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.     

Beiträge zum chemischen Transport oxidischer Metallverbindungen. V. Der Transport ternärer und quaternärer Mischferrite über ihre Metallchloride

Contributions to the Chemical Transport of Metal Oxides. V. Transport of Ternary and Quaternary Mixed Ferrites by their Chlorides The transport by means of HCl as transporting gas in a closed system in the case of the ternary mixed ferrites (Ni_0,8Fe_2,2O₄, Mn_0,75Fe_2,25O₄, Mn_1,286Fe_1,714O₄) and the quaternary mixed ferrites (Mg_0,5Mn_0,5Fe₂O₄, Mg_0,75Mn_0,536Fe_1,714O₄, Mg_0,281Mn_0,469Fe_2,25O₄, Mn_0,5Zn_0,5Fe₂O₄, Mn_0,5Zn_0,45Fe_2,05O₄, Ni_0,5Zn_0,5Fe₂O₄) between T₂ = 1100?1000°C and T₁ = 1000?800°C was investigated. Transported crystals were characterized by chemical analysis and the saturation magnetization, the transport rate has been checked. In the case of Mn_0,5Zn_0,45Fe_2,05O₄ two phases were transported. By discussing the phase diagram an explanation is given.     

Macroreticular ion-exchange resins: some analytical applications to petroleum products

Extraction and subsequent recovery, in four separate fractions, of naphthenic acids, alkylphenols, pyrrollic compounds and nitrogen bases can be made from petroleum products using macroporous ion-exchange resins. Distinctive features of the technique are the use of dissolved gases in polar solvents as eluants and the application of the carbonate form of anion-exchange resins. The transition metal form of a macroreticular cation exchanger is shown to extract ligands from non-aqueous systems and a specific application to petroleum analysis is given.     

Discontinuous-flow potentiometric determination of chloride in a large-volume wall-jet cell using an ion-selective electrode based on a silver chloride film chemically deposited on a silver iodide support

A robust and sensitive chloride ion-selective electrode can be prepared by modifying the surface of an iodide-selective electrode using the chemical reaction with mercuric chloride in an oxidizing medium containing excess chloride. A thin film of silver chloride is thus formed ensuring a rapid and reproducible response to chloride. The analytical parameters of this electrode are similar to those of commercial silver chloride ion-selective electrodes, but its electrical impedance and signal noise are substantially lower and the response somewhat faster. Its sensitivity toward surfactants is somewhat suppressed. The electrode was used for discontinuous flow potentiometric (DFP) determinations in a large-volume wall-jet cell in which the electrode surface can be continuously reactivated by a cleaning solution contained in the cell. The method was applied to determination of chloride in ground waters from an industrial waste dumping site. The limit of determination is low 9 mug Cl(-)/l (2.6 x 10(-7)M), the precision good (the relative standard deviation varies from 0.6 to 3.0% for chloride contents from 2.90 to 0.15 mg/l, respectively) and the method correlates satisfactorily with the results of an indirect AAS determination of chloride. The sample throughput is high-90 measurements can be carried out per hour, corresponding to 30-40 determinations per hour.     

Gas chromatographic system equipped with a mass detector and a selective nitrogen-phosphorous detector operating simulataneously in the analysis of pesticide residues

The possibility to perform gas chromatographic analysis using both a mass detector and a selective nitrogen-phosphorous detector will enable highly sensitive analytical results and an optimal identification reliability. In this work we describe an easily workable technical solution, which has been accomplished in our laboratory and the application of the above system to analytical procedures for the detection and determination of nitrogenous herbicides in drinking water and phosphorylated pesticides in agricultural products is discussed.     

Synthesis ofS-(+)-hydroprene

A novel path toS-(+)-hydroprene (1) starting from the technical gradeS-(+)-dihydromyrcene (2, e.e. 50%) is proposed. The latter was selectively transformed intoS-3,7-dimethyloctanal (5) in three steps including hydroalumination. The reactions of5 with allyl- or methallylmagnesium chloride followed, respectively, either by oxygenation in the presence of PdCl₂/CuCl or by ozonolysis, affordS,E-6,10-dimethyl-3-undecen-2-one (7) which was treated with ethoxyethynylmagnesium bromide to give the title juvenile hormone analogue in 23% overall yield.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No 1, pp. 110–112, January, 1993.     

Electronic and crystalline structure of Si/SiO2 interface modified by ArF excimer laser

The native oxide layers on Si(100) surface were irradiated under UHV conditions by an ArF excimer laser pulses with energy density varied between melting and evaporating thresholds. The resulting changes were studied by LEED, AES and UPS. The increase of the energy density up to evaporation threshold results in the recrystallisation of native oxide layer. The pulses with energy densities just above the evaporation threshold ablate the top layer leaving an ordered and atomicaly clean surface. The observed (1x1) surface reconstruction is probably stabilised by strains introduced during rapid melting and quenching of the topmost layers. The surface electronic structure is dominated by random satisfaction of dangling bonds swearing a well defined surface states observed on (2x1)Si(100) surface.