The pyrolysis of trimethylgermane and trimethylsilane

The number of products and the H₂/CH₄ ratio obtained from the flow pyrolyses of (CH₃)₃GeH and (CH₃)₃SiH were very different. The (CH₃)₃GeH decomposition is consistent with the following mechanism:

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The pyrolysis of (CH₃)₃SiH was found to be much more complex, presumably due to the formation of silicon-carbon double bonded intermediates and the (CH₃)₂Si(H)CH₂ radical. We also present data which supports the presence of a H atom chain sequence during this pyrolysis.     

Anionic polymerization of 1,2-butylene oxide

Anionic polymerizations of 1,2-butylene oxide were carried out in vacuum-sealed dilatometers in the range of 30–60°C. Potassium terbutoxide and dimsyl sodium were used as initiators; dimethyl sulfoxide (DMSO) and mixtures of DMSO with tetrahydrofuran were solvents. The polymer products were analyzed by gel permeation chromatography and infrared spectroscopy. The object of the investigation was to obtain information on the mechanism of the reaction and to elucidate some of its kinetic aspects. It has been shown that the polymerizations occur by two different processes, depending on the choice of experimental conditions. One of the processes involves free ions and ion-pairs, the other, ion-pairs alone. In the first case, where dimethyl sulfoxide is used as solvent, the order of the reaction with respect to the initiator concentration far exceeds unity (～1.8), while in the second case, involving mixed solvents, the order of the reaction, for all practical purposes, is one.     

Chemical structure of cow kappa-casein: study of the soluble tryptic peptides

The sequences of 13 tryptic peptides of cow ?_A-casein (accounting for about one half of the amino acid residues present in the protein) were established. The rennin sensitive linkage could be located in a large fragment (36 residues). ?-casein consists of a hydrophilic part (?-caseino-glycopeptide) and of a hydrophobic moiety (para-?-casein); in this latter, however, several quite hydrophilic sequences were characterized. Another feature of the ?-casein structure is the frequent duplication or triplication of certain amino acids (Pro-Pro; Phe-Phe; Gln-Gln-Gln-Asn-Glu-Glu-Glu; Pro-Pro-Lys-Lys-Asn-Gln-; etc. …).     

Reconocimiento de nicotina en una hebrita de tabaco

Summary Adaption of theLuís method for the detection of nicotine to microscale, usingEmich's capillary technic proved successful, attaining identification limit of 0,03g.Applying a sub-micro steam distillation effect, the nicotine in a speck of tobacco (1 mm² and less) could still be detected by using the above reaction.Extension of the above procedure to mixtures of nicotine with substances not volatile with steam, inorganic (halides) as well as organic compounds (other alkaloids, acids, etc.) proved to be successful, even when the nicotine is present in proportions of only 1 part in 1000.

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Zusammenfassung Die Anwendung der Kapillartechnik vonEmich zum Nachweis von Nikotin nachLuís war erfolgreich und zeigte eine Erfassungsgrenze von 0,03g.Bei Anwendung einer Ultramikrodampfdestillation kann das Nikotin nach obiger Methode noch in Spuren von Tabak (1 mm² und weniger) nachgewiesen werden.Die Reaktion ist auch positiv bei Gemischen von Nikotin mit anderen, mit Wasserdampf nicht flüchtigen sowohl anorganischen (Halogenide) als auch organischen Substanzen (andere Alkaloide, Säuren etc.), selbst dann noch, wenn das Nikotin bloß im Verhältnis von 11000 vorhanden ist.

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Résumé La technique capillaire d'Emich a été utilisée avec succès pour identifier la nicotine suivant le procédé deLuís; la limite de sensibilité est alors de 0,03g. La mise en oeuvre d'un ultramicroentraînement à la vapeur permet en outre, par application de la précédente méthode, d'identifier la nicotine dans des traces de tabac (moins de 1 mm²). La réaction est également positive en présence d'autres substances non entraînables par la vapeur d'eau, qu'elles soient minérales (halogénures) ou organiques (autres alcaloïdes, acides, etc. ...) même si la proportion de nicotine n'est que de l'ordre de grandeur de 1/1000.

     

EDTA titration of calcium and magnesium with a calcium-selective electrode

Direct semi-automatic and automatic derivative potentiometric EDTA procedures for the determination of calcium and/or magnesium with a calcium-selective electrode are described. Calcium is titrated in the presence of magnesium at pH 12.0 and the total calcium and magnesium is determined at pH 9.7. Calcium in the range 1-8 mg and magnesium in the range 0.7-5 mg are determined semi-automatically with average errors of about 0.2 and 0.3% respectively and automatically with average errors of 0.4 and 0.7%. Titration times vary from a few seconds to a few minutes.     

New approach to synthesis of aromatic N-phenyl-substituted polyamides

It is shown that polyimidates obtained by polycondensation of bisphenols with imidoyl chlorides may be transformed into N-phenylsubstituted aromatic polyamides. The rearrangement occurs as a result of heating at 260–340°C, and, in a diphenyl ether solution, at 240°C. The resulting polymers are soluble in organic solvents and demonstrate high thermooxidative stability.     

Structural relationships in close-packed AB2O4 oxides involving spinel,olivine, and hexagonal LiFeSnO4 structures

Close-packed structures with formula AB₂O₄ were studied in terms of polyhedra arrangement. The junction between octahedral layers (kagome) and mixed (octahedral and tetrahedral) layers were analyzed; this association allows one to determine two types of double layers whose packing leads to three closely related structural types: spinel, double-hexagonal LiFeSnO₄, and a hypothetical hexagonal structure. Olivine structure shows a polyhedral arrangement closely related to those of these three structures and can be described alike in terms of mixed layers and double layers. AB₂O₄ close-packed oxides can exhibit polymorphism; from this analysis a mechanism, involving geometrical operations applied to the double layers, is proposed for the different transitions, really observed as (DH) LiFeSnO₄ spinel and olivine-spinel or theoretical as (DH) LiFeSnO₄—hypothetical hexagonal and olivine—hypothetical hexagonal.     

ULTRAVIOLET AND N-FORMYL-KYNURENINE-SENSITIZED PHOTOINACTIVATION OF BOVINE CARBONIC ANHYDRASE: AN INTERNAL PHOTODYNAMIC EFFECT

Abstract —Direct photoinactivation by UV light of bovine carbonic anhydrase, as well as its photosensitization by N -formyl-kynurenine, a tryptophan photooxidation product, have been investigated. In the presence of oxygen both methods lead to similar results: the enzyme loses its activity, the tryptophanyl, histidyl and, to a lesser extent, tyrosyl residues being destroyed. In nitrogen-saturated solutions, a dramatic drop is observed in the photoinacitivation yield under the direct action of ultraviolet light, whereas histidyl residues remain intact. Evidence indicates an internal photodynamic action of N -formyl-kynurenine in the protein core produced by the UV photooxidation of tryptophanyl residues. Photoinactivation of oxygenated enzyme solutions by external and internal photodynamic action correlates with histidyl residue destruction via singlet oxygen. The possible importance of the photodynamic ability of N -formyl-kynurenine in the photochemistry of proteins, DNA, and cells is discussed.     

The Enol of Acetone during Photochemical Reactions of 3-Hydroxy-3-methyl-2-butanone and of Acetone

The enol of acetone, formed by disproportionation reactions of 1-hydroxy-1-methylethyl radicals, is detected by NMR, spectroscopy during photoreactions of 3-hydroxy-3-methyl-2-butanone in acetonitrile and of acetone in 2-propanol and slowly tautomerizes to acetone. The photolysis of 3-hydroxy-3-methyl-2-butanone is shown to proceed via Type I cleavage, predominantly from an excited triplet state.