Spontaneous dissolution of a single-wall carbon nanotube salt

Upon reduction with alkali metals, single-wall carbon nanotubes (SWNTS) are shown to form polyelectrolyte salts that are soluble in polar organic solvents without any sonication, use of surfactants, or functionalization whatsoever, thus forming true thermodynamically stable solutions of naked SWNTs.     

Sur le role fondamental du cation alcalin dans les reductions par les hydrures metalliques. Utilisation de coordinats macrocycliques—III : Etude de divers groupements fonctionnels reduits par LiAlH4

The reactions of the following functional groups with LiAlH₄ in Et₂O or DME were studied: ketone, aldehyde, carboxylic acid, amide, ester, nitrile, oxime, tosylate, epoxide, acyl chloride and alkyl bromide. All these reductions are catalysed by Li⁺, as shown by the use of a specific macrocyclic ligand allowing the reaction to be run free of Li⁺. Moreover, in the cases of acyl chloride and alkyl bromide the reaction (free of Li⁺) is catalysed by AlX₃ which is generated in situ. Several new mechanistic features are revealed for reductions by LiAlH₄.     

Isolation,purification, and further characterization of an L-phenylalanine oxidase fromMorganella morganii

A l-amino acid oxidase was isolated, purified, and characterized fromMorganella morganii 53187, a bacterium formerly known asProteus morganii. The synthesis of the enzyme by this bacterial strain was growth-associated and decreased sharply when the culture just reached the stationary phase. Based on this finding, the preparation of spheroplast by lysozyme-ethylene-diaminetetra-acetic acid (EDTA) disruption was carried out using the cells harvested during the exponential growth phase. Among several detergents tested, at the detergent-to-protein ratio of 2.5, 3-[(3-cholamidopropyl)dimethylammonio]-l-propane-sulfonate (CHAPS) was very effective in solubilizing most of the enzyme attached to the membranes while still preserving the activity of the solubilized enzyme. The resulting enzyme solution was then purified by hydrophobic interaction chromatography, followed by ion exchange chromatography and gel permeation. The enzyme was purified 19-fold with an overall recovery yield of 12%, corresponding to a specific activity of 252.2 U/mg protein. The selectivity of the purified enzyme toward l-amino acids was pH-dependent. At pH 6.35, the enzyme was very specific to l-leucine, whereas the selectivity for l-phenylalanine could be improved at pH 7.4. The enzyme exhibited a wide optimum temperature range 35–43?C and exhibited 1, l?dimethylferricinium reductase capability in the presence of l-phenylalanine.     

Theory of intermolecular interactions: The long range terms in the dipole–dipole,monopoles–dipole,and monopoles–bond polarizabilities approximations

The problem of evaluating the long range terms (electrostatic, polarization, dispersion) of the interaction energy between molecules at intermediate distances (i.e. distances of the order of magnitude of the molecular dimensions) is considered. Instead of being approximated by its dipole part, the exact interaction Hamiltonian is treated as proposed by Longuet-Higgins [11], i.e. the matrix elements are interpreted as electrostatic interactions between state and transition charge distributions. These charge distributions are approximated in a systematic way by sets of point charges (localized on the atoms) or sets of dipoles (localized on the bonds). The various contributions to the energy may then be expressed in terms of atomic net charges and bond polarizabilities. More refined approximations of the charge distributions could be used and correspondingly improved formulae could be derived: as an example, a formula for the σ-π dispersion energy is derived, where the σ charge distributions are approximated by bond transition dipoles (leading to σ bond polarizabilities in the final formula) while the π charge distributions are approximated by atomic charges.     

Direct Clay-Catalyzed Friedel-Crafts Arylation and Chlorination of the Hydrocarbon Adamantane

Multiple chlorinations and arylations at the tertiary positions of adamantane are promoted by FeCl₃-doped K10 montmorillonite in CCl₄ or in aromatic solvents. The process, remarkably easy to implement, can be tailored to selective formation of monosubstituted 1-adamantyl derivatives or 1,3-disubstituted adamantanes. The process achieves alkylation at the meta- and para-positions of toluene leading to a purely statistical distribution and displays no substrate specificity in competition experiments between toluene and benzene.     

Hydrazones and new Oximes of 4-Aminobicyclo[2.2.2]octanones and their Antiprotozoal Activities

Summary. 4-Aminobicyclo[2.2.2]octan-2-ones and -ols showed activity against the causative organisms of East African sleeping sickness and Malaria tropica. Several imino derivatives of the ketones were more active. Now hydrazono analogues and 3-hydroximino derivatives of the ketones and alcohols were synthesized. The structures of the obtained isomers were elucidated by NMR spectroscopy. A single phenylhydrazone exhibited quite good antitrypanosomal activity in the range of already known imino analogues.     

Hydrazones and new Oximes of 4-Aminobicyclo[2.2.2]octanones and their Antiprotozoal Activities

4-Aminobicyclo[2.2.2]octan-2-ones and -ols showed activity against the causative organisms of East African sleeping sickness and Malaria tropica. Several imino derivatives of the ketones were more active. Now hydrazono analogues and 3-hydroximino derivatives of the ketones and alcohols were synthesized. The structures of the obtained isomers were elucidated by NMR spectroscopy. A single phenylhydrazone exhibited quite good antitrypanosomal activity in the range of already known imino analogues.     

Kinetics of thermal decomposition of Co3O4 powder and single crystals

Kinetics of thermal decomposition in vacuum of Co₃O₄ powder as well as single crystals has been investigated. Discrepancies with the results of previous authors have been discussed. Decomposition of Co₃O₄ proceeds through formation of a compact layer of CoO and hence diffusion is the rate-limiting factor. The experimental curves α(t) be described for 0.05 < α < 0.85 using a modified Ginstling-Brounshtein equation: 1 ? 2α/3 ? (1 ? α)^2/3 = ktⁿ where the activation energy varies with the degree of decomposition.     

X-ray magnetic circular dichroism of Pseudomonas aeruginosa nickel(II) azurin

We show that X-ray magnetic circular dichroism (XMCD) can be employed to probe the oxidation states and other electronic structural features of nickel active sites in proteins. As a calibration standard, we have measured XMCD and X-ray absorption (XAS) spectra for the nickel(II) derivative of Pseudomonas aeruginosa azurin (NiAz). Our analysis of these spectra confirms that the electronic ground state of NiAz is high-spin (S = 1); we also find that the L(3)-centroid energy is 853.1(1) eV, the branching ratio is 0.722(4), and the magnetic moment is 1.9(4) mu(B). Density functional theory (DFT) calculations on model NiAz structures establish that orbitals 3d(x2-y2) and 3d(z2) are the two valence holes in the high-spin Ni(II) ground state, and in accord with the experimentally determined orbital magnetic moment, the DFT results also demonstrate that both holes are highly delocalized, with 3d(x2-y2) having much greater ligand character.     

Cascade polycyclization: exploration of a convergent route to access various tricyclic and tetracyclic products related to sterols

The expedient synthesis of tricyclic and tetracyclic compounds via a cascade polycyclization methodology is described. Nazarov substrates (II) containing two Michael acceptors and a cyclohexenone ester (I) underwent cycloaddition followed by intramolecular 1,4-addition to furnish, in a highly stereoselective manner, tricyclic and tetracyclic products (III). Such compounds are interesting intermediates for the synthesis of polycyclic natural and unnatural products.