Kinetic studies in various media on some hydrogenation reactions catalyzed by polymer-anchored RhCl(PPh3)3

A study has been made of the hydrogenation of cyclohexene, 1-hexene and styrene at atmospheric pressure catalysed by RhCl (PPh₃)₃ supported on styrene-divinylbenzene copolymers with 1%, 2% and 4% cross linking. The dependence of the hydrogenation rate on the concentration of the olefin, the amount of catalyst, and the nature of the solvent was investigated. The hydrogenation rate is lower than for homogeneous catalysis but the dependence of the rate on the examined parameters is similar. The ratio between the rates for 1-hexene and cyclohexene is higher than that in the homogeneous phase. This increase in selectivity may due to steric hindrance around the active sites of the resin. The solvent effects revealed that the hydrogenation rate also depends on the degree of swelling of the resin.     

Adsorption of lignosulphonates on polystyrene latex particles from aqueous solution and flocculation of the dispersions by electrolytes

Summary The adsorption isotherms of lignosulphonates with various degrees of sulphonation (0.5, 1,0, 2.0 and 4.0 moles per 840 unit weight of lignin) were measured on polystyrene latex particles from aqueous solution at 25 °C. The results showed that the lignin with the lowest degree of sulphonation gave the highest adsorption. The lignin with 1.0 and 2.0 degrees of sulphonation gave similar adsorption which was lower than that obtained with the half sulphonated lignin. However, further increase in degree of sulphonation resulted in an increase in the adsorption.Adsorption layer thickness measurements showed that the lignosulphonate with half degree of sulphonation gave thicker layers than that with 2.0 moles sulphonation. Increasing electrolyte (NaCl and CaCl,) concentration resulted in a decrease in the adsorbed layer thickness. Microelectrophoresis at 25 °C, showed only small differences in the zeta potential as a function of degree of sulphonation. Addition of electrolytes (KCl, Na₂SO₄ and CaCl₂) showed a reduction in the zeta potential. Flocculation by salts of various valence types, namely KCl, Na₂SO₄ and CaCl₂ showed that the critical flocculation concentration (C.F.C.) decreases in the order KCl > Na₂SO₄ > CaCl₂. The change in degree of sulphonation had only a marginal effect on the C.F.C.

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Zusammenfassung Die Isothermen der Adsorption von Lignosulfonaten mit verschiedenen Sulfonierungsgraden (S = 0,5, 1,0, 2,0 und 4,0 Mole pro 840 Gewichtseinheit des Lignins) an PolystyrolLatex-Teilchen in wäßriger Lösung wurden bei 25 °C gemessen. Hiernach wird Lignin mit den niedrigsten S-Werten am stärksten adsorbiert. Lignine mitS = 1,0 und 2,0 zeigen ähnliche Adsorption; sie ist aber kleiner als die fürS = 0,5. Mit weiter steigendemS nimmt die Adsorption zu.Aus der Messung der Dicke der Adsorptionsschicht folgt, daß fürS = 0,5 größer als fürS = 2,0 ist. Bei wachsendem Zusatz von NaCl oder CaCl₂ fällt ab. Nach Mikroelektrophorese-Messungen bei 25 °C hängt das -Potential nur wenig vonS ab. fällt durch die Gegenwart von KCl, Na₂SO₄ oder CaCl₂ ab. Mit den gleichen Salzen erfolgt eine Ausflockung, wobei die kritische Flockungskonzentration CFC in der Reihenfolge KCl, Na₂SO₄, CaCl₂ abnimmt; CFC ändert sich nur wenig mitS.

     

Electronic interactions in aromatic an heteroaromatic two-ring systems

The chemical shifts of the methyl protons ( ) in the PMR spectra and the integral intensities (A^1/2) of the band of the symmetrical CH stretching vibration of the methyl group in the IR spectra were measured for an extensive series of methyl derivatives of aromatic and heteroaromatic compounds including 3-, 4-, 5-, and 6-substituted 1- and 2-methylnaphthalenes, 4-, 5-, 6-, and 7-substituted 2-methylquinolines, and 5- and 6-substituted 2-methylbenzothiazoles, as well as a number of two- and three-ring systems that do not contain substituents. The changes in the chemical shifts are interpreted with allowance for two principal contributions: the contribution from the ring currents and the contribution from the changes in the electron densities (q) on the H and C atoms of the methyl group. The fact of the existence of a linear relationship between the corrected (for the ring current) values and the calculated (by the CNDO/2 method) electron charges q_C and q_H (the latter plays the dominant role) indicates that the electronic effects of the substituent make the principal contribution to the changes in the shielding constants of the protons of the methyl group in most of the investigated compounds. Similarly, the charges on the H and C atoms of the methyl group convey the trend of the integral intensities of the IR bands, thereby confirming the primarily electronic nature of the effects of structural factors on the A^1/2 values.See [2] for communication 2.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 390–396, March, 1979.     

Choice of preferred stationary phases for gas chromatography. Part II

Summary The regularities of changes of the polarity factors with the composition of mixed stationary phases are discussed. Values of the polarity factors of active solids, partitioning liquids and also colloidal stationary phases are compared. Part I: ref. [1].     

Einige Gesetzmäßigkeiten der spontanen Umwandlung der Wasserstofform des Montmorillonits in die Aluminium-form

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