Octachlorodibenzo dioxin

Table I. Octachlorodibenzo- >-dioxin Concentration before and after Burning Paper and Wood Treated with Pentachlorophenol and Sodium Pentachlorophenate...

Octachlorodibenzo- -dioxin. Pentachlorophenol was purified by sublimation and recrystallization to yield a product with the following composition trichlorophenol, 0.04% tetrachlorophenol, 0.07% and pentachlorophenol, 100.4 1%. Pentachlorophenol (300 grams, 1.13 mole) was dissolved in 900 ml of trichlorobenzene and chlorinated anhydrously for 18 hours at reflux. Ghlorine addition was stopped and the mixture was heated for 28 more hours at reflux. The crystalline product was washed with 2-liter portions of chloroform, IN NaOH, methanol, and water. Analysis by GLG suggested the presence of 5-15% heptachloro-dibenzo-p-dioxin. The mixture was carefully added to a cleaning solution of 200 ml water, 3.5 liters sulfuric acid, and 125 grams sodium dichromate. The mixture was heated at 150 °G for six hours. The product was recrystallized from hot o-dichlorobenzene and then from anisole. The purified product (160 grams, mp 329.8° 0.5°G) contained <0.1% heptachlorodibenzo-p-dioxin, determined by GLG. 

Macdonald RW, WJ Cretney, N Crewe, D Patou (1992) A history of octachlorodibenzo-/ -dioxin, 2,3,7,8-tetrachlorodibenzofuran, and 3,3, 4,4 -tetrachlorobiphenyl contamination in Howe Sound, British Columbia. Environ Sci Technol 26 1544-1550. 

Nonachloro-5,5-dihydrox3q)enta-cyclo[5.3.0.0 .0 .0 ]decane, see Kepone Nonanal, see Nonane Nonanoic acid, see Nonane 1-Nonanol, see Nonane 1-Nonene, see Nonane Nonyl hydroperoxide, see Nonane Norchloralachlor, see Alachlor Octachlorobiphenyl, see Pentachlorobenzene Octachlorocyclopentene, see Hexachlorobutadiene Octachlorodibenzo-/>dioxin, see Pentachlorophenol Octachlorodiphenylene dioxide, see Pentachlorophenol l,2,3,4,4a,9,10,10a-0ctahydrophenanthrene, see Phenanthrene... 

SYNS NCI-C03678 OCDD OCTACHLORO-DIBENZO(b,e)(l,4)DIOXIN OCTACffl-ORODIBENZO-p-DIOXIN 1,2.3,4,6,7,8,9-OCTACHLORODIBENZO-DIOXIN... 

We report the crystal structures of four chlorinated dioxins—the 2,7-dichloro-, 2,8-dichloro-, 2,3,7,8-tetrachloro-, and octachlorodibenzo-p-dioxins. Thus, five crystal structures of chlorodioxins are now known. 

Figure 4. Bond distances and angles for octachlorodibenzo-p-dioxin. The molecule is located on an inversion center.

Figure 13. ESR spectrum of octachlorodibenzo-p-dioxin in TFMS acid...

Chlorinated dibenzo ip-dioxins are contaminants of phenol-based pesticides and may enter the environment where they are subject to the action of sunlight. Rate measurements showed that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is more rapidly photolyzed in methanol than octachlorodi-benzo-p-dioxin. Initially TCDD yields 2,3,7-trichlorodiben-zo-p-dioxin, and subsequent reductive dechlorination is accompanied by ring fission. Pure dibenzo-p-dioxin gave polymeric material and some 2,2 -dihydroxybiphenyl on irradiation. Riboflavin-sensitized photolysis of the potential precursors of dioxins, 2,4-dichlorophenol and 2,4,5-trichloro-phenol, in water gave no detectable dioxins. The products identified were chlorinated phenoxyphenols and dihydroxy-biphenyls. In contrast, aqueous alkaline solutions of purified pentachlorophenol gave traces of octachlorodibenzo-p-dioxin on irradiation. 

The photolysis rate of several chlorinated dioxins was determined in methanol (20) (Figure 1). Solutions of 2,7-dichlorodibenzo-p-dioxin (5 mg/liter), TCDD (5 mg/liter), and octachlorodibenzo-p-dioxin (2.2 mg/ liter) were irradiated with light having an intensity of about 100 /mW/cm ... 

Figure 1. Photolysis rates of chlorinated dibenzo-p-dioxins in methanol under ultraviolet light 2J-dichlorodibenzo-p-dioxin (III) (5 mg/liter), 2,3,7,8-tetrachlorodiben-zo-p-dioxin (I) (5 mg/liter), 1,2,3,4,6,7,8,9-octachlorodibenzo-p-dioxin (IV) (2.2 mg/ liter) (20), 1971 by AAAS...

Octachlorodibenzo-p-dioxin was photolyzed much more slowly than TCDD (Figure 1). The rate of dioxin photolysis increased as the number of substituent chlorine atoms decreased. Octachlorodibenzo-p-dioxin gave what seemed to be a series of chlorinated dioxins of decreasing chlorine content (20). 

PCP presents a different picture from that of the lower chlorophenols and their derivatives. The corresponding dioxin shows much more stability to light than does TCDD, enough to permit its prolonged existence at low concentrations in a photoreactor. As a phenol it can directly yield dioxins, a process favored by its normal mode of application as the sodium salt. Although octachlorodibenzo-p-dioxin has much lower mammalian toxicity than TCDD (6), its formation, properties, and effects demand additional investigation. Technical preparations of PCP are frequently mixtures of tetra- and pentachlorophenols consequently, hepta-and possibly hexachlorodibenzo-p-dioxins might be expected as photolysis products in addition to the octachloro derivative. 

The toxicity of chlorodibenzodioxins other than those evaluated in this study has not been reported. Purified samples of trichloro-, penta-chloro-, and heptachlorodibenzo-p-dioxin which are free of tetrachloro-and hexachlorodibenzo-p-dioxin need to be synthesized for study. However, heptachlorodibenzo-p-dioxin cannot be highly toxic since studies on octachlorodibenzo-p-dioxin containing several percent of heptachloro-dibenzo-p-dioxin have tested the same as the pure product. 

Studies on the chlorodibenzodioxins have led to the following conclusions (1) 2,7-dichlorodibenzo-p-dioxin and octachlorodibenzo-p-di-oxin have a low acute toxicity (2) 2,3,7,8-tetrachlorodibenzo-p-dioxin has an unusually high toxicity (3) hexachlorodibenzo-p-dioxin is highly toxic but less toxic than 2,3,7,8-tetrachlorodibenzo-p-dioxin (4) all chlorodibenzodioxins are not alike in their toxicological properties. Isomers of the same dibenzo-p-dioxin vary in toxicological properties, making it important to identify them specifically. 

Effects of Combustion and Heat. The results of combusting wood and paper treated with pentachlorophenol or sodium pentachlorophenate are shown in Table I. These results indicate that octachlorodibenzo-p-dioxin concentration did not increase as the result of combusting either wood or paper treated with pentachlorophenol. It seems that the concentration of octachlorodibenzo-p-dioxin concentration was actually decreased during combustion. However, paper treated with sodium pentachlorophenate did increase in octachlorodibenzo-p-dioxin concentration as the result of combustion. 

Table IV. Octachlorodibenzo-/F-dioxin in Irradiated Solutions in pH 8 Phosphate Buffer...

A small amount of octachlorodibenzo-p-dioxin, amounting to approximately 0.03%, was formed during the photolysis of sodium penta-chlorophenol buffered at pH 8 as shown by the data in Table IV. 

Very little change was observed in the octachlorodibenzo-p-dioxin on exposure to artificial sunlight. Over extended periods of time (18—24 hours) there was some evidence of decay. Approximately 20% photolysis was observed in isooctane at the end of 18 hours and about 6% photolysis of the octachlorodibenzo-p-dioxin after 20 hours exposure in 1-octanol. 

Combustion of wood or paper treated with pentachlorophenol resulted in no increase and more probably a decrease in octachlorodi-benzo-p-dioxin concentrations while octachlorodibenzo-p-dioxin increased slightly in paper treated with sodium pentachlorophenate. The pho-tolytic degradation of sodium pentachlorophenate at pH 8 is very rapid. Under these controlled conditions formation of no more than 0.03% octachlorodibenzo-p-dioxin was observed. The 2,3,7,8 isomer, one of the most active chloracnegens is seemingly stable towards air oxidation but... 

Chlorinated dibenzo-ip-dioxins were prepared on the gram scale for use as toxicological standards, 2,7-Dichlorodi-henzo-p-dioxin was prepared by catalytic condensation of potassium 2-bromo-4-chlorophenate in 70% yield. Thermal condensation of the potassium salt of 2,4,4 -trichloro-2 -hydroxy diphenyl ether gave a mixture of the 2,8- and 2,7-dichlorodibenzo-p-dioxins which were separated by fractional recrystallization. 2,3,7,8-T etrachlorodibenzo-p-dioxin of 99.9- -% purity was prepared by catalytic condensation of potassium 2,4,5-trichlorophenate. An isomeric mixture of hexachlorodibenzo-p-dioxins was prepared by pyrolytic condensation of sodium 2,3,4,6-tetrachlorophenate. Chlorination of pentachlorophenol (containing < 0.07% tetrachlorophenol) in trichlorobenzene gave octachlorodi-benzo-p-dioxin in 80% yield contaminated by 5-15% heptachlorodibenzo-p-dioxin. Oxidative methods were used to produce octachlorodibenzo-p-dioxin at 99.9% purity. 

The most convenient and successful synthetic preparation of octa-chlorodibenzo-p-dioxin has been described by Kulka (13). The procedure involves chlorination of pentachlorophenol in refluxing trichlorobenzene to give octachlorodibenzo-p-dioxin in 80% yield. Kulka has explained the reaction as coupling between two pentachlorophenoxy radicals. Large amounts (5—15%) of heptachlorodibenzo-p-dioxin were observed in the unpurified product. Since the pentachlorophenol used in this study contained 0.07% tetrachlorophenol, we feel that tetrachloro-phenol may be produced in situ (Reaction 4). Such a scheme would be analogous to the formation of 2,4-dichlorophenol and 3-chlorophenol produced from 2,4,4 -trichloro-2 -hydroxydiphenyl ether (Reaction 2). The solubility of octachlorodibenzo-p-dioxin was determined in various solvents data are presented in Table II. 

It has been suggested that the photochemical reaction of pentachlorophenol in aqueous solution to produce octachlorodibenzo[l,4] dioxin and some of the heptachloro congener could account for the discrepancy between values for the emission of chlorinated dioxins and their deposition, which is significant for the octachloro congener (Baker and Hites 2000). 

Other componnds have also been examined as primers for the dechlorination of hexachloro to nonachloro PCB congeners (DeWeerd and Bedard 1999) a nnmber of snbstituted brominated monocyclic aromatic componnds were examined, and 4-bromobenzoate was effective—though less so than 2,6-dibromobiphenyl. In contrast, the chlorobenzoates that are metabolites of aerobic degradation were ineffective. The positive effect of brominated biphenyls in priming the anaerobic dechlorination of CBs has also been encountered in the dechlorination of octachlorodibenzo[l,4] dioxin to the 2,3,7,8 congener indnced by 2-bromodibenzo[l,4]dioxin in the presence of (Albrecht... 

Chlorinated dioxins occur in atmospheric deposition (Koester and Hites 1992), and will thereby enter the terrestrial environment and watercourses. The degradation of tetrachloro- through octa-chlorodibenzo[l,4]dioxins has been examined in low-nitrogen medium by Phanerochaete sor-dida YK-624 (Takada et al. 1996). All the compounds were extensively degraded, and the ring fission of 2,3,7,8-tetra- and octachlorodibenzo[l,4]dioxin produced 4,5-di- and tetrachlorocatechol. These results established important evidence for the biodegradability of even highly chlorinated dibenzodioxins. 

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