bluuebunny/crossref_metadata_2025 huggingface dataset:
The Challenge of Change: Australian Cities and Urban Planning in the New Millennium
Authors: FORSTER CLIVE
Published: May 2006

This paper reviews recent research on the changing spatial structure of Australia's major cities from the early 1990s, concentrating on (a) the location of employment and journey to work patterns, (b) the changing nature of housing, and (c) patterns of residential differentiation and disadvantage. The paper argues that the 1990s was a watershed decade during which some taken‐for‐granted aspects of Australian urban character experienced significant change. It then examines the latest generation of strategic planning documents for these major metropolitan areas, all published between 2002 and 2005, and argues that there is a mismatch between the strategies’ consensus view of desirable future urban structure, based on containment, consolidation and centres, and the complex realities of the evolving urban structures. In particular, the current metropolitan strategies do not come to terms with the dispersed, suburbanised nature of much economic activity and employment and the environmental and social issues that flow from that, and they are unconvincing in their approaches to the emerging issues of housing affordability and new, finer‐grained patterns of suburban inequality and disadvantage. Overall, the paper contends that current metropolitan planning strategies suggest an inflexible, over‐neat vision for the future that is at odds with the picture of increasing geographical complexity that emerges from recent research on the changing internal structure of our major cities.
Photoamidation of 2,3,4,6-tetra-O-acetyl-1-deoxy-D-arabino-hex-1-enopyranose and of (Z)-3-deoxy-3-C-(methoxycarbonyl)methylene-1,2:5,6-di-O-isopropylidene-α-D-ribo-hexofuranose
Authors: Rosenthal Alex , Ratcliffe M.
Published: May 2006

The acetone-initiated photochemical addition of formamide to 2,3,4,6-tetra-O-acetyl-1-deoxy-D-arabino-hex-1-enopyranose (1) afforded 3,4,5,7-tetra-O-acetyl-2,6-anhydro-D-glycero-D-ido-heptonamide (2), 3,4,5,7-tetra-O-acetyl-2,6-anhydro-D-glycero-D-talo-heptonamide (3), and 4,5,6,8-tetra-O-acetyl-3,7-anhydro-1-deoxy-2-methyl-D-glycero-D-talo-octitol (4), in 55, 7, and 23% yields, respectively. Reduction of 2 with diborane followed by acetylation yielded 1-acetamido-3,4,5,7-tetra-O-acetyl-2,6-anhydro-1-deoxy-D-glycero-D-ido-heptitol (7) in 70% yield. Deacetylation of 2 and 3 with sodium methoxide yielded the unsubstituted heptonamides 5 and 6.Photoamidation of (Z)-3-deoxy-3-C-(methoxycarbonyl)methylene-1,2:5,6,-di-O-isopropylidene-α-D-ribo-hexofuranose (8) yielded 3-C-[R and S-carbamoyl(methoxycarbonyl)methyl]-3-deoxy-1,2:5,6-di-O-isopropylidene- α-D-allofuranose (9) and (10).
Ormosia alkaloids. VII. Total synthesis of ormosanine, piptanthine, 18-epiormosanine, and d,l-panamine
Authors: Liu Hsing-Jang , Sato Yasuhiko , Valenta Zdenek , Wilson Jerome Sutherland , Yu Terry Ta-Jen
Published: May 2006

A stereoselective synthesis of ormosanine (1), identical in all respects with the naturally occurring racemic alkaloid of O. jamaicensis, has been accomplished. Subsequent transformation of synthetic ormosanine into racemic piptanthine (2) and into d,l-panamine (3) is described. 18-Epiormosanine (22) has also been prepared by total synthesis. Some unusual stereochemical effects allowing the control of configuration at C6, C11, and C18 are discussed.
Intermolecular interactions in nuclear magnetic resonance. X. A site-specific continuum model for the gas-to-liquid shifts of nonpolar solutes. Applications to proton medium shifts and the determination of cavity radii
Authors: Rummens Frans H. A.
Published: May 2006

Based on the Onsager reaction field theory of the dielectric polarization of a continuum, a model has been developed to calculate the Van der Waals contribution σw to the gas-to-liquid medium shifts of nonpolar solutes. The addition of a site factor correction, to account for the off-center location of the measured nucleus in the solute molecule, provides a marked improvement. The agreement between experimental and calculated σw's is good (±0.05 ppm), but a separate scale factor is required for each solute. This nonuniversality is shown to be related to the Onsager approximation for the solute cavity radius; a3 = 3V1/4πNA. It is shown that Van der Waals shifts can be used for the determination of the Onsager cavity radii; for a number of molecules these cavity radii are given. It is claimed that this method is as precise, but much easier to apply, than the Böttcher–Onsager optical method.No evidence could be found for the existence of a [Formula: see text] contribution to the medium shifts due to permanent electric dipoles of solvent molecules. Combination of experimental medium shifts in anisotropic solvents with calculated σw contributions allows the evaluation of the neighbor anisotropy contribution σa. The σa effect is found to be solute dependent; there is a V1−1/6 proportionality related to the molar volume V1 of the solute and in addition there are site effects with site factors both greater and less than unity, depending on molecular shape. The solvent dependence of σa includes not only the magnetic susceptibility anisotropy Δχ2 and the molar volume (V2−1/3) but also a term corresponding to the geometric anisotropy of the solvent molecule.The solvent CS2 is found to behave as an isotropic molecule.
Approaches to the synthesis of quinazolino[1,2,3]benzotriazinones
Authors: Ahern T. Patrick , Fong Handrick , Vaughan Keith
Published: May 2006

The synthesis of 1-(o-carboxamidophenyl)-3-aryl triazenes 12 and 15 (X = CONH2 and H) is described. Reaction of 3-(o-carboxamidophenyl)-1-(o-methoxycarbonylphenyl)-triazene (12) with piperidine in ethanol affords 2-[2-(piperidin-1-ylazo)phenyl]quinazolin-4(3H)-one (18); the formation of 18 in this reaction can only arise via the unstable quinazolino[1,2-c][1,2,3]-benzotriazinone 8 by triazine ring cleavage under the influence of piperidine. Attempted synthesis of the 4-iminotriazine 17, an isomer of the quinazolone 18, from the o-cyanophenyltriazene 20, resulted only in the formation of quinazolino[3,2-c][1,2,3]benzotriazin-8-one (6), an isomer of 8. The o-cyanophenyltriazene 20 undergoes spontaneous cyclisation, rearrangement, and further cyclisation.
Nitration of p-cymene. Exchange and rearomatization reactions of p-cymene adducts
Authors: Fischer Alfred , Röderer Rolf
Published: May 2006

Nitration of p-cymene in acetic anhydride gives a mixture of cis- and trans-1-isopropyl-4-methyl-4-nitro-1,4-dihydrophenyl acetate as the main product as well as 2- and 3-nitro-p-cymene and p-nitrotoluene. Acid-catalysed methanolysis of the acetoxynitro adduct gives a mixture of the cis- and trans-methoxynitro adducts. Under basic conditions the acetate adduct is converted into the corresponding alcohol which is in turn rearomatized to 2-isopropyl-4-methylphenol. The adducts rearomatize to 2-nitro-p-cymene in strong acid.
The flash thermolysis of allyl sulphides
Authors: Giles H. Gwynne , Marty Robert A. , Mayo Paul De
Published: May 2006

The flash thermolysis of allyl sulphides has been shown to generate thiocarbonyl compounds. The reaction provides a route to very reactive substances such as thioacrolein, thiobenzaldehyde. and monothiobiacetyl; these have been characterized spectroscopically.
Dipolar and calorimetric study of the complexes between N,N-dimethyl-N′-phenylformamidines and phenols
Authors: Foubert Alfred F. , Huyskens Pierre L.
Published: May 2006

The dipole moments µb of N,N-dimethyl-N′-phenylformamidine and its 4-methylphenyl and 4-chorophenyl derivatives and the dipole moments µab of some 20 complexes of these bases with phenols were determined in cyclohexane at 298 K. Assuming the additivity of the bond moments, the angles αb between µb and the axis C1C4 phenyl group were computed for the three bases. Dipole increments [Formula: see text] were then computed assuming the hydrogen bond involved the electron pair of the sp2 hybridized imino nitrogen atom. The variation of the Δµ computed in this way with the complexation enthalpy ΔHab is described by the same curve as that for the systems phenols–anilines and phenols–pyridines. This is not the case when other structures are chosen for computing Δµ and this provides evidence for the 'imino' structure of the complexes. For a given amidine, the dipole increment increases when the proton donor becomes more acidic. The derivative d Δµ/dpKa here is of the order of −0.5 D per pKa unit whereas this value is only −0.2 for the pyridines. The absolute values of Δµ are also greater for the amidines. This can be ascribed in part to a higher proportion of H-bonds of the ion pair type [Formula: see text] when the amidine is complexed by the same phenol as the pyridines.
A study of 13C–15N couplings and revised 13C shieldings in 15N-enriched E-acetophenone oximes
Authors: Buchanan Gerald W. , Dawson Brian A.
Published: May 2006

13C nmr chemical shifts and 13C–15N couplings through one, two, and three bonds are reported for E-acetophenone oxime and five para-substituted derivatives. It is shown that earlier assignments for three of these compounds, based on lanthanide induced shifts and CNDO calculations, are erroneous. With the exception of the methoxyl group, couplings are relatively insensitive to the nature of the para-function. For geminal 13C–15N interactions, the proximity of the nitrogen lone pair to the carbon terminus greatly enhances the absolute value of the coupling constant.
Partial molar volumes of aqueous 1:1 and 2:1 electrolytes and a structure model
Authors: Bahe Lowell W. , Jung Kathryn A.
Published: May 2006

An expression for partial molar volumes is derived from the free energy equation based on field-dielectric-gradient forces, as well as coulombic forces, between ions in structured solution. Qualitative agreement between the model and experimental partial molar volume data is very good. Excellent quantitative agreement is obtained by adopting for a universal parameter of the theory a value that implies [Formula: see text] for water at 25 °C and 1 atm. The latter value is compatible with data obtained from direct measurements.
Etude de Mn(II) en solution aqueuse perchlorique par résonance paramagnétique électronique
Authors: Benali-Baitich Ouassini , Wendling Edgar
Published: May 2006

The behaviour of manganese(II) perchlorate in aqueous perchloric acid solution [Formula: see text] was studied by epr at 25 and 55 °C. The broadening of the band following addition of HClO4 considerably exceeds that normally caused by the increase in the viscosity. This result is interpreted in terms of the formation of an internal monoperchlorato complex in equilibrium with the external complex. The decrease in the relative intensity of the signal following addition of HClO4 confirms the presence of an internal monoperchlorato complex and permits the evaluation of its stability constant, (8.0 ± 1.5) × 10−2. The relative stability of the Mn(II) monoperchlorato complex compared to those of Co(II) and Ni(II) is explained by a consideration of the ligand field stabilization energy. [Journal translation]
The use of polymer supports in organic synthesis. V. The preparation of monoacetates of symmetrical diols
Authors: Fyles Thomas M. , Leznoff Clifford C.
Published: May 2006

A 2% cross-linked divinylbenzene–styrene copolymer was directly lithiated with n-butyllithium in the presence of N,N,N′,N′-tetramethylethylenediamine. The lithiated polymer on reaction with a benzophenone gave an insoluble polymer-bound trityl alcohol. Further reaction with acetyl chloride gave a polymer-bound trityl chloride which, on treatment with the primary symmetrical diols 1,10-decanediol, 1,7-heptanediol, and 1,4-butanediol, gave mostly symmetrical diols monoblocked by insoluble polymer-bound trityl groups. Acetylation followed by acid cleavage from the polymer gave the monoacetates of 1,10-decanediol, 1,7-heptanediol, and 1,4-butanediol and some recovered diols. The recovered polymer can be efficiently recycled. The quantity of recovered diol was related to the problem of 'double-binding' of the symmetrical diols to the polymer-bound trityl groups. The extent of 'double-binding' could be greatly reduced by the use of polymer-bound trityl chloride prepared via the lithiated polymer and methyl benzoate or phosgene.
Molecular orbitals from group orbitals. II Conformational analysis of Systems with three heavy atoms. The XCH2CH2 system and the anomeric effect
Authors: Whangbo Myung-Hwan , Wolfe Saul
Published: May 2006

A procedure for the conformational analysis of Systems of the type AHmBHnDHk is proposed, in terms of interactions between AHmBHn— and —DHk fragments. The nodal properties and relative level orderings of the group orbitals of these fragments are obtained from the molecular orbitals of the molecules AHmBHn+1 and DHk+1. Attention is focussed upon two-orbital two-electron stabilizing and two-orbital four-electron destabilizing interactions between these fragments. A consistent interpretation of the conformational behaviour of n-propyl and 2-fluoroethyl carbonium ions and carbanions is attempted within the framework of this group molecular orbital procedure. The conformational behaviour of FCH2OH, a model for the anomeric effect, has also been examined. It is shown that the group molecular orbital approach accommodates two earlier interpretations of the anomeric effect, one of which focusses upon bond–bond interactions; the second focusses upon effects of the oxygen lone pairs. Some limitations of the model are noted, in particular the problem associated with explicit calculation of the magnitudes of different stabilizing and destabilizing interactions.
New reactions of 2-substituted indoles
Authors: Dave Vinod , Warnhoff E. W.
Published: May 2006

2-Alkyl (or aryl) indoles react readily with phenylhydrazine in hydrochloric–acetic acid to give o-aminophenylpyrazoles 7, if the 2-substituent is of small or moderate size, or else 3-aminoindoles, if the 2-substituent is sufficiently bulky. The 3-aminoindoles readily undergo oxidative dimerization to indolylidene aminoindoles [Formula: see text] Evidence is provided for the mechanisms of formation of these two kinds of products.
Syntheses, structural and conformational assignments, and conversions of pyridine and triazolopyridine nucleosides
Authors: Lynch Brian Maurice , Sharma Suresh Chandra
Published: May 2006

Regioselective and stereoselective routes to 2- and/or 4-substituted vic-triazolo(4,5-b)pyrid-5-ones have been established, and series of 4- and 2-β-D-ribofuranosyl derivatives have been prepared as candidate substrates for, and potential inhibitors of, the enzymes of polynucleotide synthesis. Structural assignments were made by comparison of spectroscopic properties (pmr, uv) with those of appropriate model compounds, and on the bases of proton chemical shift and coupling constant patterns in the ribose moieties, it is proposed that 4-β-D-ribofuranosyl-vic-triazolo(4,5-b)pyrid-5-ones adopt conformations with 'high anti' sugar–base torsional angles. A facile ribofuranose → ribopyranose conversion is observed with a 2-β-D-ribofuranosyl-vic-triazolo(4,5-b)pyrid-5-one.
Recherches en série hétérocyclique. XXVI. Etude de la condensation de l'azidoacétate d'éthyle sur le thiophènedicarbaldéhyde-2,3: nouvelle voie d'accès à des thiéno[2,3-c] et -[3,2-c] pyridines et pyridones
Authors: Farnier Michel , Soth Samreth , Fournari Pierre
Published: May 2006

Ethyl azidoacetate was reacted with thiophene-2,3-dialdehyde, in which the two formyl groups are free or in which one of them is blocked as the diethyl acetal, to yield, after cyclization, thieno[2,3-c] and -[3,2-c] pyridines and pyridones, respectively. The structures of the intermediate products were established by nmr; a reaction scheme is proposed. [Journal translation]
Substituent effects on polarographic reduction of some photographic color intermediates
Authors: Shawali Ahmad S. , El-Anadouli Bahgat E.
Published: May 2006

Polarographic reduction of two series of benzoylacetanilides has been investigated in 40% (by volume) ethanolic Britton–Robinson buffers. One series (A) contains substituents on the anilide moiety, and the second (B) has substituents on both the anilide and benzoyl moieties. Polarographic controlled-potential electrolysis data indicate that the electroactive species in both series is the protonated form (ArCOCH2CONHAr′)H+. The reduction half-wave potentials of anilides of series A were found to be independent of the nature of the substituent, whereas those of series B show a good linear relationship when plotted vs. the σ substituent constant of the substituent on the benzoyl moiety (ρ = 0.284, r = 0.995). Values of the acid dissociation constants of the keto (K1) and enol (K2) tautomers of the anilides of series A were calculated; unlike their E1/2 values, the pK1 data show a linear correlation with the Hammett substituent constant, σ. The pK2 values show, however, little variation with σ.
A simple synthesis of oxazolidine and thiazolidine derivatives of hydroxymethylglyceraldehyde acetonide
Authors: Just George , Chung Bong Young , Rosebery Gerald , Dupré Michel
Published: May 2006

Starting from mannitol diacetonide, a simple, high yield preparation of the title compounds is described.
Crystal structure of β-D-acetyl cellobiose, C28H38O19
Authors: Leung F. , Chanzy H. D. , Perez S. , Marchessault R. H.
Published: May 2006

The crystal structure of β-D-acetyl cellobiose was studied by X-ray crystallography. The crystal data are a = 31.814(4), b = 19.414(5), c = 5.614(1) Å, space group P212121, Z = 4. The structure, solved by direct method, was refined by block-diagonal least-squares to a final R value of 0.075 for 2605 observed reflections. The molecular conformation involves 4C1 pyranose rings with glycosidic torsion angles corresponding to near maximum extension of the molecule. Substantial differences in conformational angles were observed between this molecule and the unacetylated counterpart. The molecules lie along the a-axis of the unit cell.
Etude de l'équilibre tautomère des pyrazolinones-4
Authors: Sabaté-Alduy C. , Bastide J.
Published: May 2006

The keto–enol equilibria in variously substituted 4-pyrazolinones were studied in several solvents; these compounds exist in the enol form only. An MO theoretical study of these compounds in comparison to the 5-pyrazolinones is reported.
Structure of radicals produced by γ-radiolysis. Part 4. Adamantane matrices doped with various 5-membered heterocyclic molecules
Authors: Winters D. L. , Ling A. Campbell
Published: May 2006

The effects of γ-adiolysis at room temperature on adamantane and adamantane-d16 matrices doped with 5-membered heterocyclic molecules has been examined by X-band electron spin resonance (esr) spectrometry. Radical structures formed from heterocyclic solute molecules are discussed and tentative assignments made for 2-methyl-, 3-methyl-, and 2,5-dimethylthiophene, 2-methyl-, and 2,5-dimethylfuran. Discussion of possible radical structures derived from furan, tetrahydrofuran, 2-methyl- and 3-methyltetrahydrofuran, 2,5-dihydrofuran, and 4,5-dihydro-2-methylfuran, is included, but unambiguous assignments of structure cannot be made for these compounds from the esr data obtained. Other molecules examined included thiophene, pyrrole, and 1-methyl- and 1,2,5-trimethylpyrrole. For these latter molecules, experimentally obtained first derivative X-band esr spectra were too poorly resolved to allow rational discussion of possible structures. It was noted that perdeuterated adamantane matrices provided superior resolution for esr spectra derived from radicals with a delocalized spin center such as allyl or allenyl species.
Thermodynamic properties of binary liquid mixtures
Authors: Rao Murari Venkata Prabhakara , Naidu Puligundla Ramachandra
Published: May 2006

Excess volumes of the three binary mixtures: (1) cyclohexane – diethyl ketone, (2) cyclohexane–benzonitrile, and (3) toluene–benzonitrile have been measured at 303.15 K using a dilatometer. Excess volumes of the first two systems are positive over the whole range of composition and are negative for the third system. The measured excess volumes and the excess heats of mixing reported in the literature for the three binary systems have been analysed in the light of the statistical theory of liquid mixtures developed by Flory. The analysis has shown that the theory in its modified form is approximately applicable to the mixtures cyclohexane–diethylketone and cyclohexane–benzonitrile.
Dehydration of 1,1′-ethylenedicyclopentanol
Authors: Diaper Dennis G. M.
Published: May 2006

The major product from the dehydration of 1,1′-ethylenedicyclopentanol is the tetrahydrofuran, 6-oxadispiro[4.1.4.2]tridecane, parent of a previously unknown ring system. The olefinic products are the conjugated diene, dicyclopentylideneethane, and the endocyclic diene, 1,2-di(1-cyclopentenyl)ethane in a ratio of about 1:2.
The application of iterative optimization techniques to chemical kinetic data of large random error
Authors: Schmid George H. , Csizmadia Valeria M. , Mezey Paul G. , Csizmadia Imre G.
Published: May 2006

The possibilities of improving the computational processing of chemical rate measurements, in the frame of linear and non-linear least-square fit methods, are investigated. A simple scaling technique to avoid the distortion of the fitted parameters, inherent in the logarithmic transformation of the rate equation, is tested on several examples, and an iterative discarding method for the selection of accurate data points is recommended.
Electrochimie de composés organométalliques. I. Electrosynthèse de cyclopentadiène cyclopentadiényl cobalt substitués
Authors: Murr Nabil El , Laviron Etienne
Published: May 2006

Cobaltocene anions have been prepared electrochemically in dimethylformamide. Their reaction with various electrophiles gives, in quantitative yields, substituted cyclopentadiene cobalt cyclopentadienyls, some of which cannot be prepared by usual methods.Substituted cyclopentadiene cobalt cyclopentadienyls are also obtained in excellent yield, by reaction of electrochemically generated cobaltocene with organic halides.
Thermodynamics of basic ionization of some aminoethers in water
Authors: Lobo Sheila Teresa , Robertson Ross Elmore
Published: May 2006

Basic ionization constants (Kb) of 2-methoxyethylamine, 3-methoxypropylamine, and bis-2-methoxyethylamine in water have been measured as a function of temperature between 5 and 45 °C, thus enabling values of ΔGb0, ΔHb0, ΔSb0, and ΔCpb0 to be calculated. The results conform with the ability of the ether function to destroy hydrophobicity in water.
Cinetique chimique en milieu micellaire. Relation entre vitesse de réaction et structure du milieu
Authors: Roux Geneviève , Viallard André
Published: May 2006

A reaction has been studied between two reactants where one, ionic, is dissolved in the aqueous phase and the other, nonionic, is distributed between the aqueous phase and a micellar phase. The kinetic study of this reaction has helped to elucidate the mechanism of the reaction.Depending on the experimental conditions, it is possible to have either an equilibrium of the nonionic solute between the aqueous and micellar phases, or a reaction rate limited by the rate of diffusion of this reactant from the micellar phase to the aqueous phase. It will be shown that such kinetic studies can be used to determine quantitatively the distribution of the solute between the various phases and even inside the micelles. [Journal translation]
Isotopic exchange reactions of amines. Part 1. An 2H nuclear magnetic resonance study of the amino to methyl group deuteron exchange in methylamine
Authors: Halliday James D. , Bindner Patrick E.
Published: May 2006

Deuteron exchange kinetics between the methyl and amino groups in methylamine, catalyzed by potassium methylamide (PMA), have been studied by 2H nmr.[Formula: see text]Typical values of kobs, the observed pseudo first-order exchange rate, are 1.0 × 10−5 s−1 at 0.21 M PMA and 323 K. Effects of added potassium methylamide and temperature are described. The rate is unaffected by the thermal decomposition product of PMA and there is little or no catalysis by an equilibrium mixture of the solvated electron species e−, (e−K+), and K−. The active catalyst in solution is shown to be monomeric PMA in equilibrium with relatively inactive dimers, …, n-mers. A mechanism that describes the exchange and relates it to the thermal decomposition of the amide is discussed.
Highly stereoselective H–D exchange of diastereotopic protons in 4′,1″-dimethyl-1,2,3,4-dibenzylcyclohepta-1,3-diene-6-one
Authors: Fraser Robert R. , Champagne Philippe J.
Published: May 2006

The rates of base-catalyzed H–D exchange of the diastereotopic methylene protons adjacent to the carbonyl group in the title compound have been measured in methanol-O-d. Sodium methoxide as catalyst produced a rate ratio of 73:1. Reasons for the large increase in stereoselectivity over that encountered in the exchange of 4-tert-butylcyclohexanone are proposed.
Formation and photolysis of alkyl and peroxy radicals in dilute glass matrices
Authors: Adam Frank Cuthbert , Marshall Iain R. H.
Published: May 2006

The use of molecular oxygen as a spin trap in rigid glassy hydrocarbon media at 77 K is investigated. By slight warming of the matrix, oxygen is found to effectively scavenge the isolated alkyl radicals produced by γ-irradiation to give RO2•, but does not react with radical pairs lying in the ionization tracks. The yield of scavengable radicals in 3MP is determined and compared to the findings of other workers. The butyl radical yields for γ-irradiated 1.0 mol l−1 butyl chlorides in 3MP are found to be: t-BuCl, 5.8; i-BuCl, 5.1; 2-BuCl, 4.9; and 1-BuCl, 2.2. Alkyl radicals cannot be recovered from either RO2 or BuO2 by uv photolysis due to solvent abstraction reactions, or because of photon induced reactions of the alkyl radicals. Photolysis of the butyl radicals themselves at 253.7 nm give rise to decomposition and solvent abstraction reactions.
The reaction of diphenylethylenes with boron trifluoride and water
Authors: Bywater Stanley , Worsfold Denis J.
Published: May 2006

The concentrations have been measured of carbenium ions formed when diphenylethylene and diphenylpropene react with boron trifluoride and water in methylene chloride solution. With both these olefins it appeared necessary that two boron trifluoride molecules should be present for every water molecule to form the carbenium ion. Also the ionic species formed showed a very high degree of ionic dissociation. Diphenylethylene rapidly formed the cyclized dimer, and as a side reaction formed some triphenylmethylcarbenium ions. The diphenylpropene gave a diphenylcarbenium ion that appeared stable, but the accompanying anion was thought to be unstable and rearranged to a more stable form which disrupted the dependences on the concentrations of original reactants.
Nuclear magnetic resonance spectra of o-hydroxythiobenzamides: the intramolecular hydrogen bond as a conformational probe
Authors: Fulea Adrian O. , Krueger Peter J.
Published: May 2006

The OH and NCH2 proton signals of 1-(2′-hydroxythiobenzoyl)-2-methylpiperidine (2) are resolved into separate peaks assigned to four conformers (EA, EB, ZA, and ZB) in 220 MHz nmr spectra at −50 °C. All have a strong intramolecular [Formula: see text] hydrogen bond. The ZB and EB conformers have the lowest and highest ground state energies, respectively. Exchanges between A and B conformers have a higher energy barrier than exchanges between Z and E isomers, but by +40 °C all four conformers interchange rapidly. The nature of all possible interchange processes is considered and a potential energy surface with respect to rotation about the Ph—C(S) and C—N bonds is presented. For the 4-methyl analogue of 2 low temperature nmr spectra exhibit two sharp OH signals arising from A and B conformers. For 2,6-di-methyl-4-(2′-hydroxythiobenzoyl)morpholine the A/B OH doublet of the cis dimethyl isomer can be distinguished from that of the trans isomer. Thus it is demonstrated that the intra-molecularly hydrogen bonded OH proton is a good spectroscopic conformational probe. Nuclear magnetic resonance, ir, and uv data all indicate that in the 2,6-dimethylpiperidine analogue of 2 the CNC and Ph—C(S)N planes are perpendicular due to steric interference. Coplanarity of the phenyl ring with the thioamide group is attributed to a very strong intramolecular [Formula: see text] hydrogen bond, in equilibrium with a proton transferred [Formula: see text] form in solution. This structure resembles the transition state for rotation in the most readily achieved exchange between conformers of 2.
1,4-Cycloheptadienes: preparation and comparison of their proton magnetic resonance spectra with those of the corresponding cycloheptatrienes
Authors: Pikulik Ivan , Childs Ronald F.
Published: May 2006

A general route to 3-substituted cyclohepta-1,4-dienes is described in this paper. 7-Substituted cycloheptatrienes were used as starting materials and these were reacted with 4-phenyl-1,2,4-triazoline-3,5-dione to give 4 + 2 cycloaddition products of the norcaradiene form of the cycloheptatrienes. Catalytic reduction of these adducts gave 9-substituted 4-phenyl-2,4,6-triazatetracyclo[5.3.2.02,6.08,10]dodeca-3,5-diones in good yield. Basic hydrolysis of the hetero-cyclic ring of these products followed by Cu2+ oxidation of the resulting hydrazo compounds gave the copper complexes of substituted 6,7-diazatricyclo[3.2.2.02,4]non-6-enes. The azo compounds, formed on decomplexation of the copper complexes, readily lost nitrogen to give 3-substituted cyclohepta-l,4-dienes. Care had to be taken during these last steps as the cyclo-heptadienes with carboxylate substituents very readily isomerized to the conjugated isomers. The pmr spectra of the cyclohepta-l,4-dienes and related cycloheptatrienes are compared and discussed in terms of the presence of an induced diamagnetic ring current in the latter systems.
Photoelectron spectra of substituted oxiranes and thiiranes. Substituent effects on ionization potentials involving σ orbitals
Authors: McAlduff E. J. , Houk K. N.
Published: May 2006

The state assignments corresponding to the second and third ionization potentials of oxirane have been the subject of some uncertainty due to the great sensitivity of Koopmans' theorem predictions to the type of calculation performed for this molecule. In this study, the assignments made by Basch et al. for oxirane are confirmed through measurement of the photoelectron spectra of methyl-, 1,1-dimethyl-, 1,2-dimethyl, ethyl-, vinyl-, phenyl-, chloromethyl-, and fluoromethyloxirane. The second and third ionizations of thiirane are confirmed to be of the opposite order from those in oxirane by correlations of these values with those reported here for methyl-, vinyl, and methoxymethylthiirane.In these compounds, mono-substitution by alkyl groups causes a decrease in ionization potential not obviously related in a simple way to the type of orbital involved. Thus, assignments cannot be made straightforwardly by observing ionization potential changes caused by hyper-conjugating or inductive substituents. Alkyl group substitution in both oxirane and thiirane lowers IP's in the same order: a2 > b2 > a1 > b1. The effects of alkyl and heteroalkyl groups on the four lowest IP's of oxirane are linearly related to the electronegativities of the groups, and to the influence of alkyl and heteroalkyl substituents on the π IP of ethylene.Comparisons of the IP's of ethylheteranes and dimethylheteranes are quite useful in determining the site of localization of orbital density in the various orbitals.Conjugating substituents, which for symmetry reasons, selectively interact with only a few orbitals make definite assignments possible. Comparisons of experimental ionization potential changes and those predicted by Koopmans' theorem using ab initio STO-3G calculations are in good agreement.
N,N′-Bis(phenylaminomethyl)parabanic add as a complexing agent. Complexes of some bivalent first row transition metals
Authors: Fabretti Antonio Costantino , Franchini Gian Carlo , Preti Carlo , Tosi Giuseppe
Published: May 2006

The preparation of some complexes of N,N′-bis(phenylaminomethyl)parabanic acid with halides of cobalt(II), nickel(II), and copper(II) is reported. The complexes of the type MLX2 seem to have pseudo-tetrahedral and pseudo-octahedral symmetry. The complexes have been studied by means of magnetic susceptibility measurements, infrared and far infrared spectra, electronic and nmr spectra, and conductivity measurements. The ligand behaves as bidentate N-bonded. The various ligand field parameters, Dq, B', and β have been evaluated. The B' values suggest a strong covalency in the metal–ligand σ bond and Dq values show a medium strong ligand field. The presence of metal–nitrogen bonds is suggested. The possible stereochemistries of the complexes are discussed in the light of the experimental results.
Intermediate stages of the sulfohaloform reaction. Preparation of α-halosulfoxides and sulfinyl chlorides. Oxygen-transfer reactions
Authors: Grossert J. Stuart , Hardstaff William R. , Langler Richard F.
Published: May 2006

Details are provided of synthetic routes from dialkyl sulfides to both α-halosulfoxides and sulfinyl chlorides. In the case of the former, oxidation of α-halosulfides to the sulfoxide stage is achieved by chlorine in acetic acid containing controlled amounts of water. Sulfinyl chlorides are prepared by chlorination of α-polyhalosulfoxides in methylene chloride. During investigations into the details of the sulfohaloform reaction, a number of novel redox reactions involving oxygen transfer between sulfur species have been observed and these are presented. They include a reduction of a sulfoxide with thionyl chloride.
The photolysis of hexaaquoiron(III) perchlorate in the presence of ethylene glycol
Authors: Carey John H. , Cosgrove Ernest G. , Oliver Barry G.
Published: May 2006

Two types of reactions occur when hexaaquoiron(III) ion is irradiated at 254 nm in the presence of alcohols. Firstly, a charge transfer transition from a water centred orbital to an iron centred orbital produces OH•radicals which go on to abstract hydrogen from the alcohols. Secondly, |the reaction with the charge transfer excited states of iron(III) species can lead to outer sphere oxidation of the alcohols. In this paper, these reactions have been studied in detail for the diol ethylene glycol in aqueous solutions. It has been found that the quantum yield of acetaldehyde, the major product of hydroxyl radical reactions with ethylene glycol, is 0.09 and the yield of formaldehyde, the major product of the direct charge transfer reaction, is 0.05 in 1 M ethylene glycol. The quantum yields for these major products, as well as minor products, such as glycolaldehyde and succinaldehyde, have been determined at several concentrations of ethylene glycol and iron. A detailed reaction scheme for the photolysis has been developed.
Voltammetric studies of metal chlorides in AlCl3–CsCl and ZnCl2–CsCl melts using an oscillating solid microelectrode
Authors: Ray H. S. , Tumanova N. Kh. , Flengas S. N.
Published: May 2006

The oscillating planar solid microelectrode developed previously (1) has been used to investigate the reduction of the ions Co2+, Ni2+, Pb2+, Cd2+, Cu+, Ag+, as well as of the redox system Fe2+/Fe3+ in solvent melts containing various amounts of CsCl and AlCl3.Similarly, the reductions of the ions Co2+, Ni2+, and Cd2+ as well as Zr4+ have been investigated in solvent melts containing various amounts of CsCl and ZnCl2.Well-defined limiting currents have been obtained in all systems. These were found to vary linearly with the concentration of the solute. From the slopes of Evs. log (iL − i), or log i/(iL − i), the electrode reactions were established in most cases. The analysis of the results for Zr4+ indicates a three step reduction process.
Effects of substitution on nitrogen on barriers to rotation of cyclic amides. Part I. Investigation of the rotational barier in 4-benzoyl-1-thia-4-azacyclohex-2-ene by 1H dynamic nuclear magnetic resonance spectroscopy
Authors: Grindley T. Bruce , Pinto B. Mario , Szarek Walter A.
Published: May 2006

The rotational barrier in 4-benzoyl-1-thia-4-azacyclohex-2-ene has been investigated by total line-shape analysis of variable temperature 1H nmr spectra in acetonitrile-d3. Separate treatment of the vinyl and methylene signals yielded sets of values for activation parameters which were in excellent agreement. Assignment of the major and minor rotational isomers was made from chemical-shift data derived from the 13C nmr spectrum at 243 K in acetonitrile-d3.
Conformational analysis of 2-substituted methylenecyclohexanes and 3-substituted cyclohexenes and the anomeric effect
Authors: Lessard Jean , Tan Phan Viet Minh , Martino Robert , Saunders John K.
Published: May 2006

The analysis of the 13C and 1H nuclear magnetic resonance data of 2-substituted methylenecyclohexanes and 3-substituted cyclohexenes demonstrates that a double bond stabilizes the axial conformer for an electronegative substituent. Introduction of a methoxy group on the double bond further increases the relative stability of the axial conformer. These results are interpreted in terms of the 'double bond – no bond' resonance.
Secondary α-ferrocenyl substituted carbocations from tertiary carbinols
Authors: Lee Choi Chuck , Chen Shi-Chow , Pannekoek W. Jack , Sutherland Ronald G.
Published: May 2006

The same secondary ferrocenylisopropylcarbenium ion was formed from treatment with concentrated H2SO4 at 10 °C of either ferrocenylisopropylcarbinol or ferrocenylmethyldimethylcarbinol and the same secondary ferrocenyldiphenylmethylcarbenium ion was obtained when either ferrocenyldiphenylmethylcarbinol or ferrocenylmethyldiphenylcarbinol was treated with CF3COOH at 5 °C. The results indicate the occurrence of 1,2-hydride shifts converting tertiary to secondary carbocations.
The synthesis of D-angolosamine
Authors: Baer Hans H. , Georges Fawzy F. Z.
Published: May 2006

The synthesis of 2,3,6-trideoxy-3-dimethylamino-D-arabino-hexose hydrochloride (10) (D-angolosamine, a constituent of the antibiotic, angolamycin) is described. First, a simplified procedure for the preparation of methyl 6-deoxy-α-D-glucopyranoside from methyl α-D-glucopyranoside is recorded. The deoxy derivative served as the starting point for sequential preparation of methyl 3,6-dideoxy-3-nitro-α-D-glucopyranoside (1), its 2,4-diacetate (2), its 4-monoacetate (3), its 2-O-mesyl-4-acetate (4), its 2-mesylate (5), and methyl 2,3,6-trideoxy-3-nitro-α-D-erythro-hex-2-enopyranoside (6) essentially according to procedures previously established (in part, in the L-series). Treatment of 5 or 6 with sodium borohydride produced methyl 2,3,6-trideoxy-3-nitro-α-D-arabino-hexopyranoside (7). Catalytic hydrogenation of 7 gave the corresponding 3-amino glycoside hydrochloride (8) which was hydrolyzed to furnish 3-amino-2,3,6-trideoxy-D-arabino-hexose hydrochloride (9) (D-acosamine, the enantiomer of a component of the antibiotic, actinoidin). N,N-Dimethylation of 8 followed by hydrolysis afforded the crystalline title compound (10).
Nuclear magnetic resonance investigation of the conformational dynamic properties of benzocycloheptenones and related compounds
Authors: Bodennec G. , St-Jacques M.
Published: May 2006

Free energy barriers for ring inversion were determined from dnmr studies of 3,4-benzo-cycloheptenone (4) and for deuterated derivatives 6 and 7 of 4,5-benzocycloheptenone (5). The investigation of 2,3-benzocycloheptenone (3) revealed negative results. The magnitude of ΔG≠ for 4 and the trend observed for 5, 6, and 7 strongly suggest that the chair conformation of these molecules interconverts through a wagging motion of the C(5) end of the benzocycloheptene seven-membered ring.
The photoreduction of hexaaquoiron(III) perchlorate in the presence of tertiary aliphatic alcohols. The effect of added copper
Authors: Carey John H. , Oliver Barry G. , Langford Cooper H.
Published: May 2006

The irradiation of ferric perchlorate in the presence of tert-amyl alcohol produces Fe(II) with a quantum yield of 0.110 ± 0.002, 12% lower than the yield obtained when tert-butyl alcohol was used as scavenger. Other tertiary alcohols studied, 3-methyl-2-pentanol and 3-ethyl-3-pentanol, exhibited similar lower yields. It is shown that this reduction is due to the formation of γ-hydroxyalkyl radicals which do not reduce ferric ion to ferrous. The addition of copper causes these radicals to be oxidized. The Fe(II) quantum yield for the irradiation with tertiary amyl alcohol as scavenger in the presence of copper is in good agreement with the tertiary butyl alcohol results in the absence of copper (0.124 ± 0.003).Quantum yields are observed which are independent of scavenger concentration indicating outer sphere photooxidations are not taking place. This result supports the suggestion that an H on the carbon bearing oxygen is necessary for direct reaction between scavenger and the ferric charge transfer excited state.
An examination of two solvation parameters: ΔCp≠ and 'm'
Authors: Mohanty Rajani Kanta , Robertson Ross Elmore
Published: May 2006

The empirical 'm' values from the Grunwald–Winstein solvent correlation equation for SN displacement reactions show a fair correlation with corresponding ΔCP≠ values obtained from hydrolysis in water. The correlation plots separate according to the nature of the displaced groups, a consequence of different relative effects of anions on water structure. The mechanistic significance of the correlation is examined.
Extremal arrangements of points and unit charges on a sphere: equilibrium configurations revisited
Authors: Melnyk Theodor William , Knop Osvald , Smith William Robert
Published: May 2006

We review the formulation and solutions of a number of extremal problems associated with points and unit charges on the surface of a sphere in E3. For one of these problems, namely[Formula: see text]where dpq is the Euclidean distance between points P and Q and m is the number of points, we discuss the results for m ≤ 16 and 1 ≤ n ≤ ∞. For the cases m = 5, 11, 13–16 we find hitherto undiscovered solutions. Our solutions for m = 5 and 11 correct earlier results in the literature. We also sharpen the existing literature results for m = 7 and 10.
Studies in the usnic acid series. VII. The biodegradation of (+)-usnic acid by a Pseudomonas species. Isolation, structure determination, and synthesis of (+)-6-desacetylusnic acid
Authors: Kutney James P. , Leman Jeffrey D. , Salisbury Phillip J. , Sanchez Ignacio H. , Yee Trevor , Bandoni Robert J.
Published: May 2006

Studies on the biodegradation of (+ )-usnic acid (1) by a Pseudomonas species have revealed a novel aromatic deacylation process. The isolated metabolite, (+)-6-desacetylusnic acid (2) is crystalline and its structure is established by means of spectroscopic and chemical methods. The synthesis of 2 from usnic acid (1) is also reported and provides conclusive evidence for the structure of this metabolite.
Broad band absorption of solutes in liquid solutions and in polystyrene
Authors: McLellan C. K. , Walker S.
Published: May 2006

Broad band absorptions in the frequency range 20 to 100 cm−1 arising from four polar solutes in polystyrene matrices have been observed at 302 K and compared with those in liquid benzene or cyclohexane solutions. A broad band was also found for 1,4-diacetylbenzene in a polystyrene matrix at 124 K. The broad band absorption still occurs in the far-infrared region when group and/or molecular relaxation(s) occur in appreciably lower frequency regions. The significance of these absorptions is discussed in terms of some models which account for the origins of broad band absorptions.
Structure and synthesis of a new cyclopentenone derivative from Trichodermaalbum
Authors: Strunz George M. , Ren Wu-Yun , Stillwell Merlyn A. , Valenta Zdenek
Published: May 2006

A dextrorotatory product isolated from cultures of Trichoderma album has been identified as 5-hydroxy-3-methoxy-5-vinyl-2-cyclopenten-1-one, and a synthesis of the latter in racemic form is described. The possibility that this compound might be an artifact produced during the isolation procedure, rather than a true metabolite, is not excluded.
Photoisomerization of some bicyclooctanones in solution
Authors: Critch Susan C. , Fallis Alex G.
Published: May 2006

The ketene derived products and unsaturated aldehydes produced upon solution photolysis of a series of bicyclooctanones (bicyclo[2.2.2]octan-2-one (1), bicyclo[3.2.1]octan-2-one (6), l,8,8-trimethylbicyclo[3.2.1]octan-2-one (12)) are reported. Estimated strain energies of the approximate transition states involved and conformational analysis are utilized as guides to rationalize the results. This approach should assist more accurate predictions of photolysis products from related systems in the same solvent(s). The product ratios are solvent sensitive and preliminary experiments indicate that a primary amine (cyclohexylamine) in the photolysis solution enhances the production of ketene derived product.
Approaches toward the conformational analysis of carbocyclic hydroxyphosphono compounds: 13C–31P couplings and carbon shieldings
Authors: Buchanan Gerald W. , Morin Frederick G.
Published: May 2006

13C nmr chemical shifts and 13C–31P couplings through one, two, and three bonds are reported for twelve carbocyclic hydroxyphosphonates and alkyl derivatives with all ring sizes from four to twelve, except the cyclodecyl system. On the basis of the vicinal couplings and carbon shieldings, inferences regarding preferred conformations are drawn. Evidence for ring flattening in some cyclohexyl compounds is presented. For a given ring size, it is demonstrated that 1Jcp becomes less positive as the degree of steric congestion about the C—P bond increases.
Benzannelated annulenes. II. The synthesis of trans-12b,12c-dimethyl-12b,12c- dihydrobenzo(e)pyrene. An indication of the exceptional aromaticity of the 15,16-dimethyldihydropyrene system
Authors: Mitchell Reginald H. , Yan Joseph Shue-Hen
Published: May 2006

The synthesis of trans-12b,12c-dimethyl-12b,12c-dihydrobenzo(e)pyrene 4, in 10 steps from o-dibromobenzene and 2,6-dichlorotoluene utilizing a Wittig rearrangement – Hofmann elimination sequence on the benzothiacyclophane 6 is described. The diatropicity of 4 is compared to the parent trans-10b,10c-dimethyl-10b,10c-dihydropyrene 1, and to other benzannelated annulenes.
Consecutive reactions in the thermal decomposition of phenylalkyldiazirines
Authors: Liu Michael T. H. , Jennings Barry M.
Published: May 2006

The thermal decomposition of phenyl-n-butyldiazirine and of phenylmethyldiazirine in DMSO and in HOAc have been investigated over the temperature range 80–130 °C. The intermediate diazo compounds, 1-phenyl-1-diazopentane and 1-phenyldiazoethane respectively have been detected and isolated. The decomposition of phenyl-n-butyldiazirine and the subsequent decomposition of its product, 1-phenyl-1-diazopentane, are an illustration of consecutive reactions. The kinetic parameters for the isomerization and decomposition reactions have been determined. The isomerization of phenylmethyldiazirine to 1-phenyldiazoethane is first order and probably unimolecular but the kinetics for the subsequent reactions of 1-phenyldiazoethane are complicated by several competing rate processes.
Concerning the nonexistence of the intramolecular hydrogen bond in 2-nitrothiophenol
Authors: Schaefer Ted , Parr William J. E.
Published: May 2006

The long-range spin–spin coupling constants between the sulfhydryl proton and the ring protons in 2-nitrothiophenol in CDCl3 and C6D6 solutions suggest the presence of two conformers in which the S—H bond prefers the benzene plane. The conformer in which the S—H bond lies trans to the nitro group is favoured over the cis conformer by a free energy difference of 0.5 ± 0.2 kcal/mol at 305 K. Apparently any intramolecular hydrogen bond is very weak compared to that in 2-nitrophenol.