Chlorinated arene hydrocarbons

Aerobic degradation of chlorinated arene hydrocarbons, including the important group PCBs, and chlorobenzoates that are produced from them as metabolites, is generally initiated by dihy-droxylation of the rings to dihydrodiols followed by dehydrogenation to catechols. Halide may be lost simultaneously and for 2-halogenated benzoates, both halide and carboxyl. Salient aspects are summarized, and attention drawn to selected aspects of enzyme inhibition. 

Monooxygenase systems are sometimes involved in the degradation of toluene (Section 6.2.1) and plausibly in the transformation of aromatic compounds to arene oxide intermediates (Chapter 4, Sections 4.2.3 and 4.4.1.1, and in Sections 6.2.2 and 6.3.1.2). There is a complex relation between toluene monooxygenase activity and the degradation of chlorinated hydrocarbons. 

A second group of specific xenobiotics in Teltow Canal sediments are halogenated aromatics. Several chlorinated and brominated mono- and diaromatic hydrocarbons were detected in high amounts within the extractable organic matter as reported previously (Schwarzbauer et al. 2001). The halogenated arenes identified in the hydrolysis extracts included mono- and dichlorinated naphthalenes 12+13. mono- and dihrominated naphthalenes 14+15. tetra- to hexachlorinated biphenyls (PCB) and 2,4,6-tribomoaniline. The peak pattern of the chlorinated naphthalenes was similar to the congener distribution in technical mixtures e.g. Halowax 1000 (Falandysz 1998). 

In this context the already extensive work of Rein-houdt and coworkers on the preparation and characterization of self-assembled monolayers of resorcin [4] arenes [11-13], calixarenes [14], and even carceplexes [15] constitutes one of the most important efforts to develop this field. Self-assembled monolayers of resorcin [4] arenes exhibit selective adsorption properties for small chlorinated hydrocarbons in the gas phase [13], although serious questions have been raised as to how much the observed selectivity has to do with the presence of molecular cavities in the monolayer assembly [16]. Davis and Stirling have also reported on the self-assembly of similar compounds and demonstrated the formation of multilayers [17,18]. The extensive and very systematic work of Crooks, Ricco and co workers on the development of devices for the detection of volatile organic compounds deserves special mention [19]. Recently, Crooks and coworkers have taken a very interesting turn in their work, demonstrating that monolayer-attached dendrimeric structures exhibit remarkable selectivity for the sorption of gas-phase molecules [20,21]. 

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