Pentachloro-benzene

A plot of the total quantum yield versus the concentration of pentachloro-benzene provides a very nice linear plot (r = 0.995) (Fig. 2), suggesting that (kT + k,d) > k2[l]. Thus, by extrapolation of [1] to zero, one can calculate the quantum yield independent of triplet excimer (siaglet + triplet)- Subtraction of the quantum yields for direct fission from singlet and triplet states ( si gIe, + triplet) from ToM provides the expression for the dependence of the remainder ( ) upon concentration (Eq. 7). A plot of the reciprocal (l/cx) versus the reciprocal of the concentration of the substrate is linear (r = 0.950), which is consistent with the mechanism and is illustrated in Fig. 3 [2]. 

Fig. 2. Plot of the quantum yield of photodechlorination versus the concentration of pentachloro-benzene...

In a complementary study an interest in the mechanistic pathways which are operative in micellar media led to a characterization of the triplet pentachloro-benzene excimer. Pentachlorobenzene (1) was irradiated in 0.100 M CTAB (hexadecyltriethylammoniumbromide) aqueous solution at 254 nm. The major dechlorinated products were the tetrachlorobenzenes (2—4) with an accompanying trace of trichlorobenzenes. Bromotetrachlorobenzenes were observed as byproducts [19]. Building on our results in homogeneous solution, the mechanism for photohydrodehalogenation is represented in Scheme 3. Since... 

Nevertheless, because of compelling needs closely related to the synthesis of some substituted inert free radicals (Section 9), that Friedel-Crafts condensation has recently been explored, using as alkylating components a//-chlorocompounds (such as a//-heptachlorotoluene, and a//-undeca-chlorodiphenylmethane) and even chloroform. With aromatic substrates, such as 1,3,5-trichlorobenzene, 1,2,4,5-tetrachlorobenzene and pentachloro-benzene, good-to-excellent yields of the expected a//-arylmethanes are obtained. Examples are shown in (74). Such condensations take place in... 

Using pentachlorobenzene as a promoter and di-ethylnitrosamine as an initiator, Thomas etal. (2000) applied two types of models for describing the time-course models in glutathione S-transferase n foci. The two cell model, which was parameterized to describe a negative selection mechanism, produced adequate simulations of both the site and number of foci. This model-based analysis suggested that the differences between pentachloro-benzene-treated and imtreated rats were primarily in parameters involving the rates of cell death. 

Dichloro- benzene 1,4- Dichloro- benzene 1,3,5- Trichloro- benzene 1,2,4- Trichloro- benzene 1,2,3- Tricholoro- benzene 1,2,4,5-Tetrachloro-benzene 1,2,3,4,-Tetrachloro-benzene Pentachloro- benzene Hexachloro- benzene... 

Reaction of 2-cyanomethylpyridine with iV-(l-aryl-l-chloro-2,2,2-trifluoroethyl)-iV -(4-methylphenyl)carbodiimides, and with (1,1,2,2,2-pentachloro- and l,l-dichloro-2,2,2-trifluoroethyl)isocyanates or A-methoxycarbonyl-l,2,2,2-tetrachloro-, — l-chloro-2,2-trifluoroacetaldehyde imines afforded 3-aryl-4-cyano-l-(4-methylphenyl)imino-3-trifluoromethyl-2,3-dihydro-17/-pyrido[l,2-f]pyrimidines and 4-cyano-3-trichloro-, 4-cyano-3-trifluoro-17/-pyrido[l,2-4pyrimidin-l-ones, respectively <2004CHE47>. Refluxing 2-cyanomethylpyridine and iV-(l-aryl-l-chloro-2,2,2-trifluoroethyl)isocyanates in benzene furnished l-aryl-4-cyano-l-trifluoromethyl-l,2-dihydro-3//-pyrido[l,2-4pyrimidin-3-ones. However, when the solution of the isocyanate was added dropwise to the solution of 2-cyanomethylpyridine, and the reaction mixture was then treated with NEt at room temperature, the isomeric 3-aryl-4-cyano-3-trifluoromethyl-2,3-dihydro-l//-pyr-ido[l,2-dpyrimidin-l-ones were obtained. Reaction of l-(acetyl- and benzoylmethylene)-6,7-dimethoxy-l,2,3,4-tetra-hydroisoquinolines with PhCONCS yielded 1-acetyl-, 1 -benzoyl-9,10-dime thoxy-3-pheny 1-6,7-dihydro-2//-pyrimido[6,l- ]isoquinoline-2-thiones <2003SL2369>. 

A subsequent elimination of hydrogen halide prompted by the lability of halogen on the carbon attached to nitrogen, a second halogen addition, and a repetition of the cycle must account for the reported formation of 9-pentachloro- and 9-pentabromoethylcarbazoles on reaction with excess halogen in methanol and acetic acid, respectively. Addition of bromine to IV-vinylcarbazole in benzene as solvent was accompanied by 3,6-dibromi-nation in ethanol, 3,6-dibromo-9-(2-bromo-l-ethoxyethyl)carbazole was reportedly formed (cf. ref. 230). 

Synonyms HCB Perchlorobenzene Pentachloro-phenyl chloride Benzene, hexachloro- Esacloro-benzene (Italian) Hexachlorobenzol (German) Julin s carbon chloride Phenyl perchloryl Chemical/Pharmaceutical/Other Class Organo-chlorine... 

Synonyms Pentachloro(trichloroethenyl)-benzene Chemical/Pharmaceutical/Other Class Octachlorostyrene is a persistent, bioaccumulative, halogenated aromatic compound. Related compounds include other chlorinated styrenes that... 

With monosubstituted benzenes, the tendency of OH to undergo ipso addition seems to be small (<10%). However, if the ipso position is activated by a second substituent like CH3O, HO or 0 , ipso addition may contribute up to 25% to the overall reactivity . Due to the small size of the OH radical, steric effects (i.e. the size of X) do not seem to be of mnch importance in determining the probability of OH attack at the ipso position. Oxidative replacement of halogen has been observed also with pentafluoro-, pentachloro-, pentabromo- and 2,4,6-triiodo-phenol, where it occurs in parallel to electron transfer". ... 

Although niclosamide itself possesses two chioro groups, one each in both the benzene rings, it was considered rational to study the impact of further chioro substitution on the net biological response of the resulting molecules. Accordingly, 3,3, 5,5, 6 -pentachloro-2 -hydroxysalicylanilide (oxyclozanide, 7) was developed in the ICI laboratories, which is widely used to eliminate adult flukes of Fasciola Iiepatica from sheep and cattle at a dose of 80 and 40 mg/kg, respectively [11,16]. 

The questions raised by Kekule s interpretation of the mechanism of this reaction led to a number of investigations which involved a further study of the oxidation of aromatic phenols and quinones. Thus, for example, Zincke in collaboration with Kuster48 and Rabinowitch 4 undertook a systematic investigation of the action of chlorine (potassium chlorate plus hydrochloric acid) on various derivatives of the three dihydroxybenzenes. The results of these experiments showed that these classes of benzene derivatives split up under conditions to give aliphatic compounds. The intermediate compounds which were formed from tetrahydrobenzene during these transfonnations, were identified as the hexachloro-o-diketone derivative (I) and the pentachloro-m-diketone derivative (II). 

U017. . Benzal chloride U183. . Benzene, pentachloro... 

Nucleophilic attack of pentachlorophenoxide ion (from either pentachloro-phenol or silver pentachlorophenoxide) on dibromotriphenylphosphorane (triphenylphosphine dibromide) yields bromo(pentachlorophenoxy)tri-phenylphosphorane (Espinosa, 1972). In benzene, the latter exists, at least partly, as the isomeric salt (pentachlorophenoxy)triphenylphosphonium bromide [88]. This salt hydrolyses to a 1 1 adduct of pentachlorophenol and triphenylphosphine oxide, reproducible by just mixing its components (89). 

Chlorobenzene o-Dichloro-benzene Pentachloro- ethane intensity... 

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