bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of density on the total ionization yields in X-irradiated argon, krypton, and xenon
Authors: Huang Sam S.-S. , Freeman Gordon R.
Published: May 2006

The amounts of ionization produced by absorption of X radiation in the liquids xenon, krypton, and argon are respectively 1.5, 1.4, and 1.2 times greater than those produced by the absorption of the same energy in the corresponding low density gases. The yields of free ions in the irradiated liquids were measured at applied electric fields 1–40 kV/cm and extrapolated to infinite field strength. The total number of ionizations per 100 eV absorbed was Gtot = 6.6 in xenon, 6.0 in krypton, and 4.5 in argon. The reason that the ionization yield is larger in the liquid than in the corresponding low density gas is partly that the energy gap Eg between the top of the valence band and the bottom of the conduction band in the liquid is smaller than the gas phase ionization potential IP. The ratio IP/Eg = 1.36 for xenon (Roberts and Wilson), 1.27 for krypton, and 1.17 for argon (from data of Jortner et al.). An extra source of ionization in the liquid might be reaction of the higher excited states, M* + M → [M2+ + e−].
The influence of nonelectronegative molecules on the mobility of excess electrons in liquefied rare gases and tetramethylsilane
Authors: Sowada Ulrich , Schmidt Werner F. , Bakale George
Published: May 2006

Addition of nonelectronegative molecules (n-alkanes, alkenes, CO, CO2) to liquid argon, krypton, and xenon influences the drift velocity of excess electrons in an electric field. At high field strengths (104–105 V cm−1), where the electrons have mean energies exceeding kT, inelastic collisions with solute molecules lead to an increase of the drift velocity above the value of the pure solvent. Analysis of this effect yields the energy dependent product of collision cross section and mean fractional energy loss per collision.At low field strengths a decrease of the low field mobility with increasing solute concentration is observed from which the cross section for momentum transfer could be deduced. The influence of solutes on the low field mobility was also found in tetramethylsilane.
Electrons in fluids: the role of disorder
Authors: Cohen Morrel H.
Published: May 2006

I review the present status of the theory of those aspects of the theory of disordered materials which are particularly relevant to the physics of electrons in fluids. First, however, I describe a general theory of the movement of slow electrons in fluids of arbitrary complexity in which the fluid is treated as a fluctuating medium. Coupling to the fluctuations is via a set of generalized deformation potentials. It is shown that this concept permits a way out of the impasse that has been reached in understanding the mobility of slow electrons in liquid argon via Lekner's theory. Assuming that molecular motion can be neglected on the electronic time scale permits taking over various relevant results from the theory of electrons in disordered solids, which is briefly reviewed. The effect of molecular motion is studied next. It is shown that strict localization does not occur and that the quasi-localized electrons diffuse with a characteristic correlation frequency depending on electron–molecule coupling and upon the characteristic frequencies of molecular motion as well as with a correlation length related to the localization length in static problems. Under easily reached conditions, this diffusion process is faster than that giving rise to the Stokes law mobility. Finally, a discussion is given of mobility transitions in which localization by disorder is distinguished from self-trapping.
An improved model of the localized electron in polar fluids
Authors: Kestner Neil R.
Published: May 2006

A new model for the long range electron solvent interaction experienced by a trapped electron in a polar fluid is presented. It is an extension and modification of the work of Iguchi except that it includes a cutoff beyond which the orienting ability of the trapped electron is not strong enough to overcome other forces between the polar molecules. This potential is of finite range and supports only one bound s and p state, in contrast to the usual polaron form.
A pulse radiolysis study of solvated electrons in dilute solutions of polar liquids in nonpolar solvents
Authors: Baxendale J. H.
Published: May 2006

Measurements of the conductivities following electron pulse irradiation of dilute solutions of ethanol, n-propanol, tert-butanol, or dimethyl sulphoxide in n-hexane, cyclohexane, or i-octane are quantitatively consistent with the existence of equilibria between electrons in the hydrocarbon and electrons solvated by dimers of the polar molecules. With dimethylformamide solutions in alkanes the equilibrium could be with the monomeric anion of the solute but this assignment is not unequivocal. Absorption spectra of es− in n-hexane solutions of ethanol and of tert-butanol have been obtained.
Optical study of electrons and positive ions in pulse-irradiated liquid 3-methyloctane at low temperatures
Authors: Gillis Hugh A. , Klassen Norman V. , Woods Robert J.
Published: May 2006

The spectrum of pulse-irradiated liquid 3-methyloctane at 127 K has maxima around 625 and 2100 nm. The latter is well-known as being due to the solvated electron (es−). The former is attributed to a positive ion because it is eliminated by the addition of triethylamine, but remains in solutions of electron scavengers, and is very similar to bands observed earlier by Louwrier and Hamill in glassy solutions at 77 K of higher hydrocarbons in CCl4 or CO2-bubbled 3-methylpentane. At temperatures of 127 K and less the initial decay rate of es− is greatly decreased by the addition of ∼6mol% triethylamine. The result is interpreted as indicating that at low temperatures the mobility of the initial hydrocarbon positive ion is much greater than that of either es− or the positive ion in triethylamine solutions, and therefore the initial hydrocarbon positive ion must be the parent radical cation which moves by resonance charge transfer. As the temperature of pure 3-methyloctane is raised from 103 to 153 K, the initial Gε650 decreases by about 30% while initial Gε2100 almost doubles; because of these and other observations it is tentatively suggested that a second solvated electron is also produced.
The yield and extinction coefficient of the solvated electron in methanol: pulse radiolysis of nitrobenzene and tetranitromethane solutions
Authors: Johnson David W. , Salmon G. Arthur
Published: May 2006

The radical anion [Formula: see text] NB−, which has a strong absorption spectrum from 250–500 nm, is formed by reaction of nitrobenzene with solvated electrons, es−, and hydroxymethyl radical anions, •CO2O−, with k1 = (1.92 ± 0.35) × 1010 M−1 s−1 and k2 = (1.03 ± 0.02) × 1010 M−1 s−1.[Formula: see text]Gελ is constant for NB− over a wide range of nitrobenzene concentrations in basic solution. By assuming that the yields of scavengeable radicals are the same in neutral and basic solutions we obtain ε(NB−)300 nm = (1.66 ± 0.02) × 104 M−1 cm−1. This value is used to evaluate the yield of es− scavengeable by dilute solutions of solutes as G(es−)esc = 1.20 ± 0.03. Extinction coefficients of es−, hydroxymethyl radicals, •CH2OH, and •CO2O− and the oscillator strength of the es− absorption are calculated.The yields of es− determined by previous workers are discussed in terms of dry, damp, geminate, free, spur, and escaped electrons. A model is constructed in terms of damp, spur, and escaped electrons which compares favourably with experimental scavenging results and direct measurements by optical pulse radiolysis.
Low energy electron ranges in liquids: determination by nonhomogeneous kinetics
Authors: Dodelet J.-P.
Published: May 2006

Free ion yields have been measured in four hydrocarbon liquids: n-pentane, cyclopentane, neopentane, and neohexane. Each liquid has been studied from room temperature or below up to the critical temperature. Theoretical curves have been calculated using the relation between the free ion yields and the external field strength derived by Terlecki and Fiutak on the basis of an equation by Onsager. Two popular electron range distribution functions, Gaussian and exponential, have been shown not to be an adequate representation of the reality as far as the model used for the calculations is concerned. In order to fit experimental points, both range distribution functions would require a drastic increase in the total ionization yield, Gtot, with temperature increase. This would mean an unrealistic decrease of the ionization potential of the molecule from the melting point up to the critical temperature.It is possible to keep Gtot quite constant and within the range of values obtained by other techniques by extending the Gaussian range distribution function with a (range)−3 probability tail. The most probable range can be normalized for the liquid density. This parameter has been used to obtain information about the behaviour of epithermal electrons in the four alkane liquids from the melting point up to the critical temperature.(1) Normalized penetration ranges of epithermal electrons are dependent on the structure of the molecule in the entire liquid range but differences are smaller at critical than at low temperatures.(2) Normalized penetration ranges of epithermal electrons pass through a maximum in the liquid phase for neopentane, neohexane, and cyclopentane. No maximum is observed for n-pentane.(3) There is no drastic change in the behaviour of epithermal electrons in these alkanes at the critical temperature.
Electron scavenging in the radiolysis of supercritical butenes
Authors: Nishikawa Masaru , Yamaguchi Yoh-Ichi
Published: May 2006

Electron scavenging reactions with N2O have been studied in γ-irradiated supercritical butènes in the density range 0.25–0.48 g/cm3 at 170 ± 1 °C. Free ion yields were estimated as a function of density from the nitrogen yields by means of the 'square root' model. The estimated Gfi in butenes increased with the decrease in density, and were in the order [Formula: see text]cis-2-buteneisobutene > trans-2-butene at a given density. The density-normalized range of electrons estimated from Gfi values was independent of density over the density range studied. The magnitude of the reactivity parameter A in trans-2-butene was much larger than that in other butenes studied, but it generally increased with a decrease in density. An analysis of the parameter on the basis of the Nernst–Einstein relationship indicates that the trend is related to the change in the encounter efficiency of the reaction e− + N2O.
Effect of a magnetic field on the fluorescence produced in irradiated anthracene solutions
Authors: Dixon R. S. , Sargent F. P. , Lopata V. J. , Gardy E. M. , Brocklehurst B.
Published: May 2006

The effect of an applied magnetic field on the fluorescence from radiolytic ion recombination has been studied for anthracene in some hydrocarbon solvents. In pulse-irradiated anthracene (10−2 mol dm−3) in squalane, the fluorescence intensity following the pulse increases as a function of applied magnetic field in the range studied, 0 to 0.3 T (0 to 3000 G). At a constant magnetic field strength, the field-induced enhancement of the fluorescence intensity varies with time after the pulse. At high field strengths (0.3 T) the enhancement reaches a maximum of ∼45% about 50 ns after the pulse. Similar effects are observed in cyclohexane but the enhancement is smaller than that in squalane. In benzene solutions the effect is extremely small. These findings are confirmed by observations in continuously gamma-irradiated solutions. In gamma-irradiated solutions of anthracene (10−2 mol dm−3) in squalane, the fluorescence intensity increases with increasing magnetic field and approaches ∼13% enhancement at high fields (>0.1 T). The enhancement is smaller (∼3%) in cyclohexane and very small (<1%) in benzene solutions. 9,10-Dimethylanthracene gives a larger enhancement and anthracene-d10 a smaller enhancement than the parent anthracene at high fields. The results are in general agreement with recent theoretical predictions based on the effect of a magnetic field on the loss of spin correlation of geminate ions pairs prior to recombination.
Chemical potentials and fluctuations in indium–iodine solutions
Authors: Ichikawa Kazuhiko
Published: May 2006

The composition dependence of the relative chemical potential of In in liquid In–I alloys was determined from emf data obtained over the range of composition from In to InI3. Electrical conductivities were also measured for a limited number of concentrations. The specific conductance of the InI3 composition differs from that of pure liquid In by almost five orders of magnitude; i.e., at 600 °C that for InI3 is 0.104 while that for the pure metal is 2.16 × 104 Ω−1cm−1. At the long-wavelength limit the concentration correlation function Scc(0), which was calculated from the chemical potential data, exhibits large composition fluctuations on the In-rich side and minimal compositional disorders in the vicinity of the intermediate compositions InI, InI2, and InI3. The mean square compositional fluctuation is developed to discuss the crude short range ordering, ΔNα and the role of charge transfer, Δeα, in a general statistical mechanical theory of solutions. The large peak in Scc(0) at the indium-rich side provides crucial evidence of large concentration fluctuations, accompanied by microscopic inhomogeneities in the electronic structure, if a bimodal distribution is assumed. The limit ΔNα → 1 near the InI, InI2, and InI3 compositions shows that a preference exists for unlike nearest neighbors because of the ionic or covalent character in the chemical bonding. It is proposed that over the In-InI range there is the relationship between a gradual metal–nonmetal transition and the large concentration fluctuations which are associated with microscopic inhomogeneities in the electronic structure.
Equilibrium model for the interpretation of the conduction properties of metal–ammonia solutions
Authors: Hahne S. , Krebs P. , Schindewolf U.
Published: May 2006

The electrical conductivity of metal–ammonia solutions can be described by an equilibrium of solvated electrons of low mobility and of free electrons of high mobility. With proper choice of the equilibrium constant and its temperature and pressure dependence and of the solvation number of the solvated species the experimental conductivities can be matched in the temperature and pressure range from 240 to 420 K and up to 1000 bar over the entire concentration range from 0.1 mol/ℓ to saturation, also fitting the extrema of the temperature and pressure coefficients of the conductivity around 1 mol/ℓ.
The study of primary and secondary charge carriers in nanosecond pulse irradiated liquid dielectrics using a resonant microwave cavity
Authors: Warman John M. , Infelta Pierre P. , De Haas Matthijs P. , Hummel Andries
Published: May 2006

A microwave resonant cavity technique for studying changes in conductivity of pulse irradiated dielectric liquids is presented. The sensitivity of the method is such that transient changes in conductivity of 5 × 10−9 ohm cm−1 can be measured with a signal to noise ratio of 10 and a response time of approximately 10 ns. The use of the technique is illustrated by a study of primary (excess electron, hole) and secondary (molecular ions derived from solutes) charge carriers in the saturated hydrocarbon liquid trans-decalin. The temperature dependences of the mobilities of the excess electron and hole are found to be described quite well by μ(−) = 25 exp(−4500/RT) cm2 V−1 s−1 and μ(+) = 4.0 × 10−3 exp (500/RT). The mobility of the hole is found to exceed that of the electron below approximately 10 °C. The sum of the mobilities of the secondary ions at 22 °C in a 5 × 10−3 M SF6 plus 10−2 M benzene solution is 5.2 × 10−4 cm2 V−1 s−1. In order to determine the mobilities of even the primary charge carriers consideration had to be given to the presence of geminate ion pairs on the time scale of the observations. The way in which corrections for geminate ion pairs were carried out is fully discussed.
Etude expérimentale et théorique des spectres de vibration des dérivés di- et trisubstitués de l'isothiazole
Authors: Mille Gilbert , Guiliano Michel , Chouteau Jacques
Published: May 2006

The infrared absorption spectra in different physical states (liquid, solution, vapor) and the Raman spectra in the liquid or solid state of di- and trisubstituted isothiazole derivatives have been analyzed. For some compounds a study of the normal vibrations has also been done. An assignment of the fundamental modes of vibration of these molecules is given and discussed.
Degrees of order of solubilized alkanes, alcohols, carboxylates, and carboxylic acids in oriented lyomesophases
Authors: Chen Douglas M. , Fujiwara Fred Y. , Reeves Leonard W.
Published: May 2006

The degree of order of solubilized molecules and ions in oriented lyomesophases has been determined at specifically deuterated C—D bond axes from the quadrupole splitting of the deuterium magnetic resonance. Mixtures at low concentration of specifically deuterated alkanes, alcohols, carboxylic acids, and carboxylates of different chain length have been observed in host cationic and anionic lyomesophases. The degree of order of a given C—D position in alcohols increases strongly with chain length up to a length comparable with the host detergent. A broad series of carboxylic acids and carboxylate ions from C2 to C16 have been deuterated in the α position. The α-C—D bond axis in the solubilisate increases in order with chain length, the anion having lower order than the parent acid. An accurately linear increase in the degree of order of the α position is observed for intermediate chain lengths. At chain lengths approximately equal to the host chain lengths the α position reaches a limiting value in the degree of order and further segments do not influence the order. At short chain lengths the degree of order is less than that predicted from extrapolation of order in the linear region. This has been interpreted in terms of distribution into the aqueous compartment by the solubilisates of short chain length. Acetic acid and the acetate, propionate, butanoate, and pentanoate ions spend an appreciable amount of time in the aqueous region. An estimate has been made of these distributions based on reasonable assumptions.
Metal complex catalyzed reactions of anils. II. Transimination
Authors: Boate A. R. , Eaton D. R.
Published: May 2006

The exchange of aromatic residues between anilines and anils (transimination) has been shown to be efficiently catalyzed by metal complexes of thiourea. This reaction can be conveniently studied by nmr spin saturation transfer techniques. Experiments of this type using both CW and FT nmr spectrometers are reported. The rate of the reaction is about two orders of magnitude greater than the rates of reactions involving anil formation and hydrolysis with the same substrates and catalysts. The effectiveness of the catalysts vary in the same manner as they do for anil formation and the reaction is similarly subject to inhibition by competing ligands. The rate of exchange of the two inequivalent methyl groups in acetone anils is similarly catalyzed and may be studied by spin saturation transfer experiments. The lifetime of an anil molecule for methyl group exchange is approximately twice that for transimination suggesting that the rate determining process for transimination results in free rotation about the C—N bond so that the methyl groups have an equal probability of retaining or exchanging their environments.
Folded forms in tetrapeptides. Z-Val (Ala)3-OEt
Authors: Tamburro Antonio Mario , Scatturin Angelo
Published: May 2006

The circular dichroism spectra of Z-Val-(Ala)3-OEt in different solvents are reported. In dioxane the spectrum shows a negative band at 228–229 nm and a positive band at 212–213 nm, features which are consistent with the presence of some population of tetrapeptide molecules in a β-bend conformation. The infrared spectrum of Z-Val-(Ala)3-OEt in KBr suggests an association of the molecules in an antiparallel β-structure in the solid state.
N,N-Ethylenebis(salicylideneimine) derivatives of gallium trimethyl: crystal and molecular structure of N,N-ethylenebis(salicylideneiminato) bis(dimethylgallium)
Authors: Chong Kenneth S. , Rettig Steven J. , Storr Alan , Trotter James
Published: May 2006

Crystals of N,N-ethylenebis(salicylideneiminato)bis(dimethylgallium) are orthorhombic, a = 22.781(1), b = 9.4869(6), c = 19.700(2) Å, Z = 8, space group Pbca. The structure was solved by direct methods and was refined by full-matrix least-squares procedures to a final R of 0.036 and Rw of 0.029 for 2248 reflections with I ≥ 3σ(I). Details of the preparation and physical properties of (C16H14N2O2)(GaMe2)2 and (C16H15N2O2)(GaMe2) are given. The (C16H14N2O2)(GaMe2)2 molecule is approximately centrosymmetric in the solid state. A "GaMe2" unit is coordinated to each of the two salicylideneiminato moieties of the N,N-ethylenebis(salicylideneiminato) ligand. The gallium atoms have a distorted tetrahedral coordination geometry, with bond angles at gallium ranging from 92.7(1) to 124.6(3)°. Important bond lengths (corrected for libration) are: Ga—O, 1.886(2) and 1.884(2), Ga—N, 2.033(3) and 2.042(3), and weighted mean Ga—C, 1.959(9) Å.
The synthesis and thermal decomposition of bis(phenylthio)methyl derivatives of mercury
Authors: Chivers Tristram , Ram Ritchwick
Published: May 2006

The mercurials, [(PhS)2CH]2Hg and PhHgCH(SPh)2, have been prepared from (PhS)2CHLi and HgBr2 or PhHgCl, respectively. The unsymmetrical compound decomposes readily both in the solid state and in various solvents. The symmetrical compound is more stable but also undergoes decomposition in certain refluxing solvents. The identity of the products suggests that the major decomposition route involves homolytic fission of the Hg—CH(SPh)2 bond and that PhS migration to mercury plays only a minor role.
Vibrational spectra and normal coordinate analysis of crystallinelithium metasilicate
Authors: Devarajan V. , Shurvell H. F.
Published: May 2006

Infrared and Raman spectra of polycrystalline lithium metasilicate have been recorded. A vibrational assignment in terms of the various symmetry species of the unit cell group, C2v, has been made. A normal coordinate analysis of the unit cell vibrations at the centre of the Brillouin zone (k = 0) was carried out to support the assignment and provide descriptions of the vibrational modes. The results are discussed in the light of previous normal coordinate calculations on the isolated metasilicate chain.
Ring currents, local anisotropy, and the problem of the out-of-plane protons: a reinvestigation of the nuclear magnetic resonance spectrum of [10]-paracyclophane
Authors: Agarwal Arvind , Barnes John A. , Fletcher John L. , McGlinchey Michael J. , Sayer Brian G.
Published: May 2006

The1H nmr spectrum of [10]-paracyclophane has been recorded at 220 MHz and the methylene protons assigned on the basis of homonuclear decoupled spectra. Local anisotropic contributions to chemical shifts for protons sited above or near the aromatic ring of [10]-paracyclophane have been calculated using a classical model previously proposed by Grant. The residual incremental shift was shown to follow the Waugh–Fessenden–Johnson–Bovey classical ring current model, but the loop separation originally invoked was shown to be unnecessary. These corrected ring current contributions also correlate very well with the quantum-mechanical approach of Haigh and Mallion.
Study of NH4EuF4 in solid state reaction Eu2O3–NH4F. Thermal analyses, calorimetry, and decomposition kinetics
Authors: Rajeshwar Krishnan , Secco Etalo A.
Published: May 2006

The solid state reaction Eu2O3–NH4F leading to the formation of NH4EuF4 was studied by thermal analyses and X-ray diffraction.The heat of decomposition of NH4EuF4 and the kinetics of thermal decomposition of NH4EuF4 are reported.
Nuclear analogs of β-lactam antibiotics. III. Synthesis of 1,3-dimethyl-Δ3-O-2-isocephems
Authors: Doyle Terrence William , Luh Bing-Yu , Martel Alain
Published: May 2006

The synthesis of 1-α-methyl and 1-β-methyl isomers of 7-(3-phenoxyacetamido-1,3-dimethyl-Δ3-O-2-isocephem-4-carboxylic acids (14a and 14b) is described. Treatment of amine 2 with methacrolein followed by cycloaddition gave 4 which was ozonolyzed to yield the methyl ketones 6. Upon reduction of 6 there was obtained a mixture of isomeric alcohols 8 which were resolved by column chromatography, converted to their mesylates 9, and hydrolyzed to yield 10a and 10b. Conversion of each isomer to the corresponding O-2-isocephems 11a and 11b followed by azide reduction, coupling of the amines to phenoxyacetic acid, and removal of the ester blocking groups gave 14a and 14b. An attempt to prepare the gem-dimethyl compound failed. The structural assignments to 14a and 14b are discussed.
Nuclear analogs of β-lactam antibiotics. VII. Synthesis of 2-isocephems
Authors: Doyle Terrence William , Douglas James Leslie , Belleau Bernard , Meunier Jacques , Luh Bing-Yu
Published: May 2006

The synthesis of 7-β-phenoxyacetamido-3-methyl-Δ3-2-isocephem-4-carboxylic acid 14b and its corresponding α-sulfoxide 15 and sulfone 17 is described. Treatment of the bismesylates 4a, 4b, and 10 with hydrogen sulfide triethylamine gave the corresponding 7-β-amino-Δ3-2-isocephems 12a–c which were coupled with phenoxyacetic acid to yield the amides 13a–c. Hydrogenolysis of 13b and c gave the acids 14a–b which were active as antibiotics. Compound 14b was oxidized to its sulfoxide 15 with sodium metaperiodate and to its sulfone 17 with m-chloroperbenzoic acid. Conversion of 13c to its sulfoxide 16b followed by halogenation gave the 1α-chloro sulfoxide 18 which was converted to the acid 19. The stereochemical assignments in the 2-isocephem series are discussed.
Pyrromethenes in the synthesis of polypyrranes
Authors: Rowold Arend , MacDonald S. Ferguson
Published: May 2006

A new method makes appropriate 5-bromo-5′-methoxymethyl-pyrromethenes available for synthesizing polypyrranes related to uroporphinogens. In chloroform at 20 °C, they react with α-free pyrroles (normally) and with 5-free pyrromethanes (losing the methoxymethyl-pyrrole ring) to give tripyrrenes which reduce to unblocked tripyrranes. Likewise, but in dioxane at 20 °C and more cleanly, 5-bromo-5′-methylpyrromethenes convert pyrromethanes to tripyrrenes, and a tripyrrane to a tetrapyrrene (bilene).
Liquid-junction potentials in ethylenediamine: Attempted calculations and evaluations using concentration cells
Authors: Makhija Suraj P.
Published: May 2006

Concentration cells of the type M(Hg)|MX(1)||MX(2)|M(Hg), where M(Hg) is potassium amalgam or sodium amalgam, were investigated with three electrolytes, potassium bromide, potassium iodide, and sodium iodide. An attempt was made to determine the necessity and magnitude of liquid-junction potential corrections. Only in the case of sodium iodide are the ionic mobilities of cation and anion quite different in ethylenediamine, and liquid-junction potential corrections are necessary to obtain agreement between observed and calculated data. The limiting equations of Nernst and of Lewis and Sargent were found to be appropriate for calculating liquid-junction potentials in ethylenediamine, provided that calculated activities were used in these equations.
Acid-catalysed hydrolysis of bis(trifluoroethyl)sulfite in water and 60.7% p-dioxane in water
Authors: Salomon Mark
Published: May 2006

The rates of the catalysed hydrolysis of bis(trifluoroethyl)sulfite have been measured in concentrated acid solutions at 25 and 35 °C in water and in an aqueous mixture containing 60.7% p-dioxane by weight. The results are analyzed in terms of a solvation model similar to that proposed by Bunnett, and the kinetic medium effect. The data indicate that the mechanism of the acid-catalysed hydrolysis is bimolecular and that catalysis by halide ions occurs only in acidified solutions.
Molar excess enthalpies of acetonitrile + chloroform and of acetonitrile + chloroform-d1 at 298 K
Authors: Handa Yash Paul , Jones David Edward
Published: May 2006

Molar excess enthalpies of acetonitrile + chloroform and of acetonitrile + chloroform-d1 were measured at 298 K. The results for the former system were discussed in terms of an ideal associated solution model and the deuterium isotope effect was discussed.
Lifetimes of the solvated electron in liquid alcohols
Authors: Freeman Gordon R.
Published: May 2006

A reply is given to the preceding Comment concerning the kinetics of the decay of es− in alcohols.
Crystal structure studies of Group V chalcogenide compounds. I. The structure of tricyclohexylphosphine sulphide
Authors: Kerr K. Ann , Boorman P. M. , Misener B. S. , Roode J. G. H. van
Published: May 2006

Crystals of tricyclohexylphosphine sulphide, C18H33PS, are orthorhombic, a = 10.906(2), b = 15.836(2), c = 10.362(2) Å, Z = 4, space group Pn21a. The structure was solved by direct methods and refined by full-matrix least-squares procedures to a final Rω of 0.058 for all 1209 reflexions with sin θ/λ ≤ 0.5377.Although second harmonic generation unambiguously established the correct space group as Pn21a, parameters reported here refer to the centrosymmetric space group Pnma. The geometry at phosphorus is approximately tetrahedral with an average P—C distance of 1.838(2) Å. Angles at phosphorus range from 105.4° to 113.2°. The P=S bond length of 1.966(2) Å is one of the longest bonds of this type so far reported. Rigid body analysis of thermal parameters suggests that the 'true' bond lengths are even longer.
Syntheses in the group of Nuphar alkaloids. IV. Crystal structure and stereochemistry of synthetic (±)-3-epinupharamine
Authors: Sabat Mlchał , Głowiak Tadeusz , Szychowski Jerzy , Wrôbel Jerzy T. , Leniewski Andrzej
Published: May 2006

Racemic 3-epinupharamine hydrobromide (C15H26BrNO2) crystals are monoclinic, space group C2/c, with a = 18.163(3), b = 13.346(2), c = 13.847(2) Å, β = 100.36(1)°, Z = 8. The X-ray analysis proved the structural identity of the compound obtained by the total synthesis with the natural 3-epinupharamine. The empirical criterion indicating the axial or equatorial orientation of the C-methyl group on the basis of the direction of changes of the chemical shifts recorded in benzene solutions does not hold for the piperidine system investigated.Les cristaux du bromhydrate d'épi-3 nupharamine racémique (C15H26BrNO2) sont monocliniques, groupe d'espace C2/c avec a = 18.163(3), b = 13.346(2), c = 13.847(2) Å, β = 100.36(1)°, Z = 8. L'analyse par rayons-X a démontré l'identité structurale du composé obtenu par synthèse totale avec l'épi-3 nupharamine naturel. Les critères empiriques permettant de déterminer l'orientation axiale ou équatoriale des groupes C-méthyles en se basant sur la direction des changements dans les déplacements chimiques enregistrés en solutions benzéniques ne peuvent être utilisés dans le système pipéridine étudié. [Traduit par le journal]
Réaction oscillante de Belousov. 2. Etude d'un nouveau modèle cinétique
Authors: Schmitz Guy
Published: May 2006

On the basis of our results dealing with the bromate-cerous reaction we propose and discuss a new kinetic model for the Belousov–Zhabotinskii oscillating reaction. The existence of a limiting cycle is shown with an analog computer for a set of semi-empirically chosen kinetic parameters.
A comparison of mechanisms for the oxidation of cerium(III) by acidic bromate
Authors: Noyes Richard M. , Bar-Eli K.
Published: May 2006

The preceding paper by Schmitz suggests a mechanism of the oscillating Belousov–Zhabotinsky reaction that differs significantly from the mechanism previously proposed by Field, Körös, and Noyes. The most important differences are associated with the mechanism assumed for the oxidation of cerium(III) by bromate. The alternative mechanisms for this oxidation are examined and compared with relevant experimental information on similar systems. We conclude the mechanism developed by Schmitz and associates is inconsistent with several observations and that it is doubtful it can be the correct interpretation of this reaction.
13C chemical shifts in medium ring and macrocyclic ketolactones
Authors: Mahajan Jaswant R. , Araújo Hugo C.
Published: May 2006

Natural abundance 13C Ft nmr spectra of four different series of title compounds have been examined. Unambiguous chemical shift assignments could be made for all the carbons of the 11-membered cis-3,3-dimethyl-5-keto-6-alkyl-8-decenolides. In the rest of the 9- to 16-membered ketolactones, unique as well as logical assignments have been made using the standard 13C chemical shift rules. In the case of two benzo- and naphthoketolactone series examined, the available shielding parameters for the substituted benzenes were employed with success to the naphthalene series for the assignment of aromatic carbons.
Photochemistry of oxalate esters as a route to free radicals. Decay routes of crowded free radicals
Authors: Içli Siddik , Nowlan Vincent J. , Rahimi Parviz M. , Thankachan Chacko , Tidwell Thomas T.
Published: May 2006

Photolysis of suitable oxalate esters leads to alkyl radicals which in the case of di- and tri-tert-butylmethyl abstract hydrogen and for triisopropylmethyl-d18 gives an esr spectrum consistent with the 'cogwheel' conformation for this species.
A detailed assignment of the O–H stretching bands of ice I
Authors: Whalley E.
Published: May 2006

A detailed assignment of the infrared and Raman O–H stretching bands of disordered ice Ih and Ic is proposed. It is based on the assumptions that the spectra of disordered ice Ic are closely related to those of ordered ice Ic, and that the spectra of the as yet unrealized ordered ice Ic can be predicted from the spectra of ice VIII. The supposed similarity between the spectra of ordered and disordered ice Ic is justified by the observed similarity of the spectra of ice VIII and VII, which are respectively ordered and disordered forms of the same structure and are closely related to ordered and disordered ice Ic. The assignment takes into account the intermolecular coupling, which is particularly strong for the ν1 vibrations but weak for the v3, and the TO–LO splitting, particularly of the v3 vibrations, which is shown to be required by the high infrared intensity. The infrared and Raman bands of amorphous ice have been assigned by analogy with the assignments of ice I.
Ligand substitution kinetics of nickel(II) ion in N,N-dimethylformamide
Authors: Chattopadhyay Praphulla Kumar , Kratochvil Byron
Published: May 2006

Rate constants and activation parameters for formation of the monocomplexes of Ni(II) ion with several mono-, bi-, and terdentate ligands in N,N-dimethylformamide were obtained by stopped-flow spectrophotometry. The gross features of substitution for all the ligands studied could be accommodated within the structure of an Id-type mechanism. 4-Phenylpyridine behaves most 'normally', and 1,10-phenanthroline stabilized most strongly outer-sphere complex formation with Ni(II). Comparison of these data with previously reported work by other authors for substitution at Ni(II) in acetonitrile with the same ligands indicates that in dimethyl-formamide pyridine-type ligands generally affect the stability of metal–ligand outer-sphere complexes less dramatically than in acetonitrile. Hammett correlation is observed for 1,10-phenanthroline and its 5- and 5,6-substituted derivatives. The slope of the Hammett correlation plot in dimethylformamide is in the order of −0.2, about half the value of −0.4 reported previously in acetonitrile by other authors. This indicates that the stability of the metal–ligand outer-sphere complex is affected more greatly by small differences in the electronic nature of the coordinating substituted 1,10-phenanthrolines in acetonitrile than it is in dimethylformamide.
Studies of a model of hydrogen recombination
Authors: Snider Neil S.
Published: May 2006

A Morse oscillator model for recombination of hydrogen and its isotopes was investigated computationally. The model is very similar to one recently studied by Pritchard and co-workers. The aims of the study were the test of certain approximations and the determination of the range of validity of the model. It was found that at low temperatures the steady state approximation is an increasingly accurate and increasingly convenient approximation. A way of estimating the error arising from this approximation was proposed. Other approximations which were tested gave unsatisfactory results. The rate constant vs. temperature curve for the model does not agree well with the experimental curve for hydrogen in argon except insofar as it reproduces the observed levelling-off at high temperatures. For the model this result may be ascribed to increasing relative rates for multiquantum transitions among the levels of the diatom. The model does give the experimentally observed ratios of the rate constants for H- and D-atom recombination. This result indicates that the important factor in determining the isotope ratio is the effect of mass change on the density of states rather than its effect on the collision dynamics.
Photolyse du trans-butène-2 vers 7.1 eV
Authors: Wiçckowski Andrzej , Collin Guy J.
Published: May 2006

The photolysis of trans-2-butene (tB-2) was studied at 7.10–7.11 eV (174.5–174.3 nm) in a static system using a nitrogen lamp. The main primary photochemical processes are the C—C split leading to the formation of CH3 and CH3CHCH radicals, the primary quantum yield, Ф = 0.33 and the molecular or/and atomic hydrogen elimination, Ф = 0.27 with concurrent formation of 1,3-butadiene. The excited CH3CHCH radicals isomerize, followed by aliene formation, or are stabilized by collisions. The stabilization of the photoexcited tB-2 molecules is an inefficient process in the pressure region studied (10–20 000 N m−2). Only small isomerization of tB-2 was observed below 133 N m−2[Formula: see text]
A comparison of substituent effects on vicinal proton–proton and carbon–proton coupling constants
Authors: Forrest T. P. , Sukumar S.
Published: May 2006

Vicinal carbon–proton coupling constants have been determined for a series of tert-butyl derivatives and compared to the vicinal proton–proton coupling constants in the analogous series of isopropyl derivatives. In both series coupling constants were found to decrease with electronegativity of substituent, with 3JC,H decreasing more rapidly than 3JH,H. The relationship between the two types of coupling was found to be JC,H = 1.2JH,H − 3.5. The regular change in the ratio of JC,H to JH,H indicates that substituent effects can be useful in predicting carbon–proton coupling constants from proton–proton models.
Spectra of the 1:1 and 3:1 solid complexes of coronene-TCNQ
Authors: Truong Kim Doan , Bandrauk André D.
Published: May 2006

Two new solid TCNQ complexes have been isolated, coronene–TCNQ 1:1 and 3:1. The infrared and electronic absorption spectra are presented for the two different stoichiometries. From these spectra we infer that the complexes are covalent in the ground state with a charge transfer band appearing at 730 nm. The out of plane vibrations of the individual molecules are noticeably perturbed upon complexation.
Open-chain nitrogen compounds. Part III. The formation of triazenes in the reaction of diazonium salts with α-aminoacetonitrile and related α-substituted alky lamines
Authors: Daniels Theresa A. , Sidi Shiraz , Vaughan Keith
Published: May 2006

Several triazenes of type Ar•N==N•NH•CH2Y, where Y is electron withdrawing, have been prepared by reaction of the diazonium salts X•C6H4N2+ (X = H, p-NO2, p-CO2Me, p-COPh, and o-COPh) with the α-substituted alkylamines NH2CH2Y (Y = CN, CO2Et, COPh, and CH(OCH3)2) in aqueous solution, without prior isolation of the diazonium salt. In all cases, the diazonium ion attacks at the NH2 moiety exclusively and the methylene group in NH2CH2Y shows no tendency to compete for the diazonium ion.
Migration of hydroxyl in secondary systems during solvolysis in acid solution
Authors: Cathcart Robert C. , Bovenkamp John W. , Moir Robert Y. , Bannard Robert A. B. , Casselman Alfred A.
Published: May 2006

A system of compounds has been prepared which is well adapted for displaying the role of trans vicinal, secondary hydroxyl in solvolysis. On methanolysis in acid solution, compounds 5, 7a, and 8a all gave the same products, 9a and 10a, and in practically the same proportions, suggesting that at least one intermediate was common to all three reactions. These intermediates were such that 7a and 8a were not interconverted during the solvolysis, a fact in support of 6 as a common intermediate. Several alternative explanations were shown to be untenable, largely by taking advantage of the remarkable differences between hydroxyl and methoxyl. The work provides the most decisive evidence available for the covalent participation of hydroxyl as a neighbor group in the solvolysis of secondary systems, and contributes also to the study of the reverse reaction, the acid-catalyzed scission of epoxides.
Reductive acylation of the aliphatic diazo function. N-(2-Diazo-3-oxoalkanoyl)-glycine esters as synthetic precursors of [γ-(aryloxy)threonyl]glycine derivatives
Authors: Looker James H. , Carpenter James W. , Peet Norton P.
Published: May 2006

Catalytic reduction of several N[2-diazo-3-oxo-4-(aryloxy)alkanoyl]glycine esters gives N-[2-hydrazono-3-oxo-4-(aryloxy)alkanoyl]glycine esters. A pyrazine is obtained by catalytic reduction in ethanolic hydrogen chloride of N-[2-diazo-3-oxo-4-(phenoxy)butanoyl]glycine ethyl ester. A two-step procedure involving reductive acetylation or trifluoroacétylation of the diazo function, and subsequent borohydride reduction of the keto group yields the corresponding acylamino alcohol derivatives.
Reactions of bishalomethylarenes with superoxide
Authors: Dao L. H. , Hopkinson A. C. , Lee-Ruff E. , Rigaudy J.
Published: May 2006

1,2-Dioxenes 2, 7, and 14 are obtained from the reactions of potassium superoxide with 1,2-bishalomethylarenes. Rearrangement products are also formed in competition with the cyclization reaction. The relative yields of dioxenaes depend on the relative concentration of superoxide to substrate as well as reaction conditions. Mechanisms for the formation of the rearrangement products are proposed.
Simultaneous diffusion and chemical activation control of the kinetics of the binding of carbon monoxide to ferroprotoporphyrin IX in glycerol–water mixtures of high viscosity
Authors: Hasinoff Brian B.
Published: May 2006

The kinetics of the reaction of ferroprotoporphyrin IX with CO have been studied in mixed glycerol–water solvents of high viscosity in order that the simultaneous influence of chemical activation and diffusion control of the reaction might be observed. Analyses of curved Arrhenius plots indicated that in the low temperature high viscosity limits the reaction is largely diffusion controlled. The deviation of the second order diffusion rate constants, from that predicted by simple theory for reaction between uniformly reactive spheres of equal radii, is a factor of 0.3 to 0.9, depending upon the solvent composition. A couple of other models for diffusion controlled reaction, ascribing these deviations to changes of steric requirements, were also examined.
Analyse de quelques processus photophysiques chez les dérivés diphénylés en position 4 du γ-pyranne et du γ-thiopyranne
Authors: Lord Gabriel , Foisy Luc , Baril Lucie , Gravel Denis , Durocher Gilles
Published: May 2006

The photophysical processes along with the photolysis of 4,4-diphenyl-γ-pyran (1) and 4,4-diphenyl-γ-thiopyran (2) are discussed in this paper. The solvent effect, the temperature effect, and the photolytic source intensity dependence of the yield of the secondary photoproduct are all among the experimental parameters investigated. It is shown that the first singlet–singlet electronic transition in molecules 1 and 2 is ππ*. in nature. The divinyl ether and divinyl thioether chromophore play a role in this transition and also directly contribute to the radiationless deactivation of the first excited singlet states of these molecules. On the other hand the energy of the first triplet ππ* state seems to be more localized in the phenyl groups of the molecules 1 and 2.It is also shown that the photolysis of molecule 1 occurs by a monomolecular mechanism to produce a photoaldehyde which is also photolysed under prolonged irradiation. This aldehyde has also been shown to be a secondary photoproduct in the photoreaction sequence of 4,4-diphenyl-γ-pyran.
Stereospecific syntheses of the α-patchoulene and α-cedrene skeletons from a common intermediate
Authors: Deslongchamps Pierre , Lafontaine Jacques , Ruest Luc , Soucy Pierre
Published: May 2006

The synthesis of the cyclopropane diketone 3 and its specific conversion into the tricyclic enedione 4 (cedrene skeleton) under kinetic control and into the tricyclic enedione 5 (patchoulene skeleton) under thermodynamic control is reported.
The chemistry of anions derived from tetracyanodiphenoquinodimethane (TCNDQ)
Authors: Addison A. W. , Dalal Nar S. , Hoyano Yumiko , Huizinga Sytze , Weiler Larry
Published: May 2006

Dihydro-TCNDQ was prepared from biphenyl. The dianion salts of TCNDQ with alkali metal and tetraalkylammonium counter ions were prepared and characterized by their nmr and uv-visible spectra. Solutions of these dianions undergo two one-electron oxidations at −0.31 and −0.15 V in DMF. The electrochemistry is complicated by a second chemical process involving the monoanion [Formula: see text]. This was postulated to involve a dimerization of [Formula: see text] and this process was also implicated in the analysis of the uv-visible spectra of this anion. The [Formula: see text] anion has a solution esr spectrum of over 25 lines which have been analyzed by a computer simulation of the spectrum.
Nuphar thiaspirane sulfoxides. 13C nuclear magnetic resonance determined configuration and utilization in the interconversion of thiaspirane stereochemical types
Authors: LaLonde R. T. , Wong C. F.
Published: May 2006

The configuration of the sulfoxide oxygen in syn- and anti-thiobinupharidine sulfoxide was determined by employing the 13C nmr sulfoxidation increments of C-6. Establishment of the 13C nmr line assignments for C-6 included the study of the C-6 and C-6′ deuterated thiobinupharidine and the corresponding sulfoxides. Thermolysis of syn-thiobinupharidine sulfoxide in DMSO and subsequent reduction with sodium borodeuteride in methanol yielded thiobinupharidine, labelled with deuterium only at C-6, and thionuphlutine B, labelled with deuterium at both C-6 and C-6′. Treatment of the anti sulfoxide in xylene or DMSO resulted in no thiobinupharidine or thionuphlutine B. Similarly, syn-neothiobinupharidine sulfoxide gave neothiobinupharidine and a new thiaspirane, thionuphlutine C. These two compounds were not produced from anti-neothiobinupharidine sulfoxide heated in xylene.
Stereochemically controlled syntheses of some bicyclo[n.3.0]alkane-1-carboxylic acids
Authors: Warnhoff E. W. , Tai W. T. , Toong Y. C.
Published: May 2006

Stereospecific methods of synthesis of some cis- and trans-bicyclo[n.3.0]alkane-1-carboxylic acids are described, specifically 5a, 5b, and 11. The cis ring fusion is insured by use of the Diels–Alder reaction, and the trans ring fusion is fixed by the necessity of a cis attachment of an intermediate five-membered cyclic lactamol to the existing cyclopentane ring in 9.