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Herbicide selectivity hydrolysis

Differences of 2,4-D (2,4-dichlorophenoxyacetic acid) conjugation in wheat (tolerant) versus some broadleaf weeds (susceptible) exemplifies how Phase II metabolism imparts herbicide selectivity. Many susceptible broadleaf weeds produce glucose ester metabolites, which are readily susceptible to hydrolysis, yielding phytotoxic 2,4-D. Conversely, 2,4-D-tolerant wheat rapidly produces amino acid conjugates and 0-glucosides, which are stable, nonphytotoxic metabolites that are not easily hydrolyzed 11,12),... [Pg.171]

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. [Pg.31]

The phenoxy herbicides inexpensiveness, selectivity, nonpersistency and low toxicity to animals are difficult to beat. Application is usually accomplished by spraying on the leaves. The herbicides cannot themselves be applied to the soil because they are washed away or decomposed by microorganisms in a few weeks. They can be applied by this method using a sulfonic acid derivative that, after hydrolysis in the soil and oxidation by bacteria, can form 2,4-D in the plant. 2,4-D is still the main herbicide used on wheat. [Pg.382]

Jenkins et al. produced a fiber optic based luminescence sensor designed to measure a hydrolysis product of the nerve agent soman (GD) in water. The sensor exhibited high selectivity, no interference from organophophorous (OP) herbicides or pesticides, and high sensitivity, with a limit of detection of 600 fg/mL in water (10). [Pg.79]

Stereoselective dehalogenation of 2-haloaIkanoic acids has been demonstrated for a number of halidohydrolases (80-82). Figure 77 details the production of an L-haloacid intermediate used in the production of phen-oxypropionic acid herbicides. The R enantiomer of chloropropionic acid is selectively hydrolyzed to (S)-lactic acid due to an inversion of configuration that occurs during the hydrolysis (83). (S)-2-chloroproprionic acid is used as a chiral synthon to produce a number of (R)-phenoxypropionic acid herbicides, for example, Fusilade 2000 (ICI). [Pg.232]

Owing to their different steric configuration, the absorption of acylureas by plants is different from that of the other urea herbicides, which may partly explain their different selectivity. Presumably, these compounds exert their action after hydrolysis of the acid group. [Pg.673]

Many compounds of this class hydrolyze to produce chloroanilines, which can cause anemia and methemoglobinemia. Such hydrolysis may occur both under acidic and alkaline conditions, and the degree of hydrolysis depends on the water solubility. Although these substances may form nitrosamines under certain conditions, there is no report of carcinogenicity. Chemical structures, physical properties, and toxicity data for a few selected herbicides of this class are presented in the following sections. [Pg.817]

Table IV. Ionization and Hydrolysis of Selected Sulfonylurea Herbicides ... Table IV. Ionization and Hydrolysis of Selected Sulfonylurea Herbicides ...
Primisulfuron-methyl is a selective herbicide for the control of grasses in maize. Comparison [81] with its unfluorinated triazine counterpart methsulfuron-methyl indicates that crop safety for maize is achieved by the replacanent of the triazine methoxy and methyl substituents with two difluoromethoxy groups. It has been shown that primisulfuron-methyl is deactivated in maize by hydroxylation of the phenyl and pyrimidyl moieties followed by hydrolysis or conjugation [82]. [Pg.577]


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