Pyrene chlorination

Aerobic, Anaerobic, and Combined Systems. The vast majority of in situ bioremediations ate conducted under aerobic conditions because most organics can be degraded aerobically and more rapidly than under anaerobic conditions. Some synthetic chemicals are highly resistant to aerobic biodegradation, such as highly oxidized, chlorinated hydrocarbons and polynuclear aromatic hydrocarbons (PAHs). Examples of such compounds are tetrachloroethylene, TCE, benzo(a)pyrene [50-32-8] PCBs, and pesticides. 

It is thought that the chlorination proceeds through a ir-com-plex between cupric chloride and anthracene, and that this complex then undergoes homolytic dissociation. Hence aromatic rings subject to attack by chlorine atoms can be chlorinated in this way. Thus one can convert pyrene to 1-chloropyrene (90% yield), but phenanthrene is not chlorinated. Analogous procedures using cupric bromide lead to 9-bromoanthracene (99% yield) and 1-bromopyrene (94% yield).7... 

Pyrene is a common PAH contaminant and may occur in drinking water. Chlorination of water with or without bromide that may be present in coastal environments has been examined. Both chlorinated and brominated pyrenes with halogen substituents at the 1,3-, 1,6-, and 1,8-positions were found, and could putatively be produced by reaction of pyrene with hypochlorous acid and hypochlorite (Hu et al. 2006). 

Hu J, X Jin, S Kunikane, Y Terao, T Aizawa (2006) Transformation of pyrene in aqueous chlorination in the presence and absence of bromide kinetics, products, and their aryl hydrocarbon receptor-mediated activities. Environ Sci Technol 40 487-493. 

Figure 5.16. Plot of data for the external heavy-atom quenching of pyrene fluorescence in benzene at 20°C. Polaro-graphic half-wave reduction potentials Ein are used as a measure of the electron affinity of the quencher containing chlorine (O), bromine ( ), or iodine (3). From Thomaz and Stevens<148) with permission of W. A. Benjamin, New York.

A different synthetic route involves halogenation (bromination, chlorination) of pyrene 77, which is thus converted to the tetrahalogen derivative. Oxidation with sulfuric acid to form a diperinaphthindandione with subsequent oxidation, once again in a sodium hydroxide solution [7], yields the tetra sodium salt of naphthalene tetracarboxylic acid 78 ... 

When benzo[a]pyrene adsorbed from the vapor phase onto coal fly ash, silica, and alumina was exposed to nitrogen dioxide, no reaction occurred. However, in the presence of nitric acid, nitrated compounds were produced (Yokley et al, 1985). Chlorination of benzo [a] pyrene in polluted humus poor lake water gave ll,12-dichlorobenzo[a]pyrene and 1,11,12-, 3,11,12- or 3,6,11-... 

Polycyclic aromatic hydrocarbons (PAH), which are ubiquitous in the environment, including surface waters, undergo facile chlorination by hypochlorite when dissolved in humus-poor water to give a suite of chlorinated PAH (1660). It is therefore conceivable that this chlorination can occur under natural conditions, but this is yet to be determined. Another new possible source of natural chlorinated PAH is the reported in vitro reaction of benzo [a pyrene diol epoxide, the ultimate carcinogen of benzo aIpyrene with chloride ion to give chlorohydrin DDD, which has been isolated and identified as an intermediate en route to a benzol a pyrene-DN A adduct (1661). However, DDD is not considered to be a natural compound at this time. 

Magyarosy A, Ho JZ, Rapoport H, Dawson S, Hancock J, Keasling JD (2002) Chlorxantho-mycin, a Fluorescent, Chlorinated, Pentacyclic Pyrene from a Bacillus sp. Appl Environ Microbiol 68 4095... 

The sole representative of this class is l-(4,6-dimethoxy-l,3,5-triazin-2-yl)pyrene (67), [3271-22-5], which gives a bluish white brightening effect on polyester substrates it is employed chiefly in combination with other polyester brighteners such as 38. Compound 67 is obtained by the Fricdel-Crafts reaction of cyanuric chloride with pyrene with subsequent replacement of the remaining chlorines with methoxyl groups [117],... 

Technical Observations. Naphthalenetetraearboxylie aeid is obtained most easily — analogously to phthalic acid — by oxidation of the corresponding higher ring system, pyrene. Instead of first chlorinating the pyrene, it can be oxidized by dichromate and sulfuric acid to form pyrenequinone (mixture of the 3,8 and 3,10 quinones) and this can then be oxidized further to naphthalenetetraearboxylie acid by chloride of lime in the presence of lime, according to the reaction ... 

In a moisture-tight, three-necked flask provided with stirrer, thermometer, and reflux condenser, 101 grams (0.5 mole) of pyrene is dissolved at 130°C. in 1500 grams of dry trichlorobenzene (or dichlorobenzene). A stream of dry chlorine is introduced with vigorous stirring... 

At the end of the reaction the cuprous chloride is removed by filtration, and the carbon tetrachloride solution is chromatographed on alumina. The product is obtained as a lemon-yellow solid. By the same procedure pyrene affords 1-chloropyrene in 90% yield phenanthrene is not chlorinated. 

PAHs in water can be chemically oxidized by chlorination and ozonation. A high efficiency of PAH degradation from chlorination has been reported by Harrison et al. (1976a, 1976b) for both laboratory and waste-water treatment plant conditions. Pyrene was the most rapidly degraded PAH. Benz[a]anthracene, benzo[a]pyrene, and perylene were also highly degraded. 

In water, ozonation is generally slower and less efficient than chlorination in degrading PAHs (Neff 1979). Reaction pathways for ozonation of some PAHs include benz[a]anthracene to 7,12-quinone benzo[a]pyrene to 3,6-, 1,6-, and 4.5-diones and fluorene to fluorenone (NAS 1972). 

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