Herbicides bipyridyl

Another factor that can influence the environmental distribution of a chemical is the presence of charged groups. Some pollutants, such as the sodium or potassium salts of phenoxyalkanoic herbicides, dinitrophenols, and tetra- or penta-chlo-rophenol, exist as anions in solution. Others, such as the bipyridyl herbicides diquat and paraquat, are present as cations. In either case, the ions may become bound to organic macromolecules or minerals of soils or sediments that bear the opposite... 

Chlorophenoxy herbicides 2,4-D 2,4,5-T Bipyridyl herbicides Paraquat, diquat... 

Glyphosate is a significant eye and skin irritant. It has caused lethal outcomes, although it is far less potent than the bipyridyl herbicides. Although the pure chemical seems to have little persistence and lower toxicity than other herbicides, the commercial formulations of glyphosate often contain surfactants and other active compounds that complicate the toxicity of the product. No specific treatment is available for glyphosate toxicity. 

The bipyridyl herbicide Paraquat is made by reduction of pyridine to radical ions, which couple at the para positions. Oxidation and reaction with methyl bromide gives paraquat. Diquat is formed by dehydrogenation of pyridine and quaternization with ethylene dibromide. 

Bipyridyl herbicides include alachlor, amitrole, atrazine, bromacil, bromoxynil, butylate, cyanazine, dalapon, dicamba, diuron, linuron, fluometuron, hexazinone, molinate, metolachlor, oryzalin, pendimethalin pronamide, propanil, propazine, simazine, terbacil, triallate, and triclopyr. In addition to these herbicides, the most common bipyridyls are diquat and paraquat. Paraquat is more toxic than diquat and produces chronic abnormal cell growth in the lungs, cornea and lens of the eye, nasal mucosa, skin, and fingernails. Diquat affects the eye lens and intestinal tract lining, but does not usually produce the frequently fatal lung changes characteristic of paraquat. 

Sandy, M.S., Moldeus, P., Ross, D. and Smith, M.T. (1986). Role of redox cycling and lipid peroxidation in bipyridyl herbicide cytotoxicity. Studies with a compromised isolated hepatocytc model system. Biochem. Pharmacol. 35, 3095-3101. 

The interaction of bipyridyl herbicides (paraquat and diquat) with photosynthesis is different from that of the electron transport inhibitors. These compounds, with highly negative redox potentials (paraquat E 446mV diquat Eq -349mV), interact in the vicinity of ferredoxin causing a diversion of electron flow from the ultimate electron acceptor NADP. This was clearly seen in paraquat-treated plant material as a progressive inhibition of carbon dioxide uptake (25)... 

Bipyridyl herbicides, such as paraquat or diquat dibromide — These compounds, relatively very few with practical application, have bipyridyl structure containing two quaternary N atoms. 

Since the 1930s almost all the pesticides which have been developed are organic compounds, with notable examples being DDT, the chlorinated phenoxyacetic acid and bipyridyl herbicides, and glyphosate. 

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