bluuebunny/crossref_metadata_2025 huggingface dataset:
Cyclic Imides. Preparation of Silylphthalimides and Characterization by Infrared and Mass Spectrometry
Authors: Janzen A. F. , Kramer E. A.
Published: May 2006

A series of silylphthalimides containing silicon substituents —H, —CH3, —C2H5, —CH2CH=CH2, and —C6H5 have been prepared and characterized. The compounds are N-silylated and found to be monomeric in the liquid and gas phase. The i.r. spectroscopic studies in dilute (10−1 M) chloroform solution showed a decrease (approximately 40 cm−1) in the carbonyl stretching frequency on silylation, but relatively small changes (± 7 cm−1) on changing silicon substituents. The major effect appears to be electron donation by silyl groups. The N15 isotopomers were prepared and C—N and Si—N vibrations identified.Mass spectrometric studies of methyl- and phenylsilylphthalimides, including N15 substitution, are reported. A possible mechanism of formation of methyl- and phenylbiphenylene silicon ions, involving loss of methyl or phenyl, carbon dioxide, and hydrogen cyanide, is suggested.
Proton Magnetic Resonance Studies of Rotational Isomerism in Halotoluene Derivatives. VI. Rotational Barrier and Conformational Energy Differences in α,α,2,3,6-Pentachlorotoluene
Authors: Stewart M. A. H. , Schaefer T. , Hutton H. M. , Wong C. M.
Published: May 2006

Rotation by π radians about the sp2–sp3 carbon–carbon bond of the dichloromethyl group in α,α,2,3,6-pentachlorotoluene interconverts the two conformations which are characterized by coplanarity of the aromatic ring with the C—H bond of the sidechain. The ring protons undergo effective nonmutual exchange during this rotation. The rate of rotation as a function of temperature is extracted by line-shape fitting of the ring p.m.r. spectra. The rotation is characterized by a negative entropy of activation. The free energy difference between the two conformations is 50 ± 20 cal/mol at 240 °K.
Infrared Spectrum and Hydrogen Bonding in Solid and Liquid Trimethylamine Hydrate
Authors: Falk Michael
Published: May 2006

The OD band profiles of dilute HDO in liquid [Formula: see text] differ only slightly from those in liquid water, showing that the distribution of hydrogen-bond strengths has the same general form in the two media. Absence of shoulders at frequencies corresponding to the OD stretching frequencies of HDO in ice and in crystalline TMA hydrate points to the absence of structurally well-defined ice-like or clathrate-like regions above the melting point of the crystalline TMA hydrate.
Metastable Peak Analysis; a Method for Elucidating Fragmentation Mechanisms and Ion Structures in Mass Spectrometry. Part II. Water Loss from the Molecular Ion of 1,2-Cyclohexanediol
Authors: Benoit F. , Holmes J. L.
Published: May 2006

Defocussed metastable peaks have been used to elucidate the hitherto apparently complex fragmentation of the molecular ion of 1,2-cyclohexanediol. It was shown that the predominant mode of water loss from the molecular ion involved "scrambling" of six hydrogen atoms, those in the 4- and 5-methylene groups and the hydroxyl pair. A minor water elimination involves simple hydroxyl–hydroxyl interaction.
Effect of Solvent Upon the Vicinal Proton Coupling Constants of Complex Substituted Ethanes. II. Anomalous Results for 1-Phenyl-1,2,2-trihaloethanes
Authors: Reynolds W. F. , Wood D. J.
Published: May 2006

The n.m.r. spectra of 11 tetra-substituted ethanes have been obtained in a number of solvents. Changes in the vicinal coupling constants of 1-phenyl-1,2,2-trihaloethanes with solvent do not fit the electrostatic model for solvent effects. It is concluded that the theory breaks down because solute–solvent hydrogen bonding specifically favors the trans rotamers of these compounds. The conditions under which the theory would be expected to break down are also discussed in more general terms.
The Motion of Guest Molecules in Clathrate Hydrates
Authors: Davidson D. W.
Published: May 2006

The reorientation of molecules encaged in hydrates of structures I and II is controlled mainly by the cage geometry and the electrostatic fields of the water molecules. Departure from spherical symmetry of the short-range interactions between the guest molecule and the water molecules which form the cages leads to preferred orientations which become increasingly occupied at low temperatures. A modified Lennard-Jones potential energy calculation shows the preferred positions of Cl2 to lie off-center and close to the equatorial plane of the tetrakaidecahedral cage with the Cl atoms near the axial planes of symmetry. In an attempt to account for the remarkable reorientational freedom of polar guest molecules, the electrostatic fields of the water molecules are treated in detail. It is shown that the geometry of the cages causes the sum of the fields of the cage water dipoles to almost vanish at points near the cage center, but that this is not true of the resultant quadrupolar fields. It is suggested that the quadrupolar fields are also relatively small because the hydrogen bonding to four neighbors considerably reduces the quadrupole moment of the water molecule. The orientational disorder of the water molecules results in a wide distribution of resultant electrostatic fields in different cages. This appears to be the origin of the great width of the dielectric absorption observed at low temperatures in tetrahydrofuran hydrate and of the wide temperature range of variation of the proton magnetic resonance (p.m.r.) line width in tetrahydrofuran deuterate.
Nuclear Magnetic Resonance Study of Ring Inversion in Cycloheptene
Authors: St-Jacques Maurice , Vaziri Cambyse
Published: May 2006

The p.m.r. spectrum of 4,4,5,6,6-pentadeuteriocycloheptene (3) has been studied down to −171 °C. Analysis of the spectral change below −160 °C yielded a ΔF≠ value of 5.0 kcal/mol at −165 °C. Possible energy profiles for the ring inversion of cycloheptene are discussed.
Formation of Lower Nitro Alkanes by Vapor Phase Nitration of Cyclic Hydrocarbons
Authors: Matasa C. , Hass H. B.
Published: May 2006

Vapor-phase nitration of cyclohexane and cyclohexyl nitrite produces primary nitro alkanes, the yield of which decreases with decreasing number of carbon atoms. Both their structure and relative ratios of formation lead to the conclusion that they are formed from 1-pentyl radical, which in turn is formed from cyclohexoxyl radical. The intermediate phases are radical reactions already known from the vapor-phase oxidation of hydrocarbons.
Hindered Rotation and Intramolecular Hydrogen Exchange in N-Phenyl-o-hydroxybenzylamines
Authors: Brownstein S. , Horswill E. C. , Ingold K. U.
Published: May 2006

Non-equivalence of the benzylic hydrogens was found in several N-phenyl-ortho-hydroxybenzyl-amines and, where possible, activation parameters were calculated for the processes causing non-equivalence. Hindered rotation about the aromatic carbon-nitrogen bond was the rate determining process with an ortho-t-butyl group on the aniline ring. Exchange of phenolic and amino hydrogens was studied over a range of temperature and concentration. Both intermolecular and intramolecular exchange were observed. The latter may be the first example of such a process to be studied by n.m.r.
Methyl Glycosidation and Methyl Thioglycosidation of Some Fully Chlorosulfated Pentopyranosyl Chlorides Using Sodium Iodide as a Catalyst
Authors: Jennings H. J.
Published: May 2006

The treatment of α- and β- D-xylopyranosyl chloride 2,3,4-tri(chlorosulfate) and the corresponding α-D-lyxo derivative with a catalytic quantity of sodium iodide in methanol solution resulted in the removal of the chlorosulfate groups and rapid methanolysis of the anomeric chlorine atoms. The methanolysis proceeded with predominant inversion in each case (80–90 %), independent of the orientation of the C-2 substituent. In the presence of sodium methyl mercaptide, however, thioglycosides having an inverted configuration were produced from 1,2-cis chlorides, and thioglycosides having an unchanged anomeric configuration were formed from 1,2-trans chlorides. It is proposed that all these glycosidations occur via a free pentopyranosyl chloride intermediate, and that under the basic conditions of thioglycosidation a 1,2-anhydro intermediate is formed from 1,2-trans chlorides.
Drop Calorimetric Measurements on some Chlorides, Sulfides, and Binary Melts
Authors: Thompson W. T. , Flengas S. N.
Published: May 2006

Enthalpy content measurements on pure KCl, AgCl, CuCl, PbCl2, Ag2S, and PbS were made at temperatures up to 1000 °C using a sapphire calibrated drop calorimeter. Similar measurements were performed on AgCl–Ag2S and AgCl–KCl melts. These results determined values for the integral enthalpy of liquid–liquid mixing.
A Simple Diffusion Cell for the Determination of Absolute Diffusion Constants using Radioactive Tracers
Authors: Dyck Willy
Published: May 2006

Using microscope slides for the diffusion grating, a glass diffusion cell was constructed which permitted the determination of absolute diffusion constants of γ-ray emitting elements in aqueous solutions.The cell was tested at 25 °C with 110Ag as tracer and gave a bulk-diffusion coefficient of 1.64 × 10 −5 cm2/s and a self-diffusion coefficient of 1.48 × 10−5 cm2/s using 0.01 M AgNO3.The hydrogen ion concentration had no detectable effect on the diffusion coefficient of AgNO3 in the pH range −0.48 to 7.5. The presence of Na or Fe(III) ions, or sucrose molecules at moderate concentrations (> 0.1 M) resulted in a marked decrease in the diffusion coefficient.
Use of Nim-t-Butyloxycarbonyl in the Synthesis of Poly-L-histidine
Authors: Fridkin M. , Goren H. J.
Published: May 2006

Nα,Nim--Di-t-butyloxycarbonyl-L-histidine, Nα -benzyloxycarbonyl- Nim-t-butyloxycarbonyl-L-histidine and poly- L-histidine have been synthesized. The role in peptide synthesis of t-butyloxycarbonyl as an imidazole-blocking group is discussed and compared to other currently available imidazole-blocking groups.
Spectroscopie de masse des dérivés dans la série des dicéto-2,5 pipérazines. III
Authors: Jankowski Krzysztof , Varfalvy Louis
Published: May 2006

The fragmentation of 3,6-dibenzyl, 2,5-diketo piperazine in the mass spectrometry is presented. The general mechanism is proposed and discussed.
Reaction of 1-Nitroso-2-naphthylamine with 3-Aroylaziridines
Authors: Lown J. W. , Akhtar M. H.
Published: May 2006

Reaction of 1-nitroso-2-naphthylamine with a series of 3-aroylaziridines affords (a) 3-arylbenzo[f]-quinoxalines, (b) cyclohexylimino derivatives of 2-aroylnaphtho[1,2-d]imidazoles, and (c) a 2-arylnaphtho[1,2-d]imidazole. Electron-withdrawing substituents in either the 2 or 3 aryl moieties of the aziridine lead to preferential formation of products of type a whereas electron-donating substituents in either of these positions result in the formation of products of type b. The results of deuterium labelling and unambiguous synthetic studies in support of the proposed 1,3-dipolar cycloaddition mechanism are discussed.
Cyclization and Fragmentation of N-Chloro Lactams. The Transannular Synthesis of Bicyclic Lactams with Bridgehead Nitrogen
Authors: Edwards O. E. , Paton J. M. , Benn M. H. , Mitchell R. E. , Watanatada Churai , Vohra K. N.
Published: May 2006

High yield peroxide initiated and photochemical conversion of N-chloroazacyclooctanone to 5-chloroazacyclooctanone and of N-chloroazacyclononanone to a mixture of azabicyclo[4.3.0]nonan-2-one and azabicyclo[4.3.0]nonan-9-one is described. N-Chloro-2-azabicyclo[2.2.2]octan-3-one gave 4-chlorocyclohexylamine derivatives under similar conditions, while N-chloro-N-methylpentanoamide gave γ-valerolactone. An apparent ionic, silver ion, and base-catalyzed cyclization of N-chloroazacyclononanone was observed.
Evidence for a Radical Chain Mechanism in the Autoxidation of Triethylbismuth
Authors: Winchester R. V.
Published: May 2006

The autoxidation of triethylbismuth in cyclohexane at 25 °C produces as major products ethanol, acetaldehyde, and a solid suggested to be Bi2O3 with oxygen atoms randomly replaced by =CHCH3 or —CH2CH2— groups. Minor products include diethyl peroxide, diethyl ether, acetic acid, and probably ethylene. The reaction is strongly inhibited by diphenylamine and a radical chain reaction is proposed to account for the observed products.
CNDO/2 Electron Densities and Proton Chemical Shifts
Authors: Sebastian John F. , Grunwell John R.
Published: May 2006

An approximate linear dependence of the proton shifts on the CNDO/21 calculated electron densities on hydrogen for C5H5−, C6H6, C7H7+, C5H5NH+, and C6H5CH2− has been found. The significance and limitations of the correlation are discussed.
Reactions of 1-Phenyl-1,2,3-triazolyllithium Compounds; Formation of Ketenimines, Alkynylamines, and Heterocycles from the Ambident (N-Phenyl)phenylketenimine Anion
Authors: Raap R.
Published: May 2006

At room temperature 1,4-diphenyl-1,2,3-triazolyllithium rapidly undergoes fragmentation to nitrogen and lithium (N-phenyl)phenylketenimine anion 8c, [Formula: see text]. Some of the reactions of this ambident anion have been studied. Reaction of 8c with methyl iodide results in C-methylation to a mixture of (N-phenyl)methylphenylketenimine and 3-methyl-1,3-diphenyl-4-(2′-phenylethylene)-2-phenyliminoazetidine. A six-membered heterocyclic compound, 6-anilino-1,3,5-triphenyluracil, results from the reaction between 8c and phenyl isocyanate. With dimethyl sulfate and methyl chloroformate N-alkylation and N-acylation takes place predominantly, forming N-methyl-N-phenyl-2-phenylethynylamine and N-carbomethoxy-N-phenyl-2-phenylethynylamine respectively. Reaction of 8c with methanol and ethanethiol gives an iminoester and an iminothioester respectively.1-Phenyl-1,2,3-triazolyllithium and 4-methyl-1-phenyl-1,2,3-triazolyllithium undergo fragmentation at somewhat higher temperatures.
Electron Spin Resonance Studies of the Radiolysis of Aliphatic Amines Adsorbed on Silica Gel
Authors: Wardman P. , Smith D. R.
Published: May 2006

Several aliphatic amines have been adsorben in sub-monolayer amounts on silica gel and γ-irradiated at 77 °K. The electron spin resonance (e.s.r.) spectra of the radicals trapped on the surface at 77 °K were similar, in most cases, to the spectra obtained after irradiating the corresponding polycrystalline solid amine at 77 °K. Methyl-, ethyl-, n-propyl, and n-butylamines all gave [Formula: see text] radicals, and dimethylamine gave [Formula: see text] radicals. The radical cation [Formula: see text] was observed in the case of trimethylamine. Adsorbed methoxy-amine and t-butyl amine have also been studied and the cation-radical of the latter tentatively identified. The results are discussed in terms of reaction of the adsorbed amine with a surface active site.
Conformational Preference and Configurational Equilibria of the Methyl 3-Deoxy-3-nitro-pentopyranosides and their Nitronates
Authors: Baer Hans H. , Kovář Jan
Published: May 2006

The conformations of four methyl 3-deoxy-3-nitropentopyranosides and their sodium nitronates in aqueous solution were examined by n.m.r. spectroscopy, and the results are explained by calculation of free energies of non-bonded interactions. It is shown that protonation of glycoside nitronates is a kinetically controlled process. The β-epimerization of nitronates was investigated, and relative thermodynamic stabilities of epimers were determined and correlated with conformations. The non-bonded interaction between the nitronate grouping and an adjacent, equatorial hydroxyl group (A(1,3) effect) must be associated with a free energy in excess of 2 kcal/mol. The influence of this effect upon conformational and configurational equilibria in glycoside nitronates and upon nitromethylene acidity is emphasized. The compounds were found to differ in their behavior during early stages of the β-epimerization reaction, which was linked to differential nitromethylene acidities. Mechanisms for the reaction are discussed.
Synthesis of N-Methylamino Acid Derivatives from Amino Acid Derivatives using Sodium Hydride/Methyl Iodide
Authors: Coggins John R. , Benoiton N. Leo
Published: May 2006

Reaction of N-acetyl-, N-benzoyl-, and N-carbobenzoxy derivatives of aliphatic amino acids with sodium hydride/methyl iodide in tetrahydrofuran containing dimethylformamide at 80° gave the corresponding N-methylamino acid methyl esters as oils in high yields. Saponification of these gave the N-protected-N-methylamino acids, and decarbobenzoxylation gave the N-methylamino acid methyl ester hydrobomides. The products are essentially optically pure and free of unmethylated amino acid derivative.
The Proton Magnetic Resonance Spectra of some Chlorinated Polycyclodiene Pesticide Metabolites. Rapid Assessment of Stereochemistry
Authors: McKinney J. D. , Keith L. H. , Alford A. , Fletcher C. E.
Published: May 2006

The rapid and accurate determination of the relative stereochemistry of some postulated chlorinated polycyclodiene pesticide metabolites without excessive dependence on chemical methods is described. Proton assignments were made employing the new nuclear magnetic resonance (n.m.r.) shift reagent, Eu(DPM)3, which effected the separation of superimposed signals in these systems. The assignments based on coupling constant information and requiring spin decoupling equipment are in good agreement with those obtained from the Eu(DPM)3 studies. The data presented establishes the relative stereochemistry of these biologically important compounds and demonstrates the utility of one or both approaches in elucidating their overall structures.
Studies on Some 2,1-Benzisoxazole Derivatives
Authors: McKinnon D. M. , Wong J. Y.
Published: May 2006

7-Acetyl-3-methyl-2,1-benzisoxazole has been synthesized by reduction of 2,6-diacetylnitrobenzene. While the chemical properties of the compound indicate that it undergoes valency-tautomerism, spectroscopic studies indicate that this is a relatively slow process. Comparisons with other heterocyclic systems having similar properties are noted.
Long-range Spin–Spin Coupling in Pyrimidine Nucleosides
Authors: Hruska Frank E.
Published: May 2006

A study has been made of the 100 MHz p.m.r. spectra of a number of pyrimidine nucleosides in aqueous solution. Long-range five-bond spin–spin coupling interactions between the H-5 and H-1′ hydrogens were noted in uridine, 2′-deoxyuridine, 6-azauridine, and 6-azacytidine and rationalized by a predominantly anti conformation for each nucleoside. The absence of a detectable five-bond coupling in orotidine suggested that the syn conformation is preferred in this instance. The relative magnitudes of the four-bond and five-bond interactions in uridine and pseudouridine were shown to be consistent with the calculated mobile π-bond orders of the C6—N1 and C6—C5 bonds of the uracil base.
Surface Effects in Cationic Polymerizations
Authors: Armstrong V. C. , Katovic Z. , Eastham A. M.
Published: May 2006

β-Methylstyrene dimerizes in the presence of boron fluoride. The rate of dimerization is very erratic under the usual conditions of high vacuum operation but becomes reproducible when reactors are baked out for a few hours at 500 °C under vacuum. In baked reactors reaction still occurs without added cocatalyst, and the rate seems to depend in part on the temperature and length of time of baking. The results suggest the existence of a surface reaction whose rate is of the first order in both monomer and boron fluoride.
Production of O(1D2) Atoms in the Photolysis of CO2 at close to 1600 Å
Authors: Quick L. M. , Cvetanović R. J.
Published: May 2006

Photolysis of CO2/neopentane mixtures with a bromine lamp was studied at room temperature to obtain chemical evidence for primary formation of O(1D2) atoms in the photolysis of CO2 at close to 1600 Å. The trends in the effects of various added gases on the yield of neopentanol agreed well with those reported in the literature for the rates of deactivation of O(1D2) atoms. This agreement demonstrated O(1D2) formation in the photolysis of CO2 at the wavelength used.
Nuclear Charge Dispersion in the Fission of 235U by Protons of Energy 20–85 MeV
Authors: Saha G. B. , Tomita I. , Yaffe L.
Published: May 2006

Independent formation cross sections of 129Cs, 130Cs, 131Cs, 134Csm, 134Csm+g, 136Cs, 139Ce, and cumulative formation cross sections of 141Ce and 143Ce were obtained when 235U was caused to fission with protons of energies varying between 20 and 85 MeV. The energies at which the excitation functions reached their maxima were related to the neutron-to-proton ratio of the fission products. These were compared with other fissioning systems. Charge dispersion curves were obtained from the cross section data. The variation of (ZA − Zp) with energy, both in magnitude and in trend, agrees extremely well with predictions made by Saha and Yaffe for nuclides in this mass range. Calculations for Zp show that good agreement is obtained with the unchanged charge division hypothesis. An estimate has been made of the total number of neutrons emitted in fission at these energies.
Normal Coordinate Calculations of the Vibrations of Methylene Cyclopropane-h6 and -d6
Authors: Bertie J. E. , Norton M. G.
Published: May 2006

Normal coordinate calculations for methylene cyclopropane-h6 and -d6 have been carried out using two models. In the first model 31 internal coordinates were used, and in the second model 25 internal coordinates were used. The force constants were, in each case, refined to the 40 frequencies observed for the two molecules. Using the first model 26 force constants, of which four were constrained, fitted the frequencies with an average error of 1.2% for C4H6 and 2.8% for C4D6. Using the second model 24 force constants, of which two were constrained, fitted the frequencies with an average error of 1.4% for C4H6 and 2.8% for C4D6.The very low isotopic shift of the C=C stretching mode can be explained by an interaction with the ethylenic CH2 deformation, which is best assigned at 1047 m−1, rather than at 1139 cm−1, in C4D6. The calculations indicate that the experimental assignment for the A1 ring breathing mode and the A1 methylenic wag in C4H6 should probably be reversed. For the A1and the B1 modes with frequencies between 500 and 1300 cm−1, the normal coordinates change considerably on deuteration. The symmetry coordinates are mixed in the normal modes of C4D6 to a much greater extent than in those of C4H6.
Solubility of Bromine in Molten Silver Bromide
Authors: Block-Bolten A. , Flengas S. N.
Published: May 2006

The solubility of bromine vapor in molten silver bromide has been measured gravimetrically. At 950 °K the solubility is about 0.4 × 10−4 g-mol of Br2 per ml of salt, or 14.6 × 10−4 g-mol of bromine per g-mol of salt. At 760 °K the solubility of bromine is about 1.1 × 10−4 mol per ml of salt, or 36.6 × 10−4 g-mol per g-mol of salt.The solutions were also investigated spectrophotometrically and absorption spectra were compared with the gravimetric results to provide calibration curves. The results indicate that bromine vapor dissolves in the molten AgBr predominantly in the form of Br3− anions. Possible molecular solubility is small and cannot be detected by the gravimetric technique. The thermodynamic properties of the solutions are reported, and indicate an exothermic partial molar heat of mixing and negative excess entropies.
Reaction of Trialkylboranes with Cyclic α-Diazo Ketones. A New Synthesis of α-Alkyl Cycloalkanones
Authors: Hooz John , Gunn Donald M. , Kono Hiromichi
Published: May 2006

An efficient procedure has been developed for the alkylation of cyclic ketones, based on the reaction of trialkylboranes with cyclic α-diazo ketones. The reaction proceeds under mild conditions, affords high yields of α-alkylated cycloalkanones, and circumvents certain difficulties inherent in previous alkylation methods.
Nucleophilic Reactivity of 4,4′-Disubstituted Diphenyl Sulfides Towards trans-Dichlorobis(pyridine)platinum(II)
Authors: Gaylor J. R. , Senoff C. V.
Published: May 2006

The kinetics of the reaction of trans-[PtCl2py2] with a series of 4,4′-disubstituted diphenyl sulfides, XC6H4SC6H4Y, have been studied at 30° in methanol. A linear free energy correlation has been obtained between the logarithm of the second order rate constant and the sum of the Hammett substituent parameters for X and Y. This result is consistent with the notion that bond making is the driving force when divalent sulfur functions as a nucleophile towards platinum(II) substrates and is consistent with the inability of 4,4′-dinitrodiphenyl sulfide to coordinate to platinum(II).
Far-infrared and Raman Spectra of Crystalline ICN
Authors: Savoie R. , Pézolet M.
Published: May 2006

The Raman and far-infrared spectra of crystalline cyanogen iodide have been recorded. High-frequency shoulders alongside the Raman bands confirm the piezoelectric nature of this solid and allow an estimate to be made of the frequencies of the longitudinal modes associated to the fundamental vibrations. Dipole derivatives calculated from these frequencies agree qualitatively with those obtained from infrared band intensity measurements.
35Cl Nuclear Quadrupole Resonance of Alkyl Chloroformates, Alkyl Acid Chlorides, and Carbamyl Chlorides
Authors: Hart R. M. , Whitehead M. A.
Published: May 2006

The 35Cl nuclear quadrupole resonance (n.q.r.) frequencies at 77 °K of twenty-two chloroformates, twenty-eight acid chlorides, two thiocarbonyl molecules, and five carbamyl chlorides are reported.
Electron Spin Resonance of γ-Irradiated Dicyandiamide
Authors: Lind G. , Kewley R.
Published: May 2006

The X-band e.s.r. spectra of single crystal and powder samples of γ-irradiated dicyandiamide, (H2N)2CNCN have been observed. The results show that three radical species are formed on irradiation at room temperature. One of these radicals, which gives a single broad line spectrum of width 8.5 G and g = 2.0040, has not been identified. The other two species are considered both to have the same chemical formula [Formula: see text] but one is a π-electron radical whereas the other is a σ-electron radical with a very large proton hyperfine splitting in the range of 73–81 G. The production of two types of radicals by radiation damage to the same —NH2 group of dicyandiamide is explained in terms of the ease of formation of π- and σ-electron radicals as influenced by geometrical considerations stemming from the hydrogen bonding in the dicyandiamide crystal.
Trimethylstannylarsines
Authors: Anderson J. W. , Drake J. E.
Published: May 2006

Tin arsines which contain an As—H bond, namely trimethylstannylarsine, bis-trimethylstannylarsine, and phenyl(trimethylstannyl)arsine, have been prepared and characterized. Alternative preparations of other trimethylstannylarsines are also discussed.
Composés de coordination de molécules soufrées. II. Complexes pseudo-tétraédriques et plan du nickel(II) avec quelques dithiole-1,2 thiones-3
Authors: Petillon François Yves , Guerchais Jacques Emile
Published: May 2006

The study of the far infrared spectral region permits one to distinguish between the pseudo-tetrahedral complexes NiI2L2 (L = R1R2C3S3 where R1 = CH3 and R2 = H, R1 = R2 = CH3, R1 = C4H3S and R2 = H) and the square planar complex NiI2L′2 (L′ = R1R2C3S3 where R1 = C6H5 and R2 = H). The electronic spectra recorded in the solid state confirm the distinction. The displacement of the band νC=S of the molecule 1,2-dithio-1-3-thione which enters the sphere of coordination is more marked in the complexes of cobalt(II) than in the corresponding nickel(II) complexes.
Kinetics of Charge Scavenging in γ-Irradiated Liquid Cyclohexane: A Comparison Between Different Ion–Electron Spacial Distribution Functions Used with Two Diffusion Approximations
Authors: Dodelet Jean-Pol , Freeman Gordon R.
Published: May 2006

The form of the spacial distribution function of ions and electrons in an irradiated liquid is not accurately known and several types of function have been assumed by different workers. The various forms are compared and used in the calculation of electron–solute reaction yields in liquid cyclohexane. Our previously used semi-empirical distribution function (YSE) and a power function (YP) give satisfactory I results, but a three dimensional, single parameter Gaussian (YG1) and a delta function (YD) do not. The prescribed diffusion approximation has also been inserted into the model for comparison with earlier work. No improvement was obtained. Whereas our previous approximations may lead to an underestimate of the geminate neutralization times, the prescribed diffusion approximation may lead to an overestimate of them.
Synthesis of Some New Phosphino Acetylenes
Authors: Carty A. J. , Hota N. K. , Ng T. W. , Patel H. A. , O'Connor T. J.
Published: May 2006

The synthesis and characterization of the new phosphino acetylenes (C6H5)2PC≡CCF3, (C6H5)2PC≡CC(CH3)3, (C6H5)2PC≡CP(C6F5)2, (C6F5)2PC≡CCH3, (C6F5)2PC≡CC6H5, (C6H5)2PC≡CP[N-(C2H5)2]2, the mixed arsine–phosphine (C6H5)2PC≡CAs(C6H5)2 and the arsino acetylene (C6H5)2AsC≡CCF3, are reported.
Reactions of Sodium N,N-Diethyldithiocarbamate and Potassium Ethyl Xanthate with some 3d Transition Metal Halides in the presence of 2,2′-Bipyridyl and 1,10-Phenanthroline
Authors: Holah D. G. , Murphy C. N.
Published: May 2006

The synthesis and some properties of ethylxanthate (Xan−) complexes, MXan2 and MXan3− (M = manganese(II) and iron(II)) are reported. Reactions between divalent metal halides (manganese, iron, cobalt, nickel, copper, and zinc) and Xan− and between the metal halides and N,N-diethyldithiocarbamate (dtc−) in the presence of nitrogen bases 1,10-phenanthroline (phen) and 2,2′-bipyridyl (bipy) are described. The major products of these reactions are complexes of the type MXan2.Base and Mdtc2.Base (with notable exceptions). In the former series with bipy, two different crystalline modifications of the manganese, iron, and cobalt complexes are formed, and copper(II) is reduced to copper(I) by Xan− in the presence of both bases. In the nickel–dtc system with bipy, Nidtc2 is produced, while with phen, the complex [Niphen3]dtc2 is formed. The latter reacts very rapidly with methylene chloride. Cudtc2 is produced from the copper(II)/base/dtc reactions.
Preparation of 7-Ethyl-2-naphthoic Acid
Authors: Stewart D. K. R.
Published: May 2006

7-Ethyl-2-naphthoic acid was synthesized by cyclization of the formylation product of ethyl-4-(4′-ethylphenyl)-butyrate and dehydrogenation of the resulting 7-ethyl-3,4-dihydronaphthoic acid.
Collisional Deactivation Rates of N2+(B2Σu+)
Authors: Mackay G. I. , March R. E.
Published: May 2006

not available
The Decomposition of Aqueous Sodium Bromite
Authors: Lee C. L. , Lister M. W.
Published: May 2006

An investigation of the rate of decomposition of aqueous sodium bromite is described. The main reactions are: 2BrO2− → BrO− + BrO3− and Br− + BrO2− → 2BrO−, followed by BrO− + BrO2− → Br− + BrO3−. The rate constants and activation parameters of the decomposition reactions are reported. As the second reaction is the reverse of that previously studied in the decomposition of sodium hypobromite, its equilibrium constant (at various temperatures) can be obtained, and hence the thermodynamic properties of aqueous bromite ions. These are briefly compared with the properties of similar ions containing bromine or chlorine.
Spectroscopic Evidence for the Formation of the Mercurous Ion in Irradiated Acetates
Authors: Eachus R. S. , Herring F. G.
Published: May 2006

The Hg(I) center has been produced by γ-irradiation both in Hg(II) doped cadmium acetate trihydrate and pure mercuric acetate. Both electron paramagnetic resonance and optical spectroscopy have been used to identify this species. The results indicate that the Hg(I) ion is produced in a covalent environment.
Pressure Effect on the Kinetics of Reaction Between Solid NaCl and ZrCl4 or HfCl4 Vapors
Authors: Pint P. , Flengas S. N.
Published: May 2006

The kinetics of reaction between single crystals of sodium chloride and zirconium tetrachloride and hafnium tetrachloride vapors, to form sodium hexachlorozirconate and sodium hexachlorohafnate, respectively, have been investigated as a function of the tetrachloride pressures at a constant temperature of 485 °C. The rate of formation of Na2ZrCl6 is kinetically more favorable. The heterogeneous reaction is diffusion controlled, with the rate of diffusion depending on the availability of Cl− vacancies.
A Differential Scanning Calorimeter Study of Phase Transitions in Alkali Metal Stearates
Authors: Ripmeester J. A. , Dunell B. A.
Published: May 2006

Differential scanning calorimeter thermograms have been obtained for the alkali metal stearates from 25 to 200 °C. Four different samples of different thermal history were studied for each soap, and differences in temperature and relative enthalpy of transitions were found to depend on the various sample histories. For lithium stearate good correlation is found between DSC and nuclear magnetic resonance (n.m.r.) results. Rubidium and caesium stearates seem to be less sensitive to thermal history than the sodium and potassium salts.
Electron Affinities from Thermal Proton-Transfer Reactions: C6H5 and C6H5CH2
Authors: Bohme D. K. , Young L. Brewster
Published: May 2006

The observation of the preferred direction of proton transfer reactions in the gas phase at 300 °K has been employed to bracket the electron affinity, e.a., of the radicals C6H5 and C6H5CH2 using well-established values for electron affinities and bond energies. The results indicate that 1.2 eV ≤ e.a.(C6H5) ≤ 1.6 eV and that 0.4 eV ≤ e.a.(C6H5CH2) ≤ 0.9 eV.
The Structure of Derivatives of [SCH3Fe(CO)3]2
Authors: Crow J. P. , Cullen W. R.
Published: May 2006

[SCH3Fe(CO)3]2 when separated into its two known isomers reacts with tertiary phosphines with retention of the sulfur-methyl group configuration. The reaction of the mixture of isomers of [SCH3-Fe(CO)3]2 with ditertiary phosphines and arsines has been studied. Some ligands give bridged complexes and others chelates: one ligand gives both. The p.m.r. and Mössbauer spectra of these complexes are discussed.
Ouverture normale d'époxydes aromatiques para-substitués par des α-mercapto esters
Authors: Berse Casimir , Coulombe Ronald
Published: May 2006

The three-membered ring of aromatic epoxides can be opened by α-mercaptoesters. The reaction products arise to a great extent by a normal opening of the ring and the substituent effect of the aromatic epoxide is of little importance.
19-Hydroxy Steroids. II. The Synthesis of 3 β,5,19-Trihydroxy-5 β-cholestane
Authors: Morand Peter , Kaufman Morris
Published: May 2006

Chemical evidence is presented in support of the structures assigned to the isomeric epoxides 4a and 5a obtained by peracid oxidation of the double bond in 3β-acetoxycholest-5-en-19-ol (2a). Reduction of 3β-acetoxy-5,6α-oxido-5α-cholestan-19-ol (4a) with lithium aluminum hydride leads exclusively to the C-5 alcohol while reduction of 3β-acetoxy-5,6β-oxido-5β-cholestan-19-ol (5a) with the same hydride results in the isolation of the C-5 and -6 alcohols in a ratio of 1:5. When an attempt was made to reduce the 5β,6β-epoxide 5a with lithium trimethoxyaluminohydride a rearrangement occurred. A structure is postulated for the compound isolated and a mechanism for its formation is discussed.
Chemistry of 2-Substituted Adamantanes. III. Mass Spectra of 1- and 2-Adamantanethiol, 2-Adamantanol, and 2-Adamantanamine
Authors: Greidanus J. W.
Published: May 2006

The mass spectra of 1- and 2-adamantanethiol (1 and 2a), 2-adamantanol (2c), and 2-adamantanamine (2d) have been studied. The isomeric thiols give almost identical spectra and loss of the sulfhydryl radical produces the most abundant ion, while the molecular ion peaks have 9 and 21% relative intensity for 1 and 2a, respectively. Elimination of H2S is an insignificant process. In the fragmentation of 2c and d, loss of H2O and NH3 as a single group occurs (metastable peaks), giving M-H2O and M-NH3 ions, both at m/e 134; this produces the base peak for 2c and the second most intense (93%) peak for 2d. Further fragmentation of these ions results in very similar peak patterns for 2c and d. The amine shows a very intense molecular ion peak (79%) and an M-1 base peak ion. The mass spectra of 2c and d are very different from those of 1-adamantanol and 1-adamantanamine.
Epimerization of Monosaccharides Under Acetolysis Conditions
Authors: Sowa Walter
Published: May 2006

Monosaccharides with a cis-configuration at C-2 and -3 readily undergo inversion at C-2 in an acetolysis medium composed of acetic acid, acetic anhydride, and sulfuric acid. The acetolysis-inversion reaction has been carried out with 2,3;5,6-di-O-isopropylidene-D-gulofuranose, 2,3;6,7-di-O-isopropylidene-D-glycero-D-gulo-heptose, 2,3-O-isopropylidene-D-ribose, D-ribose, and D-mannose using chromatography for isolation of the deacetylated epimeric products. The reaction requires a medium with a high concentration of acetic acid (ca. 90%) and appears to take place only with furanose structures. Inversions observed with the unsubstituted pyranoses D-ribose and D-mannose probably occur because of tautomerization to furanose forms. The epimerization proceeds in the direction which yields a smaller number of cis-oriented groups at C-2, -3, and -4 of the furanose forms of monosaccharides.
Nuclear Magnetic Resonance Studies of Co(II) Complexes of Thiourea and Related Ligands
Authors: Eaton D. R. , Zaw K.
Published: May 2006

A number of tetrahedral Co(II) complexes of thiourea, N-methyl thiourea, and N, N′-dimethyl thiourea have been studied by nuclear magnetic resonance (n.m.r.). All the complexes are paramagnetic and the proton resonances show large isotropic shifts in acetone-d6 solutions. The origin of these shifts is discussed. Two sets of resonances are observed for each position and this is attributed to restricted rotation about the C—N bond. The barrier for this rotation is higher in the complexes than in the free ligands. For all complexes the exchange between free and coordinated ligand is fast at room temperature but slow below −80 °C. The complexes are dissociated to a greater or lesser extent in acetone solution and equilibrium constants and other thermodynamic data are reported for this dissociation. Entropy differences are more important than energy differences in determining the extent of dissociation. It has been demonstrated that both associative and dissociative mechanisms play a part in the ligand exchange process. The relative importance of the two mechanisms differs in the various complexes.
Nuclear Magnetic Resonance Investigation of Possible Molecular Motion in Coronene, Perlene, and Triphenlene in the Solid State
Authors: Fyfe C. A. , Dunell B. A. , Rimeester J.
Published: May 2006

Broad-line nuclear magnetic resonance (n.m.r.) and spin lattice relaxation time measurements on solid coronene indicate the presence of a molecular reorientation process at 160 °K. The activation energy for the process has been determined at 5.9 kcal/mol and the nature of the motion deduced as being reorientation in the plane of the molecule. No motional processes are observed for perylene or triphenylene.The results are discussed with respect to thermodynamic data and the molecular structures.
Biosynthesis of Cernuine
Authors: Ho Y. K. , Gupta R. N. , MacLean D. B. , Spenser Ian D.
Published: May 2006

The biosynthesis of cernuine (9), an alkaloid of Lycopodium cernuum, was studied in intact plants. Specific incorporation of lysine, cadaverine, Δ1-piperideine, and pelletierine was demonstrated. The alkaloid is not a modified dimer of pelletierine, as might have been anticipated on the basis of structural relations, since only one pelletierine unit is incorporated.
Lignin and Related Compounds. III. An Improved Synthesis of 3-(4-Hydroxy-3-methoxyphenyl)-1-propanol and 3-(4-Hydroxy-3,5-dimethoxyphenyl)-1-propanol
Authors: Pepper J. M. , Sundaram G. S. , Dyson G.
Published: May 2006

3-(4-Hydroxy-3-methoxyphenyl)-1-propanol (dihydroconiferyl alcohol) (1) and 3-(4-hydroxy-3,5-dimethoxyphenyl)-1-propanol (dihydrosinapyl alcohol) (2) have been synthesized in good yields from 4-allyl-2-methoxyphenol (eugenol) and 4-allyl-2,6-dimethoxyphenol by means of the hydroboration reaction.
Pulse Radiolysis of Formamide and Formamide–Water Mixtures
Authors: Walker D. C. , Wallace S. C.
Published: May 2006

From the optical absorption spectrum observed by a sub-nanosecond pulse radiolysis method it is concluded that irradiated pure liquid formamide (dielectric constant = 109) does not yield solvated electrons with lifetimes >10−11 s. In formamide–water mixtures the hydrated electron is formed in low yield and the position of the absorption band of eaq− is not altered by changing the composition. Apparently formamide reacts much more rapidly with thermalized electrons than it does with hydrated electrons. The latter may be formed in formamide–water mixtures due to aggregates of water molecules.
Molecular Screening in Helium Molecular Ion
Authors: Wang C. M. , Musulin B.
Published: May 2006

Variational energy calculations for He2+ were performed and the results were used to evaluate a semi-empirical method for choosing orbital exponents in quantum chemical calculations.
Complexes of Cu(II), Co(II), and Ni(II) with "QPyNO"
Authors: Tong Marie , Brewer D. G.
Published: May 2006

A new ligand, 2,3-di(2-pyridine N-oxide) quinoxaline and its complexes with copper(II), cobalt(II), and nickel(II), have been prepared. A detailed investigation of the magnetic and spectral properties of these compounds has led to some tentative suggestions as to their structures.
Cyclic Imides. II. Silylsuccinimides
Authors: Janzen A. F. , Kramer E. A.
Published: May 2006

A number of silylsuccinimides containing silicon substituants —H, —CH3, —C2H5, —CH=CH2, —CH2CH=CH2, —C6H5, as well as disuccinimides, have been prepared and characterized by i.r., n.m.r., and mass spectrometry. The results are compared with previous studies of silylphthalimides.
The Meyer Reaction of Phenylnitromethane in Acid. III. The Tautomerization to the aci-Form
Authors: Edward J. T. , Tremaine P. H.
Published: May 2006

The rate-acidity profiles for the Meyer rearrangement–hydrolysis of phenylnitromethane in sulfuric, perchloric, and hydrochloric acid show a maximum near 3 M acid. Ring-substituted phenylnitromethanes also show a maximum in their rate profiles, at slightly different acid concentrations. These maxima arise because the slow formation of the aci-form is followed by two competing reactions: fast tautomerization back to the nitro-form, and fast rearrangement–hydrolysis to the Meyer products. The rearrangement is rate-limiting in dilute acid and is acid-catalyzed, causing the rate increase. In more concentrated acid, the rate-limiting step is the nitro to aci tautomerization, which is not acid-catalyzed, and which goes more slowly as the activity of water decreases.The tautomerization was studied by means of primary and solvent deuterium isotope effects, and was found to occur through proton abstraction by water, through a transition state closely resembling the products.
Preparation de quelques cyclohexène-2 diones-1,4 et de leurs dérivés
Authors: Savoie J. Y. , Brassard P.
Published: May 2006

The osmic acid catalyzed oxidation of quinones has yielded for the first time to our knowledge the monomers of some cis-5,6-dihydroxycyclohex-2-ene-1,4-diones. Toluquinone and o-xyloquinone give mixtures of the two possible isomers. Observation of the n.m.r. spectra suggests that this new class of compounds are in general conformationally more mobile than quinonedihalides. The conversion of cyclohex-2-ene-1,4-diones into oximes allows the easy evaluation of all the important coupling constants.
Ferrocene Studies. VII. 1,2-Disubstituted Ferrocenes
Authors: Moynahan E. Bradley , Popp Frank D.
Published: May 2006

Further examples of the utility of the 2-lithiation of N,N-dimethylaminomethylferrocene are presented.
Nuclear Magnetic Resonance Studies of Multi-site Chemical Exchange. II. Hindered Rotation in N,N-Dimethyl Carbamyl Fluoride
Authors: Reeves L. W. , Shaw K. N.
Published: May 2006

The matrix formulation of the Bloch equations including chemical exchange reported earlier is extended to include indirect spin–spin coupling in first-order spectra. The ABX (JAB = 0) spin system is treated in detail and particular attention is paid to the determining effect on the nuclear magnetic resonance (n.m.r.) lineshapes of the relative signs of the coupling constants JAX and JBX. The hindered rotation for N,N-dimethyl carbamyl fluoride in CCl4 as solvent has been studied using a complete 1H n.m.r. lineshape analysis and the activation parameters obtained are: ΔG≠ = 18.1 ± 0.6 kcal mol−1, ΔH≠ = 17.7 ± 0.6 kcal mol−1, and ΔS≠ = −1.4 ± 2.1 cal deg−1 mol−1 at 25 °C.The complete lineshape fits give very precise values of the relative shifts (16.5 mol% in CCl4) of the methyl groups and of the coupling constants JAX (0.30 ± 0.05 Hz) and JBX (0.80 ± 0.05 Hz) at all temperatures. A 40% change in JBX (1.10 ± 0.05 Hz) is observed in neat DMCF from a lineshape fit at −15 °C. The origin of changes in chemical shifts with temperature and JBX with solvent is discussed.
The Nickel(II)–γ-Picoline–Perchlorate Complex System
Authors: Sun M. S. , Brewer D. G.
Published: May 2006

not available
Nuclear Magnetic Resonance Studies of the Solution Chemistry of Metal Complexes. II. Protonation of the Peptide Linkages of Bis(glycylglycinato)cobaltate(III)
Authors: Rabenstein Dallas L.
Published: May 2006

Protonation of bis(glycylglycinato)cobaltate(III) in acidic aqueous solutions has been investigated by proton magnetic resonance spectroscopy. Chemical shift measurements indicate that the site of protonation is the peptide oxygen rather than the Co(III)-coordinated, deprotonated peptide nitrogen as previously proposed, and that the two peptide linkages are protonated in a stepwise fashion rather than simultaneously. Equilibrium constants for the stepwise protonation equilibria have been derived from the n.m.r. data. The equilibrium constant for the first protonation step has also been determined by pH titration.
The Temperature Dependence of Transition State Volumes in Hydrolysis Reactions
Authors: Mackinnon Moyra J. , Hyne J. B.
Published: May 2006

The temperature dependence of the transition state volume, [Formula: see text], in a number of hydrolysis reactions is derived from pressure/rate data and partial volume temperature dependence. The values obtained for [Formula: see text] vary from near zero for p-methylbenzyl chloride to about 0.3 ml mol−1 deg−1 for isopropyl bromide. The interpretation of the experimental and derived values for these hydrolyses is discussed in terms of charge development with accompanying solvation effects about the solute.
Special Catalytic Power of Enzymes: Some Evidence from Model Systems
Authors: Bowden Keith , Last A. M.
Published: May 2006

Evidence from model systems for enzyme catalysis is discussed. These models involve neighboring group participation by carbonyl or carbon-acid groups, and indicate the important roles of proximity, strain, and orientation as potential sources of the special catalytic power of enzymes.
Per-deuteration of t-Butanol in Mildly Acidic Deuterium Oxide
Authors: Hocking Martin B.
Published: May 2006

Heating a solution of t-butanol in acidified deuterium oxide under slight pressure has yielded 85% per-deuterated t-butanol. At atmospheric pressure normal isobutylene was produced. Isobutylene could not be hydrated in good yield by this method. A number of related alcohols were resistant to exchange by this method, but one of them, 1-methylcyclohexanol, gave nearly complete dehydration without deuterium incorporation.
Electron Spin Resonance Studies of Radiation Damage. Part. V. γ-Radiolysis and Photolysis of Aqueous Alkaline Glasses Containing Acetonitrile. The Photo Conversion of an Imino Radical to an Alkyl Radical at 77 °K
Authors: Sargent F. P. , Bailey M. G.
Published: May 2006

The reactions of γ and photochemically produced electrons with acetonitrile in 8 M sodium hydroxide glasses at 77 °K have been re-investigated. The results differed from those previously reported and a novel photo-conversion of an imino radical to an alkyl radical was found. These results lead to a unified interpretation of (seemingly discrepant) observations on polar and nonpolar glasses.