Zum Zusammenhang zwischen Ligand-Acidität und Metallkomplex-Stabilität: Abnehmende Stabilität bei zunehmender Basizität

The increase of the stability of metal ion complexes with decreasing basicity of the ligands within different series is discussed with the help of the equation of IRVING & ROSSOTTI [4] [12] and explained in terms of the free energy G of the complexes.     

Untersuchungen zur Acidität und Basizität von Alkoxysilylaminen

Investigations on Acidity and Basicity of Alkoxysilylamines Relative acidity and basicity have been determined for silylamines of the type (RO)₃Si? NH? X (R = Et, n. Pr, i-Pr, s-Bu, t-Bu; X = n-Bu, Ph, p-MeO? C₆H₄, p-Cl? C₆H₄, p-NO₂? C₆H₄) by IR, NMR, and potentiometric investigations. The position of the ν_NH band, the shift of this band in tetrahydrofuran and the chemical shift of NH-proton-NMR signal show a significant increase of NH acidity with increasing electron attracting effect of R and X. The shift of deuteriochloroform ν_CD band at association with aminosilanes and the results of potentiometric investigations confirm the low basicity of these compounds and the decrease of the basicity with increasing acidity.     

Untersuchungen zur Acidität und katalytischen Spaltaktivität dekationisierter NaY-Zeolithe

Investigation on Acidity and Catalytic Activity of Deep-Bed Calcinated Zeolites NH₄ NaY NMR and infrared techniques are applied to decationated zeolites NaY to study Brönsted acidity. The results are compared with measurements of catalytic activity and crystallinity of this zeolites. The number of OH groups which are able to form a pyridinium ion (PyH⁺) increases with increasing exchange degree and with increasing temperature of the sample. The rate of pyridinium ion formation as an equivalent of Brönsted acidity and the catalytic activity increase similarly with increasing exchange degree up to such values where a loss of crystallinity occurs.     

Die Acidität kristalliner Kieselsäuren

Acidity of Crystalline Silicic Acids Crystalline silicic acids are strong solid acids with surface acidities ranging from H₀ < ?3 (H₂Si₁₄O₂₉ · 5.4 H₂O) to H_O ≈? 2.3(H₂Si₂O₅), measured with Hammett indicators. Thermal dehydration reduces the surface acidity to 2.3–3.3 only. The high acidity probably results from regular, extended hydrogen bonding systems including the surface water molecules. By disturbing the regular array of hydrogen bonds the acidity decreases to H_o = 5–6 which is considered to be the characteristic acidity of isolated silanol groups not involved in regular hydrogen bonding systems. The surface acidity is not directly related to the ease with which the protons are exchanged by alkali ions because of the cooperative nature of the cation exchange.