Chemistry September 2002 Vol 51/3 []

CONTENTS & ABSTRACTS

InEnglish. Summaries in Estonian

Proceedings of the Estonian Academy of Sciences.

Chemistry



Volume 51 No. 3September 2002



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

Rein Munter, Sergei Preis,and Enno Siirde

Abstract. Systematization of kinetic data of ozonation processes ofwastewater is discussed. Literary and experimental data on the ozonationkinetics of aqueous solutions and wastewater were analysed. Chemical oxygendemand (COD) was used as the generalized kinetic parameter for ozonationprocesses of water solution and wastewater. To compare the theoreticalconsiderations with experimental results, the rate constants of the ozonationof nitrobenzene and glyoxylic and oxalic acids as well as of real wastewaterfrom aniline dye production were measured. The main conclusion of this study isthat the use of COD as a generalized kinetic parameter for ozonation processesof water solution and wastewater is justified. The rate coefficient  in the equation ofozonation kinetics for water solution with several compounds or wastewater isnot constant and it depends on the formation of compounds richer in oxygen andmore resistant to ozone, i.e. on the COD of the solution. With decreasing CODalso the rate coefficient  decreases. Thereaction order with respect to the COD of the solution was shown to be equal tothe 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 inthe treatment of landfill leachates;148–155

InnaKamenev, Lui Pikkov, and Juha Kallas

Abstract. The objective of the study was to improve an aerobicbio-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 aerobicbio-oxidation combined with catalytic ozonation in a re-circulation system. Itwas shown that both processes are effective in landfill leachate purificationeven at small dosages of consumed ozone.

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

Stereoselectiveone-pot synthesis of a-aminoacid derivatives by four component reactionswith 1-amino-carbohydrates and isocyanides; 156–168

JúliaMária Drábik, Josef Achatz, and Ivar Ugi

Abstract. Fora whole century the chemistry of the isocyanides was a rather neglected part ofchemistry. 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) wasintroduced. A greater variety of products can be prepared by the U-4CR, whichrequires minimal work, and under well selected conditions almost quantitativeyields of products are often formed. The U-4CR can be accomplished by justmixing the educts, and the reaction proceeds under physiology relatedconditions. Since 1995 the products of the U-4CR and its unions with furtherreactions are industrially more often used as the libraries than by othermethodologies. Ways of forming chiral products by the U-4CR have beeninvestigated for many decades, but only recently methods were developed bywhich suitable unprotected 1-amino-carbohydrates and related amines of theU-4CR can be found. In 1986 Kochetkov and co-workers found that1-amino-carbohydrates can be prepared by just mixing carbohydrates and ammoniumhydrogen carbonate. It was found that stereoselective syntheses of chiralproducts can efficiently be performed by the U-4CR of such easily available1-amino-carbohydrates as their chiral amine components. The carbohydrate groupsof its U-4CR products can selectively be removed in yields of up to 46% of itsresulting compounds.

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

Determination of volatile N-nitrosaminesby gas chromatography–mass spectrometry with positive-ion chemicalionization; 169–184

Sergei Jurtchenko, ToomasTenno, Uldo Mölder, and Mari Reinik

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

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