Synthesis,Characterization of Cr Doped TeO2 Nanostructures and its Application as EGFET pH Sensor

In the present work, Cr doped tellurium dioxide nanostructures (CTO NS)(1 wt %, 6 wt %, 8 wt % and 12 wt %) synthesized by co precipitation method and characterized by CV, UV-Visible, SEM, XRD, XPS spectroscopic analysis. Electron beam deposited thin film of CTO NS having 12 wt % of Cr exhibited EGFET-pH sensitivity of 62.03 mV/pH at 250 °C in buffer solutions of pH 6–12, linearity 0.9345, drift rate of 1.12 mV/h and deviation of 0.01145 as compared with 1 wt %, 6 wt % and 8 wt % of CTO NS.     

Die Ringinversions-Barriere in [2.2]Metacyclophan

From racemization studies on optically active [2.2]metacyclophanes substituted in position 4, the parameters of activation for the inversion of the tenmembered ring were found to be: G ₄₂₃ =31.5 kcal/mole, H =27.5 kcal/mole and S =–10 Cl/mole.Racemization does not occurvia bond forming or breaking; the value for the inversion barrier is not affected by substituents in position 4 and therefore corresponds to the value of unsubstituted [2.2]metacyclophane, whereas substituents in the bridge exert a distinct influence. These results can easily be explained on the basis of the isoconformational concept.

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Mit 5 Abbildungen

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Herrn Prof. Dr.O. Hoffmann-Ostenhof mit besten Wünschen zum 60. Geburtstag gewidmet.     

Ein biologischer Vergleich zwischen Benzol und Pyridin in kondensierten Ringsystemen

The synthesis of imidazo[4,5-b]pyridines and of [1,2,4]-triazolo[1,5-a]pyridines is described, and their biological activity in relation to the standard antiviral substance, 2-(α-hydroxybenzyl)benzimidazol, is discussed.     

Über die Entstehung von Oligoanthrylen bei der milden Sulfonierung von Anthracen

The sulfonation of anthracene yields a variety of products and byproducts by different reaction paths depending on the reaction conditions. While trying to reduce the number of products formed by sulfonation under mild conditions, a new reaction was found: under certain sulfonation conditions anthracene is not sulfonated but reacts to form oligoanthrylenes. The highest average molecular weight of a fraction, insoluble in benzene, is about 3,000.     

Synthese neuer Aminofluorsilane,sowie Alkoxylierung von Bis (trimethylsilyl)-amino-fluorsilanen

The reaction of aminofluorsilanes of the type (R=H,F) (Me ₃Si)₂N?SiF₂R with two moles of ammonia, or of a mono- or dialkylamine, yields the corresponding amino-compounds, e.g. (Me ₃Si)₂N?Si(F)R?NH₂, (Me ₃Si)₂N?Si(F)R?NHR′ and (Me ₃Si)₂N?Si(F)R?NR₂′ (R′=Me, Et). Analogous products are obtained by reaction of the aminofluorosilanes with lithium salts of amines with bulky organic substituents in a 1 : 1 molar ratio. Alkoxy- and aryloxyaminofluorosilanes are prepared by the reaction of sodium alcoholates and sodium phenolate with (Me ₃Si)₂N?Si(F₂)R (R=H, C₂H₃, C₂H₅, C₆H₅). The i.r.-, mass-,¹H- and¹⁹F-NMR spectra of the above compounds are reported.     

Ion exchange removal of calcium carbonate and gypsum from mineral material prior to determination of cation exchange capacity using89Sr++

Summary The aim of the present work was to show that ion exchange resins can be used to remove sparingly and slightly soluble salts from calcareous and gypseous soils, which may otherwise cause serious errors in the determination of cation exchange capacity. It was shown that CaCO₃ and CaSO₄-2H₂O can be removed from a mixture with montmorillonite(Ca++) by a mixed bed resin. After resin treatment of the mixture its C.E.C. as retained Sr⁺⁺ corresponds approximately to the C.E.C. for pure montmorillonite within certain limits. Use of an anion exchange resin alone for removing these salts, however, gave an Sr⁺⁺ retention well below the C.E.C. for the mineral. It was assumed that this results from the blocking of exchange sites by resin particles.

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Zusammenfassung In kalkhaltigen und gipshaltigen B?den st?ren CaCO₃ und CaSO₄-2H₂O die Bestimmung des Kationenaustauschverm?gens. In der vorliegenden Arbeit wird gezeigt, da? Salze wie CaCO₃ und CaSO₄-2H₂O aus Mischungen mit Ca-Montmorillonit durch Ionenaustauscher herausgel?st werden k?nnen. Als Ionenaustauscher müssen jedoch Mischbettaustauscher verwendet werden; Anionenaustauscher allein liefern bei einer anschlie?enden Bestimmung des Kationenaustausches mit Sr⁺⁺ falsche Werte. Die angegebene Methode erscheint vor allem für die Untersuchung von B?den wichtig zu sein.

     

Die Kristallstruktur von Si5O[PO4]6

The crystal structure of Si₅O[PO₄]₆ has been determined and refined by least-squares, using three-dimensional X-raydata fromWeissenberg photographs: space group R 3;a=7.86₉ andc=24.13₈ Å;Z=3; 418 independent reflections;R=6.0%. The crystal structure consists of isolated [SiO₆] octahedra and [Si₂O₇] groups which are linked by [PO₄] tetrahedra forming a three-dimensional network. The average interatomic distances are: Si[6]?O=1.76₈, Si[4]?O=1.60₇ and P?O=1.52_i Å. The compound is isotypic with Ge₅O[PO₄]₆.     

A CNDO-MO calculation of VCl4

The electronic structure of the tetrahedral molecule VCL₄ is investigated within the CNDO-MO approximations. The metal and ligand valence orbitals, 3d, 4s, 4p; and 3s, 3p; respectively, have been systematically varied in an attempt to minimize the total energy; “optimum” V 4s(χ₄ = 1.10) and 4p(d ³ p ²) orbitals have been established, but V 3d(d ⁿ ) and Cl(-δ) valence orbitals are only seen to favor lower energy for expanded orbitals. Since determining the one-electron molecular orbital level which is occupied by the vanadium lone electron is a major aspect of this investigation, all calculations have been performed in triplicate: calculations assuming the unpaired electron occupies the 3a ₁, 2 _e and 4t ₂ molecular orbital (ground state electronic configurations² A ₁,² E, and² T ₂, respectively). The Hartree-Fock equations have been solved by Roothaan's SCF method for open shells, but off-diagonal multipliers between filled and partly filled molecular orbitals of the same symmetry have been neglected. As a qualitative estimate of the error introduced by this simplification, the pertinent overlap integrals between the eigenfunctions from calculations for the three possible configurations,² A ₁,² E, and² T ₂, are investigated as functions of the component 3d(d ⁿ ) and Cl(-δ) valence orbitals. The overlap integrals from the relevant² A ₁ and² T ₂ calculations are reasonably small, but the neglect of off-diagonal multipliers in calculations on the² E state is found to be a poor approximation. An ordering of the non-filled molecular orbitals in VCl₄ of 4t ₂ < 3a ₁ < 2e < 5t ₂ seems most consistent with the numerous calculations. This suggested ground state electronic configuration of² T ₂ introduces new aspects to the consideration of a (dynamic) Jahn-Teller effect in VCl₄. Experimental data pertinent to the electronic structure of VCl₄ has been briefly summarized, but unfortunately it is inadequate to confirm or deny the present calculations.