Preparation and NMR spectra of substituted 2-phenyl-5,5-dialkylimidazolinones

Eighteen substituted 2-phenyl-5,5-dialkylimidazolinones 2 have been prepared by cyclizations of substituted 2-(N-benzoylamino)alkanamides 1. The cyclization of methylamides 1 proceeds at room temperature whereas primary amides are cyclized on boiling. The ¹H and ¹³C nmr spectra of the imidazolinones are presented and the changes in their spectra connected with their protonation in hexadeuteriodimethyl sulfoxide-trifluoroacetic acid mixtures are discussed.     

Use of x-ray fluorescence spectrometry in ion-exchange studies of leach liquors

Equilibrium and kinetic studies of ion exchange of a complex leach liquor from coal ash, with strongly basic resins and a liquid ion exchanger are reported. The multi-component system was studied by determining the composition of the effluents and by non-destructive analysis of the loaded ion exchangers by XRF spectrometry. In the case of column operation, the elution processes were investigated by the same method, which was very appropriate for non-destructive monitoring of resin regeneration steps done repeatedly with the same resin sample.     

An Improved HPLC Post-Column Methodology for the Identification of Free Radical Scavenging Phytochemicals in Complex Mixtures

The importance of natural antioxidants principally relates to their health-promoting properties. The discovery of new sources of established compounds or more potent compounds is a costly exercise and any technique capable of aiding this procedure would be highly significant. An approach combining chromatographic separation, component analysis and post-column identification of free radical scavenging has been reported. However, its effectiveness is dependent upon various factors and the number of samples analyzed without operator intervention is restricted. A more applicable technique using a 10% to 100% methanol with 2% acetic acid mobile phase and a citric acid-sodium citrate buffered methanolic 1,1-diphenyl-2-picrylhydrazyl free radical reagent is presented, whereby free radical scavengers can be detected within crude extracts of variable polarity without special considerations. As an illustration, acetone, 70% (aq.) methanol and acetonitrile-soluble extracts were prepared from sage (Salvia officinalis L.) for extraction of polar and non-polar radical scavengers and analyzed. Radical scavenging components were identified as carnosic, caffeic and rosmarinic acids and luteolin-7-O-glycoside. Others radical scavengers were tentatively identified as benzoic and hydroxycinnamic acid derivatives, flavonoids and diterpenoids. Through the application of this technique, carnosic acid and rosmarinic acid were identified as the principal free radical scavengers.     

Thermal decomposition of N2H6GeF6 · H2O,isolation and characterization of intermediates

The thermal behaviour of N₂H₆GeF₆ · H₂O was investigated by TG, DTG and DTA measurements. The decomposition proceeded in three steps, in which anhydrous N₂H₆GeF₆ and N₂H₅GeF₅; were isolated and characterized by chemical analysis and vibrational spectroscopy. The X-ray powder photographs of the intermediates were indexed, namely, for N₂H₆GeF₆ on the basis of a monoclinic cell with a = 8.86(9), b = 9.29(2), c =7.40(0) Å, β = 85° and for N₂H₅GeF₅ on the basis of an ortrhorhombic cell with a = 8.43(5),b = 9.19(9), c = 7.43(6) Å.     

Exchange of halogen bonded on aromatic core. Heterogeneous catalysis—I : Reaction mechanism of iodine exchange in o-iodobenzoic acid

Reaction mechanism of halogen exchange between arylhalogenide and halogenide anion is studied in a case when the aromatic core is inactivated with respect to the S_NAr substitution by other substituents. The exchange of iodine between o-iodobenzoic acid and ¹³¹I labelled NaI serves as a modelling reaction. The reaction was found to proceed heterogeneously on a glass surface. In the case of a rapid course of the surface reaction the reaction mechanism is more complicated and the equation derived by McKay cannot be applied for expressing the time dependence of the degree of isotopic exchange. Reaction mechanism was proposed for this reaction and compared with experimental data.     

Structural characterisation of tyrosine-nitrated peptides by ultraviolet and infrared matrix-assisted laser desorption/ionisation Fourier transform ion cyclotron resonance mass spectrometry

Nitration of tyrosine residues in proteins may occur in cells upon oxidative stress and inflammation processes mediated through generation of reactive nitroxyl from peroxynitrite. Tyrosine nitration from oxidative pathways may generate cytotoxic species that cause protein dysfunction and pathogenesis. A number of protein nitrations in vivo have been reported and some specific Tyrosine nitration sites have been recently identified using mass spectrometric methods. High-resolution Fourier transform ion cyclotron resonance mass spectrometry (MALDI) FT-ICR-MS) is shown here to be a highly efficient method in the determination of protein nitrations. Following the identification of nitration of the catalytic site Tyr-430 residue of bovine prostacyclin synthase, we synthesised several model peptides containing both unmodified tyrosine and 3-nitro-tyrosine residues, using solid-phase peptide synthesis (SPPS). The structures of the nitrotyrosine peptides were characterised both by ESI- and by matrix-assisted laser desorption/ionisation (MALDI)-FT-ICR-MS, using a standard ultraviolet (UV) nitrogen nitrogen laser and a 2.97 microm Nd-YAG infrared laser. Using UV-MALDI-MS, 3-nitrotyrosyl-peptides were found to undergo extensive photochemical fragmentation at the nitrophenyl group, which may hamper or prevent the unequivocal identification of Tyr-nitrations in cellular proteins. In contrast, infrared-MALDI-FT-ICR-MS did not produce fragmentation of molecular ions of Tyr-nitrated peptides.     

Simple <Emphasis Type="Italic">b</Emphasis> ions have cyclic oxazolone structures. A neutralization-reionization mass spectrometric and computational study of oxazolone radicals

The 2-methyloxazol-5-on-2-yl radical (3) and its deuterium labeled analogs were generated in the gas-phase by femtosecond electron-transfer and studied by neutralization-reionization mass spectrometry and quantum chemical calculations. Radical 3 undergoes fast dissociation by ring opening and elimination of CO and CH(3)CO. Loss of hydrogen is less abundant and involves hydrogen atoms from both the ring and side-chain positions. The experimental results are corroborated by the analysis of the potential energy surface of the ground electronic state in 3 using density functional, perturbational, and coupled-cluster theories up to CCSD(T) and extrapolated to the 6-311 ++ G(3df,2p) basis set. RRKM calculations of radical dissociations gave branching ratios for loss of CO and H that were k(CO)/k(H) > 10 over an 80-300 kJ mol(-1) range of internal energies. The driving force for the dissociations of 3 is provided by large Franck-Condon effects on vertical neutralization and possibly from involvement of excited electronic states. Calculations also provided the adiabatic ionization energy of 3, IE(adiab) = 5.48 eV and vertical recombination energy of cation 3(+), RE(vert) = 4.70 eV. The present results strongly indicate that oxazolone structures can explain fragmentations of b-type peptide ions upon electron capture, contrary to previous speculations.     

Neighbouring group participation in formation of condensed azines. Formation of pyrazolo(3,4-b)pyrazines,isoxazolo(4,5-b)pyrazines and isothiazolo(5,4-b)pyridine

Pyrazine- and pyridinecarboxamidoximes with an amino, potentially tautomeric hydroxy or mercapto group inortho position could be transformed in the appropriate condensed azines. In this manner, representatives of pyrazolo(3,4-b)pyrazine, isoxazolo(4,5-b)pyrazine and isothiazolo(5,4-b)pyridine ring system were synthesized and some transformations investigated.Presented in part at the 8th International Congress of Heterocyclic Chemistry, Graz, 1981.     

Strukturanalyse organischer Sulfide mit Hilfe der Gras-Chromatographie

Zusammenfassung Eine Methode der Identifizierung von Alkyl- und Arylgruppen organischer Sulfide wurde ausgearbeitet, die die Spaltung dieser Stoffe mit Raney-Nickel zur gaschromatographischen Bestimmung der dabei entstandenen Kohlenwasserstoffe ausnützt.

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Summary A method was developed for identifying alkyl- and aryl groups of organic sulfides. The method employs the cleavage of these materials with Raney nickel for the gas chromatographic determination of the resulting hydrocarbons.

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Résumé On a mis au point une méthode d'identification des groupes alkylés et arylés des sulfures organiques exploitant la dissociation de ceux-ci par le nickel Raney pour le dosage par chromatographic en phase gazeuse des carbures d'hydrogène qui se forment.

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Die Autoren danken den Kollegen Dr.M. Veea, Ing.J. Petránek und Ing.J. Gaspari für die Überlassung von Proben organischer Sulfide.     

Comparative EIS study of a paste electrode containing zinc powder in neutral and near neutral solutions

The corrosion and passivation of Zn powder particles dispersed in a paste electrode immersed in 0.5 M Na₂SO₄ and 5×10^–3 M Na₂HPO₄ solutions were studied mainly by electrochemical impedance spectroscopy. The role played by diffusion in the mechanism of anodic oxidation of zinc powder particles has been shown. It was demonstrated that the anodic reactionof Zn powder in neutral or near neutral media involves at least two adsorbed intermediates. By simulating the porous structure of the electrode, some information about porous nature of zinc electrode could be extracted. Electronic Publication