Mirex reactions

It is well established that important photochemical reactions are mediated by humic material in the aquatic environment (Zepp et al. 1981a,b), and that these are particularly signihcant for hydrophobic contaminants. Partial reductive dechlorination of the persistent insecticide mirex associated with... 

Source Hexachlorobenzene may enter the environment from incomplete combustion of chlorinated compounds including mirex, kepone, chlorobenzenes, pentachlorophenol, PVC, polychlorinated biphenyls, and chlorinated solvents (Ahling et al., 1978 Dellinger et al., 1991). In addition, hexachlorobenzene may enter the environment as a reaction by-product in the production of carbon tetrachloride, dichloroethylene, hexachlorobutadiene, trichloroethylene, tetrachloro-ethylene, pentachloronitrobenzene, and vinyl chloride monomer (quoted, Verschueren, 1983). 

The reaction was found to be quantitative and 8 of the more common OC pesticides were found to disappear on reaction or give derivatives with GC retention different than Mirex. 

Dechlorination is a commonly occurring photochemical reaction. Organochlorine insecticides such as BHC isomers, dieldrin, heptachlor, mirex, and chlordane isomers are photo-degraded via dechlorination (Figure 11.5). 

In addition to the chloroacetates, as shown by comparisons with the estimates in Table V, the half-lives for both lindane and mirex in the natural water samples would have been considerably longer than those observed, had reaction with solvated electrons in bulk solution been the dominant mechanism for photoreaction. The higher efficiency of these halocarbon reactions may be attributable to sorption of the chloroacetates on the NOM, which permits more facile electron capture. Other possible pathways for reactions of sorbed halocarbons include direct photoreduction by excited states of the NOM, which, like solvated electrons, also are quenched by oxygen. Alternatively, the enhancement may involve other direct electron-transfer mechanisms such as amine-halomethane reactions. These alternative possibilities are examined in the following section. 

Likewise, reduction of mirex in an iron(II)porphyrin model system occurs to give mono-, di-, tri, and tetrahydro derivatives as well as other more polar reaction products (Holmstead, 1976). 

Because the life cycles of insects are short, they can evolve an immunity to insecticides within a short period. As early as 1948, several strains of DDT-resisfant insects were identified. Today, fhe malaria-bearing mosquitoes are almosf completely resistant to DDT, an ironic development. Other chlorocarbon insecticides were developed to use as alternatives to DDT against resistant insects. Examples of fhese chlorocarbon materials include Dieldrin, Aldrin, Chlordane, and the substances whose structures are shown here. Heptachlor and Mirex are prepared using Diels-Alder reactions. 

The facile dechlorination of the comer chlorines of the pesticide Mirex, 2, is of particular interest. These chlorines cannot be removed by nucleophilic substitution because nucleophiles cannot get inside the cage to approach carbon from the backside in Sn2 reactions. Elimination reactions are also in ossible since double bonds from these comer carbons can t be formed due to the constrained geometry. However, solvated electron solutions readily and conq>letely dechlorinate Mirex. ... 

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