2.8.10.10- tetrachloro chlorine

Anthraquinone can be brominated, chlorinated directly to the tetrachloro (I, 4, 5, 8-) stage, nitrated easily in the 1-position, but gives the 1,5-and 1,8-dinitro-derivalives on prolonged nitration the nitro groups in these compounds are easily displaced by neutral solutions of alkali sulphites yielding the corresponding sulphonic acids. Sulphonation with 20-30 % oleum gives the 2- 2,6- and 2,7-derivatives in the presence of Hg the 1- 1,5- and 1,8- derivatives are formed. 

Bromination in polar solvents usually gives /n j -3,4-dibromo-2-methyl-3-buten-2-ol in nonpolar solvents, with incandescent light, the cis isomer is the principal product (194). Chlorine adds readily up to the tetrachloro stage, but yields are low because of side reactions (195). 

Tetrachlorotoluene, C H Cl (mol wt 229.93) (1,2,3,5-tetrachloro-4-methylben2ene), is prepared from the Sandmeyer reaction on 3-arnino-2,4,6-trichlorotoluene. 2,3,4,5-Tetrachlorotoluene (l,2,3,4-tetrachloro-5-methylben2ene) is the principal isomer in the further chlorination of 2,4,5-trichlorotoluene. Exhaustive chlorination of -toluenesulfonyl chloride, followed by hydrolysis to remove the sulfonic acid group yields... 

In the case of phenazine, substitution in the hetero ring is clearly not possible without complete disruption of the aromatic character of the molecule. Like pyrazine and quinoxa-line, phenazine is very resistant towards the usual electrophilic reagents employed in aromatic substitution reactions and substituted phenazines are generally prepared by a modification of one of the synthetic routes employed in their construction from monocyclic precursors. However, a limited range of substitution reactions has been reported. Thus, phenazine has been chlorinated in acid solution with molecular chlorine to yield the 1-chloro, 1,4-dichloro, 1,4,6-trichloro and 1,4,6,9-tetrachloro derivatives, whose gross structures have been proven by independent synthesis (53G327). 

Compounds in which conformational, rather than configurational, equilibria are influenced by the anomeric effect are depicted in entries 4—6. Single-crystal X-ray dilfiaction studies have unambiguously established that all the chlorine atoms of trans, cis, ira j-2,3,5,6-tetrachloro-l,4-dioxane occupy axial sites in the crystal. Each chlorine in die molecule is bonded to an anomeric carbon and is subject to the anomeric effect. Equally striking is the observation that all the substituents of the tri-0-acetyl-/ -D-xylopyranosyl chloride shown in entry 5 are in the axial orientation in solution. Here, no special crystal packing forces can be invoked to rationalize the preferred conformation. The anomeric effect of a single chlorine is sufficient to drive the equilibrium in favor of the conformation that puts the three acetoxy groups in axial positions. 

Although interesting from a mechanistic point of view, alkane halogenation is a poor synthetic method for preparing alkyl halides because mixtures of products invariably result. For example, chlorination of methane does not stop cleanly at the monochlorinated stage but continues to give a mixture of dichloro, trichloro, and even tetrachloro products. 

Transformations which alter the bacteriochlorin chromophore are quite rare. An important reaction in the structural elucidation of the bacteriochlorophylls is the dehydrogenation to chlorophyll derivatives. Thus, bacteriopyromethylpheophorbide a (1) can be smoothly dehydrogenated with 3,4,5,6-tetrachloro-l,2-benzoquinone to the corresponding chlorin 3-acetyl-pyromethylpheophorbide a (2) in high yield.1 la,b... 

In chlorinations either a substitution or an addition process can occur with the ultimate reaction pathway(s) determined by a combination of factors, which include the reaction conditions, the positions and natures of any substituents present, and the catalyst used. Uncatalyzed chlorination of benzothiadiazole is an exothermic reaction that gives rise to a mixture of isomeric tetrachloro addition products. These are converted in basic medium into 4,7-dichloro-2,1,3-benzothiadiazole (70RCR923). When an iron(III) catalyst is present 4- and 7-chloro substitution becomes the dominant process. Chlorination of a number of 4-substituted 2,1,3-benzothiadiazoles (43) using an oxidative process gave a combination of chlorinated and oxidized products. The 4-hydroxy, 4-amino-, 4-methyl-amino, and 4-acetoxy derivatives of 43 all formed the chloroquinones (44) (40-61% yields). With the 4-aIkoxy substrates both 44 and some 5,7-dichlorinated product were obtained (88CHE96). 

Chlorination. Electrophilic chlorination of quinoline (66) in neutral medium showed a positional selectivity order of 3 > 6 > 8. The 5- and 8-positions should be sterically hindered to some extent. Hammett cr+ values predict an order for electrophilic substitution of 5 > 8 = 6 > 3. Treatment with chlorine at 160-190°C converted quinoline into a mixture of 3-chloro-, 3,4-dichloro-, 3,4,6- and 3,4,8-trichloro-, 3,4,6,8-tetrachloro-, and 3,4,6,7,8-pentachloro-quinolines. At lower temperatures ( 100°C) the major product was 3-chloroquinoline, albeit in low yield. The 4-substituted species may have arisen from an addition-elimination or radical process (70JHC171). 

Polychlorination processes have included exhaustive chlorination in the presence of antimony pentachloride, which destroyed the molecule (1882JCS412). Chlorine in carbon tetrachloride gave 3,4,6,8-tetrachlo-roquinoline chlorine dissolved in thionyl chloride gave the 4,5,7,8-isomer, whereas thionyl chloride alone produced a mixture of 3,4,5,6,7,8-hexachloro- (57%) and 3,4,6,8-tetrachloro- (37%) quinolines (73YZ73 74S356, 74URP432143). 

With phenazine (97) there is considerable resistance to any electrophilic halogenation, but in aqueous solution chlorine converted it into a mixture of 1-chloro, 1,4-dichloro-, 1,4,6-trichloro-, and 1,4,6,9-tetrachloro-phenazines (53G327). 

Exhaustive chlorination of 101 gave a mixture of polychloro derivatives with the 2,3,7,8-tetrachloro species as the major product. To achieve such C-halogenation it is necessary to choose a reaction medium that avoids hydrolysis of the initially formed 5-halides to 5-oxides [76USP3989715 90AHC(48)301]. The 1-halogenated derivatives of 100 and 101 can be readily prepared from the lithiated species (84MI14). 

Tetrachloro-4-methylacetophe-none from aluminum chloride catalyzed chlorination of p-methylacetophenone, 40, 10... 

Some PCB congeners have coplanar structures (see, e.g., 3,4,3, 4 -tetrachloro-biphenyl in Figure 6.1). The coplanar conformation is taken up when there is no chlorine substitution in ortho positions. If there is substitution of chlorine in only one ortho position, the molecule may still be close to coplanarity, because of only limited interaction between Cl and H on adjoining rings. Substitution of chlorines in... 

Dichlorodibenzo-p-dioxin was prepared from isotopic potassium 2,4-dichlorophenate uniformly labeled with Ullman conditions gave a 20.5% yield. Small amounts of dichlorophenoxy chlorophenol were removed from the product by extraction with sodium hydroxide before purification by fractional sublimation and recrystallization from anisole. Chlorination of 2,7-dichlorodibenzo-p-dioxin in chloroform solution containing trace amounts of FeCls and 12 yielded a mixture of tri-, tetra-, and pentachloro substitution products. Purification by digestion in boiling chloroform, fractional sublimation, and recrystallization from anisole was effective in refining this product to 92% 2,3,7,8-tetrachloro isomer, which also contained 7% of the tri- and 1% of the penta-substituted dibenzo-p-dioxin. Mass spectroscopy was used exclusively to monitor the quality of the products during the synthesis. 

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. 

Three isomeric tetrachlorodibenzo-p-dioxins were studied. All were insoluble in TFMS acid. To dissolve these compounds and form cation radicals, UV irradiation was necessary. The 1,2,3,4-tetrachloro compound was particularly sensitive to UV irradiation, and as a solid, even turned pink when exposed to ordinary fluorescent light. When subjected to constant UV irradiation, radical ions were induced rapidly. The change in the cation radical concentration was monitored by the ESR signal as illustrated in Figure 10. To determine whether the tetrachloro isomer had been converted to lower chlorinated derivatives after UV irradiation, the dissolved dioxin was then poured into ice water and recovered. The GLC retention time of the recovered dioxin was unchanged in addition, no new GLC peaks were observed. Moreover, the ESR spectrum see Figure 11) for the recovered material was not altered between widely... 

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. 

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. 

In a related reaction, enolate 71 is undergoing an electrophilic chlorination with 2,2,6,6-tetrachloro-cyclohexanone (74, Fig. 39), eventually leading to a-chlorinated enol esters 75 [91]. However, a different mechanism cannot be completely ruled out, where the catalyst is not acylated by the ketene, but chlorinated by the tetrachloro-ketone to form [64c-Cl] as the reactive species. 

The bleaching process, in contrast, poses major difficulties. Traditional paper bleaching uses chlorine gas, which is reduced to chloride anions, cr, as it oxidizes the colored pigments in wood pulp. The chloride anion is not a pollutant, as it is a major species in the oceans. Unfortunately, chlorine processing also generates small quantities of chlorine-containing dioxins such as 2,3,7,8-tetrachloro-dibenzo-p-dioxin, whose stmcture (below) appears less formidable than its name ... 

Chlorine-substituted quinones, and especially chloranil (i.e., tetrachloro-quinone), are predominantly transfer agents rather than inhibitors. Nuclear substitution as in the first step of reaction (55) may be involved with subsequent transfer of a chlorine atom to a monomer molecule. ... 

Partial anaerobic dechlorination of chlorinated dibenzo[l,4]dioxins has been observed in sediment slurries. The 1,2,3,4-tetrachloro compound produced predominantly l,3-dichlorodibenzo[l,4]-dioxin (Beurskens et al. 1995 Ballerstedt et al. 1997), and for substrates with five to seven chlorine substituents, chlorine was removed from both the peri and the lateral positions (Barkovskii and... 

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. 

Butadiene derivatives add chlorine under sunlight to produce tetrachloro-compounds(106) ... 

Tian and co-workers [148] have reported the synthesis of two chlorinated fluoresceins probes 4,7,2,7 -tetrachloro-6-(5-carboxypentyl) fluorescein and 4,7,4,5 -tetrachloro-6-(5-carboxypentyl) fluorescein for labeling proteins. More recently, the same research group has described the synthesis of two novel chlorinated fluoresceins, namely 2,4, 5, 7 -tetrachloro-6-(5-carboxypentyl)-4,7-dichloro fluorescein succinimidyl ester 52 and 2, 4, 5, 7-tetrachloro-6-(3-carboxypropyl)-4,7-dichlorofluorescein succinimidyl ester 53 [149]. 

Preparation of 4,5,6,7-tetrabromobenzotriazole and its tetrachloro analog by direct bromination or chlorination of benzotriazole is described in Section 5.01.7. However, other tetra-substituted benzotriazoles have to be constmcted from a suitably substituted benzene ring. Thus, treatment of pentamethylbenzene 1293 with fuming nitric acid in concentrated sulfuric acid provides 3,4,5,6-tetramethyl-l,2-dinitrobenzene 1294 in 66% yield. Using routine procedures, derivative 1294 is reduced with SnCl2 in aqueous HC1, and the obtained diamine 1295 is subsequently treated with NaNOz (in aq. HC1) to provide 4,5,6,7-tetramcthyl-l //-benzotriazole 1296 (Scheme 216) <2004BMC2617>. 

---