Search

Model experiments were carried out on the reaction behaviour of benzene, phenol and phenylalanine during chlorination with NaOCl in aqueous solution. The influence of the pH-value, concentration, reaction time and UV-light were also determined. These experiments were conducted under conditions similar to chlorination of water and the reaction products were identified by capillary GC and GC/MS. All chlorinated isomers of benzene including HCB, formed by chlorination of benzene, were identified and quantified. However, monochlorobenzene was the major reaction product (in mu g/l-concentrations). The chlorinated organic substances formed by the reaction of phenol with NaOCl were determined quantitatively. Phenylalanine/NaOCl reaction lead to the formation of 22 chlorinated organic compounds. Thirteen of these were identified and quantified. Under the influence of UV-light, the reaction of benzene/NaOCl formed primarily higher chlorinated propane derivatives, chlorinated phenols and octachlorocyclohexandiene derivatives. Similar results were obtained with the reaction of phenol/NaOCl and the phenylalanine/NaOCl. The formation of chloroform during all these reactions were determined quantitatively. Chemosphere

Brominated aromatic compounds like brominated benzenes, diphenylethers and dibenzodioxins adsorbed on the surface of fly ash from a municipal waste incininerator give mixed brominated/chlorinated und completely chlorinated aromatic compounds. These consecutive halogenation-dehalogenation reactions proceed by a nucleophilic mechanism, which is favoured by a high concentration of chloride on the fly ash. Results of kinetic and stereoselective behavior of these reactions will be discussed. The relevance of these results for PCDD/PCDF formation from bromine precursors in municipal waste incinerators will be discussed.

Thirty organic compounds were selected to investigate their chloroform formation characteristics during chlorination with sodium hypochlorite at pH-values 7.0 and 8.0. These experiments were conducted under conditions similar to those applied on the chlorination of raw water. The results indicated that the chloroform concentrations occurred by the all tested compounds was in the ppm range. The maximum levels of chloroform (11 - 13 mg/l) were determined during the reaction of resorcinol and phloroglucinol at PH-value 8.0. (C) 1999 Elsevier Science Ltd. All rights reserved Chemosphere

Zusammenfassung Increasing attention has been given for some years now to the occurrence of halogenated organic compounds in stack gases and fly-ash incineration plants. Upon combustion of an organic matrix containing polyethylene and with sodium chloride as the only chlorine source, it could be demonstrated that chloroaromatics are formed. Thus, not only organochlorines present in the material burnt but also inorganic chlorine may be a source of organochlorine emissions.

Bei der sensibilisierten Bestrahlung von 4,5,6,7,8,8-Hexachlor-2,3,3a,4,7,7a-hexahydro-4,7-methano-1,3- indendicarbonsaure-dimethylester (1) konnte gezeigt werden, das neben der fur diese Substanzklasse typischen πσ2σ-Reaktion auch intramolekular verlaufende reversible Wasserstoffverschiebungen moglich sind. Tieftemperaturbestrahlungen von 1 fuhrten zu dem Ergebnis, das das intramolekulare Wasserstofftransferprodukt 5 unterhalb −30°C als einziges Photoprodukt entsteht. Die Photoisomerisierungsprodukte 2, 3 und 4, die erst ab −30°C in einer πσ2σ-Reaktion gebildet werden, deuten darauf hin, das die Reaktion uber die biradikalischen Zwischenstufen 2a, 3a und 4a ablauft. Bei der Bestrahlung von 5 wurden die Ausgangsverbindung 1 und die Photoisomerisierungsprodukte 2, 3 und 4 erhalten. The Photoreversible Hydrogen Shift: A Competitive Reaction for the πσ2σ Isomerization of Bridged Chlorinated Hydrocarbons In the sensitized irradiation of dimethyl 4,5,6,7,8,8-hexachloro-2,3,3a,4,7,7a-hexahydro-4,7-methano-1,3- indenedicarboxylate (1) intramolecular reversible hydrogen shifts are possible besides the πσ2σ reaction typical for this class of substances. Irradiation of 1 at low temperatures showed that below −30°C 5 is the only photoproduct. The photoisomerization products 2, 3, and 4, which arise by a πσ2σ reaction only above −30°C, suggest that the reaction proceeds via the biradical intermediates 2a, 3a, and 4a. The parent compound 1 and the photoisomerization products 2, 3, and 4 are obtained by irradiation of 5.

The reaction behaviour of benzene in aqueous solution (ppm-concentrations) during chlorination with NaOC1 was studied. The dependence of chlorination upon the pH-value was determined quantitatively. All isomeric chlorobenzenes were formed including hexachlorobenzene. Thus, water chlorination can be regarded as another source of environmental hexachlorobenzene contamination.

The vapour pressures of nine organic chemicals adsorbed on silicagel were determined by a method which can be standardized. They were compared with those of the non-absorbed, free compounds (range 6 × 10 −3 – 7 × 10 4 Pa).

Upon heating of 2,4,5-T to 600°C, 2,3,7,8-TCDD is formed with a yield of 0,2 %. At 800°C, the formation of TCDD decreases by a factor at 200. Tormona 80 ® an ester at 2,4,5-T yields 200 ppm TCDD at 600°C and 3 ppm at 800°C. The highest formation rate is observed for 2,4,5-Trichlorophenol (0,5 % at 600°C). During the thermolysis of 2,4-D, γ-Hexachlorocyclohexane, 2,4,6-Trichlorophenol, Pentachlorophenol and Clophen A 40. 2,3,7,8-TCDD could not be detected.

4-Chloroaniline reacted with catechol to form 4,5-bis(4-chlorophenylamino)3,5-cyclohexadiene-1,2-dione. The reaction was catalyzed mainly by tyrosinase or pyrolusit.

The formation of cyano group-containing polycyclic aromatic compounds (cyanoarenes) and nitrogen-containing aromatic compounds (azaarenes) during combustion processes is described. The experiments were carried out by combustion of nitrogen containing polymers (nylon 6, polyacrylonitrile and polyamide) in a combustion chamber ,to simulate combustion processes of waste incineration plants. The result from experiments, in which only one nitrogen containing polymer was burnt, showed the formation of several cyanoarenes. We conclude that during combustion processes in which hydrogen cyanide is formed, air pollution by cyanoarenes and azaarenes (in ppb or ppm concentrations) may occur.