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United States Department of Agriculture

Agricultural Research Service


item Lin, Chung-ho
item Lerch, Robert - Bob
item Leigh, N
item Garrett, H
item George, M

Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 8/9/2005
Publication Date: 9/27/2005
Citation: Lin, C., Lerch, R.N., Leigh, N.D., Garrett, H.E., George, M.F. 2005. Degradation pathway of isoxaflutole (balance tm)in chlorinated tap water. ASA-CSSA-SSSA Annual Meeting Abstracts.

Interpretive Summary:

Technical Abstract: Isoxaflutole (IXF; Balance TM) belongs to a new class of isoxazole herbicides. Isoxaflutole has a very short half-life in soil and rapidly degrades to a stable and phytotoxic metabolite, diketonitrile (DKN). Further degradation of DKN produces a nonbiologically active benzoic acid (BA) metabolite. DKN was previously discovered to rapidly react with hypochlorite (OCl-) in tap water, yielding the benzoic acid metabolite as the major end product. Stoichiometry of the reaction suggests a molar ratio of OCl-/DKN near 3 (2.95 ± 0.36). During the analyses for elucidation of the degradation pathway, another stable chlorinated byproduct was identified when OCl- was depleted. This chlorinated compound was isolated and further characterized by its ion fragmentation patterns and isotope profiling. The proposed chemical structure was consistent with the structure predicted by mass spectrometry simulation software. Based on the stoichiometry of the reaction and structure of the reaction products, a two-step reaction via nucleophilic attack of the keto carbons by OCl- reaction mechanism was proposed. Due to the high stability and mobility (hydrophobicity between DKN and BA) of the chlorinated byproduct identified from this work, it has potential to be an environmental contaminant in agronomic settings if chlorinated tap water is used to prepare solutions for field spraying.

Last Modified: 06/24/2017
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