bluuebunny/crossref_metadata_2025 huggingface dataset:
Dielectric studies. Part XX. Molecular relaxation of some heterocyclic amines in dilute solution
Authors: Crossley J. , Walker S.
Published: May 2006

Dielectric constant and loss data have been obtained at microwave frequencies for acridine, 4-methyl-pyridine, phthalazine, quinoline, and isoquinoline in both cyclohexane and p-xylene solution. The data have been used to calculate relaxation times and apparent dipole moments. For phthalazine, quinoline, and isoquinoline in cyclohexane at 50 °C the distribution coefficient is zero and their relaxation times are very similar. Although the axes about which these three molecules may relax lead to different volumes being swept out, no variation in relaxation behavior has been detected, and each system can be characterized by one relaxation time. The relaxation times for all the heterocyclic molecules except quinoline and acridine in p-xylene are appreciably longer than in cyclohexane. Relaxation time values appear a sensitive means of detecting the weak molecular interaction between the amine and the p-xylene. The difference in behavior between the quinoline and acridine as opposed to isoquinoline could be attributed to a more appreciable steric effect in the former two, hindering the approach of the π-electrons of the p-xylene molecules to the hybridized lone pair on the nitrogen atom. No interaction is, in fact, detectable in the case of quinoline and acridine. The importance of allowing for weak intermolecular forces, even in dilute solution, when relaxation values are being anticipated, is emphasized.
Constraints on the determination of stability constants for metal complexes. II. The iron(III) phenolates
Authors: McBryde W. A. E.
Published: May 2006

Stability constants have been measured spectrophotometrically for the 1:1 complexes of iron(III) with phenol and five derivatives in background solutions having two different compositions, 0.027 M NaClO4 and 0 5 M KNO3 Conditional acidity constants for these phenols in the second of these media were also determined The experimental results were treated in two different ways to obtain values of the equilibrium constants and the molar extinction coefficients of the complexes It is apparent that the equilibrium in these cases must be studied under conditions, such as low pH and low concentration of iron, which militate against good precision in the results
Molecular force field for bromine pentafluoride
Authors: Pillai M. G. Krishna , Pillai P. Parameswaran
Published: May 2006

An attempt has been made to study the influence of lone pair electrons on the potential constants of BrF5 with a modified Urey–Bradley force field. It is found that the lone pair – bond pair repulsion is greater than the bond pair – bond pair repulsion. It is also concluded from a study of other molecules containing halogen atoms that the ratio of lone pair – bond pair interaction to bond pair – bond pair interaction is very nearly 1.23.
Oligomeric stannoxanes
Authors: Migdal Shmuel , Gertner David , Zilkha Albert
Published: May 2006

The controlled basic hydrolysis of tetrabutyl-1,3-dichlorodistannoxane under interfacial conditions was found to lead to α,ω-dichlorooligostannoxanes, Cl(SnBu2O)nSnBu2Cl, n being controlled by the molar ratio of base to distannoxane. These oligostannoxanes were identical with those prepared by other methods. They were used in the preparation of oligostannoxane dicarboxylates and organotin polyesters, having stannoxane recurring units in their backbone, by reaction with the sodium salts of mono- or dicarboxylic acids under interfacial conditions.
Détermination de la température thêta pour le système polyméthacrylate de méthyle – tétrachlorure de carbone
Authors: Ho-Duc Nga , Daoust Hubert
Published: May 2006

The theta temperature for the conventional polymethylmethacrylate – carbon tetrachloride system has been determined by light scattering and by viscometry. It is found to be 43.5 ± 1 °C by the first method and 48 ± 1 °C by the second.
Role of the triplet state in the benzene-sensitized decomposition of chloroform
Authors: Ng S. H. , Semeluk G. P. , Unger I.
Published: May 2006

A study has been made of the effect of increasing chloroform pressure on benzene and biacetyl emission under various conditions. No quenching of benzene fluorescence by chloroform is observed when excitation is by 2570 Å radiation, whether or not biacetyl is present. On the other hand, quenching of the sensitized biacetyl phosphorescence is pronounced. However, it is demonstrated that chloroform does not quench biacetyl phosphorescence when excitation occurs at 3660 Å, from which it can be concluded that chloroform preferentially accepts energy from the benzene triplet rather than the excited singlet. Therefore it is probably the triplet which is responsible for the benzene-photosensitized decomposition of chloroform previously reported.
Synthesis and nuclear magnetic resonance spectra of some partially acylated β-D-glucopyranosides
Authors: Tulloch A. P. , Hill A.
Published: May 2006

The synthesis of ten new partially acylated derivatives of methyl β-D-glucopyranoside, all with an acyl group at C-6, is described. The nuclear magnetic resonance spectra of these compounds, and of a number of related derivatives, have been measured using pyridine, acetone-d6, and deuteriochloroform as solvents. When OH-4 is acylated, the H-6 signals are at higher field (by 0.1–0.3 p.p.m.) than when OH-4 is not acylated, but this effect is not observed when OH-3 is acylated. When a trimethylsilyl ether group is introduced at C-4 the difference between the chemical shifts of the H-6 protons (δA –δB) increases markedly. Estimation of JBX and JAX (where B is the H-6 proton at higher field and X is H-5), from spectra obtained using acetone-d6 and pyridine as solvents, shows that JBX < JAX when there is an acyl group at C-4 but JBX > JAX when there is no acyl group at C-4.
Isolation and characterization of 4-chloro-3,4′;3′,4″-tercoumarin
Authors: Knight Allan R. , McIntyre John S.
Published: May 2006

The products from the reaction of 4-hydroxycoumarin with phosphorous oxychloride are the reported 4-chlorocoumarin and an additional compound of high molecular weight. This latter compound was characterized by substitution, degradation, and deuteration reactions as 4-chloro-3,4′;3′,4″-tercoumarin, a trimer corresponding to condensations between three coumarin molecules.
Mass spectra and proton magnetic resonance spectra of some tetrahydroprotoberberine alkaloids
Authors: Chen C.-Y. , MacLean D. B.
Published: May 2006

The mass spectra and the proton magnetic resonance spectra of tetrahydroprotoberberine alkaloids, oxygenated at the 9- and 10-positions, show marked differences from the spectra of those oxygenated at the 10- and 11-positions. These differences may be useful in structural studies on new members of this group of alkaloids.
Cleavage of carbon–silicon bonds by lithium aluminium hydride in tetrahydrofuran
Authors: Peddle G. J. D. , Roark D. N.
Published: May 2006

It was shown that many silicon–carbon bonds were readily broken by lithium aluminium hydride in refluxing tetrahydrofuran. The rate of cleavage was dependent upon the nature of the leaving group and of the other groups present on the silicon. Carbon–tin bonds were cleaved more readily than carbon–silicon bonds while carbon–germanium bonds were not cleaved.
Rearrangement of penicillins to anhydropenicillins
Authors: Wolfe Saul , Godfrey J. C. , Holdrege C. T. , Perron Y. G.
Published: May 2006

Anhydropenicillins are derived from penicillins by the removal of a molecule of water from the nucleus with concomitant rearrangement of the thiazolidine ring to an α,β-unsaturated-γ-thiolactone. Conditions are described for the preparation of the acid chlorides of penicillins; these compounds rearrange to anhydropenicillins upon treatment with a tertiary amine. Other less effective ways of performing the rearrangement are also given. The anhydropenicillins show infrared absorption at 5.5, 5.9, 6.0, and 6.1 μ, ultraviolet absorption near 270 mμ (ε = 12 000), and they possess extraordinary chemical stability. Possible reasons for these properties are discussed.
C-Aroylations of imides and N-aroylations of β-keto amides with aromatic esters by means of sodium hydride to form β-keto imides
Authors: Wolfe James F. , Trimitsis George B. , Hauser Charles R.
Published: May 2006

Aroylations at the methyl groups of N-acetylbenzamide and p-benzoylaminoacetophenone, and at a methylene position of succinimide with appropriate aromatic esters were effected by means of sodium hydride in refluxing monoglyme. Benzoylation at the amide group of α-benzoylacetamide and salicylamide were accomplished similarly. The yields of β-keto imides from these C- and N-aroylations by sodium hydride, with which intermediate dianions were evidently not formed, were generally much better than those obtained through dianions produced by means of an alkali amide in liquid ammonia. The synthetic utility of the sodium hydride method is discussed.
Optimum temperatures in pyrolysis gas chromatography
Authors: Sutton Russell , Harris W. E.
Published: May 2006

Pyrograms were recorded for a variety of compounds pyrolyzed in the gas phase in a quartz tube. The lowest temperature at which the major pyrolytic products are first formed and the lowest temperatures causing complete pyrolysis were determined and found to differ by about 80–120 °C. The temperatures of complete pyrolysis at the described experimental conditions are 600–650 °C for the most stable compounds. At temperatures above 700 °C the compounds were degraded primarily to methane, ethane, ethylene, or carbon.
Reactions of 1,2-dichlorohexafluorocyclopentene with secondary phosphines
Authors: Stockel Richard F.
Published: May 2006

Dicyclohexylphosphine and diphenylphosphine react with 1,2-dichlorohexafluorocyclopentene to give almost exclusively the monoderivative via displacement of a vinylic chlorine atom. With the former phosphine a disubstituted derivative is also found. In addition to analytical values and infrared spectroscopic data, both 19F and 31P nuclear magnetic resonance spectra support the proposed structures.
Structure of hetisinone
Authors: Aplin R. T. , Benn M. H. , Pelletier S. W. , Solo J. , Telang S. A. , Wright H.
Published: May 2006

The tentative structure proposed previously for a dehydrohetisine isolated from Delphinium cardinale Hook. has been confirmed. This alkaloid is identical with hetisinone, first obtained as a transformation product of hetisine, and subsequently isolated from D. denudatum.
Détermination des constantes de force et des amplitudes moyennes de vibration du sous-sulfure de carbone, C3S2
Authors: Diallo Alpha O.
Published: May 2006

The theory of the generalized mean amplitudes of vibration has been applied to the C3S2 molecule, which possesses a linear symmetrical structure. The numerical values of the force constants and the mean square parallel and perpendicular amplitudes at 298°K of all bonded and non-bonded pairs of atoms are calculated from spectroscopic vibrational frequencies by the Cyvin and Morino–Hirota methods, utilizing the symmetry coordinates. The "shrinkage" effect constants are also evaluated by means of the perpendicular mean square amplitudes.
Absolute rate constants for hydrocarbon oxidation. XI. The reactions of tertiary peroxy radicals
Authors: Howard J. A. , Ingold K. U.
Published: May 2006

Rate constants have been measured for the chain-terminating self-reactions of six tertiary peroxy radicals. The rate constants vary from ~ 1 × 103 M−1 s−1 for t-butylperoxy to ~ 6 × 104 M−1 s−1 for 1,1-diphenylethylperoxy radicals. It is suggested that the variation in the rate constants may be related to differences in the stability of the alkoxy radical products of tetroxide decomposition.Rate constants for hydrogen atom abstraction from aralkanes by tertiary peroxy radicals do not seem to be significantly affected by the structure of the attacking radical.In solution the triphenylmethylperoxy radical probably exists in equilibrium with the triphenylmethyl radical and oxygen. Chain termination in oxidations involving the triphenylmethylperoxy radical as the chain carrier occurs by the reaction of this radical with a triphenylmethyl radical.
Extended Hückel molecular orbital calculations on some titanium–oxygen systems
Authors: Hsia Yu-Ping
Published: May 2006

Extended Hückel molecular orbital calculations have been performed on localized TiO68− units with the precise geometry of such a unit in solid rutile, anatase, and brookite TiO2 and tetragonal BaTiO3. The relative values of one-electron energy levels in these compounds are obtained in terms of a "self-consistent" charge and population calculation. Examination of the resulting energy levels and charge distributions has led to reasonable explanations of previously unexplained data on (1) the visible and near-ultraviolet absorption spectra of these compounds, (2) the low energy X-ray absorption edges of rutile, anatase, and brookite TiO2, and (3) the pressure dependence of the absorption edges of rutile TiO2 and tetragonal BaTiO3.
An empirical periodic correlation of for the methyl group
Authors: Yue C. P.
Published: May 2006

The carbon-13-proton coupling constant J13C–H for the methyl group is found to correlate linearly with the product EX × γX–C, where EX is the electronegativity of the substituent X and γX–C is the X—C bond distance. Unknown values of J13C–H for the methyl group are predicted from the linear correlation. It is concluded that the "size effect" and the "polarization effect" are important in determining J13C–H.
A calorimetric study of periodate species in aqueous solution
Authors: Mercer E. E. , Farrar D. T.
Published: May 2006

Heats of several reactions involving sodium periodate, NaIO4(c), have been measured in an isothermal jacketed calorimeter. The apparent acid ionization constant of periodic acid was redetermined at an ionic strength of 0.13. From these data the following values for heats of formation at 25.00° have been calculated: NaIO4(c), −105.15 ± 0.30; IO4−(aq), −38.8 ± 0.4; H5IO6(aq), −188.9 ± 1.0; H4IO6−(aq), −186.3 ± 1.0 kcal/mole.
Primary process(es) in the mercury-photosensitized decomposition of dimethyl ether at 2537 Å
Authors: Payette R. , Bertrand M. , Rousseau Y.
Published: May 2006

The mercury-photosensitized decomposition of dimethyl ether has been studied at room temperature and at pressures ranging from 10 to 200 Torr.The formation of an excited dimethyl ether (DME) molecule has been verified by following the rates of formation of methane, ethane, and carbon monoxide with various ether pressures.The study of the variation of the quantum yield of molecular hydrogen formation with absorbed light intensity at high ether pressures has shown that the primary process involves the dissociation of ether molecules into hydrogen atoms and methoxy methyl radicals:[Formula: see text]The results presented in this paper indicate that the excited DME molecule can originate in a radical recombination between hydrogen atoms and methoxy methyl radicals.
Thermal decomposition of di-tert-butyl peroxide at high pressure
Authors: Shaw D. H. , Pritchard H. O.
Published: May 2006

The thermal decomposition of di-tert-butyl peroxide has been studied in the presence of carbon dioxide at total pressures from 0.05 to 15 atm and temperatures from 90–130 °C. The first-order rate constant for the decomposition is independent of total pressure in this range, with Arrhenius parameters E = 37.8 ± 0.3 kcal/mole and log A(s−1) = 15.8+0.2. A reevaluation of previous data on this reaction leads us to recommend E = 37.78 ± 0.06 kcal/mole and log A(s−1) = 15.80 ± 0.03 over the temperature range 90–350 °C; extension of this range to higher temperatures using a shock tube would be worthwhile.
The electrochemistry and the kinetics of the formation of ruthenium(II) nitrogen complexes
Authors: Itzkovitch I. J. , Page John A.
Published: May 2006

Electrolysis at a mercury cathode controlled at −0.50 V (vs. standard calomel electrode s.c.e.) in a H2SO4–K2SO4 electrolyte with pH of 2.6 and saturated with Ar gas has been used to prepare RuII–(NH3)5X. The reaction of this species with N2 in the aqueous base electrolyte at 26 °C has been studied and found to follow the equations:[Formula: see text]In base electrolyte saturated with N2 at 1 atm (CN2 ≈ 6 × 10−4 M) the value of the apparent first order constant, k′m is 4.4 × 10−5 s−1 and the value of kd is 4.2 × 10−2 1 mole−1 s−1.The electrochemistry of the various ruthenium species was also investigated in the H2SO4–K2SO4 electrolyte. At the dropping mercury electrode, RuIII (NH3)5Cl gave a well-defined one electron reduction wave with E1/2 = −0.27 V; RuII (NH3)5X gave a well-defined one electron oxidation wave with E1/2 = −0.25 V. The nitrogen complexes gave oxidation waves at a rotating platinum microelectrode, the monomer with E1/2 = +0.72 V and the dimer with E1/2 = +0.78 V.
Hydrogen atom abstraction from substituted toluenes by tert-butoxy radical
Authors: Gilliom R. D. , Howles J. R.
Published: May 2006

The relative rates of abstraction of benzylic hydrogen from substituted toluenes by tert-butoxy radicals generated from tert-butyl hypochlorite have been reexamined. Abstraction from para-methylanisole was shown to occur at the ether methyl as well as at the benzylic methyl group. For this reason the compound was excluded from an analysis of the polar effect. A slightly better Hammett correlation was obtained using sigma rather than sigma-plus values.
Reductions with sulfurated borohydrides. I. Preparation of sulfurated borohydrides
Authors: Lalancette J. M. , Frêche A. , Monteux R.
Published: May 2006

Sodium borohydride reacts with sulfur at room temperature in the presence of appropriate organic solvents to give a sulfurated borohydride: NaBH2S3. The formulation of this hydride has been established by infrared, nuclear magnetic resonance, and elementary analysis. Thermal decomposition and hydrolysis are reported. The reaction observed with NaBH4 appears to be general between borohydrides and the lower elements of Group VIA: Se and Te. A facile preparative method of NaBH2S3 is presented.
Octacyanomolybdate(IV) ion, scavenger for hydroxyl radical
Authors: Sharma B. K.
Published: May 2006

The oxidation of potassium octacyanomolybdate(IV) in 0.4 M sulfuric acid solutions (oxygenated) has been studied; G[Mo(CN)83−] was found to be 2.7, which is close to the G(OH) value of 2.9.
Carbon tetrachloride as solvent in proton magnetic resonance. Importance of size and charge effects of proximate substituents
Authors: Schaefer T. , Richardson B. , Schwenk R.
Published: May 2006

A model (not a theory), based on steric and charge removal characteristics of the substituents, is used to rationalize the low-field shifts caused by carbon tetrachloride (compared to cyclohexane) in the proton resonance spectra of 22 polyhalosubstituted benzenes. The low-field shifts are as large as 0.16 p.p.m. and these are found for protons situated between two ortho fluorine substituents. Larger halogens present a steric hindrance to the approach of the polarizable C—Cl bonds of the solvent and lead to smaller shifts. The charge removed from the region of the C—H bonds by the substituents is estimated by means of a function of the bond dipole divided by the bond length. A shape effect, arising when two hydrogens are ortho to each other, also appears to be present if there are bulky distant groups.
Nuclear magnetic resonance studies on the configurations and conformations of heterocyclic nitrosamines
Authors: Chow Y. L. , Colón C. J.
Published: May 2006

The nuclear magnetic resonance spectra of various heterocyclic nitrosamines were studied in solution. A qualitative view of the long-range diamagnetic effects of a nitrosamino group is advanced and correlated with the chemical shifts of α-equatorial protons and the methyl group in those nitrosamines possessing a preferred conformation or a rigid system. The use of this correlation to decide the configuration and conformation of heterocyclic nitrosamines is discussed. A large chemical shift difference (ca. 3 p.p.m.) between a cis α-axial and a cis α-equatorial proton was noted.
Synthesis of phenolic esters with potential long-lasting insect-repellent properties
Authors: Quintana Ronald P. , Garson Lorrin R. , Lasslo Andrew
Published: May 2006

The synthesis of undecanoic acid esters of resorcinol, 4-chlororesorcinol, hexachlorophene, o-chlorophenol, and p-chlorophenol is described. The compounds were designed to provide, potentially, perdurable insect-repellent activity. When the synthesis of esters of resorcinol and 4-chlororesorcinol was attempted with undecanoic acid, under acid catalysis, principally ketones and ketoesters were isolated. The originally sought esters were obtained, however, by the reaction of the phenols with undecanoyl chloride in the presence of pyridine. The infrared, nuclear magnetic resonance, and mass spectra of the compounds are discussed.
Synthesis of 2-amino-2-deoxy-D-allose, 2-amino-2-deoxy-D-altrose, and 2-deoxy-D-ribo-hexose from 3,4,5,6-tetraacetoxy-D-ribo-1-nitro-1-hexene
Authors: Perry M. B. , Furdová Jana
Published: May 2006

3,4,5,6-Tetraacetoxy-D-ribo-1-nitro-1-hexene with methanolic ammonia afforded a mixture of 2-acetamido-1,2-dideoxy-1-nitro-D-allitol and 2-acetamido-1,2-dideoxy-1-nitro-D-altritol, which were converted via the Nef reaction to 2-acetamido-2-deoxy-D-allose and 2-acetamido-2-deoxy-D-altrose. 2-Amino-2-deoxy-D-allose hydrochloride and 2-amino-2-deoxy-D-altrose hydrochloride were obtained from the 2-acetamido-2-deoxy-glycoses.Reduction of 3,4,5,6-tetraacetoxy-D-ribo-1-nitro-1-hexene afforded 3,4,5,6-tetra-O-acetyl-1,2-dideoxy-1-nitro-D-ribo-hexitol which was converted via the Nef reaction to 2-deoxy-D-ribo-hexose.
The structures of three alkaloids from Fumaria officinalis L.
Authors: Saunders J. K. , Bell R. A. , Chen C.-Y. , MacLean D. B. , Manske R. H. F.
Published: May 2006

Structures are proposed for three alkaloids isolated from Fumaria officinalisL. The three alkaloids, with a common ring system, are structurally related to the known ochotensimine.
Reactions of hot hydrogen atoms in mercaptan–ethylene systems
Authors: Steer R. P. , Knight A. R.
Published: May 2006

Investigation of the photolysis of methanethiol and ethanethiol vapor in the presence of ethylene and inert gas has indicated the formation of energetic hydrogen atoms in the primary process. Rate constant ratios for the reactions of these species have been found to be pressure dependent.
The transmission of polar effects. Part V. The kinetics of esterification with diazodiphenylmethane and the ionization of substituted acetic and propionic acids in several solvents
Authors: Bowden Keith , Hardy M. , Parkin D. C.
Published: May 2006

The rate coefficients for the reaction with diazodiphenylmethane in methanol, ethanol, isopropyl alcohol,t-butyl alcohol, 2-methoxyethanol, 2-n-butoxyethanol, dimethyl sulfoxide, ethyl acetate, and toluene at 30° and the pKa values in water, 50% ethanol–water, and 80% 2-methoxyethanol–water of 18 substituted acetic and propionic acids have been determined. A further 14 acids have been studied to a more limited extent. The effect of substitution has been estimated by linear free energy relations. The reaction constants for the ionization reaction are almost independent of the medium. This is interpreted as being due to the field effect of the proximate polar substituents passing through the molecular cavity almost alone. The occurrence of steric inhibition of solvation causing acid weakening for bulky multi-substitution is confirmed. The reaction constants for the esterification reaction are affected by the solvent. This is attributed to dependence on solvation of the transition state.
Dielectric behavior of low boiling chlorides in the liquid, solid, and adsorbed states
Authors: McMullen T. , Crozier E. D. , McIntosh R.
Published: May 2006

The complex dielectric constants of hydrogen, methyl, and ethyl chlorides have been measured, for the purpose of comparison with the present and future adsorption studies. The hydrogen chloride results agree with those of Cole and Swensen (22). Studies of hydrogen and ethyl chlorides adsorbed on finely divided sodium chloride show two particularly interesting phenomena. Adsorbed hydrogen chloride shows an unusually high polarizability at monolayer surface coverage, which then decreases again with increasing adsorption. Adsorbed ethyl chloride also shows a very high polarizability at a particular surface coverage, but this maximum occurs at about one-fourth of monolayer coverage, and is accompanied by loss, in contrast to the former case.
Determination of rhenium: chlorine ratios in complexes by neutron activation
Authors: Courrier W. D. , Guest A. , Lock C. J. L. , Tomlinson R. H.
Published: May 2006

A method is described for the simultaneous determination of rhenium and chlorine in complex compounds. By determining atom ratios, it is unnecessary to weigh samples. The advantages of this method when applied to air-unstable compounds are described.
Melting points of inorganic fluorides
Authors: Kojima H. , Whiteway S. G. , Masson C. R.
Published: May 2006

An apparatus is described for purifying inorganic fluorides by passing anhydrous HF through the melts. Melting points of nine fluorides purified in this way were raised and were sometimes significantly higher than the 'best' literature values.
Substitutions électrophiles en série naphtalénique. IV. Sur le diméthyl-2,6 naphtalène
Authors: Richer Jean-Claude , Baskevitch Nicolas
Published: May 2006

not available
Synthesis of DL-threo- and DL-erythro-β-hydroxyisoleucine
Authors: Dobson T. A. , Vining L. C.
Published: May 2006

DL-threo- and DL-erythro-β-Hydroxyisoleucine were prepared from cis- and trans-3-methylpent-2-enoic acids, respectively. The configuration of the erythro isomer was established from its synthesis by two independent routes. The diastereoisomers, and those of other β-hydroxy amino acids, can be distinguished by examination of their proton magnetic resonance spectra.
Complexes of N-methylxanthines with carboxylic acids
Authors: Cook Denys , Regnier Zephyr R.
Published: May 2006

Complexes of caffeine and theobromine, with acetic and salicylic acid, have been studied by means of infrared spectroscopy. In the complexes with aromatic acids a fairly strong hydrogen bond exists between the carboxylic OH group and the nitrogen atom N-9 in the imidazole ring. The acetic acid complexes involve no strong intermolecular forces and are probably weak lattice complexes.The complexes with aromatic acids are discussed in relation to theories of lipid solubility and gastrointestinal absorption.
The structure of 5,5,5-trifluoro-4-hydroxypentenoic acid lactone
Authors: Filler Robert , Schure Ralph M.
Published: May 2006

not available
Ranunculin
Authors: Benn M. H. , Yelland Lois Jean
Published: May 2006

not available
Theoretical views on Szilard Chalmers reactions in solid systems. II. Parent reformation by billiard-ball collisions
Authors: Wong W. H. , Wiles D. R.
Published: May 2006

The problem of billiard-ball replacement reactions of atoms centrally located in the molecule has been approached, using the approximation of simple two-body collisions. The reentry process has been separated into steps which can be handled by straightforward mathematical operations. Collision diameters for given energy transfer were calculated using an exponentially screened potential.Species treated include dicyclopentadienyl metals, arene metal carbonyls, and hexacoordinated complex ions, although the method is applicable to many other types of compound. An important result is that the probability of successful billiard-ball replacement is not sensitive to the initial energy, as long as this is not too low. It is concluded that this method is, at its present stage, most useful in calculating lower limits for billiard-ball reformation by following the projectile energy down to ca. 100 eV. Below this energy it is considered that thermal decomposition of the reformed molecule is likely. Results of the calculation are compared with experimental data, and further experiments are suggested by which the contribution of billiard-ball collisions may be directly assessed.
Cinétique de l'adsorption compétitive
Authors: Baret J. F. , Bois A. G.
Published: May 2006

not available
Infrared spectra of pyridine sorbed on porous glass
Authors: Low M. J. D. , Rao V. V. Subba
Published: May 2006

Infrared spectra were recorded of pyridine (PY) sorbed on highly dehydroxylated, deuterated, and fluoridated porous glass, as well as on pure silica and boria-impregnated silica. The hydrogen atoms of sorbed PY exchange with surface OD groups. Physical adsorption occurs by hydrogen bonding of PY to SiOH and B—OH groups via the PY nitrogen atom; there is some interaction of the ring π system with OH groups. Surface B:PY complexes form by coordination of PY to boron; the B:PY may be hydrogen bonded to B—OH groups. Some PY dissociates, and OH groups are generated.
Anion-molecule complexes in solution. II. The complexing of halide ions with acetylated β-D-glucopyranosyl derivatives
Authors: Martin J. S. , Hayami Jun-Ichi , Lemieux R. U.
Published: May 2006

Tetra-O-acetyl-β-D-glucopyranosyl halides and phenoxides in solution in acetonitrile showed a specific deshielding of H-1, H-3, and H-5 on addition of tetraethylammonium halides. The shifts and equilibrium constants increased as the anion radius decreased. The ortho hydrogens of the phenoxide aglucons were also significantly deshielded. The strong dependence of the equilibrium constants of the phenoxide compounds on p-substituents indicated considerable involvement of the phenyl groups in a specific conformation. A simple electrostatic model was successful in correlating the energies and predicting the structures of the complexes. It was not necessary to postulate specific hydrogen bonding to account for association of the anion with an electrophilic region of the molecule. The calculations required specific orientations of acetoxy groups with respect to the pyranose ring which are consistent with those of related studies. In favorable circumstances, the method may be used as a probe for electrophilic regions in molecules.
Thermal reactions of propylene oxide
Authors: Blades Arthur T.
Published: May 2006

Heterogeneous reactions have been shown to contribute to the formation of propionaldehyde, acetone, and allylol in the pyrolysis of propylene oxide. Methyl vinyl ether, however, is formed entirely homogeneously and may be an intermediate in the oxygen atom – propylene system.
Reductive C-alkylation
Authors: Gregorovich B. V. , Liang K. S. Y. , Clugston D. M. , MacDonald S. F.
Published: May 2006

At 95–115°, paraformaldehyde and hydriodic acid completely C-methylate aromatics such as benzene and phenol. Pyrroles are C-methylated similarly, carbethoxy and acetyl groups being lost. In hydriodic acid at 15–45°, typical pyrroles retain these groups and all free positions are C-alkylated, methylated by paraformaldehyde, or otherwise alkylated by the appropriate carbonyl compound. The alkylation of a 2-free- by a 2-formylpyrrole led to a dipyrrylmethane. With pyrroles, hydriodic acid may be replaced by another strong acid and a reducing agent. This was necessary when a β-free pyrrole gave the iodo–alkyl derivative rather than the expected product.
Schmidt rearrangement of chromanones
Authors: Bhalerao U. T. , Thyagarajan G.
Published: May 2006

The mechanism of the Schmidt rearrangement has been examined in the conversion of chromanones to 1,4- and 1,5-benzoxazepinones. With substituents in the 6-, 7-, or 8-position, only electronic effects prevail resulting in the exclusive formation of 1,4-benzoxazepinones. Steric effects come into play with increasing bulk of substituents in the 5-position of the chromanone. Results now presented favor more than one pathway for the products to arise. Nuclear magnetic resonance spectra have been used to distinguish between the isomeric 1,4- and 1,5-benzoxazepinones.Several new chromanones have been synthesized.
Convenient synthesis of t-butyl alcohol-d
Authors: Wolfe Saul , Lee Wha Suk , Campbell John R.
Published: May 2006

The title compound is prepared by alkaline hydrolysis (NaOD–D2O) of a t-butyl ester. With t-butyl acetate the alcohol salts out of the reaction mixture and is easily separated and dried; however, slow concurrent exchange of the sodium acetate reduces the deuterium content of the alcohol to 95%. With t-butyl benzoate pure t-butyl alcohol-d is isolated by distillation of the alcohol–water azeotrope and drying.
8-Aryltheophyllines
Authors: Bariana D. S.
Published: May 2006

The synthesis of a number of 8-aryltheophyllines is described. These compounds were tested as coronary vasodilators.
Studies in dehydrogenation of 6-methoxy-1-tetralone. Structure of a novel product formed with tetrachloro-1,2-benzoquinone
Authors: Kasturi T. R. , Arunachalam T.
Published: May 2006

Dehydrogenation of 6-methoxy-1-tetralone (1) using palladium–carbon (30%), palladium black, and quinones has been studied with a view to preparing 6-methoxy-1-naphthol (3). A novel addition product formed, during dehydrogenation of 1 with tetrachloro-1,2-benzoquinone, has been proved to be 2,2-(tetrachloro-o-phenylenedioxy)-3,4-dehydro-6-methoxy-1-tetralone (5). Bromination of 1 followed by dehydrobromination gave the naphthol 3 in excellent yield.
Epoxides and trans-chlorohydrins of 3-methoxycyclopentene and their use in conformational studies in the cyclopentane system
Authors: Langstaff E. J. , Moir R. Y. , Bannard R. A. B. , Casselman A. A.
Published: May 2006

The stereoisomeric oxides of 3-methoxycyclopentene (3 and 4) and the four trans-chlorohydrins of the same olefin (6–9) were prepared by methods resembling those used previously in the cyclohexane system. Structure proofs were more difficult than in the cyclohexanes, but served to illustrate some interesting chemistry. Product ratios in the cleavage of each of the epoxides with hydrogen chloride were used to deduce the probable conformations of the four transition states, by comparing the results with those from the cyclohexane system. An unexpected outcome of the work was the new convincing evidence obtained for the intervention of chloronium ions in the addition of "hypochlorous acid" to the olefin.
Novel reaction of some 2-aminoheterocycles with acrylophenones
Authors: Findlay J. A. , Langler R. F. , Podesva C. , Vagi K.
Published: May 2006

An unusual adduct is formed when 3-methylacrylophenone is treated with 2-aminothiazole. The structure of this product has been established as 4a. Similar adducts have been prepared from acrylophenones with other aminoheterocycles
Synthesis of 5H-dibenzo[a,d]cycloheptene-5-carboxylic acid and related compounds. 1,5-Hydride transfer to inductively destabilized carbonium ions
Authors: Horning D. E. , Muchowski J. M.
Published: May 2006

The synthesis of 10,11-dihydro-5H-dibenzo[a,d]cycloheptene-5-carboxylic acid (2) and several derivatives of 5H-dibenzo[a,d]cycloheptene-5-carboxylic acid (1; a–c) from 5-hydroxy-10,11-dihydro-5H-dibenzo[a,d]cycloheptene-5-carboxylic acid and derivatives thereof (3; a–c) is described.The p-toluenesulfonic acid-catalyzed elimination of water (at 110.6° in toluene) from the deuterated hydroxy ester (3b; C-10, 11 d2) resulted in the incorporation of deuterium at C-5 of the olefinic ester 1b with a KH/KD of 2.76. The large magnitude of this isotope effect indicated that the reaction proceeded via a rate-determining transannular 1,5-hydride transfer from one of the benzylic positions of 3b to the carbonium ion generated alpha to the methoxy-carbonyl group.
Synthesis of 6-chloro-9-(6′-deoxy-3′-C-methyl-2′,3′,4′-tri-O-methyl- β-D-allopyranosyl)purine: a branched-chain sugar nucleoside
Authors: Howarth G. B. , Szarek W. A. , Jones J. K. N.
Published: May 2006

The preparation of 6-deoxy-3-C-methyl-2,3,4-tri-O-metliyl-D-allopyranose (7), a branclied-chain sugar with the same constitution as nogalose from the antibiotic nogalamycin, is described. Condensation of the 1-O-acetyl derivative 8 with 6-chloropurine by the fusion method gave 6-chloro-9-(6′-deoxy-3′-C-methyl-2′,3′,4′-tri-O-methyl-β-D-allopyranosyl)purine (9), which to our knowledge is the first synthetic, purine nucleoside containing a branched-chain sugar with a pyranose ring.
On the lead tetraacetate and related oxidations of aromatic ketoximes
Authors: Frojmovic M. M. , Just G.
Published: May 2006

Fluorenone and benzophenone oxime react in glacial acetic acid with lead tetraacetate to give parent ketones, geminal dinitromethanes, iminyl ketal derivatives (9,9-difluorenylideniminoxylfluorene and 1,1-bis(diphenylmethylideniminoxyl)-diphenylmethane), and minor amounts of oxime O-acetate. Benzophenone nitrimine is also formed but only in the absence of oxygen. Side reactions due to nitric oxide, oxygen, and nitrogen dioxide take place. Separate studies with these oxidizing agents have therefore been conducted. The lead tetraacetate oxidation of these oximes in methylene chloride (or any other solvent) is complete with a half-mole equivalent of lead tetraacetate, is insensitive to molecular oxygen, and affords mainly parent ketone and ketazinemonoxides. No ketazine-bis-N-oxides, obtained from the ferricyanide oxidation of these oximes, are formed. The model oximes, benzil anti-monoxime, xanthone oxime, and indanone oxime have been studied in the light of these observations. Mechanisms involving iminoxyl radicals have been postulated for all reactions studied.
Methyl 2-hydroxy-4-methoxy-6-phenylbenzoate and methyl 2-hydroxy-6-methoxy-4-phenylbenzoate: reassignment of a structure
Authors: Howarth T. Trefor , Harris Thomas M.
Published: May 2006

Methyl 2-hydroxy-4-methoxy-6-phenylbenzoate (3b) was synthesized by treatment of methyl 6-phenyl-β-resorcylate (3a) with diazomethane. 5-Phenylresorcinol (8) was carboxylated in a Kolbe–Schmitt reaction to give γ-resorcylic acid 7b. Treatment of 7b with diazomethane gave a mixture of the corresponding dihydroxy ester 7c, monomethoxy ester 7a, and dimethoxy ester 7d. Evidence is presented that the structure of a compound obtained by Douglas and Money from base treatment of phenyl dipyrone 1 is 7a rather than the previously assigned 3b. A mechanistic proposal is presented.
Reaction of 1,2:5,6-di-O-isopropylidene-3-O-p-nitrophenylsulfonyl (and 3-O-p-tolylsulfonyl) α-D-glucofuranose with tetramethylammonium hydroxide in methyl sulfoxide
Authors: Rosenthal Alex , Nguyen L.
Published: May 2006

Treatment of 1,2:5,6-di-O-isopropylidene-3-O-p-tolylsulfonyl-α-D-glucofuranose with tetramethylammonium hydroxide in methyl sulfoxide gave 1,2:5,6-di-O-isopropylidene-α-D-glucofuranose in 89% yield. Under similar conditions, the 3-O-p-nitrobenzenesulfonate ester of 1,2:5,6-di-O-isopropylidene-α-D-glucofuranose 1, gave 3-O-[p-(3-deoxy-1,2:5,6-di-O-isopropylidene-α-D-glucofuranose-3-yl)oxyphenylsulfonyl]-1,2:5,6-di-O-isopropylidene-α-D-gluocofuranose 2, and 1,2:5,6-di-O-isopropylidene-3-O-p-nitrophenyl-α-D-glucofuranose 3. A discussion of the probable mechanism of this reaction is based on a study of the products obtained by application of the same reaction to ethyl p-nitrobenzenesulfonate.
Etude potentiométrique de la réaction du glycylglycine avec les nitrilotriacétates métalliques
Authors: Israeli Julius , Cecchetti Maria
Published: May 2006

not available
Studies of the oxide surfaces at the liquid–solid interface. Part II. Fe oxides
Authors: Ahmed Syed M. , Maksimov Dimitry
Published: May 2006

The double layer on hematite and magnetite in KNO3, NaClO4, and KCl solutions has been investigated by studying the equilibrium distribution of the potential determining ions (H+ and OH−) at the interface as a function of their electrochemical potentials. Data have been obtained on the pHs of the zero point of charge (5.3 and 6.4 for hematite and magnetite, respectively, in 0.001 M KNO3 solution), the surface charge densities, q±, and the differential capacities C(±) of the double layer.For hematite, the q+ values in NO3− and ClO4− solutions are due to chemisorption of H+ on the surface, with NO3− and ClO4− showing no tendency for specific adsorption. In KCl solutions, high values of q+ were obtained, depending on Cl− concentration that are attributed to the replacement of the surface–OH groups by Cl− (specific adsorption). Magnetite (a semiconductor) shows anomalous behavior with respect to H+ adsorption.The negative charge on the two oxides originates from acidic dissociation of the surface–OH groups which is followed by adsorption of K+ on the surface. At high values of q−, K+ ions are specifically adsorbed on the surface-metal atoms through an O2− bridge.
Diffusive and convective flow in a hydrogen-atom flow system
Authors: Rudnick Philip B. , Toby Sidney
Published: May 2006

Diffusive and convective flow was studied in a hydrogen-atom flow system using an isothermal calorimetric detector. By varying detector area, total pressure, and linear flow rate, the importance of axial diffusion in the system was investigated. Under conditions of predominantly diffusive flow, signal–distance plots were independent of flow rate. When convective flow predominated, concentration–time plots were independent of flow rate. The efficiency of a detector was clearly dependent on its surface area within wide limits, but diffusion gradients produced by the presence of even large detectors did not appear to be important.
Nox2-containing NADPH oxidase and Akt activation play a key role in angiotensin II-induced cardiomyocyte hypertrophy
Authors: Hingtgen Shawn D. , Tian Xin , Yang Jusan , Dunlay Shannon M. , Peek Andrew S. , Wu Yihe , Sharma Ram V. , Engelhardt John F. , Davisson Robin L.
Published: May 2006

Angiotensin II (ANG II) has profound effects on the development and progression of pathological cardiac hypertrophy; however, the intracellular signaling mechanisms are not fully understood. In this study, we used genetic tools to test the hypothesis that increased formation of superoxide (O2−·) radicals from a Rac1-regulated Nox2-containing NADPH oxidase is a key upstream mediator of ANG II-induced activation of serine-threonine kinase Akt, and that this signaling cascade plays a crucial role in ANG II-dependent cardiomyocyte hypertrophy. ANG II caused a significant time-dependent increase in Rac1 activation and O2−· production in primary neonatal rat cardiomyocytes, and these responses were abolished by adenoviral (Ad)-mediated expression of a dominant-negative Rac1 (AdN17Rac1) or cytoplasmic Cu/ZnSOD (AdCu/ZnSOD). Moreover, both AdN17Rac1 and AdCu/ZnSOD significantly attenuated ANG II-stimulated increases in cardiomyocyte size. Quantitative real-time PCR analysis demonstrated that Nox2 is the homolog expressed at highest levels in primary neonatal cardiomyocytes, and small interference RNA (siRNA) directed against it selectively decreased Nox2 expression by >95% and abolished both ANG II-induced O2−· generation and cardiomyocyte hypertrophy. Finally, ANG II caused a time-dependent increase in Akt activity via activation of AT1 receptors, and this response was abolished by Ad-mediated expression of cytosolic human O2−· dismutase (AdCu/ZnSOD). Furthermore, pretreatment of cardiomyocytes with dominant-negative Akt (AdDNAkt) abolished ANG II-induced cellular hypertrophy. These findings suggest that O2−· generated by a Nox2-containing NADPH oxidase is a central mediator of ANG II-induced Akt activation and cardiomyocyte hypertrophy, and that dysregulation of this signaling cascade may play an important role in cardiac hypertrophy.
Photochromism of indolino‐benzopyrans studied by NMR and UV‐visible spectroscopy
Authors: Delbaere S. , Berthet J. , Salvador M. A. , Vermeersch G. , Oliveira M. M.
Published: May 2006

The synthesis of photochromic 3,3‐di(4′‐fluorophenyl)‐3H‐benzopyrans fused to an indole moiety
is described. The structures of photomerocyanines elucidated by NMR spectroscopy and spectrokinetic data (λmax⁡ of colored form, colorability, and rate constant of bleaching) obtained by UV‐visible spectroscopy are reported.
A scalarization technique for computing the power and exponentialmoments of Gaussian random matrices
Authors: Vladimirov Igor , Thompson Bevan
Published: May 2006

We consider the problems of computing the power and exponential
moments EXs and EetX of square Gaussian random
matrices X = A + BWC for positive integer s and real t, where
W is a standard normal random vector and A, B, C are
appropriately dimensioned constant matrices. We solve the problems
by a matrix product scalarization technique and interpret the
solutions in system‐theoretic terms. The results of the paper are
applicable to Bayesian prediction in multivariate autoregressive
time series and mean‐reverting diffusion processes.
Random fixed point theorems for multivalued nonexpansivenon‐self‐random operators
Authors: Plubtieng S. , Kumam P.
Published: May 2006

Let (Ω, Σ)
be a measurable space, with Σ a
sigma‐algebra of subset of Ω, and let C
be a nonempty
bounded closed convex separable subset of a Banach space X,
whose characteristic of noncompact convexity is less than 1,
KC(X)
the family of all compact convex subsets of X.
We prove that a multivalued nonexpansive non‐self‐random operator
T : Ω × C → KC(X), 1‐χ‐contractive mapping,
satisfying an inwardness condition has a random fixed point.
The single server queue and the storage model: Large deviations and fixed points
Authors: Draief Moez
Published: May 2006

We consider the coupling of a single server queue and a storage
model defined as a queue/store model. We establish that if the
input variables, arrivals at the queue and store, satisfy large
deviations principles and are linked through an
exponential tilting, then the output variables
(departures from each system) satisfy large deviations principles
with the same rate function.
β‐Amyloid Degradation and Alzheimer′s Disease
Authors: Wang Deng-Shun , Dickson Dennis W. , Malter James S.
Published: May 2006

Extensive β‐amyloid (Aβ) deposits in brain parenchyma
in the form of senile plaques and in blood vessels in the form of
amyloid angiopathy are pathological hallmarks of Alzheimer′s
disease (AD). The mechanisms underlying Aβ deposition
remain unclear. Major efforts have focused on Aβ production,
but there is little to suggest that increased production of
Aβ plays a role in Aβ deposition, except for rare
familial forms of AD. Thus, other mechanisms must be involved in
the accumulation of Aβ in AD. Recent data shows that
impaired clearance may play an important role in Aβ
accumulation in the pathogenesis of AD. This review focuses on our
current knowledge of Aβ‐degrading enzymes, including
neprilysin (NEP), endothelin‐converting enzyme (ECE),
insulin‐degrading enzyme (IDE), angiotensin‐converting enzyme
(ACE), and the plasmin/uPA/tPA system as they relate to amyloid
deposition in AD.
Preparation and Characterization of Waterborne Polyurethaneurea Composed of Dimer Fatty Acid Polyester Polyol
Authors: Jiang Lin , Xu Qiang , Hu Chun Pu
Published: May 2006

A series of polyurethaneurea (PUU) aqueous dispersions, which were
stable at ambient temperature for more than 1 year, were prepared
with C 36‐dimer‐fatty‐acid‐based polyester polyol, isophorone
diisocyanate, dimethylol propionic acid, and ethylenediamine. The
particle size of all these PUU (DPU) aqueous dispersions
(<100 nm) was less than that of comparable specimens, that
is, poly‐(neopentyl glycol adipate) polyester‐polyol‐based PUU
(APU) aqueous dispersions, and the polydispersity index was very
narrow (≤1.13). The films prepared with the DPU aqueous dispersions
exhibited excellent waterproof performance, such as low amount of
water absorption (1.3 wt%), and good mechanical properties
(hardness and tensile strength), resulting from the strong
hydrogen bonding in urea carbonyl groups and the perfect ordered
structure of hard segments compared with those prepared with the
APU aqueous dispersions. The surface hydrophobicity of the films
prepared with modified DPU aqueous dispersions, which were
modified with a fluorinated polyacrylate emulsion, was excellent,
as the water contact angle on the surface of such films rose up to
100. The mechanical properties of such modified DPU films were
further enhanced.