Dipyridyl herbicides

Fatty Acids. Of the total fatty acids produced annually in the United States, amounting to more than 450,000 tons, 35 percent come from tall oil. The solvent extraction of pine wood yields only 1 percent fatty acids and their esters. The yield is not increased, however, by paraquat (dipyridyl herbicides) treatment. Hence, the kraft-pulping industry will continue to be the major source of fatty acids from wood. The approximate distribution of uses of the fatty acids are ... 

Paraquat and diquat are dipyridyl herbicides used for weed control and as preharvest (desiccant) defoliants. Paraquat has been used for large-scale control of illegal marijuana growing. Dipyridyl product fonnulations differ by country. In the United States, paraquat has been available as a concentrated (29-44%) liquid. Diquat is found in aqueous concentrates containing 8-37.3% of the herbicide. Granular fonnulations containing a 2.5% mixture of paraquat and diquat salts are also available. 

A. Paraquat and diquat are strong cations in aqueous solution, and concentrated solutions (eg, >20%) may cause severe corrosive injury when ingested, injected, or applied to the skin, eyes, or mucous membranes. The dipyridyl herbicides are extremely potent systemic toxins when absorbed and can... 

The dipyridyl herbicides are available in concentrated forms (5%-20% solutioiis) for agricultiiral use and dilute forms for home lawns and gardens. 

The dipyridyl herbicides are frequently implicated in cases of malicious poisoning of dogs. 

Mechanism of toxicolo action. The dipyridyl herbicides are reduced by reduced... 

The classical route for producing 2,2 -dipyridyl consists in the dehydrodimerization of pyridine on Raney-Ni using a process developed by the Imperial Chemical Industries [63AHC(2)179 68CI(L)49, 80MI4]. 2,2 -Bipyridyl reacts with ethylene bromide to give l,l -ethylene-2,2 -bipyridylium bromide (diquat). The production of one ton of the diquat (which is widely used as a herbicide) requires 1.2 tons of pyridine [Eq.(17)]. 

The dipyridyl-based contact herbicides (Diquat, Paraquat) exhibit antifertility effects on spermatocytes and cause fetal malformations. In addition these compounds are severely damaging to lungs, kidneys, liver, heart and/or QI tract, and can be permanently disabling when not lethal. 

In all the reported agrochemical applications a sulfur heterocycle is used. The 2,2-dioxo-pyrazolo[3,4-c][l,2,5]thiadiazines <90MI 713-01) and the 5,6-dipyridyl[l,2,5]thiadiazolo[3,4-6]pyr-azine (183) <84BRP2122492> are fungicidal. The 2,2-dioxopyrazolo[3,4-c][l,2,6]thiadiazines are herbicides <80USP4182623). 

Increases in yield of naval stores are brought about by chemical treatment of the exposed wood, especially with paraquat herbicides (dipyridyl compounds). This treatment stimulates extensive oleoresin formation and diffusion into the wood, extending to the pith of the tree and several feet above the treatment level. As much as 40 percent oleoresin content in the wood has been produced. Such treatment could double naval stores production, for both gum and sulfate processes. It also has the potential of providing a new type of wood naval stores by solvent extraction prior to kraft pulping, or a combination of both methods. 

Dipyridyls are also nitrogenous herbicides. For example, paraquat is used as dichloride salt. Therefore, this compound is very soluble in water and poorly soluble in solvents. Figure 58 shows the UV spectrum of a paraquat solution. 

Anion Source for Palladium Catalysis. The reagent serves as a source of weakly coordinating anions in the palladium-catalyzed formation of mixed phenyl ureas, a known class of commercially available herbicides, using palladium(II) acetate, copper(II) toluenesulfonate, and 2,2 -dipyridyl as the catalyst system. Other studies have suggested that use of this reagent to form palladium salts may have useful applications in the reductive carbonylation of nitroaromatic compounds to give isocyanates via initial carbamate formation (eq 2). ... 

Stnictue. The dipyridyl structure is uraque among the herbicides (see lafale 20-1). 

The dual application of ALA with one or more chlorophyll biosynthesis modulators can result in selective herbicide action due to the four different greening patterns within the multibranched chlorophyll pathway that occur in plants. " The chlorophyll biosynthesis modulators are classified into three major groups depending on their mode of action enhancers of ALA conversion to tetrapyrroles (e.g., 2-pyridine aldehyde, picolinic acid, 4,4 -dipyridyl, phenanthridine, 2,2 -pyridylamine) inducers of tetrapyrrole accumulation (e.g., 1,10-phenanthroline, 2,2 -dipyridyl) and inhibitors of mono vinyl protochlorophyllide accumulation (1,7- and 4,7-phenanthroline, 2,3-dipyridyl, 2,4-dipyridyl). ... 

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