Insecticide hexachlorocyclohexane

An early chlorinated phenoxy acid herbicide (2,4-D) was first discovered in 1932. Although this compound rapidly breaks down in the environment, the seed fungicide hexachlorobenzene (HCB), introduced in 1933, was found to be far more persistent.2 The structurally similar insecticide hexachlorocyclohexane or... 

Eliminations of hydracide or halogen sometimes occur during the metabolism of halogenated xenobiotics and lead to an alkene. The double bond may be oxidized into an epoxide by means of oxidative enzyme systems as discussed above. Dehydrogenation, dehydrochloration and dechlora-tion are (with oxidation) the different metabolic pathways of the y-isomer of the insecticide hexachlorocyclohexane (lindane). 

Example 7 Analysis of the insecticide hexachlorocyclohexane, molecular weight of 291 g/mole, shows 24.7% carbon, 2,06% hydrogen, and 73.2% chlorine by mass. Using 12.0, 1.0, and 35,5 as the atomic weights, respectiveiy, of these eiements, caiculate the moiecular formula of the hexachiorocyclohexane. 

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). 

There are several isomers of 1,2,3,4,5,6-hexachlorocyclohexane (HCH). The Y isomer is insecticidally active, whereas most of the others are relatively inactive. These compounds have been shown to activate inflammatory functions of neutrophils (35,36). Using Indo-1, we have characterized intracellular Ca mobilization in response to these compounds. Figure 9 shows the responses of cells labeled with Indo-1 to stimulation by y, < " P , and 6-HCH at a concentration of 260 pH. 

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). 

Particularly the chlorinated compounds have enjoyed range of applications vinyl chloride (chloro-ethene) as monomer for the production of PVC, tetra- and trichloroethenes as solvents for degreasing, and the insecticides l,l,l-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) and isomers of hexachlorocyclohexane (HCH) (benzene hexachloride). The biodegradation of fluorinated aliphatic compounds is generally different from the outlines that have emerged from investigations on their chlorinated, brominated, and even iodinated analogues. They are therefore treated separately in Part 4 of this chapter. 

The importance of methods of analysis for new insecticides is evidenced by the fact that during the past two years industry and government have cooperated in developing methods for two of them—tetraethyl pyrophosphate and benzene hexachloride (1,2,3,4,5,6-hexachlorocyclohexane) (37, 45). 

Accessibility of the deposit to the insects by contact is the chief feature of the small vial method, but fumigant action cannot be eliminated entirely. In the case of DDT this has been found to be unimportant, for flies kept in the vials out of contact with the surface are not affected. But with 7-hexachlorocyclohexane or parathion there is a noticeable toxic effect. If the vials are stood upright, laid on the side, or hung upside down, there is a decrease in the mortality produced in the order given. The position on the side has been adopted because it avoids extremes and because practical use of an insecticide often involves limited but not accentuated ventilation. 

Field test work with technically pure gamma isomer of hexachlorocyclohexane has been extensive and involved and is being continued. It was necessary to know such factors as insecticidal value in field applications as compared to other insecticides, as well as residual life, residue from the poison standpoint, and residual taste or odor factors. These factors have been worked out on numerous crops and some of the results are dealt wTith in this paper. Because the pure gamma isomer was found to be effective on insects in the soil as well as on insect infestations on plants, its residual life in soil of all types and effects on tuber and root crops were also of major importance. 

The use of pure gamma isomer of hexachlorocyclohexane on livestock has also been worked out. It has been found possible to use the wettable powder formulation dispersed in water as a spray on livestock for control of flies, lice, and ticks. Proper dosage and application must be used, of course, but this is again indicative of the safety factor of this insecticide. 

For some important insect pests there are still no satisfactory chemical controls. Such problems should be given due consideration in the development program. Many of these problems appeared to be solved with the discovery of DDT, benzene hexachlo-ride (hexachlorocyclohexane), and some of the more recent insecticides. Further studies of the toxicity of some of these products to warm-blooded animals have raised the important question of the advisability of continuing their use where food and feed products are concerned. Considerable attention is being centered on finding safer analogs, such as TDE and methoxychlor, and new and better insecticides. 

When the individual insecticides are present in the solution in such a concentration range, the electron capture responds nearly uniformly to all insecticides. A column filled with 1.5% silicone OV-17 plus silicone oil (fluoralchylsiloxane) on Chromasorb W (80-100 mesh) is used for separation of the BHC alpha, beta, gamma and delta isomers (hexachlorocyclohexane), o,p -DDT, p,p -DDE, p,p -DDD, and p,p -DDT. a-BHC and hexachlorobenzene (HCB) have a common peak. They can be separated on a column filled with 2.5% Silicone Oil XE-60 (Is-cyanoethyl-methylsilicone) on Chromosorb W (80-100 mesh). 

Abalis IM, Eldefrawi ME, Eldefrawi AT. 1985. High-affinity stereospecific binding of cyclodiene insecticides and y-hexachlorocyclohexane to y-aminobutyric acid receptors of rat brain. Pestic Biochem Physiol 24 95-102. 

Chlorination of benzene gives an addition product that is a mixture of stereoisomers known collectively as hexachlorocyclohexane (HCH). At one time, this was incorrectly termed benzene hexachloride. The mixtnre has insecticidal activity, though activity was found to reside in only one isomer, the so-called gamma isomer, y-HCH. y-HCH, sometimes under its generic name lindane, has been a mainstay insecticide for many years, and is about the only example of the chlorinated hydrocarbons that has not been banned and is still available for general use. Although chlorinated hydrocarbons have proved very effective insecticides, they are not readily degraded in the environment, they accumulate and persist in animal tissues, and have proved toxic to many bird and animal species. 

Perhaps the best-known photoaddition reaction of benzene is that with chlorine to produce hexachlorocyclohexane (3.37). of which one steroisomer is widely used as an active component in insecticides. However, this reaction does not involve the excited state of benzene chlorine absorbs light and cleaves homolytically to give chlorine atoms, which then attack the ground state of benzene, leading to overall addition. 

Of all the isomers of hexachlorocyclohexane, only the y-isomer (the only one that is strongly biologically active as an insecticide) is reduced in the normally accessible potential range (138). 

The most fundamental properties of a chemical substance are those of the substance in pure form, in most cases as a solid or liquid. Molecular mass can be deduced readily from the chemical formula or structure, although a range of values may exist for commercial mixtures. In some cases, the substance may adopt different structural (e.g., cis-trans) or enantiomeric forms, usually with relatively small physical property differences but with potentially substantial differences in ability to induce toxicity or other biological responses. The hexachlorocyclohexane isomers and enantiomers are examples, the insecticide lindane or y HCH being the most active form. 

As commonly used in commercial formulations this insecticide (termiticide) contains a number of isomers of which the active ingredient gammexane is the (la,2a,3P.4a,5a,6fS)-l,2,3,4,5,6-hexachlorocyclohexane ... 

Hexachlorocyclohexane, once confusingly called benzene hexachloride (BHC), consists of several stereoisomers with different orientations of H and Cl atoms. The gamma isomer is shown in Figure 16.5. It is an effective insecticide, constituting at least 99% of the commercial insecticide lindane. 

Slade, R.E. (1945) The y-isomer of hexachlorocyclohexane (Gammexane). An insecticide with outstanding properties. Chem. Ind. 40, 314-319. 

A group of highly chlorinated polycyclic insecticides, exemplified by heptachlor (143) and aldrin (144), is prepared from hexachlorocyclopentadiene and cyclopentadiene. The y-isomer (lindane, 145) of hexachlorocyclohexane (HCH) is the toxic component of HCH, first prepared by Michael Faraday. Toxaphene consists of a complex mixture of chlorinated camphenes, of which 146 represents a particularly toxic isomer. 

Lindane (1,2,3,4,5,6-hexachlorocyclohexane) is an insecticide registered for commercial and home use, and it is also used in some shampoos. Lindane is slightly soluble in water and volatilizes readily. Lindane is classified as B2-C (i.e., between the lower half of the B category of probable and the C category of possible carcinogen classifications). 

Under typical polar conditions, benzene and napthalene undergo halogen substitution and not addition. However, in the presence of uv light, benzene adds Cl2 to give 1,2,3,4,5,6-hexachlorocyclohexane, an insecticide. 

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