Palladium-catalyzed Mizoroki-Heck reactions were carried out in the presence of calcium carbonate in alcoholic solvents. Under these conditions an efficient preparation of functionalized benzalacetones was developed. The reactions were carried out at room temperature and aerobic conditions, giving the products within several minutes in up to 95% isolated yields. Furthermore, some kinetic investigations, mechanistic insights and considerations are presented.

The role of the potential of zero charge (PZC) and of the potential of maximum adsorption Em during the adsorption of neutral molecules at the electrode surface is not yet well understood. The phase transition of the adsorbed molecules to a condensed state adds further complications. But under certain circumstances this process can be utilized to obtain additional information about the adsorbate system and the electrochemical double layer. On these grounds a new method for the determination of the potential of maximum adsorption in condensed layers is proposed. This method is based purely on a qualitative analysis of the shape of current-time transients, which change their sign at the potential of maximum adsorption and become inverted. From this datum and the corresponding capacity-potential curves of the adsorbate system and of the pure electrolyte one can construct the true charge-potential characteristics of the system and obtain the value of the PZC. This method was applied to the system thymine/mercury/ 0.1 M NaClO4. One result is that in this system the potential of maximum adsorption is a function of the temperature, the pH-value, and the prepolarization potential. This latter result can only be explained in terms of a kinetic argumentation.

Two-dimensional nonfaradaic phase transitions on solid electrodes proceed via nucleation and growth processes. Because of couplings and mutual influences of the condensation process at the surface by the adsorption process of the expanded phase from the bulk to the surface, the modeling of the nucleation and growth process presents a self-consistent problem. An alternative way to solve this problem consists of iterated differentiations of the convolution integral describing the phase transition processes. Together with the balance equation for the expanded phase one gets a closed system of four differential equations, which can be solved numerically for given initial conditions. On the basis of numerical simulations the role of the double-layer charging on the shape of current−time transients is discussed. These predictions are proofed by experimental data, measured in the system thymine/H2O/0.X M NaCl04.

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We report on the adsorption of adenine as well as on the coadsorption of adenine/thymine and uracil/thymine on Au(111). Adenine is chemisorbed in two different states. Mutual interaction between adenine and thymine could be detected only at negative potentials where both molecules are oriented with their plane parallel to the surface. This interaction depends on the concentration of thymine, the pH value, the temperature and the roughness of the surface. At positive potentials where thymine/adenine are oriented perpendicular to the electrode surface, from our experiments no hints to their interaction could be found. Thymine prevents the uracil adsorption and no cocondensation signal between the noncomplementary bases thymine/uracil was found.