Organic synthetic herbicides

Types of herbicides. Representative chemical groupings of common herbicides tested for toxicity in cattle and sheep are presented in Table 20-1. Inorganic and organic synthetic herbicides are recognized. 

Organic synthetic herbicides are most commonly used in modern agriculture. 

Organic farming systems rely more on mechanical weed control and in certain crops on considerably more intensive soil tillage as the use of synthetic herbicides is prohibited. This can have negative effects on other key species of soil meso-fauna, i.e. a reduction of population of Collembola with organic cultivation (Krogh 1994). 

Synthetic, organic, selective herbicides first appeared in France in 1932 with the patenting of dinitro-o-cresol (DNOC) for the selective control of annual weeds in cereals. Dinitro-cresols and dinitro-phenols soon appeared, but these compounds had variable effectiveness and could kill animals as well as plants. 

Phytotoxins from nonpathogenic organisms also have potential as weed-control agents. Numerous phytotoxic compounds have been isolated and bioassayed for phytotoxic activity, and their chemical structures have been determined. Generally, these naturally occurring compounds have unique chemistries that differ from those of commercial synthetic herbicides. Some of these compounds—or others yet to be discovered—may be used directly as herbicides or provide templates for the development of new, efficacious weed control agents that are less persistent and more environmentally compatible than some compounds currently being used. 

Phosgene has been used extensively as an organic synthetic reagent to prepare isocyanates, carbamates, organic carbonates, and chloroformates used in the manufacture of polyurethane and polycarbonate resins, pesticides, herbicides, and dyes. Although not flammable, because phosgene is... 

Toxic Organic Materials. The term toxic organics iacludes synthetic organic compounds such as pesticides, herbicides, PCBs, and chlotinated hydrocarbons, usually produced by the manufacturers and formulators of these products. 

Uses Coolant and refrigerant herbicide and fumigant organic synthesis-methylating agent manufacturing of silicone polymers, pharmaceuticals, tetramethyl lead, synthetic rubber, methyl cellulose, agricultural chemicals and nonflammable films preparation of methylene chloride, carbon tetrachloride, chloroform low temperature solvent and extractant catalytic carrier for butyl rubber polymerization topical anesthetic fluid for thermometric and thermostatic equipment. 

Uses Disinfectant phenolic resins tricresyl phosphate ore flotation textile scouring agent organic intermediate manufacturing salicylaldehyde, coumarin, and herbicides surfactant synthetic food flavors para isomer only) food antioxidant dye, perfume, plastics, and resins manufacturing. 

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