2,4-Difluorobenzoic acid

Diflubenzuron breakdown by hydrolysis, soil degradation, or plant and animal metabolism initially yields 2,6-difluorobenzoic acid and 4-chlorophenylurea. Ultimately, the end products are... 

Figure 17.1 Generalized degradation pattern for diflubenzuron. Diflubenzuron (A) degrades initially to 2,6-difluorobenzoic acid (B) and 4-chlorophenylurea (C). 2,6-Difluorobenzoic acid (B) degrades to 2,6-difluorobenzamide (D) and 4-chlorophenylurea (C) degrades to 4-chloroaniline (E).

Intestinal absorption of diflubenzuron in laboratory rats, measured as the sum of urinary and biliary excretion, decreases with increasing dose from 50% at a single oral dose of 4 mg/kg BW to 4% at 900 mg/kg BW. Excretion is almost complete after 75 h at that time, up to 4% of the administered dose is recovered from skinned carcasses (Willems etal. 1980). About 80% of diflubenzuron metabolites excreted by rats seem to have the basic diflubenzuron structure intact. Three metabolites are largely excreted as conjugates in the bile. One metabolite, 2,6-difluorobenzoic acid, is excreted largely in urine. Its counterpart, 4-chlorophenylurea, was not present in urine or bile in appreciable quantity, nor was 4-chloroaniline detected (Willems et al. 1980). Lifetime feeding studies of 4-chloroaniline, a relatively common diflubenzuron metabolite, showed no compound-related effects in laboratory mice and rats (Gartrell 1981). 

The main degradation pathway of diflubenzuron in soils would lead to the formation also of 2,6-difluorobenzoic acid as a primary metabolite. 

Figure 6. Degradation curves of 2,6-difiuorobenzamide and 2,6-difluorobenzoic acid after incubation of clay hydrosoil with 3H-2,6-difluorobenzamide. Recovery in percentage of applied dose.

Animals. Elimination is partly as the unchanged parent compound in the feces, partly as hydroxylated metabolites (for c. 80%) and as 4-chlorophenylurea plus 2,6-difluorobenzoic acid (for c. 20%). The intestinal absorption is strongly related to the dosage administered—the higher the dosage, the more (relatively) is excreted unchanged in the feces. 

Soil. Strongly absorbed by soil/humic acid complex and is virtually immobile in soil. Rapidly degraded in soil, with a half-life of <7 days. The principal degradation products are 4-chlorophenylurea and 2,6-difluorobenzoic acid... 

Reactions catalyzed by transition-metal complexes allow the synthesis of a variety of esters ruthenium(II) promotes the addition of acids to alkynes,379 380 e.g. 2,6-difluorobenzoic acid (9) undergoes addition to but-l-en-3-yne to furnish the enol ester 10.380 Aryl bromides381 and aryl or vinyl triflates,382-384 but also aryl chlorides when their tricarbonylchromium(O) complexes are used,385 react with palladium382- 385 or cobalt complexes38 to form a C —M bond. Insertion of carbon monoxide into the carbon-metal bond followed by trapping with an alcohol or phenol leads to ester formation, e.g. triflate 11 gives ester 12.382... 

Diflubenzuron can be either hydrolyzed at the urea bridge or oxidized by ring hydrox-ylation followed by conjugation. Hydrolytic cleavage seems to be a major route for diflubenzuron metabolism in many insect species. Two-spotted spider mites showed <10% absorption in 96 h of topically applied diflubenzuron. Of the amount absorbed, about 27% was metabolized in 96 h to 4-chlorophenyl urea, 2,6-difluorobenzoic acid, 4-chloroformanilide, 2,6-difluorobenzamide, and other metabolites. Effects of diflubenzuron were synergized by profenofos in cotton leafworm fourth instar larvae, and they were antagonized by 20-hydroxyecdysone in beetle (Tenebrio molitor) pupae. More information is needed on interaction effects of diflubenzuron with other chemicals. 

The major degradation products of diflubenzuron in water are 4-chlorophenylurea and 2,6-difluorobenzoic acid these compounds are less toxic to aquatic organisms than the parent... 

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