Cyclodienes, polychlorinated

Cyclodienes. These are polychlorinated cycHc hydrocarbons with endomethylene-bridged stmctures, prepared by the Diels-Alder diene reaction. The development of these insecticides resulted from the discovery in 1945 of chlordane, the chlorinated adduct of hexachlorocyclopentadiene and cyclopentadiene (qv). The addition of two Cl atoms across the double bond of the ftve-membered ring forms the two isomers of chlordane [12789-03-6] or l,2,4,5,6,7,8,8-octachloro-2,3,3t ,4,7,7t -hexahydro-4,7-methano-lJT-indene, QL-trans (mp 106.5°C) and pt-tis (32) (mp 104.5°C). The p-isomerhas signiftcantiy greater insecticidal activity. Technical chlordane is an amber Hquid (bp 175°C/267 Pa, vp 1.3 mPa at 25°C) which is soluble in water to about 9 fig/L. It has rat LD qS of 335, 430 (oral) and 840, 690 (dermal) mg/kg. Technical chlordane contains about 60% of the isomers and 10—20% of heptachlor. It has been used extensively as a soil insecticide for termite control and as a household insecticide. 

The formation of polar metabolites from nonpolar materials may actually facilitate monitoring programs—in many cases the polar chemicals are highly concentrated in certain body fluids such as bile and urine. On the other hand, materials such as certain cyclodienes and polychlorinated biphenyls, which are very lipid soluble and resistant to metabolism, may accumulate and these chemicals may persist in the environment and may be transferred via the food chain to man. There is also interest in these biotransformation processes in lower organisms since the simplicity of these systems may lead to a better understanding of the phylogenetic development of xenobiotic metabolism. 

Vanadium(V) fluoride converts polyfluoroaromatics into fluorinated cyclohexadienes and cyclohexenes, and reacts with polyfluorinated and polychlorinated alkenes,113 115 alkadienes, cycloalkenes and cyclodienes to give addition products of two fluorine atoms across C = C bonds.116117... 

Photolysis of 2-bromo-4,4-dimethyl-2-cyclohexenone only affords reduction, even in a nucleophilic medium343,344. Apparently, this substrate is structurally not suitable to form a vinyl cation. Formation of vinyl radical-derived products is also the main process for all vinylic halides, if their irradiation is performed in an apolar medium. Such photochemical reductive dehalogenation and especially dechlorination reactions have been extensively studied in the past, not in the least because of their importance as abiotic transformation of persistent polychlorinated environmental pollutants. Examples are the cyclodiene insecticides aldrin and dieldrin, which contain a vicinal dichloroethene chromophore. In recent... 

Considerable research effort has been paid to the problems of the persistence of chemical means for the plant protection. Many of the studies have been aimed at the persistence of pesticides in the soil. Insecticides based on chlorinated hydrocarbons are particularly persistent, for instance DDT, BHC isomers and so-called polychlorinated cyclodiene compounds, aldrin, dieldrin, andrin, heptachlor. In many countries the use of these pesticides has been either restricted or even prohibited on account of their persistence in the environment. For chemical protection of plants they are gradually being replaced by organophosphate and carbamate substances, which are more toxic, but are less stable in the environment (e.g. parathion, dichlor-vos, carbaryl, propoxur). 

Mansour, M. and H. Parlar. 1978. Gas chromatographic determination of several cyclodiene insecticides in the presence of polychlorinated biphenyls by photoisomerization reaction. J. Agric. Food Chem. 26, 483-485. 

The polychlorinated cyclodienes Aldrin 400) and Heptachlor 402) are converted in vitro by rabbit liver microsomes to their corresponding epoxides (Figure 12). The epoxidase has the characteristics of the mixed-function oxidase system in that it requires both NADPH and oxygen and it is inhibited by SKF 525-A. Dieldrin 401) is detoxified in vivo in the rat through hydrolysis of the epoxy group to a rarzi -dihydrodiol, which subsequently is oxidized to the dicarboxylic acid other metabolites include 9-hydroxydieldrin and a pentachloroketone structure. 

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