bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis and Reactions of 1-Alkyl-3-(o-carbalkoxyphenyl)-triazenes
Authors: LeBlanc Raymond J. , Vaughan Keith
Published: May 2006

The reaction of diazotized anthranilate esters with primary aliphatic amines has been reinvestigated, giving rise to a new series of comparatively unstable 1-alkyl-3-(o-carbalkoxyphenyl)-triazenes (3). The structures of the products have been confirmed by spectroscopic analysis, molecular ion mass measurements, and from the results of chemical degradation. The spectroscopic properties indicate a preference for the tautomer in which the azo-group is non-conjugated with the benzene ring, Ar•NH•N=N•R; this hypothesis is partly supported by the chemical degradation. In general, the triazenes (3) break down by fragmentation of the triazene moiety to give anthranilic acid derivatives, or undergo cyclization to 3-alkyltriazinones (1). The alkyltriazinones are also obtained directly in the coupling reaction of the diazonium salt with the amine in the presence of a sodium acetate buffer. The cyclization is quantitative when catalyzed by activity V alumina; a wide variation in the product distribution obtained by reaction with different types of alumina has been observed, and the correlation of these results with the known surface structure of alumina is discussed. Finally, an explanation is offered for the difference between the results of the present work and previous reports.
Long-range Spin–Spin Coupling Constants from Amino Protons and 15N to Ring Protons in Aniline-15N and Some Derivatives. INDO Molecular Orbital Calculations
Authors: Wasylishen R. , Rowbotham J. B. , Ernst L. , Schaefer T.
Published: May 2006

A complete analysis (8-spins) is given of the p.m.r. spectrum of aniline-15N, of the spectra of some haloanilines-15N and of 2-aminoacetophenone-15N. Intermolecular exchange of the amino protons is slow enough for observation of their spin–spin coupling to the ring protons. The magnitudes of the coupling constants between amino protons and 15N or ring protons are a measure of the geometry of the amino group. This is not true of the couplings between 15N and the ring protons. Long-range couplings computed in the CNDO/2 and INDO approximations of molecular orbital theory show points of agreement with experiment. For example, their signs and magnitudes are consistent with a nonplanar but not with a planar conformation of aniline. Couplings from 15N to ring protons are also computed for nitrobenzene.
A New Preparative Method of 1,6-Diketones from Fatty Acids and Vinylmagnesium Chloride
Authors: Watanabe Shoji , Suga Kyoichi , Fujita Tsutomu , Takahashi Yukio
Published: May 2006

The reaction of vinylmagnesium chloride with a fatty acid or its ester in the presence of cuprous chloride gives a 1,6-diketone. From n-valeric acid, n-tetradecane-5,10-dione is obtained in 53% yield. From methyl n-valerate, a mixture of n-tetradecane-5,10-dione (33%) and 5-oxo-1-nonene (34%) is obtained.
Pulse Radiolysis of Aqueous Papain
Authors: Clement J. R. , Armstrong D. A. , Klassen N. V. , Gillis H. A.
Published: May 2006

The pulse radiolysis of the proteolytic enzyme papain has been studied in nitrogen-purged and N2O-purged aqueous solutions at pH 6.4. The rate constant for reaction of OH with papain is 4.7 × 1010 M−1 s−1. The initial spectrum of the intermediate formed by this radical is consistent with a major fraction of attack at tyrosine residues with smaller proportions reacting at tryptophan and other sites. Subsequent spectral changes are also consistent with the preferential attack of OH on tyrosine. The overall rate constant for reaction of [Formula: see text] with papain is 4.1 × 1010 M−1 s−1 and the spectrum of the electron adduct closely resembles that of the disulfide anion [Formula: see text] However, there is evidence that not all reactions of [Formula: see text] with papain lead to the formation of this species. The results are discussed in the light of deactivation yields for Co60γ radiolysis measured by biochemical techniques.
An 129I Mössbauer Study of Novel Polyhalogen Ions Formed by Radioactive Decay in the Tellurium Halides
Authors: Johnstone J. J. , Jones C. H. W. , Vasudev P.
Published: May 2006

The 129I Mössbauer emission spectra of the compounds (NH4)2129mTeX6 and 129mTeX4 (X = Cl, Br, I) have been reported against a Na129I absorber at 4 °K. The spectra give evidence in the case of the (NH4)2TeX6 compounds for the formation in the radioactive decay of the octahedral ions [Formula: see text] [Formula: see text] and [Formula: see text] In the TeX4 compounds, the emission spectra are much more complex and indicate that the 129I atoms are not found in an environment iso-structural and iso-electronic with that of the parent.The 125Te Mössbauer absorption spectra of the parent compounds were studied to aid in their identification, and the parameters obtained are compared with those in the literature. The 125Te isomer shifts for the [Formula: see text] anions are interpreted in terms of pure p-bonding and, in conjunction with data from the emission spectra and data from previously reported n.q.r. work, an isomer shift vs. p-hole density relationship is established for tellurium.
Electron Spin Resonance Study of the Self-disproportionation of some Semiquinone Radicals in Solution
Authors: Wong S. K. , Sytnyk W. , Wan J. K. S.
Published: May 2006

The photolysis of 1,4-benzoquinone, duroquinone, and 1,4-naphthoquinone in isopropanol and in dioxane leads to the observation of e.s.r. spectra of the corresponding semiquinone radicals. The rates of the self-disproportionation of these radicals were measured by the rotating-sector technique. In the case of 1,4-naphthoquinone, unexpected e.s.r. emission was initially observed by photochemically induced dynamic electron polarization of the semiquinone radicals. Photolysis of anthraquinone in isopropanol gives e.s.r. spectra of the anthrasemiquinone radical anions. Their rate of decay was measured and a mechanism for the decay was suggested. The neutral anthrasemiquinone radical, however, was observed when photolyzed in dioxane.
Oriented Polycrystal Formation of Halogen-containing Organic Molecules on Alkali Halide Windows and their Usefulness in Vibrational Spectroscopic Studies
Authors: Katon J. E. , Sinha Deepali , Griffin M. G. , Condit D. A.
Published: May 2006

It has been found that several halogen-containing organic molecules normally crystallize as oriented polycrystals when in contact with alkali halide windows. This effect can lead to erroneous interpretation of crystal film spectra if it is not recognized, but can be very useful for determining molecular and/or crystal structures if the spectra are properly analyzed.
A General Relation Between H0, Acid Concentration, and Water Activity for Strong Acids at Moderate Concentrations
Authors: Teng T. T. , Lenzi F.
Published: May 2006

Values of the Hammett acidity function H0 can be correlated for strong acid solutions up to −H0 values of 3.5 via a Bascombe and Bell type equation:[Formula: see text] taking into account the degree of dissociation of the acids. This can be interpreted according to[Formula: see text]and[Formula: see text]Alternatively, an approach based on the treatment of equilibrium constants in terms of mole-fractions yields[Formula: see text]valid for the same acids (H2SO4, HClO4, HCl, and HNO3) and again involving a tri-dehydration of the tetra-hydrated proton. The log of the ratio [Formula: see text] has been found to be proportional to −H0 itself and to be otherwise independent of the nature of the acid anion.
On the Mobility of Quasifree Electrons in Liquid Methane
Authors: Fueki Kenji
Published: May 2006

A theoretical estimate has been made of the mobility and energy of quasifree electrons in liquid methane. It is shown that the calculated mobility is in agreement with the measured mobility and that the calculated energy is also consistent with a qualitative correlation between the mobility and energy of quasifree electrons in liquid alkanes.
Solvent Effects on the Phosphorescent State of Some Aromatic Carbonyls
Authors: Gallivan James B.
Published: May 2006

Triplet state properties of chromone, 4-chromanone, acetophenone, and several alkyl derivatives of acetophenone were studied in a variety of solvent systems. The phosphorescence excitation method was used to monitor the energies and relative intensities of singlet–triplet absorption bands in the presence and absence of heavy atom solvents. The results, combined with earlier optical and magnetic resonance studies of such systems, illustrate the importance of solvent environment in determining fundamental properties of these excited states. Observed trends are interpreted in terms of contrasting effects of changing solvent polarity on proximate n,π* and π.π* triplet states. To describe the relative contribution of each orbital type to the phosphorescent state, the coefficients of each wavefunction must change with solvent. Correspondingly, the solvent environment should be specified whenever orbital designations are made.
Lower Bounds to Expectation Values: Two-Electron Atoms
Authors: Chong D. P. , Weinhold F.
Published: May 2006

Weinhold's lower bound formulas are used on rather accurate wavefunctions for the 11S ground states of H−, He, and Li+, and the 21S and 23S excited states of He. The results are found to be of very high quality, as judged by comparison with the best available variational calculations, and can be used to rule out many of the values calculated by Scherr and Knight from high-order perturbation theory.
Isotope Effects on Chemical Equilibria. Part I. Some Secondary Isotope Effects of the Second Kind
Authors: Barnes D. J. , Scott J. M. W.
Published: May 2006

Secondary isotope effects Ka(H)/Ka(D) for the isotopic acid pairs 4-X-C6H4CH2COOH/4-X-C6H4-CD2COOH(X = H, NO2, OMe) have been determined at T = 25 °C by conductance measurements. This has involved the redetermination of the dissociation constants for the non-deuterated acids and in the case of X = NO2, OCH3, the new Ka values are to be preferred. The Ka of acetic acid has also been redetermined as a check on the reliability of the new data. The three isotope effects are shown to be much smaller than might have been anticipated on the basis of the e.m.f. measurements on the pair PhCH2COOH/PhCD2COOH reported earlier (1).
The Dissociation Constants and Conductivities of Mono-, Di- and Triethylamine in Aqueous Solution
Authors: Campbell Alan Newton , Lam Sing-Yeung
Published: May 2006

The conductances of the mono-, di-, and triethylamines, and their hydrochlorides, in aqueous solution, have been determined. Corrections for the formation of amine carbonates and hydrolysis of the halides were made. By using the Kohlrausch law and the method of Shedlovsky and Kay, basic dissociation constants for the amines have been computed. The basic strength of this series has been found to conform to the usual trend for other series of aliphatic amines.
Low Energy Electron Impact Ionization and Fragmentation: Cyclobutanone
Authors: Branton Graham Richard , Pua Claudio Kong Nam
Published: May 2006

Cyclobutanone is shown to yield both C3H6+ and C2H2O+ ions on fragmentation under electron impact in a mass spectrometer. Using the energy distribution difference (EDD) technique the ionization energy of cyclobutanone is found to be 9.58 eV and the appearance potentials of the C3H6+ and C2H2O+ ions are found to be 9.85 and 10.53 eV, respectively.
Photochemistry of Ketones in Carbon Tetrachloride Solution
Authors: Pavlik J. O. , Plooard P. I. , Somersall A. C. , Guillet J. E.
Published: May 2006

Acetone, chloroacetone, 4-heptanone, 8-pentadecanone, 12-tricosanone, and dimethyl γ-keto pimellate were photolyzed at 3130 Å in carbon tetrachloride solution. The quantum yields of C2Cl6 formed, the decrease in Norrish type I and type II products, the copious yields of HCl and the Stern–Volmer quenching of ketone fluorescence by carbon tetrachloride provide definitive evidence for energy transfer which is rationalized by an exciplex mechanism of low efficiency. The excited [n,π*]1 state of the ketone forms a loose complex with the CCl4 and radiationless energy transfer leads to dissociation of the CCl4 in the primary chemical step.
Micellar Effects upon p-n-Butylaniline Catalyzed Decarboxylation of Oxalacetic Acid
Authors: Lam Leo Ka-Ming , Schmidt Jr. Donald E.
Published: May 2006

p-n-Butylaniline ([nBA] = 1 × 10−3 M) incorporated in cationic micelles of cetyltrimethylammonium bromide ([CTABr] = 6 × 10−3M) was found to enhance the rate of decarboxylation of oxalacetic acid (OAA) 45-fold while nBA alone only increases the rate six-fold as compared to the rate of spontaneous decarboxylation at the same pH. Anionic micelles of sodium dodecyl sulfate ([SDS] = 6 × 10−3 M) completely inhibited the catalytic effect of nBA. Together with the effects of added salts and the change of pH on the rate of the reaction the role of micelles in the decarboxylation of OAA is discussed.
Laser-induced Transient Bleaching of Trapped Electrons in Alkali Halide Single Crystals
Authors: May Roger , Walker David C.
Published: May 2006

F-center electrons in KBr and KI crystals at room temperature are almost totally bleached during the intense light pulse from a Q-switched ruby laser. Recovery of the absorbance is largely complete within microseconds of the end of the pulse such that net loss of trapped electrons, which would result in permanent bleaching, is negligible (Φ < 10−2). Transient bleaching seems to result from both a loss of F-centers to form F′-centers and saturation of optical transitions for both the F and F′ bands. Comparisons of transient bleaching effects at 633, 1152, and 694 nm for KBr and KI strongly imply that the trapped electron absorption bands in crystals arise from single optical transitions which are homogeneously broadened. The rate at which the ground state of the F-center is repopulated following laser photolysis is of the order of 10−9 s and is very much slower than the analogous process in hydrated electrons. Results are also presented for additively colored and γ-induced F-centers and for F- and F′-centers bleached by ruby laser pulses at low temperatures.
Crystal and Molecular Structure of the Synthetic Intermediate, 2-Bromo-3-methoxy-5-hydroxy-5,6,7,8,9,10,13,14-octahydro-8-methyl-10,13-N-acetylaminomethano-phenanthrene, C19H24O3NBr
Authors: Lynton H. , Siew P. Y.
Published: May 2006

Crystals of the synthetic intermediate, 2-bromo-3-methoxy-5-hydroxy-5,6,7,8,9,10,13,14-octahydro-8-methyl-10,13-N-acetyl aminomethano-phenanthrene, C19H24O3NBr, are monoclinic, space group P21/n, unit cell dimensions a = 10.62(1), b = 14.47(2), c = 23.88(2) Å, β = 99.4(2)°, z = 8 with two molecules in the asymmetric unit. The structure was solved by the heavy atom method and refined by full matrix least squares to R = 0.096 for 2120 observed reflections. The conformation was found to be cis at the junction between rings A and B making further cyclization to obtain an A ring nitrogen bridge not possible.
Pulse Radiolysis of Alkali Metal Solutions in Ethylamine
Authors: Fletcher J. W. , Seddon W. A. , Sopchyshyn F. C.
Published: May 2006

Pulse radiolysis of solutions of alkali metal ethylamides in ethylamine shows the formation of three distinct species; the solvated electron es−, the alkali metal anion M−, and a species considered to be the cation–electron pair with stoichiometry M. The three species coexist in equilibrium in accord with the equations[Formula: see text]Studies of these solutions as a function of temperature, alkali metal concentration, and added complexing agents ("crown" compounds) show that es− and M have distinct absorption spectra with the former having a maximum ≥ 1800 nm. The latter exhibit maxima at 1400 nm for Na and K, ~1400 nm for Cs, and 1600–1700 nm for Li. The corresponding M− species were observed in sodium, potassium, and cesium solutions with absorption maxima at 680, 890, and 1100 nm, respectively.Rate and equilibrium constants for the formation of M and M− vary markedly with the nature of the alkali metal. Estimates for these constants along with the extinction coefficients for the various species are summarized and compared with data obtained in alkali metal solutions.
Correlation of Ionization Potentials and the Sums of Substituent Constants for Substituted Benzenes
Authors: Gibson Harry W.
Published: May 2006

Previously reported experimentally determined ionization potentials of substituted benzenes are well correlated by the sum of the para substituent constants, regardless of the orientation of the substituents. σ+ is better than σ for this purpose. Tri-through hexasubstituted benzenes are also correlated, but the slope and intercept are higher in accord with electrostatic theory. These results in support of recent MO calculations indicate that substituent constants are good measures of the energy of the highest occupied orbital.
The Low Temperature Oxidation of Humic Substances
Authors: Schnitzer Morris , Skinner Stewart I. M.
Published: May 2006

In attempts to uncover a relatively mild method for the oxidative degradation of humic substances, a humic and a fulvic acid were oxidized with peracetic acid at 40 °C for 8 days. The oxidation products were extracted into organic solvents, methylated, separated by column-, thin layer-, and preparative gas-chromatography, and identified by matching their mass and micro-i.r. spectra with those of authentic specimens.The major humic acid oxidation products were phenolic acids (isolated in fully methylated forms, 8.4%), benzenecarboxylic acids (as methyl esters, 16.0%), and aliphatic acids (as methyl esters, 3.4%). The fulvic acid yielded 11.5% phenolic compounds, 8.4% benzenecarboxylic acids (as methyl esters), and 2.6% aliphatic acids (as methyl esters). These data indicated a more phenolic character for the fulvic acid than for the humic acid. In addition, small amounts of 2-methyl-3,4-furandicarboxylic acid were tentatively identified as dimethyl esters among humic and fulvic acid oxidation products. As far as total yields of oxidation products were concerned, peracetic acid oxidation at 40 °C of untreated humic and fulvic acids compared favorably with permanganate oxidation of methylated humic materials at about 100 °C, but was more time consuming.The results of this and earlier oxidative degradation studies show that the oxidation of humic substances produces phenolic and benzenecarboxylic acids as major products in addition to smaller amounts of aliphatic dicarboxylic acids. Whether these products arise from more complex structures of lignin or microbial origin or whether they occur in the forms in which they were isolated but held together by hydrogen-bonding or Van der Waal's forces requires further investigation.
Homogeneous Catalysis of Hydrogen Isotope Exchange Between D2 and Ethanol by Chlorotris(triphenyIphosphine)rhodium(I). II. In Chloroform-Ethanol
Authors: Strathdee Graeme , Given Russell
Published: May 2006

The kinetics and mechanism of D2 exchange catalyzed by RhCl(PPh3)3 have been studied in chloroform–ethanol solutions. Interpretation of the results was complicated by a side reaction of the solvent to yield HCl, RhHCl2(PPh3)2, C2H5Cl, CH2Cl2, Ph3PO, and other phosphorus(V) species. Computer simulation of the exchange reaction was used to show that the observed inverse isotope effect [Formula: see text] could arise only if the rate determining step was the activation of D2, HD, and H2 by RhCl(PPh3)3.The D2 exchange reaction rate was extremely dependent on solvent composition and decreased 30 times between 6 and 96 mol% C2H5OH. The activation energy for D2 exchange was 101 ± 9 kJ mol−1 at 58 mol% C2H5OH, and 86 ± 8 kJ mol−1 at 6 mol% C2H5OH. These data suggested that solvent–catalyst bonding interactions were important.
Essai de calcul des paramètres d'anisotropic des liaisons C—C C—H, C=C et C=O par régression multi-linéaire sur des données expérimentales résonance magnétique nucléaire
Authors: ApSimon John W. , Elguero José , Fruchier Alain , Mathieu Didier , Phan-Tan-Luu Roger
Published: May 2006

A statistical treatment has allowed us to demonstrate the impossibility of calculating the magnetic susceptibilities and the anisotropies of the C—C and C—H bonds from the collection of chemical shifts reported by Simon and co-workers (22) as we have found the model of McConnell and the ApSimon to be inconsistent with experimental values.Nevertheless, we have been able to determine the values and confidence limits for the magnetic anisotropies of the C=C and C=O bonds and the electric field term for the C=O bond.
Spin-labelled Ligands
Authors: Cazianis C. T. , Eaton D. R.
Published: May 2006

A spin-labelled ligand is defined as a molecule with two functional groups, one of which provides a Lewis base site suitable for complexing to a metal ion. The second functional group comprises a site bearing an unpaired electron. The possible utility of such compounds in coordination chemistry has been explored. The spin density distribution in 4-pyridyl-t-butyl nitroxide provides information on the relative electron accepting abilities of different metal ions in various ligand environments. A method for measuring the rates of very rapid ligand exchange reactions is also suggested.
Crystal Structure of 1-(Bis-p-chlorophenyl)methylene-3-oxo-4,4-dimethyl-1,2-diazetidmium Hydroxide, Inner Salt, C17H14Cl2N2O
Authors: Calvo Crispin , Ip Po C. , Krishnamachari Narasimhan , Warkentin John
Published: May 2006

1(bis-p-Chlorophenyl)methylene-3-oxo-4,4-dimethyl-1,2-diazetidinium hydroxide, inner salt, C17H14Cl2N2O, crystallizes with orthorhombic symmetry, a = 9.95(1) Å, b = 28.73(2) Å, c = 11.30(1) Å, space group Pbca, Z = 8. The structure of this compound and its isostructural bromine analog were determined. The structure of the chloro-derivative was refined by full-matrix least-squares techniques using 1256 unique reflections to a final R of 0.099. The structure has a short intramolecular C—H … N bond (C … N distance = 2.891(11) Å). One of the phenyl rings is in the same plane as the 4-membered ring whereas the other ring lies in a plane almost perpendicular to this plane. The N—N distance in the heterocyclic ring is 1.415(10) Å, and the N—C distances in the ring are 1.535(11) and 1.377(11) Å. The molecular configuration is stabilized by both the short N … H interaction and delocalization between one of the phenyl groups and the diazetidinium ring.
Diverse Reactivity of N-Aryl-α-ureidoacetals on Catalysis by Molecular Sieves or Acids
Authors: Forrest T. P. , Dauphinee G. A. , Chen F. M. F.
Published: May 2006

The acid-catalyzed cyclocondensation of an N′-aryl-α-ureidoacetal (1), having a tetrasubstituted urea function, yields a 1,3-benzodiazepin-2-one (2), a quinazolinone (3), an oxazolidinone (7), or an arylaminoalcohol (6) depending upon conditions employed. Treatment of 1 with molecular sieves yields the cis and trans ureidoenolethers 4a and 4b. The N′-aryl-α-ureidoacetal 8 on treatment with molecular sieves undergoes intra- and inter-molecular condensations yielding the imidazolinones 9, 10, and 11. The thioureidoacetal 12 on treatment with molecular sieves yielded the thiazolines 13 and 14.
Protonation and Acid-catalyzed Rearrangement of 1,2-Diazepines
Authors: Harris David John , Thomas M. T. , Snieckus Victor , Klingsberg E.
Published: May 2006

The protonation of the 1,2(4H)-diazepines 2a, 2b, and the 1,2(1H)-diazepine 3a in various acidic media has been studied by u.v. and n.m.r. spectroscopy. Compounds 2a and 3a undergo protonation to give 4a and 7a, respectively, whereas 2b provides the monoprotonated species 4b in dilute acid and the diprotonated form 4c in strongly acidic solution. Spectral characteristics of crystalline 1,2(4H)-diazepinium perchlorates 4a, 4d, 7a, and 7c correlate well with those observed for the corresponding free bases in acidic solutions; 7a-ClO4 and 7c-ClO4 were obtained either from 2a and 2c or from 3a and 3c, respectively. In trifluoroacetic acid-d-D2O, deuterium exchange at C4 and C6 of 2a, 2b, and 3a was observed indicating the presence of small equilibrium concentrations of species 1a, 1c and/or 1d, and 1b under these conditions. Temperature variable n.m.r. spectroscopy provides evidence for ring inversion phenomena for the protonated forms 4a and 7a. In the case of 4a, the activation energy, ΔGc≠ = 10.2 ± 0.2 kcal/mol (Tc = 8 ± 3°) has been estimated. The difference in the activation energy between the free base and the protonated form, ΔG≠ (2a)—ΔG≠ (4a) = 6–7 kcal/mol is attributed to strong repulsive N1—N2 lone pair interaction in 2a in the transition state for the ring inversion process.Under vigorous acidic conditions, the 1, 2(4H)-diazepines 2a–c give pyrazoles (10a–c), pyridines (12a–c), and acetophenone. Using identical conditions, the 1,2(4H)-diazepinium salt, 7a-ClO4 provides pyrazole 11a and pyridine 12a and, in addition, the 1-methylaminopyridinium salt 13a. However, rearrangement also proceeds under very mild conditions (ethanol–water) as shown for 7a-ClO4 and 7c-ClO4 which yield compounds 11a and 12a, and 11c, 12c, and 13c, respectively. The 1, 2(1H)-diazepine 3a gives 11a, 12a, and 13a in ethanol–water solution and exclusively 13a in trifluoroacetic acid. The mechanism of these reactions is discussed in terms of formation of open-chain (15) and diaziridine-type (19) intermediates. Electrocylic mechanisms are eliminated from consideration on the basis of the absence of products 23, 24, and 25 which should have been observed from the reactions of 2b, 2c, and 7c-ClO4 if these pathways were operative.
The Carbon-13 Magnetic Resonance Spectrum of Propane
Authors: Wasylishen Roderick E. , Schaefer Ted
Published: May 2006

The carbon-13 magnetic resonance spectra of propane and of propane-2,2-d2 are analyzed to give 1j(13C1,H) = 124.35, 1J(13C2,H) = 125.35, 2J(13C1,H) = −4.25, 2J(13C2,H) = −4.39, 3J(13C,H) = 5.80, 3J(H,H) = 7.375, 4j(H,H) < ± 0.18 Hz. The deuterium isotope shift at C2 is 0.72 ± 0.10 p.p.m. to high field.
Nonaromatic Primary Amine Tropolone Salts
Authors: Poh Bo Long
Published: May 2006

Nonaromatic primary amines react rapidly with tropolone in nonpolar solvents such as carbon tetrachloride and benzene to give quantitative yields of the corresponding amine tropolone salts which when reacted with aqueous base give back tropolone and the original amines.The reaction between nonaromatic primary amines and tropolone provides a convenient method of detecting and separating nonaromatic primary amines from other amines.
The Proton Magnetic Resonance Spectrum of p-Methylbenzylbromide, Conformational Preference of the Bromomethyl Rotor
Authors: Chum Kalvin , Rowbotham J. Brian , Schaefer Ted
Published: May 2006

A complete analysis is given of the nine-spinproton magnetic resonance spectrum of p-methylbenzyl bromide as a 20 mol% solution in acetone-d6 The long-range coupling constants between methyl and ring protons are the same as those in toluene. The coupling constants between the methylene protons and the other protons in the molecule are consistent with a two-fold barrier of 500 ± 200 cal/mol for the bromomethyl group, the preferred conformation having the C—Br bond in a plane perpendicular to the aromatic plane. An alternative model, in which a C—H bond of the bromomethyl rotor prefers the aromatic plane to the extent of 3 kcal/mol, is considered unlikely.
Cobalt-59 Neclear Quadrupole Resonance Studies on Five-coordinate Cobalt Complexes
Authors: Chia Lian Sai , Cullen William R. , Gerry Michael C. L.
Published: May 2006

The n.q.r. spectra of a number of complexes of the type [Y3PCo(CO)3]2 have been recorded. The results are compared with those from related studies.
Fluorescence différée et émissions photostimulées du carbazole et de la diphénylamine dans une matrice rigide d'éther à 77 °K
Authors: Muller D. , Ewald M. , Durocher G.
Published: May 2006

The isothermal delayed fluorescence along with the visible (6000 Å) photostimulated fluorescence and phosphorescence emissions have been recorded and analyzed in the following systems: diphénylamine (DPA) – ether rigid glass and carbazole (C) – ether rigid glass at 77°K. The electron–cation recombination after visible light stimulation has been analyzed in terms of a kinetic model already described (10). The triplet quantum yields of the DPA and C molecules are calculated and compared to the existing experimental values. The rate constant ratio (β) of populating the first triplet (T1) relative to populating the first excited singlet (S1) after the recombination event has taken place, is equal to about 2 in both systems investigated here. A value of 4.4 was obtained for indole and tryptophan in the same matrix. This difference can only be explained in terms of various singlet state energies for these molecules and also in terms of the stimulating energies used in these experiments.
Laser Spectrofluorimetry of Chlorophylls
Authors: Leblanc Roger M. , Galinier Geneviève , Tessier Alain , Lemieux Lise
Published: May 2006

A device has been set up to determine quantitatively the weak fluorescence intensities of pigment molecules. It consists of a laser spectrofluorimeter. The excitation beam can be produced with either a He/Cd laser (441.6 nm) or a He/Ne laser (632.8 nm). This system allows us to detect the fluorescence of dilute chlorophyll a or b solutions of the order of 10−12 mol/l. This sensitivity also permits the study of the emission spectra from chlorophyll in monomolecular or solid states, and since a polarization rotator has been incorporated into our apparatus, one may presume some possible orientation of the molecules.
Sur le spectre électronique de l'ion ozonide, 03−
Authors: Giguère Paul A. , Herman Kazimiera
Published: May 2006

Potassium ozonide dissolved in liquid ammonia absorbs fairly strongly in the u.v. from 300 nm, in addition to the strong band in the violet–blue. Previous conflicting results were due to interference of other species, such as O3, O2−, and HO2, which also absorb in that region. The irregular spacing of the maxima in the visible band points to some interference of a second vibrational mode of the upper state.
Pyrazolo[1,5-a]Pyrimidine: Synthesis and Regiospecific Electrophilic Substitution in the Pyrazole and/or Pyrimidine Rings
Authors: Lynch Brian Maurice , Khan Misbahul Ain , Sharma Suresh Chandra , Teo Huk Chia
Published: May 2006

A general cyclization route to pyrazolo[1,5-a]pyrimidines from 3-aminopyrazole and 1,3-dicarbonyl compounds is applied to synthesis of the parent ring system. In nitration of this species the orientation of substitution is strongly reagent dependent. Mixed nitric and sulfuric acids yield the 3-nitro compound, whereas nitric acid in acetic anhydride yields the 6-nitro compound. Brominations yield 3-bromo and 3,6-dibromo species.The majority reacting species in the strongly acidic medium is identified as the 1-protonated entity by conjoint use of approximate molecular orbital calculations and the variation of coupling constant patterns accompanying protonation. The molecular orbital calculations predict successive 3- and 6-substitution by electrophiles in pyrazolo[l,5-a]pyrimidine and its conjugate acid, and an addition–elimination sequence is proposed to account for the observed 6-nitration.
A New Method for Determining Individual Rate Constants for Specific Non-chromophoric Substrates of Proteolytic Enzymes
Authors: Brubacher Lewis J.
Published: May 2006

Equations are developed for the pre-steady state kinetics of the proteolytic enzyme-catalyzed hydrolysis of a substrate A in the presence of a monitoring substrate (or covalent inhibitor) S of known properties. A two-intermediate acyl–enzyme mechanism is assumed in which the first intermediate is in instantaneous equilibrium with enzyme and substrate. The appearance of the first product of substrate S is characterized by two relaxation rate constants. From these constants it is possible to determine the dissociation constant and the acylation and deacylation rate constants of substrate A. Criteria are also developed for using the steady state rate parameters of A to establish conditions for which the slower relaxation process is equivalent to the deacylation rate constant of A. The technique of premixing enzyme with substrate A has certain advantages in this approach.
1H, 13C, 14N, 19F Nuclear Magnetic Resonance Contact Shifts and Electron Spin Distribution in Aniline and Fluoroanilines – Ni(II) Acetylacetonate Complexes
Authors: Chachaty C. , Forchioni A. , Virlet J.
Published: May 2006

The contact shifts of 1H, 13C, 14N, and 19F in chloroform solutions of Ni(II) acetylacetonate -aniline and fluoraniline complexes have been studied by high resolution n.m.r. The unpaired electron spin distribution in these ligands is compared to that calculated by the INDO method for the corresponding aniline cation radicals. The ratio of the hyperfine coupling constants aNHH/aN suggests that in these aniline complexes the [Formula: see text] fragment is pyramidal with an angle of 13–15° between the perpendicular of the C—N bond and the axis of the p like orbital centered on nitrogen. The electron spin distribution between the NH2 group and the phenyl ring may be partially accounted for by assuming an internal rotation about the C—N bond. The 13C relaxation indicates a N—Ni distance of the order of 2 Å for aniline and 2 fluoraniline complexes and an electron spin-lattice relaxation time of ∼5 × 10−10 s at 300 °K.
Perchlorato, Nitrato, and Acetylacetonato Complexes of Copper(I). The Crystal and Molecular Structure of Perchloratobis(tricyclohexyiphosphine)Copper(I)
Authors: Restivo Roderic J. , Costin Abraham , Ferguson George , Carty Arthur J.
Published: May 2006

Copper(I) perchlorate, nitrate, and acetylacetonate complexes of the types Cu(triphos)ClO4 (triphos = CH3C(CH2PPh2)3), Cu(Cy3P)2ClO4 (Cy3P = P(C6H11)3), Cu(triphos)NO3, Cu(Cy3P)2(HFac)(HFac = hexafluoroacetylacetonate), and Cu (Cy3P)2(TtFac) (TtFac = thienyltrifluoroacetylacetonate) have been synthesized by reduction of the corresponding perchlorate, nitrate, and acetylacetonates with tertiary phosphines. Infrared spectra indicate the presence of monodentate perchlorate groups in Cu(triphos)ClO4 and in Cu(Cy3P)2ClO4 and the crystal structure of the latter has been determined by a three-dimensional X-ray analysis using diffractometer data. The crystals are monoclinic, space group C2/c, with cell dimensions a = 18.159(6), b = 9.493(2), c = 22.182(3) Å, and β = 95.41(2)° and four molecules per unit cell. The structure was refined by block-diagonal least squares methods to a final R of 0.051 for 2617 reflections using anisotropic thermal parameters for the nonhydrogen atoms. The structure consists of discrete Cu(Cy3P)2ClO4 molecules with symmetry C2 separated by normal van der Waals distances. The copper atom is three-coordinate and the perchlorate anion is monodentate but disordered over two sites. Principal dimensions include: Cu—P 2.262(1) Å, Cu—O 2.220(7) Å, [Formula: see text][Formula: see text] and 99.8(2)°, and [Formula: see text]
Stéréochimie de l'addition homolytique de l'acide thioacétique a des dérivés méthylènes cyclohexaniques
Authors: Richer Jean-Claude , Lamarre Claude
Published: May 2006

The stereochemistry of the homolytic addition of thioacetic acid to 4-tert-butyl-2,2-dimethyl-1-methylenecyclohexane, to 3,3,5-trimethyl-1-methylenecyclohexane, to β -pinene and, for comparison purposes, to 4-tert-butyl-1-methylenecyclohexane has been examined. The results obtained during this study are compared to those obtained from the reduction of the corresponding ketones by LiAlH4. [Journal translation]
Apparent Molal Volumes and Heat Capacities of Tetrabutylammonium Bromide in Aqueous Electrolyte Solutions
Authors: Desrosiers Nicole , Desnoyers Jacques E.
Published: May 2006

The apparent molal volumes and heat capacities of Bu4NBr were measured in aqueous solutions of NaF, NaCl, NaBr, KBr, NaAc, and NH4Ac at 25 °C with a flow densimeter and a flow microcalorimeter. The derived transfer functions of Bu4NBr from water to the electrolyte solutions, after correction for the long-range coulombic forces, are all negative. This suggests that the noncoulombic interactions between hydrophobic and hydrophilic ions result in negative contributions to volumes and heat capacities.
Derivatives of 2-Pyrazolin-5-one. II. Catalyzed Sodium Borohydride Reduction of Some 4–(2-Nitrobenzylidene)-2-pyrazolin-5-ones. A Reappraisal
Authors: Coutts Ronald T. , El-Hawari Abdel-Monaem
Published: May 2006

A reexamination of the sodium borohydride and palladium–charcoal reduction of 3-methyl-4-(o-nitrobenzylidene)-1-phenyl-2-pyrazolin-5-one (3a) has revealed that the final product is 3-methyl-4-(o-aminobenzyl)-1-phenyl-2-pyrazolin-5-one (5a), and not 9-hydroxy-3-methyl-3a,4,9,9a-tetrahydro-1H-pyrazolo[3,4-b]quinoline as claimed previously. Reduction of 3a to 5a proceeds via the 4-(o-nitrobenzyl) compound. Chemical and physical properties of 5a are described which support the assignment of this revised structure to the reduction product of 3a. Two analogs of 3a were also reduced in the same manner and yielded products analogous to 5a and not the previously claimed pyrazolo[3,4-b]quinolines.
MyD88 and NOS2 are essential for Toll-like receptor 4-mediated survival effect in cardiomyocytes
Authors: Zhu Xinsheng , Zhao Huailong , Graveline Amanda R. , Buys Emmanuel S. , Schmidt Ulrich , Bloch Kenneth D. , Rosenzweig Anthony , Chao Wei
Published: April 2006

Innate immune system such as Toll-like receptor 4 (TLR4) represents the first line of defense against infection. In addition to its pivotal role in host immunity, recent studies have suggested that TLR4 may play a broader role in mediating tissue inflammation and cell survival in response to noninfectious injury. We and other investigators have reported that cardiac TLR4 signaling is dynamically modulated in ischemic myocardium and that activation of TLR4 confers a survival benefit in the heart and in isolated cardiomyocytes. However, the signaling pathways leading to these effects are not completely understood. Here, we investigate the role of MyD88, an adaptor protein of TLR4 signaling, and inducible nitric oxide synthase (NOS2) in mediating TLR4-induced cardiomyocyte survival in an in vitro model of apoptosis. Serum deprivation induced a significant increase in the number of apoptotic cardiomyocytes as demonstrated by transferase-mediated dUTP nick-end labeling (TUNEL) assay, nuclear morphology, DNA laddering, and DNA-histone ELISA. Lipopolysaccharide (LPS), a TLR4 agonist, activated TLR4 signaling and led to significant reduction in apoptotic cardiomyocytes and improved cellular function of surviving cardiomyocytes with enhanced Ca2+transients and cell shortening. We found that both TLR4 and MyD88 are required for the LPS-induced beneficial effects as demonstrated by improved survival and function in wild-type but not in TLR4−/−or MyD88−/−cardiomyocytes. Moreover, genetic deletion or pharmacological inhibition of NOS2 abolished survival and functional rescue of cardiomyocytes treated with LPS. Taken together, these data suggest that TLR4 protects cardiomyocytes from stress-induced injury through MyD88- and NOS2-dependent mechanisms.
Acute vascular responses to isometric handgrip exercise and effects of training in persons medicated for hypertension
Authors: McGowan Cheri L. , Levy Andrew S. , Millar Philip J. , Guzman Juan C. , Morillo Carlos A. , McCartney Neil , MacDonald Maureen J.
Published: April 2006

Previous work from our laboratory demonstrated that isometric handgrip (IHG) training improved local, endothelium-dependent vasodilation in medicated hypertensives [McGowan CL (PhD Thesis), 2006; McGowan et al. Physiologist 47: 285, 2004]. We investigated whether changes in the capacity of smooth muscle to dilate (regardless of endothelial factors) influenced this training-induced change, and we examined the acute vascular responses to a single bout of IHG. Seventeen subjects performed four 2-min unilateral IHG contractions at 30% of maximal voluntary effort, three times a week for 8 wk. Pre- and posttraining, brachial artery flow-mediated dilation (FMD, an index of endothelium-dependent vasodilation) and nitroglycerin-mediated maximal vasodilation (an index of endothelium-independent vasodilation) were measured in the exercised arm by using ultrasound before and immediately after acute IHG exercise. IHG training resulted in improved resting brachial FMD ( P < 0.01) and no change in nitroglycerin-mediated maximal vasodilation. Pre- and posttraining, brachial artery FMD decreased following an acute bout of IHG exercise (normalized to peak shear rate, pre-, before IHG exercise: 0.01 ± 0.002, after IHG exercise: 0.008 ± 0.002%/s−1; post-, before IHG exercise: 0.020 ± 0.003, after IHG exercise: 0.010 ± 0.003%/s−1; P < 0.01). Posttraining, resting brachial artery FMD improved yet nitroglycerin-mediated maximal vasodilation was unchanged in persons medicated for hypertension. This suggests that the training-induced improvements in the resting brachial artery FMD were not due to underlying changes in the forearm vasculature. Acute IHG exercise attenuated brachial artery FMD, and although this impairment may be interpreted as hazardous to medicated hypertensives with already dysfunctional endothelium, the effects appear transient as repeated exposure to the IHG stimulus improved resting endothelium-dependent vasodilation.
T wave alternans in an in vitro canine tissue model of Brugada syndrome
Authors: Morita Hiroshi , Zipes Douglas P. , Lopshire John , Morita Shiho T. , Wu Jiashin
Published: April 2006

Macroscopic T wave alternans (TWA) associated with increased occurrence of ventricular arrhythmias has been reported in patients with Brugada syndrome. However, the mechanisms in this syndrome are still unclear. We evaluated the hypothesis that TWA in Brugada syndrome was caused by the dynamic instability and heterogeneity of action potentials (APs) in the right ventricle. Using an optical mapping system, we mapped APs on the epicardium or transmural surfaces of 28 isolated and arterially perfused canine right ventricular preparations having drug-induced Brugada syndrome (in μmol/l: 2.5–15 pinacidil, 5.0 terfenadine, and 5.0–13 pilsicainide). Bradycardia at cycle length (CL) of 2,632 ± 496 ms ( n = 19) induced alternating deep and shallow T waves in the transmural electrocardiogram. Compared with the shallow T waves, deep T waves were associated with epicardial APs having longer durations and larger domes. Adjacent regions having APs with alternating domes, with constant domes, and without domes coexisted simultaneously in the epicardium and caused TWA. In contrast to the alternating epicardial APs, midmyocardial and endocardial APs did not change during TWA. Alternans could be terminated by rapid (CL: 529 ± 168 ms, n = 7) or very slow (CL: 3,000 ms, n = 7) pacing. The heterogeneic APs during TWA augmented the dispersion of repolarization both within the epicardium and from the epicardium to the endocardium and caused phase 2 reentry. In this drug-induced model of Brugada syndrome, heterogeneic AP contours and dynamic alternans in the dome of right ventricular epicardial, but not midmyocardial or endocardial, APs caused TWA and heightened arrhythmogenicity in part by increasing the dispersion of repolarization.
Enhanced calcium mobilization in rat ventricular myocytes during the onset of pressure overload-induced hypertrophy
Authors: Carvalho Beatriz M. R. , Bassani Rosana A. , Franchini Kleber G. , Bassani José W. M.
Published: April 2006

Early cardiovascular changes evoked by pressure overload (PO) may reveal adaptive strategies that allow immediate survival to the increased hemodynamic load. In this study, systolic and diastolic Ca2+cycling was analyzed in left ventricular rat myocytes before ( day 2, PO-2d group) and after ( day 7, PO-7d group) development of hypertrophy subsequent to aortic constriction, as well as in myocytes from time-matched sham-operated rats (sham group). Ca2+transient amplitude was significantly augmented in the PO-2d group. In the PO-7d group, intracellular Ca2+concentration ([Ca2+]i) was reduced during diastole, and mechanical twitch relaxation (but not [Ca2+]idecline) was slowed. In PO groups, fractional sarcoplasmic reticulum (SR) Ca2+release at a twitch, SR Ca2+content, SR Ca2+loss during diastole, and SR-dependent integrated Ca2+flux during twitch relaxation were significantly greater than in sham-operated groups, whereas the relaxation-associated Ca2+flux carried by the Na+/Ca2+exchanger was not significantly changed. In the PO-7d group, mRNA levels of cardiac isoforms of SR Ca2+-ATPase (SERCA2a), phospholamban, calsequestrin, ryanodine receptor, and NCX were not significantly altered, but the SERCA2a-to-phospholamban ratio was increased 2.5-fold. Moreover, greater sensitivity to the inotropic effects of the β-adrenoceptor agonist isoproterenol was observed in the PO-7d group. The results indicate enhanced Ca2+cycling between SR and cytosol early after PO imposition, even before hypertrophy development. Increase in SR Ca2+uptake may contribute to enhancement of excitation-contraction coupling (augmented SR Ca2+content and release) and protection against arrhythmogenesis due to buildup of [Ca2+]iduring diastole.
Neurotrophin effects on intracellular Ca2+and force in airway smooth muscle
Authors: Prakash Y. S. , Iyanoye Adeyemi , Ay Binnaz , Mantilla Carlos B. , Pabelick Christina M.
Published: April 2006

Neurotrophins [e.g., brain-derived neurotrophic factor (BDNF), neurotrophin 4 (NT4)], known to affect neuronal structure and function, are expressed in nonneuronal tissues including the airway. However, their function is unclear. We examined the effect of acute vs. prolonged neurotrophin exposure on regulation of airway smooth muscle (ASM) intracellular Ca2+concentration ([Ca2+]i): sarcoplasmic reticulum (SR) Ca2+release and Ca2+influx (specifically store-operated Ca2+entry, SOCE). Human ASM cells were incubated for 30 min in medium (control) or 1 or 10 nM BDNF, NT3, or NT4 (acute exposure) or overnight in 1 nM BDNF, NT3, or NT4 (prolonged exposure) and imaged after loading with the Ca2+indicator fura-2 AM. [Ca2+]iresponses to ACh, histamine, bradykinin, and caffeine and SOCE following SR Ca2+depletion were compared across cell groups. Force measurements were performed in human bronchial strips exposed to neurotrophins. Basal [Ca2+]i, peak responses to all agonists, SOCE, and force responses to ACh and histamine were all significantly enhanced by both acute and prolonged BDNF exposure (smaller effect of NT4) but decreased by NT3. Inhibition of the BDNF/NT4 receptor trkB by K252a prevented enhancement of [Ca2+]iresponses. ASM cells showed positive immunostaining for BDNF, NT3, NT4, trkB, and trkC (NT3 receptor). These novel data demonstrate that neurotrophins influence ASM [Ca2+]iand force regulation and suggest a potential role for neurotrophins in airway diseases.