bluuebunny/crossref_metadata_2025 huggingface dataset:
Occurrence of the Enterotoxin Gene Cluster and the Toxic Shock Syndrome Toxin 1 Gene among Clinical Isolates of Methicillin-Resistant
Staphylococcus aureus
Is Related to Clonal Type and
agr
Group
Authors: Chini Vassiliki , Dimitracopoulos George , Spiliopoulou Iris
Published: May 2006

Analysis of 177 methicillin-resistant
Staphylococcus aureus
(MRSA) strains for the presence of
egc
and
tst
revealed that 60 strains carried at least one of the tested genes. MRSA strains were classified by pulsed-field gel electrophoresis into four clones belonging to
agr
groups I and III. Toxin genotypes were related by clonal type and
agr
group.
Rapid
Staphylococcus aureus agr
Type Determination by a Novel Multiplex Real-Time Quantitative PCR Assay
Authors: Francois Patrice , Koessler Thibaud , Huyghe Antoine , Harbarth Stephan , Bento Manuela , Lew Daniel , Etienne Jérôme , Pittet Didier , Schrenzel Jacques
Published: May 2006

The accessory gene regulator (
agr
) is a crucial regulatory component of
Staphylococcus aureus
involved in the control of bacterial virulence factor expression. We developed a real-time multiplex quantitative PCR assay for the rapid determination of
S. aureus agr
type. This assay represents a rapid and affordable alternative to sequence-based strategies for assessing relevant epidemiological information.
Synthesis of 3-(1,1-ethylenedioxyoctyl)-cyclopentanone
Authors: Orr D. E. , Johnson F. B.
Published: May 2006

1,4-Cyclohexanedione has been converted into compounds 8 and 9. Treatment of 8 and 9 with base produces compound 10, which has been converted into 3-(1,1-ethylenedioxyoctyl)-cyclopentanone.
Cyclizations of dialdehydes with nitromethane. XIV. The isolation of four crystalline methyl 3,6-dideoxy-3-nitro-α-L-hexopyranosides
Authors: Baer Hans H. , Čapek Karel
Published: May 2006

Cyclization of L′-methoxy-L-methyldiglycolic aldehyde (1) with nitromethane and sodium methoxide in methanol (40 min at room temperature) furnished four crystalline methyl 3,6-dideoxy-3-nitro-α-L-hexopyranosides in a combined yield of 75%. Chromatographic separation gave the gluco (2), manno (3), talo (4), and galacto (5) isomers in an approximate ratio of 18:8:3:1. Shortening of the reaction time to 25 min decreased the total yield to 53% at the expense of 2, the ratio of isolated products being 8:8:2.3:1.7. The configurations of the new nitro glycosides 3, 4, and 5 were proven by catalytic hydrogenation followed by N-acetylation, which gave the known 3-acetamido derivatives.
A quantum mechanical study of proton exchange in sulfoxides with retention and inversion of configuration
Authors: Rauk Arvi , Wolfe Saul , Csizmadia I. G.
Published: May 2006

A survey of the experimental data on the structures of α-sulfonyl and α-sulfinyl carbanions is presented as an introduction to the present work, a theoretical study of hydrogen methyl sulfoxide (HMSO) and hydrogen methylsulfinyl anion (HMSO−) by nonempirical self consistent field (s.c.f.) calculations using Gaussian basis sets. Calculations on dimethyl sulfoxide (DMSO) and its conjugate base (DMSO−) are also presented and fully justify the choice of HMSO and HMSO− for the detailed work. A conformational energy surface (total energy as a function of rotation about the C—S bond and inversion of the carbanion angle) for HMSO− is presented and used to determine the stereochemical fate of a carbanion generated next to a sulfinyl group. Predictions are made concerning the probable course of proton exchange next to S—O and an explanation is offered for the experimental facts concerning exchange in sulfoxides. A very significant finding is that postulation of d-orbital conjugation is not essential to explain the asymmetry of α-sulfinyl carbanions.
A thermochemical study of addition complexes of zirconium and hafnium tetrahalides
Authors: Chung Fine Man , Westland Alan D.
Published: May 2006

Enthalpies of addition were determined calorimetrically for the crystalline complexes MX4•2L where M = Zr or Hf, X = Cl or Br, and L = tetrahydrofuran or tetrahydrothiophene. With oxygen as the donor atom of L, the two metalhalides exhibited nearly identical acceptor power but with sulfur as donor, HfCl4 proved to be the better acceptor. Hafnium(IV) shows more class b character than zirconium(IV).
Infrared spectra of trans-1,2-diphenylethylene and trans-1,2-diphenylethylene-d12
Authors: Pecile Cesare , Lunelli Bruno
Published: May 2006

The location of the infrared active fundamentals of trans-1,2-diphenylethylene and trans-1,2-diphenyl-ethylene-d12 are discussed on the evidence given by the absorption spectra measured in the 4000–33 cm−1 region for solid and solution samples. This assignment is consistent with that reported in the preceding article for diphenylethine and fits the correlative scheme offered by the monosubstituted benzenes in the case of the light as well as of the heavy compound.The polarized spectra of single crystals, (001) crystal plane, allowed examination of the dichroic behavior of the bands corresponding to planar vibrations for which no prediction is possible on the basis of the overall C2h symmetry. The local symmetry C2v of the aromatic fragment is not observed to prevail in such a complete and satisfactory way as to indicate the presence of an empirical polarization specificity, even though to some extent, particularly in the case of the a1 modes of the phenyl ring, there is coincidence between the polarization observed and that predicted on the basis of the local symmetry.
Basic dissociation constant for ethylamine by a convenient conductance method
Authors: Linde W. Van Der , Northcott D. , Redmond W. , Robertson R. E.
Published: May 2006

A dilution technique is described which permits a determination of the ionization constant of amines by a conductance method, in a closed system. Small amounts (5–6 g) of the amine salt are required, making the method useful in studying isotope effects. Values of Ki for ethylamine over the temperature range 1.5–45.3 °C led to calculated values at 25 °C of ΔG = 4528.3 ± 0.8 cal/mole, ΔH = −266 ± 12 cal/mole, ΔS = −16.08 ± 0.04 cal/mole deg, ΔCp = −62.2 ± 1.8 cal/mole deg.
Photochemical decomposition of methanethiol. II. The wavelength dependence of the hydrogen atom energy
Authors: White John M. , Sturm Jr G. P.
Published: May 2006

Data are presented which indicate that the energy distribution of the hydrogen atom produced in the photolysis of methanethiol varies with wavelength in the region 2288 to 2537 Å.
Some aspects of the formation of hex-2-enopyranosides from methyl 2,3-di-O-methanesulfonyl-α-D-glucopyranosides
Authors: Fraser-Reid Bert , Boctor Bahya
Published: May 2006

The elimination of vicinal sulfonyloxy groups from methyl 2,3-di-O-methanesulfonyl-α-D-glucopyranosides with the formation of hex-2-enopyranosides using potassium iodide, and zinc in refluxing dry dimethyl formamide has been investigated. The specific use of a zinc–copper couple has been found to be highly advantageous to the yield and reproducibility of the reaction, and the elimination proceeds successfully whether acid or base labile groups are present at carbon-4 or -6. Both the 4,6-di-O-benzoyl (3b) and the 6-O-benzoyl (3d) precursors give methyl 6-O-benzoyl-α-D-erythro-hex-2-enopyranoside (4d) as the major product, the latter also being obtainable by selective benzoylation of methyl α-D-erythro-hex-2-enopyranoside (4c). The reaction of the dibenzoate therefore occurs with some deacylation at carbon-4, but it is noteworthy that this is not accompanied by any epimerization. A similar pattern of reaction apparently occurs with the 4,6-di-O-acetyl derivative (3a). The conformations of the starting di-O-methanesulfonyl esters are discussed and suggestions for the n.m.r. assignments of the groups are made.
The total synthesis of optically active annotinine
Authors: Wiesner K. , Poon Lizzie , Jirkovský I. , Fishman M.
Published: May 2006

The total synthesis of the first Lycopodium alkaloid annotinine in the optically active form is described. The key step in this synthesis was the photochemical addition of allene to the tricyclic vinylogous imide (3) which yielded the photoadduct (6).
Kinetics of the thermal decomposition of cyclobutanone
Authors: Blades Arthur T.
Published: May 2006

The thermal decomposition of cyclobutanone into cyclopropane and carbon monoxide has been shown to occur simultaneously with the major decomposition to ethylene and ketene. The relative rate constant expression is given by [Formula: see text] Both reactions are pressure sensitive below 10 Torr and this quasi-unimolecular behavior is most pronounced in the cyclopropane forming reaction, consistent with the higher activation energy. The data are also discussed in relation to the photochemical decomposition and it is shown that cyclopropane formation from the ground singlet is an important feature of the photolysis at 3130 Å.
Recoil studies of some light-mass products from the proton-induced fission of 238U at intermediate energies
Authors: Saha G. B. , Yaffe L.
Published: May 2006

The recoil properties of 66Ni, 67Cu, and 72Zn produced in the fission of 238U by protons of 40–85 MeV energy have been studied radiochemically by the thick target – thick catcher technique. The average kinetic energy of each product has been calculated from the ranges by use of known range–energy relationships. The calculated impact velocity vll shows that these fission products are formed predominantly via a compound nucleus mechanism in this energy region. The average total kinetic release in fission is found to be insensitive to the bombarding energy.
Determination of the bond dissociation energy, D(CH3Hg—CH3), by the toluene carrier method
Authors: Kominar R. J. , Price S. J.
Published: May 2006

The thermal decomposition of Hg(CH3)2 has been studied in a toluene carrier flow system over the pressure range 4.5 to 323 mm at temperatures of 422 to 527 °C. The Arrhenius equation for the pressure independent region,[Formula: see text]is in excellent agreement with earlier work on the fully inhibited decomposition at lower temperatures. The region of fall off of the unimolecular rate constant is in agreement with a classical Kassel calculation using s = 16−18, but the rate of fall off requires the use of a curve with s = 3, displaced five log units to the left. This is consistent with the previous results for the dissociation of ethane into two methyl radicals and is further evidence of the inability of the classical Kassel equation to represent the behavior of systems with high pre-exponential factors.
Gas phase photochlorination of perfluorocyclohexene
Authors: Cosa J. J. , Vallana C. A. , Staricco E. H.
Published: May 2006

The kinetics of the gas phase photochemical reaction between perfluorocyclohexene and chlorine was studied between 10 and 50 °C. The system was irradiated with light of 4360 Å. The rate of the photochlorination was independent of the perfluorocyclohexene pressure and of the total pressure. It was found to be proportional to the first power of the pressure of Cl2 and to the square root of the intensity of absorbed light. At 30 °C, the quantum yield was found to be 200 when the initial Cl2 pressure was 100 Torr, and intensity of light absorbed 9.89 × 10−9 einstein l−1s−1.An activation energy of 5.1 kcal/mole could be assigned to the reaction C6F10Cl + Cl2.
Acetoacetyl pyrroles and their boron complexes
Authors: Roomi M. W.
Published: May 2006

Various boron complexes of acetoacetyl pyrrole have been synthesized and their nuclear magnetic resonance and infrared spectra showed that the complexes formed are six member chelate.
Synthesis of isomers of acetylcarnitylcholine and other carnitine derivatives
Authors: Kato Gabor , Hosein E. A.
Published: May 2006

Carnitine, γ-trimethylammonium-β-hydroxy butyric acid, was synthesized from γ-chloro-β-hydroxy butyronitrile. Acetylcarnitylcholine was prepared either by the esterification of acetylcarnitine or by the acetylation of carnitylcholine.
Cationic cyclization of deuterated manool
Authors: Edwards O. E. , Mootoo B. S.
Published: May 2006

A test of the mechanism of acid-catalyzed cyclization of manool to 14α-hydroxyhibane was achieved by synthesis and cyclization of 7,7,9,17,17-pentadeuteriomanool. The reaction involves initial formation of a cyclooctenyl cation, an unusual in vitro step. The mass spectrum of the deuterated manool in relation to that of manool was used to analyze its fragmentation.
New nitrochalcones. IX
Authors: Széll T. , Sohár I.
Published: May 2006

A number of new nitrohydroxychalcones are reported. Electron-donating groups in the aldehyde favor condensation by HCl, and electron-withdrawing substituents favor condensation by NaOH.
Hexahalocyclopentadienes. I. A reinvestigation of the reaction of hexachlorocyclopentadiene with fluoro- and chlorosulfonic acids
Authors: Pews R. G.
Published: May 2006

The reaction of hexachlorocyclopentadiene with chlorosulfonic acid has been reinvestigated and the product found by spectral methods to be the chlorosulfate ester of undecachloropentacyclo[5.3.0.02,6.03,9−.04,8]decan-5-ol. With fluorosulfonic acid, the analogous fluorosulfate ester is formed and not octachloro-3a,4,7,7a-tetrahydro-4-7-methanoindene-1,8-dione as reported by McBee and Newcomer. A mechanism is proposed for the reaction.
Effect of solvent and temperature upon the rotationally averaged vicinal coupling constants of some substituted 1,2-dibromoethanes
Authors: Reynolds W. F. , Wood D. J.
Published: May 2006

The solvent dependence of vicinal coupling constants has been investigated for (1,2-dibromoethyl)-benzene and three of its 4-substituted derivatives and for threo- and erythro(1,2-dibromopropyl)benzene. The temperature dependence of the vicinal coupling constants of three of the compounds has also been investigated. The difference between the two vicinal coupling constants of (1,2-dibromoethyl)benzene is dependent upon solution dielectric constant (in non-aromatic solvents) while the sum of coupling constants remains constant. The relative stabilities of its three rotamers are deduced from this information. A polar substituent in the 4-position does not affect the rotational equilibrium in any predictable manner. The vicinal coupling constant of threo(1,2-dibromopropyl)benzene is strongly solvent dependent. The relative stabilities of its three rotamers are deduced from the observation that the vicinal coupling constant is temperature independent. The most stable rotamer of erythro(1,2-dibromopropyl)-benzene is deduced from the observation that the vicinal coupling constant is large and independent of solvent. Factors affecting conformational preference are deduced. It is concluded that dipolar interactions are as important as steric interactions.
Study of isotopic effects and determination of the quadrupole coupling constant from the nuclear magnetic resonance spectra of monodeuterobenzene in a nematic phase
Authors: Diehl P. , Khetrapal C. L.
Published: May 2006

The proton and the deuteron magnetic resonance spectra of monodeuterobenzene have been studied in the nematic phase of a mixture of 50% 4-methoxybenzylidene-4-amino-α-methyl cinnamic acid-n-propyl ester and 50% anisole–azophenyl-n-capronate at room temperature.The proton spectrum is studied as a superposition of three 5-spin sub-spectra due to coupling with one deuteron (spin I = 1) and analyzed iteratively as a 7-spin system, treating the deuteron as two spin [Formula: see text] particles.The values of the dipole–dipole couplings show minor but significant deviations due to isotopic substitution, from those expected for the regular hexagonal geometry. Two parameters are necessary to define molecular orientation. The ratio of the two orientation parameters is reported.The ratios (rHD/rHH)ortho and (rCH − rCD)/(rHH)ortho are obtained. They indicate a reduction in the time average value of the C—D bond length compared to the C—H one.It is suggested that the orientation parameters from the proton spectrum of the molecule are used in order to determine the deuteron quadrupole coupling constant from deuteron magnetic resonance (d.m.r.) spectra of partially deuterated molecules dissolved in the nematic phase. The method is applied to the present case. Its limitations and the sources of errors are discussed.
Metabolites of pathogenic fungi. VIII.1 – 3 Floccosin and floccosic acid, two metabolites from Epidermophyton floccosum (Harz) Langeron and Milochevitch, 1930
Authors: Blank F. , Buxtorf C. , Chin O. , Just G. , Tudor J. L.
Published: May 2006

Floccosic acid, floccosin, its magnesium complex, and a green iron-containing pigment, floccoviridin, were isolated from E. floccosum. Structure 7 is proposed for floccosic acid, and degradative work defining some of the functions in floccosin as depicted in partial formula C is described.
Fragmentation and rearrangement processes in the mass spectra of perhalogenoaromatic compounds. Part II. Pentafluorophenyl derivatives of GroupIV
Authors: Miller J. M.
Published: May 2006

The mass spectra of compounds of the type (C6F5)4M (M = Si, Ge, Sn, and Pb) have been studied. Bond forming rearrangements were detected, involving fluorine abstraction by the central atom, forming perfluorophenylene ions and neutral metal fluoride species. The heavier metals give simpler spectra and fragmentation schemes. The bulk of the ion current is carried by fluorocarbon ions for the silicon derivative and by organometallic or metal fluoride ions in the other three cases, SnF+ and PbF+ forming the base peaks in their spectra. When M is carbon in the compounds (C6F5)3COH and (C6F5)2CO, there is little evidence for rearrangements and transfer of fluorine to the central carbon atom.
Anion–molecule complexes in solution. III. Nuclear magnetic resonance studies of halide ion–alcohol association
Authors: Green R. D. , Martin John S. , Cassie W. B. McG. , Hyne J. B.
Published: May 2006

Certain alkyl-, aryl-, and arene-substituted alcohols form linear, hydrogen bonded complexes with bromide and other halide ions in tetrachloromethane. The hydroxyl proton shifts ca. 4 p.p.m. downfield in the complex, regardless of the degree or type of substitution. The interaction is enhanced by inductive electron withdrawal by substituents on the C—O—H moiety. A comparison of the present results with infrared spectroscopy shows that the absorption at ca. 3300 cm−1 is entirely due to 1:1 alcohol–anion complexes. The a coefficient in Buckingham's equation for electrostatic interaction of a molecule with an ion, δσE = aEz−bE2, is found to be 5.5 for alcohol O—H bonds.
Detection of the triple ion (durosemiquinone-Na2)+ by electron spin resonance spectroscopy
Authors: Gough T. E. , Hindle P. R.
Published: May 2006

Reduction of duroquinone by sodium in tetrahydrofuran and in 2-methyltetrahydrofuran in the presence of sodium tetraphenylboride yields the triple ion (durosemiquinone-Na2)+ which shows hyperfine interaction with twelve equivalent hydrogen and two equivalent sodium nuclei. When the reduction is performed in 1,2-dimethoxyethane, the triple ion is not formed, and the electron spin resonance spectra indicate the presence of an intermolecular cation exchange process.
Si+ and SiO+ reactions of atmospheric importance
Authors: Fehsenfeld F. C.
Published: May 2006

Flow system measurements are reported of the approximate rate constants for the gas phase reactions Si+ + O2 → SiO+ + O, SiO+ + N → Si+ + NO or NO+ + Si, and SiO+ + O → Si+ + O2. The constants are, respectively, <10−11, ∼1.5 × 10−10, ∼1.5 × 10−10, and 2 × 10−10, all in cm3 s−1.
Aeronomic importance of ion–molecule clustering reactions
Authors: Bohme D. K.
Published: May 2006

A literature survey of observations of ion clusters in mass spectrometers indicates that the association rate constant depends on the number of atoms in the cluster. An altitude profile of estimated apparent bimolecular rates of clustering in the atmosphere is made from this empirical correlation. Experimental measurements of the termolecular rate constant for clusters in formation are reported; the temperature dependence of some of these has been measured.
Optical rotatory dispersion and circular dichroism of diastereoisomers. I. The ephedrines and chloramphenicols
Authors: Mitscher L. A. , Kautz F. , LaPidus J.
Published: May 2006

Optical rotatory dispersion (o.r.d.) and circular dichroism measurements are reported for all four diastereoisomers in both the ephedrine and chloramphenicol series. The Cotton effect associated with the 1Lb absorption band is a reliable guide to absolute configuration in both series whereas the 1La band is not. Circular dichroism measurements are preferred as the 1La band dominates the o.r.d. curves to such an extent that erroneous assignment is quite possible. An attempt to relate the sign and intensity of the 1Lb Cotton effect with rotamer population failed due to lack of apparent correlation.
Infrared spectroscopic studies of adsorption and catalysis. Part 3. Carboxylic acids and their derivatives adsorbed on silica
Authors: Young R. P.
Published: May 2006

Infrared spectra in the region 4000–1300 cm−1 have been obtained of acetic acid, acetyl chloride, acetic anhydride, propionic acid, and propionyl chloride adsorbed on discs of pressed silica powder. In all cases the spectra showed the presence of both the simple hydrogen-bonded species[Formula: see text]where X = OH, Cl, or O.CO.R and Si* represents a surface silicon atom, and also chemisorbed surface ester groups R.CO.O—Si*. The latter were characterized by a νC=O frequency in the 1760–1740 cm−1 region, whereas in the case of hydrogen-bonded physical adsorption, the νC=O frequency was about 20–30 cm−1 lower than that of the same molecule in the vapor phase. At high temperatures (150–200 °C) the water or hydrogen chloride eliminated in the surface esterification reaction was desorbed, and high conversions of surface OH to surface ester groups were observed. Under these conditions the carboxylic acid was formed from both the chloride and the anhydride; the latter was also produced at room temperature from the acid chloride. A scheme is suggested for the equilibration of these compounds on hydroxylated silica surfaces. The chemisorbed ester groups were susceptible to hydrolysis by water vapor, thus regenerating the original silanol OH groups.
Excitation and ionization of Hg by metastable states of N2 and CO
Authors: Dugan C. H.
Published: May 2006

When metastable states of N2 and CO collide with mercury atoms, the excitation energy can be transferred to the mercury atom, yielding a fluorescence in the spectral lines of mercury. This note describes observations of this process using a thermal beam of metastable molecules excited by electron impact. Metastable CO excites only the 63P levels of Hg. Metastable N2 excites predominantly 63P, but some 10% of collisions excite 61P, and higher states are also excited. In addition, ionization of Hg by excited N2 (but not by CO) is reported. Other observations are reported briefly.
Determination of the activity of water in highly concentrated perchloric acid solutions
Authors: Wai Henry , Yates Keith
Published: May 2006

The water activities of concentrated aqueous perchloric acids in the range 40–75% have been determined at 25 °C using a modified isopiestic method.
Base strengths of substituted 2- and 4-styrylpyridines in the ground and excited states
Authors: Doty J. C. , Williams J. L. R. , Grisdale P. J.
Published: May 2006

The base strengths of various 2- and 4-styrylpyridines in the ground state and first-excited-singlet state have been determined. The base strengths are found to conform to the Hammett equation if the proper σ values are chosen.
Epoxides of 1,1-dichloro-2,2-difluoroethylene and chlorotrifluoroethylene
Authors: Chow D. , Jones M. H. , Thorne M. P. , Wong E. C.
Published: May 2006

The major products from the photochemically initiated oxidation of 1,1-dichloro-2,2-difluoroethylene and chlorotrifluoroethylene in the liquid phase are the corresponding epoxides and acyl halides. The epoxides have been isolated in pure form and characterized.
Three forms of aluminium in aqueous systems determined by 8-quinolinolate extraction methods
Authors: Turner R. C.
Published: May 2006

8-Quinolinolate extraction methods for the determination of Al3+ plus mononuclear hydroxyaluminium ions, polynuclear hydroxyaluminium ions, and the initial solid phase formed when a base is added to AlCl3 solutions, are presented. The methods are based on the rates of reactions of 8-quinolinol with the 3 forms of aluminium substances. Results under a variety of experimental conditions are reported.
Calculated R.R.K.M. unimolecular dissociation rate constants for hydrazine
Authors: Setser D. W. , Richardson W. C.
Published: May 2006

Unimolecular rate constants for hydrazine dissociation by thermal and chemical activation have been calculated according to the R.R.K.M. theory. The two activated complex models used in the calculations represent plausible upper and lower bounds to the rate constants. The calculations are mainly directed toward establishing expected decomposition to stablilization ratios of N2H4 produced by combination of NH2 radicals; however, a general comparison to available experimental data for hydrazine dissociation is made.
Studies of the phosphorodiamidates of alkali metals
Authors: Sadana Y. N.
Published: May 2006

Phosphorodiamidates of lithium, rubidium, and cesium have been prepared and characterized. The infrared spectra and the X-ray powder diffraction patterns of these and the previously known sodium and potassium salts have been recorded and discussed.
Diagramme de phase du système Rb–Rb2O: le sous-oxyde de rubidium Rb3O
Authors: Touzain Ph.
Published: May 2006

The Rb–Rb2O diagram system has been obtained by the technique of differential thermal analysis. The samples of different compositions were prepared by direct synthesis from doubly distilled rubidium and gaseous oxygen. This system shows a golden eutectic which melts at −10 °C for a composition close to RbO0.2, and a compound which exhibits incongruent melting (at 48 °C). The latter can be isolated as copper colored crystals by centrifugation of the liquid mixture; it is a sub-oxide with the formula Rb3O. Dismutation of Rb2O in Rb2O2 and Rb is observed at 410 °C.
γ-Radiolysis of cyclohexane with electron scavengers. VII. Perfluorocyclohexane and perfluorobenzene as electron scavengers
Authors: Sagert N. H. , Reid J. A. , Robinson R. W.
Published: May 2006

The room temperature, liquid phase radiolysis of cyclohexane has been investigated using perfluorocyclohexane (C6F12) and perfluorobenzene (C6F6) as electron scavengers. Yields of the respective monohydrofluorocarbons were investigated over several orders of magnitude scavenger concentration. The C6F11H yield from the C6F12–cyclohexane system has previously been shown to result from electron capture by C6F12. The data over the extended concentration range were used to calculate a total ion yield of 4.3 ± 0.2 G units and a free ion yield of 0.14 ± 0.02 G units. With C6F6 as an electron scavenger, hydrogen, cyclohexene, and dicyclohexyl yields were all reduced. However, C6F5H yields were much lower than the C6F11H yields from C6F12. On changing the neutralization step by adding the proton scavenger ethanol, C6F5H yields were obtained equal to the C6F11H yields from C6F12. Thus C6F6 is as efficient an electron scavenger as C6F12. Since a change in the neutralization process produces a large change in yield, it is likely that C6F5H (or C6F5) is produced in the neutralization process.
Thermal decomposition of hydrazoic acid as a possible source of NH radicals
Authors: Richardson W. C. , Setser D. W.
Published: May 2006

The thermal decomposition of hydrazoic acid in the presence of methane, ethane, and propane investigated over the temperature range 285–470 °C gave only N2, NH3, and polymer as products. Limited experiments were done with ethene as a substrate, and products were formed which correspond to reactions of nitrogen containing radicals with C2H4. The pyrolysis of HN3 is not a good source of NH radicals due to heterogeneity and complex secondary reactions of radicals with HN3.
Explosive sensitivity of cobalt(III) ammine complexes
Authors: Joyner Taylor B.
Published: May 2006

Unexpected uniformities in the explosive sensitivities of a number of coordination compounds have been observed. These suggest that the kinetics of reaction within the hotspot (as distinct from either generation of the hotspot or propagation from the hotspot to macroscopic proportions) play a critical role in determining the sensitivity of an explosive to initiation by impact.
Spectroscopic and acoustic measurements in relation to the conformation of a cyclic sulfite and a cyclic sulfate
Authors: Hamblin P. C. , White R. F. M. , Eccleston G. , Wyn-Jones E.
Published: May 2006

In the investigation of certain types of conformational equilibria, the ultrasonic absorption technique can be used to supplement information derived from more conventional spectroscopic techniques, and thereby lead to a more detailed analysis of molecular configuration.Nuclear magnetic resonance, infrared spectra, and ultrasonic absorption measurements indicate that both 4-methyl trimethylene sulfite and 4-methyl trimethylene sulfate exist as equilibrium mixtures of two chair isomers. In each case one isomer is strongly predominant.
Studies in ferrocene derivatives. VII. The synthesis of ferrocenyl ethylenes via an abnormal Grignard reaction
Authors: Horspool W. H. , Sutherland R. G. , Sutton J. R.
Published: May 2006

RMgBr reacts normally with acylferrocenes to give the corresponding alcohols. RMgI gives good yields of the most highly substituted ferrocenyl ethylene. In solutions of moderate acid strength, α-ferrocenyl carbonium ions lose a proton to form the substituted alkene rather than undergo nucleophilic attack by water to give the corresponding alcohol. Since the alcohols are more basic than the alkenes, it is possible to devise a general synthesis of ferrocenyl ethylenes by the reaction of any Grignard reagent with an acylferrocene.
13C Nuclear magnetic resonance studies. XII. Conformational effects on 13C shieldings in alicyclic oxygenated compounds
Authors: Buchanan G. W. , Stothers J. B. , Wu Siu-Tzyy
Published: May 2006

The 13C shieldings of the primary carbinyl carbons in cyclohexylmethanol, its acetate and methyl ether as well as those for the corresponding carbon in their 4-t-butyl derivatives have been measured at 15.1 MHz using the 'proton-decoupling' method. Similar data for the 1-methyl-4-t-butylcyclohexylcarbinols and their acetates were obtained to examine the influence of the additional methyl substituent. Possible origins of the observed conformational effects on 13C nuclear shieldings are considered. The 1H results for the methylene protons in these carbinyl groups are also presented and discussed. These results, which permit estimations of the conformational free energies (−ΔG°) of the —CH2OR groupings (R = H, Ac, Me), are presented to illustrate the 13C approach to conformational analysis.
Composition of the leaf wax of Little Club wheat
Authors: Tulloch A. P. , Weenink R. O.
Published: May 2006

Leaf wax of Little Club wheat is composed of: hydrocarbons (8–15%); esters (20–26%); alcohols (25–42%); acids (2%); β-diketone (6–10%); hydroxy β-diketones (9–16%); and unidentified material (9–12%). The esters are mainly octacosanol esters of C14 to C32 fatty acids but lesser amounts of esters of trans 2-tetracosenoic and trans 2-docosenoic acids also occur. The free alcohols are almost entirely octacosanol. The β-diketone is hentriacontane-14,16-dione and the hydroxy-β-diketones are a 1:1 mixture of 8- and 9-hydroxyhentriacontane-14,16-diones.
Conformation and configuration of some α,β-unsaturated carbonyl compounds from their nuclear magnetic resonance spectra
Authors: Phillips W. M. , Currie D. J.
Published: May 2006

Nuclear magnetic resonance spectra were recorded for 95 styrenes with two functional groups (A and B) on the β-carbon atom where A, B are COCH3, COCH3; COCH3, CO2C2H5; CO2C2H5, COCH3; CO2C2H5, CO2C2H5; CO2C2H5, CN; and CO2C2H5, H. The chemical shifts of the ethylenic hydrogen and the hydrogens of the functional A and B groups were examined in detail to determine the effects of ring substituents. The configuration of the unsymmetrical styrenes and the conformation of the A and B groups as deduced from the spectra are discussed.
Chromic acid oxidation of aromatic alcohols
Authors: Stewart Ross , Banoo Fariza
Published: May 2006

The mechanism of the chromic acid oxidation of di- and tri-aryl carbinols has been studied in 80 wt% acetic acid containing sulfuric acid. The reactions are cleanly second-order and give benzophenones in the case of the secondary alcohols and benzophenones plus phenols in the case of the tertiary alcohols. Electron-donating substituents in the tertiary alcohol appear predominantly in the phenol component and the rate-controlling step is believed to be a 1,2-aryl shift. The reaction constant for the migration is ρ+ = −1.44 and that for the overall reaction is ρ+ = −0.879. The presence of manganous ions does not alter these values although it lowers the overall rate of reaction. Although an analogous 1,2-hydride shift mechanism can be written for the oxidation of the secondary alcohols, there are enough points of difference between the oxidations of the secondary and tertiary systems to make this appear unlikely.
Branched-chain sugar nucleosides. II. 9-(3-Deoxy-3-C-hydroxymethyl-β-D-glucopyranosyl)-adenine
Authors: Rosenthal Alex , Sprinzl M. , Koch H. J.
Published: May 2006

Application of the oxo reaction to 1,2,4,6-tetra-O-acetyl-3-deoxy-α-D-erythro-hex-2-enopyranose (1), followed by acetylation of the oxo products, gave crystalline 1,2,3′,4,6-penta-O-acetyl-3-deoxy-3-C-(hydroxymethyl)-α-D-glucopyranose (2) in about 30% yield. Conversion of 2 into the branched-chain sugar bromide, followed by condensation of the latter with 6-benzamidochloromercuripurine afforded a blocked branched-chain sugar nucleoside (5) in 67% yield based on 2. The nucleoside (5) was deblocked with methanolic sodium methoxide to afford 9-(3-deoxy-3-C-hydroxymethyl-β-D-glucopyranosyl)-adenine (6) in 75% yield.
Solvolyse des tosylates des tert-butyl-4 diméthyl-2,2 cyclohexanols cis et trans
Authors: Richer Jean-Claude , Belanger Patrice
Published: May 2006

not available
Collisional deactivation of singlet methylene in the photolysis of ketene
Authors: Cox R. A. , Preston K. F.
Published: May 2006

An investigation has been made into the effect of inert gas additions on product quantum yields for the photolysis at 2800 and 2490 Å of mixtures of ketene and oxygen and for the photolysis at 2800 Å of mixtures of ketene and carbon monoxide. Concentration ratios of O2 (or CO) to CH2CO were chosen so that the reaction of CH2(3Σg−) with CH2CO could be ignored and C2H4 formation could be attributed entirely to the reaction[Formula: see text]Quenching of the C2H4 quantum yield by inert gases was interpreted in terms of collisional deactivation of CH2(1A1) to the ground state[Formula: see text]and rate constant ratios k2/k1 have been determined for a number of gases: He (0.018), Ar (0.014), Kr (0.033), Xe (0.074), N2 (0.052), N2O (0.10), CF4 (0.047), C2F6 (0.11), and SF6 (0.045). It has been assumed that collision-induced intersystem crossover in excited singlet ketene makes an insignificant contribution to the observed quenching effects, but it has not been possible to verify this assumption experimentally. The mechanism of collision-induced electronic relaxation of singlet methylene is discussed in the light of the results.
Thermodynamic properties of ruthenate and molybdate ions
Authors: Hepler Loren G.
Published: May 2006

Thermodynamic data that have been obtained subsequent to compilations by the U.S. National Bureau of Standards and Latimer now permit calculation of ΔGf0, ΔHf0, and [Formula: see text] values for RuO42− (aq) and MoO42− (aq). Use of these quantities is illustrated by calculation of thermodynamic properties of Ag2MoO4 (c).
Reductions with sulfurated borohydrides. III. Borohydrides incorporating selenium and tellurium
Authors: Lalancette J. M. , Arnac M.
Published: May 2006

The reactions of selenium and tellurium with lithium, sodium, potassium, and tetramethylammonium borohydrides have been examined, using the hydrogen evolution as a measurement of the replacement of hydrogen by the chalcogen on the borohydride anion. Of all the possible reactions, only the combination of sodium borohydride with tellurium led to a stable compound, easily isolated and of definite stoichiometry. This new borohydride, NaBH2Te3 offers interesting possibilities as a reducer.
Absolute rate constants for hydrocarbon autoxidation. XV. The induced decomposition of some t-hydroperoxides
Authors: Howard J. A. , Ingold K. U.
Published: May 2006

The radical induced decomposition of several t-hydroperoxides at 30° has been studied. In the self reaction of t-alkylperoxy radicals the ratio of the rates of alkoxy radical diffusion from the cage to combination in the cage is essentially independent of the size of the t-alkyl group.The rate constant for abstraction from hydroperoxides of the hydroperoxidic hydrogen by alkoxy radicals is about 4 × 106 M−1 s−1 at 30°. This reaction has a deuterium isotope effect, kH/kD ≈ 5.The 1,1-diphenylethoxy radical undergoes a 1,2-phenyl shift to yield the 1-phenyl-1-phenoxyethyl radical more rapidly that it undergoes β-scission.
Infrared spectroscopic investigations of zeolites and adsorbed molecules. Part V. Carbon dioxide
Authors: Angell C. L. , Howell M. V.
Published: May 2006

When bivalent cation-exchanged, but not univalent or decationized, Type X or Y zeolites are heated at 500° in the presence of carbon dioxide, two or three bands appear in the 1600 to 1300 cm−1 region of the infrared spectrum. These bands are stable even at 700°, and their frequencies are cation-dependent. They are assigned to a unidentate surface carbonate species, which (in the case of Ca Y) blocks about 20% of the surface cations.
Aliphatic diazo compounds. IX. The base-induced dimerization of α-diazo ketones
Authors: Yates Peter , Giles R. G. F. , Farnum D. G.
Published: May 2006

Treatment of 2-diazoacetophenone (1) with potassium t-butoxide in t-butyl alcohol gives a colorless dimer, which is shown to be 5-benzoyl-2-phenacyltetrazole (4) by its independent synthesis by phenacylation of 5-benzoyltetrazole. The latter reaction also gives 5-benzoyl-1-phenacyltetrazole (3), which is distinguished from 4 by its reduction to di(2-hydroxy-2-phenylethyl)amine and by its cyclization on treatment with ammonium acetate. The assignment of the structure of the colorless dimer of 1 permits the postulation of related pathways for its formation and that of the red-brown dimer obtained on treatment of 1 with potassium hydroxide in dimethyl sulfoxide. 2-Phenacyltetrazole (22) and benzoic acid are formed in addition to 4 on treatment of 1 with potassium t-butoxide in t-butyl alcohol; these are considered to arise via cleavage of 4, since prolonged treatment of 4 and 3 with potassium t-butoxide in t-butyl alcohol gives 22 and 1-phenacyltetrazole (24), respectively. Compounds 22 and 24 have been prepared independently by phenacylation of tetrazole.
Mechanisms of action of trypsin and chymotrypsin
Authors: Kasserra H. P. , Laidler K. J.
Published: May 2006

The mechanistic evidence for reactions catalyzed by chymotrypsin and trypsin is briefly reviewed and is considered with reference to the structure as determined by the X-ray studies. Conclusions are drawn about the detailed nature of the processes of complex formation, acylation, and deacylation. Although there are significant differences between the two enzymes as far as specificity and pH effects are concerned, it appears that the mechanisms of their action are very similar.
Structural aspects of the hydrolysis products of metal alkoxides and metal trialkylsilyloxides
Authors: Lorimer J. W. , Jones D. E. G.
Published: May 2006

The average degree of polymerization [Formula: see text] depends on the average degree of hydrolysis [Formula: see text] as[Formula: see text] over a large range of [Formula: see text] for all metal oxide alkoxides and oxide trialkylsilyloxides that have been formed by hydrolysis and examined in solution. A number of general theoretical models are developed which permit quantitative interpretation of the parameters a and b. Mixtures of linear or branched chains in proportions governed wholly or partly by the degree of polymerization of the unhydrolyzed alkoxide can explain all the data on oxide alkoxides in solution in their corresponding alcohol, and the model leads to a plausible mechanism for disproportionation. Similar models with more complex structure can be involved in the metal oxide trialkylsilyloxides. Heterogeneity in the composition of the repeating units or in the number of metal–oxygen–metal bridges between successive repeating units can also be significant for both oxide alkoxides and oxide trialkylsilyloxides. Models involving cyclic chains are possible, but steric effects make them improbable in many cases. Mixtures of chains with equal average degrees of hydrolysis for each type of chain have been assumed in previous analyses, but are shown to be special cases of the more general model.
Vibrational spectra of halopentacarbonylmanganese(I) derivatives
Authors: Butler I. S. , Spendjian H. K.
Published: May 2006

The solid-state infrared (i.r.) and laser Raman spectra of the halopentacarbonylmanganese(I) derivatives, Mn(CO)5X (X = Cl, Br,and I), have been recorded in the C—O stretching and the low frequency (700–33 cm−1) regions. The i.r. overtone and combination spectra recorded in the regions 2800–2250 and 1350–700 cm−1 have been used to help in the assignment of some of the low frequency fundamentals. The solid-state i.r. and laser Raman spectra of the dimeric halotetracarbonylmanganese(I) derivatives, [Mn(CO)4X]2 (X = Br and I), have been recorded in the C—O stretching and the low frequency regions for comparative purposes and shown to be consistent with the expected D2h symmetry of the molecules.
Oxidation of hydrocarbons in the liquid phase: n-dodecane in a borosilicate glass chamber at 200 °C
Authors: Boss B. D. , Hazlett R. N.
Published: May 2006

The 5-h oxidation of n-dodecane at 200 °C by air at 1 atm is reported for experiments in a borosilicate glass reaction chamber equipped with a gas bubbler. The rate of reaction was limited by the rate of oxygen diffusion from the gas phase due to the rapid reaction of dissolved oxygen. The reaction products were analyzed in aliquots taken periodically from the reaction chamber. Chemical analyses, gas–liquid phase chromatography (g.l.p.c.), tandem g.l.p.c.-mass spectroscopy, infrared, and ultraviolet were used to identify products accounting for 98% of the oxygen reacted. The isomer distribution of the dodecenes, dodecanols, and dodecanones formed, as well as the distribution of carboxylic acids, were determined. Three classes of intramolecular reaction products, cyclic ethers, cyclic hydrocarbons, and lactones, were detected. Many volatile products were detected. A filterable precipitate obtained after 10 h of oxidation was studied using infrared attenuated total reflectance techniques. A reaction mechanism is discussed based on current knowledge of other systems, the products identified, and the stoichiometry of the reaction.
Dibenzo[a,d]cycloheptene and related compounds. II. The synthesis of some 11-substituted dibenzo[b,e]azepin-6-one, 5-substituted dibenzo[a,d]cycloheptene, and 12-substituted dibenzo[a,d]cyclooctene derivatives
Authors: Ackermann K. , Chapuis J. , Horning D. E. , Lacasse G. , Muchowski J. M.
Published: May 2006

The synthesis of several 11-substituted-5,6-dihydro-11H-dibenzo[b,e]azepin-6-ones, and an improved method of preparing 5-cyano-10,11-dihydro-5H-dibenzo[a,d]cycloheptene and 12-cyano-5,6,7,12-tetrahydrodibenzo[a,d]cyclooctene are described.A description of the synthesis of epoxides from diaryl ketones and dimethylsulfonium methylide by a modified technique is given.The nuclear magnetic resonance spectra of several of the 11-substituted dibenzo[b,e]azepin-6-ones are interpreted on the basis of a slow interconversion between diastereomeric boat conformers in which the C-11 substituent is quasi axial or quasi equatorial.
Solvation effects on conformational equilibria. Studies related to the conformational properties of 2-methoxytetrahydropyran and related methyl glycopyranosides
Authors: Lemieux R. U. , Pavia A. A. , Martin J. C. , Watanabe K. A.
Published: May 2006

Further evidence is presented (8) that changes in optical rotation at the D-line of sodium which occur with changes in solvent largely reflect changes in conformational equilibria.Changes in the nuclear magnetic resonance spectrum of 4,4,5,5-tetradeuterio-2-methoxytetra-hydropyran and in the rotation of s(+)-2-methoxytetrahydropyran with changes in solvent are interpreted to show that solvents capable of donating a hydrogen to a hydrogen bond have an effect on the magnitude of the anomeric effect which is greater than that resulting from the change in the dielectric constant of the solvent. In the case of methyl 2-deoxypyranosides with the methoxy group in axial orientation, water appears to have an especially profound influence in stabilizing that orientation of the methyl group which brings it into gauche relationship with both the C2-grouping and the anomeric hydrogen; that is, counter to the anomeric effect.The methyl 2-deoxy-β-L-erythro-pentopyranoside was synthesized from di-O-acetyl-L-arabinal by way of an iodomethoxylation. Deuterolysis of the resulting 1,2-trans-acetylated methyl 2-deoxy-2-iodopentosides is shown to proceed in one case with extensive inversion of configuration and with extensive retention in the other case and offers a route to the preparation of 2-deoxy-2-deuterio-erythro-pentose with a high proportion (>75%) of the diastereoisomer with the arabino-configuration.
Photochemical and thermal isomerizations of cis- and trans-cinnamic acids, and their photostationary state
Authors: Hocking Martin B.
Published: May 2006

cis-Cinnamic acid was prepared photochemically from the trans isomer according to a published method, but was isolated by vacuum distillation. The photostationary state of these acids has been determined for moderately concentrated solutions of each isomer exposed to unfiltered ultraviolet. The position of the cis–trans thermal equilibrium approached from all cis- and from all trans-isomers has been tested without solvent and found to lie at, or very close to, 100% trans. Kinetic examination of the rates of these isomerizations shows that they fit a kinetic expression of the form −d[cis]/dt = k[cis] [H+].
Nature of the coordination bond in metal complexes of substituted pyridine derivatives. IV. Skeletal vibration spectra and the substituent effect upon the coordination bond of the pyridine complex of zinc(II) ion
Authors: Wong Patrick T. T. , Brewer D. G.
Published: May 2006

Far infrared spectra of the complexes Zn(pyridine)2X2, where X = Cl or Br, have been investigated in the region 350–20 cm−1. Eight infrared-active skeletal modes of these complexes have been observed, and a tentative assignment of these absorption bands has been made. The previous investigation of the effect of substituents upon the coordination bond of the copper–pyridine complex has been extended to the zinc–pyridine complex in the present paper. It was found that the relative zinc–pyridine bond strength, affected by the substituents, is determined by both the relative σ-contribution and π-contribution to the bond, rather than mainly by the σ-contribution as in the system of copper complexes. The force constants associated with the zinc–pyridine coordination bond of a series of 4-substituted pyridine complexes have been calculated by a normal coordinate treatment described in previous papers in this series.
Fluorocarbon-bridged di(tertiary phosphine) complexes of Group VIB metal carbonyls
Authors: Cullen W. R. , Dong D. F. , Thompson J. A. J.
Published: May 2006

A series of complexes of the general formula [Formula: see text]n = 2, 3, or 4; M = Cr, Mo, or W have been prepared. The properties of the new complexes, in particular their infrared spectra, are discussed.