CONTENTS & ABSTRACTS

In English. Summaries in Estonian

Proceedings of the Estonian Academy of Sciences.

Chemistry

Volume 51 No. 3 September 2002

Characterization of ozonation processes by oxygen demand of compounds; 139–147

Rein Munter, Sergei Preis, and Enno Siirde

Abstract. Systematization of kinetic data of ozonation processes of wastewater is discussed. Literary and experimental data on the ozonation kinetics of aqueous solutions and wastewater were analysed. Chemical oxygen demand (COD) was used as the generalized kinetic parameter for ozonation processes of water solution and wastewater. To compare the theoretical considerations with experimental results, the rate constants of the ozonation of nitrobenzene and glyoxylic and oxalic acids as well as of real wastewater from aniline dye production were measured. The main conclusion of this study is that the use of COD as a generalized kinetic parameter for ozonation processes of water solution and wastewater is justified. The rate coefficient in the equation of ozonation kinetics for water solution with several compounds or wastewater is not constant and it depends on the formation of compounds richer in oxygen and more resistant to ozone, i.e. on the COD of the solution. With decreasing COD also the rate coefficient decreases. The reaction order with respect to the COD of the solution was shown to be equal to the reaction order with respect to the pure compound.

Key words: theoretical oxygen demand, ozonation rate constant, wastewater, rate coefficient, chemical oxygen demand.

Aerobic bio-oxidation combined with ozonation in the treatment of landfill leachates; 148–155

Inna Kamenev, Lui Pikkov, and Juha Kallas

Abstract. The objective of the study was to improve an aerobic bio-oxidation process of landfill leachates. Two processes were studied: aerobic bio-oxidation combined with ozonation in a re-circulation system (repetitive sequential aerobic bio-oxidation–ozone treatment) and aerobic bio-oxidation combined with catalytic ozonation in a re-circulation system. It was shown that both processes are effective in landfill leachate purification even at small dosages of consumed ozone.

Key words: landfill leachate, aerobic bio-oxidation, ozonation, combined process.

Stereoselective one-pot synthesis of a-aminoacid derivatives by four component reactions with 1-amino-carbohydrates and isocyanides; 156–168

Júlia Mária Drábik, Josef Achatz, and Ivar Ugi

Abstract. For a whole century the chemistry of the isocyanides was a rather neglected part of chemistry. A new era began in 1958 when the isocyanides became well available, and a year later the four component reaction of the isocyanides (U-4CR) was introduced. A greater variety of products can be prepared by the U-4CR, which requires minimal work, and under well selected conditions almost quantitative yields of products are often formed. The U-4CR can be accomplished by just mixing the educts, and the reaction proceeds under physiology related conditions. Since 1995 the products of the U-4CR and its unions with further reactions are industrially more often used as the libraries than by other methodologies. Ways of forming chiral products by the U-4CR have been investigated for many decades, but only recently methods were developed by which suitable unprotected 1-amino-carbohydrates and related amines of the U-4CR can be found. In 1986 Kochetkov and co-workers found that 1-amino-carbohydrates can be prepared by just mixing carbohydrates and ammonium hydrogen carbonate. It was found that stereoselective syntheses of chiral products can efficiently be performed by the U-4CR of such easily available 1-amino-carbohydrates as their chiral amine components. The carbohydrate groups of its U-4CR products can selectively be removed in yields of up to 46% of its resulting compounds.

Key words: one-pot reaction, four component reaction of isocyanides, Ugi reaction (U-4CR), 1-amino-carbohydrates, stereoselectivity, a-aminoacid derivatives, selective cleavage.

Determination of volatile N-nitrosamines by gas chromatography–mass spectrometry with positive-ion chemical ionization; 169–184

Sergei Jurtchenko, Toomas Tenno, Uldo Mölder, and Mari Reinik

Abstract. A gas chromatography–mass spectrometry method was developed and optimized for the determination of volatile N-nitrosamines in smoked meat products. Five volatile N-nitrosamines (N-nitrosodimethylamine, N-nitrosodiethylamine, N-nitrosopiperidine, N-nitrosopyrrolidine, and N-nitrosodibutylamine) were separated by gas chromatography and differentiated by positive-ion chemical ionization using two different reagent gases – methane and ammonia. The HP 6890 Plus GC/HP 5973 MSD with positive-ion chemical ionization option was used in the selected ion-monitoring mode. For cleaning the sample solid-phase extraction was used. The detection limit for N-nitrosamines using positive-ion chemical ionization was 0.01 ppb with about 70–80% recovery.

Key words: volatile N-nitrosamines, positive-ion chemical ionization, gas chromatography, mass spectrometry, food.