Herstellung keramischer Pulver. II. Über die Bildung von Mg2TiO4, MgTiO3 und MgTi2O5 durch Hydrolyse von 2-Ethoxyethylaten

Preparation of Ceramic Powders. II. Mg₂TiO₄, MgTiO₃, and MgTi₂O₅ Formed by Hydrolysis of 2-Ethoxyethylates Solutions of 2-ethoxyethylates of magnesium and titanium in 2-ethoxyethanol submitted to hydrolysis, evaporation and heating of the residue up to 450°C allow to prepare Mg₂TiO₄, MgTiO₃, and MgTi₂O₅ in an amorphous state with smaller than 1% of volatile components. Highly dispersed powders showing an increased sintering activity are obtained as a result of recrystallization. Mg₂TiO₄ is formed as inverse spinel phase in a metastable state.     

Photocycloaddition of Cyclohex‐2‐enones to Penta‐1,2,4‐triene

Dihydrothiinone 9a undergoes photocycloaddition regioselectively to all three C?C bonds of penta‐1,2,4‐triene ( 10 ), the relative stabilities of the biradical intermediates determining the product distribution. In contrast, cyclohexenone 9b and dihydropyranone 9c afford more complex mixtures of bicyclo[4.2.0]octanones, which also turn out to be less stable on chromatographic workup, reflecting the higher strain due to the shorter bond lengths (C? O and C? C vs. C? S) in the six‐membered rings, respectively.     

Über einige neue Bispirane

We have obtained four new bispirane systems in which both spiroatoms are vicinal atoms in cyclopropane or cyclobutane rings and in which the heterocyclic component has the basic structure of 1,4-dioxep-2-ene. We have shown that from two possibilities (bispiran, propellan) the general reaction leads only to a bispiran system. To the bispiran2 exhibiting the highest hyperchromism we ascribed the bispirocoplanar conformation (Fig. 1).

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Mit 3 Abbildungen     

Identification of amber and imitations by near infrared reflection spectroscopy

Imitations of amber have been prepared since a long time, but the number of imitations is increasing since modern polymers are available. At present, many imitations are based on a few synthetic polymers and even experts have some problems in distinguishing between real and falsed amber without destruction of the material. IR-Spectroscopy or pyrolysis combined with gas chromatography/mass spectrometry are very efficient methods in identifying amber and imitations but these methods need a sample preparation. By means of near infrared reflection spectroscopy it is possible to identify amber and imitations without any sample preparation in a short time. Optimization of the method and the application are discussed.     

Inverse Pulspolarographie am h?ngenden Quecksilbertropfen

Zusammenfassung Die inverse Voltammetrie am hängenden Quecksilbertropfen mit pulspolarographischer Aufzeichnung der anodischen Auflösungsströme wird auf ihre Leistungsfähigkeit untersucht. 10^–9 M Lösungen von Cu, Pb, Cd, Zn können im Routinebetrieb analysiert werden. In Alkalisalzmatrices sind Direktbestimmungen der Schwermetalle im 10^–7 bis 10^–8%-Bereich möglich. Die Nachweisgrenze für Cd beträgt 5 · 10^–11 Mol/l. Die Empfindlichkeit der Methode wird mit derjenigen verwandter voltammetrischer Verfahren verglichen.

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Anodic stripping pulse polarography at the hanging mercury drop electrodeDetermination of Cu, Pb, Cd and Zn

The efficiency of anodic stripping pulse polarography at the H.M.D.E. is tested. In routine work the analysis of 10^–9 M solutions of Cu, Pb, Cd, Zn offers no difficulty. The determination of the elements in alkali salts in the 10^–7 to 10^–8% range is possible. The detection limit for Cd was found to be 5×10^–11 M. The sensitivity of the method was compared with those of related voltammetric techniques.

     

Synthesen mit Nitrilen, 29. Mitt.: Die linearen Kondensationsprodukte aus Dimethylaminophenylpropenon und Malonsäuredinitril

Zusammenfassung In unpolaren Lösungsmitteln kondensieren sich monomeres und dimeres Malonitril mit Dimethylamino-phenyl-propenon zu linearen Dienen bzw. Trienen. 2-Cyan-5-dimethylamino-3-phenyl-2,4-pentadienamid (4) kann als Zwischenprodukt für die Bildung von Pyridonen aus Enaminoketonen und Cyanacetamid aufgefaßt werden, da in saurem Medium die Cyclisierung zum 2-Oxo-4-phenyl-1,2-dihydro-pyridin-3-carbonitril bzw. dem Carbonsäureamid gelingt.

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Syntheses with nitriles, XXIX: The linear condensation products from dimethylaminophenyl propenone with malononitrile

Monomeric and dimeric malononitrile condense in nonpolar solvents with dimethylamino phenyl propenone to form linear dienes and trienes, resp. 2-Cyano-5-dimethylamino-3-phenyl-2,4-pentadienamide (4) represents an intermediate in the formation of pyridones from enamine ketones and cyanoacetamide. It is cyclised in acidic medium to 2-oxo-4-phenyl-1,2-dihydropyridine-3-carbonitrile (8) (or-3-carboxamide,9).

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Herrn Prof.O. Hromatka zum 65. Geburtstag gewidmet.     

Classification of Poincaré duality algebras over the rationals

The Poincaré duality algebras over Q play a key role in the rational homotopy classification of closed manifolds [3]. In this paper we give a way of classifying general Poincaré duality algebras and then specialize to the case of algebras which are generated by some homogeneous component and show how the classification reduces to the linear classification of certain homogeneous polynomials and exterior forms.     

Metallcarbonylkomplexe mit mehrzähnigen ringförmigen Liganden. I. Pentacarbonylkomplexe des s-Trithians und verwandter Verbindungen

Carbonyl Metal Compounds with Polydentate Cyclic Ligands. I. Pentacarbonyl Complexes of s-Trithiane and Related Compounds The complexes (RCHS)_nM(CO)₅ (R = H, CH₃, n = 3; R = H, n = 4; M = Cr^, Mo, W) were prepared from the tetrahydrofuran pentacarbonyl metal compounds and the respective ligands. The Cotton-Kraihanzel force constants of these complexes indicate the sulfur ligands to be slightly more basic than triphenylphosphine. The trimethyltrithiane complexes (R = CH₃, n = 3) exhibit rapid intramolecular exchange of the M(CO)₅-group along the three coordination centers of the ligand.     

Neutral and ionic aluminum,gallium, and indium compounds carrying two or three terminal ethynyl groups

The syntheses of the ionic compounds [Li(+).2 dioxane (2,6-iPr(2)C(6)H(3)N(SiMe(3))Al(C triplebond CSiMe(3))(3))(-)].0.75 dioxane (1), [(Li(+))(2).(dioxane)(7)](0.5) [2,6-iPr(2)C(6)H(3)N(SiMe(3))Ga(C triplebond CSiMe(3))(3)(-)].1.5 dioxane (2), and [(Li(+))(2).(dioxane)(7)](0.5) [2,6-iPr(2)C(6)H(3)N(SiMe(3))In(C triplebond CSiMe(3))(3)(-)].1.5 dioxane (3) by the reaction of the corresponding organo metal chloride with LiC triplebond CSiMe(3) are reported. The neutral ethynyl compounds Br-Al(C triplebond CtBu)(2).2 THF (4), Cl-Ga(C triplebond CtBu)(2).THF (5), Cl-In(C triplebond CtBu)(2).2 THF (6), Al(C triplebond CtBu)(3).C[N(Me)CMe](2) (7), Ga(C triplebond CtBu)(3).dioxane (8), and In(C triplebond CtBu)(3).NEt(3) (9) have been obtained in good yields from the reaction of AlBr(3), GaCl(3), and InCl(3) with LiC triplebond CtBu in the presence of a Lewis base. Compound 7 is the first heterocyclic carbene substituted ethynyl derivative. Aluminum and gallium compounds with three terminal ethynyl groups Al(C triplebond CPh)(3).NMe(3) (10) and Ga(C triplebond CPh)(3).NMe(3) (11) have been prepared by the reaction of AlH(3).NMe(3) or GaH(3).NMe(3) with three equivalents of phenylethyne. All the above-mentioned compounds have been structurally studied. In compound 1 the lithium ion is coordinated to the three terminal ethynyl groups, whereas in compounds 2 and 3 the lithium is coordinated to the solvent (dioxane). Compound 8 crystallizes as a coordination polymer with dioxane molecules bridging the individual gallium units.