Cyclodiene

The first resins to be produced on a commercial scale were the coumarone—indene or coal-tar resins (1) production in the United States was started before 1920. These resins were dominant until the development of petroleum resins, which were estabHshed as important raw materials by the mid-1940s. Continued development of petroleum-based resins has led to a wide variety of aHphatic, cyclodiene, and aromatic hydrocarbon-based resins. The principal components of petroleum resins are based on piperylenes, dicyclopentadiene (DCPD), styrene, indene, and their respective alkylated derivatives. 

In order to increase the solubiUty parameter of CPD-based resins, vinyl aromatic compounds, as well as other polar monomers, have been copolymerized with CPD. Indene and styrene are two common aromatic streams used to modify cyclodiene-based resins. They may be used as pure monomers or contained in aromatic steam cracked petroleum fractions. Addition of indene at the expense of DCPD in a thermal polymerization has been found to lower the yield and softening point of the resin (55). CompatibiUty of a resin with ethylene—vinyl acetate (EVA) copolymers, which are used in hot melt adhesive appHcations, may be improved by the copolymerization of aromatic monomers with CPD. As with other thermally polymerized CPD-based resins, aromatic modified thermal resins may be hydrogenated. 

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. 

Mode of Motion. The cyclodienes, like lindane and toxaphene, affect the nerve axon produciag hyperactivity, convulsions, prostration, and death. The biochemical lesion is the competitive inhibition of the y-aminobutyric acid (GABA) neurotransmitter binding site of the nerve axon. Spray workers with lengthy exposure to dieldrin have suffered from prolonged and repeated central nervous system disturbances produciag epileptiform coavulsioas. Similar disturbances occurred ia workers heavily exposed to chlordecoae. 

Lindane is one of eight different hexachlorocyclohexane (HCH), C H Cl, isomers and its Chemical Abstract n.2cniQ is la, 2a 3P, 4a, 5a 6P-hexachlorocyclohexane [58-89-9] (y-HCH or y-BHC, ben2ene hexachloride) (80). Commercial products containing lindane are marketed as either a mixture of isomers or as the pure y-BHC isomer. Not unexpectedly, lindane is a highly stable lipophilic compound and it has been used extensively worldwide as an insecticide. In contrast, hexachloropentadiene, C Cl, is an extremely reactive industrial intermediate used as a chemical intermediate in the synthesis of a broad range of cyclodiene-derived pesticides, which include endosulfan, endrin, heptachlor, and several different organohalogen flame retardants (81). 

The detrimental effect of organochlorine pesticides on reproductive success in birds of prey is well established following the crash of some populations during the 1950s and 1960s. Links have been established with the DDT metabolite, DDE, the cyclodiene pesticides and Although many raptor species... 

Although eggshell thinning attributable to DDE exposure has occurred in birds in the UK, the lethal and siiblethal effects of the cyclodiene pesticides aldrin, dieldrin and heptachlor are also believed to have contributed to the population effects, particularly in the case of the sparrowhawk and peregrine falcon. Following the withdrawal of DDT and the cyclodienes from use in the UK, Europe and North America, bird of prey populations that were severely affected have shown partial or complete recovery. ... 

Balasubramaniam E, Paul V, Jayakumar AR, et al. 1996. The effect of chronic cyclodiene insecticide treatment on some pharmacological actions of diazepam in rats. Environ Toxicol and Pharm(2) 141-146. 

Flodstrom S, Warngard L, Hemming H, et al. 1988. Tumor promotion related effects by the cyclodiene insecticide endosulfan studied in vitro and in vivo. Pharmacol Toxicol 62 230-235. 

Gant DB, Eldefrawi ME, Eldefrawi AT. 1987. Cyclodiene insecticides inhibit GABA receptor-regulated chloride transport. Toxicol Appl Pharmacol 88 313-321. 

Pomes A, Rodriguez-Farre E, Sunol C. 1994. Disruption of GABA-dependent chloride flux by cyclodienes and hexachlorocyclohexanes in primary cultures of cortical neurons. J Pharmacol Exp Ther 271(3) 1616-1623. 

Rosa R, Rodriguez-Farre E, Sanfeliu C. 1996. Cytotoxicity of hexachlorocyclohexane isomers and cyclodienes in primary cultures of cerebellar granule cells. J Pharmacol Exp Ther 278(1) 163-169. 

Tumer KO, Syvanen M, Meizel S. 1997. The human acrosome reaction is highly sensitive to inhibition by cyclodiene insecticides. J Androl 18(6) 571-575. 

Cyclodienes H. virescens Field strains Altered GABA ... 

The organochlorine insecticides (henceforward OCs) can be divided into three main gronps, each of which will be discnssed separately in the sections that follow. These are (1) DDT and related componnds, (2) the cyclodiene insecticides, and (3) isomers of hexachlorocyclohexane (HCH Brooks 1974 Fignre 5.1). 

The cyclodiene insecticides aldrin, dieldrin, endrin, heptachlor, endosulfan, and others were introduced in the early 1950s. They were used to control a variety of pests, parasites, and, in developing countries, certain vectors of disease such as the tsetse fly. However, some of them (e.g., dieldrin) combined high toxicity to vertebrates with marked persistence and were soon found to have serious side effects in the field, notably in Western European countries where they were extensively used. During the 1960s, severe restrictions were placed on cyclodienes so that few uses remained by the 1980s. 

Apart from the oxidations just mentioned, cyclodienes are rather stable chemically. It should, however, be noted that dieldrin can undergo photochemical rearrangement under the influence of sunlight to the persistent and toxic molecule photo dieldrin, which occurs as a residue following the application of this insecticide in the field. 

In terrestrial animals, cyclodienes such as dieldrin, like other refractive lipophilic pollutants, can be excreted in their unchanged forms, notably with lipoproteins, which are exported into milk (mammals), eggs (birds, reptiles, insects), or developing... 

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