Organochlorine pesticides structure

Chetty CS, Aldous CN, Desaiah D. 1983a. Sensitivity of rat brain ATPase system to structurally related organochlorine pesticides. Indian Journal of Comparative Animal Physiology 1(1) 107-113. 

Organochlorine pesticides involve organic molecules that contain several halogenated atoms, and OPPs involve esters of phosphoric, phosphonic, phosphorothioic, or related acids (20,21). Figure 1 shows the chemical structures and names of some OCPs and OPPs. 

With the restriction of most organochlorine pesticides within the developed world between 1970 and 1980, the major release of the compounds in Table 1 now relates to use in developing countries, especially Asia, South/Central America, China and Africa, although statistics on their use in many areas remain unclear.8 The following briefly reviews the major types of persistent organochlorine pesticides found in the wider environment. The structures of a selection of these are illustrated in Figure 1. 

Some difficulties were encountered in the absolute confirmation of configurational and structural isomers where mass spectral peak intensities and mass values of characteristic fragment ions were too similar under the conditions of the analysis. In those instances, however, identification was readily made on the basis of gas chromatographic retention time data. The estimated lower limit of detectability of organochlorine pesticide residues by this analytical scheme and instrument configuration was determined to be approximately 0.05 to 0.1 ppm. 

Similar to other organochlorine pesticides in this structural class, chlorobenzilate causes disruption of normal flow of Na" " and across axonal membranes in the central (CNS) and peripheral nervous systems, and may also antagonize GABA-mediated inhibition in CNS. The net result is a hyperexcitable state of neurotransmission. 

In addition to those listed above, many other classes of compounds are also used in several pesticide formulations dithiocar-bamates, chlorophenols, nitrophenols, and various phthalimides. While the former three classes of substances—organochlorine pesticides, organophosphates, and carbamates— are among the best known pesticides (e.g., insecticides, rodenticides), triazines, chlorophenoxy acids, and bipyridyls are used in making herbicides. There are also many pesticides that do not fall under any specific class of structures. These are discussed separately. 

The general term organochlorine pesticides refers to many halogenated organic componnds that are being used cnrrently or that were nsed in the past in pesticide formn-lations. Snch substances may differ widely in their chemical structures and, therefore, in their physical and toxicological properties. Some of the most well-known pesticides of this class, many of which listed as U.S. EPA priority enviromnental pollutants, may be structurally classified into the following five types ... 

TABLE 46.1 Comparison of Chemical Structures of Some Organochlorine Pesticides to Their LD50/LC50 Values... 

Organochlorine pesticides = A unique class of pesticides because of their cyclic structure, number of chlorine atoms, and low volatility. They can be classified into four categories dichlorophenyl-ethanes (e.g., DDT), cyclodienes, chlorinated benzenes (e.g., hexachlorobenzene (HCB)), and cyclohexanes (e.g., hexachlorocyclohexane (HCH)). 

Figure 2.1 The chemical structures of some chiral pollutants, (a) Aliphatic organochlorine pesticides (b) aromatic organochlorine pesticides (c) phosphorous pesticides.

Strength as an oxidizing agent. There is, however, pressure to reduce the use of chlorine gas and organochlorine compounds, because they can lead to the environmental release of chlorinated hydrocarbons, which may cause cancer and other kinds of adverse health effects. The danger compounds include the notorious dioxin (Structure 6.2), which is a degradation product of organochlorine pesticides and other similar compounds. 

GC is coupled with many detectors for the analysis of pesticides in wastewater. At the present time the most popular is GC-MS, which will be discussed in more detail later in this section. The flame ionization detector (FID) is another nonselective detector that identifies compounds containing carbon but does not give specific information on chemical structure (but is often used for quantification because of the linear response and sensitivity). Other detectors are specific and only detect certain species or groups of pesticides. They include electron capture,nitrogen-phosphorus, thermionic specific, and flame photometric detectors. The electron capture detector (ECD) is very sensitive to chlorinated organic pesticides, such as the organochlorine compounds (OCs, DDT, dieldrin, etc.). It has a long history of use in many environmental methods,... 

Several hundred-pesticide compounds of diverse chemical structures are widely used in the United States and Europe for agricultural and non-agricultural purposes (Fig. 10). Some are substitutes for organochlorines, which were banned due to their toxicity, persistence, and bioaccumulation in environmental matrices. According to a report published by the US-EPA, a total of 500,000 tons of pesticides was used in 1985 [144, 145, 148]. As far as specific pesticides are concerned, worldwide consumption of Malathion and Atrazine in 1980 amounted to 24,000 and 90,000 tons, respectively [149,150]. In the Mediterranean countries, 2100 tons of Malathion (active ingredient) were sprayed during the same period compared to 9700 tons in Asia [150]. 

A number of pesticides are used in vast amounts in agriculture and horticulture each year. As a result, waters, soils, and plants are frequently contaminated with these substances, which therefore constitute one of the major sources of potential environmental hazards to man and animals through their presence and concentration in the food chain. Pesticides are classified according to their chemical structure into organochlorines, organophosphates, carbamates, triazine herbicides,... 

Several hundred-pesticide compounds of diverse chemical structures are widely used in the United States and Europe for agricultural and non-agricultural purposes, generating large amounts of solid waste materials. Some are substitutes for organochlorines, which were banned due to their toxicity, persistence, and bioaccumulation in environmental matrices. Chemical structures of various pesticides are shown in Fig. 3. 

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