Darstellung und Reaktionen des 3-Ethinyl-2,4-diformyl-pentandials

Preparation and physical and chemical properties of 3-ethinyl-2,4-diformyl-pentandial (3 a) and its salts are described.3 a contains 2 malonaldehyde groups. Starting from3 a, 4H-pyranes, 4H-dihydropyridines, dipyrazoles, diisoxazoles, bisdiazepines and vinamidine derivates are obtained.

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Zur Umsetzung des 3,4,5,6-Tetrahydro-6-hydroxy-4,4,6-trimethyl-1,3-thiazin-2-thions mit sekundären Aminen

Tetrahydro-6-hydroxy-trimethyl-1,3-thiazine-2-thione (1) reacts with secondary amines via the dialkylammonium-3-oxoalkyldithiocarbamate3, either via isothiocyanates6 to 4-dialkylaminodihydro-2(1H)-pyridinethiones7 or to dialkylammonium dithiocarbamates (13), depending on the amine used and the reaction conditions. Subsequently, 6-dialkylaminotetrahydro-1,3-thiazine-2-thiones11 or tetrahydro-6-mercapto-1,3-thiazine-2-thione10 are formed. On being heated to reflux,11 reacts to pyridinethione7 and 4-dialkylaminodihydrothiopyranthione19. With secondary amines only13 is formed from tetrahydro-6-hydroxytetramethyl-1,3-thiazine-2-thione20. The reaction of dihydrotrimethyl-1,3-thiazine-2-thione21 with secondary amines leads to N,N-dialkylthioureas16 or dialkylammonium thiocyanates17 and with dialkylformamides 4-dialkylaminodihydropyridinethiones7 are formed. Dihydrotetramethyl-1,3-thiazine-2-thione24 reacts neither with secondary amines nor with dialkylformamides.     

Polymerization of methacrylates. I. Polymerization reactivity of picryl methacrylate

The polymerization of picryl (PMA), 2,4-dinitrophenyl (2,4-DNMA),2,6-dinitrophenyl (2,6-DNMA), 2-methyl-4,6-dinitrophenyl (MDNMA), and 2,6-dimethylphenyl methacrylates (DMMA) was carried out in benzene at 60°C. PMA, 2,6-DNMA, and MDNMA did not undergo radical homopolymerization, while 2,4-DNMA and DMMA did. The results suggest that the growing radical readily attacks the oxygen atom of the nitro group at the 2 position of the terminal phenyl group due to the steric effect of the substituent at the 6 position, resulting in chain termination. PMA formed a charge-transfer complex with 2-naphthyl methacrylate (NMA). The stoichiometric composition of this complex was shown to be 1:1 molar complex. PMA was readily copolymerized with NMA. The amount of solvent affected the composition of the copolymer obtained at a given same mole fraction in feed. The results suggest that charge-transfer interaction between the ester groups affects the copolymerization mechanism.     

Beiträge zur Chemie der Pyrrolpigmente, 19. Mitt.: Die elektrochemische Oxidation von Pyrromethenonen und Pyrromethenen (Gallenpigment-Partialstrukturen)

The electrochemical oxidation of arylmethylene-pyrrolinones, pyrromethenones and pyrromethenes as representative bile pigment partial structure models was investigated by means of a rotating disc platinum electrode using acetonitrile as the solvent. Two different oxidation reactions were found. The first reaction being a reversible one-electron oxidation with compounds of the arylmethylene-pyrrolinone series and pyrromethenones which are unsubstituted in position 5 of the pyrrole ring. A two step reaction (the first one reversible, the second irreversible) on the other hand was found to be typical for pyrromethenones bearing a methyl group in this position.Through protonation the first step is at a higher potential, whereas the second one is lowered and becomes reversible. The resulting oxidation pattern can be interpreted analogous to the oxidation of hydroquinones in aprotic solvents.The geometrical isomers of a pyrromethenone were oxidized at appr. the same potential, but there is a strong dependence of the potential of the first oxidation step on the substitution: a higher degree of alkylation favours oxidation by lowering the oxidation potential.

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N-Monobromamide: Darstellung durch Bromierung mit „Dibromisocyanursäure”, Eigenschaften

By reaction of primary carboxamides with “dibromoisocyanuric acid” (DBI) N-monobromoamides can be readily obtained as well as the N,N-dibromoamides described in an earlier paper¹. Reactions, some of them new, and properties of these compounds are described and compared with those of the N,N-dibromoamides. Like other compounds bearing the NHBr group^{2, 3} the N-monobromocarboxamides disproportionate at room temperature according to: 2 RCONHBr ? ? RCONH₂+RCONBr₂. For CH₃CONHBr the equilibrium constant was found to beK=0.02. In aqueous solution they behave as weak acids. The dissociation constants of eight compounds [R=?CH₃, ?C₂H₅, ?CH₂Cl, ?CHCl₂, ?CCl₃, ?CF₃, ?C(CH₃)₃ and ?C₆H₅] were measured: they differ from those of the corresponding carboxylic acids by about three powers of ten.     

Zum Mechanismus der Hydrogenolyse aromatisch gebundenen Halogens

The selective chlorination of a m/p-xylene mixture, followed by distillation of the unreacted p-xylene, leaves a residue containing up to 90% of monochlorinated m-xylenes. m-Xylene is recovered from the latter by heterogeneous catalytic hydrogenolysis in the gas-phase. It was found that the hydrogenolysis on certain noble metal catalysts proceeds according to an ionic reaction mechanism at temperatures below a definite temperature range. At temperatures above this range hydrogenolysis follows a radical reaction mechanism.     

Cu(I) catalyst in DMF: an efficient catalytic system for the synthesis of furans from 2-(1-alkynyl)-2-alken-1-ones

The cyclization of 2-(1-alkynyl)-2-alken-1-ones 1 proceeded very smoothly in the presence of alcohols 2 with a catalytic amount of Cu(I)Br in DMF at 80 degrees C, leading to the formation of highly substituted furans 3. The catalytic system reported herein is easy to handle, compared to the previously known system wherein the reaction between 1 and 2 needed to use moisture sensitive gold(III) chloride.     

Metallchelate mit Acetophenon-Benzoylhydrazon und Acetophenon-Salicoylhydrazon

The stoichiometry and structure of acetophenone benzoylhydrazone and acetophenone salicoylhydrazone chelates with some divalent metal ions are studied by conductometric titration and visible and infra-red absorption spectrophotometry. The results are supported by analysis of the solid complexes. The infra-red study revealed that coordination occurs through C=O and C=N groups. The shift in the C=O and C=N bands is utilised for the determination of bond lengths.     

Zur Kenntnis der thermischen Zersetzung von Ammoniumhexafluoroscandat,-titanat,-vanadat und-chromat

Thermal analysis supported by kinetic calculations was applied exhaustively to these compounds. Under dynamic conditions, tetrafluorometallates(III), which as intermediates, could not be isolated, for the first three compounds. In each case, the final step was the pure metal(III) fluoride. Ammonium hexafluorochromate(III) decomposed directly to the pure chromium(III) fluoride. The decomposition rate of all compounds slowed down towards the end, probably for kinetic reasons. Polymorphic transitions of ammonium hexafluorotitanate(III) were observed at 35 and 100°C. Ammoniumhexafluoroscandate(III) underwent polymorphic transition at 47°C. The decomposition patterns for all these compounds were similar. Conditions for the preparation of pure ammonium tetrafluorometallates(III) of Sc, Ti and V are described.     

Untersuchungen zur 3-Phononenabsorption in partiell kristallinen Polymeren

Zusammenfassung In dieser Arbeit wird die Dreiphononenabsorption in Polymeren, die den Hauptanteil an den dielektrischen Verlusten im Millimeterwellengebiet stellt, theoretisch und experimentell untersucht. Aus der Störungsrechnung bis zur 2. Ordnung wird die Temperaturabhängigkeit der Absorption abgeschätzt. Damit ist eine befriedigende Deutung des gesamten Temperaturverlaufs der dielektrischen Verlust-Kurven möglich. Im Hochtemperaturbereich läßt sich die Mehrphononenabsorption eindeutig gegenüber restlichen Relaxationsprozessen abgrenzen. Im Tieftemperaturgebiet konnte erstmals auch für das Millimeterwellengebiet ein temperaturunabhängiger Bestandteil fehlordnungsinduzierter Einphononenabsorption nachgewiesen werden. Im Übergangsbereich durchlaufen die Absorptionskurven einen Wendepunkt bei einer charakteristischen TemperaturT ₀, die dem Schwerpunkt der am Absorptionsprozeß beteiligten Phononenfrequenzen entspricht. Daraus konnten in Übereinstimmung mit dem Experiment die Frequenzen der niedrigsten optisch aktiven Phononen für die verschiedenen Polymeren abgeschätzt werden.

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Summary The 3-phonon absorption in polymers, which gives the main contribution to their dielectric loss in the microwave region, is theoretically and experimentally investigated. Perturbation theory up to the second order is used for the evaluation of its temperature dependence. The theoretical results allow an interpretation of the total absorption-temperature-curves: In the high temperature region 3-phonon absorption can be distinguished from residual relaxation losses (above the glass temperature). In the low temperature region the existence of a low frequency tail of temperature independent disorderinduced one-phonon absorption became evident. At intermediate temperatures (50–150°K) the curves show an inflexion point or plateau at a characteristic temperatureT ₀, which according toT ₀= ⁰, corresponds to the frequencies of those phonons, that mainly contribute to the multiphonon absorption. The plateau gives, in good agreement with the experiment, the frequencies of the lowest optically active phonons in the various polymers.

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Mit 6 Abbildungen in 8 Einzeldarstellungen

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Vorgetragen auf der Arbeitssitzung des Fachausschusses Physik der Hochpolymeren in der Frühjahrstagung 1970 des Regionalverbandes Hessen-Mittelrhein-Saar der Deutschen Physikalischen Gesellschaft in Darmstadt, 10.–13. März 1970.