Urea herbicides linuron

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. 

Huber, G., Gemes, E. (1981) Decomposition of urea herbicide linuron (3-(3,4-dichlorophenyl)-l-methoxy-l-methylurea) in water of Lake Balaton. Hungar. J. Ind. Chem. 9, 113. 

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)... 

You are concerned about the longevity of the herbicide, linuron, leaching into a river from some neighboring farmland. Given the structure of this urea derivative, you expect it will be biodegraded via a hydrolysis mechanism. You recall a report of a hydrolase enzyme from a common bacterium that exhibits a half-saturation constant, KMM, for linuron of 2 /tM and a maximum degradation rate, Vmax, for linuron of 2500 /nmol kg-1 protein s l. 

Fig. 4.69. Reaction scheme for the formation of DNS derivatives of carbamate and urea herbicides (example, Linuron). 1 = Hydrolysis 2 dansylation of the aniline moiety.

Masabni et al (1996) identified a Ser264 to Thr (threonine) mutation in a resistant biotype of common purslane. This conferred a high level of resistance to atrazine and also to linuron, a substituted urea herbicide. This was the first report of a Ser264 to Thr substitution in higher plants selected under field conditions. Previously, this mutation had only been selected through tissue culture in tobacco and potato (Sigematsu et al, 1989 Smeda etal, 1993). 

Dansylation has also been used to detect N-phenyl-carbamate and urea herbicides by adding excess reagent on the applied spot directly on the tic (3 2. This in situ reaction proved to be cleaner and more practical than labelling in solution and was applied to the detection of Linuron (33) in agricultural crops at the 0.05 ppm level. Other applications involving hydrolysis and dansylation in solution prior to tic have been reported with organophosphorus insecticides... 

Thus, the reaction has some value for the synthesis of known ureas derived from methoxymethyl amine such as the herbicide Linuron [see scheme 141] (Ref. 196). 

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 photolytic degradation of urea herbicides also proceeds in several steps. In addition to hydrolysis reactions, degradation products hydroxylated in the ring are formed in photonucleophilic reactions. In the case of monuron and linuron, hydrolysis is even preceded by the exchange of the chlorine at< ms of the ring for hydroxyl groups (Rosen et al., 1969 Crosby and Tang, 1969). 

Linuron Methoxydiuron Arresin Afalon. A residual urea herbicide for the control of weeds in field crops including potatoes and carrots. Crystals mp = 93-94° soluble in H2O, acetone, alcohol, benzene, toluene, xylene LDso (rat orl) = 1500 mg/kg. Agan Chemical Manufacturers Ashlade Formulations Ltd. Adas Interlates Ltd DuPont UK Farm Protection Ltd. Hoechst UK Ltd. ICI Chem. Polymers Ltd. MTM AgroChemicals Ltd. 

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.)... 

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. 

Chloroalkyl carbamates, prepared with phosgene (see Section 4.3.2 Carbamates ), react with hard nucleophiles such as methoxymethyl amine to afford known ureas such as the herbicide Linuron [219]. 

The first generation of urea herbicides is represented by types such as monuron and linuron (see Table 29.12). These compounds in general interfere with the photosynthetic process, as they inhibit electron transport in the photosystem II process of the plant. They have varying degrees of selectivity, depending upon the structure. Some owe their selectivity to physical properties such as water solubility and soil absorption. If the crop is a deep-rooted perennial, the shallow rooted annual weeds are controlled by using a herbicide that is not easily leached down into the root zone... 

Urea and uracil herbicides tend to be persistent in soils and may carry over from one season to the next (299). However, there is significant variation between compounds. Bromacil is debrominated under anaerobic conditions but does not undergo further transformation (423), linuron is degraded in a field soil and does not accumulate or cause carryover problems (424), and terbacd [5902-51-2] is slowly degraded in a Russian soil by microbial means (425). The half-hves for this breakdown range from 76 to 2,475 days and are affected by several factors including moisture and temperature. Finally, tebuthiuron apphed to rangeland has been shown to be phytotoxic after 615 days, and the estimated time for total dissipation of the herbicide is from 2.9 to 7.2 years (426). 

Cotterill [100] studied the effect of ammonium nitrate fertilizer on the electron capture or nitrogen specific gas chromatographic determination of Triazine plus other types of herbicide (Atrazine(2-chloro-4-ethylamino-6-isopropylamino, 1,3,5 triazine), Simazine (2-chloro-4.6 bis ethyl amino 1,3,5 triazine), Linuron (3,4,-chlorophenyl-l-methoxy-l-methyl urea), Metribuzin, Triallate and Phorate) residues in soil. 

The presence of free anilines or other metabolites in soils and plants has been reported [123, 139-143]. Some work has suggested that they are very strongly bound to soil components and the findings of Caverly and Denney [138] are in agreement with these conclusions. The presence in soils of metabolites of Linuron that possess the urea structure have been reported [123, 142] these are produced mainly by microbiological degradation. The dimethyl derivative is considered to be inactive whereas the monomethyl metabolite has phytotoxicity approaching that of the parent herbicide [142], It is probable that the procedure reported by... 

Linuron, a substituted urea introduced by Hoechst in 1960, is employed primarily as a preemergence herbicide but it also has contact effect on foliage (Fig. 3). Linuron is used principally in soybeans, corn, sorghum, wheat, and potatoes. It is often mixed with other herbicides to broaden the weed spectrum. 

Substituted ureas, e.g. linuron and chlorbrpxp-uron Triazine herbicides, e.g. simazine Uracilherbicides, e.g. bromacil ... 

Linuron, a urea derivative herbicide and androgen receptor antagonist, and butyl benyl phthalate, a plasticizer, are two compounds with very different chemical properties, yet in a laboratory animal study, prenatal exposure to a mixture of these produced dose-additive testosterone and other adverse developmental effects. I66 ... 

There are a number of organic acids that interfere with plant metabolism. Dicamba (3,6-dichloro-2-methoxybenzoic acid) and tricamba are herbicides which interfere with protein synthesis, while picloram (4-amino-3,5,6-trichloro-2-pyriidinecarboxylic acid) interacts with nucleic acid synthesis in susceptible plants. Dicamba is primarily eliminated in the urine due to its hydrophilic properties. Some benzonitrile derivatives are also employed as herbicides, including dichlobenil (2,6-dichlorobenzonitrile), bromoxynil (3,5-dibromo-4-hydroxybenzonitrile), and ioxynil. Linuron (N -(3,4-dichlorophenyl)-N-methoxy-N-methylurea) is a phenyl urea while trifluralin (a,a,a-trifhiro-2,6-dinitro-N,N-dipropyl-p-toluidine) is a dinitroaniline. The major concern with the substituted ureas is induction of hepatic microsomal enzymes which could modulate the disposition of simultaneously exposed chemicals metabolized by the same enzymes. Finally, one of the most common herbicides presently in use is glyphosphate, or Roundup , a phospho-... 

Using this biosensor, it was possible to detect herbicides of the urea, nitrile, and triazine families (eg, linurone, ioxynil, atrazine) with different sensitivities (125-350 ug/1). The sensitivity improved by 20-50 pg/l after fresh microbial cells were placed into the device. 

Furthermore, urea-type pesticides propanil, linuron, and diuron, which arc the main herbicides used throughout the world, have the ability to bind to AR (Cook et ai, 1993 Bauer et al., 1998). Indeed, linuron is strueturally related to the nonsteroidal antiandrogen flutamidc, and its IC50 for competition at the AR is approximately 3.5 limes that of flutamide. The activity of its metabolite, 3,4-dichloroanilinc, is higher than that of linuron. 

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