Urea herbicides diuron

Diuron was introduced by du Pont in 1954 (Fig. 3). It is one of a series of substituted urea herbicides. Diuron is applied preemergence to crops such as cotton, alfalfa, grapes, fruit and nut crops. Foliar activity is enhanced when a surfactant is added to the spray. 

Introduced in 1951 by du Pont in the USA monuron (CMU, 6) was the first urea herbicide. Diuron (DCMU, 7) was introduced by the same company in 1956. 

Herbicides Substituted urea herbicides Diuron, neburon, phenobenzuron and isoproturon Adsorption LiChrosorb SI 60 Water saturated with dichloromethane (the role of water being to block the most active silanol sites thereby... 

Schneider P, Goodrow MH, Gee SJ et al. A highly sensitive and rapid ELISA for the urea herbicides diuron, monuronand linuron. J Agric Food Chem 1994 42 413-422. 

HAs have been issued for bromacil, diuron, and fluometuron no occurrence data are available for tebuthiuron or terbacd (295). Chloroxuron [1982-47-4] fenuronTCA [4482-55-7] andnorea [18530-56-8] also are urea herbicides. 

These high levels were sporadic and transitory. However, some of them were high enough to have caused phytotoxicity, and more work needs to be done to establish whether herbicides are having adverse effects upon populations of aquatic plants in areas highlighted in this study. It should also be borne in mind that there may have been additive or synergistic effects caused by the combinations of herbicides found in these samples. For example, urea herbicides such as diuron and chlortoluron act upon photosynthesis by a common mechanism, so it seems likely that any effects upon aquatic plants will be additive. Similarly, simazine and atrazine share a common mechanism of action. 

Miscellaneous urea herbicides (chlorobromuron (3,4(bromo-3-chlorophenyl)-1 -methoxy-1 -methylurea), Chlorotoluron (3(3 chlorotoluyl) dimethyl urea), Diuron (N-(3,4 chlorophenyl) N,N dimethyl urea), Monolinuron (3(4, chlorophenyl-1-methoxy-1 -methylurea), Linuron (3,(3,4 dichlorophenyl)-1 -1 -methoxy-1 -methylurea) Chloroxuron (3, (3,4 dichlorophenyl-1,1 dimethylurea)... 

More than 25 different substituted urea herbicides are currently commercially available [30, 173]. The most important are phenylureas and Cycluron, which has the aromatic nucleus replaced by a saturated hydrocarbon moiety. Benzthiazuron and Methabenzthiazuron are more recent selective herbiddes of the class, with the aromatic moiety replaced by a heterocyclic ring system. With the exception of Fenuron, substituted ureas (i.e., Diuron, Fluometuron, Fig. 10, Table 3) exhibit low water solubilities, which decrease with increasing molecular volume of the compound. The majority of the phenylureas have relatively low vapor pressures and are, therefore, not very volatile. These compounds show electron-donor properties and thus they are able to form charge transfer complexes by interaction with suitable electron acceptor molecules. Hydrolysis, acylation, and alkylation reactions are also possible with these compounds. 

SE Katz. Determination of the substituted urea herbicides linuron, monuron, diuron, neburon and fenuron in surface waters. J Assoc Off Anal Chem 49 452-456, 1966. 

Urea herbicides. Phenyl urea chemistry represents one of the earliest classes of herbicides. Replacement of the aromatic chlorines of diuron with a trifluoro-methyl group resulted in improved crop selectivity. Fluometuron (Cotoran ) and parafluron are both selective urea herbicides, fluometuron developed for the control of grass and broadleaf weeds in cotton. It was prepared from the corresponding 3-trifluoromethyl anilines. A number of other phenyl urea herbicides were introduced later, including trimefluor, 3-chloro-4-trifluoromethoxyphenyl-A/,A/-dimethyl urea [19]. 

TPNH) and oxygen to demethylate a number of closely related N,N-dimethylcarbamates (21). The same particulate system, however, exhibited a low order of activity on the urea herbicides monuron, diuron, and fenuron. Apparently, substitution of a nitrogen atom for the oxygen atom of the ester linkage to form the corresponding urea substantially decreased the velocity of the reaction. 

Kinoshita EK and DuBois KP (1970) Induction of hepatic microsomal enzymes by Herban, Diuron, and other substituted urea herbicides. Toxicology and Applied Pharmacology 17 406-417. 

High doses of borates persist for 2-5 years in the soil, depending on precipitation and the clay content of the soil. Owing to their good solubility in water, borates diffuse into the deeper layers of the soil and can kill deep-rooted weeds. Borates are combined with urea herbicides (e.g. diuron), 2,4-D, chlorates and uracyls. 

The two closely related urea herbicides take the form of stable crystalline compounds slightly soluble in water. Owing to their high chemical stability, their strong adsorption to the soil and their poor water solubility, they remain in the upper few centimeters of the soil and are very persistent. Diuron is the most persistent herbicide apart from simazine. 

The selectivity of these compounds can be attributed to several factors. Because of their acyl group, their mode of penetration into the plants differs substantially from that of the other urea herbicides. The acyl group is slowly split off in the soil, resulting in diuron and monuron, and they exert their action in these forms. Owing to their poor solubility in water and strong adsorption on the soil, they remain in the upper 10 cm of the soil, and are not toxic to deep-rooted crop plants. 

Field tests with monuron, linuron and with diuron (Belasco and Pease, 1969 Maier-Bode, 1971) unequivocally showed that under natural conditions no azo compounds are formed in the soil in analytically detectable quantities neither could they be detected by gas chromatography (detectability 0.01 ppm) in cultured crops grown on soils treated with urea herbicides. 

The different results of the photophosphorylation-inhibiting experiments performed by Bishop (1962) indicate a difference in the action mechanism of triazine herbicides and urea herbicides (Ashton and Crafts, 1973). According to Avron, diuron inhibits photophosphorylation catalysed both by FMN and by vitamin Kj, whereas Bishop demonstrate that simazine inhibits only photophosphorylation catalised by FMN. 

FIGURE 25.11 GC with a fused-silica capillary column and a NPD detector of some urea herbicides after conversion to their methylated forms. Symbol explanation A, monuron B, isoproturon C, chlorotoluron D, linuron E, diuron F, methabenzthiazuron G, tebuthiuron. (From Scott, S., Analyst, 118, 1117, 1993. With permission.)... 

Dichlorophenyl-dimethyl urea, DCMU, Diuron, 3-(3,4-dichlorophenyl)-l,l-dimethylurea, N -(3,4-dichlorophenyl)-N,N-dimethyluTaK a systemic herbicide which blocks electron transport from photosystem II to photosystem I (see Photosynthesis). It is absorbed principally by the roots then translocated ac-ropetally in the xylem. 

Synonyms AF 101 AI3-614378 Anduron Ansaron Bioron BRN 2215168 Caswell No. 410 CCRIS 1012 Cekiuron Crisuron Dailon DCMU DCMU 99 Dialer Dichlorfenidim 3-(3,4-Di-chlorophenol)-l,l-dimethylurea 3-(3,4-Dichlorophenyl)-l,l-dimethylurea A -(3,4-Dichloro-phenyl)-A,A-dimethylurea l,l-Dimethyl-3-(3,4-dichlorophenyl)urea Dion Direx 4L Diurex Diurol DMU DP hardener 95 Duran Durashield Dynex EINECS 206-354-4 EPA pesticide chemical code 035505 Farmco diuron Herbatox HW 920 Karmex Karmex diuron herbicide Karmex DW Krovar Lucenit Marmer NA 2767 NSC 8950 Seduron Sup r flo Telvar Telvar diuron weed killer UN 2767 Unidron Urox D USAF P-7 USAF XR-42 Vonduron. 

Chlorination of waters containing two phenylurea-type herbicides, isoproturon and diuron, results in the formation of THMs. The reaction of the phenylurea-type herbicide isoproturon with chlorine produced compounds that still contained the aromatic ring of the herbicide with the urea side-chain unmodified. The formation of chlorinated and brominated derivatives was related to the bromide concentration present in the water [113]. 

Triazine (e.g., atrazine, simazine) and substituted urea (e.g., diuron, monuron) herbicides bind to the plastoquinone (PQ)-binding site on the D1 protein in the PS II reaction center of the photosynthetic electron transport chain. This blocks the transfer of electrons from the electron donor, QA, to the mobile electron carrier, QB. The resultant inhibition of electron transport has two major consequences (i) a shortage of reduced nicotinamide adenine dinucleotide phosphate (NADP+), which is required for C02 fixation and (ii) the formation of oxygen radicals (H202, OH, etc.), which cause photooxidation of important molecules in the chloroplast (e.g., chlorophylls, unsaturated lipids, etc.). The latter is the major herbicidal consequence of the inhibition of photosynthetic electron transport. 

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