Kalorimetrische bestimmung der komplexstabilität von additionskomplexen des SbCl5 mit substituierten acetessigsäureaniliden

The formation enthalpies of SbCl₅ complexes with various substituted aceto-acetanilides were measured by solution calorimetry. The enthalpy values are influenced by the kind and the position of substituents at the phenylring of the aceto-acetanilide. A correlation between the enthalpy values and the position of the amidl-valence vibration is pointed out.     

Hydrolysis of glycosides with microgel catalysts

A dormant macromolecular catalyst was prepared by polymerization of an aqueous styrene-butyl acrylate miniemulsion in the presence of a new polymerizable pentadentate ligand. The catalyst was activated by binding Cu(II) ions to the ligand site and then explored for its ability to hydrolyze glycosidic bonds in alkaline solution. The performance was correlated to the catalytic activity shown by low molecular weight analogs. A turnover rate of up to 43 × 10(-4) min(-1) was previously observed for cleavage of the glycosidic bond in selected p-nitrophenylglycosides with a binuclear, low molecular weight catalyst; by contrast, the same reaction is more than 1 order of magnitude faster and has a turnover rate of up to 380 × 10(-4) min(-1) when using the prepared macromolecular catalyst. The catalyzed hydrolysis is about 10(5)-fold accelerated over the uncatalyzed background reaction under the provided conditions, while a significant discrimination of the α- and β-glycosidic bond or of the galacto- and gluco-configuration in the sugar moiety in the glycoside substrates is not observed.     

Effect of water on the catalytic oxidation of catechols

A dinuclear copper(II) complex derived from a new water-soluble pentadentate Schiff base backbone ligand has been prepared and characterized in solution and in the solid state. The complex has been found to accelerate the aerobic oxidation of 3,5-di- tert-butylcatechol (DTBC) into 3,5-di- tert-butylquinone (DTBQ) by 5 orders of magnitude, compared to the background reaction in aqueous methanol (k(cat)/k(non) = 160,000) at 30 degrees C. The transformation of the model substrate is considerably slower in pure methanol (k(cat)/k(non) = 60,000) under otherwise identical conditions. In-depth investigation of the catalytically active species revealed different structures for the copper(II) complex in methanol and in methanol/water mixtures.