Separation and identification of organic and organometallic compounds by use of a liquid chromatography-particle beam-glow discharge mass spectrometry combination

Evaluation of the particle beam glow discharge mass spectrometry (PB-GDMS) system as a detector for liquid chromatography (LC) is described for the analysis of polycyclic aromatic hydrocarbons, steroids, selenoamino acids, and alkyllead compounds. A particle beam interface is used to introduce analyte species from the LC into a glow discharge source for subsequent vaporization and ionization. Mass spectra display classic EI fragmentation patterns for the organic compounds, as well as elemental and molecular information for the organometallic compounds. Chromatographic separations display good temporal correlation between UV and PB-GDMS detection modes. Detection limits for Pb in lead nitrate, triethyllead, and triphenyllead fall in the sub-ppb (ng) range.     

The role of surface oxides in formic acid oxidation on Au

Compared to Pt or Pd electrodes, Au is a poor catalyst for the direct anodic oxidation of HCOOH, but the formation of Au surface oxides in acidic solutions is accompanied by a fast oxidation of HCOOH. This fast reaction is not simply a secondary reaction of Au surface oxides since those oxides are kinetically stable in HCOOH solutions. They do oxidize HCOOH only via a slow and purely electrochemical process which occurs on free Au sites and is “driven” by oxide reduction. The fast HCOOH oxidation is due to a highly reactive intermediate which is able either to form stable Au oxides Au_nO_m or to react with HCOOH. Our results are consistent with the model that by the charge transfer step a reactive non-equilibrium {Au…O> species is formed which converts to stable equilibrium oxides Au_nO_m after migration and rearrangement steps. Pre-equilibrium <Au…O> oxidizes HCOOH and this oxidation is of lower order with respect to <Au…O> compared with the formation of Au_nO_m.     

A supersonic beam ion cyclotron resonance instrument for the study of van der Waals cluster ions

For the study of ionized van der Waals cluster ions an instrument is presented, which consists of a supersonic beam cluster source coupled to an ICR spectrometer with external ion source. The neutral van der Waals clusters are generated by supersonic expansion and ionized by electron impact in the external source. The cluster ions are extracted at right angle to the neutral cluster beam and fly collision-free parallel to the magnetic field direction into the differentially pumped ICR cell. For the ion transfer, an improved lens system is presented. The cluster ion transfer lens system is capable of focusing ions with energies of a few eV perpendicular to the magnetic field direction through the differential pumping orifice. The ions are injected into the ICR cell with a trap barrier pulse, ion accumulation is possible. With this system the first ICR spectra of small cluster ions of carbon dioxide are obtained.     

Darstellung und Struktur von Pyrazolyl-Kationen mit Polymethin- und Methan-Gerüst

The 4-pyrazoline-3-one1 reacts with 4-dimethylaminobenzaldehyde to yield the stable asymmetric cyanine dye2b which reacts with1 to give the colorless (aryl) (dipyrazolyl) methane3b. Using aldehydes with less cationstabilizing groups the polymethines2 are not isolated but only the methanes3. The structures of2b and3 are discussed by¹ H,¹³C and Hetero NMR spectra.     

Reactions of heterocyclic cations with nitrogen-containing nucleophiles. 10. Synthesis of 3,5,7-triaryl-1,2-oxazepinium perchlorates by the reaction of 2,4,6-triarylpyrylium salts with nitrones and substituted hydroxylamines

2-Substituted 3,5,7-triaryl-1,2-oxazepinium perchlorates were obtained by the reaction of 2,4,6-triarylpyrylium salts in dimethylformamide with nitrones and N-arylhydroxylamines. The products are the first representatives of seven-membered cations with eight electrons.See [1] for Communication 9.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 457–460, April, 1982.     

Role of phosphates in the promotion of silver catalysts for partial oxidation: I. Structure and properties of phosphates on the surface of polycrystalline silver

The chemical composition, structure, and properties of an H₃PO₄-promoted polycrystalline silver foil are studied by XPS. The surface of the doped sample contains oxygen in two states with binding energies of 531.1 and 533.0 eV. Heat treatment results in silver clusters distributed in the polyphosphate matrix. It follows from TDS data that the surface of the promoted catalyst contains a strongly bound oxygen species that desorbs at ~900 K. It is believed that the silver clusters stabilized by the phosphate matrix are active sites on the surface of the phosphorus-promoted catalyst.Translated from Kinetika i Kataliz, Vol. 46, No. 1, 2005, pp. 153–160. Original Russian Text Copyright © 2005 by Knyazev, Boronin, Vodyankina, Koshcheev, Kurina.     

Structural studies on layered alkylpyridinium iodopalladate networks

The reaction of alkylpyridinium (CnH2n + 1NC5H5, hereafter Cn-Py) iodide salts in aqueous acetonitrile with a preformed palladium iodide precursor afforded two different types of organic-inorganic phases depending on the molar ratio. A 2:1 ratio yielded the phase [Cn-Py]2[PdI4] (3, n = 14, 16), which crystallized in the triclinic crystal system. The X-ray crystal structure of 3, (n = 14), refined in the space group P1 (a = 8.918(3) A, b = 9.894(3) A, c = 29.062(12) A, alpha = 93.51(3) degrees, beta = 94.17(3) degrees, gamma = 115.60(3) degrees, and Z = 2), consists of interdigitated bilayers with a basal spacing of 29.0 A. The aliphatic chains of the cations, which run almost parallel to the stacking direction, are fully stretched between polar planes built on isolated [PdI4]2- anions and cation headgroups. Changing the organic cation to palladium ratio to 1:1 led to a new phase [Cn-Py]2[Pd2I6] (4, n = 14, 16), which crystallizes in the triclinic P1 space group (a = 9.399(4) A, b = 14.264(6) A, c = 29.415(13) A, alpha = 92.11(4) degrees, beta = 90.07(4) degrees, gamma = 104.53(3) degrees, Z = 3 for 4(n = 14); a = 9.417(2) A, b = 14.215(3) A, c = 31.552(6) A, alpha = 87.96(3) degrees, beta = 87.63(3) degrees, gamma = 75.67(3) degrees, Z = 3 for 4(n = 16)). The layered structure is basically of a continuously interdigitated single-layer type, with a bilayer sublattice superimposed. Isolated [Pd2I6]2- anions contribute to the inorganic planes. A high degree of interdigitation and tilting of the aliphatic chains lead to basal spacings of 29.4 and 31.5 A for 4(n = 14) and 4(n = 16), respectively. The [Cn-Py]2[PdI4] and [Cn-Py]2[Pd2I6] phases were characterized by thermal analysis. Mesomorphic behavior was observed only for 3(n = 16), which was confirmed by variable-temperature powder XRD and optical microscopy.     

Analysis of influence of spin relaxation on form of nuclear magnetic resonance spectra in liquids with radiofrequency pumping

For a model system of two nonequivalent nuclei with spin 1/2, the NMR spectrum of one of the nuclei has been calculated under conditions of pumping of the second spin, and a study has been made of the spectral transformation upon changing the times of transverse and longitudinal relaxation of both spins. It has been established that the form of the spectrum undergoes qualitative changes. An increase in the rate of transverse relaxation not only broadens the observed lines, but simultaneously changes the character of motion of the spins in the pumping field: With increasing relaxation rate, the motion is converted from coherent motion (nutation) to incoherent motion (transitions between levels, saturation effect). Transformations of the spectrum are related specifically to these changes.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 23, No. 4, pp. 436–443, July–August 1987.     

The synthesis of cis- and trans-1,2-dibromocyclopropane

A preparative route to cis- and trans-1,2-dibromocyclopropane ($\text{1}$) was developed via the Hunsdiecker reaction of silver cyclopropane-1,2-dicarboxylate ($\text{2}$). Cis- and trans-$\text{2}$ gave the same ratio of cis- and trans-$\text{1}$ (1:3.2). The mechanism of this reaction is briefly discussed.