Low-temperature hydride furnace modified for the atomic absorption spectrometric determination of metals with low appearance temperatures

The sample is vaporized from tungsten filament coils (150 W) and transported by an argon stream to the cell of a modified hydride furnace for atomic absorption spectrometry (a.a.s.). The system provides almost the same sensitivity for elements with low appearance temperatures (e.g., Bi, Cd, Pb, Tl, Zn) as graphite-furnace a.a.s. The detection limits are between 0.1 and 5 ng ml^?1, depending on the element.     

Efficient electron transfer through a triazole link in ruthenium(II) polypyridine type complexes

Spectroscopic, electrochemical and theoretical characterisations of photoactive systems readily assembled via click-chemistry show an efficient bi-directional charge shift through the triazole link.     

Über die Reaktionen von Guanidin bzw. Harnstoff mit Cyanhydrinen

Action of guanidine or urea on cyclohexanone-, cyclopentanone-, cycloheptanone-and acetonecyanohydrine3 a?3 d generates very different products: 3 a reacts with guanidine inDMF to yield 1,3-diazaspiro[4.5]decane-2,4-diimine (5 a). Heating the components without solvent affords 7,14-diazadispiro[5.1.5.2]pentadecan-15-one(7)^15–17, the guanidine not participating in the reaction; similarly3 b is transformed by guanidine to a pentacyclic dispirocompound (possible formulae19 and20), whereas3 d reacts to give 3,3,5,5-tetramethylpiperazine-2,6-dione(21)¹⁹. In 3-pentanone guanidine-cyanide condensates itself to give 2,4-diamino-triazine (22)^{21, 22}. Action of urea on3 a?3 d yields the 4-imino-1,3-diazaspiroalkan-2-ones6 a?6 c and the 4-imino-5,5-dimethylimidazolidin-2-one6 d ^6–8 resp. If the reaction of urea and3 d is carried out inDMF, however, 5,5-dimethyl-4-ureido-3-imidazolin-2-one (28) (or the tautomeric carbamoyliminoimidazolidinone27) is produced. The structures of the compounds prepared are proved by NMR-, IR- and mass spectra.     

Starke verdrillungen trotz schwacher sterischer hinderung

Considerable twisting of weakly hindered hydrazonyl radicals is explained on the basis of a low barrier to rotation due to compensation of the loss of π-π-delocalization on twisting by gain of π-σ-delocalization.     

Rapid Autoxidation Forms Highly Oxidized RO2 Radicals in the Atmosphere

Gas‐phase oxidation routes of biogenic emissions, mainly isoprene and monoterpenes, in the atmosphere are still the subject of intensive research with special attention being paid to the formation of aerosol constituents. This laboratory study shows that the most abundant monoterpenes (limonene and α‐pinene) form highly oxidized RO₂ radicals with up to 12 O atoms, along with related closed‐shell products, within a few seconds after the initial attack of ozone or OH radicals. The overall process, an intramolecular ROO→QOOH reaction and subsequent O₂ addition generating a next R′OO radical, is similar to the well‐known autoxidation processes in the liquid phase (QOOH stands for a hydroperoxyalkyl radical). Field measurements show the relevance of this process to atmospheric chemistry. Thus, the well‐known reaction principle of autoxidation is also applicable to the atmospheric gas‐phase oxidation of hydrocarbons leading to extremely low‐volatility products which contribute to organic aerosol mass and hence influence the aerosol–cloud–climate system.     

On the backscattering factor in quantitative Auger electron spectroscopy of binary alloys

The matrix dependent relative sensitivity factor S_rel(c) is considered for use in quantitative Auger analysis. It is affected by matrix dependent factors like the backscattering factor, the escape depth of Auger electrons and the number of atoms per unit volume. The backscattering factor, especially, is evaluated and possibilities of its determination are shown. Measurements of Auger intensities and of the energy distribution of backscattered electrons were carried out for this purpose on a series of CuPd and CuSb alloys, respectively. The backscattering factor thus obtained is compared with values resulting from a formula of JABLONSKI and by experimental data of SMITH and GALLON .