Polychlorierte Verbindungen und ihre Verwendung zur gas-chromatographischen Bestimmung von Elementen im ng-Bereich

Zusammenfassung Aus polychlorierten Kaliumxanthogenaten wurden verschiedene Metall-Chelate dargestellt, dünnschicht-chromatographisch getrennt und ihre R_f-Werte unter verschiedenen Trennbedingungen bestimmt.Anschließend wurden die einzelnen Komplexe gas-chromatographisch mit Elektroneneinfang-Detektoren untersucht. Über den durch augenblickliche thermische Zersetzung des Chelats in reproduzierbarer Menge anfallenden polychlorierten Alkohol konnten Metalle im ng-Bereich quantitativ indirekt bestimmt werden.

---

Polychlorinated compounds and their use for the gas-chromatographic determination of elements in the ng-rangeI. Polychlorinated xanthates and their use for the determination of nickel

Ten chelates of polychlorinated xanthates were investigated by thin-layer chromatography. Their R_f-values were determined on silica gel and aluminium oxide for several different eluents. At 200° C the xanthates pyrolize momentarily and reproducibly to the corresponding alcohol, allowing the perchlorinated ligands to be utilized for the determination of metals by electron capture gas-chromatography.Combining thin-layer chromatography and the pyrolyzing technique nanogram amounts of mixtures of metals can be determined.

---

---

Die Arbeit wurde in dankenswerter Weise von der Deutschen Forschungsgemeinschaft, Bad Godesberg, der Fazitstiftung, Gemeinnützige Verlagsgesellschaft m. b. H, Frankfurt a. M., und dem Verband der Chemischen Industrie e.V., Düsseldorf, unterstützt.     

Polynuclear nonfused bis(1,3,4-oxadiazole)-containing systems

Nonfused bis-1,3,4-oxadiazoles were synthesized by reaction of 5-substituted mono-and bis-tetrazoles with mono-and dicarboxylic acid chlorides. The results of kinetic studies showed that the transformation of tetrazoles into 1,3,4-oxadiazoles is accelerated by 1 to 2 orders of magnitude on addition of a catalytic amount of dimethylformamide, triethylamine, or pyridine.     

The effect of preparation procedure and composition of water-ethanol suspensions of amorphous silica on their aggregative stability and kinetics of coagulation

The method of flow ultramicroscopy is employed to study the effect of the composition and preparation procedure of dilute water-ethanol suspensions of two samples of amorphous silica (fractionated fused quartz and monodisperse amorphous silica) on the kinetics of their coagulation. It is revealed that all suspensions prepared by the addition of silica powders to water-ethanol mixtures with ethanol contents of 96 and 40 vol % are stable with respect to aggregation, as the suspensions prepared by the addition of aliquots of concentrated dispersions of the aforementioned silica samples in 96% ethanol aged for different time periods to water-ethanol mixtures containing 96 vol % ethanol. At a 40-vol % content of ethanol in the mixture, the coagulation whose character (including “superfast” coagulation) substantially depends on the time of aging of initial concentrated silica dispersions occurs. Furthermore, kinetic studies are performed for the coagulation of dilute silica suspensions prepared by the addition of silica powders to water-ethanol solutions containing 40 vol % of ethanol and traces (<1 ppm) of poly(ethoxysilane), poly(acrylic acid), and a supernatant prepared by the centrifugation of concentrated silica dispersion in 96% ethanol aged for more than 3 months. It is found that the addition of aliquots of the aforementioned ethanol solutions to silica suspensions in 40% ethanol, which are initially stable with respect to aggregation, causes their superfast coagulation.     

Cotton-mouton constants and spatial structure of pyridiniumethane derivatives and their analogs in aqueous media

A conformational analysis has been performed on 1,2-dipyridiniumethane and 1,2-diisoquinoliniumethane, using data on the Cotton-Mouton effect in water and in methanol. It has been shown that, in comparison with the 1,2-dibenzyl derivatives, in aqueous media, an abnormally high excess of the gauche conformer over the trans conformer is observed, an effect that is attributed to the formation of hydrate bridges.Deceased.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2766–2771, December, 1991.     

Structure-parameter and force-field refinement for lead dihalide molecules

Conclusions It has been shown for PbF₂ that one can process electron-diffraction data for molecules containing heavy atoms on the basis of atomic scattering amplitudes calculated with a relativistic approximation for the atomic electron density. The errors in calculating the atomicscattering amplitudes explain the previous discrepancies in the observed values for the Pb-Cl amplitudes in PbCl₂ derived in two independent researches. The differences between those values are now not so considerable, and they may be explained as due to experimental error or to the processing of the measurements in Hungary for most of the scattering angles having been performed without the relativistic corrections to the electron density.Our mean-square vibration amplitudes and the measured frequencies can be used with our semiempirical relationships for the force constants to determine the potential-energy parameters for those molecules and to estimate the vibrational frequencies for PbI₂, which have not been measured.I am indebted to Professor V. P. Spiridonov and staff at the vapor electron-diffraction laboratory at Moscow University for providing the observed values for the reduced molecular component of the scattering intensities for lead dihalides and for valuable comments in discussion on the draft.High-Temperature Institute, Academy of Sciences of the USSR. Translated from Zhurnal Strukturnoi Khimii, Vol. 32, No. 1, pp. 54–59, January–February, 1991.     

The structure of the 1-1-difluoroethylene radical anion and the factors determining the hyperfine interaction with 19F

A structure with a pyramidal -CF₂ group is shown to desribe satisfactorily hyperfine interactions in CH₂CF_$\text{2}$ radical anions within the framework of the INDO method. The factors responsible for the substantial difference in the degree of spin density delocalization on F in CH₂CF_$\text{2}$ and C₂F_$\text{4}$ are analyzed.     

Molybdenum-95 NMR spectra of some molybdenum carbony and related compounds

Molybdenum-95 NMR spectra have been measured for a selection of molybdenum carbonyl compounds and Mo(Σ-C₅H₅)(η-C₅H₅)(NO)(S₂CNMe₂). A chemical shift range of more than 1500 ppm is found. The chemical shifts and linewidths are discussed.     

Synthesis and spatial structure of the geometrical isomers of 4-substituted 1-tert-butyl-3-methyl-piperidin-4-ols and 4-acyloxy-1-tert-butyl-3-methylpiperidines

In order to study the interrelationship between the structure, reactivity, and spectroscopic characteristics of the stereoisomeric piperidines, starting from 1-tert-butyl-3-methylpiperidin-4-one the synthesis has been performed of the geometric isomers of some 4-substituted 1-tert-butyl-3-methylpiperidin-4-ols and 4-acyloxy-1-tert-butyl-3-methylpiperidines. The spatial structures of the compounds obtained have been determined by IR and PMR spectroscopy.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1056–1061, August, 1973.     

Automated determination of fluoride ion in the parts per milliard range

Fluoride, down to 2 ppM, has been determined by automated direct potentiometry using a fluoride ion-selective electrode. The method reduces the dilution and contamination effects of TISAB and takes the electrode response-time into consideration. The relative standard deviation for water samples is 1.5-1.8% and the recovery varies from 96 to 107%.     

Conformations of fused cycloalkanes in organometallic complexes : IV. The crystal and molecular structure of tricyclo-[6.4.0.02.7]dodeca-3,5-dienetricarbonyliron

The precise molecular structure of the title compound has been determined by single crystal X-ray diffractometry. It consists of a cyclohexadiene ring fused at the 5 and 6 positions to a cyclobutane ring which is in turn fused to a cyclohexane ring. The two six-membered rings are trans to each other with respect to the shared four-membered ring. The Fe(CO)₃ moiety is bound in the usual way to the conjugated diene portion of the cyclohexadiene ring. The feature of greatest interest is the mutual influence of the conformations of the two fused cycloalkane rings, whose intrinsically preferred conformations are mutually incompatible. Under the influence of the fused cyclohexadiene ring the C₄ ring would tend to be planar, while the cyclohexane ring would tend, of itself, to have a chair conformation. The actual result is a compromise, with the C₄ ring being folded by 15° along its diagonal and the C₆ ring having a conformation intermediate between planarity and a chair. Crystallographic data: space group, P2₁, Z = 2. Unit cell dimensions at 3°C are a = 6.176(1), b = 11.307(2), c = 9.781(2) Å and β = 92.89(2)°. A set of 1733 reflections having 2θ(Mo-K_α) < 63.7° and I > σ(I) was refined to convergence (R₁ = 0.055; R₂ = 0.034) with hydrogen atoms refined isotropically and all others anisotropically.