Pesticides pyridine derivatives

Organophosphorus Derivatives. Neopentyl glycol treated with pyridine and phosphorus trichloride in anhydrous dioxane yields the cycHc hydrogen phosphite, 5,5-dimethyl-l,3-dioxaphosphorinane 2-oxide (2) (32,33). Compounds of this type maybe useful as flameproofing plasticizers, stabilizers, synthetic lubricants, oil additives, pesticides, or intermediates for the preparation of other organophosphoms compounds (see Flame retardants Phosphorus compounds). 

Pyridine and derivatives of pyridine occur widely in nature as components of alkaloids, vitamins, and coenzymes. These compounds are of continuing interest to theoretical physical, organic, and biochemistry and to industrial chemistry. Pyridine and derivatives have many uses, e.g., herbicides and pesticides, pharmaceuticals, feed supplements, solvents and reagents, and chemicals for the polymer and textile industries. 

Bowman and Beroza [472] hydrolysed carbamates by heating with 10% NaOH solution and condensed the phenol produced with chlorothiophosphate in the presence of pyridine (Scheme 5.37). The resulting derivative is highly specific for the compound under analysis and, with the use of a flame photometric detector, it permits its sensitive analysis (at the level of hundredths of 1 ppm in foodstuffs). A column packed with 10% of DC-200 was used for the analysis at 190°C. Holden et al. [473] also obtained a high sensitivity in the analysis of N-methyl- and dimethylcarbamates if they condensed amines released by alkaline hydrolysis with l-fluoro-2,4-dinitrobenzene and applied an ECD for detection (2% of XE-60, 190°C). Different substituted anilines were similarly analysed as products from the decomposition of different pesticides [474] in the form of different perfluorinated acyl derivatives. 

The Pesticide Manual describes 5 pyridine carboxylic acid derivatives, 3 benzoic acids, and 10 aryloxyalkanoic acids in current use as herbicides. 2,4,5-T seems to be banned worldwide and is not included in the current issue (Tomlin, 2000) but is described in earlier issues (e.g., Worthing, 1979). It was first registered in 1948 by Amchem Products, Inc., Pennsylvania, and the Dow Chemical Company, and was mainly used to control shrubs and trees, for example, in forests and along railways. Although the content of dioxin was eventually controlled, with a limit of <0.05 mg/kg in the preparation, it was banned soon after the termination of its use in Vietnam. Other products with 2,4,5-trichlorophenol were also banned or restricted after the Seveso accident (see Hay, 1978a, 1978b). 2,4-D is also produced from a chlo-rophenol and may contain dioxins, but of the much less toxic congeners. It... 

The Pesticide Manual describes 5 pyridine carboxylic acid derivatives, 3 benzoic acids, and 10 aryloxyalkanoic acids in current use as herbicides. 

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