Über die Michael-Reaktion mit Chinolacetaten, 3. Mitt.

Zusammenfassung Versuche, von o-Benzochinolacetaten ausgehend die hydroaromatischen (primären) Additionsprodukte derMichael-Reaktion zu erhalten, hatten bisher nur bei Ia und Ib mit Malonsäuredinitril Erfolg. Mit p-Benzochinolacetat VI gelingt die Darstellung der primären Additionsprodukte auch mit anderen Reaktionskomponenten, wie z. B. Malonsäurediäthylester. *** DIRECT SUPPORT *** A3615076 00007     

Viscosity effects on the thermal decomposition of bis(perfluoro-2-N-propoxypropionyl) peroxide in dense carbon dioxide and fluorinated solvents

The thermal decomposition of the free-radical initiator bis(perfluoro-2-N-propoxyprionyl) peroxide (BPPP) was studied in dense carbon dioxide and a series of fluorinated solvents. For the fluorinated solvents, the observed first-order decomposition rate constants, k(obs), increased with decreasing solvent viscosity, suggesting a single-bond decomposition mechanism. The k(obs) values are comparatively larger in dense carbon dioxide and similar to the "zero-viscosity" rate constants extrapolated from the decomposition kinetics in the fluorinated solvents. The decomposition activation parameters demonstrate a compensation behavior of the activation enthalpy with the activation entropy upon change in solvent viscosity. Comparison of the change in activation parameter values upon change in solvent viscosity for BPPP with two additional initiators, acetyl peroxide (AP) and trifluoroacetyl peroxide (TFAP), further suggests that carbon dioxide exerts a very minimal influence on the decomposition mechanism of these initiators through solvent-cage effects.     

Schwingungs- und Elektronenspektren der bindungsisomeren Hexakis(thiocyanato-isothiocyanato)-ruthenate(III)

Vibrational and Electronic Spectra of Bond-Isomeric Hexakis(thiocyanato-isothiocyanato)ruthenates(III) Well resolved IR, Raman, and Electronic spectra of the bond isomeric complexes (TBA)₃[Ru(NCS)_n(SCN)_6?n], n = 1–5, including the pairs of geometric isomers n = 2, 3, 4, are recorded at low temperatures (10 and 80 K). Characteristic vibrations of the N- or S-coordinated ambident ligand SCN^? occur as listed: ν_CS(N): 810–850, ν_CS(S): 690–710, δ_NCS: 450–490, δ_SCN: 420–450, ν_RuN: 300–350, ν_RuS: 270–295 cm^?1. The assignment of the complexes is based on stepwise increasing intensities of the ν_CS(N) modes with increasing number of N-coordinated ligands. Characteristic shifts and splittings in the spectra allow to distinguish the geometric bond isomers according to their different symmetries. Even the absorption spectra in the visible range show within the series of bond isomers and for the cis/trans pairs systematic alternations.     

Some ideas on minimization in ultra micro elemental analysis

Summary The problems encountered in the development of ultra micro methods or trace methods of elemental analysis are generally discussed. It is shown that process analyses (e.g. titrations) are preferable to meet needs of accuracy and sensitivity. Moreover, continuous systems of chemical process analyses seem to give a solution to the generally stated problems.

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Überlegungen zur Minimalisierung in der Ultramikroelementaranalyse

Zusammenfassung Die Probleme bei der Entwicklung von Ultramikro- oder Spurenmethoden in der Elementaranalyse werden allgemein diskutiert. Es wird gezeigt, daß Prozeßanalysen (z.B. Titrationen) den Anforderungen an Genauigkeit und Empfindlichkeit entsprechen. Darüber hinaus scheinen kontinuierliche Systeme chemischer Prozeßanalysen eine Lösung der aufgezeigten Probleme zu ermöglichen.

We thank the Czechoslovak Academy of Sciences, the Analytical Department of the Charles University of Prague and the High School for Chemical Technology of Pardubice for the possibility given to one of us (B.G.) to discuss with many colleagues in the SSR, the ideas presented in this article.     

The gas chromatography, thermal analysis and mass spectrometry of fluorinated lead β-diketonates Determination of traces of lead by the integrated ion-current technique

Preparative details for perfluoroalkanoylpivalylmethanes and their lead chelates are given. Thermal analysis, gas chromatography and mass spectral studies all indicate high thermal stability, but strong column interaction makes successful quantitative gas chromatography difficult. The integrated ion-current technique is applied to determine lead heptafluorobutanoylpivalylmethanate in the range 10^-9–10^-7 g of lead, but a lower detection limit of ca. 10^-14 g is indicated.     

Plasma chromatography of heroin and cocaine with mass-identified mobility spectra.

Plasma chromatography detects and identifies compounds in trace quantities at atmospheric pressure through characteristic positive and negative mobility spectra. To facilitate use of the technique to detect gas chromatographic effluents, a number of reference mobility spectra for different classes of compounds have been reported. Reference spectra for two more compounds, heroin and cocaine, are presented in this study. The primary ions found in these mobility spectra were determined to be M+, (M - H2)+, and (M - CH3CO2)+ for heroin and M+, (M - C6H5CO2)+ and (M - C6H5CO2 - CO2CH3)+ for cocaine using a directly interfaced plasma chromatograph-mass spectrometer. The identified ions agree closely with those predicted in the ion mobility spectra using mass-mobility correlation data coupled with chemical ionization mass spectrometry data. Also, an independent check demonstrating the reliability of reduced mobility values reported in earlier reference spectra was made.     

Syntheses, geometry optimization, and electronic structure of N-and C-substituted benzonaphthyridines

Synthesis of N-and C-substituted derivatives of benzo[h][1,6]naphthyridine, bearing 2-hydroxyethyl group has been made by quaternization reaction and by condensation of corresponding methylbenzonaphthyridines with formaldehyde. For six derivatives of isomeric benzo[c][1,5]-, benzo[h][1,6]-, and benzo[f][1,7]naphthyridines the ¹³C NMR spectra are discussed. For ten compounds the geometry was optimized with the AM1 and, in one case also with the ab initio 6–31G method; their effective charge values have also been calculated.     

The elastic scattering on jellium clusters

The following calculations are based on the local density approximation potential (LDA) of W. Ekardt for the spherical jellium-background model (SJBM). Taking into account the smooth shape of the potential, the WKB approximation was used to calculate the energy and angular dependence of the electron scattering cross-sections fo rsmall Na clusters. The number of phase shifts needed to describe the scattering in the range of energies <4.5 eV increases with the size of cluster. The calculated elastic electron scattering cross-sections for the Na clusters, corresponding to the shell closings (8, 20, 40), are exhibiting a pronounced peak structure, correlated with resonance states. The computed peaks of the angular dependences of the cross-sections on energy are shifted to small angles with increasing the cluster size. The absence of fragmentation at these small electron energies presents a challenge for the experimentalists.