Preparation of supported platinum catalysts from tetrakis (Triphenylphosphine) platinum by impregnation

Pt[P(C₆H₅)₃]₄ has been applied for preparation of Pt/C and Pt/Al₂O₃ catalysts. The highest hydrogenation activity exhibited the catalysts prepared using alumina support. Activity of these catalysts is higher compared with those obtained from Pt(NH₃)₄Cl₂.

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Pt[P(C₆H₅)₃]₄ Pt/C Pt/Al₂O₃. , , . , Pt(NH₃)₄Cl₂.

     

HPLC fractionation and structural dynamics of humic acids

Different soil extracted humic acids as well as a commercial humic acid sodium salt were fractionated by HPLC. An almost complete recovery could be achieved for the dissolved material. All humic samples show a typical chromatogram of at least five fractions. The separation of humic substances is influenced by an altered hydrophobicity due to changes in the tertiary structure. Three fractions were further investigated by Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy and by HPLC/HPLC separation. DRIFT spectroscopy provided data on the primary structure, whereas HPLC/HPLC results gave insight into the secondary and tertiary structure and their changes. Received: 18 June 1996 / Revised: 9 October 1996 / Accepted: 12 October 1996     

HPLC fractionation and structural dynamics of humic acids

Different soil extracted humic acids as well as a commercial humic acid sodium salt were fractionated by HPLC. An almost complete recovery could be achieved for the dissolved material. All humic samples show a typical chromatogram of at least five fractions. The separation of humic substances is influenced by an altered hydrophobicity due to changes in the tertiary structure. Three fractions were further investigated by Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy and by HPLC/HPLC separation. DRIFT spectroscopy provided data on the primary structure, whereas HPLC/HPLC results gave insight into the secondary and tertiary structure and their changes. Received: 18 June 1996 / Revised: 9 October 1996 / Accepted: 12 October 1996     

Prediction of Properties of Soil Humic Substances from FTIR Spectra using Partial Least Squares Regression

Abstract

Humic substances (HS) play a key role in aquatic and terrestrial ecosystems. The understanding of the ecological functionalities of HS is based on the analysis of their properties, which is normally a very time-consuming procedure. Therefore we tested the possibility to apply the partial least squares regression (PLSR) method in connection with the mid infrared Fourier transform (FTIR) spectra of a series of soil humic substances for the prediction of different HS properties. The results with humic acid (HA) and fulvic acid (FA) fractions of soil HS from different environments show the possibility to predict several properties of an unknown soil HA with satisfying reliability above all the elemental composition.     

Reduzierte Zustandssummenverhältnisse isotoper Moleküle auf quantenchemischer Grundlage: VI. Mitt. MINDO/3-MO-Berechnungen von Radikalkationen

Anhand der graphischen Darstellung ihrer Temperaturabhängigkeit werden die reduzierien (D/H)- und (¹³C/¹²C)Zustandssummenverhältnisse von Pentan, Cyclohexan und Cyclohexen mit denen der entsprechenden Radikalkationen verglichen. Die Werte für die Radikalkationen liegen generell niedriger als für die neutralen Moleküle und zeigen in einigen Fällen eine stärkere strukturell bedingte Differenzierung.

The reduced partition function ratios concerning the H/D- and ¹²C/¹³C.substitutions of pentane, cyclohexane, and cyclohexene are compared with those of the corresponding radical cations by means of graphs of their temperature dependence. The values for the radical cations are generally lower than for neutral molecules and show in some cases greater differences for structurally different positions of isotopic substitution.     

Schwingungsverhalten von dimethylsulfid,dimethyl-sulfoxid,dimethylsulfon und den entsprechenden per-deuterierten verbindungen: 2. Mitt. normalkoordinatenbehandlung

Normal coordinate calculations on dimethyl sulphide, dimethyl sulphoxide, dimethyl sulphone and their perdeuterated derivatives have been carried out. The GF-matrix method of Wilson was applied using the general harmonic valence force field. The calculated frequencies of the normal vibrations agree satisfactorily with the corresponding values obtained from the spectra. In addition the potential energy distributions were calculated and discussed. It has been found that the potential energy of the symmetric SO valence vibration of dimethyl sulphone is located only partly in the SO bond, like in dimethyl sulphoxide.