Herbicides fenuron

Of all the urea derivatives the herbicide fenuron (5) has the highest solubility in water and is the least adsorbed by the soil. Owing to its good water solubility, it is easily washed into the deeper layers of the soil. Absorbed through the roots it kills deep-rooted grass and broad-leaved weeds. It is also effective for the control of... 

Phenoxy acids (2,4-dichlorophenoxy acetic acid, MCPA, and 2,4,5-trichlorophenoxy acetic acid) and similar acid herbicides (benzaton, dicamba, dichlorprop, and mecoprop) sulfonurea herbicides (chlorsulforon, metsulforon methyl, tribenuron methyl, and thifensulfuron methyl) triazine herbicides (methoxy-s-triazines, chloro-s-triazines, alkylthio-s-triazines) phenylurea herbicides (fenuron, monolinuron, and diuron), metabolites of the fungicide thiophanate-methyl (carbenazim and 2-aminobenzimidazole)... 

Fig. 9.9 which was obtained using a Perkin Elmer 452 gas chromatograph shows the separation of 0.5ng amounts of four derivatised herbicides A, monoLinuron B, Fenuron C, Linuron and D, chlorobromuron. 

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. 

Figure I. Chemical structure of 3-phenyl-l, 1-dimeihylurea (fenuron) —a typical phenylurea herbicide...

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. 

Bucha and Todd described the herbicidal properties of neburon (27) together with those of monuron, fenuron and diuron as early as 1951, but neburon, introduced only in 1955, did not gain widespread use. 

FIGURE 25.9 Capillary GC with fused-silica column coated with CP-Sil 5 (analogous to SB 30 and OV-101) of HFB derivatives of 13 phenylureas obtained after extraction of a Bosbaan river water sample spiked at 1 fjig/ level, and direct derivatization with HFB A. Injected amount corresponds to 0.1 ng of each herbicide. Symbol explanation Fm, fluometuron Fe, fenuron Mo, monuron Ml, monolinuron Ip, isoproturon Ct, chlorotoluron Mb, metobromuron Bu, buturon Di, diuron Li, linuron Cb, chlorbromuron Mx, metoxuron Nb, neburon. (From Brinkman, U. A. Th., de Kok, A., and Geerdink, R. E., J. Chromatogr., 283, 113, 1984. With permisssion.)... 

The arylurea hetbicides wete also used for MIPs synthesis. Two arylureas, fenuron and isoproturon, wete polymerized svith MAA as functional monomet and used as adsorbents for solid phase extraction of pollutants. The isoprotuton-imprinted polymer did not demonstrate the selectivity towards the template but had a high affinity towards all other arylurea herbicides. The corresponding blanks (nonimprinted polymers) did not retain any of these compounds, which suggest that the imptinting was achieved. With fenuron, very good specificity for this herbicide was observed. This result can be explained by the small size of the fenuron molecule. Indeed the other arylureas were not able to enter in the small cavities formed around fenuron due to steric interactions of the meta- or para-substituents in the aromatic ring. ... 

Fenuron was mobile in soil systems compared with other phenylurea herbicides (87, 356), Movement was related to the water solubilities of the compounds (87). Fenuron s leachability was also greater in coarse textured soils than in fine textured ones and was related to the organic matter content of the soil. In a recent field experiment fenuron moved substantially in a lateral direction over the soil surface and in a vertical direction into the subsoil (63). Femuron moved into the subsoil much more on coarse textured soils than on fine textured ones, but it moved only when excessive amounts (80-160 pounds per acre) were used (356). 

Herbicidal activity of the phenylureas in soils decreased as the organic matter content of the soils increased 165, 347, 350, 372, 373, 374, 375, 376), Studies showed that adding organic matter to sandy soil greatly reduced the herbicidal activity of fluometuron and fenuron in growth chamber studies with model soil systems (63) and in field experiments on modified soils (121),... 

Other investigators found no relationship between phenylurea adsorption or herbicidal activity and the clay contents of soils (373, 375, 376, 377). In small-pot experiments in growth chambers, the author (63) found that montmorillonite clay added to model soil systems significantly reduced the phytotoxicity of fiuometuron and fenuron but that kaolinite... 

The herbicidal effect of aryl- and hetarylurea, systematically studied starting from first observations in 1946, was improved between 1951 [30] and 1973 [31]. From this chemistry today the compounds chloroxuron (Ciba, 1960), dimefuron (Hoechst, 1969), diuron (Du Pont, 1954), ethidimuron (Bayer, 1973), fenuron (Du Pont, 1957), fluometuron (Ciba, 1960), isoproturon (Hoechst, 1974), linuron (Hoechst, 1960), methabenzthiazuron (Bayer, 1968), metobromuron (Ciba, 1963), metoxuron (Sandoz, 1968), monolinuron (Hoechst, 1958), neburon (Du Pont, 1957), siduron (Du Pont, 1964) and tebuthiuron (Elanco, 1973) are still used. 

Herbicides used were fenuron (a) monuron (b) diiu-on(c) linuron (d) tebuthiuron (e) ethidimu-ron (f) atrazine (g) amet-ryne (h) propazine (i) prometryne (j) terbutryne (k) metribuzine (1) meta-mitron (m) bromacyl (n) cyanoacrylate-s (o) cyano-acrylate-r (p) bromoxynil (q) ioxynil (r) dinoseb (s) phenmedipham (t) fluo-meturon (u) simazine (v)... 

---