Chloroaromatic compounds

At 550—600°C, hydrogen sulfide reacts with chloroaromatic compounds forming thiophenols and diaryl sulfides (115) ... 

Vandenbergh PA, RH Olsen, JE Colaruotolo (1981) Isolation and genetic characterization of bacteria that degrade chloroaromatic compounds. Appl Environ Microbiol 42 737-739. 

Kester [5] has discussed the application of the purge and trap gas chromatographic method discussed in section 5.1.1.3 to the determination of chloroaromatic compounds such as chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, bromobenzene in soils. Following methanol extraction of the soil the extract is gas purged and the purge gases trapped on a Tenax 1 silica gel-charcoal trap followed by thermal desorption from the trap and examination by gas chromatography and/or mass spectrometry. 

Fortunately, some microbial species are capable of degrading such chemicals [124-126]. This ability is used for the development of microbial sensors for chloroaromatic compounds (see Table 12). 

Figure 11.7 Apolar and slightly monopolar organic compound sorption coefficients, K,min (L nr2), observed for exchange between aluminum oxides and aqueous solutions plotted as a function of sor-bate hydrophobicity (as measured by yw) apolar series of chlorobenzenes (squares, Schwarzenbach and Westall, 1981) and aromatic and chloroaromatic compounds (diamonds, Maderet al., 1997).

Kaschabek, S. R. Reineke, W. (1992). Maleylacetate reductase of Pseudomonas sp. strain B13 dechlorination of chloromaleylacetates, metabolites in the degradation of chloroaromatic compounds. Archives of Microbiology, 158, 412-17. 

Genthner, B. R. S., Price, W. A. Pritchard, P. H. (1989)- Anaerobic degradation of chloroaromatic compounds in aquatic sediments under a variety of enrichment conditions. Applied and Environmental Microbiology, 55, 1466-71. 

Reactions on or close to solid surfaces maybe inhibited by deposition ofinsoluble or poorly soluble products on the reactant surface, a phenomenon referred to as overgrowth. Examples include the reaction of amines with chloranil [7], the diazotisation of poorly soluble aromatic amines in which the product diazonium salt is also insoluble and halogen exchange reactions of chloroaromatic compounds using potassium fluoride in dipolar aprotic solvents where the potassium chloride product may coat the potassium fluoride [8]. 

Fig. 5.60. Transformation of a phenol into a chloroaromatic compound by Ar-SN reaction via a Meisenheimer complex.

Mercury. - Cadmium. - Polycyclic Aromatic and Heteroaromatic Hydrocarbons. - Fluorocarbons. -Chlorinated Paraffins. - Chloroaromatic Compounds Containing Oxygen. - Organic Dyes and Pigments. - Inorganic Pigments. - Radioactive Substances. - Subject Index. 

This model has been applied to a wide variety of pollutants including carboxylic acids, phenolic, aminoaromatic, and chloroaromatic compounds. In every case it was able to reproduce the time course of the different species with a great accuracy. This, together with the small number of parameters and with their physical meaning made the model as an important tool to analyze electrochemical oxidation processes. 

Anaerobic Metabolism, To examine the extent of anaerobic chloroaromatic metabolism, we undertook a study in which sediments from the upper Hudson River, the lower Hudson River, and the East River were used as inoculum (33, 34). Each monochlorophenol isomer (2-, 3-, and 4-chloro-phenol, CP) and each monochlorobenzoate isomer (2-, 3-, and 4-chloroben-zoate, CB) was used as substrate. Duplicate or triplicate cultures were established under three anaerobic conditions denitrifying, sulfidogenic, and methanogenic. The initial concentration of each of the chloroaromatic compounds was 0.1 mM incubation was at 30 °C in the dark. Substrates were quantified by high-pressure liquid chromatography N2 and CH4 were analyzed by gas chromatography nitrate and sulfate were determined by colorimetric methods or by ion chromatography (33, 34). 

During the past decade, considerable progress has been made in the area of transition metal-catalyzed cleavage and functionalization of the inert C-Cl bond in nonactivated chloroaromatic compounds. This new and important field of chemistry is reviewed in the present chapter, which describes both mechanistic and synthetic aspects of C-Cl activation. Oxidative addition reactions of chloroarenes to complexes of catalytic metals are discussed, along with their applications in a wide variety of reductive dechlorination, nucleophilic displacement, olefin arylation, coupling, and carbonylation reactions. 

The significance of toxic metabolites is important in a number of diverse metabolic situations (1) when a pathway results in the synthesis of a toxic or inhibitory metabolite and (2) when pathways for the metabolism of two (or more) analogous substrates supplied simultaneously are incompatible due to the production of a toxic metabolite by one of the substrates. A number of examples are provided to illustrate these possibilities that have achieved considerable attention in the context of the biodegradation of chloroaromatic compounds, and further discussion is provided in Chapter 6, Section 6.5.1.2. The issue of toxic or inhibitory metabolites also merits attention in a wider context (Chapter 7, Section 7.5). 

The degree and position of chlorination affects the bioavailabilities of chloroaromatic compounds. For example, the higher chlorinated PCBs, PCDDs and PCDFs tend to exhibit lower bioaccumulation rates than their lower chlorinated counterparts in the presence of sediment and soil, apparently reflecting variations in adsorption characteristics of the chloroaromatics (Tarsen et al. 1992 Toonen et al. 1994). 

On the contrary, chloroaromatic compounds, such as decachlorodiphenyl, are too stable thermally to be widely used as flame retardants. 

Sutton, M. M., and E. N. Hunter. 1988. Pho-tolytic/thermal destruction of dioxins and other toxic chloroaromatic compounds. Chemosphere 79(1-6) 685-90. 

As indicated in a previous paper near quantitative yields of biphenyl derivatives can be obtained from select chloroaromatic compounds using zero valent nickel-triphenylphosphine complex in the presence of zinc metal. The conditions employ a catalytic amount of nickel-triphenylphosphine complex in the presence of zinc metal in dry, dipolar aprotic solvents at 60 to 80°C. The reaction is complete in a few minutes. 

Several bacteria able to grow on 3-nitrobenzoate as the sole source of carbon and nitrogen have recently been isolated (29). One strain was a spontaneous mutant derived from Pseudomonas sp. strain JS150 which was previously isolated for its ability to grow on a variety of chloroaromatic compounds. In addition, a Comamonas strain able to grown on... 

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