bluuebunny/crossref_metadata_2025 huggingface dataset:
Bond dissociation energies and bond orders of diatomic alkali-earth halides
Authors: Reddy R. R. , Reddy A. S. R. , Reddy V. Krishna
Published: May 2006

New relations are proposed for the determination of bond dissociation energies of diatomic alkali-earth halides. The relations are[Formula: see text]and[Formula: see text]where [Formula: see text], Δx represents Pauling's electronegativity differences (XA − XB) and rc is the internuclear distance. The estimated bond energies are in reasonably good agreement with the literature values. The errors calculated with our suggested relations for bond energies are 9.9% and 7.5% respectively. The corresponding errors evaluated from Matcha's and Pauling's equations are 6.1 % and 48.2%, respectively. A simplified formula for the determination of bond orders of alkali-earth halides has been suggested. The formula has the form [Formula: see text]. The definition for bond order given by Parr and Borkman differs from that given by Politzer. Thorough investigation of the two statements reveals that the Politzer's definition is a better one.
The preparation of specifically deuterated diphenylamines
Authors: Doak Wesley A. , Knessl Charles , Labaziewicz Henryk , O'connor Sally E. , Pup Liviu , Putz Gerard , Schranz Marijo , Walter Robert I. , Yang Ling , Werstiuk Nick H.
Published: May 2006

Procedures have been developed for the preparation, at levels of label which exceed 90%, of ring-deuterated diphenylamines (DPAs) with the label at specific ring positions. The compounds so prepared are DPA-d10, DPA-2,4,6,2′,4′,6′-d6, DPA-2,6,2′,6′-d4, and DPA-4,4′-d2.
Structure cristalline du complexe de magnésium de la calcimycine (A. 23187)
Authors: Alléaume Marc , Barrans Yvette
Published: May 2006

The 1:2 magnesium ion complex of the antibiotic calcimycine (A. 23187) crystallizes in the space group P21, with cell dimensions a = 11.152(2), b = 27.684(2), c = 10.168(2) Å, β = 107.02(2)°, and Z = 2. The structure was refined to an R = 0.063 based on 3473 observed reflections. The octahedral coordination of the Mg2+ ion is highly symmetrical. Each calcimycine ion is bound to Mg2+ through a carboxyl oxygen, a carbonyl oxygen, and the nitrogen of the benzoxazole ring system. The Mg—O distances are respectively 2.00 Å and 2.06 Å, the Mg—N distances 2.23 Å [Formula: see text].
Trapping of o-quinodimethane with p-quinones: synthesis of tetrahydro-1,4-anthracenediones
Authors: Askari Syed , Lee Susan , Perkins Robert R. , Scheffer John R.
Published: May 2006

Previous work from our laboratory has been concerned with investigating the photochemical reactivity of the tetrahydro-1,4-napthalenedione system, both in solution and the solid state. The results obtained prompted us to extend our studies to the analogous tetrahydro-1,4-anthracenedione system. The most direct method of synthesis of the desired compounds is through Diels–Alder addition of o-quinodimethane to p-quinones. Because of the ease with which the adducts would be expected to undergo bis-enolization to the corresponding hydroquinones, their preparation requires mild, neutral conditions. After much experimentation, success was achieved using the Durst–Charlton sulfur dioxide extrusion method for generating o-quinodimethane from 3,6-dihydro-1,2-oxathiin-2-oxide. Insitu trapping using p-benzoquinone and other substituted p-quinones afforded the desired adducts in reasonable yields. In the case of duroquinone and 2,3-dimethyl-1,4-naphthalenedione, fluoride ion-catalyzed generation of o-quinodimethane from [o-[α-(trimethylsilyl)methyl]benzyl]trimethylammonium bromide by the method of Ito also gave acceptable results; however, the bis-enolizable adducts were not stable under these eaction conditions.
Infrared spectra of hydrogen bonded adducts of 2,6-dichlorophenols and oxygen bases
Authors: Wolny R. , Koll A. , Sobczyk L.
Published: May 2006

Infrared spectra of hydrogen bonded complexes of 2,6-dichlorophenol derivatives and oxygen bases have been studied over a broad ΔpKa range (from −10.55 to +1.69). For the complexes of 1:1 stoichiometry typical evolution of spectra, similar to those for other hydrogen bonded systems, have been found. With an increase of ΔpKa the hydroxyl group stretching vibration band shifts to lower frequencies until the inversion region is reached, where hydrogen bonded (HB) and proton transfer (PT) forms occur in equilibrium, then abroad background absorption is observed. The centre of gravity of the broad protonic bands, veg, calculated from the integrated intensity over the whole infrared region have been correlated with ΔpKa and the contribution of the PT form. It has been shown that the minimum on the plot veg vs. ΔpKa is reached close to the inversion point, where KPT = 1. The observed correlations and the change in the shape of the broad protonic absorption are consistent with expectations of theories based on the concept of the double minimum potential function and the stochastic mechanisms of band broadening.
Structural, magnetic, and spectroscopic studies of tetrakis(pyridine) complexes of iron(II) sulfonates
Authors: Haynes John S. , Rettig Steven J. , Sams John R. , Thompson Robert C. , Trotter James
Published: May 2006

The iron(II) complexes Fe(NC5H5)4(RSO3)2 where R = CF3, CH3, and p-CH3C6H4 have been prepared and their crystal structures determined by single crystal X-ray diffraction. Crystals of trans-bis(methanesulfonato-O)tetrakis(pyridine)iron(II) are monoclinic, a = 16.524(2), b = 9.1127(6), c = 18.684(2) Å, β = 109.903(6)°, Z = 4, space group Pn. The structure was solved by conventional heavy-atom methods and was refined by full-matrix least-squares procedures to R = 0.034 and Rw = 0.038 for 4243 reflections with I ≥ 3α(I). Crystals of trans-bis(trifluoromethanesulfonato-O)tetrakis(pyridine)iron(II) are monoclinic, a = 10.456(1), b = 9.2981(8), c = 14.625(2) Å, β = 96.372(6)°, Z = 2, space group Pn. Structure solved and refined as above to R = 0.036, and Rw = 0.037 for 1483 reflections with I ≥ 3σ(I). Crystals of trans-bis(p-toluenesulfonato-O)tetrakis(pyridine)iron(II)are orthorhombic, a = 40.818(2), b = 9.8722(6), c = 17.3544(7) Å, Z = 8, space group Fdd2. The structure was solved by Patterson and Fourier syntheses and was refined by full-matrix least-squares procedures to R = 0.030 and Rw = 0.032 for 1851 reflections with I ≥ 3σ(I). All three structures show discrete octahedral molecules with monodentate trans-coordinated sulfonate groups. Two crystallographically independent molecules are observed in the R = CH3 structure, the difference between them involving the orientation of the CH3SO3 groups with respect to the O—Fe—O vector. The FeN4O2 chromophore in each compound is a tetragonally compressed octahedron (approximate D4h, symmetry) with average Fe—N distances of 2.21, 2.23, and 2.24 Å and Fe—O distances of 2.11, 2.06, and 2.08 Å for theCF3, CH3, and p-CH3C6H4 derivatives, respectively. The compounds were studied using vibrational, electronic, and Mössbauer spectroscopic methods, magnetic susceptibility measurements, and differential scanning calorimetry. Quadrupole splitting values from Mössbauer spectra indicate a 5B2g ground state for all three compounds and magnetic susceptibility data (310–4.2 K) have been analyzed assuming this ground state, using both a crystal field and a zero-field splitting model.
Metal ion – biomolecule interactions. X. Synthesis, spectroscopic and magnetic resonance investigations of methylmercury(II) complexes of the sulfur modified nucleosides 6- mercaptopurine riboside and 2-amino-6-mercaptopurine riboside
Authors: Buncel E. , Kumar R. , Norris A. R.
Published: May 2006

A number of methylmercurated complexes of 6-mercaptopurine riboside and 2-amino-6-mercaptopurine riboside (6-MNucH2) containing S-bound CH3Hg(II) in neutral and cationic complexes (as in [CH3Hg(6-MNucH)] and [CH3Hg(6-MNucH2)]NO3), S- and N-bound CH3Hg(II) (as in [(CH3Hg)2(6-MNucH)]NO3), and S-, N-, C-bound CH3Hg(II) (as in [(CH3Hg)3(6-MNuc)]NO3) have been prepared in aqueous solution at appropriate pH and mole ratios of the constituents. The complexes were characterized by means of 1H and 13C nmr and ir spectroscopy and elemental analysis. Formation of C-bound methylmercurated species extends our previous results obtained with xanthosine, inosine, and imidazole derivatives, and substantiates our proposal that activation through electrophilic coordination at N(7) is a requirement for C(8)—H abstraction. 2J(1H–199Hg) coupling constants, measured in (CD3)2SO for a number of CH3Hg(II) complexes of N-, S-, and C-donor heterocyclic ligands, including the 6-mercaptopurine riboside of the present study, correlate well with the 1J(13C–199Hg) coupling constants, according to 1J = 8.4602J − 155.6. The significance of this correlation in terms of the strength of the Hg–ligand bond is considered. The results could provide insight into the apparent selectivity of binding of CH3Hg(II) by bio-ligands, as well as in the design of chemotherapeutic agents for the treatment of methylmercury poisoning.
An extension of the Beierbeck and Saunders parameters for the semiempirical calculation of the 13C nuclear magnetic resonance chemical shifts: the gauche-γ(X) effect in epoxides
Authors: Colombo Maria I. , Bustos Daniel A. , Gonzalez-Sierra Manuel , Olivieri Alejandro C. , Ruveda Edmundo A.
Published: May 2006

An additional substituent parameter, the gauche–γ(X), was derived and a correction for the HC parameter of Beierbeck and Saunders is proposed; this new parameter would allow the semiempirical calculation of 13C nuclear magnetic resonance shifts of six-membered ring epoxides and, consequently, their stereochemistry.
A comparison of electron spin resonance α- and β-hyperfine coupling constants in para-substituted α-phenethyl radicals
Authors: Arnold Donald R. , Nicholas A. Martin de P. , Young Kent M.
Published: May 2006

The linear relationship between the electron spin resonance hyperfine coupling constants (hfc) of the α- and β-hydrogens of para-substituted α-phenethyl radicals provides experimental evidence that the magnitude of both the α- and β -hfc is determined largely by the extent of spin delocalization in these benzylic systems. The [Formula: see text] scale, developed using substituted benzyl radicals, is shown to apply to phenethyl radicals as well.
The reduction of (1-(4-cyanophenyl)-3-hydroxy-2-buten-1-one-N)pentaamminecobalt(III) by chromium(II)
Authors: Balahura Robert J. , Johnston A.
Published: May 2006

The reduction of the title compound,[Formula: see text]by chromium(II) is first order in Cr(II) and obeys the rate law kobsd = k1Ka′/(Ka′ + [H+]) at 25.0 °C and I = 1.0 mol L−1 (LiClO4) with k1 = (2.9 ± 0.1) × 104 L mol−1 s−1 and Ka′ = 0.86 ± 0.03 mol L−1. In the rate law, k1 refers to reduction of the 3+ ion above and the Ka′ is the acid dissociation constant for the protonated form of 1. The reduction occurs by a remote attack inner-sphere mechanism with complete transfer of the organic ligand to chromium.
Transferts d'électrons assistés par les métaux de transition:influence de la nature du cation métallique sur la réduction de composés carbonylés en milieu aprotique
Authors: Fournier Françoise , Fournier Michel
Published: May 2006

The pinacolisation of ketones is enhanced when a bivalent transition metal cation is present. This phenomenon is general and occurs with Cr2+, Mn2+, Fe2+, Co2+, Zn2+ but not with Ni2+. The cathodic reduction leads to α-glycols with a good yield, without any resin production, and at a less negative potential than that of the ketone itself. The distribution of all isolated compounds is dependent on the Lewis character-acidity and complexing power of the metallic cation. Thus, for the dimerization, the greatest specificity is generally observed when Fe2+ is present. For the chalcone, the better stereoselectivity is obtained with Zn2+. No evidence of initial carbonyl complex of the metal ion was shown.
Hydridoiridium(III) sulfoxide complexes and their reactivity toward dioxygen
Authors: James Brian R. , Morris Robert H. , Kvintovics Pal
Published: May 2006

Synthetic routes to hydridoiridium(III) dimethylsulfoxide complexes via oxidative addition of HCl or H2 to precursor insitu iridium(I) species are described. The complexes, trans, mer-IrHCl2(DMSO)3 (1a) and cis, mer-IrH2Cl(DMSO)3 (2), have been characterized by 1H nmr and ir, and contain only S-bonded sulphoxide, DMSO. Comparison is made with data for other isomers reported in the literature, and some discrepancies are discussed. The decomposition of 1a and 2 in chloroform leads to isomers of IrCl3(DMSO)3, while (2) with HCl generates cis,cis IrHCl2(DMSO)2(DMSO) with the O-bonded sulfoxide trans to hydride. The reaction of 1a in dichloromethane with dioxygen occurs with a 1:1 stoichiometry and generates two complexes tentatively formulated as Ir(OH)Cl2(DMSO)2H2O (3) and IrCl2(O2)(DMSO)2DMSO (4); a hydroperoxide intermediate (Ir—OOH) initially formed from 1a is considered to react with further 1a in the rate-determining step. Oxidation of coordinated DMSO to the sulphone is not observed, implying that such a catalyzed O2-oxidation reported earlier in aqueous 2-propanol proceeds via reaction of IrOOH with free DMSO, or else via free hydrogen peroxide.
A simple, biogenetically modeled synthesis of 4-(methylthio)butyl thiocyanate: the reaction of thiocyanate anion with S-methyl-(1,n)-epithionium ions
Authors: Benn M. H. , Singh Vinod K.
Published: May 2006

The reaction of S-methylthiolanium fluorosulphate with thiocyanate ion gives predominantly 4-(methylthio)butyl thiocyanate, a result which is in accord with a hypothesis for the biogenesis of this compound, and which has implications for the natural occurrence of analogous thiocyanates.
Polarized overtone-combination bands in the near-infrared spectra of K2SnCl4•H2O and KSnCl3•H2O at cryogenic temperatures
Authors: Walker Ian M. , McCarthy Paul J.
Published: May 2006

The near-infrared (nir) spectra of K2SnCl4•H2O and KSnCl3•H2O contain many highly polarized absorptions, due largely, if not completely, to combinations of vibrations of the water molecules in the crystals. The polarization of the absorptions can be related to the site symmetry of the water molecule. In K2SnCl4•H2O combination bands based on rocking, wagging, and twisting librations are seen, from which it is possible to definitively identify the rocking libration. The librations are much less in evidence in the spectra of KSnCl3•H2O. Sets of normal mode anharmonicity constants have been calculated from the energies of the absorptions.
Aza analogues of protoberberine and phthalideisoquinoline alkaloids
Authors: Jahangir Jahangir , MacLean David B. , Holland Herbert L.
Published: May 2006

Anions derived from furo[3,4-c]pyridin-3(1H)-one, by treatment with lithium diisopropylamide, react with substituted, 3,4-dihydroisoquinolines and 2-methyl-3,4-dihydroisoquinolinium salts yielding nitrogen analogues of the protoberberine and phthalideisoquinoline alkaloids, respectively.
Preparation of deuterium labelled styrenes and divinylbenzenes
Authors: Werstiuk Nick Henry , Timmins George
Published: May 2006

Specifically deuteriated styrenes (1-d, 2,2′-d2, and ring labelled), perdeuteriostyrene, and specifically deuteriated divinylbenzenes (1,1′-d2,2,2,2′,2′-d4, and ring labelled) have been prepared by transforming suitably labelled phenylacetic (hydride or deuteride reduction and dehydration by solid KOH) and phenylenediacetic acids (esterification, hydride or deuteride reduction, and dehydration by solid KOH), respectively.
The reactions of O(3P) with 2-propanone, 2-butanone, and 3-pentanone
Authors: Roscoe John M.
Published: May 2006

The reactions of O(3P) with 2-propanone, 2-butanone, and 3-pentanone have been studied kinetically as a function of temperature and substrate concentration. The absolute rate constants for these reactions in the gas phase, in the units M−1 s−1, obey the following relations.[Formula: see text]The activation energies for these reactions are comparable to those for the reactions of O(3P) with alcohols, but the preexponential factors for the reactions of O(3P) with these ketones are significantly smaller than those for the analogous reactions with alcohols. The available data indicate that the reactivity of O(3P) toward ketones shows a variation with polar effects of substituents which is similar to that found for the reactions of OH with ketones.
Atomic properties and the reactivity of carbenes
Authors: MacDougall Preston J. , Bader Richard F. W.
Published: May 2006

The properties of the atoms in a number of substituted carbenes and silylene provide an understanding of the relative stabilities of their lowest lying singlet and triplet states and of their differing chemical reactivities. The theory of atoms in molecules defines all of an atom's properties, including its energy. In this research one finds that the methylenic carbon or silicon atom is energetically most stable in the triplet state of each system, while the ligands are most stable in the corresponding singlet state. It is also found that the average electron populations of the carbon and silicon atoms are largest in the triplet states. In systems where the carbon or silicon atom bears a net positive charge, as found in CHNH2, CF2, and SiH2, the excess in the transfer of charge to the more electronegative ligands in the singlet states stabilizes the ligands more than it destabilizes the central atom. These systems have singlet ground states. The relative susceptibility of singlet and triplet carbenes to electrophilic and nucleophilic attack is determined by the properties of the Laplacian of the charge distribution. This quantity assimilates the model of localized electrons in terms of local concentrations of electronic charge. It also determines regions from which electronic charge is locally depleted. These regions are found to coincide with those where the lowest-lying vacant orbital is concentrated.
Infrared spectroscopic studies of solvent effects on the conformation of n-alkanes
Authors: Casal H. L. , Yang P. W. , Mantsch H. H.
Published: May 2006

The infrared spectra of specifically deuterated n-tridecane-7,7-d2 pure and mixed with several linear and branched hydrocarbons have been measured as a function of temperature. The average gauche fraction at the middle of the n-tridecane chain has been determined from the intensities of conformation-specific CD2 rocking bands. The results indicate that the concentration of gauche rotamers in the centre of the n-C13 chains varies with the solvent. For example, when n-tridecane is dissolved in other n-hydrocarbons the gauche concentration decreases when the chain length of the solvent is shorter than n-C13 and increases when the solvent chains are longer than n-C13. However, no simple, direct correlation is found between these solvent-induced changes in gauche concentration and measured thermodynamic quantities of mixing.
Ternary charge-transfer complexes. III. Complexes with Group V elements in the anion
Authors: Brownstein Sydney , Gabe Eric , Lee Florence , Piotrowski Andrej
Published: May 2006

NOMX6•aromatic charge-transfer complexes are formed where M may be P, As, orSb, X maybe For Cl, and aromatic may be benzene or a methyl-substituted benzene. Nuclear magnetic resonance and optical spectral parameters are given and three crystal structures reported. Appreciable conductivity is found for NOSbCl6•polystyrene and NOSbF6•hexamethylbenzene.
Substrates for the differentiation of the N-acetylglucosaminytransferases. Synthesis of βDGlcNAc(1 → 2)αDMan(1 → 6)βDMan and βDGlcNAc(1 → 2)αDMan(1 → 6) [αDMan(1 → 3)]βDMan glycosides
Authors: Tahir S. Hasan , Hindsgaul Ole
Published: May 2006

The trisaccharide βDGlcNAc(1 → 2)αDMan(1 → 6)βDMan (2) and the tetrasaccharide βDGlcNAc(1 → 2)αDMan(1 → 6)[αDMan(1 → 3)]βDMan (3) have been chemically synthesized as their 8-methoxycarbonyloctyl glycosides. Compounds 2 and 3, both partial structures of naturally occurring asparagine linked oligosaccharides, are designed to function as selective substrates in N-acetylglucosaminytransferase assays.
The addition of electrophiles on ester enolates containing an oxygen in the β-position. A stereoelectronically controlled reaction
Authors: Caron Maurice , Kawamata Takeshi , Ruest Luc , Soucy Pierre , Deslongchamps Pierre
Published: May 2006

The enolate anion derived from spiro ketal methyl esters (1, 3, and 4) reacts with various electrophiles (PhSeBr, Ch3I, O2, I2, (CH3S)2, and (PhS)2) to yield as the major product, the isomer resulting from an equatorial approach of the electrophilic reagent. This stereochemically controlled reaction is discussed in terms of stereoelectronic effects that increase the electron density of the α face of the enolate anion.
Electron transport in dense gases: limitations on the Ioffe-Regel and Mott criteria
Authors: Gee Norman , Freeman Gordon R.
Published: May 2006

In the gas phase, the Ioffe–Regel criterion that electron transport becomes modified when the mean free path equals the electron wavelength (L = λ) applies clearly only to helium and hydrogen, which have a net repulsive interaction with electrons. The Mott criterion, that when L = λ/2π the electron is in a localized state, also applies to these two gases. The two criteria are less effective for molecules that have net attractive interactions with the electrons, because the interactions are not simply additive. They are not useful for xenon gas. The criteria are also assessed for: (a) several highly polarizable, spherical and nonspherical molecules; (b) polar molecules; (c) nitrogen and carbon dioxide, which form transient anions.
Étude par résonance magnétique nucléaire du platine-195 de la réaction de cis-[Pt(éthylméthylsulfoxyde)2Cl2] avec un sel d'argent
Authors: Rochon F. D. , Girard Louise
Published: May 2006

The products of the reaction of cis-[Pt(EMSO)2Cl2] (EMSO = ethylmethylsulfoxide) with Ag2SO4 were studied by 195Pt nuclear magnetic resonance. The results have shown the presence of several species in aqueous solution. The reactions were done at different conditions of pH. The spectra of two isolated oligomers were also measured. The hydroxy-bridged dimer and trimer show a signal around −2900 ppm while the hydrolyzed monomers have signals around −3200 ppm. A semi-quantitative profile of the different equilibria in solution is suggested.
Fast disproportionation of hexacyanomanganate(III) in acidic solution. Formation of hexacyanomanganate(IV) and kinetics of its decomposition
Authors: López-Cueto Guillermo , Ubide Carlos
Published: May 2006

When potassium hexacyanomanganate(III) dissolves in acidic solution it rapidly disproportionates into hexacyanomanganate(IV) and Mn(II). Hexacyanomanganate(IV) then slowly decomposes to yield Mn(II) and (CN)2. Kinetics of the latter reaction has been studied. The reaction is found to be first order with respect to [Formula: see text], H+, and Mn(II) concentrations and the experimental rate law has the form v = kobs[Mn(IV)] = (ka + kb[H+] + kc[Mn(II)])[Mn(IV)]. At 40 °C and ionic strength 2.0, ka, kb, and kc values are (1.78 ± 0.01) × 10−4 s−1, (5.97 ± 0.05) × 10−5 s−1 M−1, and (3.40 ± 0.18) × 10−3 s−1 M−1, respectively. A mechanism with three parallel pathways is proposed, the deduced rate law being similar to the experimental one. Activation parameters, ΔH≠and ΔS≠ for the rate constants ka, kb, and kc are also reported.
Synthesis of the subterminally 6-O-phosphorylated trimannosides found on carbohydrate chains of lysosomal enzymes
Authors: Srivastava Om. P. , Hindsgaul Ole
Published: May 2006

The three possible subterminally 6-O-phosphorylated trimannosides (2–4) found on the asparagine-linked carbohydrate chains of lysosomal enzymes have been chemically synthesized as their 8-methoxycarbonyloctyl glycosides, R = (CH2)8COOCH3. The key step in the syntheses involves glycosylation of suitably protected α-D-mannopyranosides 5–7 with the phosphorylated mannobiosyl donor 2-O-(2,3,4,6-tetra-O-acetyl-α-D-mannopyranosyl)-3,4-di-O-benzyl-6-O-di-phenylphosphoryl-α-D-mannopyranosyl chloride (14), which produced mixtures of α- and β-linked trisaccharidic products. Compounds 2 (αDMan(1 → 2) αDMan 6-phosphate(1 → 2)αDManOR), 3 (αDMan(1 → 2)αDMan 6-phosphate(1 → 3)αDManOR), and 4 (αDMan(1 → 2)αDMan 6-phosphate(1 → 6)αDManOR) are being used in a study of the targeting of enzymes to the lysosomes by phosphomannosyl receptors.
Reduction of carbonyl compounds promoted by silicon hydrides under the influence of trimethylsilyl-based reagents
Authors: Aizpurua Jesús M. , Lecea Begoña , Palomo Claudio
Published: May 2006

The synthetic utility of hydrosilanes under the influence of trimethylsilyl-based reagents as new reducing systems is described. 1,1,3,3-Tetramethyldisiloxane (TMDS) reagent in combination with iodotrimethylsilane or bromotrimethylsilane produces alkyl halides from aldehydes in good to excellent yields. Polymethylhydrosiloxane (PMS) in the presence of iodotrimethylsilane also produces benzyl iodides in excellent yields. On the contrary, PMS reagent was found unsuitable for the synthesis of benzyl bromides. Similarly, TMDS reagent in combination with trimethylsilyl triflate produces symmetrical ethers from aldehydes without concomitant formation of competitive products. Under similar conditions, PMS reagent failed to provide the expected symmetrical ethers and Friedel–Crafts products were formed. Reduction of quinones to hydroquinones is also described.
Cellules photoélectrochimiques de phtalocyanine d'hydroxyaluminium déposées par rotation
Authors: Perrier Gérard , Dao Lê H.
Published: May 2006

The spin-coating technique was used to produce hydroxyaluminum phthalocyanine (PcAlOH) photoelectrochemical cells. The spectral and electrical behavior of NESA/PcAlOH/BQ/HQ/Pt cells is studied and comparisons are made with cells based upon sublimed PcAlOH films. Due to the weak solubility of PcAlOH in volatile organic solvents, the DMSO used in the spin-coating method seems to be trapped in the solid film, and leads to a decrease in the photoelectrochemical cell efficiency. Studies on the influence of the counter-electrode showed that a vanadium counter-electrode gave higher values of Jsc, Voc, and η than a platinum one, but corrision phenomena were observed in that case.
Sulfur extrusion from 1,4-benzothiazepines: formation of 3-aryl-4-carbomethoxyisoquinolines
Authors: Fodor Lajos , MacLean David B.
Published: May 2006

Treatment of 3-aryl-2-carbomethoxy-4,5-dihydro-1,4-benzothiazepines with N-chlorosuccinimide in ether gave 3-aryl-4-carbomethoxyisoquinolines in a reaction in which the sulfur atom was extruded from the seven-membered thiazepin ring.
Chemical constituents of Lansiumanamallayanum Bedd.
Authors: Purushothaman K. K. , Sarada A. , Saraswathy A.
Published: May 2006

Several triterpenoids and steroids have been isolated from Lansiumanamallayanum Bedd. The leaves yielded an unknown triterpene lansitriol and four new steroids, lansisterone E1, lansisterone Z2, lansisterol B, and lansisterol A 3. From the bark, a new triterpene lactone designated as lansilactone 4 was isolated. Structures for compounds 1, 2, 3, and 4 have been proposed as 3β,4β-dihydroxy-17(20)-trans 5α-pregna-16-one; 3β,4β-dihydroxy-17(20)-trans 5α-pregna-16-one; 24-methylene 3β,4β,7β, 20-tetrahydroxy cholest-5-ene, and 25,26,27-lanostane trisnorlactone.
A simple and efficient synthesis of 5′-(2H3)olivetol
Authors: Girard Michel , Moir David B. , ApSimon John W.
Published: May 2006

The title compound 1 was prepared in 13% overall yield starting from the commercially available and inexpensive 3,5-dimethoxybenzoic acid (4). The n-pentyl side chain was elaborated from cross-coupling reactions between halides.
A synthetic strategy for tricholomic acid and acivicin
Authors: Hanessian Stephen , Vanasse Benoit
Published: May 2006

A synthetic strategy towards tricholomic acid and acivicin has been established using the aldol condensation of N-pyruvilideneglycinatoaquocopper(II) and an optically active aldehyde derived from S-malic acid as the key bond-forming reaction. Although a viable strategy was developed, no asymmetric induction was observed.
Alcaloïdes bisbenzylisoquinoléiques de Albertisia cf. A. papuana
Authors: Lavault Marie , Bruneton Jean , Cavé Adrien , Chan Kai Cheong , Deverre Jean Robert , Sevenet Thierry , Guinaudeau Hélène
Published: May 2006

Four new bisbenzylisoquinoline alkaloids were obtained from Albertisia cf. A. papuana Becc. (Menispermaceae). These are (−)-2,2′-bisnorphaeanthine (5), (+)-pangkoramine (7), (+)-pangkorimine (9), and (+)-2′-norcocsuline (14). They are accompanied by the known (+)-daphnoline (2), which is the main alkaloid, and by seven known dimers with one, two, or three ether bridges.
Synthesis, 1H, 13C, and 29Si nuclear magnetic resonance spectra and crystal structure of trans-1,4-diphenyldecamethylcyclohexasilane
Authors: Kumar Kanta , Litt Morton H. , Chadha Raj K. , Drake John E.
Published: May 2006

The coupling reaction between PhMeSiCl2 and Me2SiCl2 in the presence of Na/K alloy resulted in a variety of phenylated permethylcyclohexasilanes of which only trans-1,4-Ph2Me10Si6 could be obtained in pure form by repeated recrystallizations. It was studied by means of nmr (1H, 13C, and 29Si) and X-ray crystallography. The crystals are monoclinic, P21/c with a = 10.105(6), b = 14.77(1), c = 9.973(6) Å, β = 94.08(5)°, V = 1485(2) Å3, and Z = 2 for 1922 unique "observed" reflections and the structure refined to an R index of 0.036. The molecule has site symmetry [Formula: see text] and the chair conformation of cyclohexane, with the two phenyl rings occupying the equatorial positions.
A 13C and 15N nuclear magnetic resonance study of solid ammonium thiocyanate
Authors: Dickson Ross M. , McKinnon Michael S. , Britten James F. , Wasylishen Roderick E.
Published: May 2006

The static 13C nmr powder pattern for solid ammonium thiocyanate is analyzed to obtain the 13C chemical shielding anisotropy, 321 ± 7 ppm, and the 13C–14N dipolar splitting, 1295 ± 25 Hz. Slow magic angle spinning 15N nmr experiments are analyzed to obtain a nitrogen chemical shielding anisotropy of 415 ± 15 ppm. The 13C–14N dipolar splitting leads to an effective C—N bond length of 1.19 ± 0.01 Å, in good agreement with the value of 1.176 Å reported from accurate X-ray and neutron crystallographic studies. In solid NH4NCS absolute values of the average shielding constants [Formula: see text] and ct[Formula: see text] are 52 and 34 ppm, respectively. Comparison of calculated and observed [Formula: see text] values indicates that intermolecular interactions decrease the 13C and 15N shielding constants by approximately 10 and 30 ppm, respectively.
Preparation of integrated chemical sensors using commercial VLSI technology
Authors: Glavina Paul G. , Harrison D. Jed
Published: May 2006

The fabrication of ion sensitive field effect transistors (ISFET) and microelectrode arrays for use as chemical sensors using a commercial CMOS fabrication process is described. The commercial technology is readily available through the Canadian Microelectronics Corporation; however, several of the recommended design rules must be ignored in preparing chemical sensors using this process. The ISFET devices show near theoretical response to K+ in aqueous solution (55 mV slope) when coated with a K+ sensitive membrane. An extended gate ion sensitive device is presented which offers advantages in encapsulation of ISFET sensors. The source-drain current of both devices show a linear response to log [Formula: see text] in contrast to ISFETs previously reported that have high internal lead resistances. Al and poly-Si microelectrode arrays are fabricated commercially and then Pt is electrodeposited on the microelectrodes. The resulting arrays show good cyclic voltammetric response to Fe(CN)64− and Ru(NH3)63+ and are relatively durable.
Extraction of alkali metal cations into polyester-based polyurethane foam using crown ether and picric acid
Authors: Khan A. S. , Baldwin W. G. , Chow A.
Published: May 2006

The distribution of alkali metal picrates between water and polyester-based polyurethane foam in the presence of dicyclohexyl-18-crown-6 was studied. The order of extraction coefficients of the alkali metals is governed by the ratio of the cation size to that of the crown ether, although the degree of extraction may depend on the nature of the organic phase. The extraction of alkali metals by polyurethane foam from an aqueous solution in the presence of crown ether and a bulky anion can be considered as an ion pair extraction of MCrA by an organic solvent.
An improved synthesis of 1,3-dihydro-1-methyl-5-phenyl-2H-pyrido[3,4-e]-1,4-diazepin-2-one via ortho-directed lithiation of 3-tert-butyl and 3-tert-butoxycarbonylaminopyridine
Authors: Fiakpui Charles Y. , Knaus Edward E.
Published: May 2006

The ortho-directed lithiation of 3-tert-butyl- or 3-tert-butoxycarbonylaminopyridines (3) with alkyllithiums and reaction with N,N-diethylbenzamide followed by acid hydrolysis gave 3-amino-4-benzoylpyridine (6) in good yield. Reaction of BTBO with the glycine derivatives 7a, b and then reaction with 6 afforded 3-alkoxycarbonylaminomethylcarbonylamino-4-benzoylpyridines 8a, b. Acid-catalyzed hydrolysis and cyclization of 8a, b yielded 9, which on methylation gave 1,3-dihydro-1-methyl-5-phenyl-2H-pyrido[3,4-e]-1,4-diazepin-2-one (10) in 36% overall yield from 3a.
Diisopropylethylamine eliminates dipeptide formation during the acylation of amino acids using benzoyl chloride and some alkyl chloroformates
Authors: Chen Francis M. F. , Benoiton N. Leo
Published: May 2006

Acylation of amino acids using benzoyl chloride in aqueous alkali leads to benzoylamino acids containing one percent of benzoyldipeptide. Use of diisopropylethylamine instead of sodium hydroxide as base eliminates the side reaction responsible for the contaminant. Ethoxycarbonylamino acids are advantageously prepared in the same manner using ethyl chloroformate or diethyl dicarbonate. The latter gives rise to some N-substituted dipeptide when used in aqueous alkali. The method is unsatisfactory for the benzyloxycarbonylation of amino acids. Use of 9-fluorenylmethyl chloroformate and diisopropylethylamine gives the pure derivative of leucine in moderate yield.
Chelated compounds and derivative of β-alkoxycarbonylalkyltin chlorides — 5-arylazo-8-quinolinolates, alizarinates, and thiocyanate: preparation and spectroscopic studies
Authors: Deb Barun Kanti , Ghosh Amiya Kanti
Published: May 2006

Complex formation with chelating ligands like 5-phenylazo-8-quinolinol, 5-(2I-carboxyphenylazo)-8-quinolinol, 1,2-dihydroxyanthraquinone (i.e., alizarin), and 1-nitroso-2-naphthol is due to nucleophilic attack on tin of the β-alkoxycarbonylalkyltin chlorides (a unique class of PVC stabilizer intermediates) with the subsequent elimination of hydrogen chloride. A number of complexes of the types R2SnL2, RSnL2Cl, R2SnLCl, R2Sn(LIHI)2, R2SnLII, and RSnLIICl (where R = CH3OCOCH2CH2—, C4H9OCOCH2CH2—, and CH3OCOCH(CH3)CH2—; LH = 5-phenylazo-8-quinolinol, 1-nitroso-2-naphthol; LIHHI = 5-(21-carboxyphenylazo)-8-quinolinol; and LIIH2 = 1,2-dihydroxyanthraquinone) and a thiocyanate derivative viz. (CH3OCOCH2CH2)2Sn(SCN)2 have been prepared. 5-Arylazo-8-quinolinols exhibit azo–hydrazone tautomeric equilibria but their complexes exist only in the azo form. β-Alkoxycarbonylethyltin alizarinates are somewhat different from other complexes. In these complexes two hydroxyl groups of alizarin have been utilised in complex formation, moreover, one of the two carbonyl groups of alizarin also remains involved in coordination to tin. In (CH3OCOCH2CH2)2Sn(SCN)2, the thiocyanate group is possibly linked to tin atom through nitrogen. All the complexes and the thiocyanate derivative have been characterised by elemental analyses, electronic, ir, and 1H nmr spectra. Possible structural features of the compounds are discussed.
Synthesis and characterization of transition metal complexes containing novel, unsymmetric tridentate organogallate ligands
Authors: Onyiriuka Emmanuel C. , Storr Alan
Published: May 2006

Two novel unsymmetric tridentate anionic organogallate ligands have been synthesized and their coordinating properties toward a number of transition metal carbonyl species, and toward the "NINO" moiety, have been investigated. The ligand [Me2Ga(N2C3H3)•O(C5H3N)CH2NMe2]−, La, has shown unusual behaviour in that it produces both the fac and mer octahedral isomers, LaM(CO)3, (M = Mn or Re), on reaction with Mn(CO)5Br and [Re(CO)4Cl]2, respectively. In addition, this ligand gives a stable Rh(III) addition product, LaRh(Me)(I)CO, on reaction of LaRh(CO) with Mel. The second ligand, [Me2Ga(N2C3H3)•O(C9H6N)]−, Lq, containing a quinolyl moiety in addition to a pyrazolyl group attached to dimethyl-gallium, displays more predictable behaviour in its coordinating properties.
Deuterium isotope effects on the 119Sn shielding constants and spin–spin coupling constants in stannane and the stannonium cation
Authors: Leighton Kevin L. , Wasylishen Roderick E.
Published: May 2006

Deuterium induced isotope effects on the 119Sn chemical shielding constants have been measured for stannane and the stannonium cation; they are found to be approximately −0.403 ppm/D and −0.05 ppm/D respectively. The 119Sn shifts in the series SnDnH4−n (n ≤ 4) deviate from additivity as predicted by Jameson and Osten. The primary and secondary isotope effects on Sn–H spin–spin coupling for stannane were obtained and are −2.8 Hz and −1.7 Hz respectively. The primary isotope effect for Sn–H spin–spin coupling for the stannonium cation was found to be −11.6 ± 7 Hz; an accurate value for the secondary isotope effect on the spin–spin coupling could not be obtained. The derivative of the 119Sn shielding constant and J (Sn,H) with respect to extensions in the equilibrium bond length have been calculated for stannane.
The characterisation and X-ray crystal structure of pentabromodiselenium hexafluoroarsenate, Se2Br5AsF6; some thermodynamic considerations and the nonexistence of Se2I5AsF6
Authors: Murchie Michael P. , Passmore Jack , White Peter S.
Published: May 2006

The crystal structure of Se2Br5AsF6 was determined by low-temperature X-ray diffraction methods. Single crystals of Se2Br5AsF6 are rhombohedral, space group R3 with a = 13.367(4) Å, c = 19.000(6) Å, V = 2940 Å3, and Z = 9. The structure was refined to final agreement indices of R = 0.087, Rw = 0.093 for 604 observed (I > 3σ(I)) reflections and 71 parameters. The structure consists of essentially discrete Se2Br5+ cations and AsF6− anions with some cation–anion interaction. The Se2Br5+ cation, of essentially C2h symmetry contains two trans SeBr2 units, linked by a bridging bromine atom. The two terminal selenium–bromine bond distances are 2.291(7) and 2.268(6) Å, of bond order 1, and the angle between them is 100.0(3)°. The bridging bromine atom lies at the inversion centre of the Se2Br5+ cation, with an Se—Br distance of 2.582(3) Å, corresponding to a bond order of about 0.5. The two angles between the bridging Se—Br and terminal Se—Br bonds are 97.4(1)° and 98.9(2)°. Se2Br5AsF6 decomposes slowly at room temperature and rapidly at 100 °C leading to the formation of SeBr3AsF6, SeBr4, and elemental selenium. It reacts with Br2 to give SeBr3AsF6 and SeBr4. Se2Br5AsF6 is prepared by the reaction of Se4(AsF6)2 and the appropriate quantity of Br2. The analogous reaction with I2 leads to I2SeSeSeSeI2(AsF6)2 and not Se2I5AsF6. These differences have been accounted for on the basis of estimates of the appropriate bond and crystal lattice energies. The 77Se nmr of SeBr3+ and Se2Br5+ in SO2 solution, and the Raman spectrum of SeBr4 are reported.
Arylphosphonic acids. I. Substituent effects on their first and second dissociations
Authors: Nagarajan K. , Shelly Kevin P. , Perkins R. R. , Stewart Ross
Published: May 2006

Thermodynamic pK1 and pK2 values of 36 arylphosphonic acids have been determined. The pK values of the meta and para compounds are correlated well by the σn parameter, suggesting that there is little conjugation between the phosphonic group and the aromatic ring; the ρ values of the first and second dissociations are 0.923 and 1.140, respectively. The —PO3H− group itself appears to be electron donating, contrary to earlier literature reports. The effect of ortho groups has been examined using multivariate analysis; the steric component of the proximity effect is acid weakening and has a larger effect on the second dissociation than on the first, presumably because a greater change in degree of solvation accompanies the second dissociation than the first.
Thioamide spectroscopy: long path length absorption and quantum chemical studies of thioformamide vapour, CHSNH2/CHSND2
Authors: Judge R. H. , Moule D. C. , Goddard J. D.
Published: May 2006

The 270 nm absorption spectra of thioformamide, CHSNH2 and CHSND2, have been photographically recorded under conditions of long path length (88 m) and moderate resolution (7.5 Å/mm). The absorption was assigned to the electron promotion, nS → π* (CS), and to the electronic transition, [Formula: see text]. The spectra proved to be complex, highly congested and somewhat diffuse which limited the extent of the vibrational assignments. Progressions in five members were observed in both CHSNH2/CHSND2 in intervals of 516/496 cm−1 which were assigned to ν10, the out-of-plane aldehyde wagging mode. It was concluded on Franck–Condon grounds that the [Formula: see text] molecule was non-planar at the aldehyde center. Structures and vibrational frequencies were calculated for the [Formula: see text] and the[Formula: see text] electronic states at the 3-21G* SCF level. The calculations confirmed that the lower state was strictly planar and predicted that both the aldehyde and amino groups were pyramidal in the upper electronic state.
The phosphorylation of chrysotile asbestos fibers with phosphorus oxychloride (POCl3): mechanism of reaction and chemical composition of the external coating
Authors: Khorami Jaleh , Lemieux Alain , Nadeau Denis
Published: May 2006

Magnesium hydroxide and silica, which are at the base of the chemical composition of chrysotile asbestos fibers, have been treated with phosphorus oxychloride vapors and compared to chrysotile asbestos treated similarly. Thermogravimetric, evolved gas analyses, and Fourier Transform infrared spectroscopy techniques were used to identify the compounds formed and (or) adsorbed on the surface of the minerals phosphorylated at room temperature and after a heat post-treatment at 300 °C. The results obtained show that the reaction of silica with phosphorus oxychloride can be considered negligible. However, the modifications induced on magnesium hydroxide and chrysotile asbestos fibers are similar. After the chemical treatment at room temperature, it was possible to identify the presence of hydrochloric acid, phosphorus oxychloride, magnesium chloride (nH2O), and acid orthophosphate salts. In comparison, the compounds formed after the 300°C heat post-treatment were only hydrated polyphosphate salts and magnesium chloride (nH2O). It is postulated that a polyphosphorus coating is formed at the surface of the chrysotile asbestos fibers when these are treated with phosphorus oxychloride at room temperature and then treated at 300 °C after the phosphorylation process.
Interaction between bromothymol blue and antipyrine in dichloromethane
Authors: Gainza Alberto Hernandez , Jimenez Luisa Puerta
Published: May 2006

Antipyrine (AT) reacts with bromothymol blue (BTB) in dichloromethane (DCM), forming an ion pair of 1:1 stoichiometry. Chemical equilibrium has been demonstrated and the formation constants of the ion pair at various temperatures have been calculated spectrophotometrically. The thermodynamic parameters of the reaction are ΔH0 = −6994 cal/mol, ΔS0 = −11.05 cal/K mol, and [Formula: see text].
Synthesis and characterization of Hg(II) complexes of Me3MCH2SeMe, (M = Si, Ge). Crystal structures of [HgX2(Me3SiCH2SeMe)]2, X = Cl, Br, I
Authors: Chadha Raj K. , Drake John E. , McManus Neil T. , Mislankar Anil
Published: May 2006

Complexes of the general formula [HgX2(Me3MCH2SeMe)]2, where M = Si, Ge; X = Cl, Br, I, have been prepared and characterized by 1H nuclear magnetic resonance and Raman spectroscopy. Crystal structures of [HgX2(Me3SiCH2SeMe)]2, where X = Cl, Br, and I (1, 2, and 3 respectively), show that they have centrosymmetric dinuclear structures. The crystals of 1 and 2 are monoclinic, while those of 3 are triclinic. For 1: P21/c, a = 14.235(11), b = 6.551(6), c = 14.211(9) Å, β = 117.33(5)°, Z = 2, and R = 0.0560. For 2: P21/c, a = 14.329(6), b = 6.695(2), c = 14.819(4) Å, β = 118.47(2)°, Z = 2, and R = 0.0540. For 3: [Formula: see text], a = 7.651(2), b = 8.387(2), c = 12.321(4) Å, α = 90.07(2), β = 91.80(2), γ = 116.02(2)°, Z = 1, and R = 0.0565. All three complexes show the expected pseudotetrahedral geometry about mercury. The stereochemical differences arise in the arrangement of the bulky trimethylsilylmethyl groups, which in the HgI2 adduct are rotated away from the centre of the molecule but which in the HgCl2 and HgBr2 adducts are turned towards the centre. These are the first dinuclear structures reported of HgBr2 and HgI2 adducts since it was demonstrated 46 years ago by Evans etal. that [HgBr2(AsBu3)]2 was present in [HgBr2(AsBu3)2•HgBr2].
13C nuclear magnetic resonance spectra in the solid state of 18-crown-6•NaNCS•H2O, some dicyclohexyl-18-crown-6 ethers, and their complexes with phenoxides and phenol
Authors: Buchanan G. W. , Khan M. Z. , Ripmeester J. A. , Bovenkamp J. W. , Rodrigue A.
Published: May 2006

High resolution 13C CPMAS spectra for three configurationally isomeric dicyclohexyl-18-crown-6 ethers and three complexes derived therefrom are presented. Spectra are consistent with conformationally locked crown ether structures at 298 K. Data are discussed in terms of the symmetry properties of the macrocycles and stereochemical effects on 13C chemical shifts in the solid phase. For the complex of 18-crown-6 with NaSCN and H2O, a single line is observed at 298 K. Temperature reduction removes the chemical shift averaging as the different torsional angles of the solid crown ether undergo distortions that become slow on the nuclear magnetic resonance timescale.
Préparation et détermination des configurations des dihydroxy-10,11 dihydro-10,11 quinidines 10(R) et 10(S), des métabolites de la quinidine
Authors: Jarreau François-Xavier , Koenig J. J. , Pays Michel , Leroyer Robert , Brisse François , Richer Jean-Claude
Published: May 2006

This paper describes the chemical preparation of the 10,11-dihydroxyquinidines, some of the metabolites of quinidine. The 10(R) and 10(S) isomers have been separated using the isopropylidene derivatives. The physical characteristics of each of these isomers have been determined and their respective structures have also been determined using 1H nuclear magnetic resonance at 400 MHz. On the basis of an X-ray diffraction structure determination, it has been shown that the main product, melting point 239 °C, is the 10(R) isomer. This product crystallizes with one molecule of water in the orthorhombic system with a = 8.756(2), b = 11.499(7), and c = 19.123(5) Å and space group P212121. The structure has been refined to a final value of R = 0.040 for 2039 observed reflections. [Journal translation]
Surfactant–cyclodextrin interactions by conductance measurements
Authors: Palepu Ramamurthy , Reinsborough Vincent C.
Published: May 2006

Conductance measurements were used to identify and to obtain association constants for the complexes formed between cyclodextrins (CD) with emphasis on β-cyclodextrin (βCD), and surfactants such as sodium dodecylsulfate (SDS) and tetradecyltrimethyl ammonium bromide. With both anionic and cationic surfactants, αCD forms predominantly a 2:1 CD/surfactant complex while with both βCD and γCD the main species is 1:1. γCD binds much less strongly with surfactants than both αCD and βCD. Cyclodextrins destroy micelles by complexing the surfactant monomers more strongly than they are bound in self-association.