CIDNP-Effekte bei Photolyse und Thermolyse von substituierten Phenyldiazoniumsalzen

The existence of radical pairs during the photolysis and the thermolysis of substituted benzenediazonium tetrafluoroborates and hydroquinone in acetonitrile is shown by means of CIDNP. The reaction is assumed to occur via a one-electron-step to form first a radical pair consisting of phenyldiazene and p-benzosemiquinone. This radical pair is able to lose nitrogen either by photolysis or thermolysis and can lead either to a disproportionation or to various recombinations.     

Zum Problem der Michael-Addition an Cumarin

Zusammenfassung DieMichaeladdition von Cyanacetamid bzw. Malonsäuredinitril an Cumarin wird einer kritischen Betrachtung unterzogen. Die bisher angenommenen Strukturen eines 3,4-Dihydro-4-cyanacetamid-cumarins¹ (1) und 3,4-Dihydro-4-cyanessigsäureamidin-cumarins sind mit den UV- und IR-Spektren dieser Verbindungen nicht verträglich. Es wird ein für beide Fälle gültiger Reaktionsmechanismus vorgeschlagen, der zum 3-Cyan-3,4-dihydro-4-acetamid-cumarin (7) und 2-Amino-3-cyan-4-acetamid-4H-1-benzopyran (10) bzw. dessen tautomerer Iminoform (9) führt. Beide Strukturen zeigen völlige Übereinstimmung mit den spektralen Daten sowie mit den bekannten Abbaureaktionen.

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The structures of 3,4-dihydro-4-cyanoacetamide-coumarin (1) and 3,4-dihydro-4-cyanoacetamidine-coumarin, obtained by Michael-addition of cyanoacetamide and malononitrile resp. to coumarin are reinvestigated, because there is no agreement with their u.v. and infra-red spectra. A new mechanism is proposed which leads to 3-cyano-3,4-dihydro-4-acetamido-coumarin (7) and 2-amino-3-cyano-4-acetamido-4H-1-benzopyran (10) or its tautomeric imino-form9 resp.

     

Synthesen mit Nitrilen, 20. Mitt.: Untersuchungen über den Farbstoff aus Acenaphthenchinon und Malonitril

Zusammenfassung Malonitril und Acenaphthenchinon reagieren bei Anwesenheit von Basen zum blau gefärbten 6b-Hydroxy-8-imino-7,8-dihydro-6bH-cyclopenta [a]acenaphthylen-7,7,9-tricarbonsäurenitril (5). Kondensation mit Acenaphthenon führt zum 1-Dicyanmethylen-acenaphthen (7) bzw. zum 8-Amino-acenaphtho-[2,1—j]fluoranthen-7-carbonsäurenitril (9).

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The reaction of malononitrile and acenaphthenequinone in the presence of bases yields a blue compound, 6b-hydroxy-8-imino-7, 8-dihydro-6bH-cyclopenta[a]acenaphthylene-7,7,9-tricarbonitrile (5). Condensation with acenaphtenone gives 1-dicyanomethyleneacenaphtene (7) and 8-aminoacenaphtho[2,1—j]fluoranthene-7-carbonitrile (9), resp.

     

Untersuchungen zur Temperaturabhängigkeit charakteristischer IR-Absorptionen, 1. Mitt.: Temperatureffekt bei Carbonsäuren und bei anderen wasser-stoffbrückenbildenden Systemen

Zusammenfassung Die Temperaturabhängigkeit der Assoziation von Carbonsäuren und anderen wasserstoffbrückenbildenden Systemen wird durch IR-spektroskopische Methoden aufgezeigt.

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The temperature dependence of the dimerisation of carboxylic acids and other hydrogen bonded systems has been studied by infrared spectroscopic methods.

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Mit 5 Abbildungen     

Mesoionische Sechsringheterocyclen,XVI Syntheses von 2 a, 5 a-Diaza-acenaphthylen Mesoionen

Reaction of 7-azaindole with activated malonates (1) results in the formation of the tricyclic mesoionic diaza-acenaphthylene compounds2. Hydrogenation of2a with platin as catalyst leads to the saturated betaine4. The structure assignment was established by¹H-¹³C-NMR shift correlation and decoupling experiments.     

NMR-spektroskpische Untersuchungen an mehrfach substituierten β-Lactamen

Zusammenfassung Es wird durch kernresonanzspektroskopische Untersuchungen an mehrfach substituierten -Lactamen aufgezeigt, daß diese Verbindungen, im Gegensatz zur bisherigen Annahme, in vier isomeren Formen vorliegen.

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NMR-Spectroscopic investigation of -lactams bearing several substituents

It has been shown by means of NMR-spectroscopy that substituted -lactams exist in four isomeric forms, in contrast to previous assumptions.

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Herrn Prof. Dr.H. Nowotny, Vorstand des Institutes für Physikalische Chemie der Universität Wien, gewidmet.     

Multi-laboratory study of the analysis and kinetics of stanozolol and its metabolites in treated calves.

The European Union banned the use of anabolic steroids for cattle fattening in 1988. Analytical techniques able to detect trace amounts of the parent drugs and their metabolites are mandatory for the control of abuse. Stanozolol (Stan) is an anabolic steroid that is often found in injection sites and cocktails. However, it has never been detected in tissues (kidney fat, meat) or excreta (urine, faeces) taken during regulatory inspection. The difference between the structure of Stan and the other steroids (a pyrazole ring fused to the androstane ring system) is probably the cause of this phenomenon. In the multi-laboratory study described here, veal calves were treated with intramuscular doses of Stan. In the excreta of these calves the presence, absence and/or concentration of Stan and of its major metabolites 16 beta-hydroxystanozolol and 3'-hydroxystanozolol were determined. For the determination of these analytes the different laboratories used different extraction and clean-up procedures and also evaluated different analytical techniques such as GC-MS (negative chemical ionization) and LC-MS-MS. The aim of this investigation was to explore which analyte should be validated for veterinary inspection purposes.     

Zum Problem des Phenolphthaleins

Zusammenfassung Kernrescnanzspektroskopische Untersuchungen bestätigen das Vorliegen dreier verschiedener Formen des Phenolphthaleins im alkalischen Medium.

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The phenolphthalein problem

A nuclear magnetic resonance investigation confirms the existence of three different phenolphthalein anions in aqueous alkali.

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Mit 1 Abbildung     

Ein Beitrag zur Chemie des 2,3-Dihydro-3-oxo-benzo[b]thiophen-1,1-dioxids Synthesen mit Nitrilen, 86. Mitt.

Summary 2,3-Dihydro-3-oxo-benzo[b]thiophen-1,1-dioxide (1) reacts as CH-acidic component with amidines of orthoesters and anilines resp. to give the anilinomethylene derivates3, 4, and5. With triethyl orthoformiate the hydroxymethylene-compound7 is obtained. Anilino- and phenylhydrazino derivates8 and9 prove the carbonyl activity of1, azo-coupling leads to10, whereas treatment of1 with sulfur and malononitrile yields the benzo[b]thieno[2,3-d]thiophenes11. Introduction of substituents with active NH-functions in position 2 of the dicyanomethylene-product2, such as azocoupling, reaction with phenyl isocyanate and formation of enamines, leads to ring closure reactions between a nitrile and the NH-group. Thereby the phenyl-benzo[4,5]thieno[2,3-c]pyridazines12, the phenyl-1H-benzo[4,5]thieno[2,3-c]pyridines13 and the phenylamino-benzo[4,5]thieno[2,3-c]pyridines14 are obtained.¹³C and¹⁵N-NMR spectroscopy was used as proof of the ring closure reactions.

     

New nonlinear mechanisms of midlatitude atmospheric low-frequency variability

This paper studies the dynamical mechanisms potentially involved in the so-called atmospheric low-frequency variability, occurring at midlatitudes in the Northern Hemisphere. This phenomenon is characterised by recurrent non-propagating and temporally persistent flow patterns, with typical spatial and temporal scales of 6000-10 000 km and 10-50 days, respectively.We study a low-order model derived from the 2-layer shallow-water equations on a β-plane channel. The main ingredients of the low-order model are a zonal flow, a planetary scale wave, orography, and a baroclinic-like forcing.A systematic analysis of the dynamics of the low-order model is performed using techniques and concepts from dynamical systems theory. Orography height (h₀) and magnitude of zonal wind forcing (U₀) are used as control parameters to study the bifurcations of equilibria and periodic orbits. Along two curves of Hopf bifurcations an equilibrium loses stability () and gives birth to two distinct families of periodic orbits. These periodic orbits bifurcate into strange attractors along three routes to chaos: period doubling cascades, breakdown of 2-tori by homo- and heteroclinic bifurcations, or intermittency ( and ).The observed attractors exhibit spatial and temporal low-frequency patterns comparing well with those observed in the atmosphere. For the periodic orbits have a period of about 10 days and patterns in the vorticity field propagate eastward. For , the period is longer (30-60 days) and patterns in the vorticity field are non-propagating. The dynamics on the strange attractors are associated with low-frequency variability: the vorticity fields show weakening and strengthening of non-propagating planetary waves on time scales of 10-200 days. The spatio-temporal characteristics are “inherited” (by intermittency) from the two families of periodic orbits and are detected in a relatively large region of the parameter plane. This scenario provides a characterisation of low-frequency variability in terms of intermittency due to bifurcations of waves.