Chlorinated aromatic compounds phenols

As recently as 1970, only about 30 naturally occurring organohalogen compounds were known. It was simply assumed that chloroform, halogenated phenols, chlorinated aromatic compounds called PCBs, and other such substances found in the environment were industrial pollutants. Now, only a third of a century later, the situation js quite different. More than 5000 organohalogen compounds have been found to occur naturally, and tens of thousands more surely exist. From a simple compound like chloromethane to an extremely complex one like vancomycin, a remarkably diverse range of organohalogen compounds exists in plants, bacteria, and animals. Many even have valuable physiological activity. Vancomycin, for instance, is a powerful antibiotic produced by the bacterium Amycolatopsis orientalis and used clinically to treat methicillin-resistant Staphylococcus aureus (MRSA). 

The photocatalytic degradation of chlorophenols on ZnO has also been demonstrated [127]. The photocatalytic degradation of other chlorinated aromatic compounds [127], phenol [128-134], fluorinated aromatic compounds [135], and other substituted phenols and aromatic compounds [Izumi 1981, 738 Matthews 1984, 2386 Abdullah 1990, 2099 [136-141] have been demonstrated. The degradation of halogenated aromatic pollutants such as polychlorinated biphenyls (PCBs) [142] and polybrominated dibenzofiirans [143] has also been attempted. 

Polycyclic aromatic hydrocarbons Alkylated aromatic hydrocarbons Chlorinated aromatic compounds Chlorobenzenes Polychlorinated biphenyls Polychlorinated dibenzo[l,4]dioxins Chlorinated guaiacols and catechols Nitrogen-containing aromatic compounds Azaarenes and aromatic nitriles Oxygenated aromatic compounds 2,4-Dipentyl phenol Polycyclic quinones and ketones Aliphatic carboxylic acids Cs and C, dicarboxylic acids... 

There has been substantial interest in the fate of chlorinated aromatic compounds under anaerobic conditions since some of these, such as PCBs, polychlorinated phenols, polychlorinated catechols, and polychlorinated anilines, have been recovered from anaerobic sediment samples. The persistence of these compounds is therefore determined by the activity of anaerobic dehalogenating bacteria and extensive effort has therefore been devoted to isolating the relevant organisms. An increasing number of strains have been obtained in pure culture. They display different specificities, some use the aromatic substrate as an electron acceptor, and the role of reductive dechlo-ination in energy metabolism has been reviewed (Holliger et al. 1999). 

Py-MS (Py at 930 °C) shows that the major decomposition products of BPA and Chakon Il-polyacrylates are a series of phenols and some other flammable aromatic compounds (Figure 2.4). However, BPC Il-polyacrylate gives out less flammable compounds (such as phenols), but more CO2, CO and HCl and some chlorinated aromatic compounds which have relatively low fuel values and may also confer flame-retardant effects in the gas phase. Therefore, the reduced flammability of Chakon... 

Koini et al. [125] reported an efficient and mild method for the chlorination and bromination of oxygenated aromatic compounds (phenols, substituted phenols, methoxyarenes, and 1,4-benzoxazines) (178/180) with good regioselectivity and yields (47-68%), using a combination of HCl or HBr/(30%)H2O2/AcOH in petroleum ether as solvent (Scheme 47). The use of ultrasound irradiation did not confer any additional advantage when compared with conventional heating. 

The next section reviews, the neurobehavioral affects of solvents found in the environment in the order of importance. " We begin with trichloroethylene (TCE) and related short chain chlorinated agents. Next are aromatic compoxmds such as toluene including related xylene and styrene with comments on creosols or phenols. The chlorinated aromatic compounds follow dichlorophenol and polychlorinated biphenyls and their highly... 

Oxidation of phenols with chlorine dioxide or chlorine produces chlorinated aromatic intermediates before ring rupture. Oxidation of phenols with either chlorine dioxide or ozone produces oxidized aromatic compounds as intermediates which undergo ring rupture upon treatment with more oxidant and/or longer reaction times. In many cases, the same nonchlorinated, ringruptured aliphatic products are produced using ozone or chlorine dioxide. 

Schnaak et al. [4] Polychlorinated terphenyls, naphthalenes, chloropesticides, halogenated hydrocarbon solvents, aromatic hydrocarbon solvents (BTEX), chlorobenzenes, poly aromatic hydrocarbons (EPA 610), phenols, chlorophenols, phthalates, petroleum hydrocarbons, LAS and nonylphenol (NP), organotin compounds and 2,4-dichloroaniline 1 pg/kg to 10 mg/kg for chlorine-contained compounds 10 pg/kg to 1 g/kg for solvent and phenols 1 mg/kg to 10 g/kg for EPA610, DEHP, LAS, and mineral oils Sewage sludge... 

Such xenobiotics as aliphatic hydrocarbons and derivatives, chlorinated ahphatic compounds (methyl, ethyl, methylene, and ethylene chlorides), aromatic hydrocarbons and derivatives (benzene, toluene, phthalate, ethylbenzene, xylenes, and phenol), polycyclic aromatic hydrocarbons, halogenated aromatic compounds (chlorophenols, polychlorinated biphenyls, dioxins and relatives, DDT and relatives), AZO dyes, compounds with nitrogroups (explosive-contaminated waste and herbicides), and organophosphate wastes can be treated effectively by aerobic microorganisms. 

Elforts have been made to characterize the nature and content of individual components that are present in the low-molecular-mass fraction of the total mill effluents, which include the spent chlorination and alkali extraction stage liquors [2,4]. Approximately 456 types of compounds have been detected in the conventional bleach effluents, of which 330 are chlorinated organic compounds [22]. The compounds may be lumped into three main groups, namely, acidic, phenolic, and neutral (Table 2). Acidic compounds are further divided into the five categories of acids fatty, resin, hydroxy, dibasic, and aromatic acids. The most important fatty acids are formic and acetic acids. The dominant resin acids are abietic and dehydroabietic acids. Among the hydroxy acids identified, glyceric acid predominates. Dibasic acids such as oxalic, malonic, succinic, and mafic acids are derived from the lignin and carbohydrate fraction... 

The technology is best suited for the removal of water-soluble metals and organics. Organics that would most likely be mobilized by this process include aromatic compounds such as benzene, toluene, xylene, and phenolic compounds, as well as chlorinated solvents. Electroki-netic remediation is not a practical method of remediation for insoluble organics such as heavy hydrocarbons. 

Organic compounds, aromatic solvents (benzene, toluene, nitrobenzenes, and xylene), chlorinated aromatics (PCBs, chlorobenzenes, chloronaphthalene, endrin, and toxaphene), phenols and chlorophenols (cresol, resorcinol, and nitrophe-nols), polynuclear aromatics (acenaphthene, benzopyrenes, naphthalene, and biphenyl), pesticides and herbicides (DDT, aldrin, chlordane, BHCs, heptachlor, carbofuran, atrazine, simazine, alachlor, and aldicarb), chlorinated... 

Ozone reacts slowly with many types of water contaminants such as alicyclic taste or odor compounds, e. g. geosmin or THMs and unactivated aromatics such as chlorinated benzenes. Ozone will react faster with certain types of aromatic compounds, e. g. those carrying electron supplying substituents such as the hydroxyl group in phenol. If there is no... 

Reductive dehalogenation of chlorinated phenols to phenol, cyclohexanol and other chlorine-free compounds takes place rapidly with hydrogen gas and Pd/C in an aqueous system or under solvent-free conditions. Thus, pentachloro phenol was able to be completely dechlorinated within 20 min (Scheme 4.45). This methodology enables a facile route for rapid and complete detoxification of highly toxic polychlorinated aromatic hydrocarbons and environmental remediation71,72. 

Many toxic substances, environmental pollutants, and hazardous waste compounds, such as benzene, toluene, naphthalene, and chlorinated phenols, are aromatic compounds (see Figure 1.14). 

On the other hand Price and Sears [107] studied the reactions of nitryl chloride with various aromatic compounds in the presence of aluminium chloride, and found that phenol, anisole and naphthalene tended to undergo oxidative degradation. In the case of naphthalene they obtained a 31% yield of a- nitronaphthalene, whereas with anisole and phenol they were able to isolate only traces of nitro compounds without any evidence of chlorination. 

While the process at the cathode always ends finally in withdrawal of oxygen or in taking up of hydrogen, the number of possible reactions at the anode—aside from solution-phenomena, which are without interest here—is a much greater one. For, each ion which is capable of substituting can pass into the reactive state at the anode and produce reactions which cannot be numbered with the real oxidations. In the first place numerous substitutions can occur in difficultly oxidizable bodies, especially aromatic compounds, for instance the chlorination of phenols and phthale ins, nitration of acids, diazotizing of amines, etc. Substitution and oxidation processes often occur simultaneously, as in the electrolytic formation of iodoform from alcohol. 

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