133Xe release during post-irradiation annealing of uranium metal in the presence of a constant volume of air

The fractional release of¹³³Xe at different temperatures was studied as a function of time in the presence of an atmosphere of air during post-irradiation annealing of uranium metal. It was found that the relation between the fractional release and t^1/2 is irregular. There is an initial step in the annealing curves (at the temperature range of 400–710°C) which decreases by increasing temperature and totally disappears at the high temperature of 800–1000 °C. The other parts of the release curves are typical for¹³³Xe release from uranium metal. The initial step was found to be due to the surface oxidation of uranium metal.     

Composition of lipids of the grain of opaque-2 maize

It has been established that the change in the composition of the total lipids and the fall in the fatty acid content depend on the initial maize genotype. A decrease in the amount of unsaponifiable substances in the grain of mutants is accompanied by qualitative changes in the composition regardless of the nature of the genotype.Scientific-Research Institute of Biology Dnepropetrovsk State university. Translated from Khimiya Prirodnykh Soedinenii. No. 3. pp. 360–363. May–June, 1988.     

Inter-ring rotational potential of biphenyl and its effect on poly(p-phenylene)

Detailed ab initio studies have been done on the inter-ring torsional states of the biphenyl molecule using self-consistent field molecular orbital method. The potential goes through a minimum at an angle of 38°. The height of the potential barrier for the coplanar state is 2.01 kcal/mol. When the phenyl rings are perpendicular to each other, this height increases to 2.37 kcal/mol. The role of correlation and polarization is found to be important. The shape of the potential suggests that polyparaphenylene may possibly exist as a super helix.     

Photolysis of p-benzoquinone in N2 matrices at 12K: a novel decomposition pathway

Photolysis of _p-benzoquinone in N₂ matrices at 12K has been found to give acetylene and CO; 1,4-naphthoquinone and 9,10-anthraquinone, however, are inert under similar conditions.     

Synthesis of (+)-2R,3R,11R,12R- and (−)-2S,3S,11S,12S-tetraphenyl-18-crown-6

The synthesis of the title crown ethers starting from optically active hydrobenzoins is described. R(+)-1,in CDCl₃ ,preferentially extracts R(+)-phenylglycine methyl ester hydroperchlorate from an aqueous solution of the racemate with a chiral recognition factor of 1.5 as shown by nmr measurements.     

The mass spectra of 1,1,1-trichloro-2,4-pentanedione and its Al(III), Cr(III), Fe(III), Mn(II), Co(II) and Cu(II) complexes

The compounds 1,1,1-trichloro-2,4-pentanedione, Cu(II)tca₂, Co(II)tca₂, Mn(II)tca₂, Al(III)tca₃, Cr(III)tca₃ and Fe(III)tca₃ (tca?1,1,1-trichloro-2,4-pentanedionato, [CCl₃COCHCOCH₃]^?) have been prepared and their mass spectra have been obtained. The mass spectral results have been compared with findings for comparable fluorinated and nonhalogenated compounds. Comparisons are made in terms of internal redox reactions and hard and soft acid base theory. Rearrangement of chloride from ligand to metal accompanied by the elimination of CO or other neutral even electron fragments emerges as an important reaction for the ions of these compounds. While the internal redox reactions characteristic of all previous β-diketonate complex mass spectra still occur, their importance appears reduced to some degree by the facility of the chlorine rearrangement.     

Steric structure of phosphorus-contaiming heterocycles

Conclusions The steric structure of 3-halo-1-thia-3-phosphethanes with a tetracoordinated phosphorus atom was investigated by the methods of dipole moments and Kerr constants, enlisting data on quantum chemical calculations of the energies of the conformations.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2240–2244, October, 1973.The authors would like to thank I. M. Shermergorn for providing the samples for the investigations.     

Austausch von Chlorisotopen am Phosphoratom, 1. Mitt.: Dialkylchlorthiophosphate

Zusammenfassung An den Modellverbindungen Dialkylchlorthiophosphat (RO)₂P(S)Cl (R=Me, Et, n-Pr) und Diphenylchlorthiophosphat (PhO)₂P(S)Cl wurde der Austausch Chlorid—Radiochlorid am Thiophosphorylzentrum untersucht. Die bimolekularen Geschwindigkeitskonstanten, die Aktivierungsenergien und Aktivierungsentropien wurden berechnet. Der Einfluß von Substituenten auf bimolekulare Substitutionsreaktionen am vierfach koordinierten Phosphoratom wurde diskutiert.

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Chlorine isotopic exchange at phosphorus atoms, I.: Chloridothiophosphates

The chloride—radiochloride ion exchange at the thiophosphoryl centre has been studied using dialkylchloridothiophosphates (RO)₂P(S)Cl (R=Me, Et, n-Pr) and diphenylphosphorochloridothionate, (PhO)₂P(S)Cl, as model compounds. The bimolecular rate constants, energies and entropies of activation have been calculated. Effects of the substituents in the bimolecular displacement reaction on four-coordinated phosphorus atom have been discussed.

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Mit 3 Abbildungen     

Zur Oxydation von Tiron mit Wasserstoffperoxid in Gegenwart von Kobalt

Zusammenfassung Die Kinetik und der Mechanismus der von Kobaltionen katalysierten Tiron-Wasserstoffperoxid-Reaktion werden untersucht. Bei der Oxydation des Tirons bildet sich ein farbloses Produkt unbekannter Struktur, dessen Konzentrationszunahme zur photometrischen Messung der Reaktionsgeschwindigkeit dient. Unter den gewählten Bedingungen (3,56 · 10^–4 M Tiron, 0,1 M Wasserstoffperoxid, pH 10,3) verläuft die Reaktion bezüglich der Tiron- und Katalysatorkonzentration nach der 1. Ordnung. Die katalytische Reaktion, deren Geschwindigkeitskonstante zu 4,7 · 10⁴ l Mol^–1 · s^–1 ermittelt wurde, kann zur Kobaltbestimmung im Bereich von 0,6–10 ng/ml verwendet werden.Die Ergebnisse der Untersuchungen über die Oxydationsgeschwindigkeit des Tirons und über die Zersetzungsgeschwindigkeit des Wasserstoffperoxids in Abhängigkeit vom pH-Wert deuten darauf hin, daß die Zersetzung des Wasserstoffperoxids Voraussetzung für die Oxydation des Tirons ist. Während Tiron selbst eine stabilisierende Wirkung auf das Oxydationsmittel ausübt, katalysiert ein in Gegenwart von Kobaltionen entstehender Komplex dessen Zersetzung.

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Summary The kinetics and the mechanism of the tiron-hydrogen peroxide reaction catalysed by cobalt ions are investigated. The oxidation of tiron results in a product of unknown structure, whose increase of concentration is utilized for photometric reaction rate measurements. On the conditions used (3.56 · 10^–4 M tiron, 0.1 M hydrogen peroxide, pH 10.3) the reaction is of the first order with respect to tiron and catalyst concentration. The catalytic reaction, the rate constant of which was evaluated to be 4.7 · 10⁴ l · Mol^–1 · s^–1, can be used for the determination of cobalt in the range from 0.6 to 10 ng/ml.The results of the investigations on the oxidation rate of tiron and on the decomposition rate of hydrogen peroxide in dependence on pH indicate that the decomposition of hydrogen peroxide is a prerequisite for the oxidation of tiron. Whereas tiron itself shows a stabilizing effect on the oxidant, the complex formed in presence of cobalt ions catalyses the decomposition of hydrogen peroxide.

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Frau M. Borrmann gilt unser Dank für experimentelle Mitarbeit.     

Photofragmentierung von Cyclohexa-1,3-dien-5,6-dicarbonsäure-anhydriden [1]

The photochemical elimination of the anhydride function («C₂O₃») from the dihydrobenzenoid anhydrides 6a-6c is described. Some applications and limitations of this double bond producing reaction are given. A formal correlation between ease of «C₂O₃» elimination upon irradiation and upon electron impact respectively is indicated.