Valence electronic structure of CH3Br and CH3I: Electron momentum distributions and separation energies

Bromomethane (CH₃Br) and iodomethane (CH₃I) have been studied by binary (e,2e) coincidence spectroscopy at 1200 eV using non-coplanar symmetric kinematics. Separation energy spectra have been determined in the energy range up to 47 eV at azimuthal angles of 0° and 8° for CH₃Br and 0° and 6° for CH₃I. The separation energy spectra and the electron momentum distributions measured for each of the valence orbitals are compared with theoretical predictions employing SCF wavefunctions and outer valence type and extended 2 ph-TDA Green function calculations. Electron density and momentum density maps have been calculated for all the valence orbitals using the SCF wavefunctions, and they are used to explain trends and contrasts in the electronic structure and bonding properties of these halomethanes in both position and momentum space.     

Conformational analysis—131: A molecular mechanics treatment of phosphines

The molecular mechanics method (1973 force field) has been extended to include the general class of phosphaalkanes. Structural data on simple molecules were fit well, and equilibria between conformations can be calculated in general in agreement with experiment, in sofar as experimental data are known. Phosphacyclohexane and a few simple derivatives have been studied in some detail. It is concluded that the force field developed is adequate for the prediction of structures and energy differences, but it is not possible to calculate heats of formation, due to the lack of experimental data.     

Corrosion measurements by potential-step chronoamperometry

A solid-state computer-controlled system has been developed for the measurement of corrosion currents under potentiostatic anodic conditions. The system applies a potential step and measures the resulting current for a variable number of cycles. Data are stored and manipulated by the computer. Tests show that corrosion behaviour of metals in various environments can be evaluated.     

Nucleation in premicellar aggregation

The role of a nucleating agent (cholesterol) in the premicellar aggregation of sodium lauryl sulfate (SLS), cetyltrimethylammonium bromide, Triton X-405 and Brij 35 has been investigated. The I(1)/I(3) ratios of pyrene in the solutions indicate that SLS is strongly nucleated by cholesterol, but the other detergents appear to be so to a lesser extent. However, quenching studies show that premicellar Brij 35 also forms nucleated aggregates that protect the probe from the quencher. Energy transfer data with Triton X-405 suggest that such aggregates have a more open structure than self-assembling ones and are more accessible to water.     

13C- and 1H-NMR. Studies on the Configuration of Tricarbonyliron Complexes of Oxa- and Aza[4.4.3]propellanes

The configurations of a series of mono- and bis-Fe(CO)₃ complexes of 12-oxa[4.4.3]-propella-2,4,7,9-tetraene ( 1 ) and of 11,13-dioxo-12-methyl-12-aza[4.4.3]propella-2,4,7,9-tetraene ( 7 ) as well as of a trienic aza-propellane complex have been studied in solution by ₁₃C- and ₁H-NMR. spectroscopy. Praseodymium-induced ₁₃C-shifts of the metalcarbonyl carbon atoms and of the central carbon atom of the complexed diene systems are particularly sensitive and useful to prove exo- or endo-configuration of the tricarbonyliron ligand. In addition, H,H- and C,H-coupling constants of the complexes and parent compounds are reported and discussed.     

Propellanes. Part LXXX. Baeyer-Villiger Oxidation of [4.3.3]Propellane-8,11-dione

Oxidation of the title compound with m-chloroperbenzoic acid affords a keto-lactone, two bis-lactones and a bis-spirolactone, in varying amounts depending upon the reaction conditions. The structures were established by means of X-ray diffraction, ¹H- and ¹³C-NMR spectroscopy.     

A proper account of core-polarization with pseudopotentials: single valence-electron alkali compounds

A polarization potential is incorporated into semi-empirical and Hartree-Fock adjusted pseudopotentials. For molecules, the pseudopotentials become geometry-dependent. The omission of this effect has been the reason for too smallR_e values in earlier semi-empirical work. Very accurate results are obtained for the dimer and hydride ions of alkali elements up to K.     

The synthesis of pyridine derivatives from 3-formylchromone

3-Formylchromone ( 1 ) reacts with active methylene derivatives to yield condensation products 2a-d, 10,11 and 12 . Treatment of 2a-d with ammonia or methylamine gives pyridines 3–6 . Alternatively, reaction of 1 with enamine derivatives yields pyrido compounds 15, 17, 19, 21, 23 and 28 in one step. Factors determining the formation and regiospecificity of the pyridine ring forming reactions are also discussed.     

Zur Kenntnis von Ba(MgZn)V2O8, BaMn2V2O8 und Ba1/2Sr1/2Ni2V2O8

On Ba(MgZn)V₂O₈, BaMn₂V₂O₈, and Ba_1/2Sr_1/2Ni₂V₂O₈ Ba(Mg, Zn)V₂O₈ (A), BaMn₂V₂O₈ (B) and Ba_1/2Sr_1/2Ni₂V₂O₈ (C) were prepared by solid state reactions (A and B) and crystallization from a melt (C) respectively. (A? C) crystallize in the space group: D-I4₁/acd, Nr. 142. [Lattice constants (A): a = 12.4524(57) Å, c = 8.4408(36) Å; (B): a = 12.5563(14) Å, c = 8.5942(9) Å; (C): a = 12.2248(20) Å, c = 8.3245(15) Å]. (A), (B) and (C) are isotypic to SrNi₂V₂O₈ but showing higher symmetry.