function and only three of them are reactive toward ozone. Each oxygen of the acetal function must have an electron pair orbital oreitned antiperiplanar to the C—H bond in order to be reactive toward ozone.
Studies of the Metal–Sulfur Bond. Complexes of the Pyridine Thiols
Authors: Kennedy B. P. , Lever A. B. P.
Published: May 2006

Complexes of 2-pyridine thiol, 4-pyridine thiol, and 2-methyl-6-pyridine thiol, and some of their oxygen analogs with cobalt(II), nickel(II), zinc(II), cadmium(II), mercury(II), platinum(II), bismuth(III), and tin(IV) are characterized. On the basis of vibrational (conventional and far infrared) and electronic spectroscopy, magnetism, conductivity, and X-ray powder diffraction, the structures of these complexes are identified. In the thiol complexes, the bonding occurs, in all cases, through the sulfur, rather than the nitrogen atom. Bonding through oxygen is confirmed for the hydroxypyridine analogs. Tetrahedral [Formula: see text] chromophores are identified for M = Co(II), Zn(II), and Cd(II), whilst square [Formula: see text] chromophores occur with M = Ni(II) and Pt(II). The complexes exhibit sulfur-to-metal charge transfer spectra from which the optical electro-negativities of the thiol ligands are shown to be near 2.4. Spectroscopic parameters for the complexes are derived and compared, together with their oxygen analogs, against phosphorus and arsenic sulfides and oxides.
The Hydrate of Hexafluorophosphoric Acid
Authors: Davidson D. W. , Garg S. K.
Published: May 2006

HPF6 is said to form a hexahydrate of a unique clathrate structure in which [Formula: see text] ions occupy truncated-octahedral cages in a framework of hydrogen-bonded water molecules. N.m.r. studies show, however, that appreciable quantities of HF are incorporated in the lattice and that the composition is more properly [Formula: see text], a result supported by chemical analysis. H3O+ and HF appear to be distributed over the lattice sites previously assigned to water molecules so as to involve all H atoms in the hydrogen bonding. The 1H resonance line is narrowed by rapid proton diffusion down to 150 °K. The 19F line of encaged [Formula: see text] is narrowed by rotation above 75 °K and reaches the rigid-lattice shape only below 25 °K.
Rhodium(I) and (III) Complexes of Some Phospholes and Their Behavior as Homogeneous Hydrogenation Catalysts
Authors: Holah David G. , Hughes Alan N. , Hui Benjamin C.
Published: May 2006

Reactions between rhodium(III) chloride hydrate and certain phospholes are described; these result in the formation of both Rh (III) and Rh (I) complexes. The phospholes also react with Rh (I) carbonyl and ethylene complexes. The products of these reactions were investigated as homogeneous catalysts in the hydrogenation of 1-hexene, and some show relative rates of hydrogenation comparable with that of hydridocarbonyltris(triphenylphosphine)rhodium(I) but slower than that of tris(triphenylphosphine)rhodium (I) chloride.
Isomérisation des épisulfures
Authors: Jankowski Krzysztof , Harvey Ronald
Published: May 2006

Stereoisomerisation of some episulfides was observed using the reaction of potassium thiocyanate in DMF or water–ethanol. The stereoisomerisation was followed by n.m.r.
Synthesis and Reactions of Strained Hydrocarbons Possessing Inverted Carbon Atoms. Tetracyclo[3.3.1.13.7.01.3]decanes
Authors: Pincock R. E. , Schmidt J. , Scott W. B. , Torupka E. J.
Published: May 2006

Tetracyclo[3.3.1.13.7.01..3]decane (i.e., 1,3-dehydroadamantane or DHA) and its 5,7-dimethyl derivative may be synthesized from the corresponding 1,3-dibromoadamantane compounds with sodium–potassium alloy in ether or heptane. These highly strained cyclopropyl compounds are very reactive towards free radical and electrophilic reagents. They homopolymerize 140–160° to thermally resistant, insoluble materials and spontaneously copolymerize with oxygen in solvents at room temperature. Reaction with bromine in ether at −70° yields an intermediate bromoadamantyloxonium tribromide which decomposes to 1-bromo-3-ethoxyadamantane on warming. Other rapid reactions of these strained 1,3-dehydroadamantanes are reported.
Free Radicals by Mass Spectrometry. XLV. Ionization Potentials and Heats of Formation of C3H3, C3H5, and C4H7 Radicals and Ions
Authors: Lossing F. P.
Published: May 2006

Using an energy-resolved electron beam, appearance potentials for[Formula: see text],[Formula: see text], and [Formula: see text] fragment ions from hydrocarbons of formula C3H4, C3H6, C4H6, C4H8, and C5H10 have been measured. In each case the fragment appears to have a common structure, corresponding to [Formula: see text], [Formula: see text], and [Formula: see text]. Ionization potentials have been measured for propargyl radical (8.68 V), methallyl radical (7.54 V), and 2-methylallyl radical (7.89 V). Corresponding ionic heats of formation are propargyl 281 ± 3 kcal/mol, methallyl 204 ± 3 kcal/mol, and 2-methylallyl 211 ± 5 kcal/mol. The [Formula: see text] fragment ion is 25 kcal/mol more stable than propargyl ion, and is almost certainly cyclopropenyl ion. Ionization potentials for propyne, allene, cyclopropene, 1- and 2-butyne, and fifteen isomers of formula CnH2n have also been measured by monoenergetic electron impact.
The Preparation and Paramagnetic Susceptibility of β-MnSe
Authors: Murray Ritchie MacLaren , Forbes Brian Charles , Heyding Robert Donald
Published: May 2006

A procedure is given for the preparation of β-MnSe by precipitation from solution. The cubic B3 zinc blende type structure has a unit cell dimension of 5.88 ± 1 Å. The magnetic susceptibility obeys the Curie–Weiss law above 110 °K with C = 3.64 ± 14 and θ = 444 ± 13, equivalent to an effective moment of 5.40 μB.
Reduction of Isopropyl Tri-O-acetyl-2-oximino-α-D-hexopyranosides
Authors: Lemieux R. U. , James K. , Nagabhushan T. L. , Ito Y.
Published: May 2006

Hydrogénation of 2-oximino-α-D-arabino-hexopyranosides in the presence of palladium and hydrazine provided high stereoselectivity for the formation of 2-amino-2-deoxy-α-D-glucopyranosides including disaccharide structures. Similar yields of gluco-isomer were normally obtained on reduction by borane of 2-acetoximino-tri-O-acetyl-α-D-arabino-hexopyranosides in tetrahydrofuran. However, reduction of 2-O-(2-acetoximino-tri-O-acetyl-α-D-arabino-hexopyranosyl)-1,3-dibenzoylglycerol provided a ratio of about 3:2 of the gluco-to manno-isomers. Reductions with lithium aluminum hydride were not appreciably stereoselective. Treatment of isopropyl 2-oximino-α-D-arabino-hexopyranoside with hydrazine in the presence of palladium catalyst gave isopropyl 2-deoxy-α-D-arabino-hexopyranoside in a novel room-temperature Wolff–Kishner type reaction.Reduction of isopropyl tri-O-acetyl 2-oximino-α-D-lyxo-hexopyranoside both with borane and lithium aluminum hydride proceeded with slight stereoselectivity for the galacto-isomer.
Chemical Synthesis of α-Linked 2′-Amino-2′-deoxydisaccharides
Authors: Lemieux R. U. , James K. , Nagabhushan T. L.
Published: May 2006

The reduction by borane in tetrahydrofuran of the 2-acetoximino-tri-O-acetyl-α-D-arabino-hexo-pyranosyl derivatives of 1,2;3,4-di-O-isopropylidene-α-D-galactopyranose and 1,2;5,6-di-O-isopropylidene-α-D-glucofuranose (1 and 4, respectively) proceeds with a high degree of stereoselectivity for the α-D-gluco-configuration and affords a convenient route to 2-amino-2-deoxy-α-D-glucopyranosides. The reduction of the corresponding 2-acetoximino-tri-O-acetyl-α-D-lyxo-hexopyranosyl derivatives (7 and 12) proceeds with slight stereoselectivity favoring the α-D-talo-configuration. Chromatographic separation was required to provide the N-acetyl derivatives of 2-amino-2-deoxy-α-D-galactopyranosides and 2-amino-2-deoxy-α-D-talopyranosides.
Refinement of the Crystal Structure of Synthetic Chervetite, Pb2V2O7
Authors: Shannon Robert D. , Calvo Crispin
Published: May 2006

The structure of synthetic chervetite has been refined by full matrix least-squares to a ωR = 0.029 using 1105 reflections. Unit cell dimensions are a = 13.3689(7), b = 7.1607(4), c = 7.1027(4) Å, β = 105935(5)°, and the space group is P21/a. The structure, originally solved by Kawahara, is a dichromate-type structure with a V2O74− group eclipsed to within 11 ± 5°. The Pb2+ ions are irregularly coordinated to 8 or 9 oxygens with distances from 2.40 to 3.20 Å. The distortion of the Pb–O distances is considerably greater than the corresponding distortions of the Sr–O distances in the similar β-Sr2V2O7 structure and is related to the tendency of Pb2+ to form directional covalent bonds. The V–O distances range from 1,665 to 1.720 Å for terminal oxygens and are 1.812 and 1.821 Å for the bridging oxygens. The V–O distances are consistent with the strengths of the Pb—O bonds.
Raman and Infrared Studies of Hexa-, Tetra-, and Dihydrates of Crystalline Magnesium Nitrate
Authors: Chang Tien-Chung Godfrey , Irish Donald E.
Published: May 2006

Raman and infrared spectra of Mg(NO3)2•6H2O, Mg(NO3)2•6D2O and partially dehydrated products have been obtained and assigned. As the water content is reduced a different set of lines appears and maximizes at the composition Mg(NO3)2 4H2O On further dehydration a third set of lines characteristic of Mg(NO3)2•2H2O appears. The existence of the metastable tetrahydrate had not been confirmed since it was reported in 1932. The spectra suggest that four equatorial sites aroung Mg2+ in the tetrahydrate are occupied by four water molecules and two axial sites by nitrate ions, oriented in monodentate fashion. The spectra suggest that in the dihydrate approximately octahedral coordination is maintained by having two nitrate ions oriented in bidentate fashion and two water molecules trans to each other on the remaining sites.