Chlorinated phenoxy-2-phenols

Dioxins and furans are not produced deliberately, but are produced unintentionally as byproducts of combustions of organic matter in the presence of chlorine. Dioxins and fiirans consists of 135 possible chlorinated dibenzoftnan and 75 chlorinated dibenzo-p-dioxins with Irom 1 to 8 chlorine substituents (Figure 18.2). PCDDs/DFs are found as byproducts during the manufacture of some industrial chemicals such as PCBs, polychlorinated naphthalenes, chlorinated phenols, chlorinated phenoxyacids, polychlorinated diphenyl ethers, polyvinyl chlorides, and chlorinated phenoxy-2-phenols (Hutzinger et al, 1985 Hryhorczuk et al, 1986 ATSDR, 2001 Masunaga et al. 

The reaction products from 2,4-dichlorophenol were tetrachloro-phenoxyphenols and tetrachlorodihydroxybiphenyls (Figure 5), as determined from their mass spectra and those of their methyl ethers. 4,6-Dichloro-2-(2, 4 -dichlorophenoxy)phenol (V) was the major phenoxy-phenol the mass spectral fragmentation pattern of o-hydroxyphenol ethers is quite characteristic since a hydrogen transfer occurs during the fragmentation (Figure 6). A trace of a trichlorophenoxyphenol also was detected and was formed presumably by the unsensitized reductive loss of chlorine, discussed previously. 

Renberg [35] used an ion-exchange technique for the determination of chlorophenols and phenoxy acetic acid herbicides in soil. In this method the soil extracts are mixed with Sephadex QAE A-25 anion exchanger and the adsorbed materials are then eluted with a suitable solvent. The chlorinated phenols are converted into their methyl ethers and the chlorinated phenoxy acids into their methyl or 2-chloroethyl esters for gas chromatography. 

Polychlorinated Dibenzo-(p)-Dioxins and Dibenzo-Furans. Another group of compounds that we need to specifically address are the polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzo-furans (PCDFs) (Fig. 2.15). The PCDDs and PCDFs are not intentionally produced but are released into the environment from various combustion processes and as a result of their occurrence as unwanted byproducts in various chlorinated chemical formulations (e.g., chlorinated phenols, chlorinated phenoxy herbicides see Alcock and Jones, 1996). Because some of the PCDD and PCDF congeners are very toxic (e.g., 2,3,7,8-tetrachloro dibenzo-p-dioxin, see margin), there have been and still are considerable efforts to assess their sources, distribution, and fate in the environment. Similarly to the PCBs or DDT (see above), the PCDDs and PCDFs are highly hydrophobic and very persistent in the environment. It is therefore not surprising that they have also been detected everywhere on earth (Brzuzy and Hites, 1996 Lohmann and Jones, 1998 Vallack et al., 1998). Finally, we should note that polybrominated diphenylethers (PBDEs, see margin) that, like the PBBs (see above), are used as flame retardants, are of increasing environmental concern (de Boer et al., 2000). 

Chlorinated hydrocarbons Chlorinated phenoxy acetic acids Oigano-phosphates Phenols and cresols Onset of symptoms... 

Chlorinated phenoxy acid (CPA) herbicides can analysed by GC-MS only after derivatization. For LC-MS, negative-ion ESI is the method of choice. Deprotonated molecules are detected as the most abundant ions under these conditions, often next to a phenolate fragment ion due to the loss of the acid side chain. Next to the deprotonated molecule, weak formic acid adducts [M+HCOO] were observed for MCPA, 2,4-D, MCPP, andMCPB [41]. 

These results confirm our hypothesis, and prove the essential role of polychlorinated gem-dichlorocyclohexadienones as reaction intermediates which can react to give either noble products (chlorinated phenols in meta), or unwanted condensation products (polychloro phenoxy phenols, polychloro dihydroxy biphenyls, etc.). 

Unfortunately, PCP often contains impurities that are toxic not only to fungi and bacteria but also to other living organisms. Its environmental impact includes effects on human health as well as on plants and other environmental organisms, such as aquatic species and wildlife. Its impurities include the less chlorinated phenols, polychlorinated phenoxy phenols, polychlorinated dibenzo-p-dioxins, and polychlorinated furans. By the late 1980s, pentachloro-phenol and its impurities had become so ubiquitous in the environment that its use has now been restricted. 

Phenolic compounds are ubiquitous in the environment coming from different sources such as manufacturing processes used in the plastic, dye, drug, antioxidant, and pesticide industries. Chloro- and nitrophenols are the main degradation products of many chlorinated phenoxy acid and organophosphorus pesticides, respectively [1,2]. These compounds are of particular interest and concern to the environment because they are toxic to most aquatic organisms [3,4]. Moreover, they affect the taste and odor of both water and fish even at very low concentrations of phenolic compoimds in water [5]. The US Environmental Protection Agency (EPA) has listed 11 phenols as priority pollutants [6]. 

Chlorinated phenols enter the aquatic environment as by-products of industrial processes, such as the production of antioxidants, dyes, and drugs. In drinking water they occur as a result of the chlorination of phenols, as by-products of reactions with phenolic acids, as biocides, or as degradation products of phenoxy herbicides and chlorinated bleaching of paper. CP concentration in drinking water usually does not exceed 1 pg L, which is the US EPA s maximum allowable contaminant level (MCL) for drinking water for pentachlorophenol, the only listed CP. ... 

This group of pesticides comprises different families of chemicals with her-bicidal action including substituted phenols, chlorinated aliphatic acids, chloro-phenoxy alkanoic acids, and substituted benzoic acids, which possess carboxyl or phenolic functional groups capable of ionization in aqueous media to yield anionic species [47,151,168-170]. 

Dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) dominated the herbicide market up to the late 1960s. These are sometimes called phenoxy herbicides. Phenol is the starting material for 2,4-D. Chlorination via electrophilic aromatic substitution (know the mechanism ) gives 2,4-dichlorophenol. The sodium salt of this compound can react with sodium chloroacetate (Sn2) and acidification gives 2,4-D. 

The reaction is generally carried out in the presence of a base such as sodium hydroxide. Bisphenol A is a phenol and, as such, a weak acid. The generated RO reacts with the electron-poor chlorine-containing carbon on epichlorohydrin, creating a cyclic ether end group. The phenoxy moiety can also react with the cyclic ether, eventually forming the polyether structure. This sequence is described in Figure 4.8. 

Numerous studies on the metabolism of 2,1t-dichlorophenoxy-acetic acid (2,1+-D) and related herbicides in animals have shown that these chemicals are absorbed and distributed rapidly in the body, and are excreted, undegraded, relatively quantitatively in the urine within a week after administration (M Pharmacokinetic studies with 2,1+,5-T in rats and dogs (5.) and in humans (6J supported these findings, and demonstrated that rates of clearance from plasma and elimination in urine depend on dosage level, animal species, and chemical structure of the phenoxy acid being studied ( + ). Corresponding chlorinated phenol metabolites were detected only in ruminants (M or in trace amounts in urine of rats fed very high doses of phenoxy herbicides (7.) ... 

The synthesis of the series of 2,4,5-amino-substituted derivatives of 1-phenoxy-anthraquinone (II) was accomplished by an exchange of chlorine or bromine atoms upon heating the corresponding 1-chloro- or 1-bromoanthraquinones in a phenol-phenoxide solution as well as by alkylation of 1-aminomethyl- or dimethylanthra-quinones using methyliodide.14... 

Phenoxy-5,13-pentacenequinone (IV) was obtained by the replacement of chlorine atoms with phenoxy groups in 5-chloro-6,13-pentacenequinone in a phenol-phenoxide melt (Scheme 7).57 5-Chloro-6,13-pentacenequinone was synthesized by cyclization of 2-(l-chloro-2-naphthoyl)-3 naphthoic acid, which was prepared by acylation of a-naphthol with anhydrous naphthalene-2,3-dicarboxylic acid and by the subsequent treatment of the resultant 2-(l-oxy-2-naphthoyl)-3 naphthoic acid with phosphorus pentachloride. 

When a side chain also contains a halogen atom, such as in l,l-dichloro-2-(chloromethyl)cy-clopropane (22) or 2-(bromomethyl)-l,l-dichlorocyclopropane, elimination can occur to give a methylenecyclopropane followed by two elimination-addition cycles. The elimination-addition products are accompanied by variable amounts of substitution products in which the two chlorine atoms on the ring remain intact. Thus, for example, reaction of 22 with phenolate under phase-transfer conditions gives 10% of the substitution product 24 along with 73.5% of the double-addition product, 2-methylene-l,l-bis(phenoxy)cyclopropane (23). Bulkier nucleophiles, such as those derived from 2-phenylpropanenitrile and diphenylacetonitrile, do not add twice to the same carbon atom and give 88 and 46% yield of the 2,3-bisadducts 25, respectively. 

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