Kinetics and Mechanism of a Reaction of Phenylacetylene with Carbon Monoxide and Butanol in Toluene Catalyzed by a Palladium(0) Complex in the Presence of Trifluoroacetic Acid and Triphenylphosphine

The reaction of phenylacetylene with CO and n-butanol in toluene (363 K) catalyzed by the Pd(dba)₂/m(CF₃COOH)/n(Ph₃P) system (dba is dibenzylideneacetone; 2 m 8; 10 n 30) is studied. The initial rate of the main product (butyl 2-phenylpropenoate) buildup is found to depend on the pressure of CO and the concentrations of reactants and system components. The state of the catalyst under reaction conditions is studied in situby IR spectroscopy. A kinetic model is developed based on the experimental results. This model corresponds to the mechanism that resembles the hydride mechanism in the type of main intermediates in the catalytic cycle.     

Non-catalytic Addition of 1,2,4-Triazole to Nucleophilic and Electrophilic Alkenes

Non-catalytic addition of 1,2,4-triazole to vinyl ethers and esters occurs on heating (65-175°C, 4-20 h) to give Markovnikov adducts (yield 30-100%). Electron-deficient alkenes (acrylonitrile, acrylic acid, 4-phenyl-3-buten-2-one) react with 1,2,4-triazole (78-190°C, 4-20 h) to give anti-Markovnikov adducts in yields of 45-83%.     

Industrial Application of Hybrid Sol-Gel Coatings for the Decoration of Crystal Glassware

The coloration of glass via melting techniques presents some unique problems with respect to the reproducibility, toxicology and economics of certain colors, especially if the market demands are highly variable. This is also the case for consumer products such as crystal glass and tableware. Traditionally, the decoration of crystal glasses is performed by laborious manual techniques, which are costly and do not meet modern market requirements. Alternatively, spraying of colored lacquers is a highly flexible and valuable tool for the development of new products. Sol-gel type hybrid coatings provide several advantages compared to conventional organic systems like high abrasion resistance, almost perfect adhesion, refractive index matching and sufficient stability in dishwashing procedures. The solubility of organic dyes in the hybrid matrix is sufficient for intense colors even at rather low layer thicknesses, which on the other hand convey the high brilliance of the base material. The development of transparent, translucent and opaque hybrid coatings for crystal glass has been completed in the last few years and the production of partially coated articles has started recently. The synthesis and properties of the coating material are reviewed and the industrial process and first market results are also outlined.     

Hydrocarbobutoxylation of Phenylacetylene on Palladium Complexes: A Solvent Effect

Data on changes in the activity of the Pd(dba)₂/2TsOH/10Ph₃P (dba is dibenzylideneacetone) and PdCl₂(Ph₃P)₂/8Ph₃P catalytic systems in the reaction of phenylacetylene with CO and n-butanol under the action of a solvent (aromatic hydrocarbons, chloroalkanes, ethers, esters, ketones, and dipolar aprotic media) are presented. The differences found in the response of either of the systems to changes in the properties of the medium are discussed in terms of a scheme of the catalytic cycle of reaction. It is noted that activity does not correlate with the physicochemical characteristics (polarity, basicity, and electron-acceptor ability) of solvents.     

STUDIES OF ADHESION OF METAL PARTICLES TO SILICA PARTICLES BASED ON ZETA POTENTIAL MEASUREMENTS

The zeta-potentials of silica, copper, platinum and gold particles have been measured as a function of pH. The isoelectric points were found to be at pH 3.0, 5.8, 3.0 and 3.5, respectively. In the pH range 3.0 to 5.8 copper and silica particles are oppositely charged and accordingly the coating of silica with copper particles could be demonstrated. In the case of gold and platinum the sign of the charge is such that direct adhesion to silica particles cannot be expected and this was also demonstrated in the case of platinum.