Oxidative Coupling as a Cause of Substituent Release from Aromatic PollutantsEPA Grant Number: R823847
Title: Oxidative Coupling as a Cause of Substituent Release from Aromatic Pollutants
Investigators: Bollag, Jean-Marc , Dec, Jerzy
Institution: Pennsylvania State University
EPA Project Officer: Hiscock, Michael
Project Period: September 1, 1995 through October 1, 1998 (Extended to September 30, 1999)
Project Amount: $425,000
RFA: Exploratory Research - Chemistry and Physics of Water (1995) RFA Text | Recipients Lists
Research Category: Water , Land and Waste Management , Engineering and Environmental Chemistry
The objective of this project is to establish that the release of substituents through dehalogenation, decarboxylation, demethoxylation, demethylation, dehydroxylation, and dehydrogenation of phenolic and anilinic compounds is caused by oxidative coupling reactions. Recent studies indicated that the stoichiometric patterns of the release were in agreement with the free radical mechanism of oxidative coupling. According to this mechanism, release of a substituent may occur only if the unpaired electron of a free radical involved in coupling is located at the substituted aromatic carbon. Under certain conditions, substituents can also be released from the formed o-quinones during nucleophilic attack by phenoxide ions. Since the release patterns will reveal the sites on substrate molecules at which the coupling takes place, the research may be of great importance for elucidating reaction pathways involving oxidative coupling.
The investigation will be completed in three stages: (1) the determination of the rates and stoichiometry of substituent release under different reaction conditions; (2) the development of methods to distinguish between degradative and non-degradative substituent release and to assess their effect on the overall transformation of substrates in the environment; (3) the determination of the pathways of the studied processes and the identification of the formed products.
The non-degradative release of substituents from aromatic compounds constitutes a new and as yet unexplored aspect of oxidative coupling reactions. It is expected that research in this area will advance the understanding of such significant environmental and industrial processes as humification, delignification, binding of aromatic chemicals to soil, and polymerization of pollutants in aqueous environments.