bluuebunny/crossref_metadata_2025 huggingface dataset:
The Static Dielectric Constants of the Liquified Fluoromethanes
Authors: Tremaine Peter , Robinson Maurice G.
Published: May 2006

The static dielectric constants of CF4, CHF3, CH2F2, and CH3F have been measured at temperatures ranging from their melting points to their normal boiling points. The molar polarization of CF4 agrees with that of the gas phase to within experimental error. The deviation of the dielectric constants of the polar fluoromethanes from the values predicted by the Onsager equation cannot be fully due to their non-spherical shape.It is postulated that although a significant parallel dipole correlation may be present in each fluoromethane, the polarization resulting from the liquid lattice vibrations, may account for much, or all, of the effect in CH3F and CH2F2.
Flash Photolysis Studies of Solute Triplets: an Anomalous Heavy Atom Effect of Xenon
Authors: Head David Alan , Singh Ajit , Cook Margaret Grace , Quinn Michael John
Published: May 2006

Flash photolysis studies show that in solutions of naphthalene in methylcyclohexane the apparent yield of the naphthalene triplet is enhanced ~6% by added krypton and ~50% by added xenon. The effect of xenon on the decay rate of the naphthalene triplet is anomalous; the decay rate decreases instead of increasing. This is attributed to complex formation between singlet excited naphthalene and xenon. We have also investigated the heavy atom effect in solutions of naphthalene in other solvents and in solutions of other solutes. It is anomalous in some of these solutions but to a lesser extent.
Mechanistic Studies of Isomerization Reactions of Tetragonal Planar Tertiary Phosphine Complexes of Palladium(II)
Authors: Cooper David G. , Powell John
Published: May 2006

The complexes [PdCl2(Me2RP)2] (R = o-tolyl; α-napthyl) may be isolated in both cis and trans forms. In CHCl3 solution cis-trans isomerization processes for these complexes are slow and this is ascribed to steric hindrance by the bulky R groups. The cis-trans isomerization is catalyzed by a variety of added ligands L. These isomerization processes have been extensively studied for the complexes cis-and trans-[PdCl2(Me2o-tolylP)2] in CHCl3 solution. The results of variable temperature n.m.r. and u.v. kinetic studies are fully consistent with a consecutive displacement mechanism with an ionic species of the type [PdCl(Me2o-tolylP)2L]+Cl− as an intermediate. The kinetic characteristics are determined by the nature and relative stability of this ionic intermediate. For L = Me2o-tolylP the rate of isomerization is zero order in complex and second order in added phosphine concentration. (At 38° kcis→trans = 6.2 × 103 l mol−1 s−1, ktrans→cis = 6.3 × 103 l mol−1 s−1) For L = PPh3 the rate of isomerization is considerably slower and first order in both complex and added PPh3 concentrations (kcis→trans6.3 = × 10 l mol−1 s−1, ktrans→cis = 6.7 × 10 l mol−1 s−1). Isomerization is also effected in neat methanol and the rate is first order in complex concentration. N.m.r. studies of mixtures of trans-[PdI2(Me2o-tolylP)2] and cis-[PdCl2(Me2o-tolylP)2] in CHCl3 solution show halogen exchange to occur more rapidly than isomerization. However a cis-diiodo complex is not observed and instead isomerization to the trans-diiodo complex is observed to occur.
Thallium and Tin Electrode Potentials in Fused LiCl–KCl Eutectic
Authors: Shafir Joseph M. , Plambeck James A.
Published: May 2006

Electrode potentials of thallium and tin couples were measured in dilute solutions of the ionic species in fused LiCl–KCl eutectic, at 450 °C. Standard molar electrode potentials of the Tl(III)/Tl(I) and Sn(IV)/Sn(II) couples are +0.155 and −0.310 V against a standard molar platinum reference electrode (s.m.p.e.). The standard potentials of the Tl(III)/Tl(0) and Sn(IV)/Sn(0) couples were calculated to be −0.385 and −0.964 V, respectively, vs. the s.m.p.e.
The Vibrational Analysis of Cyclopentanone
Authors: Kartha V. B. , Mantsch H. H. , Jones R. N.
Published: May 2006

The infrared and Raman spectra of cyclopentanone, ααα′α′-d4-cyclopentanone, βββ′β′-d4-cyclopentanone and d8-cyclopentanone have been measured and a normal co-ordinate analysis performed based on a twisted C2 conformation. The 36 normal vibrations were computed using a selective valence force field comprising 16 diagonal and 16 off-diagonal force constants. The 4 isotopic species provided 144 frequencies to refine 15 diagonal force constants. The initial values of the constants were transferred from a force field for cyclohexanone computed in this laboratory. The infrared and Raman spectra were analyzed in terms of the potential energy distribution coefficients categorized as group frequencies, zone frequencies, and delocalized frequencies.
The Synthesis of Nitro and Dimeric Nitroso Sugars by Peracid Oxidation of Amino Sugars
Authors: Baer Hans H. , Chiu Shuet-Hing Lee
Published: May 2006

A number of methyl 3-amino-3-deoxyaldopyranosides were oxidized with m-chloroperbenzoic acid. The reaction, which had been previously applied to steroidal amines (6), has provided a new route to nitro sugars and at the same time furnished hitherto unknown nitroso sugar derivatives, namely, dimeric methyl 3-deoxy-3-nitrosoaldopyranosides. Oxidation of a model compound, trans-2-aminocyclohexanol, likewise gave the corresponding nitro and dimeric nitroso alcohols. The combined yields of oxidation products ranged from 40 to 95%.
Electric Dipole Moments and Conformations of ortho-, meta-, and para-Fluoroacetophenones and of ortho-, meta-, and para-Trifluoromethylacetophenones
Authors: Bock Ernst , Wasylishen Robert , Gaboury Bernard E. , Tomchuk Edward
Published: May 2006

The dipole moments of ortho-, meta-, and para-fluoroacetophenone and of ortho-, meta-, and para-trifluoromethylacetophenone were determined in dilute benzene and carbon tetrachloride solutions at 25 °C. In addition the dipole moments and the total energies of the above molecules and of acetophenone, fluorobenzene, and trifluoromethylbenzene were computed for different molecular conformations by the INDO molecular orbital approximation. In some cases there is quantitative agreement between the experimental dipole moments and the INDO computed dipole moments. The most probable conformation for different fluoroacetophenone and trifluoromethylacetophenone molecules is suggested.
Synthesis of Tritium Labelled [8-Arginine]-vasopressin
Authors: Holton H. Hutch , Branda Luis A. , Ferrier Barbara M.
Published: May 2006

Ring tritiated phenylalanine has been incorporated into [8-arginine]-vasopressin synthesized by the solid phase method. The peptide produced has levels of biological activities in agreement with those of the highly purified natural hormone.
Quaternary Nitrogen Heterocycles. II. Kinetics of Reversible Pseudobase Formation from N-Methyl Heterocyclic Cations
Authors: Bunting John W. , Meathrel William G.
Published: May 2006

The kinetics of the formation and decomposition of the pseudobases from the 2-methyl-4-nitroisoquinolinium, 10-methylacridinium, and 10-methyl-9-phenylacridinium ions have been studied. The pH–rate profiles of these reactions indicate that for each of these ions, pseudobase formation may kinetically involve either attack of a water molecule or of hydroxide ion on the heterocyclic cation depending upon the pH of the reaction. Pseudobase decomposition to the cation may occur through either the neutral or protonated pseudobase species or their kinetic equivalents. The temperature dependences of the equilibrium and kinetics are reported for each ion, and deuterium isotope effects for the reactions of the 2-methyl-4-nitroisoquinolinium ion have been measured. Possible mechanisms for the reactions are discussed on the basis of the observed activation parameters and isotope effects and are compared with related reactions.
Studies of β-Diketone Complexes of Rhenium(V). The Molecular and Crystal Structure of trans-Dichlorobis(pentane-2,4-dionato)rhenium(IV)
Authors: Brown I. D. , Lock C. J. L. , Wan Che'ng
Published: May 2006

One of the compounds obtained by reacting acetylacetone with oxoethoxodichlorobis(triphenylphosphine)rhenium(V) has been shown by single crystal X-ray diffraction to be trans-dichlorobis(pentane-2,4-dionato)rhenium(IV). The crystals are triclinic, a = 8.032(4), b = 8.344(6), c = 7.429(6) Å, α = 118.1(2), β = 92.3(2), γ = 55.5(2)°, [Formula: see text], Z = 1. Intensities were measured with a microdensitometer from photographs recorded on an integrating precession camera. Of the 991 measured reflections all were observed and 984 were used in the refinement. The structure was refined by full matrix least squares to an R2 value of 0.0685. The compound was found to be a trans-monomer, in contrast to the dimeric structure claimed to exist in solution. The ligand atoms bonded to rhenium lie almost exactly at the apices of an octahedron and the bond lengths (Re—Cl, 2.326(8); Re—O1, 1.97(1); Re—O2, 2.01(1) Å) are in the range expected.
An Investigation of the Sn1−x SbxO2 System by Mössbauer Spectroscopy
Authors: Birchall T. , Bouchard R. J. , Shannon R. D.
Published: May 2006

The Sn1−xSbxO2 system has been studied by means of 119Sn and 121Sb Mössbauer spectroscopy. The presence of an unresolved quadrupole splitting in SnO2 is confirmed. The data show that the oxidation states of the tin and antimony are IV and V, respectively. The conduction electrons resulting from Sb substitution are distributed over the entire lattice. As the Sb content increases, the 119Sn isomer shift and s electron density at the Sn nucleus also increase, as expected for a conduction band composed largely of Sn 5s orbitals.
The Preparation of Specifically Deuterated trans- Cinnamyl Alcohol and trans- Cinnamic Acid
Authors: Lee Donald G. , Brownridge James R.
Published: May 2006

The reduction of ethyl phenylpropiolate by lithium aluminum hydride results in partial reduction of the triple bond to give trans-cinnamyl alcohol. If ethyl phenylpropiolate is reduced by LiAlD4 followed by work-up with acetone and H2O the product is the specifically labeled compound, trans-3-phenyl-2-propen-1-ol-1,1,2-d3. If the ester is reduced with LiAlH4 followed by work-up with acetone-d6 and D2O the product is trans-3-phenyl-2-propen-1-ol-O,3-d2. Oxidation of these two products by sodium ruthenate leads to formation of trans-cinnamic acid-α-d and trans-cinnamic acid-β-d, respectively.
Solute Radical Inactivation of the Sulfhydryl Enzyme Papain – Sensitization and Protection
Authors: Gaucher G. M. , Mainman Barbara L. , Armstrong D. A.
Published: May 2006

Particularly pure N2O-purged papain solutions (2 × 10−5 M; pH 6.8) were irradiated at 0 °C for different times with 60Co γ-rays, in the presence of 10−30 mM solutions of acetate, isobutanol, and thiocyanate. In comparison to OH radicals, these solute radicals substantially enhanced papain inactivation. Calculated inactivation probabilities per papain–radical reaction (i.e. 0.43 for OH and 1.00 for solute radicals) support this finding.In situ protection of both N2-purged and N2O saturated papain solutions by cysteine was found to occur only at cysteine: papain molar ratios above 15:1, while below this ratio substantial sensitization occurred, reaching a maximum at a 2:1 ratio. This enhanced inactivation of papain at low cysteine concentrations is primarily repairable in nature, and probably due to CysS• attack on papain's active site sulfhydryl. Only at relatively high cysteine:papain ratios (> 30) can protection be ascribed simply to radical scavenging.
The Interaction of Organomercury Pollutants with Biologically Important Sites: An X-ray study of the 2:1 Complex between Methylmercury and Penicillamine
Authors: Wong Yau Shing , Chieh Peter C. , Carty Arthur J.
Published: May 2006

The toxic pollutant methylmercurychloride forms 1:1 and 2:1 complexes with the sulfur amino acid DL-penicillamine. The mode of binding of the methylmercury by penicillamine has been established by a three-dimensional X-ray study of [CH3Hg]2(SC(CH3)2CHNH2COO).
Estimation of Phenols by the 4-Aminoantipyrine Method: Identification of the Colored Reaction Products by Proton Magnetic Resonance Spectroscopy
Authors: Jones Peter F. , Johnson K. E.
Published: May 2006

The products from the oxidation of several phenols in the presence of 4-aminoantipyrine have been isolated and their p.m.r. spectra examined. The results confirm the proposed formation of p-quinoneimide adducts and the elimination of the para-group in the case of reactive p-substituted phenols. Data from ortho substituted phenols reveal the formation of syn and anti geometrical isomers of the quinoneimide. In contrast, when the starting phenol has a meta-substituent, only a single isomer, the less hindered anti form, is obtained. An unusually large anisotropic effect of the antipyryl group, causing a deshielding of the closest proton on the quinoneimide ring, has been found. In the reaction between p-benzoquinone and 4-aminoantipyrine, the color obtained is due to the formation of the p-quinoneimide, and not to a charge-transfer complex.
In situ Generation and Electrophilic Addition Reactions of the Elements of 'XF'
Authors: Hall L. D. , Jones D. L.
Published: May 2006

Addition of the elements of 'IF' and of 'BrF' to alkenes can be effected by the in situ generation of these electrophiles from the halogen-AgF. For cyclohexene, 3,3,6,6-tetradeuterocyclohexene, methylenecyclohexane, styrene, and indene, these reactions are simple. However, for acenaphthylene, halogen–fluorine exchange and other reactions make the overall reaction quite complex. Electrophilic addition reactions for 1-fluoro-acenaphthylene are also described. The n.m.r. spectra of many of the products are given and discussed in some detail.
The Limiting Conductance of 1/3In3+ Ion and the Conductances of Aqueous Solutions of Indium Trichloride
Authors: Campbell A. N.
Published: May 2006

The direct determination of the limiting conductance of 1/3In3+ ion is not possible because of hydrolysis. This figure has been obtained by a method which may be open to criticism as 56.3 mhos, at 25°. If anything, this figure is too high.
La décomposition du tétraméthylgermane par les atomes Hg 6(3P1)
Authors: Duval Jocelyn , Rousseau Yves
Published: May 2006

The primary process in the mercury photosensitized decomposition of tetramethylgermane is a C—H bond cleavage. The hydrogen quantum yield, extrapolated at infinite pressure, is close to unity. Under mild conditions, hydrogen and 1,2-di(trimethylgermyl) ethane are the only products observed. At high intensities and low substrate pressures, atomic cracking occurs yielding methyl radicals which lead to the formation of methane.
The Hemicelluloses of Western Red Cedar (Thuja plicata (Donn))
Authors: Dutton Guy G. S. , Funnell Norman A.
Published: May 2006

The hemicelluloses of Thuja plicata (Donn) of the family Cupressaceae have been examined as part of a chemotaxonomic study. Little difference has been found from other Coniferales except that the xylan contains a percentage of L-arabinose lower than for many Pinaceae. Although 2- and 3-O-methylxylitol acetates are not separable by g.l.c. the composition of such a mixture may be determined by circular dichroism (c.d.) or by proton magnetic resonance (p.m.r.) spectroscopy.
Some New Iron Carbonyl Cluster Complexes of Di(tertiary arsines)
Authors: Chia L. S. , Cullen W. R. , Sams J. R. , Ward J. E. H.
Published: May 2006

New polynuclear iron carbonyl complexes having the stoichiometry LFe3(CO)10 have been obtained from the reactions of Fe3(CO)12 with the di(tertiary arsine) ligands (CH3)2AsC(X)(Y)CF2As(CH3)2 (X = Y = H; X = H, Y = F; X = F, Y = CF3). The structures of the new cluster complexes have been investigated using i.r., n.m.r., and Mössbauer spectroscopies. Mössbauer data are also reported for LFe3(CO)10 and LFe3(CO)9 derivatives of the mixed ligand [Formula: see text].
Free Radical Substitution Reactions of Sulfur Monochloride. A Limited Synthesis of Mercaptans
Authors: Tanner Dennis D. , Brownlee Brian G.
Published: May 2006

The photolysis of sulfur monochloride with a series of saturated aliphatic hydrocarbons yielded alkyl chlorides, di- and polysulfides, hydrogen chloride, and elemental sulfur. The free radical substitution reactions leading to the production of alkyl chloride and the di- and polysulfides were shown to proceed via a chlorine atom abstraction reaction. The major products, the di- and polysulfides could be transformed quantitatively, by lithium aluminum hydride reduction into their corresponding mercaptans. The reaction describes a simple free radical route to the synthesis of a variety of alkyl mercaptans.
The Crystal and Molecular Structure of trans-(Methyl)(but-2-yne)-bis(dimethylphenylphosphine)platinum(II) Hexafluorophosphate [(CH3)(H3CC≡CCH3)Pt(P(CH3)2]PF6
Authors: Davies Brian W. , Payne Nicholas C.
Published: May 2006

The crystal and molecular structure of trans-(methyl)(but-2-yne)bis(dimethylphenylphosphine)-platinum(II) hexafluorophosphate, [(CH3)(H3CC≡CCH3)Pt(P(CH3)2]PF6, has been determined from three dimensional X-ray diffraction data recorded by diffractometric methods. The structure has been refined by full-matrix least-squares methods on F using 1060 unique data to a conventional agreement factor R = 0.036. The crystals are orthorhombic, space group Pnma(D2h16), with a = 15.447(5), b = 15.344(4), c = 11.005(3) Å, and Z = 4. The coordination about the platinum atom is approximately square planar, if the acetylene is considered to be a unidentate ligand. There is crystallographic mirror symmetry imposed on the ions, such that the platinum atom, the methyl carbon atom, and the four carbon atoms of the acetylene ligand all lie on the mirror plane. The acetylene C≡C bond is approximately perpendicular (86.5(1.5)°) to the coordination plane of the platinum atom. The mean platinum–carbon(acetylene) bond length is 2.278(5) Å, and the mean angular departure from linearity of the ligand is 12(4)°. There is a small (156 cm−1) reduction of Vstr (C≡C) for the but-2-yne ligand upon coordination, and the acetylenic carbon–carbon bond length, 1.22(3) Å, is not significantly different from the value of 1.21(2) Å observed in the free ligand.
Theoretical Considerations and Equilibrium Conditions in Analytical Potentiometry. Computer Facilitated Mathematical Analysis of Equilibria in a Multicomponent System
Authors: Sarkar Bihudhendra , Kruck Theo P. A.
Published: May 2006

A method entitled "analytical potentiometry" is described which permits the accurate determination of the stability constants and of the distribution of simultaneously existing complex species in multi-component systems. A series of computer programs are introduced to facilitate the otherwise tedious mathematical analysis of data. Besides simple binary systems, this method is capable of dealing with mixed ligand coordination complexes and can be adapted to polynuclear systems. For many metal ions, there are no electrodes permitting the accurate determination of those ions over a wide enough concentration range. This method eliminates the need for metal ion specific electrodes. The concentration of free metal ions is determined indirectly by the use of a weak base and the glass electrode. These features bear great significance in resolving complex systems containing multiple species simultaneously which cannot be solved by the commonly known classical methods.
Structure of the Species in the Copper (II)–L-Histidine System
Authors: Kruck Theo P. A. , Sarkar Bibudhendra
Published: May 2006

The presence of simultaneously existing multiple species were taken into account in interpreting the structures of the complex species in the Cu(II)–L-histidine system. A refined proton displacement technique was utilized for structure elucidation of the species in solution. The absorbance and the molar extinction of the individual species were computed from the total absorbance and the species distribution over the pH range studied. The i.r. spectra of L-histidine and Cu(II)–L-histidine in D2O were obtained as a function of pD. They were interpreted in view of the species detected in a given pH range. The results of the species distribution as a function of pH, proton displacement, visible spectra of the individual species, and infrared data, were all combined to make structural interpretations. The following modes of metal coordination were proposed for the major species in the Cu(II)–L-histidine system: MHA, O(carboxyl) and N(imidazole); MH2A2, O(carboxyl) and N(amino) in both L-histidines; MA, O(carboxyl), N(imidazole), and N(amino); MHA2O(carboxyl), N(imidazole), and N(amino) in one L-histidine and O(carboxyl) and N(amino) in the other; MA2, O(carboxyl). N(imidazole), and N(amino) in both L-histidines, or O(carboxyl), N(imidazole), and N(amino) in one L-histidine and N(amino) and N(imidazole) in the other or an equilibrium mixture of both structures.
Reaction of Active Nitrogen with Tetrachloroethylene
Authors: Jones William Ernest , Rujimethabhas Manit
Published: May 2006

The reaction of active nitrogen with tetrachloroethylene yielded cyanogen chloride, trichloroacetonitrile, cyanogen, chlorine, and carbon tetrachloride. In addition, a yellow–brown polymer was found on the glass wall. A brief discussion of a possible mechanism is given.
Application of Carbon-13 Nuclear Magnetic Resonance to Conformational Analysis of Trimethylene Sulfites
Authors: Buchanan Gerald W. , Stothers J. B. , Wood Gordon
Published: May 2006

Carbon-13 n.m.r. chemical shifts are reported for trimethylene sulfite, 10 alkyl derivatives, and a related 1,3,2-dioxathiane. Data are discussed in terms of possible chair and twist conformations and in some cases the data permit definitive conformational assignments. Results are compared with previous conclusions based on proton n.m.r. and dipole moment measurements. The orientation of the S=O group is shown to have a very pronounced influence on the C-4 and -6 ring carbon shieldings.
On the Aggregation of Bovine Serum Albumin in 0.1 M Salt Solutions
Authors: Rosario Nanette O. Del , Sun Siao Fang
Published: May 2006

The molecular weight of bovine serum albumin at neutral pH in 0.1 M salt solutions was determined with light scattering measurements. Simultaneously, preferential binding of a salt to the protein was calculated. It was found that the protein aggregates in KI and KSCN, but not in KCl, LiCl, and LiBr solutions. Analysis of the sedimentation behavior has confirmed aggregation as a molecular phenomenon, not an artifact.
Biosynthesis of Lycomarasmin
Authors: POPPLESTONE C. R. , Unrau A. M.
Published: May 2006

Cultures of Fusarium oxysporum Schl. emend. Sny. et Hans. f lycopersici (Sacc.) Sny. et Hans. grown on a liquid medium with glucose as the principal carbon source produce, among other products, the phytotoxin lycomarasmin. Acid hydrolysis of lycomarasmin results in the formation of aspartic acid, glycine, and pyruvic acid. Tracer studies showed that glycine-U-I4C, L-serine-U-14C, DL-aspartic acid-4-14C, DL-alanine-1-14C, and glucose-U-14C served as relatively efficient precursors of the lycomarasmin molecule. DL-Aspartic acid-4-I4C was incorporated into the 4-carbon fragment without label scrambling. Glycine was found to be the most efficient precursor of the 2-carbon fragment while glucose afforded the most efficient and direct route for the 3-carbon fragment.
A Rapid Route to Hex-1-enopyran-3-uloses
Authors: Fraser-Reid Bert , Walker D. L. , Tam S. Y-K , Holder N. L.
Published: May 2006

Whereas the pseudo-axial 3-hydroxyl group of allal derivatives is known to be inert to manganese dioxide oxidation, the equatorial counterpart in glucal derivatives is shown to be readily oxidized. Thus glucal is converted to the 6-O-triphenylmethyl ether or 6-O-benzoyl ester to promote solubility in chloroform, and the derivatives are oxidized in that solvent in 12 h or less.Acetonation of glucal is readily accomplished in 45 min using 2,2-dimethoxypropane and p-toluenesulfonic acid in dimethylformamide; the product may be oxidized directly either with manganese dioxide or dipyridine chromium oxide. Thus it is possible to obtain 1–3-g quantities of the crystalline acetonated enone from triacetyl glucal (via deacetylation, acetonation, and oxidation) in 3–4 h.If the acetonation medium stands for 2 h methyl 2,3-dideoxy-4,6-O-isopropylidene-α-D-erythro-hex-2-enopyranoside is obtained. The mechanism of its formation in the reaction medium is discussed.
Vacuum Ultraviolet Photolysis of Trimethylethylene
Authors: Collin Guy J. , Gaucher Christian M.
Published: May 2006

The vacuum u.v. photolysis of trimethylethylene (2-methyl-2-butene) was carried out in a static system using rare gas resonance lamps: xenon (147.0 nm) and krypton (123.6 nm). The main hydrocarbon products were isoprene, 1,3-butadiene, propyne, allène, ethylene, and other minor products. Identification and measurements of the yields of hydrogen atoms, methyl, and ethyl radicals were carried out quantitatively by the use of radical–radical reactions. Because of the high yield of isoprene, the effect of conversion was studied. At a high conversion (i.e. 0.1%) the isoprene quantum yield decreases. Hydrogen atoms add mainly to the secondary carbon of the monomer (≥90%). The Δ(CH3,tert-C5H11) value was calculated to be 1.32 ± 0.14. With the krypton line (10.0 eV) no evidence was found for the participation of ionic reactions in the formation of the measured products except for the formation of 2-methyl-1-butene in a low yield. At this wavelength the ion quantum yield is 0.224 ± 0.005.
Solvation Enthalpies of Some Alkali Metal and Tetraalkylammonium Salts in Dioxane-Water Mixtures
Authors: Bhatnager Om N. , Campbell A. N.
Published: May 2006

Enthalpies of solution of LiCl, NaCl, (CH3) 4NBr, (C2H5)4 NBr, (C3H7)4 NBr, and (C4H9)4 NBr in dioxane-water mixtures varying in composition from 20 to 64.5% dioxane have been determined. Values of standard enthalpy of solution, ΔHs0, were obtained using the extended Debye–Hückel equation.Using these ΔHs0 and the lattice energies (U) of these salts, solvation enthalpies have been evaluated.
Détermination de la vitesse du son dans les sels fondus. Technique et applications
Authors: Denielou Lucien , Petitet Jean-Pierre , Tequi Christophe
Published: May 2006

This paper describes a technique for measuring the speed of sound in molten salts employing a pulse method. The signal coming from the sample is made to coincide with that coming from a delay line of a variable length of water. The intervening parts between the emitting and receiving crystals are made of sintered alumina. The calculation of corrections due to the intervening parts and the calculation of error are given in detail. The technique is applied to measure the speed of sound in potassium bromide, alkali sulphates and the chromate, molybdate and tungsten of sodium. [Journal translation]
Some Thermodynamic Properties of the Dimethylsulfoxide–Water and Propylene Carbonate–Water Systems at 25 °C
Authors: Lam S. Y. , Benoit R. L.
Published: May 2006

Molar excess free energies of the systems dimethylsulfoxide–water and propylene carbonate–water have been calculated from static vapor pressure measurements at 25 °C. Enthalpies of mixing at low water concentrations have also been determined. Possible association interactions in these systems are discussed.
Proton Spin–Spin Coupling Constants in Isothiazole, Isoxazole, and some of their Alkyl Derivatives
Authors: Wasylishen Roderick E. , Rowbotham J. Brian , Schaefer Ted
Published: May 2006

The signs and magnitudes of the spin–spin coupling constants over three to six bonds between protons in isothiazole, isoxazole, and in 10 of their alkyl derivatives are measured and discussed in terms of the coupling mechanisms. The chemical shifts of ring protons and methyl protons appear to arise from a common mechanism originating in the ring but are not simply related to electron densities calculated by molecular orbital theory at the CNDO/2 level of approximation.
A Nuclear Magnetic Resonance Investigation of Molecular Motion in Solid cis-Diaquotetramminecobalt(III)sulfate
Authors: Dunell B. A. , Nattrass J. F. , Ulrich S. E.
Published: May 2006

The second moment and spin lattice relaxation times have been obtained for cis-diaquotetramminecobalt(III)sulfate between 77 and 310 °K. The results suggest that one of the ammine ligands is unique, reorienting more slowly at a given temperature than the others. Both water ligands undergo C2- jumps. Although whole ion rotation does not occur libration does, and the second moment is interpreted in terms of such a torsional motion.
Influence of Lewis Acids on the Diels–Alder Reaction. VII. The Reaction of Furan with Ethyl Propiolate
Authors: McCulloch A. W. , Smith D. G. , McInnes A. G.
Published: May 2006

Reaction of furan and ethyl propiolate at 130° affords a low yield of 2,6-dicarbethoxy-9-oxatetracyclo[3.2.1.1.3,802,4]non-6-ene (4). This structure was confirmed by 1H and 13C n.m.r. spectroscopy. In the presence of AlCl3 the same addends give only a mixture of the Diels–Alder endo–endo10 and endo–exo11 diadducts. Isomer 11 is decomposed by AlCl3, the rate of decomposition, and therefore the product ratio 10:11, being as expected dependent on time, temperature, and reactant concentrations.
Nitrogen–Sulfur Ligand Systems via Reduction of Schiff's Base – Zinc Complexes Derived from Benzothiazolines
Authors: Corbin James L. , Work Dale E.
Published: May 2006

The coordinated imine groups of the Schiff's base – zinc complexes derived from various 2-substituted benzothiazolines are easily reduced with sodium borohydride to the corresponding amines. Removal of the metal ion from these reduced complexes yields the free ligands, providing a simple route to novel aminomercaptan chelating agents. Compounds of bi-, tri-, and tetradentate types were prepared in this manner.Evidence is given for a disproportionation of 2,2′-dimethyl-2,2′-bibenzothiazolinyl into 2-methylbenzothiazoline and 2-methylbenzothiazole in chloroform solution.
The Preparation of cis-1,3-Bis (dimethylarsino)-2,2,4,4-tetramethylcyclobutane and its Group VIB Metal Carbonyl Derivatives
Authors: Cullen William R. , Price John T.
Published: May 2006

The addition of tetramethyldiarsine to 2,2,4,4-tetramethylbicyclo[1.1.0]butane forms predominantly cis-1,3-bis(dimethylarsino)-2,2,4,4-tetramethylcyclobutane, L. The compound can behave as either a bridging or chelating ligand with group VIB metal carbonyls depending upon the reaction conditions affording LM(CO)4 and LM2(CO)10 (M=Cr, Mo, W). The structures of these derivatives are discussed.
Carbanions in Carbohydrate Chemistry: Synthesis of C-Glycosyl Malonates
Authors: Hanessian Stephen , Pernet Andre G.
Published: May 2006

The condensation of 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl bromide with sodio diethyl malonate led to crystalline diethyl 2-(2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl) malonate. The corresponding dibenzyl ester proved to be a versatile intermediate for the preparation of crystalline β-D-glucopyranosyl malonic acid and β-D-glucopyranosyl acetic acid derivatives. The anomeric configuration in these C-glycosides was determined by a chemical correlation. With 2,3,4,6-tetra-O-acetyl- β-D-glucopyranosyl chloride and sodio diethyl malonate, the major product was a 1,2-O-ketal derivative resulting from an attack of the carbanion on the 1,2-acetoxonium ion. The condensation of 2,3,4,6-tetra-O-benzyl-α-D-glucopyranosyl bromide with sodio diethyl malonate was conducted with, and without added bromide ion and the mechanistic implications of the results are discussed. C-Glycosides were also prepared in the D-mannofuranose series and their transformation into the D-lyxofuranose series (anomeric mixture) is described. The utility of n.m.r. shift reagents, and an apparent differential complexation by Eu(DPM)3 and Eu(FOD)3-d27 is demonstrated.
The Acylation of β-Keto Ester Dianions
Authors: Huckin Stuart Nicholas , Weiler Larry
Published: May 2006

A method for the successful acylation of the dianion of simple β-keto esters to yield β,δ-diketo esters has been developed. The dianion of methyl acetoacetate also reacts with the monoanion of methyl acetoacetate to give a triketo ester which cyclizes to methyl orsellinate. These dianions also add to nitriles to give 5-amino-3-keto-4-pentenoates which may in some cases cyclize to 4-hydroxypyridones.
The Transformation of Carvone into Racemic Grandisol
Authors: Ayer William A. , Browne Lois M.
Published: May 2006

Grandisol (1) is one of the components of the pheromone complex emitted by the male boll weevil. We report the transformation of readily available eucarvone (3), via the photoisomer 4, into grandisol in 20% overall yield. A key step in the synthesis is the Beckmann cleavage of oxime 15, derived in three steps from 4, to nitrite 16. Hydrolysis of 16 followed by hydride reduction gives grandisol (1).
Distribution Function and Angular Deformations of a Model Related to Vitreous Ice and Liquid Water
Authors: Kell G. S.
Published: May 2006

A random tetrahedral model, without bonding defects and in which the distance between nearest neighbors is constant, has been constructed to study the effect of angular variations from tetrahedral, and the observations have been interpreted in terms of vitreous ice and liquid water. The model was constructed to have relatively small deformations from tetrahedral, and the oxygen–oxygen–oxygen angles vary from 90 to 132°, with an interquartile width of 12°. The measured density is intermediate between that of hexagonal ice and liquid water and, because of the small angular deformations, provides an estimate both of the density of vitreous water and of the minimum density possible for a random tetrahedral system.
Crystal Structure of Hexamethylcyclotriphosphazene-Iodine (1:1 Adduct)
Authors: Markila Peter L. , Trotter James
Published: May 2006

Crystals of the title compound, N3P3Me6•I2, are triclinic, a = 10.707(13), b = 8.873(5), c = 8.871(6) Å, α = 96.65(6), β = 103.91(12), γ = 97.81(12)°, Z = 2, space group [Formula: see text] The structure was determined with MoKα diffractometer data by Patterson and Fourier syntheses, and was refined by full-matrix least-squares methods to R = 0.053 for 1934 observed reflexions. One atom of the iodine molecule is weakly bonded to nitrogen, N—I = 2.417(7), I—I = 2.823(1) Å, N—I—I = 177.8(2)°. The six-membered phosphazene ring is slightly non-planar, with a chair conformation. The two P—N bonds involving the nitrogen atom bonded to iodine are longer, mean 1.64 Å, than the other four P—N bonds, mean 1.598 Å Other mean dimensions are: P—C = 1.789 Å, N—P—N = 114.7, P—N—P = 124.0, C—P—C = 104°.
The Reaction of Iminophosphoranes with Dimethylformamide
Authors: Muchowski Joseph M.
Published: May 2006

It is shown that aliphatic iminophosphoranes react with dimethylformamide to produce N,N-dimethyl-N′-alkylformamidines.
One Step Synthesis of Thietane 1,1-Dioxide Derivatives from α-Amino Ketoximes
Authors: Chen Shi-Chow , Chow Yuan L.
Published: May 2006

One step conversion of cyclic α-amino ketoximes to 2-(ω-cyanoalkyl)-2-dialkylaminothietane 1,1-dioxides was described. The n.m.r. studies of the thietane 1,1-dioxides, using a combination of Eu(fod)3 shift reagent and decoupling technique, indicates the trans orientation of the substitution groups on the thietane ring.
Redox Behavior of Diazotized Amines in Aprotic Solvents
Authors: Elofson R. M. , Gadallah F. F. , Cantú A. A. , Schulz K. F.
Published: May 2006

The redox behavior of diazotized aromatic and aliphatic amines is discussed. The half-wave potentials of their cathodic and/or anodic waves is correlated with their chemical reactivity. The effect of redox reactions on the stability of the nitrogen moiety of diazo compounds is elaborated. The lability of nitrogen in the resulting ion-radical species is suggested as a key to fixation of nitrogen via redox schemes.
Lewis Acid Catalyzed Rearrangements of Nitroxide Radicals
Authors: Cazianis C. T. , Eaton D. R.
Published: May 2006

The interaction of nitroxide radicals with the Lewis acids, aluminum chloride and boron trifluoride has been investigated using e.s.r. and n.m.r. techniques. Three types of reaction have been demonstrated. Initially a paramagnetic complex with the nitroxide group is formed. This can then dimerize or polymerize to a diamagnetic complex. Concurrently rearrangement of t-butyl groups to s-butyl groups can occur giving a further series of radicals and complexes. The rearrangements are analogous to the well known carbonium ion rearrangements induced by Lewis acid catalysts. Relative equilibrium constants and rates for the various reactions are discussed in a qualitative manner.
Intrinsic Acidities of α, β, γ, Chlorosubstituted Aliphatic Acids from Gas Phase Equilibrian Mesurements
Authors: Yamdagni R. , Kebarle P.
Published: May 2006

not available
Pyridine-catalyzed Halogenation of Aromatic Compounds. I. Bromination
Authors: Dunn G. E. , Blackburn B. J.
Published: May 2006

The mechanism of catalysis of aromatic bromination by pyridine was investigated by measuring the rates of bromination of mesitylene in acetic acid and in chloroform with and without added pyridinium or other substituted ammonium salts. Most salts increased both the second- and third-order rate constants for bromination, and pyridinium salts were no more effective than others. Bromide salts decreased the rate and sometimes the order of the bromination reaction by complexing bromine as tribromide. The formation constants of pyridinium tribromide and tetra-n-butylammonium tribromide in chloroform at 25.0° were found to be 2 × 102 and 9 × 104 M−1 respectively. It is concluded that in dilute solution pyridine catalysis of bromination is simply a salt effect which can be accounted for by the commonly accepted mechanism of bromination.
Infrared Chemiluminescence from the Reaction of Oxygen Atoms with Chloroethylenes
Authors: Arnold S. J. , Kimbell G. H. , Snelling D. R.
Published: May 2006

Infrared chemiluminescence from vibrationally excited CO and from vibrationally excited HCl was observed when C2H3Cl, 1,1-C2H2Cl2, cis- and trans-1,2-C2H2Cl2, or C2HCl3 was introduced into a stream of oxygen atoms. The mechanisms describing the reactions of oxygen atoms with these molecules are discussed in detail. The initial step is postulated to involve the formation of an aldehyde and a carbene. The reaction step responsible for the formation of CO† is postulated to be[Formula: see text]and for HCl†[Formula: see text]
The Synthesis of 1, 2-Diazepines from Thiapyrylium Salts
Authors: Harris David John , Kan Gordon Y.-P. , Snieckus Victor , Klingsberg E.
Published: May 2006

The reactions of thiapyrylium salts 3a–c with hydrazine and methylhydrazine yield the 3,5,7-triphenyl-1,2(4H)-diazepines 4a–c and 1-methyl-3,5,7-triphenyl-1,2(1H)-diazepines 5a–c in good to excellent yields. Although numerous 1-acyl-1,2(1H)-diazepines are now known, compounds 5a–c represent the first examples of 1-alkyl-1,2(1H)-diazepine derivatives. With a slight variation in work up conditions, the reaction of thiapyrylium salts 3a and 3c with methylhydrazine leads to the formation of the pyrazoline derivatives 6a and 6c, respectively; on the other hand, only pyrazolines 9a and 9b can be obtained from the corresponding reaction with phenylhydrazine. Pyrolysis of the pyrazolines 6a, 6c, 9a, and 9b provides the pyrazoles 7a, 7c, 10a, and 10b, respectively. The mechanism of some of these transformations is briefly discussed.
On the Mechanism of Quenching by Amines: A New Method for Investigation of Interactions with Triplet States
Authors: Young Robert H. , Brewer D. , Kayser R. , Martin R. , Feriozi D. , Keller Richard A.
Published: May 2006

Rate constants for the quenching of singlet oxygen by a series of substituted N,N-dimethylanilines were obtained by a direct method employing a dye-laser. The Hammett ρ value obtained from the data (−1.71) suggests that a (partial) charge-transfer complex may be responsible for the quenching action. This rate data was combined with that obtained for the total quenching action on the sensitized photooxidation of 1,3-diphenylfuran. The quenching action on the photooxidation reaction is due to both the quenching of singlet oxygen and the quenching of the triplet state of the sensitizer (rose bengal or methylene blue). The combination of the data from each series of experiments resulted in rate constants of quenching of the triplet states of the sensitizers. A number of the N,N-dimethylanilines quenched the triplet states at the diffusion limit. Hammett ρ values (−1.86 for rose bengal and −4.19 for methylene blue) indicate that charge-transfer intermediates are probably responsible for the quenching action. This was confirmed by the observation of a transient intermediate assigned to the charge-transfer radical of methylene blue. The technique used here represents a novel approach to the investigation of triplet states.
Proton Magnetic Resonance Study of Intramolecular Hydrogen Bonding in Halophenols
Authors: Rowbotham J. Brian , Schaefer T.
Published: May 2006

The long-range spin–spin coupling constants over five bonds between the hydroxyl proton and the ring protons in a series of trihalophenols imply that the intramolecular hydrogen bond strength (negative enthalpy) to fluorine is greater than that to iodine by 75 ± 20 cal/mol, whereas the strengths to chlorine and bromine are 460 ± 60 cal/mol greater than to iodine. If a distinction can be made between chlorine and bromine, then chlorine–hydrogen bonds more strongly by only a few tens of calories per mol. The measurements were made mainly on dilute solutions in carbon tetrachloride at 32 °C.
Protonation of Polymethylphenols
Authors: Blackstock Stephen M. , Richards Kenneth E. , Wright Graeme J.
Published: May 2006

The protonation of a series of polymethylphenols in fluorosulfonic acid at −50° has been studied. For those phenols with no substituent at C-4, protonaton occurs exclusively at that position. Isomeric ions were obtained for all phenols with a methyl substituent at C-4. 4-Methylphenol and 2,4-dimethylphenol each gave three ions, one from O-protonation and two from protonation at C-2 and C-4, whereas 2,4-dimethylphenol, 2,3,4-, 2,4,5-, and 3,4,5-trimethylphenol, and 2,3,4,5-tetramethylphenol gave only the C-protonated species. These studies establish that although electronic factors are important, steric factors play a predominant role in determining the relative proportions of the various species.
Chloride Quantum Yields from Photolysis of Chloropentammine and Chloropentakisalkylamino Chromium(III) Complexes
Authors: Wong C. F. C. , Kirk A. D.
Published: May 2006

Determination of chloride quantum yields in the photolysis of [Cr(NH3)5Cl]2+ and chloropentakisalkylamino complexes has yielded values up to an order of magnitude lower than those reported in the literature. These determinations are described and the importance of the thermal production of chloride from the main photoproduct as a source of error is discussed. The similarity of the chloride quantum yields for the series of complexes confirm that our results for [Cr(NH3)5Cl]2+, which are at least an order of magnitude lower than the lowest reported in the literature, are closer to the correct value than the earlier data.
The Quenching of Singlet Oxygen (1Δg) by Transition Metal Chelates
Authors: Carlsson D. J. , Suprunchuk T. , Wiles D. M.
Published: May 2006

Various transition metal chelates were found to quench 1O2 in the liquid phase. 1O2 was generated either photochemically, from an ozonide, or with a microwave source and reacted with rubrene or 3-methyl-2-pentene. Rate constants for 1O2 quenching by the chelates were measured in various solvents using the three 1O2 sources, and compared with the constants of previously known 1O2 quenchers. The most efficient chelates quenched 1O2 at close to the diffusion controlled rate, as did β-carotene. Some quenchers of 1O2 in the liquid phase were qualitatively shown to quench in the solid state. The possible 1O2 quenching mechanisms of the chelates are discussed.
A Study of the Donor Properties of the Phenoxachalcogenines.: I. Tetracyanoethylene and Chloranil as Acceptors
Authors: Heller Charles A. , Zingaro Ralph A. , Meyers Edward A.
Published: May 2006

The phenoxachalcogenines have been studied as donors toward tetracyanoethylene (TCNE) as the acceptor. It was found that the thermodynamic values for the interactions show no significant trends when the chalcogenine atom is varied from Te to Se to S to O. For the four 1:1 complexes studied, the following average values for the thermodynamic properties were obtained at 20 °C (the total range for each quantity is given in parentheses): K = 1.4 (1.0) l mol−1 ΔG = 0.2 (0.4) kcal mol−1, ΔH = −2.0 (0.2) kcal mol−1 ΔS = −7.0 (0.5) cal deg−1 mol−1. The lack of any significant changes in the thermodynamic values is explained on the basis that all of the complexes involve similar interactions, probably of the π–π molecular complex type. The results were essentially the same for the interaction between phenoxatellurine (PTe) and chloranil (TCQ).
Oxidative Transfer Dehydrogenation of α,β-Unsaturated Carbinols to α,β-Unsaturated Ketones Catalyzed by Ruthenium Complexes
Authors: Sasson Yoel , Rempel Garry L.
Published: May 2006

The homogeneous competitive intermolecular and intramolecular hydrogen transfer from unsaturated carbinols to vinyl ketones in the presence of a number of ruthenium complexes is reported. The oxotriruthenium complex, Ru3O(OOCCH3)7 was used in applying this process for the oxidative transfer dehydrogenation of unsaturated carbinols to unsaturated ketones.
The Dimerization Constant of Nitrobenzene in Benzene: A Critique of Partition as a Thermodynamic Method
Authors: Goldman Saul , Duer Wayne C.
Published: May 2006

The dimerization constant (K) of nitrobenzene in benzene was determined at 5.5 and 25 °C by means of partition (solvent extraction). A hydration study was performed at these temperatures to determine the extent of hydration of nitrobenzene in the benzene phase. Published freezing point depression data for the anhydrous benzene–nitrobenzene system were used to obtain a value of K at 5.5 °C. The heats of solution of nitrobenzene in benzene (anhydrous) were determined at 25 °C. The heat of solution and freezing point depression data were combined to obtain a value of K for the anhydrous system at 25 °C. At each of 5.5 and 25 °C the value of K determined by partition was significantly smaller than the corresponding value of K for the anhydrous system, and the discrepancy was larger at 25 than at 5.5 °C. It was found that by fitting a simple electrostatic model to the difference in the values of K found at 5.5 °C, the difference at 25 °C could be predicted.
Marine Organic Chemistry. II. Synthesis of 3β,6α-Dihydroxy-5α-pregn-9(11)-en-20-one, the major Sapogenin of the Starfish Asteriasforbesi
Authors: ApSimon John W. , Eenkhoorn Johan A.
Published: May 2006

A seven-step synthesis of 3β,6α-dihydroxy-5α-pregn-9(11)-en-20-one (7), starting from 11-oxoprogesterone, is presented.
The Mass Spectra of Derivatives of Polyporic Acid
Authors: Grigsby R. D. , Jamieson W. D. , McInnes A. G. , Maass W. S. G. , Taylor A.
Published: May 2006

The diacetate and di-O-methyl derivative of polyporic acid have anomalous mass spectra. Ions are observed at m/e values equal to the molecular weight but ions 2 mass units larger than these, often of greater intensity, are also observed. The abundance of such ions depends on the temperature of the sample, the pressure in the source, and the partial pressure of water in the instrument. In addition, ions m/e 420 and 462 are found in the spectrum of the diacetate which are parents of the M + 2 ion(s). Similarly, M + 17 and M + 32 ions are observed in the spectrum of the dimethoxy compound. When deuterium oxide and the ester or the perdeuterioacetyl derivative were introduced into the source M + 4 ions were seen in the mass spectra. These unusual reactions should permit diagnosis of the 2,5-dihydroxy-1,4-benzoquinone moiety in newly isolated natural products.