Pyrithiobac-sodium

Pyrithiobac-sodium is a pre- and post-emergence herbicide to control broad-leaved weed and grasses The residue definition is for the parent, pyrithiobac-sodium, only. 

Pyrithiobac-sodium is extracted as the free acid, pyrithiobac, from crop and soil samples. 

For cottonseeds, pyrithiobac-sodium is extracted with acetone-water (4 1, v/v). After filtration, the acetone is removed by evaporation under reduced pressure. The residue is adjusted to pH 1 and extracted with ethyl acetate. The extract is cleaned up by liquid-liquid partitioning and methylated with diazomethane. The methyl ester of pyrithiobac is purified by silica gel column chromatography. Pyrithiobac-methyl is determined by gas chromatography (GC) with nitrogen-phosphorus detection (NPD). 

Pyrithiobac-sodium, analytical grade (KI Research Inst. Co. Ltd) Pyrithiobac-methyl, analytical grade (KI Research Inst. Co. Ltd)... 

Untreated control samples of cottonseed and soil were fortified with pyrithiobac-sodium. The fortification levels were 0.01-0.1 mg kg" for cottonseeds and 0.005-0.05 mg kg- for soil. The recoveries obtained were 95-110% from cottonseeds and 86-98% from soil. The routine limit of determination was 0.01 mgkg- for cottonseeds and 0.005 mg kg- for soil. 

The residue R, expressed in mg kg- pyrithiobac-sodium, is calculated using the following equation ... 

Wp, = amount of pyrithiobac-methyl for V, read from the calibration curve (ng) F = factor (1.023) for conversion from pyrithiobac-methyl (MW 340.8) to pyrithiobac-sodium (MW 348.7)... 

H. Matsushita, T. Oishi, Y. Asano, and K. Ishikawa, Residue analytical method of pyrithiobac-sodium in crops and soil, in Abstracts of the 17th Annual Meeting of the Pesticide Science Society of Japan, p. 149 (1992). 

S.K. Singles, R.F. Dietrich, and R.D. McFetridge, Degradation of pyrithiobac sodium in soil in the laboratory and field, in Pesticide Environmental Fate, Bridging the Gap Between Laboratory and Field Studies, ed. W. Phelps, K. Winton, and W.R. Effland, ACS Symposium Series No. 813, American Chemical Society, Washington, DC, Chapter 15, pp. 207-221 (2002). 

Pyridate heterocyclic nitrogen, pyridazine Pyrifenox oxime, pyridine Pyrimethanil heterocyclic nitrogen, pyrimidine Pyriproxifen phenyl-ether, pyridine Pyrithiobac-sodium heterocyclic nitrogen, pyrimidine... 

In a biotype of Amarantkus retrojlexus from Israel, resistance was caused by a change of Prol97 to Leu. This biotype exhibited cross-resistance to sulfonylureas, imidazolinones, triazolopyrimidines and to pyrithiobac-sodium in vwo and on the ALS enzyme level [60]. In mutations of Amarantkus rudis, Ser653 was found to be exchanged by Thr or Asn. These were only resistant to imidazolinones [61]. 

The sodium salt of 6-chloro-2-[(4,6-dimethoxypyrimidin-2-yl)thio]benzoic acid 13 (pyrithiobac-sodium) was selected as one of the best cotton herbicides [13]. 

Pyrithiobac-sodium is prepared by the condensation of 2-chloro-6-mercap-tobenzoic acid 16 and DMSP 6. Compound 16 was synthesized through two steps starting from 2,6-dichlorobenzonitrile 17. The industrial process of DMSP 6 synthetic scheme (Fig. 2.5.10) has been optimized [17, 18]. 

On the other hand, the ALS of Lactuca setriola possessing a mutation of proline at 171 to histidine has been shown to be resistant to the SU and to exhibit cross-resistance to the IM but not to the PC. The ALS of K. scoparia possessing a mutation of proline at position 171 to serine was inhibited by the PC herbicide, bispyribac-sodium (BS) as potently as the wild-type enzyme but expressed a cross-resistance to the PC herbicide, pyrithiobac-sodium (Fig. 4) (5). 

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