The chemistry and the sterechemistry of Poly(N-Alkyliminoalanes: XIII. The crystal and molecular structure of the hexamers (ClAlN-i-Pr)6 and (Me0.83H0.17AlN-i-Pr)6MeAlN-i-Pr)6

The crystall and molecular structures of (ClAlN-i-Pr)₆ (I), and of (Me_0.83H_0.17AlN-i-Pr)₆(MeAlN-i-Pr)₆ have been determined by single crystal three-dimensional X-ray analysis. Block-matrix least-squares refinements led to conventional R factor of 0.039 for I and 0.037 for II. The compounds are isostructural, as the cage molecules consist of a prismatic hexagonal framework, (AlN)₆, similar to that observed for the parent hydrogenated analogue (HAlN-i-Pr)₆.Some differences in bond distances and angles are discussed, in connection with the different Al-bonded substituents. Crystal data: I, trigonal space group R$\text{3}$; a = 17.083(2), c = 9.652(1); Z = 3; D_c 1.46 g cm^?3; II, trigonal space group R$\text{3}$, a = 17.378(3), c = 9.706(3) »; Z = 3; D_c 1.15 g cm^?3.     

Improvements on radiochemical method for the determination of Am and Cm in typical waste streams from nuclear power plants

The determination of Am and Cm in typical waste streams from nuclear power plants using anion exchange chromatography has some drawbacks like the contamination by Pu and Po. This improved procedure solves these problems, and it has been applied with success to the analysis of Am and Cm in nuclear waste samples: ion exchange resins, ion exchange resins solidified with cement and evaporator concentrates.     

Energetic and topological analysis of the reaction of Mo and Mo2 with NH3, C2H2, and C2H4 molecules

The Density functional theory has been applied to characterize the structural features of Mo(1,2)-NH(3),-C(2)H(4), and -C(2)H(2) compounds. Coordination modes, geometrical structures, and binding energies have been calculated for several spin multiplets. It has been shown that in contrast to the conserved spin cases (Mo(1,2)-NH(3)), the interaction between Mo (or Mo(2)) and C(2)H(4) (or C(2)H(2)) are the low-spin (Mo-C(2)H(4) and -C(2)H(2)) and high-spin (Mo(2)-C(2)H(4) and -C(2)H(2)) complexes. In the ground state of Mo(1,2)-C(2)H(4) and -C(2)H(2), the metal-center always reacts with the C-C center. The spontaneous formation of the global minima is found to be possible due to the crossing between the potential energy surfaces (ground and excited states with respect to the metallic center). The bonding characterization has been performed using the topological analysis of the Electron Localization Function. It has been shown that the most stable electronic structure for a pi-acceptor ligand correlates with a maximum charge transfer from the metal center to the C-C bond of the unsaturated hydrocarbons, resulting in the formation of two new basins located on the carbon atoms (away from hydrogen atoms) and the reduction of the number of attractors of the C-C basin. The interaction between Mo(1,2) and C(2)H(4) (or C(2)H(2)) should be considered as a chemical reaction, which causes the multiplicity change. Contrarily, there is no charge transfer between Mo(1,2) and NH(3), and the partners are bound by an electrostatic interaction.     

Determination of four nitroimidazole residues in poultry meat by liquid chromatography-mass spectrometry

A multi-residue liquid chromatography-mass spectrometry (LC-MS) assay method is described for the determination of four nitroimidazoles in poultry muscle. The extraction procedure is based on liquid-liquid extraction with ethyl acetate followed by an evaporation step. A deuterated internal standard is used. The LC separation was made on a C18 bonded silica column with an aqueous formic acid (0.2%) solution-methanol-acetonitrile (81:13:6) mobile phase. Following electrospray ionization, the protonated molecular ion [M+H]+ is obtained for each compound. Monitoring several ions for each nitroimidazole provides the specificity required for confirmatory assay. Validation of the method was performed to estimate linearity, intra-day and inter-day repeatability, accuracy and detection limit. The present method is capable of identifying nitroimidazole residues in muscle at levels below 5 microg/kg.     

Synthesis of 2-amino-3-hydroxy- and of 2,3-diamino-3H-1,4-benzodiazepines

A new synthesis of 7-chloro-2,3-diamino-5-phenyl-3H-1,4-benzodiazepines is described, which allows for the preparation of compounds bearing the same or different substituents at the 2 and 3 positions, starting from 2-amino-7-chloro-3-hydroxy-5-phenyl-3H-1,4-benzodiazepines.     

A molecular orbital study of lithium ion association with bases. I. The carbonyl bases R2CO

Ab initio SCF calculations have been performed to determine the relative lithium ion affinities of the carbonyl bases R₂CO and the structures of the complexes R₂COLi⁺. The predicted order of lithium ion affinity for the bases R₂CO with respect to R is NH₂ > CH₃ > OH> H> F. Except for (OH)₂COLi⁺ which has C_a, symmetry, the complexes R₂COLi⁺ have C_2v symmetry, with the lithium ion located on the symmetry axis near the oxygen. The major structural changes in the intramolecular coordinates of the bases which occur upon lithium ion complexation include an increase in the carbonyl C---O bond length, a decrease in the length of the bond from the carbonyl carbon to the substituent atom X, and an increase in the X---C---X angle at the carbonyl carbon. The energetic, structural, and electronic properties of the complexes indicate that the interaction between the lithium ion and a carbonyl base is predominantly an ion-dipole attraction rather than a covalent interaction.     

Chronocoulometric study of the electrochemistry of Prussian blue

During the electrochemical oxidation of Prussian blue (PB) to Prussian yellow (PY), an electrocatalytic oxygen production proceeds at the electrode when aqueous electrolyte solutions are used. The formed oxygen is scavenged by the PY, probably by absorption, and it is consumed during the electrochemical reduction of PY to PB by a heterogeneous chemical reaction of PB with oxygen to PY and hydrogen peroxide. Because of this catalytic regeneration of PY, it is impossible to determine the amount of low-spin iron by chronocoulometry using a potential program in which PB is first oxidized to PY and then the charge is measured to reduce PY to PB. The latter charge is biased by the electrocatalytic PY regeneration.