bluuebunny/crossref_metadata_2025 huggingface dataset:
The Structure of Sideritol, a Diterpenoid of the ent-Atisane Class
Authors: Ayer William A. , Ball Jo-Ann H. , Rodríguez Benjamin , Valverde Serafin
Published: May 2006

Sideritol, C20H32O3, diterpenoid isolated from Sideritisangustifolia Lag., has been shown to be ent-13-atisen-1β, 16α, 17-triol (1). Sideritol is the first reported oxygenated diterpenoid of the ent-atisane class which does not contain nitrogen. The transformation of sideritol into ent-17-noratisane (11), previously prepared from atisine, rigorously defines the skeleton and absolute stereochemistry of sideritol.
A Salamander Alkaloid Synthesis
Authors: Benn Michael , Shaw Roger
Published: May 2006

Lithium-ethylamine reduction of 17β-acetoxy-1α-hydroxy-2a-aza-A-homo-5β-androstan-3-one, obtained by a Schmidt reaction on 17β-acetoxy-1α-hydroxy-5β-androstan-3-one, yielded an alkaloid isolated from Cryptobranchusmaximus Stanley and provided access to other salamander alkaloids.
The Effect of Pressure on the Solubility of CaCO3, CaF2, and SrS04 in Water
Authors: Macdonald Robie W. , North Neil A.
Published: May 2006

The effect of pressure on the solubility of CaCO3(calcite), CaF2, and SrSO4 in water was investigated for temperatures between 0 and 35 °C for pressures up to 1000 atm. It was found that for SrSO4 at 0 °C, and at 22 °C above 500 atm, and CaCO3 the high pressure solubility products were appreciably lower than those expected from calculations based on the anhydrous salts. It is postulated that this effect may be due to the formation of a bulk or surface hydrate. Consequently, care must be taken in assigning the solid phase when predicting the pressure dependence of the solubility of a sparingly soluble salt.
Oxydation du cyclohexène par le nitrate cérique d'ammonium
Authors: Briguet Claude , Freppel Christian , Richer Jean-Claude , Zador Miklos
Published: May 2006

The oxidation of cyclohexene by ceric ammonium nitrate has been studied. In anhydrous DMSO the reaction leads to cyclohexene-3-nitrate, while in acetonitrile N-(cyclohexene-2-yl) acetamide is formed. Hydroxylated products are formed in the presence of water. The results obtained are explained in terms of the formation of an intermediate arising from the addition of the radical NO3• to the olefinic double bond. [Journal translation]
Degenerate Rearrangements in a Cyclohexenyl Cation. Independent Ring Carbon Interchange and Hydrogen Interchange Processes
Authors: Cone Richard , Haseltine Rollin P. , Kazmaier Peter , Sorensen Ted S.
Published: May 2006

In a 1,2,4-trialkyl-substituted cyclohexenyl cation, two very facile degenerate rearrangements occur. One is simply a scrambling of a proton (C-3) on the allyl center with the C-4 proton. The more interesting process is one involving the specific interchange of the C-1 and -4 carbons and attached alkyl groups. Accurate rates have been measured for both these processes using specific deuterium labelling and the n.m.r. spin saturation technique, in order to probe the mechanism of the rearrangements.
New Synthesis of Nitroxyl Radicals of the Piperidine and Tetrahydropyridine Series
Authors: Wong Lawrence T. L. , Schwenk Robert , Hsia J. Carleton
Published: May 2006

1-Oxyl-2,2,6,6-tetramethyl-4-piperidone cyanohydrin (5) was prepared by addition of HCN to 1-oxyl-2,2,6,6-tetramethyl-4-piperidone (4). The cyanohydrin was used to synthesize 1-oxyl-4-carboxy-2,2,6,6-tetramethylpiperidine (2) and 1-oxyl-4-carboxy-2,2,6,6-tetramethyl-1,2,5,6-tetrahydropyridine (3) which are useful nitroxyl radicals for spin labeling studies.
Electronic Raman Spectroscopy and Magnetic Susceptibilities
Authors: Koningstein J. A. , Kane-Maguire C. J.
Published: May 2006

Data from electronic Raman spectroscopy are employed to calculate temperature dependent magnetic susceptibilities for terbium aluminum garnet, terbium gallium garnet, europium gallium garnet, thulium aluminum garnet, and thulium gallium garnet. An electronic Raman spectrum of terbium gallium garnet is reported, as are newly observed electronic levels in thulium gallium garnet.
Structure Cristalline de TIVO3
Authors: Ganne Marcel , Piffard Yves , Tournoux Michel
Published: May 2006

Thallium metavanadate (TIVO3) crystallizes in an orthorhombic lattice (space group Pbcm) with parameters a = 5.16, b = 11.22, c = 5.73 Å with Z = 4. The structure was determined using 255 independent reflections measured with an automatic diffractometer.Vanadium has a tetrahedral coordination in this structure. The tetrahedra are joined by having two oxygens in common to form chains (VO3)nn− parallel to the c axis.TIVO3 is established to be isomorphous to the metavanadates MVO3 (M = K, NH4, Rb, Cs). Thallium has a coordination number of ten analogous to that of the alkali metals. The study demonstrates that the 6s2 doublet of thallium is sterochemically inactive in TIVO3. [Journal translation]
Arrhenius Parameter for Some Gas-phase Cycloaddition Reactions of Singlet Molecular Oxygen
Authors: Ashford R. D. , Ogryzlo E. A.
Published: May 2006

Rate constants have been determined for several reactions of O2(1Δg) in the gas phase, at temperatures between 300 and 550 °K. The following values were obtained when the data was fitted to the Arrhenius equation:[Formula: see text]A charge-transfer interaction in the transition-state is invoked to account for the data available for such reactions.
The Reaction of Propiolic Acid Esters with Tertiary Amines. Formation of Betaines
Authors: McCulloch A. W. , McInnes A. G.
Published: May 2006

Reaction of propiolate esters, H—C≡C—CO2R, with tertiary alkylamines R′3N in highly aqueous media yields betaines of the type trans R′3N+ •CH=CH•CO2−. The spectral and chemical properties of these derivatives are discussed as well as the mechanism of their formation. The major by-product of reaction is the corresponding trans-3-alkoxyacrylate RO—CH=CH—CO2R.
Radiolysis of Ethane + Sulfur Hexafluoride and Ethylene + Sulfur Hexafluoride Gaseous Systems. Formation of SF5• Radical and its Reactivity
Authors: Gawlowski Janusz , Herman Jan A.
Published: May 2006

Neutralization processes of ions in radiolysis of ethane or ethylene + sulfur hexafluoride systems lead to the formation of the SF5• radical. Compounds of the general formula RSF5 are formed as a result of recombination reactions with hydrocarbon radicals. In the mixture ethane +0.3% sulphur hexafluoride the radiochemical yield of SF5• is [Formula: see text] The presence of ammonia decreases [Formula: see text] to ca. 0.2, suggesting that the neutralization process of NH4+(NH3)n with SF6− ions follows some unknown path. In the present work some reactions of the SF5• radical are studied. Preliminary results indicate that the presence of SF6 influences very little, if at all, the yield of atomic hydrogen.
Apparent Molal Volumes and Heat Capacities of Alkaline Earth Chlorides in Water at 25 °C
Authors: Perron Gérald , Desnoyers Jacques E. , Millero Frank J.
Published: May 2006

The densities and volumetric specific heats of the alkaline earth chlorides have been measured in water at 25 °C in the concentration range 0.01 to 0.4 M with a flow densimeter and a flow microcalorimeter. Apparent molal volumes and heat capacities have been derived.
Chemical Behavior of Charge-transfer Complexes, VI. Catalysis of Acetolysis of 2,4,7-Trinitro-9-fluorenyl p-Toluenesulfonate by Aromatic Hydrocarbon Donors
Authors: Colter Allan K. , McKenna Arthur L. , Kasem M. A.
Published: May 2006

The catalytic effectiveness of eleven aromatic hydrocarbon donors in the acetolysis of 2,4,7-trinitro-9-fluorenyl p-toluenesulfonate (TNF-OTs) has been examined. For nine of these donors, the kinetic data were analyzed to obtain the rate constant, kc, for acetolysis of the 1:1 donor–substrate complex, and the 1:1 donor–substrate association constant, K. Two measures of catalytic effectiveness, log kc and log kcK correlate well with the highest occupied molecular orbital energy of the donor, E(HOMO), calculated by the Hückel molecular orbital (HMO) method. The success of these correlations is considered to mean that the transition state for acetolysis resembles a π-complex. A model based on Mulliken's charge-transfer theory in its simplest form leads to an estimate of 0.11 of an electron transferred from the donor to the acceptor substrate in the complexed transition state.
Further Studies on the Homogeneous Hydrogenation of Olefins Catalyzed by a Cyclic Phosphine Complex of Rhodium(I) Hydride
Authors: Holah David G. , Hoodless Ian M. , Hughes Alan N. , Hui Benjamin C. , Martin Douglas
Published: May 2006

The use of RhH(DBP)3 as a very active homogeneous hydrogenation catalyst is described and the equilibrium constant for its dissociation to the catalytically active RhH(DBP)2 evaluated.
The Kinetics of the Insertion Reaction of Tin(II) Chloride with Hexacarbonylbis(triphenylphosphite)dicobalt
Authors: Barrett Peter Fowler
Published: May 2006

The kinetics of the thermal insertion reaction of SnCl2 with the metal–metal bonded complex [P(OC6H5)3Co(CO)3]2 have been studied by following the change in the visible spectrum in THF over the temperature range 35.0 to 55.0 °C. The activation enthalpy and entropy for the reaction are 24.7 ± 0.4 kcal/mol and 2.4 ± 1.3 cal mol−l deg−1 respectively. The data are consistent with a two-stage mechanism identical to that proposed for the corresponding reaction with [P(n-C4H9)3Co(CO)3]2 and from a comparison of the two reactions it is concluded that the cobalt–cobalt bond is slightly weakened when tributylphosphine is replaced by the better π-electron acceptor triphenylphosphite. The insertion products [LCo(CO)3]2SnCl2 are shown to undergo further reaction with [LCo(CO)3]2 to form [LCo(CO)3]3SnCl (L = CO, P(n-C4H9)3, P(OC6H5)3).
13C Chemical Shifts of Methylquinolizidines and Correlations with the Chemical Shifts of Methyl Substituted trans-Decalins
Authors: LaLonde Robert T. , Donvito Thomas N.
Published: May 2006

13C chemical shifts are reported for quinolizidine and eight methylquinolizidines. Assignments of methylquinolizidine resonances are made with the assistance of the previously made assignments of quinolizidine, the methyl substituted trans-decalins and the methyl parameters of Grant. A more careful comparison of the quinolizidines with the trans-decalins is made through correlations with experimental data for four decalins and calculated data for six decalins.
The Chlorine Atom Sensitized Oxidation and the Ozonolysis of C2Cl4
Authors: Mathias Eckart , Sanhueza Eugenio , Hisatsune I. C. , Heicklen Julian
Published: May 2006

The chlorine atom initiated oxidation of C2Cl4 was studied both in the absence and presence of O3 at 24 and 32 °C. In the absence of O3, the products are CCl3CCl(O) and CCl2O, and they are produced in a long-chain process in a ratio of 2.5 at 24 °C and 3.0 at 32 °C. The product producing step involves the decay of C2Cl5O radicals[Formula: see text]The ratio k6a/k6b is 5.0 at 24 °C and 6.0 at 32 °C since CCl3 reacts with O2 to produce another CCl2O molecule. In the presence of O3 the ratio Φ{CCl3CCl(O)}/Φ{CCl2O} drops, [Formula: see text] is produced, and the chain length is reduced. The change in Φ{CCl3CCl(O)}/Φ{CCl2O} is a function of [O3]/[O2] and is attributed to the additional reactions[Formula: see text]The epoxide yield is a function of [C2Cl4]/[O3] and is attributed to the reaction of ClO with C2Cl4. The ClO is produced by the reaction of Cl• with O3[Formula: see text]which competes with[Formula: see text]The ratio k2/kl0 = 6.7. The reduction in yield as O3 is added results from the terminating reaction[Formula: see text]The ClO2 reacts further with O3 to produce Cl2O7.The reaction of O3 with C2Cl4 at 24 °C also produces mainly CCl3CCl(O) and CCl2O with [Formula: see text] as a minor product. Other minor products detected after extended conversions included Cl2, CO, and CO2. However c-C3Cl6 was not found. The ratio [CCl3CCl(O)]/[CCl2O] is < 1. Moreover, the addition of O2 retarded the reaction, indicating a long chain mechanism in which both free radicals (species with an odd number of electrons) and CCl2 were absent. A diradical chain mechanism is presented which explains the main features. The chain step is the addition of CCl2O2 to C2Cl4[Formula: see text]The adduct then reacts with O3 in a chain regenerating step or with O2 in a chain terminating step.
Gas–Solid Exchange Reaction: Zinc Vapor and Polycrystalline Zinc Orthosilicate
Authors: Secco Etalo A. , Dhar Hari Pada , Su Chien-Huo
Published: May 2006

The exchange kinetics of zinc vapor with polycrystalline zinc orthosilicate have been studied in a static system in the temperature range 760–1000 °C.The kinetic data reveal two rate laws. The initial rate is assigned to a transport step, i.e. mobility of zinc with D = 10−8 exp (−34 ± 5 kcal/RT ) cm2 s−1. The rate at high annealing times is a composite of the initial rate and a particle growth process, e.g. sintering.
Coordination Compounds of Indium. Part XXVI. Ligand Exchange Studies with Trifluoromethyl-β-diketonato(dimethyl)indium(III) compounds
Authors: Chung H. L. , Tuck D. G.
Published: May 2006

The ligand exchange between Me2InL and HL (L = CF3.CO.CH.CO.R− anion; R = methyl or t-butyl) has been studied by 19F n.m.r. spectroscopy, using benzene and di-isobutylketone as solvents. The exchange is first order in both Me2InL and HL. Activation free energies were derived from measurements of the coalescence temperature. The results are compared with those of earlier studies. The rate-controlling process in the exchange is identified as the rotation of one monodentate diketonate ligand about a partial double bond prior to intramolecular proton transfer to a second monodentate ligand.
Adsorption and Desorption of Hydrogen, Carbon Monoxide, and Their Reaction Products on a Catalyst for the Synthesis of Methanol
Authors: Aharoni C. , Starer H.
Published: May 2006

Mixtures of hydrogen and carbon monoxide were adsorbed on a catalyst for the methanol synthesis and desorbed at increasing temperatures. The fraction of CO converted into methane increases when the ratio CO adsorbed to hydrogen adsorbed decreases, and when the temperatures of adsorption and desorption increase. Methanol is obtained in small amounts at high temperature, low pressure, and low CO:H2 ratio. It is assumed that the surface is heterogeneous and that hydrogen and CO form an intermediate adsorbed compound converted into methane or methanol by reaction with adsorbed hydrogen.
Conformations of Sugars: Proton Dihedral Angles from Gauche Coupling Constants
Authors: Forrest T. P.
Published: May 2006

Proton coupling constants have been used in calculating dihedral angles of vicinal gauche protons in variety of pyranose derivatives of glucose, mannose, arabinose, xylose, altrose, and galactose. The calculations involve the use of a formula which was derived from a correlation of the coupling constants of ethane derivatives with the electronegativities of substituents and their orientation relative to the coupled protons.The results indicate that the formula has general applicability and gives more reasonable values than a Karplus equation in which the constants have been adjusted to fit some compounds of the series. The calculated dihedral angles indicate that an equatorial substituent generally causes little distortion of dihedral angles, whereas an axial substituent generally causes the equatorial proton on the same carbon to have a smaller than normal dihedral angle with the adjacent axial proton and a larger than normal dihedral angle with the adjacent equatorial proton.
Kinetics of the Cu(II) – Nitrilotriacetic Acid Reaction
Authors: Maguire James
Published: May 2006

The kinetics of the reaction between Cu(II) and nitrilotriacetic acid (NTA) to form the 1:1 complex have been studied by the stopped-flow technique over the pH range 2–6. The reaction is kinetically first order in both [Cu(II)] and [NTA]total; the rate constant has a minimum value of 1.1 × 105 l mol−1 s−1 in the pH range 3.5–5 and increases with either increasing or decreasing pH. An explanation for the observed kinetic behavior may be that in the case of the monoprotonated species HNTA2− there is a rate-limiting transfer of a proton from nitrogen before complex formation takes place, and that this transfer is facilitated with increasing acidity.
C6F5X Bond Dissociation Energies: Determination from Appearance Potential Measurements and Correlation with Thermochemical Data
Authors: Price Stanley James W. , Sapiano Henry J.
Published: May 2006

Appearance potentials for C6F5+ from C6F5X (X = F, Cl, Br, I) have been determined relative to argon (15.76 eV) by the extrapolated voltage difference method. The respective appearance potential values are 16.86, 15.85, 14.93, and 13.21 eV with an estimated precision of ± 0.05 eV. Combining differences in these values with the kinetic values of D[C6F5—I] = 66.2 kcal mol−1 leads to D[C6F5&([a-z]+);F] = 150.4 ± 2.0 kcal mol−1, D[C6F5&([a-z]+);Cl] = 127.1 &([a-z]+); 2.0 kcal mol−1, and D[C6F&([a-z]+);Br] = 105.9 ± 2.0 kcal mol−1Comparison with D[C6F5—X] (X = F, Cl, I) from thermochemistry (1) indicates that the combined excitation energies, kinetic energies, and chemical shifts for the process C6F5X → C6F5+ + X are constant within experimental error.
The Synthesis and Pyrolytic Rearrangement of Phthalate Esters of Some Tertiary Silanols. An Attempt to Prepare a Silicon Carbon Double Bond Species
Authors: Rutherford K. G. , Seidewand R. J.
Published: May 2006

The synthesis and pyrolysis of the methyl phthalate esters of diphenylmethylsilyl, t-butylsilyl, benzyldiphenylsilyl, and optically active 2-octanol yielded corresponding silyl ethers and phthalic anhydride. In the case of the latter compound, almost complete retention of configuration was observed about the asymmetric carbon atom. A mechanism is proposed for this rearrangement.
Crystal Structures of K2MgCl4 and Cs2MgCl4
Authors: Gibbons Cyril S. , Reinsborough Vincent C. , Whitla W. Alexander
Published: May 2006

Supporting evidence for complex ion formation in MgCl2 alkali chloride melts was sought from a single crystal X-ray analysis of the title compounds. Crystals of K2MgCl4 are tetragonal, a = 4.94, c = 15.58 Å, Z = 2, space group I 4/mmm. The compound is isostructural with K2NiF4, and was determined with MoK α diffractometer data and refined by full-matrix least-squares to R = 0.046 for 180 reflections.Crystals of Cs2MgCl4 are orthorhombic, a = 9.777, b = 7.514, c = 13.234 Å,Z = 4, space group Pnma. The compound is isostructural with β-K2SO4, and was determined with MoKα diffractometer data and refined by full-matrix least-squares to R = 0.074 for 1084 reflections. The K2MgCl4 structure contains an infinite two-dimensional array of MgCl6 octahedra sharing edges. The Cs2MgCl4 structure contains discrete MgCl42− anions which likely continue to exist in the melt close to the melting point.
Base-catalyzed Rearrangement Reactions of 4a-Ammomethyl-1,2,3,4,4a,9-Hexahydrophenanthrenes. Synthesis of D-Normorphinans
Authors: Conway Terry T. , Doyle Terrence W. , Perron Yvon G. , Chapuis Jacques , Belleau Bernard
Published: May 2006

The syntheses of members of the D-normorphinan system, which is unreported prior to this work, are described. Two methods employing 4a-aminomethyl-1,2,3,4,4a,9-hexahydrophenan-threnes (1a-d) as starting materials were developed. These were the base-catalyzed rearrangement of 1 to the 4a-aminomethyl-4a,10a-cis-1,2,3,4,4a,10a-hexahydrophenanthrenes 2 followed by base-catalyzed ring closure of one of these (2b) to N-methyl-D-normorphinan (3) and the intramolecular cyclization of the chloramine derived from 2c to give 10-substituted-N-benzyl-D-normorphinans which were transformed into a number of derivatives.The Eu(fod)3 induced shifts in the n.m.r. spectra of certain of these D-normorphinans are reported and form the basis of a configurational assignment to one of the products obtained on chloramine solvolysis.
13C Nuclear Magnetic Resonance and 14C Tracer Studies on 1,2-Phenyl Shifts in the Reaction of Labeled Triphenylvinyl Bromide with Acetic Acid and Silver Acetate
Authors: Rummens Franz H. A. , Green Robert D. , Cessna Allan J. , Oka Mitsuo , Lee Choi Chuck
Published: May 2006

Reaction of triphenylvinyl bromide, labeled at C-2 with 14C or 13C (1—Br-2-14C or 1—Br-2-l3C), with HOAc–AgOAc gave an isotopically rearranged product, 1—OAc-x-14C or 1—OAc-x-13C. After conversion of the product to 1,2,2-triphenylethanol (2—x-14C or 2—x-13C), 14C assays after degradation to benzophenone, or analyses by FT c.m.r. and by 13C satellites of p.m.r. in the FT or CW mode all gave results that were in reasonable agreement, indicating 6.8 ± 0.9% scrambling of the label from C-2 to C-1. The work shows that while the c.m.r. technique eliminates the need for degradation, the tracer method, with appropriately high specific activities, is capable of giving higher precision.
Etude par spectrométrie infrarouge de la complexation entre les N,N-diméthyl-N′-phénylformamidines et quelques donneurs de proton
Authors: Vaes J. , Foubert F. , Zeegers-Huyskens Th.
Published: May 2006

The stability constants of complexes formed between ethanol and phenols with some N,N-dimethyl-N′-phenylformamidine derivatives are determined by i.r. spectrometry. The application of the Hammett relation shows the existence, in addition to the first degree terms depending on the substitution parameters of the proton donor (∑σa) and the proton acceptor (∑σb), of a crossed term depending on the ∑σa∑σb product. The different parameters are discussed as a function of the acid–base properties of the molecules. The results suggest that the formation of the hydrogen bond takes place on the imino nitrogen atom. The stability constant of the complexes of 2:1 stoichiometry is calculated; in this complex the second molecule of phenol seems to be preferentially bonded to the oxygen atom of the first molecule rather than to the amino nitrogen atom.
Solvent Effects on Solvent Exchange Reactions at Nickel(II) Centers
Authors: Langford Cooper H. , Tong James P. K. , Merbach André
Published: May 2006

Several recent correlations relating kinetics of Ni(II) complex formation and solvent exchange to solvent properties are examined after collection of literature and new experiments on solvent exchange kinetics at Ni(II) when onlythesolvent is varied (entering group, leaving group, and nonlabile ligands held constant). The results indicate solvent exchange is remarkably insensitive to bulk solvent. It is suggested that this implies that the interesting correlations of complex formation rates with solvents introduced by Bennetto and Caldin provide a means to study the solvent dependence of the encounter equilibria between a Ni(II) complex and a ligand L. The linear relationship between enthalpies and entropies of activation for reactions at Ni(II) in different media is attributed to the changes in the ligands bound to the Ni(II) center but not undergoing substitution in the reaction observed.
Fluorinated Alkoxides. Part IX. The Resolution Of Perfluoro(2,3-diphenylbutane-2,3-diol) and its use in preparing Optically Active Complexes Of Ni2+ and Cu2+
Authors: Cripps W. Stafford , Willis Christopher J.
Published: May 2006

Perfluoro(2,3-diphenylbutane-2,3-diol), CF3(C6F5)C(OH)C(OH)(C6F5)CF3, prepared by the reductive dimerization of C6F5COCF3, has been separated into meso- and DL-isomers and the latter resolved via its cinchonidine salt into optical enantiomers. The doubly ionized diol, PDBD2−, acts as a dinegative, chelating, ligand, and neutral complexes of the form (PDBD)-ML2 may be isolated, where L is a neutral nitrogen- or phosphorus-containing ligand and M = Ni2+ or Cu2+. Use of the resolved diol enables optically active metal complexes to be prepared, and from their o.r.d./c.d. spectra we assign an absolute configuration to the diol. The partially fluorinated diols CF3(C6H5)C(OH)C(OH)(C6H5)CF3 and CH3(C6F5)C(OH)C(OH)(C6F5)CH3 have also been prepared from the appropriate ketones. The former, which appears to be exclusively the meso-isomer, has more limited chelating ability than the fully fluorinated analog, while the latter shows no ligand properties; these differences are ascribed to the reduced acidity resulting from the lower degree of fluorination.Nuclear magnetic resonance studies suggest hindered rotation of the C6F5 groups through steric interaction with CF3 groups in perfluoro(2,3-diphenylbutane-2,3-diol); an alternate explanation involving hydrogen bonding from the hydroxylic proton to aromatic fluorine atoms is considered less likely.
The Structure of (NO)2[Ho(NO3)5], A 10-Coordinate Species
Authors: Toogood Gerald E. , Chieh Chung
Published: May 2006

Nitrosonium pentanitratoholmate(III), (NO)2Ho(NO3)5, was prepared from holmium metal and dinitrogen tetroxide in anhydrous ethyl acetate. Its crystals are monoclinic with a = 8.094, b = 11.979, c = 14.170 Å and β = 104.7°,Z = 4, space group P21/c. The structure was solved by the heavy-atom method and refined by full matrix least-squares methods to an R value of 0.085 for 1514 observed reflections measured on the G.E. XRD-6 diffractometer. The structure consists of one Ho(NO3)52− and two NO+ ions. The holmium is 10-coordinated by five essentially symmetric bidentate nitrate groups which arrange themselves in a trigonal bipyramidal fashion around the metal with a mean Ho—O distance of 2.45 Å. The two NO+ ions per metal occupy slightly different environments and give rise to two i.r. bands at 2250 and 2285 cm−1, attributable to the (N, O+) stretching vibration. The mean N—O distance within these ions is 1.00 Å.
The Copper–Selenium System at Temperatures to 850 K and Pressures To 50 Kbar
Authors: Murray Ritchie MacLaren , Heyding Robert Donald
Published: May 2006

Phase relationships in the copper/selenium system in the composition range 30–70 atomic % selenium have been studied at temperatures from 298 to 850 K and at pressures to 50 kbar. A revised atmospheric pressure phase diagram is given, as well as an outline of the phase diagram at 20 kbar.αCu2Se is monoclinic at 298 K with a = 14.087, b = 20.481, c = 4.145 Å, β = 90° 23′. The α → β (f.c.c.) transformation is complex, and occurs over a 30 K interval centered on 396 K. The overall enthalpy change is 6.4 ± 2 kJ mol−1. The maximum in the DTA signal for this transition decreases slowly with increasing pressure at < 1 K kbar−1. The signal disappears above 42 kbar, presumably due to the formation of a high pressure modification.Variable composition in Cu2−xSe (berzelianite) extends from Cu2.00Se to Cu1.75Se in the range 402–523 K. Cu1.80Se, with a = 5.765 Å at 298 K, is stable throughout the temperature and pressure ranges investigated.Cu3Se2 (umangite) is stable at 298 K to at least 35 kbar. Dimensions of the tetragonal cell at 298 are a = 6.385, c = 4.217 Å. At atmospheric pressure it disproportionates to Cu2−xSe and βCuSe at 386 K with an enthalpy change of 10.0 ± 5 kJ mol−1. The reverse reaction is very slow. Above ca. 5 kbar it disproportionates to Cu2−xSe and CuSe2II at a temperature less than 413 K. The reverse reaction is fast.αCuSe (klockmannite) is hexagonal with a = 3.934, c = 17.217 Å at 298 K. It transforms to βCuSe at 323 K under atmospheric pressure with an enthalpy change of 0.84 ± 5 kJ mol−1. This modification is C end-centered orthorhombic with a = 3.948, b = 6.958, c = 17.239 Å at 324 K. With increasing temperature the orthorhombic a/b ratio increases rapidly until, at 393 K, the transition to γCuSe is complete. This modification is hexagonal with a = 3.984, c = 17.288 Å at 430 K. CuSe is unstable above 5 kbar at 298 K, decomposing to form Cu3Se2 and CuSe2II.Marcasite-type CuSe2, with a = 5.0046, b = 6.1822, c = 3.7397 Å at 298 K, disproportionates to CuSe and Se at 605 K under atmospheric pressure with an enthalpy change of 9.6 ± 4 kJ mol−1. It transforms at less than 5 kbar at 298 K to the cubic pyrite modification CuSe2II, with a = 6.116 Å. CuSe2II melts congruently at 818 K and 20 kbar. The melting point increases with increasing pressure at ca. 3 K kbar−1.
Carbonyl Addition Reactions: Factors Affecting the Hydrate–Hemiacetal and Hemiacetal–Acetal Equilibrium Constants
Authors: Guthrie J. Peter
Published: May 2006

Equilibrium constants for hydrate–hemiacetal interconversion in aqueous solution at 25° have been measured for four fluorinated carbonyl compounds: compound, alcohol, K4 (M−1): CF3CHO, C2H5OH, 2.3; CF3COCH3, CH3OH, 1.0; CF3COPh, CH3OH, 3.5; CF3COCF3, CH3OH, 0.14. These values, combined with values from the literature, permit an examination of substituent effects upon the equilibrium constant for[Formula: see text]The free energy change for this process, corrected for symmetry and steric effects, follows the equation[Formula: see text]Thus electronic effects upon this equilibrium are generally small and in fact are often smaller than steric effects.This analysis permits and justifies the calculation of free energies of formation of [Formula: see text] compounds from the (more generally measurable) free energies of formation of the analogous [Formula: see text] compounds.
The Crystal Structure of Dimedone
Authors: Singh Ishwar , Calvo Crispin
Published: May 2006

Dimedone, C8H12O2, crystallizes with monoclinic symmetry, a = 10.079(7), b = 6.835(3), c = 12.438(4) Å, β = 110.24(5)°, space group P21/n and Z = 4. The structure of this compound was solved by direct methods and refined by full-matrix least-squares techniques using 1205 unique reflections to a final R of 0.047. In the solid state it exists in the enolic form and these molecules pack in the crystal in systems of infinite chains linked together by hydrogen bonds in the y direction. These results are virtually the same as recently reported by Semmingsen.
On the Mechanism of Base-catalyzed Hydrogen Isotope Exchange in Cyclic Ketones
Authors: Banerjee Sujit , Werstiuk Nick H.
Published: May 2006

The kinetics of H → D exchange in norcamphor (1) and of D → H exchange in norcamphor-3,3-d2 (6) have been determined. The rate ratio kexo/kendo drops from 661 in H → D exchange to 72 for D → H exchange. These data imply the presence of a dual mechanism for endo exchange and emphasize the importance of isotope effects in dictating exchange selectivity.
Apparent Molal Volumes and Heat Capacities of some Sulfates and Carbonates in Water at 25 °C
Authors: Perron Gérald , Desnoyers Jacques E. , Millero Frank J.
Published: May 2006

The densities and volumetric specific heats of Na2SO4, K2SO4, MgSO4, Na2CO3, NaHCO3, and NaOH were measured up to an ionic strength of 1 in water at 25 °C with a flow densimeter and a flow microcalorimeter. From these data, the heat capacity for the formation of the ion pair MgSO40was evaluated as 84.9 J K−1 mol−1. There is an anomalous increase in the apparent molal heat capacities of Na2CO3 at low concentration but the apparent molal volumes are normal. This anomaly can be suppressed with NaOH. Attempts to account quantitatively for this behavior by an hydrolysis correction were not successful.
The Crystal Structure of the [Pt(diethylenetriamine)Br]Br Complex
Authors: Melanson Robert , Hubert Joseph , Rochon F. D.
Published: May 2006

The molecular and crystal structure of the [Pt(dien)Br]Br complex (dien = diethylenetriamine) has been studied by X-ray diffraction. The compound belongs to the orthorhombic Pca21 space group and the cell parameters are: a = 14.211, b = 4.940, c = 13.450 Å, and Z = 4. The refinement of the positional and anisotropic thermal parameters, carried out by full matrix least squares calculations, converged to R = 0.039 and Rw = 0.036.The coordination around the platinum atom is planar. The crystal consists of alternate layers of [Pt(dien)Br]+ cations and Br− ions parallel to the ac plane.
Correlation of The Diterpenoids Sideritol and Jativatriol
Authors: Carstenn-Lichterfelde Carlos von , Panizo Fernando M. , Quesada Teresa G. de , Rodríguez Benjamin , Valverde Serafin , Ayer William A. , Ball Jo-Ann H.
Published: May 2006

The diterpenoids jativatriol (1) and sideritol (2) have been correlated by transformation of each into ent-17-noratis-13-en-1,16-dione (9). In the case of jativatriol, a simple procedure is described for transforming the ent-5-beyerene derivative into an ent-13-atisene derivative.
Substituted 5-Allyl-9-oxobenzomorphans. Versatile Intermediates for Investigations in the Field of Analgesics and Narcotic Antagonists. Part 1
Authors: Monkovic Ivo
Published: May 2006

2-Tetralone has been converted to 5-allyl-2-methyl-9-oxo-benzomorphan methobromide (4). Thermal dequaternization of 4 afforded tertiary base 5. Alternatively, 4 was reduced with sodium borohydride to give 7a or reacted with methylmagnesium iodide to give 7b. Dequaternization of these to tertiary bases (8a and 8b) followed by acid-catalyzed cyclization afforded tetrahydrofurano compounds 9a and 9b, respectively. Bromocyclization of 8b afforded bromomethyltetrahydrofurano compound 9c, which was further converted to dimethylamino compound 9d.
A New Method of Preparing Hydrazonyl Halides
Authors: Wolkoff Peder
Published: May 2006

The triphenylphosphine – carbon tetrahalide (Br, Cl) system transforms N′-benzoyl-N-arylhydrazines (1), N,N-dimethyl-, and N-methyl-N-phenyl-N′-benzoylhydrazines (3) into the corresponding hydrazonyl halides 2 and 4.Tribromomethyltriphenylphosphonium bromide (7), formed by reacting triphenylphosphine with carbon tetrabromide, is capable of transforming N′-benzoyl-N-phenylhydrazine (1a) into the corresponding hydrazonyl bromide (2b) in the presence of triphenylphosphine.
Homogeneous Catalysis of Hydrogen Isotope Exchange between D2 and Ethanol by Dichlorotris(triphenylphosphine) Ruthenium(II)
Authors: Strathdee Graeme , Given Russell
Published: May 2006

Rates of D2–ethanol exchange catalyzed by solutions of dichlorotris(triphenylphosphine) ruthenium(II) in 1:1 benzene–ethanol are reported as a function of the concentrations of ruthenium, deuterium, triphenylphosphine, and HCl. The rates were extremely fast, and approached 10−3 mol D2 l−1 s−1 at 333 K with 1.3 mmol/l Ru. Over the temperature range 263 to 303 K, the apparent activation energy was 85 kJ/mol. The kinetics have been interpreted in terms of a mechanism in which activation of D2 by RuCl2L3 is rate-controlling. A comparison is made between the characteristics of this homogeneous catalyst and those of the related RhClL3.
A Convenient Preparation of meso-Tetra(4-sulfonatophenyl)porphyrin
Authors: Busby Claudia A. , Dinello Robert K. , Dolphin David
Published: May 2006

The sulfonation of meso-tetraphenylporphyrin, in concentrated sulfuric acid followed by neutralization and dialysis, provides an efficient and convenient route to meso-tetra(4-sulfonatophenyl)porphyrin.
Juvabione and its Analogs. Juvabione and Δ4′ -Dehydrojuvabione Isolated from the Whole Wood of Abiesbalsamea, have the R,R Stereoconfigurations, not the R,S
Authors: Manville John Fieve
Published: May 2006

The petroleum ether soluble fractions from the whole wood meal of a number of native Abiesbalsamea (L.) Mill. var. balsamea and var. phanerolepis Fern. contain varying amounts of several juvabione analogs. These include the previously reported (+)-juvabione (1a), atlantones (2), and lasiocarpenone (3). This paper describes the first isolation of (+)-Δ4′-dehydrojuva-bione (R,R) (5a) and proves the R,R stereoconfiguration for (+ )-juvabione (1a) isolated from native Abiesbalsamea. These results require that those samples previously isolated from a Slovak fir and which have the R,S stereoconfigurations, be renamed (+ )-epijuvabione (6 ) and (+ )-Δ4′-dehydroepijuvabione (7).
The Ionization of Picric Acid in Ethanol–Sulfolane and t-Butyl Alcohol – Sulfolane Mixtures at 30 °C
Authors: Castagnolo Maurizio , Giglio Angelo De , Dell'atti Angelo , Petrella Giuseppe
Published: May 2006

Dissociation constants at 30 °C of picric acid have been determined by a spectrophotometric method in ethanol–sulfolane and t-butyl alcohol – sulfolane mixtures over the entire solvent composition range. Picric acid behaves as a weak acid in all mixtures. In pure sulfolane, picric acid undergoes simple dissociation for c < 0.08 M (pKHPI = 7.6). At concentrations higher than 0.08 M more complex equilibria have been observed and interpreted assuming Pi(HPi)2− as the principal picrate species in solution. Complex behavior of dependence of association constant on solvent composition was observed; in both solvent mixtures as sociation of picric acid decreases with decrease of dielectric constant. This behavior was discussed in terms of preferential solvation of picric acid by alcohols, the more basic components of the mixtures. A reaction mechanism of four alcohol molecules with one acid molecule accounts for the behavior observed.
Configurational Entropy Change of Sodium Pyrophosphate
Authors: Leung Kiang Y.
Published: May 2006

Based on an analysis of the observed crystal structures of the phases of anhydrous sodium pyrophosphate, a calculation of the configurational entropy change of the system between the ordered ambient-temperature phase and the disordered hexagonal phase above 600 °C has been carried out. The result is 0.2187R cal mol−1 deg−1 where R is the gas constant.
Crystal Structure of the Glaserite Form of BaNaPO4
Authors: Calvo Crispin , Faggiani Romolo
Published: May 2006

Crystals of BaNaPO4 were grown from a Ba3P2O8–Na2B4O7 melt. The crystals are trigonal, space group [Formula: see text]with a = 5.622(4) and c = 7.259(5) Å. The structure, isotypic with that of glaserite, was refined by full-matrix least-squares methods to a final R value of 0.042 using 218 unique reflections. There are three different cation sites. Na and Ba lie at sites of [Formula: see text] symmetry and are coordinated to 6 and 12 oxygen atoms respectively. The Na—O bond lengths are 2.344(7) Å and the two unique Ba—O bond lengths are 2.788(7) and 3.247(9) Å. The remaining cation site has 3m symmetry, a coordination number of 10, and contains equal amounts of Na+ and Ba2+. The bond lengths range from 2.548(12) to 3.017(7) Å. The phosphate group also has 3m symmetry with mean P—O bond lengths of 1.538 Å. The underbonded apical P—O bond length is 1.520 Å.
Syntheses of Some Phosphino- and Phosphinatoazoles
Authors: Fischer Sven , Peterson Louis K. , Nixon John F.
Published: May 2006

not available
The Stability and Conformation of the 1,3,6,8-Tetraazatricyclo[4.4.1.13,8]dodecane System: the Structure of the Condensation Product of 1,2-Diaminocyclohexane and Formaldehyde
Authors: Murray-Rust P. , Riddell F. G.
Published: May 2006

The condensation of d,1-trans-1,2-diaminocyclohexane with formaldehyde gives a pentacyclic molecule based on the 1,3,6,8-tetraazatricyclo[4.4.1.13,8]dodecane nucleus. This was shown to have S4 symmetry by 1H n.m.r. and an X-ray analysis showed crystals to be orthorhombic, Fddd, a = 12.02, b = 19.25, c = 12.90 Å. The symmetry of the compound in the crystal was D2d due to a disordered arrangement and structure analysis was carried out to R = 0.166. When optically active diamine was used as starting material, the analogous reaction did not occur and this was attributed to strain in the tricyclic system. The conformation of the molecule is related to those of similar compounds as found by X-ray analysis.
Metastable Ion Studies. V. The Identification of C2H4O+ · Ion Structures from their Characteristic Kinetic Energy Releases
Authors: Holmes John L. , Terlouw Johan K.
Published: May 2006

Metastable ion peaks for the fragmentation C2H4O+ • → C2H3O+ + H• have been studied in the first field-free region of a double focussing mass spectrometer under conditions of good energy resolution. Three isomeric C2H4O+ • ions were generated[Formula: see text] (b) CH3CHO+, and (c) CH2=CHOH+ • from ethylene oxide, acetaldehyde, and ethyl vinyl ether respectively, each fragment producing a different 1m* peak having a characteristic shape and kinetic energy release. The above ions do not therefore interconvert prior to fragmentation and their characteristic 1m* peaks permit their unequivocal identification, thus providing a powerful method for ion structure determination.In agreement with some recent collisional activation data it was found that the unbranched aldehydes, cyclic alcohols, and 2-haloethanols investigated generated (c) type C2H4O+ • ions. These are also produced by glycidol and α-furfuryl alcohol. Some compounds generated composite 1m* peaks, e.g. 1,3-dioxolane produces (a) and (c) ions, while compounds which produce prominent C2H5O+ ions having the protonated acetaldehyde structure, generate m/e 44 ions of structures (b) and (c). In isopropanol these components were separated by a deuterium labelling experiment. Contrary to earlier proposals, pyruvic acid does not generate (b) type ions but produces predominantly ions of structure (c).
Conformations of Bridged Diphenyls. XI. Crystal Structure of 2-(4′-Carbomethoxy-2′-nitrophenylsulfonyl)-1,3,5-trimethylbenzene
Authors: van der Heijden Simon P. N. , Chandler W. David , Robertson Beverly E.
Published: May 2006

The crystal structure of 2-(4′-carbomethoxy-2′-nitrophenylsulfonyl)-1,3,5-trimethylbenzene, C17H17NO6S, has been determined by X-ray diffraction. The crystals are triclinic, a = 12.907(13), b = 7.577(5), c = 9.1808(9) Å, α = 105.82(3), β = 112.81(5), γ = 93.97(4)°, [Formula: see text] with Z = 2. The integrated intensities of 3792 independent reflections were measured on a four circle diffractometer and 2985 reflections were used in the refinement to give a least-squares residual of 0.046 and a conventional R factor of 0.057.The molecule shows a twist-nitro-proximal conformation. However, the dihedral angles made by the mesityl ring and the nitro-substituted ring with the central C—S—C plane are dissimilar in contrast to the nearly equal angles found for the similarly substituted sulfinyl compound.
Base-catalyzed Degradations of Carbohydrates. VIII. Disaccharide Syntheses
Authors: Aspinall Gerald O. , Krishnamurthy Thinnayam N. , Furda Ivan
Published: May 2006

Acetylated derivatives (3 and 10) of the disaccharides 6-O-β-D-glucopyranosyl-3-O-mesyl-D-glucose and 3-deoxy-6-O-β-D-glucopyranosyl-D-ribo-hexose have been synthesized. The parent disaccharides have been degraded to give 2-deoxy-5-O-β-D-glucopyranosyl-D-erythro-pentose (4) which has been characterized as the methylated disaccharide alditol.
The Stereochemical Basis of Anticonvulsant Drug Action. V. The Crystal and Molecular Structure of Sulthiame
Authors: Camerman Arthur , Camerman Norman
Published: May 2006

The crystal and molecular structure of sulthiame, (N-[4′-sulfamylphenyl]-l,4-butansultam), one of a series of carbonic anhydrase inhibitors that have gained wide use as antiepileptic agents, has been determined in order to compare the stereochemistry of this compound to that of other antiepileptics. Crystals of sulthiame are orthorhombic, space group Pca21; with cell dimensions a = 8.267, b = 17.750, c = 8.651 Å. The structure was determined by Patterson and Fourier methods and refined to a final R value of 0.039.Sulthiame molecular conformation differs markedly from that of diphenylhydantoin and other anticonvulsant drugs, suggesting a different mechanism of action for this compound. If the sulfonamide group is removed from sulthiame, however, the resulting molecule, although no longer a carbonic anhydrase inhibitor, does retain weak antiepileptic activity and does bear a weak conformational resemblance to the other noncarbonic anhydrase inhibitor anticonvulsant drugs.
Effect of the N-Phenyl Substituent on the Pyrolyses of 1-Phenyl-2-benzothiazolinone and 1-Phenyl-2-benzothiazolinethione
Authors: Lin Denis C. K. , Thomson Michael L. , Dejongh Don C.
Published: May 2006

Results from the pyrolyses of 1-phenyl-2-benzothiazolinone (7) and 1-phenyl-2-benzothiazolinethione (8) are reported and compared with those obtained previously from the corresponding compounds without the N-phenyl group. The mass spectra of 7 and 8 are reported, also. The major fragmentation in the mass spectrum of 7 is the loss of CO, followed by loss of S or H. Pyrolysis of 7 at 750° in a stream of nitrogen gives phenothiazine (9, 31%) and carbazole (10, 28%), by loss of CO and of CO and S, respectively. Pyrolysis of 9 yields 10. The major fragmentation in the mass spectrum of 8 is the loss of H. Pyrolysis of 8 at 750° produces 2-(phenylthio)benzothiazole (11, 87%), which is an isomer of 8, resulting from phenyl migration, and 2-phenylbenzothiazole (12, 3%). Pyrolysis of 11 gives 12.
An Electron Spin Resonance Study of Some Reactions of Pentafluorosulfuranyl (SF5)
Authors: Tait John Charles , Howard James Anthony
Published: May 2006

A kinetic electron spin resonance study of the self-reaction of SF5 and a spectroscopic and kinetic e.s.r. study of the reaction of SF5 with 1,1-di-t-butylethylene are reported. This radical undergoes self-reaction by a second-order process and the rate constants are given by the Arrhenius equation log 2k1(M−1 s−1) = (10.3 ± 0.5) − (1.7 ± 0.5)/θ where θ = 2.303RT kcal mol−1. It adds to 1,1-di-t-butylethylene to give (t-Bu)2CCH2SF5 which decomposes by a first-order process with rate constants that obey the expression log k2(s−1) = (13 ± 0.4) − (10 ± 0.2)/θ. Both these rate constants are pertinent to kinetic studies of the photoinduced addition of SF5C1 to olefins.
Charge Distributions and Chemical Effects. IX. On the Charge Dependence of C-13 Chemical Shifts in Alkylcyclohexanes and Cyclopropane
Authors: Roberge Réal , Fliszár Sándor
Published: May 2006

The analysis of ab initio charge distributions in cyclohexane and selected methylcyclohexanes indicates that no effect other than that described by the relationship δC = −237.1 qC + 242.64 between C-13 chemical shifts and C net charges (as determined for the alkanes) contributes to any significant extent to the shielding of the carbon atoms. This is no longer true for cyclopropane.
Emission from Electronically Excited C2
Authors: Arnold S. J. , Kimbell G. H. , Snelling D. R.
Published: May 2006

Chemiluminescence attributable to the Swan, Phillips, and Ballik–Ramsay bands of C2 was observed when halomethanes of the form CH2−nX2+n (X = Cl, Br, I) were introduced into a stream of hydrogen atoms. The relative population of the ν′ = 0 levels of the A3Πg, b1Πu and A′ 3∑g− states are 10:400:1000 with the total rate of formation into all three states being approximately equal. The principal step for the formation of C2* is believed to be[Formula: see text]
Metal Halide Ammines. III. Thermal Analyses and Calorimetry of Fluorosilicate Ammines and Hydrates of Bivalent Metals. Infrared Spectra of the Ammines
Authors: Patil Kashinath C. , Secco Etalo A.
Published: May 2006

Bivalent metal fluorosilicate ammines have been prepared. The thermal analyses of the dodecammines reveal the decomposition to occur via the pentammine and/or tetrammine. The final ammonia loss is concomitant with fluorosilicate decomposition. Calorimetric data are given for the decomposition reactions. Some fluorosilicate hydrates are included for comparison purposes.The infrared spectral data of the ammines are presented with their assignments.
Paniculatine. A New Alkaloid from L. paniculatum Desvaux
Authors: Castillo M. , Morales G. , Loyola L. A. , Singh I. , Calvo C. , Holland H. L. , MacLean D. B.
Published: May 2006

The structure of paniculatine, an alkaloid of L. paniculatum, has been elucidated. It has a skeletal structure different from other alkaloids of the Lycopodium family.
Cyclization of Some 2,3,5,6-Tetrafluorophenylhydrazine Derivatives. Use of Nuclear Overhauser Effect Measurements in Structural Assignment
Authors: Elliott Arthur J. , Gibson Martin S.
Published: May 2006

Treatment of N-(2,3,5,6-tetrafluorophenyl)-N′-thiobenzoylhydrazine and of N-benzoyl-N′-(2,3,5,6-tetrafluorophenyl)hydrazine with acetic anhydride and triethylamine proceed without rearrangement to give 4-acetyl-2-phenyl-5,6,8-trifluoro-4H-1,3,4-benzthiadiazine and -benzoxadiazine, respectively. Structures follow from 19F n.m.r. and n.O.e. data.
Chlorine-water Oxidation of Some α-Methylsulfonyl Sulfides
Authors: Hardstaff W. R. , Langler R. F. , Leahy J. , Newman M. J.
Published: May 2006

An examination of the chlorination of phenylmethy), diphenylmethyl, and triphenylmethyl methylsulfonyl sulfides (1, 2, and 3) in aqueous acetic acid has provided indirect evidence for Pummerer rearrangement during the chlorination of an α-methylsulfonyl sulfinyl chloride. The results are discussed from both mechanistic and synthetic standpoints.