Bestimmung von C-Methylgruppen in organischen Sauerstoffverbindungen durch Oxydation mit Chromsäure unter optimalen Bedingungen. I

Zusammenfassung Eine Reihe sauerstoffhaltiger Modellsubstanzen, die Methylgruppen am primären, sekundären oder doppelt gebundenen Kohlenstoffatom enthalten, wurden mit einem Gemisch von 2 T. 5-n Chromsäure und 1 T. konz. Schwefelsäure 45 Minuten bei 130° C oxydiert. Die entstandene Essigsäure wurde mit Wasserdampf abdestilliert und alkalimetrisch titriert. Die angeführten Reaktionsbedingungen können als optimal angesehen werden, da sie die größte oxydative Wirkung haben, bei der jedoch Essigsäure nicht weiter oxydiert wird. Der Abbau des Kohlenstoffskeletts verläuft schneller und vollständiger als bei der Methode vonKuhn undRoth. Die Essigsäureausbeute lag zwischen 0,70 und 0,95 Mol Essigsäure je C-Methylgruppe und wurde in Abhängigkeit von der Struktur der untersuchten Stoffe diskutiert.

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Determination of C-methyl groups in organic oxygen compounds through oxidation with chromic acid under optimal conditions

Summary A number of oxygen-containing model substances, which contained methyl groups on primary, secondary or doubly bound carbon atoms, were oxidized with a mixture of 2 parts of 5N chromic acid and 1 part of conc. sulfuric acid for 45 minutes ar 130° C. The resulting acetic acid was distilled off with steam and titrated alkametrically. The cited reaction conditions may be regarded as optimal, because they exert the greatest oxidative action, which however the acetic acid is not further oxidized. The degradation of the carbon skeleton proceeds faster and more completely than in the method ofKuhn andRoth. The yield of acetic acid lay between 0.70 and 0.95 mol acetic acid per C-methyl group and was discussed with respect to the structure of the investigated material.

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In dieser Mitteilung ist der erste Teil der Dissertationsarbeit von Frau Dipl.-Ing.B. Voláková inbegriffen.     

Hybridization in some macrocyclic polyacetylenes

The hybridization in several cyclic polyacetylene compounds has been calculated by the maximum overlap method, assuming planar and non-planar geometries of the molecules. In the planar configuration the hybrids describing the molecular skeleton deviate from the corresponding bond directions. We have a few “bent” bonds, but in contrast to the situation in small rings, here the deviation angles are negative, i.e., the hybrids point toward the inside of the ring. Non-planar structures in which acetylene groups are kept in a plane and CCH₂ or CH₂ groups are displaced out of the plane show less deviation from the bond directions of bent bonds. Furthermore, the deviation angles decrease with an increase in the out-of-plane displacement of methylene groups. Finally, when the angle of bending of the molecules approaches 50°, the deviation vanishes, predicting a puckered conformation for the molecules. Correlation between CC stretching vibration frequencies and the corresponding CC bond overlap is discussed.     

Anwendung derR-Wert-Methode auf isokonformere Cyclohexane: Kernsubstituierte [2.2]Metacyclophane

The applicability of theLambert-Buys-Criterion (R-Value-Method) is tested for the ten-membered ring of [2.2]metacyclophane. The torsional angles thus obtained from the vicinal proton spin coupling constants are in accordance with X-ray data and recent force field calculations. Consequently, further investigations could be performed regarding the changes of the basic geometry in substituted [2.2]metacyclophanes. Fourteen derivatives with different substituents and substitution patterns were studied and their conformational changes are discussed.

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Mit 7 Abbildungen

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VonH. Lehner auszugsweise vorgetragen am Organisch-Chemischen Institut der Reichsuniversität Gent, Belgien, am 27. Mai 1975.     

Peroxides of higher aliphatic ethers

The oxidation of higher aliphatic ethers with oxygen at 50° yields two peroxides as the main oxidation products for each ether, namely a dihydroperoxy-dialkyl ether and a dihydroperoxy-dialkyl peroxide. The mass spectra of these compounds are recorded and the main fragmentation pattern is discussed.     

Study of isotope exchange reactions by double labelling

This paper presents the method of double labelling in the study of the kinetics of homogeneous isotope exchange reactions. This method was tested by the determination of the Sn(II)−Sn(IV) exchange rate in hydrochloric acid medium. The system was labelled by the tracer^119mSn [initially in the Sn(IV) state]; when the isotope equilibrium was established, Sn(IV) was again labelled by tracer¹¹³Sn. The separation of Sn(II) and Sn(IV) in the given time of exchange was performed by the extraction of Sn(IV)-hydroxyquinolate into chloroform. The specific activities of the separated components were determined from the ratio of¹¹³Sn and^119mSn activities. The exchange rate was calculated from the time dependence of specific activities. The advantage and possibilities of the method of double labelling in the study of isotope exchange are discussed.     

Einfluß der Änderungen im Kristallgitter des Kaolinits auf die Eigenschaften seiner wäßrigen Dispersionen

Ohne Zusammenfassung     

Absorption properties of commercial lead chromates

For the cyanide determination in waste waters containing more than 2.5×10^?6 Mol of CN^?/l a conductometric method has been proposed. The sulphuric acid containing samples were distilled and the obtained HCN was passed into a 5×10^?4 Mol/l AgNO₃ solution, of which the conductivity was measured. The method offers the possibility of a precise observation of the completion of the HCN distillation and also the direct measurement of the cyanide concentration by the change of conductivity. The analysis time is about 40 min.     

Loss of light stabilizers from polypropylene

Loss of light stabilizers. related to 2-hydroxybenzophenone and 2-(2-hydroxyphenyl) benzotriazole. from isotactic polypropylene was measured over the range 60–120° and during storage at 25'. The light stabilizer content in polypropylene corresponded to that used in practice. The rate constants and the activation energy were calculated from the rate of loss. The influence of the structure of stabilizer on the rate of loss from polymer is discussed. The losses of stabilizers from polymer were compared with the vapour pressure of stabilizers and with the losses of stabilizers alone at 280. The rate of diffusion of stabilizers to the surface of polypropylene and the rate of even evaporation may cause a rapid diminution of stabilizer or undesirable accumulation on the polymer surface.     

Flow injection analysis : Part II. Ultrafast determination of phosphorus in plant material by continuous flow spectrophotometry

The effect of sample volume, tube length, tube diameter, peak height and sampling rate on the determination of phosphorus in acidic plant digests was investigated, and optimal conditions for the flow injection method are described. Sampling rates of 420 samples per hour were achieved without incurring problems from carryover of samples, and evidence was obtained that rates as high as 700 samples per hour are possible. The flow injection method was proved to be suitable for routine analyses and has obvious advantages over other automated or manual methods in sampling rate, simplicity of design and cost.     

Thia- und Dithia-cycloalkane und die Spaltung einiger gesättigter Heterocyclen mit Methyljodid

Zusammenfassung Die 8- und 9-gliedrigen Thia-cycloalkane und die dimeren 14-, 16- und 18-gliedrigen Ringsulfide wurden aus den entsprechenden ,-Dibromalkanen und Natriumsulfid in hochverdünnter alkoholischer Lösung erstmalig dargestellt und charakterisiert. Die Beweisführung für die Struktur der Monomeren erfolgte durch Ringspaltung mit Methyljodid und Identifizierung der entstandenen ,-Dijodalkane.Es wird gezeigt, daß die Ringspaltungsmethode mit Methyljodid unter Herauslösung der gesamten C-Kette auch auf gewisse gesättigte O- und N-Heterocyclen anwendbar ist. Tetrahydrofuran, 1,6-Epoxyhexan und 1,4-Dioxan sowie der Trimethyleniminring werden sämtlich in verschiedenem Ausmaß gespalten, nicht aber die Polymethylenimine mit 4 bis 7 C-Atomen. Im spirocyclischen N,N-Hexamethylen-piperidiniumjodid wird jedoch der 7-gliedrige Ring gesprengt. Piperazin wird nicht angegriffen, wohingegen die Ringhomologen, 1,5-Diaza-cyclooctan und 1,10-Diaza-cyclooctadecan der Spaltung zugänglich sind.Soweit untersucht, werden Benzoyl und p-Toluolsulfonyl am Stickstoff allgemein durch Methyl verdrängt, p-Nitrophenyl und o,p-Dinitrophenyl werden aber nicht ausgetauscht.Mit 4 Abbildungen.