Perchlorination

BMC A very powerful perchlorinating agent (to replace all H by Cl) prepared from S2CI2, SO2CI2 and AICI3. 

Hexachloroethane is formed in minor amounts in many industrial chlorination processes designed to produce lower chlorinated hydrocarbons, usually via a sequential chlorination step. Chlorination of tetrachloroethylene, in the presence of ferric chloride, at 100—140°C is one convenient method of preparing hexachloroethane (142). Oxychlorination of tetrachloroethylene, using a copper chloride catalyst (143) has also been used. Photochemical chlorination of tetrachloroethylene under pressure and below 60°C has been studied (144) and patented as a method of producing hexachloroethane (145), as has recovery of hexachloroethane from a mixture of other perchlorinated hydrocarbon derivatives via crystalH2ation in carbon tetrachloride. Chlorination of hexachlorobutadiene has also been used to produce hexachloroethane (146). 

Other well-known reactions are those offluorinated olefins with fluoride ion and negatively substituted aromatic compounds leading to the formation of per-fiuoroalkylated aromatic compounds The reaction may be considered an amonic version of a Fnedel Crafts process and can result in introduction of one or several perfluoroalkyl substituents [/ /] Aromatic substrates include substituted and unsuhstiluled perfiuorobenzenes [J3l, 212, 213, 214], fiuorinated heterocycles [131, 203, 215, 216, 217, 218, 219, 220, 221, 222, 223],perchlorinated heterocycles [224] (equation 44), and other activated aromatic compounds [225] (equation 45) The fluonnated olefins can be linear or cyclic [208] (equation 46)... 

Chlorination. When 75 was treated with chlorine in the presence of aluminium chloride, initial chlorination took place at the 5-position, but the reaction was rather unselective 5,8-di-, 5,7,8-tri-, and 5,6,7,8-tetra-chloroisoquinolines were also formed (64JOC329). Perchlorination has been achieved by initial reaction of the isoquinoline-aluminium chloride complex with chlorine, as above, followed by treatment with phosphorus pentachloride at 270°C in an autoclave [66JCS(C)2328]. Treatment of 1,8-dimethylisoquinoline with NCS gave the 5-chloro derivative (91NKK-1193). Meisenheimer reaction of isoquinoline 2-oxides with phosphoryl chloride gave 1-chloroisoquinoline (84MI2). 

Yoon and co-workers prepared perchlorinated pyridazines via chlorination of pyridazone 164 <00JHC1049>. They reported that the chlorination of 164 using phosphorus oxychloride gave only 165 in 81% yield. However, a solution of phosphorus pentachloride and cyclohexane provided only 166 in 81% yield. Furthermore, other reaction conditions gave a mixture of 165 and 166 in varying ratios depending upon the solvent, temperature, and reaction time. 

The technique of perchlorinating the two aromatic rings surprisingly enhances both the tinctorial strength and the fastness properties of the product considerably. This quality increase is notably attributed to factors which are described in detail in Sec. 2.11.2. 

Perchlorination and GC Organic Compounds in Drinking Water (EPA/600/4-88-039), December 1988, Revised July 1991... 

A more detailed mechanistic study was performed recently for the thermal conversion of perchlorinated aliphatic C-6 polyenes like C6C18 into hexachloroben-zene (see Figure 8.5). 

Determination of Chlorinated Pesticides in Water by GC with an ECD 508A Screening for Polychlorinated Biphenyls by Perchlorination and GC... 

The fungitoxic N-perhalogenmethylmercapto moiety was introduced for plant protection in 1950 The. two fungicides captan(l) (N-(trichloromethylthio)-tetrahydrophthalimide and folpet(2) (N-(trichlorome-thylthio)phthalimide) contain a perchlorinated methyl-thio group (1 ). About a decade later substitution of fluorine for one of the chlorines in the perchloro-... 

Phenoxathiin and thianthrene can be chlorinated without oxidation into the corresponding sulfoxides using sulfuryl chloride and AICI3 to form the 2,3,7,8-tetrachloro derivatives 41 and 42, respectively. Use of BMS reagent- a mixture of sulfur monochloride, sulfuryl chloride, and aluminium chloride - results in exhaustive chlorination of phenoxathiin and thianthrene with formation of perchlorinated products 43 and 44. It is noteworthy that using sulfuryl chloride in dichloromethane, the sulfoxides were isolated as the major products <1997CHE333>. 

Perchlorinated DPC also gave a carbene dimer when generated in... 

Attempted perchlorination of the parent TP (PC15, 220°C) leads to tetrachloropyrimidine (76JHC139). 

Kliolkute SD, Rodriguez J, Dukelow WR. 1994. The effects of polybrominated biphenyls and perchlorinated terphenyls on in vitro fertilization in the mouse. Arch Environ Contam Toxicol 26(2) 208-211. 

Japanese workers218 report the formation of 2-alkyl-3-halopyrazolo[l,5-ajpyridines from the corresponding 3-acyl derivatives, whereas attempted perchlorination of 5 with phosphorus pentachloride in a steel bomb gave a 48% yield of perchloropyridine.219... 

Chlorination of the pyrido [ 1,2-a]pyrimidine (189) yielded a perchlorinated pyridine derivative (281).244 Perhydropyrido[l,2-a]pyrimidine (282) is sensitive towards acids, with ring cleavage to 283 taking place.191 The latter can be recyclized by alkali.192 Hydrogenation in concentrated hydrochloric acid over platinum(IV) oxide yields l-(3-aminopropyl)piperidine.192,342 Hydrogenation over Raney nickel in the presence of acetaldehyde leads to 1-ethylperhydropyrido [ 1,2-a]pyrimidine.237... 

Perchlorinated vinylpyridines were reduced to pyridylacetylenes where none, one, or more halogens were also removed from the aromatic nucleus (Scheme 28).136 Attempts to dehalogenate the trichloromethylcarbinol (88)... 

The synthesis of fluotrimazole starts from m-xylene. Peroxide catalyzed perchlorination converts this to m-trichloromethyl-benzo-trichloride. m-Trichloromethyl-benzotrifluoride is then obtained by selective chlorine/fluorine exchange. This key product is also readily accessible on a technical scale by conproportionation of the two corresponding m-trihalomethyl-benzotrihalogenides. Friedel-Crafts reaction with benzene leads to trifluoromethyl-tritylchloride, which reacts smoothly with 1,2,4-triazole in polar solvents to give fluotrimazole. 

---