bluuebunny/crossref_metadata_2025 huggingface dataset:
Five-coordinate iron and manganese dinitrosyl complexes incorporating tridentate chelating dimethyl(N,N-dimethylethanolamino)(pyrazolyl)gallate ligands: crystal and molecular structure of [Me2Ga(N2C5H7)(OCH2CH2NMe2)]Fe(NO)2
Authors: Chong Kenneth S. , Rettig Steven J. , Storr Alan , Trotter James
Published: May 2006

Novel neutral monomeric five-coordinate manganese and iron dinitrosyl compounds incorporating asymmetric tridentate anionic gallate ligands are described. The crystal structure of the formally "19-electron" iron complex [Me2Ga(N2C5H7)(OCH2CH 2NMe2)]Fe(NO)2 has been determined. Crystals of [dimethyl(N,N-dimethylethanolamino)(3,5-dimethylpyrazolyl)gallato (N(2),N(3),O)]dinitrosyliron(I) are monoclinic, a = 7.3079(6), b = 14.274(1), c = 17.076(1) Å, β = 91.709(4)°, Z = 4, space group P21/c. The structure was solved by Patterson and Fourier syntheses and was refined by full-matrix least-squares procedures to R = 0.034 and Rw = 0.046 for 2848 reflections with I ≥ 3σ(I). The crystal structure consists of discrete monomeric units. The coordination geometry about the iron atom is distorted trigonal-bipyramidal with the tridentate gallate ligand acting in a meridional fashion, occupying one equatorial and both axial positions. The two nitrosyl groups occupy the other two equatorial sites and both Fe—N—O groupings are considerably bent toward one another in the equatorial plane. Important mean molecular dimensions (distances corrected for libration) are: Fe—O, 2.037(3), Fe—N(pyrazolyl), 2.112(3), Fe—N(amino), 2.279(3), Fe—NO, 1.710(3), N—O, 1.153(5), Ga—O, 1.916(3), Ga—N, 1.975(3), Ga—C, 1.972(6) Å, and Fe—N—O, 158.6(7)°.
Solvent extraction of monothioacetylacetone chelates of zinc(II) and nickel(II)
Authors: Leban Marzio , Jeffries David , Fresco James
Published: May 2006

The formation constants of nickel(II) and zinc(II) monothioacetylacetonates have been determined as 2.95 × 1012 and 6.46 × 1010 respectively. These are about 700 times more stable than the corresponding acetylacetonates. Both monothioacetylacetonats were more than 99% extracted into chloroform and ligand hydrolysis was not significant before completion of metal ion extraction.
Preparation and 31P nuclear magnetic resonance studies of chiral phosphines
Authors: Payne Nicholas C. , Stephan Douglas W.
Published: May 2006

The reaction of Li metal with alkyldiphenylphosphines generates the alkylphenylphosphide anions, which can undergo subsequent reactions with alkyl halides to give chiral phosphines (RR′R″P). The 31P nmr chemical shifts have been measured for these phosphines, and show greater deviations from the values predicted by the first order additivity model than do those of more symmetrical phosphines (i.e., R3P and R2R′P). The shifts for these chiral molecules, and for a wide range of other phosphines, can be accurately predicted using a second order pairwise additivity scheme. The dependence of the observed and calculated chemical shifts upon electronegativity and steric factors is discussed.
Réactions d'addition nucléophiles sur les cétones. Mise en évidence d'un effet directionnel d'origine stérique dans l'effet isotopique secondaire du deutérium
Authors: Boyer Bernard , Lamaty Gérard , Roque Jean-Pierre , Geneste Patrick
Published: May 2006

A kinetic study of the addition reactions of borohydride and sulfite ions and of hydroxylamine to a number of stereospecifically deuterated carbonyl compounds (3,3,5,5-tetramethyl cyclohexanone, 7,7-d2-bicyclo[2,2,1]-2-bornanone) leads to the observation of a distant secondary deuterium isotope effect. The results obtained reveal the intervention of a directional effect in the steric origin of these isotope effects. In particular, this study shows the importance of the orientation of the vibrations brought into play by a C—D bond during the reaction process. (Journal translation)
Molecular motion and methyl group rotation barriers from 13C nmr relaxation times. Norbornane and adamantane derivatives in solution
Authors: Beierbeck Helmut , Martino Robert , Saunders John K.
Published: May 2006

The carbon-13 relaxation time data for several norbornane and adamantane derivatives are presented. It is shown that the most probable principal axis of the rotational diffusion tensor is an axis which contains the centre of mass of the molecule and the heterosubstituent. The influence of the C—Ĉ—H bond angle on the calculation of methyl group rotation barriers from relaxation time data and on the barrier is discussed.
A homopropargyl radical rearrangement. Kinetics of the rearrangement of the 2,2,5,5,-tetramethyl-3-hexyn-1-yl radical
Authors: Ingold Keith U. , Warkentin John
Published: May 2006

The rate constants for rearrangement of the 2,2,5,5-tetramethyl-3-hexyn-1-yl radical to the 2,6,6-trimethyl-4-heptyn-2-yl radical have been measured from 45 to 88 °C by kinetic epr spectroscopy. The temperature dependence can be represented by[Formula: see text]where θ = 2.3RT kcal mol−1. This rearrangement, which must involve an intermediate vinyl radical of the methylenecyclopropane type, is much slower than analogous rearrangement of homoallyl radicals but comparable in rate to rearrangement of homobenzyl (neophyl) radicals.
Sulfur-bonded sulfoxide complexes of rhodium(III) and rhodium(I)
Authors: James Brian R. , Morris Robert H.
Published: May 2006

Aqueous 2-propanol solutions of RhCl3•3H2O on treatment with sulfoxides yield mer-RhCl3L3 complexes, the sulfoxide L being dimethyl (DMSO), tetramethylene (TMSO), methyl phenyl (MPSO), or (R)-methyl-p-tolyl (MPTSO); with diphenyl sulfoxide (DPSO), a [RhCl(DPSO)2]2 complex with S-bonded sulfoxide is obtained via the propanol reduction of a Rh(III) intermediate. The mer-rhodium(III) complexes in solution contain two sulfur-bonded sulfoxides (R2SO), and one oxygen-bonded sulfoxide (R2SO) that is trans to a (R2SO) ligand. The DMSO ligand in mer-RhCl3(DMSO)2(DMSO) is displaced by amides, amine oxides, and phosphine oxides; the DMSO cis to the oxygen-bonded ligands is identified in nmr by using the ring current shielding effects of OPPh2Me. Salts of [RhCl4(R2SO)2]− have been obtained with n-propyl sulfoxide and DMSO using several cations, including the symmetrically hydrogen-bridged species, [R2SO—H—OSR2]+. The cyclooctene precursor [RhCl(C8H14)2]2 has been used to synthesize [RhCl(DPSO)(C8H14)]2, [RhCl(DMSO)2]2, and [RhCl(DIOS)2]2, where DIOS is (2R,3R)-2,3-isopropylidene-2,3-dihydroxy-1,4-bis(methylsulfinyl)butane. The nature of rhodium–sulfur bonding is discussed, especially in terms of a contribution of metal–sulfur π-backbonding.
Effet de cation sur la réactivité ambidente des anions: la nette tendance à la O-alkylation manifestée par les énolates de lithium de composés β-dicarbonylés
Authors: Sarthou P. , Bram G. , Guibe F.
Published: May 2006

The study of the specific reactivity of the ion pairs of alkaline enolates of β-dicarbonyl compounds shows that the lithium enolates, in spite of their characteristically strong enolate–cation interactions display, especially when compared to sodium enolates, a marked tendency towards O-alkylation. This strong O-/C-nucleophilicity of the lithium ion pairs is not very sensitive to changes in medium polarity (from THF or DME to DMF) but depends on the nature of the alkylating agent, being enhanced with moderately electrophilic alkyl sulfonates or sulfate but lessened with alkyl halides or with very electrophilic sulfonates (triflate). It is suggested that the lithium enolate tendency towards O-alkylation is partly the result of a Li+ – leaving group interaction (especially in the case of the sulfonates) and partly an intrinsic property of the enolate–lithium ion pair; this latter property is discussed in terms of the respective solvation abilities towards cations of the C- and O-alkylation transition states.Some of our results about the nucleophilic reactivity of ion pairs in DMF are at variance with previous reports in the literature. The origin of the discrepancy is discussed.
Volumetric and thermochemical properties of ionic surfactants: sodium decanoate and octylamine hydrobromide in water
Authors: Lisi Rosario De , Perron Gérald , Desnoyers Jacques E.
Published: May 2006

The heat capacities per unit volume and the densities of sodium decanoate (NaDec) in water were measured as a function of concentration and temperature in the range 0.5 to 45 °C. Similar data were obtained for octylamine hydrobromide at 5 and 15 °C. Enthalpies of dilution of NaDec in water were measured at 25 °C. From these and previously published data the apparent and partial molal heat capacities, expansibilities, volumes, and relative enthalpies were determined as a function of temperature and concentration. The concentration dependence of [Formula: see text] and [Formula: see text], is similar to that of other surfactants such as alkyltrimethylammonium bromides and sodium dodecyl sulfate, but in contrast with the other surfactants, [Formula: see text] goes through a sharp maximum in the micellization region at the lower temperatures. These thermodynamic properties can be analysed with a phase-separation model to give the changes in volume, heat capacity, and enthalpy during micellization as a function of temperature. The limitations of this model are also discussed.
Factors influencing the nature of seleniranium ions in selenenyl chloride additions to alkenes: the use of methanol as solvent
Authors: Garratt Dennis G. , Kabo Ann
Published: May 2006

The reaction of benzeneselenenyl chloride with some simple alkylsubstituted acyclic and cyclic alkenes has been investigated using methanol as the solvent. Products of solvent-incorporation, (β-methoxyalkyl phenyl selenides, are normally favoured over the analogous chloro species, but exceptions have been noted. The observation of products of solvent-incorporation, Wagner–Meerwein rearrangement, and homoallylic rearrangement is in accord with an AdE2 mechanism involving both intimate and solvent-separated ion-pairs prier to the product forming step.
Substituent positional effect on radiative lifetimes of anthracene sulphonates
Authors: Gupta A. K. , Basu Sekhar , Rohatgi-Mukherjee K. K.
Published: May 2006

Excited state lifetimes of anthracene-1-sulphonate, anthracene-2-sulphonate, anthracene-1,5-disulphonate, and anthracene-1,8-disulphonate have been studied by photoselection and single photon counting methods. Experimental lifetimes are compared with theoretical values. For anthracene- monosulphonates, exciplex formation with water is proposed. In the case of anthracene-1,8-disulphonate, distortion in molecular geometry is found responsible for the higher non-radiative decay constant. Summation of nonradiative decay constants, Σki, increase in the series [Formula: see text]. The sharp increase for 1,8-AS is perhaps due to distortion of the molecular geometry due to steric effect of two bulky and charged —SO3− groups on the same side of the anthracene skeleton.
Interaction of divalent metal ions with pyridoxal phosphate. I. Nuclear magnetic resonance studies of cobalt(II) binding
Authors: Viswanathan Tenkasi S. , Swift Terrence J.
Published: May 2006

The binding of Co(II) to pyridoxal phosphate (PLP)at neutral pH was investigated with 31P, 1H, and 13C nmr spectroscopy. The proton and phosphorus spin–lattice relaxation times of PLP were measured in the absence of Co(II) and with increasing amounts of the metal ion. The shifting and the relaxation enhancement of the phosphorus resonance in the presence of Co(II) have indicated the binding of the metal ion to the phosphate of PLP. The addition of metal ion also shifted and broadened the proton and carbon resonances. The shifting and broadening was the largest for the 4-CHO proton with other protons following the order 4-CHO [Formula: see text] 2-methyl > 5-methylene > 6-H. At neutral pH Co(II) shifted only the 5-methylene proton resonance of pyridoxamine phosphate (PMP) indicating binding of Co(II) only to the 5′-phosphate of PMP at this pH. Comparison of the shifting and broadening of the proton resonances of PLP with similar shifts in model compounds has indicated a structure for the 1:1 PLP:Co(II) complex in which the metal ion is simultaneously bound to the phosphate and the aldehyde oxygen. The proton spin–lattice relaxation times and the isotropic shifts of the 13C resonances in the 1:1 PLP:Co(II) complex support this conclusion.
Effect of the acyl substituent on the equilibrium constant for hydration of esters
Authors: Guthrie J. Peter , Cullimore Patricia A.
Published: May 2006

Heats of hydrolysis have been measured for the trimethyl orthoesters of isobutyric, propionic, benzoic, methoxyacetic, chloroacetic, and cyanoacetic acids using aqueous acid with an organic cosolvent where necessary, and of the corresponding esters in alkaline solution. Solubilities or free energies of transfer from gas to aqueous solution have been measured, permitting calculation of the free energies of formation of the aqueous orthoesters, and by methods which we have published previously, calculation of the free energies of formation of the covalent hydrates of the esters, and the free energy changes for hydration of these esters.Using estimated pKa values equilibrium constants were calculated for the addition of hydroxide to the esters. The data are in good agreement with the appropriate Marcus equation relating rate and equilibrium constants with a value for b of 8.99 ± 0.17. This line was used to estimate the equilibrium constant for addition of hydroxide, and thence of water, to some additional esters where only the rate constant was available. Rate constants for hydrolysis of methyl esters in aqueous solution at 25 °C were calculated from literature data, correcting for the effect of other conditions as necessary. From the equilibrium constants for addition of water we could estimate the rate constants for uncatalyzed hydrolysis; for the cases where this rate constant has been measured, the agreement was satisfactory. For acid catalyzed hydrolysis the data permit a test of the two alternative mechanisms considered previously, namely specific acid catalysis and general acid catalysis with hydronium ion acting as a general acid. For esters the mechanism is clearly specific acid catalysis, but for aldehydes and ketones it appears very likely that the mechanism is general acid catalysis.
Etude par la résonance de l'azote 15 et du phosphore 31 de la liaison P—N dans des dérivés du phosphore trivalent; analyse statistique des données expérimentales
Authors: Gouesnard Jean-Paul , Dorie Jean , Martin Gérard J.
Published: May 2006

Natural abundance 15N and 31P nmr and dynamic 13C nmr have been applied to the study of about fifty aminophosphines, in order to generalize the influence of the chemical factors which govern the electronic distribution of the nitrogen–phosphorus III bond. Factor and regression analyses of δ15N, δ31P, and 1JP—N values performed on different series of aminophosphines have shown that common factors and various correlations exist between the nmr parameters in the different kinds of derivatives. The statistical results are discussed in terms of topologic, electronic, and steric contributions. The nature of the different substituents of the nitrogen or phosphorus atoms governs the observed changes in screening, coupling constants, and the rotational barriers ΔG≠ around the P—N bond, which are explained in considering the type of nitrogen and phosphorus hybridization, the pπ–dπ donation and the electronic states (ΔE−1 approximation) of the P—N fragment.
Infrared spectra of the ammonium ion in crystals. Part IX. Ammonium tetraphenylborate, NH4B(C6H5)4: crystal structure at room temperature and at 120 K, and evidence of hydrogen bonding
Authors: Westerhaus Wolfgang J. , Knop Osvald , Falk Michael
Published: May 2006

A determination of the crystal structure of ammonium tetraphenylborate (ATPB) at 120 K shows that the ammonium ion in this crystal, at a site of symmetry D2d, is oriented in a way consistent with the expectation from a simple model based on Coulombic interaction. Infrared spectra of the isotopic ammonium ions obtained between 10 K and room temperature indicate that the effect of the tetraphenylborate anion on the strength of the N—H bond (as measured by the stretching frequency) is small and independent of temperature, and that the distortion of the ammonium ion from Td symmetry is slight. From the combined evidence it is concluded that the ammonium ion in ATPB must be regarded as hydrogen-bonded, but the potential field due to the four phenyl rings surrounding the ammonium ion offers little resistance to the bending (and probably also to the librational) motion of the ion.
Potentiometric properties of trialkylammonium ion-exchangers
Authors: Gérin Michel , Fresco James
Published: May 2006

The potentiometric behaviour of nitrobenzene solutions of 21 trialkylammonium salts employed as membrane material has been investigated. Deviations from ideal Nernst response curves for chloride, bromide, iodide, and perchlorate sensors were explicable on the basis of partition and hydrolysis of the ion exchangers. Interference coefficients for the anion selective electrochemical sensor tridodecylammonium perchlorate could be related to the ion-exchange constant of the salt.
Electron spin resonance study of spin-trapped azide radicals in aqueous solutions
Authors: Kremers Walter , Singh Ajit
Published: May 2006

Organic spin traps have been used to study the formation of azide radicals during the reaction of azide anions with hydroxyl radicals. The azide radicals have been successfully trapped with three spin traps: 5,5-dimethylpyrroline-1-oxide (DMPO), phenyl-N-tert-bulyl nitrone (PBN), and 4-pyridyl-N-tert-butyl nitrone (PyBN). The azide radicals produced from 15N sodium azide have also been trapped. The hyperfine splittings of the resulting radicals have been determined.
A wavelength specifie photo-electric detecter
Authors: Stephens R.
Published: May 2006

A photo-electric detector is described which is capable of showing selectivity towards atomic resonance radiation. Details are given of the construction of such a device suitable for use with the mercury 253.7 nm line. A possible mechanism for the operation of the detector is considered. Its spectral selectivity is illustrated by an examination of the atomic absorption signals obtained with a partially reversed line source.
A 31P nuclear magnetic resonance spectroscopic study of some 2:1,3:1, and 4:1 complexes of phosphine sulfides and selenides with cadmium(II), including some complexes with mixed ligands
Authors: Dean Philip A. W. , Polensek Lijana
Published: May 2006

Using low-temperature 31P nmr, many new complexes formed between divalent cadmium (as Cd(SbF6)2) and monodentate phosphine chalcogenides in liquid SO2 have been characterized. A 4:1 (L:M) complex is formed with Bu′3PS and, possibly, Bu′3PSe. 4:1 and 3:1 complexes are formed with Ph3PE, (o-C6H4Me)Ph2PE, (p-C6H4Me)3PE, and (C6H11)3PE (E = S or Se) as well as (o-C6H4Me)2PhPSe, while 4:1, 3:1 and 2:1 complexes occur for (o-C6H4Me)3PE (E = S or Se), and, probably, (o-C6H4Me)2PhPS. In addition, ail the mixed ligand complexes in the series [Cd(SeP(C6H11)3)n(SP(C6H11)3)4–n]2+, [Cd(SeP(C6H11)3)n(SP(C6H11)3)3–n]2+, and [Cd(SeP(o-C6H4Me)3)n(SP(o-C6H4Me)3)3–n]2+ have been identified.Trends in the 31P nmr data are discussed.
Thermolysis of alkylated 2-cyclohexenones and related monoterpenoid ketones
Authors: Lange Gordon L. , Pereira Vincent A. , Weedle Michael
Published: May 2006

2-Cyclohexenone and three methylated cyclohexenones were thermolyzed at 400 °C for 20 hours to give conversions to products in the range 11 to 45%. When three monoterpenes containing the cyclohexenone moiety were thermolyzed under the same conditions the conversions were over 75%. The major products formed were alkylated benzenes, alkylated phenols, and double bond isomers of the starting enones. Mechanisms are proposed to account for these products.
The formation and reactions of aromatic dimer cations in a high pressure photoionization source
Authors: Stone John A. , Lin Margaret S.
Published: May 2006

Aromatic dimer cations (M2+) have been generated for a series of aromatic compounds in a high pressure photoionization source. Relative third order rate constants for formation of M2+ have been obtained for benzene (1.0), benzene-d6 (2.7), toluene (0.8), o-xylene (1.5), p-xylene (0.7), fluorobenzene (0.3), m-fluorotoluene (0.5), m-chlorotoluene (0.7), p-chlorotoluene (0.5), and o-methoxytoluene (0.4). These values are consistent with and supplement previous data for such systems. Reagent ion monitoring has been used to determine the relative rates of reaction of both M2+ and the monomer ions, M+, with a series of (mainly) aromatic compounds (X). Reaction of C6H6+ is by charge transfer to compounds of lower ionization potential than C6H6. (C6H6)2+ reacts only by charge transfer, if the ionization potential of X is more than 0.5 eV lower than that of benzene. When the difference is smaller, mixed dimer cations are observed which are probably formed in a switching reaction (C6H6)2+ + X → (C6H6•X)+ + C6H6.
An experimental evaluation of simplified procedures for determining the proton spin–lattice relaxation rates of natural products
Authors: Colebrook Lawrence D. , Hall Laurance D.
Published: May 2006

A general discussion is given of the determination of the proton spin–lattice relaxation rates of natural products, with particular emphasis on use of the null-point method which, for the systems studied here, gives identical results with those obtained via the conventional (and relatively time consuming) computational method.
The mechanism of the reaction of the Nash and the Sawicki aldehyde reagent
Authors: Compton Bruce Jon , Purdy William C.
Published: May 2006

Synthetic and chromatographic studies are presented on the Nash and Sawicki colorimetric methods for quantitating formaldehyde. It is shown that the actual color-forming agent in the Nash method is an isolable iminodione formed insitu by reaction of the two components. Explanation is given for differences between these two methods.
Deuterium and phosphorus-31 nuclear magnetic resonance of cholesteryl palmitate in dipalmitoylphosphatidylcholine model membranes
Authors: Cushley Robert J. , Gorrissen Heiner , Wassall Stephen R.
Published: May 2006

Cholesteryl palmitate (CP) bas been incorporated into vesicles of dipalmitoylphosphatidylcholine and dipalmitoylphosphatidylcholine/20 mol% cholesterol, in amounts up to 5 mol%. By means of 31P lanthanide induced shifts the average diameter of these vesicles was calculated to be ~270 Å.The 2H spectral linewidths of selectively deuterated CP incorporated into liquid crystalline dipalmitoylphosphatidylcholine vesicles are ≤ 150 Hz, implying a low degree of order for the ester acyl chain. Addition of 20 mol% cholesterol to the vesicles increases the linewidths which, nevertheless, remain ≤ 185 Hz. The corresponding 2H longitudinal relaxation times (≤ 450 ms) indicate that the fast segmental motions of the ester chain are slower than for the phospholipid chains.
Electrophilic additions to allenes. VII. The role of steric versus electronic effects in the reactions of areneselenenyl halides with allenes
Authors: Garratt Dennis G. , Beaulieu Pierre L. , Morisset Veronique M. , Ujjainwalla Mark
Published: May 2006

The reactions of benzeneselenenyl chloride, bromide, and 2,4,6-trimethylbenzeneselenenyl bromide with alkyl 1,3-disubstituted allenes in methylene chloride solution have been investigated. While kinetic data are in accord with similar rate determining transition states, exhibiting strong steric effects for ail three species, the product distributions show changes in both chemoselectivity and configurational-selectivity in accord with two different types of steric interaction mechanisms during the product determining transition states. A mechanism involving rate limiting formation of alkylideneseleniranium ions and/or alkylideneepiselenuranes, followed by isomerization between the alkylideneseleniranium ions by a path not involving allylic ions, prior to the product determining transition states, is proposed.
Activity coefficients, densities, dipole moments, and surface tensions of the system triethylamine–methylethylketone–water
Authors: Campbell Alan N.
Published: May 2006

The properties named in the title have been determined by standard methods. Viscosity, molar volume, and orientation polarisation all indicate abnormalities of the nature of association between the components.The most interesting result is that of surface tension which indicates that, in the case of the binary system triethylamine–water, a surface layer of constant composition is formed over a wide range of total composition. When, by a rise in temperature of two or three degrees, this layer becomes unstable, it splits into two phases of different composition. The surface layer may then be instantaneously reformed and so on. A mechanism for the generation of a two-phase system is thus established. The data for the three-phase, isothermal, system are not so convincing, for reasons that are suggested.
Dielectric absorption of a few aromatic amines in a polystyrene matrix
Authors: Tay S. P. , Walker S.
Published: May 2006

Dielectric absorption studies in the ranges 77–373 K and 102–107 Hz have been made on aniline, poly(4-aminostyrene), p-toluidine, 4-chloroaniline, 1-aminopyrene, and 4-aminobiphenyl in a polystyrene matrix. An intramolecular process has been observed in poly(4-aminostyrene) and 1-aminopyrene with enthalpies of activation of 25 and 26 kJ mol−1 respectively. The enthalpy of activation of the intramolecular process is of the same order as that found for the torsional barrier in aniline and 4-fluoroaniline. The most likely candidate for the intramolecular process appears to be rotation of the amino group about the carbon–nitrogen bond.
Fission fragment radiolysis of carbon dioxide
Authors: Ikezoe Yasumasa , Sato Shoichi , Shimizu Saburo
Published: May 2006

The fission fragment radiolysis of CO2 and the CO2–C3H8, CO2–NO2 systems is studied in comparison with the γ radiolysis. Two kinds of back reactions (re-oxidation of carbon monoxide to carbon dioxide) are operative in the fission fragment radiolysis. One (a rapid back reaction) is the unidentified ionic chain reaction which proceeds at low CO concentrations, and the other (a slow back reaction) is assigned to a radical reaction (CO + O + CO2 → 2CO2 [3′]). This slow back reaction is a characteristic of the fission fragment radiolysis. The analysis of results gives an upper limit of the radius of fission fragment tracks in the reaction system, rρ < 1.04 μg cm−2.
Kinetics and mechanism of the thermal decomposition of N-nitrosodiphenylmethylimine
Authors: Liu Michael T.H. , Ibata Toshikazu
Published: May 2006

The thermal decomposition of N-nitrosodiphenylmethylimine has been investigated in various solvents. The decomposition products are benzophenone and nitrogen. The ΔH†and ΔS† parameters for these first-order decompositions have been determined. The experimental evidence is consistent with the hypothesis that the thermolysis of N-nitrosodiphenylmethylimine involves the formation of a cyclic transition state via an electrocyclic ring closure mechanism.
On the existence of intramolecular hydrogen bonds in methyl o-mercaptobenzoate and 2-methoxymethylbenzenethiol
Authors: Schaefer Ted , McKinnon David M. , Sebastian Rudy , Krawchuk Bert
Published: May 2006

Full analyses of the 1H nmr spectra of methyl o-mercaptobenzoate and of 2-methoxymethylbenzenethiol yield spectral parameters suggesting that the trans conformer of the former is preferred by 1.6 ± 0.7 kJ/mol in free energy in solution at 305 K. Both cis and trans conformers can be reasonably discussed in terms of "planar" conformations. The ether displays nearly equal concentrations of cis and trans conformers. However, these conformers display considerable conformational freedom of the sulfhydryl group. These results are compared to previous infrared data. It is suggested that in the ester the small tendency towards intramolecular hydrogen bonding involves the carbonyl oxygen. Any [Formula: see text] interaction in the ether must surely occur for conformations in which the S—H and C—O bonds are far from the ring plane.
129I Mössbauer spectra of tellurium iodides. Part II
Authors: Dance Nigel S. , Jones Colin H. W.
Published: May 2006

The 129I Mössbauer spectra of PhTeI, p-EtOPhTeI2−, p-EtOPhTeI4−, Ph3TeI, (Me2TeI2)2•Ph2Hg, and Na2HgI4 have been measured and the data interpreted in terms of the bonding to tellurium in these compounds and ions. Evidence is presented that PhTeI is polymeric. The 129I coupling constants in p-EtOPhTeI2− and p-EtOPhTeI4− are very similar and are the same as those observed in other compounds containing linear I—Te—I linkages, lending support to the use of an additive model in interpreting 125Te quadrupole splittings. The compound Ph3TeI is best formulated as an ionic species. The compound formed on reaction of α-Me2TeI2 with Ph2Hg is concluded to be (Me2PhTe+)2HgI42−.
Studies in general acid and general base catalysis. Rate–acidity profiles for prototropic processes
Authors: Stewart Ross , Srinivasan R.
Published: May 2006

A theoretical study has been made of the effect of changing acidity on the rate of aqueous prototropic reactions. These processes, typified by ketone enolization, are catalyzed by general acids and bases and their log rate–pH profiles may take a number of different shapes. In the absence of buffer catalysis there are four reaction paths available to a substrate Z: ZH+ + HO−, Z + HO−, ZH+ + H2O, and Z + H2O. Equations have been derived that express the contributions each of these paths makes to the observed rate in terms of the experimental catalytic constants, the proton activating factor (paf), the deprotonating factor (dpf), and the basicity of the substrate as expressed by KZH+. For ideal systems the relative rates of the kinetically equivalent paths Z + H2O and ZH+ + HO− (though one does not know which is the larger) is given by the quantity [Formula: see text] where [Formula: see text], and [Formula: see text] are the experimental catalytic constants. It is argued in the case of the real substrate acetone that (a) this quantity underestimates the rate difference, and (b) the more important path is Z + H2O. Where paf is available from rate data determined in buffers an unequivocal choice can be made between the kinetically equivalent paths, provided paf is a constant for the particular substrate.
Crystal structure of raucubaine
Authors: Pauptit Richard A. , Trotter James
Published: May 2006

Crystals of raucubaine, isolated from Rauwolfia salicifolia C20H24N2O3, m.w. = 340.4, are monoclinic, p21, a = 7.2179(3), b = 12.8169(7), c = 9.1996(2) Å, β = 93.040(3)°, V = 849.87 Å3, ρc = 1.33 g cm−3, Z = 2, R = 0.046 for 1699 reflections. The previously-unknown structure of this alkaloid was determined.
Approaches to the synthesis of triterpenoids. VI. The synthesis of 3,3,10aβ-trimethyl-l,2,3,4,4aβ,5,8,9,10,10a-decahydrophenanthren-7(6H)-one, a potential intermediate for pentacyclic triterpene synthesis
Authors: ApSimon John W. , Moir David , Yamasaki Kazuyuki
Published: May 2006

Investigations of the CDE ring construction of naturally occurring triterpenoids are described. The efficient synthesis of 3,3,10aβ-trimethyl-1,2,3,4,4aβ,5,8,9,10,10a-decahydrophenanthren-7(6H)-one(25) has been achieved. The D/E ring junction of the molecule, as well as that of related compounds, has been established by the use of 13C nmr spectra. The synthetic intermediate 25 can be considered as a key substance for a synthetic entry to friedelin (1) in addition to β-amyrin (23).
Interaction électron–solvant dans la radiolyse-γ du N-methylacétamide et de ses mélanges à l'eau. Effet d'intercepteurs sélectifs
Authors: Tran-Thi T. H. , Koulkès-Pujo A. M. , Sutton J.
Published: May 2006

A study of the reaction mechanism of the γ-radiolysis of N-methyl acetamide (NMA) at 30 °C (dielectric constant 178) in the presence of various electron scavengers (N2O; HCl. 2NMA; (CH3)2CO) has shown that the attachment of a presolvated electron to NMA is a slow reaction compared to that of N2O with the same species. This attachment probably is dissociative. The rate constants of the "dry"electron with N2O, acetone (Ac), and NMA are in the following order[Formula: see text]
1,7-Dioxaspiro[5.5]undecanes. An excellent system for the study of stereoelectronic effects (anomeric and exo-anomeric effects) in acetals
Authors: Deslongchamps Pierre , Rowan Daryl D. , Pothier Normand , Sauvé Gilles , Saunders John K.
Published: May 2006

Several isomeric compounds derived from the spiro systems 5 to 9 (Scheme 4) were obtained from the acid cyclization of the appropriate dihydroxy ketone precursor.The configuration and the conformation of the products obtained was determined by 13C nmr analysis and equilibration studies. The experimental results can be rationalized by taking into account the anomeric and the exo-anomeric effects and the usual steric interactions.
Product distributions and isotopic selectivities in ir multiphoton dissociation of pentafluoroiodoethane
Authors: Weinberg E. , Gauthier M. , Hackett P. A. , Willis C.
Published: May 2006

Infrared multiphoton dissociation of pentafluoroiodoethane leads to a complex array of reaction products. For photolysis in the v4 band the reaction mechanism involves C2F5—I bond cleavage followed by thermal dissociation of C2F5 radicals. For irradiation within the v3 band at high fluence, efficient secondary photolysis of C2F5 radicals is postulated. At lower fluences the dissociation is isotopically selective leading to C4F10 enriched in carbon-13.
The relative rates of bromination of cyclohexane and cyclopentane with molecular bromine. Comparison of the reactions in solution and in vapor phase
Authors: Tanner Dennis D. , Ruo Tomoki C-S. , Takiguchi Hideki , Guillaume Andre
Published: May 2006

The relative rates of transfer of the cyclopentyl radical with molecular bromine and hydrogen bromide (k2′/k−1′) and with hydrogen tribromide and hydrogen bromide (k3′/k−1′) have been determined. The relative transfer rates are compared with the analogous values previously reported for the reactions of cyclohexyl radicals (k2/k−1 and k3/k−1). Utilizing the values of k2′/k−1 and k2/k−1 the competitive vapor phase rates of bromine atom abstraction of hydrogen from the two substrates could be obtained. An expression using a combination of the five sets of relative rate constants was used to determine the effect of competitive cage reversal which occurs in the solution phase bromination of the two substrate radicals with caged hydrogen bromide. For two structurally similar radicals, cage reversal (internal return) was found to affect the relative rates of bromination by 30%, while the relative transfer rates, although differing each by a factor of two, fortuitously nearly cancel each other's effect.The effect of both internal and external reversal reactions on the relative rates of bromination of structurally dissimilar substrates, halogenated alkanes and their parent hydrocarbons, is discussed.
A rapid method for the determination of bitumen, water, and solids in oil sands
Authors: Ball D. Lorne , Cooke E. D. , Cooley Jean M. , Hamilton M. Coreen , Schutte Robert
Published: May 2006

A simple and rapid method has been developed to measure the bitumen, water, and solids content of Athabasca oil sand samples in order to efficiently serve both plant operations and research needs. A solvent blend of 74% toluene and 26% isopropyl alcohol extracts both the bitumen and the water from the solids producing a homogeneous liquid phase. The bitumen is determined gravimetrically on an aliquot of this solution. A Karl Fischer titration is used to measure the water concentration. Solids are measured gravimetrically or can be reported by difference. Mass balances between 99.05 and 100.25% are achieved routinely.
Ion exchange properties of trialkylammonium salts
Authors: Gérin Michel , Fresco James
Published: May 2006

Two phase acid–base titrations of amines from tributyl to tridodecyl and their salts have been performed for the nitrobenzene–water system. Hydrolysis constants were determined and from these anion-exchange constants were calculated. For these series of salts values of hydrolysis and anion-exchange constants were independent of the amine and strongly influenced by the nature of the anions.
A novel type rearrangement in cyclic β-dicarbonyl compounds in strong acid media
Authors: Saito Kimitoshi , Yuki Hidetaka , Ohyama Toshiyuki , Nakane Ryohei , Nagumo Katsuyuki , Sato Tadashi
Published: May 2006

5,5-Dimethylcyclohexane-1,3-dione and its derivatives were shown to isomerize to give 5,6-dihydropyran-4-ones on irradiation in FSO3H or 98% H2SO4. The 2,2-dimethyl derivative, lacking hydrogen on C2, failed to give any products under the same conditions. A similar type of isomerization was also observed with thiolane-2,4-dione and its derivatives, while no photoisomerization was observed with their nitrogen or oxygen analogs. A possible reaction mechanism is proposed.
Gas phase photochemical decomposition of 1-bromopropane
Authors: Bayliss Stuart G. , Failes Robert L. , Shapiro Jacob S.
Published: May 2006

The gas phase photochemical decomposition of 1-bromopropane (lbp) was studied over the temperature range 374–483 K and the pressure range10–95 kPa. Within these ranges the overall kinetics are expressed by:[Formula: see text]where I0 is the incident light intensity. The principal propagation step involves the abstraction of the secondary hydrogen by a bromine atom leading to two major products: propene and hydrogen bromide. Termination involving allyl radical is postulated, a feature that sets this photolysis apart from those of ethyl and neopentyl bromides. The overall activation energy is 33.8 ± 0.8 kJ mol−1 and it leads to Arrhenius parameters for the propagation step [3] of Ea = 29.7 kJ mol−1 and log10A = 9.1 (A in dm3 mol−1 s−1).[Formula: see text]
A preliminary treatment of solute and solvent interactions in the diffuse part of the electric double layer
Authors: Outhwaite C. W.
Published: May 2006

The electrolyte in the diffuse layer is modelled by a system of charged hard spheres and dipolar hard spheres. Poisson's equation and integral equations for the mean electrostatic potential are derived and the implications worked out for a mean field approximation.
Solvent accessibility and hydrophobicity in the adsorption of alkylammonium cations at air/water and Hg/water interfaces. Part II. Behavior at the Hg/water interface in relation to hydrophobic interactions
Authors: Conway B. E. , Rocheleau F.
Published: May 2006

The adsorption behavior of a series of n-propylammonium ions in which the N+ center has varying accessibility to the solvent, and hence the ions exhibit varying hydrophobicity, is examined at the Hg/H2O interface at various electrode potentials. With the most hydrophobic ion, (n-Pr)4N+, attractive interactions arise in the interphase. An attempt is made to explain this behavior in terms of Gurney hydration co-sphere sharing effects which are significant in 3-dimensional aqueous solutions of R4N+ salts.The surface pressure behavior and Esin and Markov effects are also evaluated.Comparisons are made with the adsorption and surface potential results reported in Part I for the air/water interface.
The cybrodins, a new class of sesquiterpenes
Authors: Ayer William A. , McCaskill Robert H.
Published: May 2006

The isolation and structure determination of the "cybrodins", a new group of sesquiterpenoids produced by a new strain of the bird's nest fungus Cyathus bulleri, is reported. Cybrodol (3), isocybrodol (4), cybrodal (5), trisnorcybrodolide (6), and cybrodic acid (7) may be classified as seco-illudalane sesquiterpenes. The evidence leading to the structural assignments is presented, along with chemical correlations among the cybrodins. The possible mode of biogenesis is discussed. Pterosin-C (13), a known norsesquiterpene, and 3-methyllumichrome (17) were also isolated. Small quantities of a new sesquiterpenoid, broderol, believed to possess structure 21, were obtained on two occasions.
Ionic strength effect on liquid chromatographic retention of benzenesulfonates on nonpolar adsorbents
Authors: Rotsch Terry D. , Cahill Jr W. R. , Pietrzyk Donald J. , Cantwell Frederick F.
Published: May 2006

Chromatographic retention of substituted benzenesulfonate ions is studied on two nonpolar styrene–divinylbenzene adsorbents as a function of mobile phase ionic strength. On both Amberlite XAD-2 and Hamilton PRP-1, a plot of reciprocal of the capacity factor for each benzenesulfonate versus reciprocal of the square root of ionic strength is linear as predicted by Stern–Gouy–Chapman electrical double layer theory. Chromatographic resolution is improved by using an electrolyte-containing mobile phase.
ipso Nitration. XXIII. Reactions of cyclohexadiene adducts from nitration of 4-ethyltoluene in acetic anhydride
Authors: Fischer Alfred , Henderson George N.
Published: May 2006

The diastereoisomers of 4-ethyl-1-methyl-4-nitrocyclohexa-2,5-dienyl acetate (1) and 1-ethyl-4-methyl-4-nitrocyclohexa-2,5-dienyl acetate (2) are stereospecifically reduced to the corresponding nitrocyclohexadienols with aluminum hydride. Each dienol is stereospecifically methylated to the corresponding methyl ether with methyl iodide, silver oxide, and potassium hydroxide. Acid-catalysed solvolysis of the acetates 1 and 2 results in the substitution of the acetate moiety by other nucleophiles and these reactions are not stereospecific. The products of rearomatization of dienyl acetates, dienols, and dienyl methyl ethers depend on the acidity and ionizing power of the solvents and are readily explained in terms of reactions involving a nitrocyclohexadienyl cation or acetoxy- (hydroxy-, methoxy-)cyclohexadienyl cation as key intermediates. In the 4-acetoxy-4-alkylcyclohexadienyl cation 1,2-migration of the acetoxyl group is more rapid than alkyl migration, but 1,2-alkyl migration is faster than migration of the hydroxyl or methoxyl groups in the corresponding cations. 1-Ethyl-4-methoxy-4-methylcyclohexa-2,5-dien-1-ol and 4-ethyl-3-nitrotoluene are significant minor products in the solvolysis of 1-ethyl-4-methyl-4-nitrocyclohexa-2,5-dien-1-ol in aqueous methanol. Nitration of p-ethyltoluene in the presence of sulfuric acid or in trifluoroacetic anhydride gives a mixture of 4-ethyl-2-nitro- and 4-ethyl-3-nitrotoluene in a 2:1 ratio.
Studies related to biological detoxification of kraft pulp mill effluent. I. The biodegradation of dehydroabietic acid with Mortierella isabellina
Authors: Kutney James P. , Singh Mahatam , Hewitt Gary , Salisbury Phillip J. , Worth Brian R. , Servizi James A. , Martens Dennis W. , Gordon Robert W.
Published: May 2006

A study related to biological detoxification of kraft pulp mill effluent is presented. A series of fungal and bacterial preparations were evaluated for their action on dehydroabietic acid (DHA), one of the effluent constituents toxic to fish. Mortierella isabellina was the organism selected for the biodegradation of DHA and subsequent chemical studies established the structures of four novel diterpenoid substances with very much lower acute toxicity to Daphnia pulex.
Multivariate analysis of data for the ionization of weak acids in water – dimethyl sulfoxide solvent mixtures
Authors: Edward John T. , Sjöström Michael , Wold Svante
Published: May 2006

The ionization constants p(sKa) reported for 41 weak acids of varying chemical type in ten water–DMSO solvent mixtures have been analysed by the SIMCA version of principal components analysis. This shows the data to fit a two-component model. The significance of the results for acidity function theory is discussed.
Thermal fragmentation of 3-alkyl-2-phenyloxetanes, 3,3-dimethyl-2-aryloxetanes, and related compounds. A case study of 2-aryl-substituted oxetanes
Authors: Imai Toshiro , Nishida Shinya
Published: May 2006

Thermolyses of epimeric 3-alkyl-2-phenyloxetanes (1c, 1t, 2c, 2t, 3c, and 3t), 3,3-dimethyl-2-aryloxetanes (4, 5, 6, 7, and 8), 3,3,4,4-tetramethyl-2,2-diphenyloxetane (9), and 3,3-dimethyl-2,2-diphenyloxetane (10) were studied in degassed N,N,N′,N′-tetramethylethylenediamine at 270–350 °C. Although the fragmentation of 9 and 10 can be understandable on the basis of a diradical mechanism, there were several observations, in the reaction of certain other oxetanes, which could hardly be explained simply in terms of such a mechanism. Namely, (1) less strained 1t reacted faster than more strained 1c; (2) a major mode of the fragmentation for 1c, 2c, and 3c was "B" (forming an alkene and benzaldehyde), whereas that for 1t, 2t, and 3t was "A" (forming an alkenylbenzene and formaldehyde); (3) the apparent energy of activation for the "B" process seemed to be larger than that for the "A"; (4) a dramatic change of the major fragmentation mode from "B" to "A" was brought about by a substituent on the phenyl group, as was observed in 4–8. These results may be explained reasonably by assuming that the fragmentation proceeds, at least, in dual reaction courses. In competition with an anticipated diradical pathway, there will be another process, which is energetically little more favorable than the diradical fragmentation, rather specific to the "A" mode of fragmentation, and important particularly in the reaction of the trans isomers. Probable candidates for the second process are discussed.
Bis(triethylammonium) hexachlorostannate (IV): crystal structure and hydrogen bonding
Authors: Knop Osvald , Cameron T. Stanley , James Margaret Ann , Falk Michael
Published: May 2006

The crystal structure of (Et3NH)2SnCl6 at room temperature consists of a monoclinically distorted antifluorite packing of Et3NH+ and SnCl62− ions. Each anion has two cations centrosymmetrically associated with it through bifurcated hydrogen bonds to four of the Cl atoms, leaving two of the six chlorines unengaged. The bifurcation is nearly symmetric and the [Formula: see text] group is nearly planar. Infrared spectra of undeuterated and partially deuterated polycrystalline (Et3NH)2SnCl6 show that the NH stretching vibration is essentially uncoupled while the corresponding ND vibration undergoes a complex Fermi resonance resulting in a multiplet in the spectrum of even weakly deuterated material. The hydrogen bonding in (Et3NH)2SnCl6 is stronger than in the corresponding ammonium compound. A negative temperature coefficient of the NH and ND stretching frequencies is consistent with the bifurcation of the hydrogen bond. If a low-temperature transition exists, it was not evident in the NH and ND stretching absorptions.
The crystal structure and vibrational spectra of cis-dichlorobis(cyclopropylamine)-platinum(II), PtCl2(C3H5NH2)2
Authors: Howard-Lock Helen Elaine , Lock Colin James Lyne , Turner Graham , Zvagulis Maruta
Published: May 2006

Crystals of cis-dichlorobis(cyclopropylamine)platinum(II), PtCl2(C3H5NH2)2, are monoclinic, a = 12.770(5), b = 5.838(2), c = 15.113(6) Å, β = 104.46(3)°, Z = 4, space group P21/c. The structure was solved by Patterson and Fourier syntheses and was refined by full-matrix least-squares to R = 0.057, Rw = 0.055 for 1577 reflections with I > 3σ(I). Bond lengths and angles are normal. A vibrational analysis of the compound and its d2-deuterated analogue was performed.
Enzymic aromatization of deuterium labelled testosterone and androst-4-ene-3,17-dione
Authors: Holland Herbert L. , Taylor Gregg J.
Published: May 2006

The preparation and aromatization by human placental microsomes of androst-4-ene-3-ones labelled with deuterium at C-4, C-6α, C-6β, C-16, and C-19 is described. Deuterium nmr spectra are reported for these compounds and for a sample of a 1,2-dideuterated androst-4-ene-3-one; the latter is formed nonstereospecifically by reduction of the C-1(2) double bond of a Δ1,4-diene-3-one. Aromatization by placental microsomes occurs with retention of deuterium at C-4 and C-6, but with some loss from C-16. The aromatization of 19-d1 and 19,19,19-d3 steroids in the presence of 16,16-d2 steroids has been carried out to determine the deuterium isotope effect for the oxidative removal of C-19. The values obtained (kH/kD for 19-d1 = 2.3, kH/kD for 19,19, 19-d3 = 3.2) are a combination of primary and secondary effects, but suggest that oxidation at C-19 is a rate-limiting reaction of the biosynthetic sequence.The fungus Pellicularia filamentosa NRRL 2727, reported to hydroxylate androst-4-ene-3,17-dione at C-19, gave only the products of hydroxylation at C-11α, C-11β, and C-14.