Organophosphorus ester insecticides

Ecobichon DJ Organophosphorus ester insecticides, in Pesticides and Neurological Diseases. Edited by Ecobichon DJ, Joy RM. Boca Raton, FL, CRC Press, 1982, pp 151-203... 

Used industrially for the manufacture of organophosphorus compounds (Insecticides, dyes, pharmaceuticals, defoliants) as well as esters for plasticizers, gasoline additives, and hydraulic fluids used in industry as a chlorinating agent, catalyst, dopant for semiconductor grade silicon, fire retarding agent, and solvent in cryoscopy. 

The objective of this work Is to establish a reaction mechanism between sodium perborate and several organophosphorus esters. By analogy we can then describe Its probable effects upon other phosphorus-based Insecticides. We conclude that the reactivity of sodium perborate toward five model compounds Is attributable to the nucleophilic reactions of hydroperoxyl anion, HO2 , produced by perborate dissociation In water. On this basis we predict that sodium perborate solutions will be effective chemical detoxicants for phosphorus ester Insecticides. 

Insect resistance and environmental pollution due to the repeated application of persistent synthetic chemical insecticides have led to an Increased interest in the discovery of new chemicals with which to control Insect pests. Synthetic insecticides, including chlorinated hydrocarbons, organophosphorus esters, carbamates, and synthetic pyrethroids, will continue to contribute greatly to the increases in the world food production realized over the past few decades. The dollar benefit of these chemicals has been estimated at about 4 per 1 cost (JJ. Nevertheless, the repeated and continuous annual use in the United States of almost 400 million pounds of these chemicals, predominantly in the mass agricultural insecticide market (2), has become problematic. Many key species of insect pests have become resistant to these chemicals, while a number of secondary species now thrive due to the decimation of their natural enemies by these nonspecific neurotoxic insecticides. Additionally, these compounds sometimes persist in the environment as toxic residues, well beyond the time of their Intended use. New chemicals are therefore needed which are not only effective pest... 

Historically, organophosphorus esters have played an extremely important part in insect control, and despite modern developments are still used on a wide scale. In contrast to the organochlorine insecticides, they degrade readily in the environment. 

Table III. Inhibition (as IC50) of Specific [3H]Pr-BP Binding to Housefly Head Membranes by Organophosphorus Esters and Related Compounds and their Insecticidal Activity (as LD50)...

Introduction. Nerve agents are primarily organophosphorus esters similar to insecticides. Although some have been given names, they are usually known by their code letters GA (TABUN), GB (SARIN), GD (SOMAN), and VX. 

The organophosphorus esters represent another class of environmental chemicals that are hydrolyzed by nucleophilic substitution reactions. These chemicals comprise one of the most important classes of agrochemicals with insecticidal activity (Fest and Schmidt, 1983). The organophosphorus esters also have important industrial uses such as oil additives, flame retardants, and plasticizers (Muir, 1988). The wide range of biological activity that this class of chemicals exhibits is due to the variety of substituents that can be attached to the central phosphorus atom. 

The organophosphorus esters that have the greatest environmental significance because of their extensive use as insecticides have the general structure ... 

Organophosphate Ester Hydraulic Fluids. A number of studies have been conducted on organophosphate ester hydraulic fluids because of the well known neurotoxic effects caused by organophosphorus insecticides, organophosphorus nerve gases, and tri-ort/w-cresyl phosphate (TOCP). The following manifestations of acute exposure to organophosphorus compounds have been described ... 

In non-saline sediments aliphatic and polyaromatic hydrocarbons, phthalate esters carboxylic acids, uronic acid aldoses chloroaliphatics haloaromatics chlorophenols chloroanisoles polychlorobiphenyls polychlorodibenzo-p-dioxins poychlorodibenzofurans various organosulphur compounds, chlorinated insecticides, organophosphorus insecticides mixtures of organic compounds triazine herbicides arsenic and organic compounds of mercury and tin. 

As discussed in Section 2.5.1, the detection of certain thiophosphate esters in human urine may indicate exposure to disulfoton and/or other organophosphate insecticides. Several methods are available for the quantitation of organophosphorus metabolites from urine (Bradway et al. 1981 Daughton et al. 1976 Lores and Bradway 1977 Shafik et al. 1973). 

Studies were initiated at Iowa State University in 1977 to determine if pesticides would be contained and degraded when deposited in water/soil systems. Although the addition of known amounts of the selected pesticides was controlled, the physical environment was not temperature, humidity, wind speed, etc. were normal for the climate of Central Iowa. Four herbicides and two insecticides were chosen on the basis of three factors. Firstly, they represented six different families of pesticides. The four herbicides, alachlor, atrazine, trifluralin, and 2,4-D ester, represent the acetanilides, triazines, dinitroanilines, and phenoxy acid herbicides, respectively. The two insecticides, carbaryl and para-thion, represent the carbamate and organophosphorus insecticides, respectively. Secondly, the pesticides were chosen on the basis of current and projected use in Iowa Q) and the Midwest. Thirdly, the chosen pesticides were ones for which analytical methodology was available. 

Oxygen heterocycles are less common amongst organophosphorus insecticides but two examples are dioxathion (79) (59JA139) and salithion (80) (62ABC452). The latter is the only phosphorus heterocycle that has achieved commercial use. The generally poor insecticidal activity of cyclic phosphorus esters has been ascribed to instability and steric effects (B-74MI10702). 

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