Synthesis of chlorinated dibenzofurans and chlorinated amino-dibenzofurans from the corresponding diphenyl ethers and nitro-diphenylethers

The synthesis of five chlorinated dibenzofurans and three chlorinated animodibenzofurans from easily available diphenyl ethers is described. Also reported is the preparation of the diphenyl ethers. The ¹H-NMR and mass spectra data for the compounds are also reported.     

Photo-electrochemical degradation of some chlorinated organic compounds on n-TiO2 electrode

The electrolysis of some chlorinated organic compounds such as chloroacetic acids, chloromethanes and chloroethenes were carried out on a photo-irradiated n-TiO(2) electrode applied a constant potential, 1.0 V vs. Ag/AgCl, and the alternated pulse potentials of +1.0 V and various negative potentials, -1.0, -1.2 and -1.4V vs. Ag/AgCl in 0.1 mol dm(-3) Na(2)SO(4) solutions saturated with oxygen or with nitrogen. These compounds were degraded on the n-TiO(2) electrode by the photo-electrolysis and mineralized to carbon dioxide, carbon monoxide and chloride ion. When the alternated pulse potentials were applied, the mineralization yields were increased for these compounds, especially for trichloroacetic acid and carbon tetrachloride, both of which were comparatively stable to the degradation in the constant potential electrolysis. The presence of oxygen in the solution was effective for the mineralization of these compounds, while little effective for that of trichloroacetic acid and of carbon tetrachloride.     

Incidence of chlorinated benzenes and chlorinated ethylenes in Lake Ontario Herring Gulls

Great Lakes Herring Gulls (Larus argentatus) and their eggs have proven to be useful integrators on a lakewide basis of high molecular weight, relatively involatile organochlorine pollutants such as PCRs. A search for relatively volatile organochlorine compounds by GC/MS also revealed the presence of tri- and tetrachloroethylene, and isomers of di-, tri-, tetra-, penta- and hexachlorobenzene in the body lipid of adult Herring Gulls from Lake Ontario. Analysis of pooled eggs from colonies throughout the Great Lakes in 1978 showed that pentachlorobenzene and hexachlorobenzene were ubiquitous contaminants at levels from 14–50 ng/kg and 90–350 ng/kg, respectively. Hexachlorobenzene levels were 2–3 times higher in Lake Ontario than the other lakes, whereas pentachlorobenzene was more evenly distributed geographically. Levels of 1,2,3,4-tetra-, 1,2,4,5-tetra- and 1,2,4-trichlorobenzene near the detection limit of 10–20 ng/kg were found in a few samples.     

Microbial degradation of chlorinated dioxins

Polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) were introduced into the biosphere on a large scale as by-products from the manufacture of chlorinated phenols and the incineration of wastes. Due to their high toxicity they have been the subject of great public and scientific scrutiny. The evidence in the literature suggests that PCDD/F compounds are subject to biodegradation in the environment as part of the natural chlorine cycle. Lower chlorinated dioxins can be degraded by aerobic bacteria from the genera of Sphingomonas, Pseudomonas and Burkholderia. Most studies have evaluated the cometabolism of monochlorinated dioxins with unsubstituted dioxin as the primary substrate. The degradation is usually initiated by unique angular dioxygenases that attack the ring adjacent to the ether oxygen. Chlorinated dioxins can also be attacked cometabolically under aerobic conditions by white-rot fungi that utilize extracellular lignin degrading peroxidases. Recently, bacteria that can grow on monochlorinated dibenzo-p-dioxins as a sole source of carbon and energy have also been characterized (Pseudomonas veronii). Higher chlorinated dioxins are known to be reductively dechlorinated in anaerobic sediments. Similar to PCB and chlorinated benzenes, halorespiring bacteria from the genus Dehalococcoides are implicated in the dechlorination reactions. Anaerobic sediments have been shown to convert tetrachloro- to octachlorodibenzo-p-dioxins to lower chlorinated dioxins including monochlorinated congeners. Taken as a whole, these findings indicate that biodegradation is likely to contribute to the natural attenuation processes affecting PCDD/F compounds.     

Relative retention times of chlorinated monoterpenes

GC retention times for 67 chlorinated monoterpenes, belonging to the technical pesticide Toxaphene have been measured under the same conditions and relative retention times have been determined. They consisted of 45 chlorinated bornanes, 13 chlorinated bornenes, 8 chlorinated dihydrocamphenes and 1 chlorinated camphene. Useful correlations between structure and retention time were found. Similar changes in structure for different compounds lead to similar changes in retention times. These correlations allow to predict retention times for yet unknown Toxaphene congeners.     

Numerical simulation of the thermal destruction of some chlorinated C1 and C2 hydrocarbons

We have numerically modeled the breakdown of small quantities of several chlorinated hydrocarbons (CH3Cl, CH2Cl2, CHCl3, CCl4, C2H3Cl, and C2H5Cl) in a lean mixture of combustion products between 800 and 1480 K. This simulates the fate of poorly atomized waste in a liquid-injection incinerator. Kinetics calculations were performed using the CHEMKIN and SENKIN programs, with a reaction mechanism that was developed at Louisiana State University to model flat-flame burner experiments. A 99.99-percent destruction efficiency was attained in one second at temperatures ranging from 1280 to 960 K, with CCl4 requiring the highest temperature for destruction and C2H5Cl the lowest. For all compounds except C2H5Cl, there was a range of temperatures at which byproducts accounted for several percent of the elemental chlorine at the outlet. The more heavily chlorinated compounds formed more byproducts even though the amount of elemental chlorine was the same in all cases. The sensitivity of results to residence time, equivalence ratio, temperature profile, and the presence of additional chlorine, was examined for the case of CHCl3.     

Photodegradation of chlorinated pesticides dispersed on sand

The photochemical behaviour of several chlorinated pesticides, namely 4-chloro-2-methylphenoxyacetic acid (MCPA), dichlorophen (DCPH), flamprop-methyl (FPM) and vinclozolin (VCZ) is studied on various kinds of sand: Fontainebleau sand (almost pure silica), Touggourt sand (coloured sand from Sahara) and Jijel sand (dark marine sand). The photodegradation of MCPA is more rapid on Fontainebleau sand than on the two others, because the former is almost colourless pure silica and the others adsorb on the internal surface of the reactor. The degradation rate decreases in the order MCPA, DCPH, FPM, VCZ. The main products identified are 4-chloro-2-methylphenol with MCPA and reduction product with DCPH.     

Formation of chlorinated disinfection by-products in viticulture

Background, aim and scope  The use of sodium hypochlorite (HYP) in viticulture results in effluents which are contaminated with halogenated substances. These disinfection by-products (DBPs) can be quantified as group parameter ‘adsorbable organic halogens’ (AOX) and have not been determined in effluents of viticulture yet. The substances that are detected as AOX are unknown. The AOX can be composed of harmless substances, but even toxic contaminants. Thus, it is impossible to assess ecological impacts. The aim of this study is to determine the quantification of AOX and DBPs after the use of HYP. This will be helpful to reduce environmental pollution by AOX. Materials and methods  The potential of HYP to generate AOX was determined in laboratory-scale experiments. Different model solutions were treated with HYP according to disinfection processes in viticulture and conditions of AOX formation in effluents were simulated. AOX were quantified using the flask-shaking method and identified DBPs were investigated by gas chromatography–mass spectrometry. Results  Treatment with HYP resulted in the formation of AOX. The percentage conversion of HYP to AOX was up to 11%. Most important identified DBPs in viticulture are chloroform, dichloroacetic acid and trichloroacetaldehyde. In addition, the formation of carbon tetrachloride (CT), 1,1,1-trichloropropanone, 2,4-dichlorobenzoic acid and 2-chloro-/2,4-dichlorophenylacetic acid was investigated. It was demonstrated that reaction temperature, concentration of HYP and type of organic matter have important influence on the formation of chlorinated DBPs. Discussion  The percentage conversion of HYP to AOX was similar to other published studies. Although a correlation of single compounds and AOX is difficult, chloroform was the predominant AOX. Generation of the volatile chloroform should be avoided due to possible adverse effects. The generation of dichloroacetic acid is of minor importance on account of biodegradation. Trichloroacetaldehyde and 1,1,1-trichloropropanone are weak mutagens and their formation should be avoided. Conclusions  The generation of AOX and chlorinated DBPs can be minimised by reducing the concentrations of the organic materials in the effluents. The removal of organic matter before disinfection results in a decreased formation of AOX. HYP is an effective disinfectant; therefore, it should be used at low temperatures and concentrations to reduce the amount of AOX. If possible, disinfection should be accomplished by the use of no chlorine-containing agents. By this means, negative influences of HYP on the quality of wine can also be avoided. Recommendations and perspectives  Our results indicate that HYP has a high potential to form AOX in effluents of viticulture. The predominant by-products are chloroform, dichloroacetic acid and trichloroacetaldehyde. In further research, wastewaters from a winery and the in- and outflows of two sewage treatment plants were sampled during vintage and analysed. These results will be discussed in a following paper.     

Anaerobic transformations and bioremediation of chlorinated solvents

Chlorinated aliphatic compounds, notably the chlorinated solvents, are common contaminants in soil and groundwater at hazardous waste sites. While these compounds are often recalcitrant, under favorable conditions they can be transformed and degraded through microbially mediated processes. There is great interest in understanding the transformations that are observed at contaminated sites and in manipulating these systems to achieve remediation. An important class of transformations occurs in anaerobic environments. Many of the transformations are reductive, and many yield useful energy to specific anaerobic bacteria. They include reductive dechlorination, dehydrochlorination and dichloroelemination. Of these, reductive dechlorination is often a growth-supporting reaction, while the others may be abiological or catalyzed by biological molecules. The reactions may result in chlorinated products, but there are often reaction sequences leading to completely dechlorinated products. The behavior of carbon tetrachloride (CT), 1,1,2,2-tetrachloroethane (TeCA) and the chloroethenes, perchloroethylene (PCE) and trichloroethylene (TCE), illustrate the range of anaerobic transformations that are possible, as well as the limited transformation that often is seen in the environment. CT undergoes reductive and substitutive reactions that are catalyzed by biological molecules but do not support bacterial growth. The anaerobic degradation of TeCA, which is a major contaminant at a site near Tacoma, WA, USA, provides examples of each type of transformation, and the products formed are consistent with the chlorinated compounds that are found in groundwater extraction wells. A laboratory study, using anaerobic sludge that had been fed chlorinated compounds, a cell-free extract from the sludge, and killed controls, showed that TeCA was transformed to four products and that these were further transformed, suggesting that it might be possible to degrade TeCA to innocuous products. Reductive dechlorination of PCE and TCE has been studied in many laboratories. Studies with mixed anaerobic consortia and with several dehalogenating bacteria, including strain 195 (. Isolation of a bacterium that reductively dechlorinates tetrachloroethane to ethane. Science 276, 1568-1571) that transforms PCE to ethene, have demonstrated that reductive dechlorination supports growth of the novel bacteria that carry out the reactions. Hydrogen has been shown to be an electron donor for the bacterial dehalogenation reactions, and kinetic and thermodynamic considerations indicate that dehalogenators can compete in some, but not all, anaerobic environments, pointing to applications of in situ bioremediation and to its limitations. Selected field studies of anaerobic transformations help delineate the applications of this type of bioremediation.     

Sorption kinetics of chlorinated hydrophobic organic chemicals

This is the second of a two-part series describing the sorption kinetics of hydrophobic organic chemicals. Part I “The Use of First-Order Kinetic Multi-Compartment Models” is published in issue 1 of this journal, pp. 21–28. Sorption kinetics of chlorinated benzenes from a natural lake sediment have been investigated in gas-purge desorption experiments. Biphasic desorption curves, with an initial “fast” part and a subsequent “slow” part, were found for all tested chlorobenzenes. From these results first-order sorption uptake and desorption rate constants were calculated with a two-sediment compartment model, which is presented in the first paper. In three sets of experiments the sorption uptake period and sediment/water ratio were varied. Rate constants are not influenced by these experimental conditions, which supports the partitioning concept for the sorption of hydrophobic organic chemicals in sediments.     

Oxidative ring cleavage of low chlorinated biphenyl derivatives by fungi leads to the formation of chlorinated lactone derivatives

The yeast Trichosporon mucoides and the filamentous fungus Paecilomyces lilacinus as biphenyl oxidizing organisms are able to oxidize chlorinated biphenyl derivatives. Initial oxidation of derivatives chlorinated at C4 position started at the non-halogenated ring and went on up to ring cleavage. The products formed were mono- and dihydroxylated 4-chlorobiphenyls, muconic acid derivatives 2-hydroxy-4-(4-chlorophenyl)-muconic acid and 2-hydroxy-5-(4-chlorophenyl)-muconic acid as well as the corresponding lactones 4-(4-chlorophenyl)-2-pyrone-6-carboxylic acid and 3-(4-chlorophenyl)-2-pyrone-6-carboxylic acid. Altogether T. mucoides formed 12 products and P. lilacinus accumulated five products. Whereas the rate of the first oxidation step at 4-chlorobiphenyl seems to be diminished by the decreased bioavailability of the compound, no considerable differences were observed between the degradation of 4-chloro-4'-hydroxybiphenyl and 4-hydroxybiphenyl. Twofold chlorinated biphenyl derivatives did not serve as substrates for oxidation by either organism with the exception of 2,2'-dichlorobiphenyl, transformed by the yeast Trichosporon mucoides to two monohydroxylated derivatives. The results show, that soil fungi may contribute to the aerobic degradation of low chlorinated biphenyls accumulating from anaerobic dehalogenation of PCB by bacteria.     

Effective synthesis of sulfate metabolites of chlorinated phenols

Chlorophenols are an important class of persistent environmental contaminants and have been implicated in a range of adverse health effects, including cancer. They are readily conjugated and excreted as the corresponding glucuronides and sulfates in the urine of humans and other species. Here we report the synthesis and characterization of a series of ten chlorophenol sulfates by sulfation of the corresponding chlorophenols with 2,2,2-trichloroethyl (TCE) chlorosulfate using N,N-dimethylaminopyridine (DMAP) as base. Deprotection of the chlorophenol diesters with zinc powder/ammonium formate yielded the respective chlorophenol sulfate ammonium salts in good yield. The molecular structure of three TCE-protected chlorophenol sulfate diesters and one chlorophenol sulfate monoester were confirmed by X-ray crystal structure analysis. The chlorophenol sulfates were stable for several months if stored at −20 °C and, thus, are useful for future toxicological, environmental and human biomonitoring studies.