bluuebunny/crossref_metadata_2025 huggingface dataset:
The Crystal and Molecular Structure of Acetamidopentaamminecobalt(III) Perchlorate. A Conjugate Base of Nitrogen Bonded Acetamide
Authors: Schneider Michael Louis , Ferguson George , Balahura Robert James
Published: May 2006

The crystal and molecular structure of acetamidopentaamminecobalt(III) perchlorate, [CH3CONHCo(NH3)5]2+•2ClO4−, has been determined from three-dimensional X-ray data obtained by diffractometer methods. The crystals are monoclinic, space group [Formula: see text] with four formula units in a unit cell of dimensions a = 13.250(6), b = 10.318(6), c = 10.676(5) Å, β = 98.34(3)°. The structure has been refined by block-diagonal least-squares methods with anisotropic thermal parameters to a final residual R of 0.055 for 1340 observed reflexions. The crystal structure consists of discrete octahedral cations and tetrahedral perchlorate anions. The Co—N (amide) distance is short (1.911(8) Å) while the trans Co—N (ammine) bond is long (1.994(8) Å) compared to the equatorial Co—N distances which average 1.963(13) Å. The bond distances in the amide group, C—O 1.267(12) Å and C—N 1.339(12) Å, indicate that a delocalized system plays an important role in the ground state structure of the cation.
Spectroscopic Properties of a Series of Vinyl–Platinum Complexes
Authors: Appleton T. G. , Chisholm M. H. , Clark H. C. , Manzer L. E.
Published: May 2006

Nuclear magnetic resonance, infrared, and Raman data are given for the series trans-PtRXQ2 and trans-[PtRQ2L]+, where [Formula: see text], Q = (PCH3)2C6H5, L = neutral ligand, and Z = anionic ligand. The coupling constants between 195Pt and the trifluoromethyl 19F nuclei and between 195Pt and the vinyl proton Hv both correlate linearly with [Formula: see text] for the corresponding methylplatinum complexes. The results are explained in terms of platinum hybridization in the Pt—C bond dominating the coupling constant.
Photooxidation of Azomethane
Authors: Shortridge Robert , Heicklen Julian
Published: May 2006

The photooxidation of azomethane has been studied at 25 °C and O2 pressures up to 100 Torr in order to ascertain quantitatively the fate of CH3O2 and CH3O radicals by measuring the quantum yields of CH3OOH and CH3OOCH3 production. The generally accepted reactions include[Formula: see text]The appropriate rate constant ratios were found to be: k5/k31/2k41/2 = 0.31, k4a/k4b = 8.9, and k6/k41/2 = 0.021 M−1/2 s−1/2. The estimated accuracy of these values is ± 30%.
Charge Density Distribution in Vanadium Complexes
Authors: Eaton D. R. , Chua K. L.
Published: May 2006

An empirical method for investigating the effect of substituents on the charge distribution of transition metal complexes is presented. This method is based on the measurement of n.m.r. chemical shifts of paramagnetic compounds and is applied to a series of V(III) complexes. Measurements are reported on the sixteen isomers which result from the systematic replacement of CH3 groups by CF3 groups in V(III) trisacetylacetonate. Ninety-nine of the possible 100 1H and 19F chemical shifts have been measured. Substituent shifts of several thousand Hz are observed and have been interpreted using a model invoking charge redistribution in both σ and π orbitals. Similar experiments involving phenyl substituents are also reported. The model adopted enables the data to be fitted with a precision of around 2%. The substituent parameters derived from this model are discussed in terms of changes in electron density and the results compared with substituent effects in aromatic compounds. The important differences arise from the three dimensional nature of metal complexes which leads to interactions between the σ and π electrons of a type not found in simple aromatic compounds. The significance of these results to the rationalization of ligand effects on ligand exchange and catalytic reactions is discussed.
The Infrared and Raman Spectra of Powdered and Single-Crystal Barium Chlorate Monohydrate and -deuterate
Authors: Bertie John E. , Heyns Anton M. , Oehler Oscar
Published: May 2006

The infrared and Raman spectra of polycrystalline and single-crystal Ba(ClO3)2•H2O and Ba(ClO3)2•D2O have been obtained. The observed bands have been assigned to the various Davydov components of the intramolecular modes and colattice modes. For the water molecule, all of the fundamentals of H2O, HDO, and D2O have been located, the anharmonicities of the bending modes have been determined, and those of the stretching modes are essentially the same as for water vapor. The intermolecular coupling is very weak. The effective harmonic force field for the water molecules has been calculated. The stretch–stretch interaction constant is much smaller than for water vapor, reflecting a smaller separation of the asymmetric and symmetric stretching modes. The intermolecular vibrations of the water molecules have been located. For the chlorate ions, in spite of the disorder due to the 37Cl, the spectra can be interpreted in terms of unit cell modes, albeit as a first approximation. The isotope shift of the symmetric Cl—O stretching mode appears to be unusually large. The far-infrared spectra have been tentatively assigned to translational and rotational vibrations involving the Ba2+ and ClO3− ions.
Proton Transfer Kinetics in Medium-strong Inorganic Acids
Authors: Hodgkin David Charles , Kruus Peeter
Published: May 2006

A method of obtaining relative and absolute rate constants for proton transfer equilibria is described. It is suitable for equilibria of the type[Formula: see text]in dilute (< 0.1 M) solutions of medium strong inorganic acids. To obtain absolute values of kd, kr it is necessary to know the value of ΔV0 for the equilibrium. Ultrasonic absorption data for aqueous solutions of H3PO4, H3AsO4, and H2SO4 at 20, 10, and 0 °C are presented together with data at 20 °C for H3PO3, H2SeO3, HIO4, NaHSO4, KHSO4, and NH4HSO4. From analysis of the concentration dependence of the excess absorption, values of Ka are calculated for these acids, and values of kd, kr for those where ΔV0 is available. The Ka obtained are in reasonable agreement with literature values except for HIO4 and H2SeO4. The absolute values of kr for H3PO4, H3AsO4, and HSO4− indicate that the diffusion controlled recombination process postulated is complete when the ions are about 15 Å from each other.
Rationalization of Carbon-13 Magnetic Resonance Spectra of Yeast Mannans and Structurally Related Oligosaccharides
Authors: Gorin P. A. J.
Published: May 2006

The carbon-13 magnetic resonance (c.m.r.) spectra of oligosaccharides, derived from yeast mannans by partial acetolysis, contain signals at δC 93.1–105.4 (C-l's) and 79.2–81.2 (C-2's and/or C-3's substituted by mannopyranosyl units). They were assigned on the basis of (a) carbons deshielded by attached mannopyranosyl units have resonances at lower field than those of unsubstituted carbons and (b) comparison under carefully controlled conditions of the relative sizes of signals of comparable carbons, which have the same resonances, in members of two different homologous series of oligosaccharides. The c.m.r. spectra of certain mannans containing (1 → 6)-linked α-D-mannopyranose main-chains could then be rationalized since they have many signals with resonances in common with those of oligosaccharides, which are derived by partial acetolysis and contain the structures of the side chains.
The Use of Polymer Supports in Organic Synthesis. II. The Syntheses of Monoethers of Symmetrical Diols
Authors: Wong Jack Y. , Leznoff Clifford C.
Published: May 2006

An insoluble polymer support system was used as a unique method of blocking one functional group of a completely symmetrical difunctional compound. The monotetrahydropyranyl and monotrityl ethers of the symmetrical diols, HO—(CH2)n—OH, where n = 2,4,6,8, and 10, were prepared. Reaction conditions for the preparation of the monotetrahydropyranyl ether of 1,10-decanediol were optimized.
Investigations of Substituent Effects by Nuclear Magnetic Resonance Spectroscopy and All-valence Electron Molecular Orbital Calculations. II. 4-Substituted α-Methylstyrenes and α-t-Butylstyrenes
Authors: Hamer G. K. , Peat I. R. , Reynolds W. F.
Published: May 2006

not available
Reversible Inhibition of the Esterase Activity of Carboxypeptidase A by Carboxylate Anions
Authors: Bunting John W. , Myers Chester D.
Published: May 2006

Reversible inhibition of the hydrolysis of O-(hippuryl)-L-3-phenyllactic acid by carboxypeptidase A has been studied for 26 carboxylate ion inhibitors at 25°, pH 7.5, and ionic strength 0.2 (NaCl). Competitive inhibition, partially competitive inhibition, and mixed inhibition kinetics were observed. Within homologous series, strictly competitive inhibition by the lower members gave way to partially competitive inhibition with higher members, while homologs having very large hydrocarbon moieties displayed mixed inhibition kinetics. Partially competitive inhibition in this system is not consistent with a scheme involving only 1:1 enzyme–inhibitor complexes; rather, higher order enzyme–inhibitor complexes will be necessary for a complete description of the inhibition mechanism.Inhibition constants (log Ki) for the aliphatic carboxylate ions which are strictly competitive inhibitors, are closely correlated linearly with Hansch's π-parameter for hydrophobicity. This quantitatively confirms the importance of hydrophobic interactions between carboxypeptidase A and inhibiting ions. Carboxylate ions containing aromatic rings are less effective inhibitors than expected on the basis of the π-parameters of their hydrocarbon moieties. The dependence of log Ki on π in this system is unusually strong for a binding phenomenon, and suggests that an inhibitor-dependent conformational change may also be involved.
Ring Opening of Dihydro-1,4-oxathiins
Authors: Corbeil Maurice Armand , Curcumelli-Rodostamo Michael , Fanning Robert James , Graham Bruce Allan , Kulka Marshall , Pierce James Benjamin
Published: May 2006

Acid hydrolysis of 5,6-dihydro-2-methyl-1,4-oxathiin-3-carboxanilide gives 2-(2-hydroxyethylthio)-acetoacetanilide enol. 3-Carbonyl-substituted 5,6-dihydro-1,4-oxathiins were found to undergo ring cleavage by nucleophilic nitrogen attack on C-2. Thus the following reactions were observed: 3-acetyl-5,6-dihydro-2-methyl-1,4-oxathiin on treatment with hydrazine gives 4-(2-hydroxyethylthio)-3,5-di-methylpyrazole, instead of the hydrazone. The 1,4-oxathiins, N-(5,6-dihydro-2-methyl-1,4-oxathiin-3-ylcarbonyl)-N′-phenylurea and 5,6-dihydro-2-methyl-1,4-oxathiin-3-carboxylic acid hydrazide rearrange to give 5-(2-hydroxyethylthio)-6-methyl-1-phenyluracil and 4-(2-hydroxyethylthio)-3-methyl-2-pyrazolin-5-one, respectively. Finally, treatment of 5,6-dihydro-2-methyl-1,4-oxathiin-3-carbonyl chloride with 2-aminopyridine and with 2-aminopyrimidine affords 4H-3-(2-hydroxyethylthio)-2-methyl-pyrido[1,2-a]pyrimidin-4-one and 4H-3-(2-hydroxyethylthio)-2-methylpyrimido[1,2-a]pyrimidin-4-one, respectively, as the predominant products.
A Study on the Kinetically Controlled Cyclization of 6-Deoxy-3-O-methyl-6-nitro-D-glucose and-L-idose, and the Preparation of Optically Active Nitroinositol Derivatives
Authors: Kovář Jan , Baer Hans H.
Published: May 2006

The cyclization (internal Henry addition) of 6-deoxy-3-O-methyl-6-nitro-D-glucose (1) and-L-idose (2) was investigated with respect to the sequence in which stereoisomeric deoxynitroinositol methyl ethers are formed from each. It was found that, under conditions of kinetic control, the primary products generated from 1 are the nitronate 4′ (that corresponds to the epimeric deoxynitroinositols 4 and 5 having the epi-3 and muco-3 configurations, respectively) and the nitronate D-6′ of optically active 1-deoxy-4-O-methyl-1-nitro-L-myo-inositol (L-6). They are formed in approximately equal proportions. Ensuing thermodynamically controlled processes lead to racemization of L-6 and formation of the scyllo isomer 3 at a relatively slow rate. The cyclization of 2, found to be faster than that of 1, gave as primary products the enantiomeric nitronate D-6′ and the nitronate 3′ in a ratio of about 4:1. The nitronate 4′ arose by subsequent epimerization. The optically active compounds D-6 and L-6 were isolated in pure, crystalline form.
13C Nuclear Magnetic Resonance Studies. 32. The 13C Spectra of Several Norbornyl Derivatives
Authors: Stothers J. B. , Tan C. T. , Teo K. C.
Published: May 2006

The 13C n.m.r. spectra of several norbornyl derivatives have been recorded to examine the variation of 13C shieldings with molecular geometry. Since it is well established that nonbonded interactions between vicinal carbon nuclei lead to pronounced upfield shifts, the so-called γ effects, series of methyl-substituted norbornanes, norbornenes, norbornan-2-ones (norcamphors), and norborn-5-en-2-ones were prepared as model systems having a variety of γ interactions between vicinal methyl groups. The observed shifts of these methyl carbons are considered in terms of the dihedral angle relating the vicinal nuclei. The use of specific deuteration for unequivocal signal assignments of carbons geminal and vicinal to the site of deuteration is illustrated.
Reactions of Ozonides. XI. A 14C Tracer Study of the Ozonolysis of Ethylidenecyclohexane in Cyclohexanone
Authors: Kerur Dundappa R. , Diaper Dennis G. M.
Published: May 2006

Using 14C labelling of cyclohexanone or ethylidenecyclohexane, examination of the products of ozonolysis of the alkene in the presence of the ketone reveal 6-hexanolide to be initially formed in < 1% yield. Cyclohexanone peroxides are the major products from ethylidenecyclohexane ozonized in cyclohexanone. Carbonyl-modified alkene ozonolysis is therefore suggested to be explicable by the Criegee mechanism, and it is unnecessary to invoke Baeyer–Villiger interactions. Ozonide formation is not totally suppressed by cyclohexanone.
The Effects of Potassium Fluoride and Potassium Iodide on the Expansivity of Water
Authors: Burns Noel M.
Published: May 2006

An examination of the specific volumes of KF and KI solutions over the concentration range 0.1 to 2.0 m and over the temperature range 0° to 95° has led to the conclusion that the partial molal expansivity of the salts is due almost entirely to changes in the electrostrictive processes in water with temperature and are not due to changes in the structural effects of the salts on the bulk water with changing temperature. However, structural effects are considered to be of significant magnitude below 70°.
Hexamethylazoxybenzene. Structure, Basicity, and Rearrangement
Authors: Cox Robin A. , Buncel Erwin
Published: May 2006

2,2′,4,4′,6,6′-Hexamethylazoxybenzene (1) has been prepared and characterized. The u.v. spectrum is indicative of large distortion from coplanarity. 1 is only slightly more basic than azoxybenzene despite expectations due to electronic effect of the methyl substituents. Two factors are considered responsible for this: steric inhibition of resonance in the unprotonated species and steric hindrance to hydration in the conjugate acid.Rearrangement of 1 in moderately concentrated sulfuric acid gives rise to the alcohol 4-hydroxymethyl-2,2′,4′,6,6′-pentamethylazobenzene (6). A Bamberger type phenolic product which would result from methyl migration is not observed. Possible reaction mechanisms are given.
The Synthesis of (±)-Cordrastine. A New Route to the Phthalideisoquinoline System
Authors: Smula V. , Cundasawmy N. E. , Holland H. L. , MacLean D. B.
Published: May 2006

The phthalideisoquinoline system has been synthesized from substituted 2-phenyl-1,3-indandiones as starting materials. The key step in the synthesis is the rearrangement of the spirobenzylisoquinoline ring system to the phthalideisoquinoline system. The diastereomeric cordrastines, I and II, have been synthesized by this method and their relative configurations have been established by comparison of their p.m.r. spectra with those of phthalideisoquinoline alkaloids of known configuration.
Preparation of 2-Methoxytetrahydropyran-3-one from Halogenated Dihydro- and Tetrahydropyran Precursors
Authors: Roff J. E. , Brown R. K.
Published: May 2006

The reaction of 5-halo-3,4-dihydro-2H-pyran with halogen and sodium methoxide gives in good yield the corresponding 3,3-dihalo-2-methoxytetrahydropyran. The latter, upon treatment with aqueous sodium hydroxide or sodium methoxide in methanol failed to provide 2-methoxytetrahydropyran-3-one but instead gave the 3-halo-2-methoxy-5,6-dihydro-2H-pyran. The ketone, 2-methoxytetrahydropyran-3-one was obtained by the treatment of 5-chloro-3,4-dihydro-2H-pyran with m-chloroperoxybenzoic acid followed by the addition of sodium methoxide.Attempts to prepare the 3,3-dibromo-2-methoxytetrahydropyran by the reaction of 3-bromo-2-methoxytetrahydropyran with bromine were unsuccessful, but gave the ring cleavage product, methyl 2,5-dibromopentanoate.
Recombination of Iodine Atoms by Flash Photolysis over a Wide Temperature Range. V. I2 in CF4, SF6, CO2, Ne, Kr
Authors: Chang Hen Won , Burns George
Published: May 2006

Recombination rate constants for iodine atoms in CF4, SF6, CO2, Ne, and Kr were studied by flash photolysis. The results can be summar ized as follows:[Formula: see text]These rate constants are compared with those available in the literature, and analyzed, qualitatively, in terms of current theories of recombination reactions.
The Specific Activity of Silica Supported Platinum for the Catalysis of Hydrogen–Methane Deuterium Exchange
Authors: Sagert Norman Henry , Pouteau Rita Mary Louise
Published: May 2006

Rate data are reported as a function of temperature for the exchange of D2 with CH4 over a number of platinum–silica catalysts. Two different methods of preparing catalysts, impregnation and ion exchange, were used to get two series of metal particle sizes. Within each series, the particle size was increased by sintering batches in air at temperatures to 800 °C. These methods produced platinum particles ranging from 0.9 to 10 nm diameter. The metal surface areas were measured by hydrogen chemisorption and, where possible, by X-ray diffraction and electron microscopy.The specific rate coefficients or rate coefficients per unit surface area of platinum varied by a factor of up to 40 within each series and reached a maximum for sintering temperatures of about 500 °C. The maximum specific rate coefficients for CH4 conversion at 200 °C, and total pressure of 60 kN m−2, were 1.3 and 1.9 × 10−6 mol CH4 m−2 s−1 for the ion-exchanged and impregnated catalysts respectively. Activation energies were in the range 60 to 100 kJ mol−1. Since a relatively small change in specific rate coefficient was noted between the two series as compared to the changes within each series, no large effect of particle size on the specific rate coefficient was demonstrated. The different specific rate coefficients within the series are ascribed to other effects of sintering, particularly the formation of the lower energy Pt(111) surface. Some evidence was noted for a particle size effect in the distribution of products, with more multiple exchange being observed for the smallest particles.
Restricted Internal Rotation in 1-Arylhydantoins, 3-Arylhydantoins, and 3-Aryl-2-Thiohydantoins: Reversal of the Effective Sizes of Methyl and Chlorine
Authors: Colebrook Lawrence D. , Giles H. Gwynne , Granata Alessandro , Icli Siddik , Fehlner James R.
Published: May 2006

In 1-arylhydantoins an o-methyl group is effectively larger than an o-chloro substituent in restricting rotation about the aryl-C—N bond, whereas in 3-arylhydantoins and 3-aryl-2-thiohydantoins the reverse order of sizes is observed. This difference is attributed to repulsion between the chlorine atom and a carbonyl oxygen atom in the torsional transition state of the 3-aryl compounds.
The Racemization of Sulfonium Salts. III. The Racemization of Arylsulfonium Salts
Authors: Darwish David , Scott Christopher E.
Published: May 2006

The rate constants for racemization by inversion of a variety of monoaryl- and diarylsulfonium salts are reported. There is a marked steric effect upon the rate of the racemization reaction. An estimate is made of the half-life for racemization of acyclic optically active triarylsulfonium salts.
The Reactions of Active Nitrogen with Simple Alcohols
Authors: Roscoe John M. , Roscoe Sharon G.
Published: May 2006

The reactions of active nitrogen with CH3OH, C2H5OH, n-C3H7OH and iso-C3H7OH have been studied as a function of temperature. The rate constants for these reactions fit the following expressions:[Formula: see text](Activation energies are in kJ/mol. Rate constants are in 1 mol−1 s−1.)Experiments with CH3OH, CH3OD, and CD3OD indicate a small primary isotope effect for OH and a secondary isotope effect for CH. This, with other data, implies that abstraction of a H atom from the alcohol is not an important initial step.Consumption of N atoms ranged from 4.7 to 7.1 times the alcohol consumed. With the exception of the reaction of active nitrogen with iso-C3H7OH, the only detectable stable reaction product was HCN. Intervention of O atoms as intermediates appears to be important in all the reactions. In the reaction of active nitrogen with iso-C3H7OH, acetone, and acetonitrile were also found as products in amounts of about 26% and 14% respectively of the HCN yield. These products appear to arise through O atom intervention.Mechanisms for the reactions and the nature of the activated state in the initial step are discussed.
Arrhenius Parameters for Reaction of tert-Butylperoxy Radicals with some Hindered Phenols and Aromatic Amines
Authors: Howard James Anthony , Furimsky Edward
Published: May 2006

The reaction of tert-butylperoxy radicals with some 2,6-di-tert-butyl-4-substituted phenols, α-naphthol, α-naphthylamine, and N-phenyl-α-naphthylamine has been studied by following the change in radical concentration with time using an e.p.r. spectrometer. Rates of radical decay were first-order in both reactants and were not influenced by the presence of tert-butyl hydroperoxideAbsolute values of the second-order rate constants were measured from −35 to −100° and the preexponential factors and activation energies fell in the range 104–105 M−1 s−1 and 0.5–1.0 kcal mol−1. Rate constants for deuterated phenols (OD) and aromatic amines (ND) were an order of magnitude lower than for the corresponding light compoundsThere was no evidence for quantum mechanical tunneling in these hydrogen atom transfer reactions and it would appear that the activation parameters are low because reaction initially involves the formation of a hydrogen bonded peroxy radical – phenol (or aromatic amine) complex, followed by the transfer of a hydrogen atom within the complex
Investigation of the Polymers Formed in Reactor Irradiated Aniline and Pyridine
Authors: Barakat Mahmoud F. , Abdelkerim Fawzi M.
Published: May 2006

In reactor irradiated aniline or pyridine most of the radiocarbon generated by the 14N(n,p)14C reaction was found preferentially localized in a polymer-like material, brown in color, frequently lustrous and constituting 15–30% of the initial amount of the irradiated material. This stimulated us to try to obtain an idea about the chemical groupings existing in these highly radioactive materials and thereafter to deduce their possible formation pathways.By comparing the i.r. spectra of these polymers with those of the corresponding pure compounds it was possible to detect some changes in the spectra on polymerization and consequently it was possible to identify some basic structural groups existing. Based on these findings some polymerization reaction mechanisms have been suggested. In general, polymer formation was assumed to take place through the formation of polymerization centers produced by the rupture of the aromatic rings to give highly unsaturated fragments and radicals. These are capable of adding different radicals and fragments formed in the irradiated material by radiolysis or by the action of energetic recoil atoms. Cross linking between individual polymer chains was observed. The preferential localisation of 14C in the polymer fraction could be attributed to the great capacity of the recoil atoms to form reactive secondary species such as 14CH3•, 14CH2••, or 14CH••• which participate in polymer formation.
Studies on Metal Hydroxy Compounds. XIV. Thermal Analyses, Calorimetry, and Decomposition Kinetics of Heterocationic Hydroxy Chloride Compounds
Authors: Leu Ah-Dong , Ramamurthy Palepu , Secco Etalo A.
Published: May 2006

Studies were carried out on two series of mixed metal hydroxy chloride compounds of the type xMe(OH)2•yMCl2 where Me = Cd, Cu and M = Mn, Co, Ni, Cu, Zn, Cd, Mg, or Ca.Thermal analyses for the Cd–M series reveal that the initial mode of decomposition involves a dehydroxylation step with a concomitant metathetical reaction between MCl2 and CdO. The compound CdCl2•2CdO is formed and decomposes at higher temperature leading to the eventual volatilization of CdCl2. The kinetics of thermal decomposition follow a simple first-order rate equation. The sole exception to this general pattern of behavior is the Cd–Zn compound.The initial mode of thermal decomposition of the Cu–M series compounds follows a parallel pattern described for the Cd–M series. The kinetic data for the Cu–M series are fitted into three groups: (i) phase boundary control embracing the contracting sphere and contracting plate model equations, (ii) A-E type equation with n = 2, and (iii) first-order rate equation.
The Question of Conformational Restriction in the trans-Cyclononene Ring of Caryophyllene
Authors: Warnhoff E. W. , Srinivasan V.
Published: May 2006

The possibility that the barrier to rotation of the trans double bond within the nine-membered ring of caryophyllene might be high enough to prevent the interconversion of conformers 2 and 3 near room temperature has been examined. Contrary to earlier reports, it has been found that two trans epoxides are formed on peracid epoxidation of caryophyllene and hence both conformers are present. Attempts to determine whether 2 and 3 are interconverting near room temperature were inconclusive.
Effect of Electron Scavenger on the γ-Radiolysis of Gaseous Propane at High Densities
Authors: Nishikawa Masaru , Yamaguchi Yoh-ichi , Fujita Kazuo , Kon Kazunori , Okamoto Tetsuro
Published: May 2006

Hydrogen formation from γ-radiolysis of gaseous propane at 120 ± 1 °C was studied as the function of density in the range from 0.1 to 0.5 g/ml. G(H2) gradually decreased with density from 8.0 at 0.12 g/ml towards the liquid-phase value of 6.4 at room temperature. G(H2) in the presence of SF6 showed similar decrease from 3.9 to 3.0. The decrease was discussed in comparison to the abrupt drop in G-values from the radiolysis of ammonia at high density (11). The separation distances of ion–electron pairs were estimated from the analysis of the electron scavenging reaction.
Electron Spin Resonance Studies in Aqueous Solution: Fragmentation of Radical Intermediates Derived from β-Amino Alcohols
Authors: Foster Terry , West Paul Ronald
Published: May 2006

In acidic aqueous solution, oxidation of the β-amino alcohols [Formula: see text], I, and [Formula: see text], II, (R = H, alkyl) using the Ti(III)–H2O2 flow technique gave the radicals [Formula: see text], and [Formula: see text]. The spectrum of [Formula: see text] shows restricted rotation about the C1—C2 bond assigned to intramolecular hydrogen bonding.Under neutral conditions, oxidation of I gave the spectrum of •CH2CHO, and of II the acetonyl radical •CH2COCH3. It is proposed that elimination occurs by deprotonation of the abstraction radical in a hydrogen-bonded conformation, followed by rapid fragmentation to yield the α-carbonyl radical.
An Electron Spin Resonance Study of the Reaction of Nitrogen Dioxide with Metal Acetylacetonates
Authors: Wolodarsky William H. , Faniran Joshua , Wan Jeffrey K. S.
Published: May 2006

The reaction of nitrogen dioxide with several metal acetylacetonates was studied by electron spin resonance. Those metal complexes that have stable lower oxidation state, (i.e. Cu(II), Fe(III), Co(III), and VO(II)) react to form iminoxy radicals, while those metals not readily reduced (i.e. Zn(II), Cr(III), and Ce(III)) do not give iminoxy radicals. On the basis of the e.s.r. results, a simple mechanism was proposed to account for the formation of iminoxyacetylacetone radicals. A low temperature study of the e.s.r. spectra of the iminoxy-Cu(II)hexafluoroacetylacetonate suggested that a π-complex is formed between the organic radical and the Cu(II) compound.
A Proton Magnetic Resonance Study of l,4-Dichlorobenzene-13C Partially Oriented in Nematic Phases
Authors: Burnell E. E. , Diehl P. , Niederberger W.
Published: May 2006

The p.m.r. spectra of 1,4-dichlorobenzene-(13C and 12C) partially oriented in nematic phases have been measured and analyzed, and the geometry of the molecule has been determined. The angle [Formula: see text] is found to be 119.4° and [Formula: see text] 120.3°. The JCH are determined using spectra of samples with differing degrees of orientation.
Vibrational Spectra of the Hexacarbonyl Manganese(I) Cation
Authors: McLean R. A. N.
Published: May 2006

The infrared and Raman spectra of the hexacarbonylmanganese cation as Mn(CO)6+ PF6− were assigned by comparison with other hexacarbonyl species. The CO stretching force constants for Mn(CO)6+ and Re(CO)6+ as indicated by the CO stretching vibrational frequencies are not significantly different. However, the Mn—C force constant in Mn(CO)6+ is likely to be considerably less than the Cr—C force constant in Cr(CO)6, whereas Re(CO)6+ and W(CO)6 have similar values. It is postulated that, although Mn(CO)6+ has equal metal–carbon σ bonding to Re(CO)6+, the metal-carbon σ bonding is less for Mn(CO)6+.
The γ-Radiolysis of Ethane. III. The Effect of Density on Ion Scavenging Reactions above the Critical Temperature
Authors: Holland Patrick T. , Stone John A.
Published: May 2006

The radiolysis of ethane has been studied over the density range 0.0018–0.5 g cc−1 at a temperature just above the critical point. The variations of product yields with increasing density are consistent with increasing collisional stabilization of excited species. Electron scavenging by sulfurhexafluoride in ethane at 0.275 g cc−1 is accurately described by an expression used for liquid phase scavenging with Gfree ions = 0.65. At 0.052 g cc−1 a much higher yield of free ions is observed and at high sulfurhexafluoride concentrations there is a sensitized decomposition of ethane.Ammonia-d3 scavenges ions at all densities but in the region around 0.07 g cc−1 a mechanism operates which produces more than one hydrogen molecule per ion scavenged. The freely diffusing ions do not appear to be readily scavenged by ammonia-d3.
Titanium(IV) Chloro-Derivatives of Strong Monobasic Acids
Authors: Dalziel J. R. , Klett R. D. , Yeats P. A. , Aubke F.
Published: May 2006

The interaction of the monobasic protonic acids HSO3F, HSO3CH3, HPO2F2, and HCO2CF3 with titanium(IV) chloride at room temperature is studied with either the acid or the metal halide in excess. Whereas with the acid in excess products of the type TiCl2Y2, with Y = oxyacid group, are formed, the excess of TiCl4 results in the formation of TiCl3.33(SO3F)0.66, TiCl3SO3CH3, and again TiCl2(PO2F2)2 and TiCl2(CO2CF3)2.The first two compounds are also obtained by ligand redistribution reactions with TiCl4 in excess, e.g.[Formula: see text]in quantitative yield.Vibrational spectra for the PO2F2, SO3F and the previously reported SO3CF3 derivatives are interpreted in terms of hexacoordinated titanium and generally bi- or tridentate oxyacid groups. In TiCl3.33(SO3F)0.66 evidence for a highly unusual tetradentate SO3F group is presented, where coordination to titanium involves all three oxygens as well as fluorine.
Chemically Induced Dynamic Electron Polarization. IV. The Photolysis of 1,4-Naphthoquinone
Authors: Wong Sau-King , Hutchinson Douglas A. , Wan Jeffrey K. S.
Published: May 2006

Electron spin resonance emission was studied from the photochemically produced 1,4-naphthosemi-quinone radical in liquid methanol, ethanol, isopropanol, ethylene glycol, and in acetic acid in the presence of 2,6-di-tert-butylphenol. This chemically induced dynamic electron polarization is due to the optically spin polarized triplets of the parent quinone and their subsequent hydrogen abstraction reaction with retention of the polarization in the resultant semiquinone radicals. In the acetic acid–2,6-di-tert-butylphenol system, emission was observed also from the phenoxy counter radical. The magnitude of the polarization at constant microwave power was found to be temperature dependent. The comparison of the photochemical theory and the radical-pair theory is examined in the light of some of the results obtained.
The Synthesis of Analogs of the Hallucinogen 1-(2,5-Dimethoxy-4-methylphenyl)-2-aminopropane (DOM). II. Some Ring-methoxylated 1-Amino-and 2-Aminoindanes
Authors: Coutts Ronald T. , Malicky Jerry L.
Published: May 2006

The synthesis of 2-amino-4,7-dimethoxy-5-methylindane (12a), the cyclic analog of the known hallucinogen 1-(2,5-dimethoxy-4-methylphenyl)-2-aminopropane (DOM), is described. The key intermediate was trans-2-amino-4,7-dimethoxy-6-methyl-1-indanol (trans-10a) which was converted to 12a in two ways. The prolonged action of hydrochloric acid on trans-10a gave 4,7-dimethoxy-5-methyl-2-indanone (11d), the oxime of which, on catalytic reduction, was converted to 12a in low yield. A direct catalytic reduction of trans-10a in the presence of hydrochloric acid also gave 12a, together with cis-2-amino-4,7-dimethoxy-6-methyl-l-indanol (cis-10a).The synthesis and properties of other derivatives of 2-aminoindane, and some derivatives of 1-amino-indane are also described.
Revised Rate Constants for Quenching Reactions of Excited CO2+, N2O+, and N2+
Authors: Freeman C. G. , Phillips L. F.
Published: May 2006

Data for the quenching of fluorescence excited by 58.4 nm irradiation of CO2, N2O, and N2 have been recalculated in the light of improved absorption coefficients for 58.4 nm radiation. The new rate constants for quenching of CO2+ are in better agreement with results obtained from experiments with electron beam excitation; for N2+ the disagreement is greater than before.
Mass Spectra of some 5,6α-Cyclopropano-5α-cholestane Derivatives
Authors: Templeton J. F. , Wie C. W.
Published: May 2006

The mass spectra of the epimeric 3-substituted hydroxy and ethoxy derivatives of 5,6α-cyclopropano-5α-cholestane have been reported and on the basis of deuterium-labelled compounds the nature of some high molecular weight fragments are discussed. Together with the characteristic fragment ions of steroidal derivatives ions related to the presence of the 5,6α-cyclopropane ring occur at m/e 247, 301, 302, and 329.
An Ab Initio Study of the Effect of Substituents on Protonation of the Carbonyl Group
Authors: Hopkinson A. C. , Csizmadia I. G.
Published: May 2006

Ab initio calculations have been performed on a series of molecules HCOX, where X=CH3, NH2, OH, F, H, and also on the corresponding oxygen protonated cations. Rotational studies show the incoming proton to be trans to the substituent X except in formyl fluoride, where internal hydrogen bonding stabilizes the cis isomer. The geometries of the fluoro- and amino-substituted cations have been optimized along with that of oxygen protonated ketene. Proton affinities are found to be very dependent on substituents with the order of basicity being [Formula: see text]an order which closely follows the negative charge on the oxygen. Plots of the computed charge on the carbon atoms against the core binding energy are different for the cations and neutral compounds but can be made to fall on the same line by correcting the binding energy using "the charge potential model" for the K-shell electron which is removed.
Kinetics of Proton Transfer Reactions of Carbon Acids. IV. Primary Deuterium Isotope Effect in the Reaction of Di-(4-nitrophenyl)methane-d2 with t-Butoxide
Authors: Kim Jae-Hang , Leffek Kenneth T.
Published: May 2006

The primary deuterium isotope effect has been measured for the proton transfer reaction from di-(4-nitrophenyl)methane to t-butoxide ion in a solvent consisting of 10% v/v toluene in t-butanol at a series of temperatures between 20 and 45 °C. The isotopic rate ratio, kH/kD, is 7.3 at 25 °C. The activation parameters showed an enthalpy of activation difference (ΔHD≠ − ΔHH≠) of only ca. [Formula: see text] kcal mol−1 and an entropy isotope effect (ΔSD≠ − ΔSH≠) of −2.4 cal mol−1 deg−1. The latter indicates, according to the theory of Bell, that tunnelling of the proton through the energy barrier is unimportant in this reaction. This result is compared to other reactions in the literature, in which tunnelling has been postulated to occur.
A Vinylogous Wagner Rearrangement in the Benzonorbornene Series
Authors: Wiesner Karel , Ho Pak-Tsun , Ohtani Hiroyuki
Published: May 2006

A simple synthesis of compound 11 by a generally applicable novel method is described. This compound undergoes an acid-catalyzed rearrangement to the ketone 12 in high yield at room temperature.
The 19F Nuclear Magnetic Resonance Spectra of Octahedral Fluorothiocyanato-N- and Fluorocyanato-N-Titanates(IV)
Authors: Dean Philip A. W. , Ferguson Brian J.
Published: May 2006

The low temperature 19F n.m.r. spectra of the mixtures TiF62−−TiX62− (X = Cl−, Br−, NCS−, NCO−) in sulfur dioxide solution have been examined. When X = Cl− or Br− rapid fluorine exchange is occurring even at the lowest accessible temperature, but when X = NCS− or NCO− the spectra of the individual mixed species TiF6−xXx2− are observed. In the latter two cases the solutions also contain fluorine-bridged dimers in stable equilibrium. The 19F chemical shifts of TiF6−xXx2− (X = NCS− or NCO−) and of some related mixed complexes are reasonably represented by the equation δ = pC + qT where C and T are constants characteristic of the substituent X and p and q are the number of ligands X cis and trans respectively to the resonating fluorine. The constants T appear to be a measure of the π-donor ability of the ligand X in these complexes, supporting the idea that the chemical shift of a fluorine in fluorotitanates is determined largely by the extent to which fluorine-to-titanium back donation occurs.
The Synthesis of 4-O-α-D-Glucopyranosyl-L-rhamnopyranose
Authors: Berry Joffre M. , Button Guy G. S.
Published: May 2006

4-O-α-D-Glucopyranosyl-L-rhamnose has been synthesized in 40% overall yield by condensation of 2-O-benzyl-3,4,6-tri-O-p-nitrobenzoyl-β-D-glucopyranosyl bromide with methyl 2,3-O-isopropylidene-α-L-rhamnopyranoside in nitromethane using mercuric cyanide as acid acceptor. The methyl glycoside hexaacetate was obtained crystalline.
A Carbon-13 Nuclear Magnetic Resonance Study of Cation Solvation in Alcohols
Authors: Stockton Gerald W. , Martin John S.
Published: May 2006

Natural abundance 13C spectra of solvent coordinated to the cation have been observed in solutions of Mg(II) and Al(III) salts in alcohols. Carbon shielding changes induced by cations resemble those induced by electronegative substituents; a sign reversal between the β and γ positions is found in both instances. Solvent exchange rates correspond to those found by 1H n.m.r.; this confirms that whole molecule exchange is dominant. Selective relaxation of the solvation shell signals at low temperatures reflects differences in conformational mobility within the solvation complex.
Formation of the Radical Cations of Some Tetracyclic Aromatic Hydrocarbons in Boric Acid Glass
Authors: Khan Z. H. , Khanna B. N.
Published: May 2006

The radical cations of tetracene, chrysene, 1,2-benzanthracene, and 3,4-benzphenanthrene have been produced in boric acid glass by u.v. irradiation. Their electronic spectra are recorded in the region 200–1400 nm and show a close resemblance to the available data for the cations reported earlier.
13C Nuclear Magnetic Resonance Studies. 38. Examination of the Long-range Shielding Effects of the Hydroxyl Group in Alicyclic Systems
Authors: Grover S. H. , Stothers J. B.
Published: May 2006

The substituent effects of the hydroxyl group on the 13C shieldings of the trans-decalols and the 10-methyl-trans-decalols have been determined. The shifts for the carbons three and four bonds from the site of substitution depend strongly on their orientation with respect to the hydroxyl group. While the latter have not been widely recognized, these δ effects are valuable for spectral analysis and stereochemical assignments since these range up to 3.4 p.p.m. In direct contrast to the well established trends for γ effects, steric crowding of δ nuclei causes marked downfield shifts. The corresponding effects in several steroids are illustrated.
A Carbon-13 Nuclear Magnetic Resonance Study of Binding of Copper(II) to Pyrimidine Nucleotides and Nucleosides
Authors: Kotowycz George
Published: May 2006

The influence of paramagnetic Cu2+ ions on the proton decoupled 13C n.m.r. spectra of pyrimidine nucleosides and nucleotides has been studied. For 5′-CMP, the C5 resonance is broadened first on the addition of Cu2+ ions followed by the C2, C4, and C1′ resonances. From a comparison of the transverse and longitudinal relaxation rates of the base carbon nuclei due to the presence of Cu2+ ions, binding of Cu2+ to the N3 nitrogen of 5′-CMP is predicted. A similar broadening behavior is observed for 5′-UMP, 5′-TMP, cytidine, and uridine. This indicates that the Cu2+ ion is located near the N3 nitrogen in these Cu2+-nucleoside and -nucleotide complexes.
The Master Equation for the Dissociation of a Dilute Diatomic Gas. XI. Vibrational Freezing in a Nozzle Flow
Authors: Labib Nabil I. , Pritchard Huw O.
Published: May 2006

A previously reported calculation on a model expansion in a nozzle flow is extended to the point where the whole vibrational energy "freezes" and the behavior of the vibrational relaxation time is examined. Starting with the high levels, each individual vibrational energy level becomes decoupled from the ground state in sequence, down to and including υ = 1; under these conditions, all measures of the vibrational relaxation time fail, but perhaps surprisingly the rate constant for recombination remains well defined.
Quaternary Nitrogen Heterocycles. VI. Equilibria and Kinetics of Pseudobase Formation from some Heteroaromatic Dications
Authors: Bunting John W. , Meathrel William G.
Published: May 2006

Equilibrium constants (pKROH) and the kinetics of cationpseudobase equilibration have been measured for pseudobase formation by the 5,6-dihydropyrazino[1,2,3,4-lmn]-1,10-phenanthrolinium (1; pKROH = 9.54), 5H-6,7-dihydro-1,4-diazepino[1,2,3,4-lmn]-1,10-phenanthrolinium (2; pKROH = 9.17), and pyrazino[1,2,3,4-lmn]-1,10-phenanthrolinium (3; pKROH = 6.22) dications. Ultraviolet and p.m.r. spectral studies indicate that in strongly basic methanolic solutions 1 and 2 form bismethoxide adducts whereas in aqueous alkaline solutions these cations form the monopseudobase alkoxide ions (zwitterions) rather than the dipseudobases. The lower pKROH value for 2 than for 1 is suggested to arise from strain in the dication 2, which is relieved upon pseudobase formation.
The Near-ultraviolet Absorption Spectrum of Diimide Vapor
Authors: Back R. A. , Willis C. , Ramsay D. A.
Published: May 2006

Absorption spectra of N2H2 and N2D2 in the gas phase have been obtained in the region 3000–4300 Å, consisting of about 30 diffuse bands for each compound. Long progressions in the spectra are attributed to excitation of the H—N=N bending mode, v2′, in the upper state, with much shorter progressions arising from the N=N stretching mode, v3′; values of v2′ = 1215 and 910 cm−1 and v3′ = 1550 and 1440 cm−1 were estimated for N2H2 and N2D2 respectively.The spectra are attributed to the 1Bg ← 1Ag(π* ← n+) transition of trans diimide, probably made allowed by vibronic interaction. From Franck–Condon calculations the H—N=N angle in the upper state was estimated to be 132 ± 2°, an increase of 25° from the ground-state value; the increase in the N=N bond length was estimated to be about 0.05 Å.
Chemistry of Aminochromes. Part XVIII. The Effects of pH and Substituents on some Aminochrome–Thiol Reactions
Authors: Powell W. S. , Heacock R. A.
Published: May 2006

Aminochromes react with thiols in the pH range ca. 3–4 to give mainly 4-thiosubstituted-5,6-dihydroxyindoles (or the corresponding 5,6-dihydroxyindolines) along with reduction products (5,6-dihydroxyindoles or 5,6-dihydroxyindolines). There is also some evidence, in this pH range, for the formation of an addition product involving one of the aminochrome carbonyl groups directly. Under somewhat less acidic conditions (pH 5–6), however, the major products formed initially are, in general, 3a-thiosubstituted-3a, 4-dihydroaminochromes. These products, which are formed reversibly, are gradually replaced in the reaction mixture by the indolic products, which are formed irreversibly. The increased rate of formation of the 4-thiosubstituted-5,6-dihydroxyindoles at lower pH's is probably due to the increased protonation of the C-6 carbonyl oxygen. The 3a-thiosubstituted-3a, 4-dihydroaminochromes may be formed more readily at higher pH's due to the increased ionization of the thiol.
Spectra and Decay of Trichloromethyl Radicals in Aqueous Solution
Authors: Lesigne B. , Gilles L. , Woods R. J.
Published: May 2006

Trichloromethyl radicals (λmax < 230 nm, ε230 nm = 2300 ± 450 M−1 cm−1) are formed by the pulse radiolysis of aqueous carbon tetrachloride solutions. At concentrations of the order of 10−4M and pH 5.5–12.4, CCl3 disappears by a second-order process with 2k = (7.4 ± 1.8) × 108 M−1 s−1 and without detectable hydrolysis. Both CCl3 and CHCl2 are believed to be formed by the pulse radiolysis of aqueous chloroform solutions but at wavelengths greater than 230 nm only absorption attributable to CCl3 was observed.
On the Whiteway–Smith–Masson and Flory–Stockmayer Theories of Polymerization
Authors: Stepto R. F. T.
Published: May 2006

An error in the Whiteway–Smith–Masson (W.S.M.) theory of random polymerization is noted. The application of the W.S.M. theory and the Flory–Stockmayer (F.S.) theory to experimental data is discussed, and no grounds for the rejection of the F.S. theory are found. A method of simulating the self-polymerization of RAƒ monomers is proposed which should be capable of resolving differences between the two theories.
The γ-Radiolysis of Liquid Cyclohexane Containing Di-n-Propyl Disulfide
Authors: Stone John A. , Esser Joseph
Published: May 2006

Di-n-propyl disulfide is an electron, positive ion, and free radical scavenger in γ -irradiated liquid cyclohexane. The efficiency of electron scavenging is comparable with that of sulfurhexafluoride and the efficiency of H atom scavenging is comparable with that of ethylene. The expected product of cyclohexyl radical scavenging, namely cyclohexylpropyl sulfide, accounts for only about one quarter of these radicals which disappear. No other sulfur-containing products are found. In cyclohexane solutions containing two different disulfides or a disulfide and a thiol a rapid equilibration of the thiyl groups leads to their statistical distribution between the sulfur-containing species.
Elimination, Oxidation, and Transposition Reactions in Conformationally Biased Carbohydrates: Methyl 4,6-O-Benzylidene-α-D-Altropyranosides Containing the Phenylthio Group
Authors: Hanessian Stephen , Staub A. P. A.
Published: May 2006

The title compound containing a phenylthio group at C-3 and a methanesulfonate group at C-2 undergoes a quantitative transposition reaction in refluxing benzene to give the diequatorial isomer. In DMSO, a complex reaction takes place leading to elimination and oxidation at C-2. Oxidation of the title compound containing a phenylthio group at C-2, with acetic anhydride–DMSO gives the corresponding 3-uloside. With the isomeric 3-phenylthio derivative the enol acetate is formed. These results are rationalized based on mechanistic considerations.
The Synthesis of 1,7- and 1,8-Dimethylphenazines
Authors: Taurins Alfred , Long Andrew Davenport
Published: May 2006

The cyclization of 2′,4- and 2′,5-dimethyl-2-nitrodiphenylamine with sulfur in boiling diphenyl ether gave 1,7- (1) and 1,8-dimethylphenazine (2), respectively. A mixture of 1 and 2, obtained by the condensation of 3,4-diaminotoluene with 3-methylcatechol, was separated into components by chromatography. The u.v. and i.r. spectra of 1 and 2 were recorded.