Polychlorinated products

Use of mercuric catalysts has created a serious pollution problem thereby limiting the manufacture of such acids. Other catalysts such as palladium or mthenium have been proposed (17). Nitration of anthraquinone has been studied intensively in an effort to obtain 1-nitroanthraquinone [82-34-8] suitable for the manufacture of 1-aminoanthraquinone [82-45-1]. However, the nitration proceeds so rapidly that a mixture of mono- and dinitroanthraquinone is produced. It has not been possible, economically, to separate from this mixture 1-nitroanthraquinone in a yield and purity suitable for the manufacture of 1-aminoanthraquinone. Chlorination of anthraquinone cannot be used to manufacture 1-chloroanthraquinone [82-44-0] since polychlorinated products are formed readily. Consequentiy, 1-chloroanthraquinone is manufactured by reaction of anthraquinone-l-sulfonic acid [82-49-5] with sodium chlorate and hydrochloric acid (18). 

Efficient synthesis of 2-chlorofuran is best achieved by decarboxylation of 2-chlorofuran-5-carboxylic acid (63JGU1397) or via the lithium derivative of furan. When furan or 3-bromofuran were treated in turn with ethyl-lithium and hexachloroethane, 2-chlorofuran (48%) or 3-chlorofuran (54%) was formed, uncontaminated by any polychlorinated products (73SC213). Chlorodesilylation of ethyl 5-trimethylsilyl-2-furoate with sul-furyl chloride in acetonitrile gave the 5-chloro ester in —85% yield (91MI4). 

Chlorination of Alkanes. Free-radical chlorination is the most commonly used method for the chlorination of a saturated hydrocarbon.31 106-108 111 112 Both thermal and photochemical processes may be carried out in the liquid or vapor phase. The liquid-phase photochemical procedure is preferred for polychlorination gas-phase photochemical reactions can yield either mono- or polychlorinated product. 

Fig. 4.1 Separation of technical pentachlorophenol using cyclohexane-acetic acid (98 2) as the eluting solvent. Peaks 1, mixture of dioxins and other polychlorinated products 2, mixture of chlorinated phenols including trichlorophenol 3, tetrachlorophenol 4, pentachlorophenol...

Of particular interest is that chlorination of Ni-mesotetraphenylporphyrin 177 was also conducted with this selenurane [82]. Thus, the reaction of 177 with 172a used in a 1 3 molar ratio gave a mixture of di-178 (30%), tri-179 (50-55%), and polychlorinated products. When a 15-fold molar excess of PhSeClg was used, compounds 180 and 181 containing six and seven chlorine atoms were obtained (Scheme 23). 

Although yields of imidazoles are not always good, and the 5-chloro products may be contaminated with polychlorinated products, the method can be useful. If symmetrical oxamides are heated at 60-95°C with 2.1 mol eq. of phosphorus pentachloride in phosphoryl chloride (with cooling to moderate the exothermic reaction), followed by further heating at around 100°C for 30 min, high yields of (1) are achievable [5]. Some unsymmetrical oxamides have also been shown to give good yields on occasion [8] (Table 2.1.1). 

Polychlorinated products may be obtained by further chlorination of chlorine-containing compounds 29, 62, McBee and Hass (55, 55, 56, 59 devised a process for chlorinating an organic compound in such a way that rupture of the carbon-to-carbon bond takes place, and polychloro compounds with fewer carbon atoms than the starting material are obtained. They used the term chlorinolysis to define this process. Further chlorinations of polychloro compounds may lead to the formation of unsaturated compounds. For example, high-temperature chlorination of polychloropentanes and polychlorobutanes, led to production of hexachlorocyclopentadiene 52 and hexachlorobutadiene 60, respectively. 

In conventional solvents, the ratio of mono- to polychlorinated products (M/P) has been shown to depend on solvent viscosity [65]. 

This behaviour is generally characteristic of a bifunctional mechanism beyond a turning point value of the platinum concentration, the activity of the support becomes the limiting step. Therefore, chlorobenzene initially undergoes a partial transformation on the acid sites of the zeolite, and the reaction is then completed on the metal particles. On the platinum loaded catalysts, polychlorinated products (PhClx) were... 

Also obtained when 4-hydroxycoumarin in aceticacid was treated with an excess of gaseous chlorine at 10-15° and the polychlorinated product so formed hydrolyzed [4668,4669]. 

Attempts to prepare carbazolesulfonyl chlorides by reacting carbazole 15 with chlorosulfonic acid (one or two equivalents) in thionyl chloride were unsuccessful and appear to yield polychlorinated products. On the other hand, treatment of carbazole with boiling excess chlorosulfonic acid in the presence of varying proportions of phosphorus pentachloride was claimed to yield carbazolesulfonyl chlorides. Carbazole 15 reacted with excess chlorosulfonic acid (seven equivalents) in chloroform solution at room temperature (1 hour) to give the 1,3,6-trisulfonyl chloride 19, 72% (Scheme 2). ... 

TaF has been characterized by ir, Raman, x-ray diffraction, and mass spectrometry (3,11,12). TaF has been used as a superacid catalyst for the conversion of CH to gasoline-range hydrocarbons (qv) (12) in the manufacture of fluoride glass and fluoride glass optical fiber preforms (13), and incorporated in semiconductor devices (14). TaF is also a catalyst for the Hquid-phase addition of HF to polychlorinated ethenes (15). The chemistry of TaF has been reviewed (1,16—19). Total commercial production for TaF is thought to be no more than a few hundred kilograms aimuaHy. 

Historically, polychloriaated biphenyls (PCBs) and to a lesser extent polychlorinated terphenyls (PCTs) were the most important derivatives of the respective polyphenyls. When they came to be recognized as serious environmental contaminants, production ceased in the early 1970s. These products are now of significance primarily because of thek environmental aftereffects (62). Much environmental research and governmental regulations stem therefrom... 

Polychlorinated Pesticides. A once substantial but now diminished use for DCPD is in the preparation of chlorinated derivatives for further use or synthesis into pesticide compounds (see Insectcontrol technology). Soil permanence and solubiUty of the products in human fatty tissues have considerably restricted the use of these compounds. The more prominent chlorinated pesticides were aldrin, dieldrin, chlordane, and heptachlor, all of which use hexachorocyclopentadiene as a starting material. Aldrin and dieldrin are no longer used in the U.S. Chlordane and heptachlor are stiU produced, but only for export use. 

TCDD is the most potent inducer of chloracne. This has been well known since the accident in Seveso, Italy, in 1976 in which large amounts of TCDD were distributed in the environment subsequent to an explosion in a factory that produced a chlorophenoxy herbicide, 2,4,5-T. TCDD is an impurity produced during the production of 2,4,5-T. The most common long-term effect of TCDD exposure was chloracne. Exposed individuals also suffered increased excretion of porphyrins, hyper-pigmentation, central nervous system effects, and liver damage and increased risk of cancer was a long-term consequence of the exposure. In addition to TCDD, polychlorinated biphenyls (PCBs), polychlorinated dibenzofurans, and polychloronaphthalens cause chloracne as well as other effects typical of TCDD. 7i... 

Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in marine products and estimation of exposure through fishes and shellfishes 97YZ850. 

Polychlorination, on the other hand, can he carried out on the whole range of n-paraffins from C10-C30 at a temperature range of 80-120°C (using a high Cl2/paraffm ratio). The product has a chlorine content of approximately 70%. Polychloroparaffins are used as cutting oil additives, plasticizers, and retardant chemicals. 

PCDFs are similar in many respects to PCDDs but have been less well studied, and will be mentioned only briefly here. Their chemical structure is shown in Figure 7.1. Like PCDDs, they can be formed by the interaction of chlorophenols, and are found in commercial preparations of chlorinated phenols and in products derived from phenols (e.g., 2,4,5-T and related phenoxyalkanoic herbicides). They are also present in commercial polychlorinated biphenyl (PCB) mixtures, and can be formed... 

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