An approach to the construction of the aromatic portions of naphthomycin and the rubradirins - nucleophilic additions to unsymmetrically substituted naphthoquinones

A Diels-Alder entry into the highly substituted naphthoquinones present in the rubradirins and naphthomycin is described.     

The magnesium bromide induced claisen condensation reaction of N-acylpyrazoles

N-Acylpyrazoles formed the 5-membered C=O-Mg-N-2 chelate complexes with magnesium bromide which afforded the Claisen condensation products by the action of tertiary amine through the corresponding enolate.     

On the lower excited states of the formyl radical HCO

Extensive ab initio Cl calculations were carried out on the lower four doublet states of HCO. The results are used in assigning hydrocarbon flame bands, the upper state of the A and B bands being the B²A′ and C²A″ states. These two states are characterized as bonding of H with the π-to-π^* state of CO.     

Determination of traces of vanadium with the catalytic maximum wave in differential pulse polarography

Summary A differential pulse-polarographic method has been studied for the determination of vanadium employing the catalytic maximum wave. A well-defined differential pulse polarographic peak is observed in the potential range from –0.2 to –0.7 V vs. SCE for vanadium(V) in 10 mmol 1^–1 NaCl containing 10 mmol 1^–1 acetic acid, 40 mmol 1^–1 pyrocatechol, and 2.5 mmol 1^–1 KBrO₃. The peak current is very large and proportional to the concentration of vanadium(V) between 1×10^–7 and 1×10^–6 mol 1^–1. The relative standard deviation at 0.5 mol l^–1 vanadium(V) was 2.06% (n=7). This method has been successfully applied to the determination of vanadium in standard materials such as pond sediment.

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Spurenbestimmung von Vanadium mit Hilfe der katalytischen Maximumsstufe in der Differential-Puls-Polarographie

Zusammenfassung Ein gut definierter differentialpuls-polarographischer Peak wurde für Vanadium(V) in 10 mmol/l NaCl-Lösung, die 10 mmol/l Essigsäure, 40 mmol/l Brenzcatechin und 2,5 mmol/l KBrO₃ enthielt, beobachtet (Potentialbereich –0,2 bis –0,7 V gegen SCE). Der Peakstrom ist sehr groß und die Vanadiumkonzentration im Bereich von 1×10^–7 bis 1×10^–6 mol/l proportional. Die relative Standardabweichung betrug 2,06% (n=7) bei 0,5 mol/l Vanadium(V). Das Verfahren wurde mit gutem Erfolg zur Vanadiumbestimmung in Standardproben (z.B. Teichsediment) eingesetzt.

     

Basis dependence of wave functions of the ground state and low-lying excited states of planar formaldehyde

By the use of three bases containing 3p STO 's possessing different diffuseness, the electronic structure of several excited states (valence- and Rydberg-type) of planar formaldehyde is investigated by limited CI calculations. The spatial extension of the valence-type state is independent of the bases, whereas a diffuse orbital is important in describing the Rydberg-type state. The natural orbital analysis shows that the Rydberg-type states can be described as an outer electron plus an electronic cloud representing the ionized state to which the Rydberg states converge.